API571-Part3

4.2 Mechanical & Metallurgical Failure Mechanisms 机械和冶金失效机制

4.2 4.2 Mechanic Mechanica al and Metallur tall urgi gical cal Fail Failur ure e Me Mechanis ch anisms ms 4.2.1 Graphitization. 4.2.2 Softening (Spheroidization). 4.2.3 Temper Embrittlement. 4.2.4 Strain Aging. 4.2.5 885°F (475°C) Embrittlement. 4.2.6 Sigma Phase Embrittlement . 4.2.7 Brittle Fracture. 4.2.8 Creep and Stress Rupture. 4.2.9 Thermal Fatigue . 4.2.10 4.2.10 Short Term Term Overheatin Overheating g – Stress Stress Rupture. Rupture. 4.2.11 Steam Blanketing. 4.2.12 Dissimilar Metal Weld (DMW) Cracking. 4.2.13 Thermal Shock. 4.2.14 4.2.14 Erosion/ Erosion/Erosi Erosion on – Corrosion. Corrosion. 4.2.15 Cavitation. 4.2.16 Mechanical Fatigue. 4.2.17 Vibration-Induced Fatigue. 4.2.18 Refractory Degradation. 4.2.19 Reheat Cracking.

2013 2013-- API57 API570 0 Ex Ex amin ami n atio ati o n

2013 2013-API -API51 510 0 Examin Exami n atio ati o n

Par. Par. 3 – Definit Definitions ions

Par. 3. - Definit Definitions ions

4.2.7 – Britt Brittle le Fract Fracture ure

4.2.3 – Tempe Temperr Embrittl Embrittlement ement

4.2.9 4.2 .9 – The Therma rmall Fatigue Fatigue

4.2.7 – Britt Brittle le Fract Fracture ure

4.2.14 – Erosion Erosion/Erosi /Erosion on Corrosion Corrosion

4.2.9 4.2 .9 – The Therma rmall Fatigue Fatigue

4.2.16 – Mechani Mechanical cal Fatigu Fatigue e

4.2.14 – Erosio Erosion/Eros n/Erosion-Cor ion-Corrosion rosion

4.2.17 – Vibrat Vibration-Ind ion-Induced uced Fatigue Fatigue

4.2.16 – Mechan Mechanical ical Failure

4.3.1 – Galvanic Galvanic Corrosion Corrosion

4.3.2 – Atmospheric Atmospheric Corrosion Corrosion

4.3.2 – Atmospheric Atmospheric Corrosion Corrosion

4.3.3 – Corrosion Corrosion Under Insulati Insulation on (CUI)

4.3.3 – Corrosion Corrosion Under Insulation Insulation (CUI) (CUI)

4.3.4 – Cooling Water Corrosion Corrosion

4.3.5 – Boiler Water Water Condensat Condensate e Corrosion Corrosion

4.3.5 – Boiler Water Water Condensate Condensate Corrosi Corrosion on

4.3.7 – Flue Gas Gas Dew Point Point Corrosion Corrosion

4.3.10 – Caustic Caustic Corrosion Corrosion

4.3.8 – Microbiologica Microbiologicall Induced Corrosion Corrosion (MIC) (MIC)

4.4.2 4.4.2 – Sulfidat Sulfidation ion

4.3.9 4.3.9 – Soil Soil Corrosio Corrosion n

4.5.1 – Chloride Chloride Stress Corrosion Corrosion Cracking Cracking (Cl-SCC) (Cl-SCC)

4.4.2 4.4.2 – Sulfid Sulfidati ation on

4.5.2 4.5.2 – Corros Corrosion ion Fatigue Fatigue

4.5.1 – Chloride Chloride Stress Corrosion Corrosion Cracking Cracking (Cl-SCC) (Cl-SCC)

4.5.3 – Caustic Caustic Stress Stress Corrosion Corrosion Cracking Cracking

4.5.3 – Caustic Caustic Stress corrosion corrosion Cracking Cracking

5.1.2.3 5.1.2.3 – Wet H2S Damage (Blister/ (Blister/HIC/SO HIC/SOHIC/SCC HIC/SCC))

5.1.3.1 5.1.3.1 – High Temperature Temperature Hydrogen Hydrogen Attack Attack (HTTA)

5.1.3.1 5.1.3.1 – High Temperatur Temperature e Hydrogen Attack Attack (HTHA) (HTHA)

Exam

510

Damage Mechanism

Temperatures

Affected materials

Graphitisation

800° 800°F~1100° F~1100°F for C Steel

Plain carbon steel

875° 875°F for for C ½ Mo Ste Steel el

C, C ½ Mo

Spheroidisation

850 °F ~ 1400 °F

Low alloy steel up to 9% Cr

Tempered

650 °F~ 1070 °F

2 ¼ Cr-1Mo Cr-1Mo low alloy steel, steel, 3Cr3Cr-

Embrittlement

1Mo (lesser extent), & HSLA CrMo-V rotor steels

Strain Aging

Intermediate temperature

Pre-1980’s C-steels with a large grai grain n siz size e and and C- ½ Mo

885°F embrittlement

600 °F~ 1000 °F

300, 400 & Duplex SS containing ferrite phases

Sigma-Phase Embrittlement

1000 °F~ 1700 °F

Ferritic, austenitic & duplex SS. Sigma forms most rapidly from the ferrite phase that exists in 300 Series SS and duplex SS weld deposits. It can also form in the 300 Series SS base metal (austenite phase) but usually more slowly.

Exam

Damage Mechanism

Temperatures

Affected materials

510/570

Brittle Fracture

Below DTBTT

C, CC- ½ Mo, 40 400 SS

510/570

Creep & stress rupture 700 °F ~ 1000 °F

All metals and alloys

Thermal fatigues

Operating temperature

All materials of construction construction

Short Term

>1000 °F

All fired heater tube materials

Overhe Overheati ating ng – Stress Stress

and common materials of

Rupture

construction

Steam Blanketing

>1000 °F

Carbon steel and low alloy steels

Dissimilar Metal Weld

Operating temperature

(DMW) Cracking Thermal Shock

Carbon steel / 300 SS junction

Cold liquid impinge on hot surface

All metals and alloys. alloys.

Exam

Damage Mechanism

Temperatures

Affected materials

570/510

Erosion/Erosion

Service temperature

All

Corrosion 570/510

Mechanical fatigue

Service temperature

All

570

Vibration-Induced

Service temperature

All

Fatigue

4.2.1 Gr ap h i t i zat i o n 石墨化 (不是 API510/570 API510/570考试项考试项))

Prolong Exposure 800°F ~ 1100°F for C Steel >875°F for for C ½ Mo Stee Steell

4.2. 4.2.1 1 Graphiti Graphi tiza zati tion on 石墨化 4.2.1.1 Description of Damage

a) Graphitiza Graphitization tion is a change change in the the microstru microstructure cture of of certain certain carbon carbon steels steels and 0.5Mo steels after long-term operation in the 800° 800 °F to 1100° 1100°F (427° (427°C to 593° 593°C) range that may cause cause a loss in strength, strength, ductility, ductility, and/or and/or creep resistance.在 resistance.在800° 800°F 1100° 1100°F长期运行后 b) At elevated elevated temperatu temperatures, res, the carbide carbide phase phases s in these these steel steels s are are unstable unstable and may decompose into graphite nodules. This decomposition is known as graphitization.碳钢 graphitization.碳钢/C - ½ Mo钢, 在长期受到高温度影响，钢中碳化物相变得不稳定, 从而分解成石墨结节 4.2.1.2 Affected Materials Some grades of carbon steel and 0.5Mo steels. (普通碳钢 ( 普通碳钢/0.5 /0.5钼钢钼钢))

碳钢/ 碳钢/C - ½ Mo钢, 在长期受到高温度影响，钢中碳化物相变得不稳定,, 从而分解成石墨结节中碳化物相变得不稳定

Graphitization Location: Areas with tubes tubes containing carbon steel and and C-Mo. Most Most likely in the the weld heat-affected zones and high residual stress areas. 易受影响区: 易受影响区: 碳钢或 C- ½ Mo 普通碳钢, 普通碳钢, 焊接热影响区和高残余应力区

Pro robabl bable e caus cause: e: Prolonged exposure to above 800° 800 °F (425° (425°C) for carbon carbon steels steels and greate greaterr than than 875°°F (470° 875 (470°C) for the car carbon bon-- ½ mo molyb lybden denum um all alloys oys.. In In grap graphit hitize ized d boil boiler er components, component s, the nucleation of graphite likely starts by the precipitation of “carbon” from super-saturated super-saturated ferrite, an an aging phenomenon. phenomenon. This nucleation is enhanced by strain, in effect a strain aging. The preferential formation of graphite within the heat-affected zone is dependent on the balance of the structure being being nearly strain strain free. Thus Thus the “more unstable” heat-affec heat-affected ted zone microstructure will decompose into ferrite and graphite before the annealed ferrite and pearlite of the normalized structure will. If the base metal is coldworked, the annealing of the weld will slow the nucleation of graphite, and the strained tube will graphitize before the heat-affected zone.

在长时间的高温影响下,蝶状珠光体(碳化铁)首先转化为粒状珠光体,然后碳从超饱和的碳化铁析出,晶核形成石墨与周边缺碳纯铁素体.

4.2. 4.2.1. 1.3 3 Critic Crit ical al Factors Facto rs

a) The most most important important factor factors s that affect affect graphitiz graphitizatio ation n are the chemistry chemistry,, stress, temperature, and time of exposure. b) In general, general, graphitiza graphitization tion is not not commonly commonly observed. observed. Some steels steels are much more susceptible susceptible to graphitization than others, others, but exactly what what causes some steels steels to graphitize graphitize while others are resistant is not well understood. It was originally thought that silicon and aluminum content played a major role but it has been shown that they have negligible influence on graphitization. c) Graphitiza Graphitization tion has has been been found found in low alloy alloy C-Mo C-Mo steels steels with with up to 1% Mo. The addition of about 0.7% chromium has been found to eliminate graphitization. d) Temperatu Temperature re has an importa important nt effect effect on the the rate of graphit graphitizat ization. ion. Below Below 800° 800°F (427° (427°C), the rate rate is extremely extremely slow. slow. The rate increase increases s with increasing temperature.

e) There are two general types of graphitization. First is random random graphitization graphitization in which the graphite nodules are distributed randomly throughout the steel. While this type of graphitization may lower the room-temperature room-temperature tensile strength, it does not usually lower the creep resistance.

f) The seco second nd and and more more damag damaging ing type type of of graphi graphitiz tizat ation ion resu results lts in in chains or local l ocal planes planes of conce conc entrated ntrated gra g raphit phite e nodules. •

Weld Weld heat heat-af -affec fecte ted d zone zone grap graphit hitiza izatio tion n is most most freq frequen uently tly found found in the heat-affected heat-affected zone adjacent to to welds in a narrow band, band, is called “eyebr “eyebrow, ow,”” graphi graphitiz tizat ation ion..

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Non-we Non-weld ld graphi graphitiz tizati ation on is a form form of localiz localized ed graphi graphitiz tizati ation on that that sometimes occurs along along planes of localized yielding in steel. steel. It also occurs in a chain-like manner in regions that have experienced significant plastic deformation deformation as a result of cold col d working operations or bending.

Weld heat heat affected zon zone e gra gr aphit ph itiza izati tion on

is most frequently found in the heat-affected zone adjacent to welds in a narrow band, corresponding to the low temperature edge of the heat affected zone. In multi-pass welded butt joints, these zones overlap each other, covering the entire cross-section. Graphite nodules can form at the low temperature edge of these heat affected zones, resulting in a band of weak graphite extending across the section. Because of its appearance, this graphite formation within heat heat affected affected zones zones is called “eyebrow” “eyebrow” graphitization.

Type 2: HAZ graphite nodules

eyebrow! Type2 Graphitization 焊缝热影响区石墨化现象

eyebrow! Graphitization

eyebrow! Type 2 Graphitization 焊缝热影响区现象

太厉害了别人的肖像变成他家的版权了 ..NMD

Non-weld graphiti graphi tiz zation tio n is a form of localized graphitization that sometimes occurs along planes of localized yielding in steel. It also occurs in a chain-like manner in regions that have experienced significant plastic deformation as a result of cold working operations or bending. 显著地塑性变形区域, 显著地塑性变形区域, 石墨化可能以链状方式形成.

Type 2: Non Weld Chains or local planes of concentrated graphite nodules

4.2.1. 2.1.4 4 Affected Aff ected Units Unit s or o r Equip Equ ipment ment

a) Primarily Primarily hot-wall hot-wall piping piping and and equipment equipment in in the FCC, FCC, catalyt catalytic ic reformin reforming g and coker units. b) Bainitic Bainitic grades grades are are less susceptib susceptible le than than coarse coarse pearlit pearlitic ic grades. grades. c) Few failure failures s directly directly attribu attributabl table e to graphitiz graphitizatio ation n have been been reporte reported d in the refining industry. However, graphitization has been found where failure resulted primarily from other causes. d) Several Several serious serious cases cases of graphitiz graphitization ation have have occurred occurred in the the reactors reactors and and piping of fluid catalytic catalytic cracking units, as well as with carbon steel furnace furnace tubes in a thermal cracking unit and the failure of seal welds at the bottom tube sheet of a vertical waste heat boiler in a fluid catalytic cracker. A graphitization failure was reported in the the long seam seam weld of a C 0.5Mo catalytic reformer reactor/inter-heater line.

e) Where Where concentrat concentrated ed eyebrow eyebrow graphitiza graphitization tion occurs occurs along along heat-aff heat-affecte ected d zones, the creep rupture strength may be drastically lowered. Slight to moderate amounts of graphite along the heat-affected zones do not appear to significantly lower room or high-temperature high-temperature properties. f) Graphi Graphitiz tizati ation on seldo seldom m occurs occurs on on boilin boiling g surface surface tubi tubing ng but but did occu occurr in low alloy C-0.5Mo tubes and headers during the 1940’s. Economizer tubing, steam piping and other equipment that operates in the range of temperatures of 850° 850°F to 1025° 1025°F (441° (441°C to 552° 552°C) is more more like likely ly to suff suffer er graphitization.

4.2.1. 2.1.5 5 Appe App earanc arance e or Morph or phol olog ogy y of Damage Damage

1. Damage Damage due to to graphitiza graphitization tion is is not visible visible or readily readily appare apparent nt and can can only be observed by metallographic examination (Figure 4-1 and Figure 4-2). 2. Advanc Advanced ed stage stages s of dam damage age rela related ted to loss loss in cree creep p stren strength gth may may inclu include de micro-fissuring / microvoid formation, subsurface cracking or surface connected cracking.

0.5μm

Figure 4-1 – High magnification magnification photomicrogr photomicrograph aph of metallographic metallographic sample showing graphite nodules. Compare to normal microstructure shown in Figure 4-2.

Figure 4-2 – High magnification magnification photomicro photomicrograph graph of metallographic metallographic sample showing typical ferrite-pearlite structure of carbon steel.

4.2.1.6 Prevention / Mitigation 预防/ 预防/缓解 Graphitization can be prevented by by using chromium chromium containing containing low alloy steels for long-term operation above 800° 800°F (427° (427°C).

The addition of about 0.7% chromium has been found to eliminate graphitization.

0.7% chromium

以消除石墨化.

4.2.1.7 Inspection and Monitoring a) Evidence Evidence of graphitiza graphitization tion is most effectiv effectively ely evaluated evaluated through through removal removal of full thickness samples for examination using metallographic techniques. Damage may occur mid-wall so that field replicas may be inadequate. b) Advanced Advanced stage stages s of damage damage relat related ed to loss loss in strengt strength h include include surface surface breaking cracks or creep deformation that may be difficult to detect. 4.2.1.8 Related Mechanisms Spheroidization (see 4.2.2) and graphitization are competing mechanisms that occur at overlapping temperature ranges. Spheroidization tends to occur preferentially above 1025° 1025°F (551° (551°C), while graphitization predominates below this temperature.

Spheroidization (see 4.2.2) and graphitization are competing mechanisms that occur at overlapping temperature ranges. Spheroidization tends to occur preferentially above 1025 F (551 (551°°C), while graphitization predominates below this temperature. Graphitization can be prevented by by using chromium chromium containing containing low alloy steels for long-term operation above 800° 800°F (427° (427°C). Affected Materials: Some Some grades of carbon steel and 0.5Mo 0.5Mo steels. steels. Graphitization has been found in low alloy C-Mo steels with up to 1% Mo. The addition of about 0.7% chromium has been found to eliminate graphitization.

Creep Type: Microvoid formation & jointing of ligament between voids

Typical ferrite-pearlite structure of carbon steel.

Typical ferrite-pearlite structure of carbon steel.

Typical martensitic structure of carbon steel.

Figure 13: Lower bainite generated by isothermal transformation transformation of 52100 steel at 230C for 10h http://www.msm.cam.ac.uk/phase-trans/2 http://www.msm.cam.ac.u k/phase-trans/2011/Bearing 011/Bearings/index.htm s/index.htm l

Random graphitization

Random graphitization

Chain graphitization http://davidnfrench.com/Graphitization.html

Graphitization of A Cast Iron Main

>800° >800 °F

石墨化, 石墨化,学习重点: 学习重点: 1. 高温现象 1. 高温现象:: 800° 800°F to 1100° 1100°F 2. 受影响材料 2. 受影响材料:: 碳钢( 碳钢(不包括低合金钢) 不包括低合金钢), ½ Mo钢 3. 损伤模式 3. 损伤模式:: (1) 无规则石墨化(仅仅影响室温抗拉)与 (2) HAZ/平面石墨化 (较为严厉,影响室温抗拉高温蠕变性能) 4. 注意项 4. 注意项:: ½ Mo钢,抗拒性较强, 875°F高于碳钢 800° 800°F 抗拒性较强,敏感温度为 875° 5. 添加 5. 添加 0.7%Cr 有效阻止石墨化. 有效阻止石墨化. 6. 不是 6. 510/570考试学习项.. 不是 API 510/570考试学习项

http://www.chasealloys.co.uk/steel/all http://www.chasea lloys.co.uk/steel/alloying-ele oying-elements-in-ste ments-in-steel/#chromiu el/#chromium m

4.2.2 Carbide Spheroidization 碳化物球化 (不是 API510/570 API510/570考试项考试项))

Spheroidization Prolong Exposure 850°F ~ 1400°F

4.2.2 2.2 Sof Softeni tening ng (Spheroidi Spheroi diza zati tion on)) 碳化物球化

4.2.2.1 Description of Damage Spheroidization is a change in the microstructure of steels after exposure in the 850° 850°F to 1400° 1400°F (440° (440°C to 760° 760°C) range, where the carbide carbid e phases phases 碳化物 in carbon steels steels are unstable unstable and may agglomerate agglomerate from their normal plate-like plate-like form to a spheroidal form, or from small, finely dispersed carbides in low alloy steels like 1Cr-0.5Mo to large agglomerated carbides. Spheroidization may cause a loss in strength and/or creep resistance. 4.2.2.2 Affected Materials All commonly used grades of carbon steel and and low alloy steels including C0.5Mo, 1Cr-0.5Mo,1.25Cr-0.5Mo, 2.25Cr-1Mo, 3Cr -1Mo, 5Cr-0.5Mo, and 9Cr1Mo steels. 高温现象: 高温现象: 在长期高温下, 在长期高温下,细分散或板状碳化物形成球状形式细分散或板状碳化物形成球状形式.. 涵盖了普通碳钢, 涵盖了普通碳钢, 0.5Mo钢 0.5Mo钢, 低合金钢, 低合金钢,

Figure 9: The microstructures near the OD surfac surfacee were were most mostly ly decar decarbur burize ized. d. The remaining carbides were highly spheroidized and agglomerated along the ferrite grain boundaries. The microstructure 90° from the rupture and at the tube end is shown.(Nit shown.(Nital al etch, Mag. 500X) 500X)

Figure 10: The microstructures near the ID surface consisted of partially and highly spheroidized and agglomerated carbides along along the the ferr ferrite ite grai grain n bound boundari aries. es. The microstructure 90 ° from the rupture and at the tube end is shown. (Nital etch, Mag. 500X)

http://www.met-tech.com/short-term-overheat-rupture-of-t11-superheater-tube.html

Differences 

Softening (Spheroidization), at prolong exposure to high temperature carbide phases in carbon steels are unstable and may agglomerate from their their normal plate-like plate-like form to to a spheroidal spheroidal form, or or from small, small, finely dispersed carbides in low alloy all oy steels like 1Cr-0.5Mo to large agglomerated carbides. 在长期高温工作下, 在长期高温工作下,低合金碳钢, 低合金碳钢,碳化物相变得不稳定, 不稳定, 导致正常板状形式凝聚成一个球状形式导致正常板状形式凝聚成一个球状形式..



Graphitisation, the carbide phases phases in carbon/Molydenum carbon/Molydenum steels are unstable and may decompose into graphite nodules.在高温长期工作 nodules. 在高温长期工作下,普通碳钢/0.5 普通碳钢/0.5钼钢中的化物相变得不稳定钼钢中的化物相变得不稳定,,这碳化物分解成石墨结节这碳化物分解成石墨结节.. 影响的材料差别为; 影响的材料差别为; (1) 普通碳钢/ 普通碳钢/受石墨化影响 (2) 低合金含铬钼高强度, 低合金含铬钼高强度,高温钢受碳化物球化

Spheroidization in physical metallurgy, a process consisting in the transition of excess-phase crystals into a globular (spheroidal) form. The transition occurs at relatively high temperatures and is associated with a decrease in the interfacial energy 高温下界面的能量减少.. Of particular 高温下界面的能量减少 importance is the spheroidization of the cementite plates contained in pearlite. In this process, the lamellar pearlite is converted into granular pearlite片状珠光体转变为粒状珠光 pearlite片状珠光体转变为粒状珠光体. As a result, the hardness and the strength of the metal are significantly decreased, but the ductility is increased.

Carbide Spheroidization 碳化物球化

Figure Figu re 1. Corroded sheath exterior (0.85X Original Magnification)

Figure 2. Etched sample of a section of non-corroded material (200X Original Magnification with Nital Etch)

http://www.matter.org.uk/steelmatter/formin http://www.matter.org.u k/steelmatter/forming/4_5.html g/4_5.html

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Graphitisation and spheroidization both were high temperature phenomenon.石墨化与球化都 phenomenon.石墨化与球化都是材料高温效应

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Graphitisation affect affect normal carbon steel. It is a break down of carbides into ferrite and free graphite (carbon) nodules.石墨化是高温下 nodules.石墨化是高温下,,碳化物分解为铁素体和游离石墨/碳.

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Spheroidization affect Cr-Mo low carbon steel up to 9%Cr. It is a agglomeration of carbides forming spheroidal carbides. 球化是高温下,界面的能量减少导致片状珠光体转变为粒状珠光体

Spheroidization affect Cr-Mo low carbon steel up to 9% Cr. It is a agglomeration of carbides forming spheroidal carbides 影响达 9%Cr 低合金碳钢, 碳钢,高温下界面的能量减少高温下界面的能量减少,,片状珠光体转变为粒状珠光体 (片状碳化物集聚形成球状碳化物). 形成球状碳化物).

9% Chromium

含

碳化物球化影响范围.

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Residual stress & cold works accelerated graphitization.残余应 graphitization.残余应力和冷工程加速石墨化.. 力和冷工程加速石墨化

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For spheroidisation coarse-grained steels are more resistant than fine-grained. fine-grained. Fine grained silicon-killed steels are more resistant than aluminum killed. 

粗粒度的钢比细粒度更抗拒碳化物球化.. 粗粒度的钢比细粒度更抗拒碳化物球化



细晶硅镇静钢比铝镇静更抗拒碳化物球化.. 细晶硅镇静钢比铝镇静更抗拒碳化物球化

Susceptibilit usceptibi lity y to Spheroidization pheroidization 球化易感性

•

Annealed st steels 退火钢材 are more resistant to spheroidization than normalized steels.

•

Coarse-grained st steels 粗粒度钢材 are more resistant than fine-grained.

•

Fine Fine grain grained ed silico silicon-k n-kille illed d steel steels s are are more more resist resistant ant than than alumin aluminumum-kil killed led..

•

The loss in strength 强度损失 may be as high as about 30% but failure is not likely to occur except under very high applied stresses.

Exam

DM

Temperatures

Affected materials

NO

Graphitisation

800°F~1100°F for C Steel

Plain carbon steel

875°F for for C ½ Mo Stee Steell

C, C ½ Mo



Some grades of carbon steel and 0.5Mo steels.

NO

All

Spheroidisation 850°F ~ 1400°F

Low alloy steel up to 9% Cr.

commonly used grades of carbon steel and low alloy steels including C-0.5Mo,

1Cr-0.5Mo,1.25Cr-0.5Mo, 1Cr-0.5Mo,1.25Cr-0.5Mo, 2.25Cr-1Mo, 3Cr-1Mo, 5Cr-0.5Mo, and 9Cr-1Mo steels. Spheroidization (see 4.2.2) and graphitization are competing mechanisms that occur at overlapping temperature ranges. Spheroidization tends to occur preferentially above 1025 °F (551°C), while graphitization predominates below this temperature. Discussion: Graphitization Graphitization occurs on some carbon carbon steel and 0.5Mo 0.5Mo steels only.

Spheroidization is a change in the microstructure of steels after exposure in the 850° 850°F to 1400° 1400°F (440° (440°C to 760° 760°C) range, where the carbide phases in carbon steels are unstable and may agglomerate from their their normal plate-like plate-like form to a spheroidal form. form. 碳化物球化学习重点: 碳化物球化学习重点: 1. 高温现象 1. 高温现象 – – 850° 850°F to 1400° 1400°F, 2. 原理 2. 原理:: 低合金碳钢, 低合金碳钢,高温下界面的能量减少高温下界面的能量减少,,片状珠光体转变为粒状珠光体 (片状碳化物集聚形成球状碳化物片状碳化物集聚形成球状碳化物), ), 3. 受影响材质 3. 受影响材质::涵盖了普通碳钢, 涵盖了普通碳钢, 0.5Mo钢 0.5Mo钢,低合金钢至 9Cr1Mo钢 9Cr1Mo钢, 4. 粗粒度的钢比细粒度更抗拒碳化物球化 4. 粗粒度的钢比细粒度更抗拒碳化物球化,, 5. 细晶硅镇静钢比铝镇静更抗拒碳化物球化 5. 细晶硅镇静钢比铝镇静更抗拒碳化物球化,, 6. 不同于石墨化 6. 不同于石墨化,,碳化物还是碳化物只不过高温下聚集成为球状碳化物还是碳化物只不过高温下聚集成为球状,, 7. 非 7. 非 API 510/570考试题非 510/570考试题非 API 510/570考试题 510/570考试题

API510-Exam API51 0-Exam

4.2.3 Temper Embrittlement 回火脆化



Graphitization

800° 800°F~1100° F~1100°F for C Steel Plain carbon steel / 0.5Mo

石墨化

875° 875°F for for C ½ Mo Stee Steell

Steel

850°F ~ 1400° 1400°F Spheroidization碳 Spheroidization碳 850°

0.5Mo Steel, Low alloy steel

化物球化

up to 9 % Cr

Tempered

650° 650°F~ 1070° 1070°F

2 ¼ Cr-1Mo Cr-1Mo low allo alloy y steel, steel,

Embrittlement

3Cr-1Mo (lesser extent), &

回火脆化

HSLA Cr-Mo-V rotor steels


回火脆化 4.2. 4.2.3 3 Temp Temper er Emb Embri ritt ttlement lement 回火脆化 4.2.3.1 Description of Damage Temper embrittlement embrittlement is the reduction in toughness due to a metallurgical change that can occur in some low alloy steels as a result of long term exposure in the temperature range of about 650° 650 °F to 1100° 1100°F (343° (343°C to 593° 593°C) . This change causes an upward shift in the ductile-to-brittle transition transition temperature as measured by Charpy impact testing. Although the loss of toughness is not evident at operating temperature, equipment that is temper embrittled may be susceptible to brittle fracture during start-up and shutdown. 2¼ Cr-1 Cr-1Mo Mo ~ 3Cr 3Cr-1 -1Mo Mo量低合金钢在量低合金钢在650 650°°F to 1100° 1100°F工作下,导致受影响材质, 韧脆转变温度向上移位. 工作状态下,设备不会受到此损伤机理任何影响,但在关机,重启时的低温下,材料会因回火脆性的损伤机理导致产生设备受压母材脆裂.


Temper embrittlement embrittlement is the reduction in toughness due to a metallurgical change that can occur in some low alloy steels as a result of long term exposure in the temperature range of about 650° 650 °F to 1100° 1100°F (343° (343°C to 593° 593°C) . 2¼ Cr-1M Cr-1Mo~ o~ 3Cr3Cr-1M 1Mo o钢材在650 钢材在650°°F to 1100° 1100°F 工作下, 工作下,导致受影响材质, 导致受影响材质, 韧脆转变温度向上移位.. 韧脆转变温度向上移位


4.2.3.2 Affected Materials

a) Prima Primarily rily 2 ¼ Cr-1M Cr-1Mo o (P5A) (P5A) low low alloy alloy steel steel,, 3Cr-1 3Cr-1Mo Mo (P5A) (P5A) (to (to a lesse lesserr extent), and the high-strength low alloy Cr-Mo-V (P5C) rotor steels. b) Older Older gener generati ation on 2 ¼ Cr-1M Cr-1Mo o materi materials als manuf manufact acture ured d prior prior to 1972 1972 may may be particularly susceptible. Some high strength low alloy steels are also susceptible. c) The C- ½ Mo (P (P3) and and 1 ¼ Cr- ½ Mo (P4 (P4)) all allo oy st steels eels are are not not sig signif nifican icanttly affected by temper embrittlement. However, other high temperature damage mechanisms promote metallurgical changes that can alter the toughness or high temperature ductility of these materials. Cr-1Mo Mo~ ~ 3Cr-1 3Cr-1Mo Mo低合金钢, Cr-Mo-V轴钢 Cr-Mo-V轴钢受影响. 主要是对主要是对 2¼ Cr-1 低合金钢受影响


Temper Embrittlement 回火脆性易感性

3Cr-1Mo (to a lesser extent)

Primarily 2.25Cr-1Mo low alloy steel. and the highstrength low alloy Cr-Mo-V rotor steels.

The C-0.5Mo, 1Cr0.5Mo and 1.25Cr0.5Mo alloy steels are not significantly affected.


[Embrittlement temperature 650 650° F~1070°F] °F~1070°






韧脆转变温度


韧脆转变温度向上移位


脆性转变温度向上移位.另脆性转变温度向上移位. 个特征是回火脆化, 个特征是回火脆化,不会对脆性转变点上搁架冲击功有任何影响. 任何影响.


SEM fractographs of tempered embrittled material show primarily intergranular intergranular cracking due to impurity segregation at grain boundaries 材料的回火脆化,主要是由于晶界杂质偏聚导致是沿晶开裂


http://www.twi.co.uk/news-events/bulletin/archive/1999/janua http://www.twi.co.uk/news-events/bu lletin/archive/1999/januaryryfebruary/welding-and-fabrication-of-high-t february/welding-and-f abrication-of-high-temperature-co emperature-components-formponents-foradvanced-power-plant-part-1/


4.2. 4.2.3. 3.3 3 Cri Criti tical cal Factors Facto rs 关键因素

a) Alloy steel steel composit composition, ion, thermal thermal history, history, metal metal temper temperatur ature e and exposure exposure time are critical factors. 受热历史, 受热历史,金属温度和受感时间是关键因素 b) Susceptib Susceptibility ility to to temper temper embrittle embrittlement ment is largely largely determ determined ined by the the presence of the alloying elements manganese manganese and and silicon, and the tramp elements phosphorus, phosphorus, tin, antimony, and arsenic. The strength level and heat treatment/fabrication treatment/fabrication history should also be considered. 回火脆化敏感性很大程度上决定于锰//硅与杂元素( 性很大程度上决定于锰硅与杂元素(磷/锡/锑和砷) 锑和砷)含量. 含量. c) Temper Temper embritt embrittleme lement nt of 2.25C 2.25Cr-1M r-1Mo o steels steels develops develops more more quickly quickly at at 900° 900°F (482° (482°C) than in the 800° 800°F to 850° 850°F (427° (427°C to 440° 440°C) range, but the damage is more severe after long-term exposure at 850° 850 °F (440° (440°C). 高温下易感性较大, 易感性较大,但在低温下伤害较为严重但在低温下伤害较为严重..


d) Some embrittle embrittlement ment can occur occur during during fabricatio fabrication n heat heat treatmen treatments, ts, but most most of the damage occurs over many years of service in the embrittling temperature range. 有的损伤是因建造热处理引发有的损伤是因建造热处理引发,,但一般上大多数受感于长期在敏感温度下操作引发的.. 期在敏感温度下操作引发的 e) This form form of damage damage will signifi significantl cantly y reduce reduce the structu structural ral integrit integrity y of a component containing a crack-like flaw. An evaluation of the materials toughness may be required depending on the flaw type, the severity of the environment, and the operating conditions, particularly in hydrogen service. 含裂纹状缺陷的部件会减弱结构完整性.. 特别是氢服务设备, 含裂纹状缺陷的部件会减弱结构完整性特别是氢服务设备,应在考虑缺陷的类型, 类型, 处理工艺的严峻性与操作条件处理工艺的严峻性与操作条件,,进行材料的韧性评估. 进行材料的韧性评估.


4.2.3.4 Affected Units or Equipment a) Temper Temper embrittle embrittlement ment occur occurs s in a variety variety of process process units units after after long term term exposure to temperatures above 650° 650 °F (343° (343°C). It should be noted that there have been very few industry failures related directly to temper embrittlement. b) Equipment Equipment susce susceptib ptible le to temper temper embrittl embrittlemen ementt is most most often often found found in hydroprocessing units, particularly reactors, hot feed/effluent exchanger components, and hot HP separators. Other units with the potential for temper embrittlement embrittlement include include catalytic catalytic reforming reforming units units (reactors (reactors and exchange exchangers), rs), FCC reactors, reactors, coker coker and visbreaking visbreaking units. units. c) Welds Welds in these these alloys alloys are often often more more suscept susceptible ible than than the the base metal metal and should be evaluated. 受影响的设备主要是用于高温处理单元,例如加氢装置, 受影响的设备主要是用于高温处理单元, 例如加氢装置,催化重整装置, 催化重整装置,催化裂化反应器, 化反应器,炼焦器, 炼焦器,减粘裂化单元, 减粘裂化单元,等. 焊接部位受感性比母材强焊接部位受感性比母材强,,这位应当作为评估考虑部位. 评估考虑部位.


http://www.twi-global.com/techni http://www.twi-glob al.com/technical-knowle cal-knowledge/job-kn dge/job-knowledge/d owledge/defectsefectsimperfections-in-welds-reheat-cracking-048/ http://en.wikipedia.org/wiki/Welding_defect



4.2.3.5 Appearance or Morphology of Damage a) Temper Temper embrittle embrittlement ment is is a metallurgi metallurgical cal change change that is not not readily readily apparent apparent and can be confirmed through impact testing. Damage due to temper embrittlement embrittlement may result in catastrophic brittle fracture. 外观变化不明显, 外观变化不明显,需要通过冲击试验证实需要通过冲击试验证实.. b) Temper Temper embrit embrittlem tlement ent can be ident identified ified by an an upward upward shift shift in the ductile-to ductile-to-brittle transition temperature measured measured in a Charpy V-notch impact test, as compared to the non-embrittled or de-embrittled material (Figure 4-5). Another important important characteristic characteristic of temper temper embrittlement embrittlement is that there is no effect on the upper shelf energy.夏比 energy. 夏比V V型缺口冲击试验证实韧性型缺口冲击试验证实韧性-- 脆性转变温度向上移位. 温度向上移位.另个特征是回火脆化, 另个特征是回火脆化,不会对脆性转变点上搁架冲击功有任何影响. 影响. c) SEM fract fractograp ographs hs of severe severely ly temper temper embrittl embrittled ed materia materiall show primari primarily ly intergranular cracking due to impurity segregation at grain boundaries. 主要为晶间开裂



Intergr ntergra anul nula ar Cracking Crackin g


Intergranular Cracking Metal surface Cr 5C2/ Cr 3C2 precipitated Low Cr grain boundary Crack initiation & growth

Progressive crack


Embritt mbr ittleme lement nt Mechanism chanis m

Tensile stress

Grain Boundary Cr depleted grain boundary PPT as Cr 5C2/Cr 3C2

Grain boundary decohesionCrack initiation pt.


4.2.3.6 Prevention / Mitigation a) Ex Exis isti ting ng Mate Materi rial als s 1. Temper Temper embrittl embrittlemen ementt cannot cannot be prevent prevented ed if the materi material al contains contains critica criticall levels of the embrittling impurity elements and is exposed in the embrittling temperature temperature range. 2. To minimiz minimize e the possib possibility ility of brittle brittle fracture fracture during during startup startup and shutdown shutdown,, many refiners use a pressurization sequence to limit system pressure to about 25 percent of the maximum maximum design pressure for temperatures temperatures below a Minimum Pressurization Temperature (MPT). Note that MPT MPT is not not a single point but rather a pressure temperature envelope which defines safe operating conditions to minimize the likelihood of brittle fracture.


3. MPT’ MPT’s s gene genera ralllly y rang range e fro from m 350 350°°F (171° (171°C) for the earliest, earliest, most highly highly temper embrittled steels, down to 125° 125 °F (52° (52°C) or lower lower for newer, newer, temper temper embrittlement embrittlement resistant steels (as required to also minimize effects of hydrogen embrittlement). embrittlement). 4. If weld weld repairs repairs are requi required, red, the the effects effects of temper temper embrit embrittlem tlement ent can can be temporarily reversed (de-embrittled) by heating at 1150° 1150°F (620° (620°C) [compared: embrittlement temperature 650° 650 °F~1070° F~1070°F] for for two hours hours per per inch inch of thickness, and rapidly cooling to room temperature. It is important to note that re-embrittlement re-embrittlement will occur over time if the material is re-exposed to the embrittling temperature range.


Existing Material: De-embrittlement De-embrittlement treatment.

Heating at 1150 °F (620°C) [compared: embrittlement temperature 650 °F~1070 °F (343°C to 593°C) ] for two hours per inch of thickness, and rapidly cooling to room temperature.


b) New Materials The best way to minimize the likelihood and a nd extent of temper embrittlement is to limit the acceptance levels of manganese, silicon, phosphorus, tin, antimony, and arsenic in the base metal and welding consumables. In addition, strength levels and PWHT procedures should be specified and carefully controlled. 最好的缓解方法是控制母材最好的缓解方法是控制母材//焊材的锰, 焊材的锰,硅,磷,锡,锑,砷的成分. 砷的成分.

Acceptance Level of Mn, Si, P, Sn, Sb, As.


Susceptibility usceptibi lity to temper temper embri embrittleme ttlement nt

A common common way to minimize temper temper embrittlement embrittlement is to limit the "J*" "J*" Factor for for base metal and the "X" Factor for weld metal, based on material composition as follows: J* = (Si + Mn) x (P + Sn) x 104 {elements in wt%} X = (10P + 5Sb + 4Sn + As)/100 {elements in ppm}


Typical J* and X factors used for 2.25 Cr steel are a maximum of 100 and 15 , respectively. Studies have also shown that limiting the (P + Sn) to less than 0.01% is sufficient to minimize temper embrittlement because because (Si + Mn) control the rate of embrittlement.

J* X

: 100 Max. (Base metal) : 15 Max. (Weld metal)


4.2.3.7 Inspection and Monitoring a) a) A common common metho method d of monito monitoring ring is to to install install blocks blocks of origina originall heats of of the alloy steel material inside the reactor. Samples are periodically removed from these blocks for impact testing to monitor/establish the ductile-brittle transition temperature. temperature. The test blocks should be strategically located near the top and bottom of the reactor to make sure that the test material is exposed to both inlet and outlet conditions. b) Process Process conditio conditions ns should should be monit monitored ored to ensure ensure that a proper proper pressurization sequence is followed to help prevent brittle fracture due to temper embrittlement. 4.2.3.8 Related Mechanisms Not applicable.


Figure Figure 4-5 – Plot Plot of CVN toughness as a function of temperature showing a shift in the 40-ft-lb transition temperature.




Temper embrittlement embrittlement is inherent in many steels and can be characterized by reduced impact toughness. toughness. The state of temper embrittlement has practically no effect on other mechanical properties at room temperature. temperature. Figure 1 shows schematically schematically the effect of temperature on impact toughness of alloy steel which is strongly liable to temper embrittlement. Many alloy steels have two temperature intervals of temper embrittlement. For instance, irreversible temper brittleness may appear within the interval of 250-400 °C and reversible temper brittleness, within 450°C-650°C. http://www.keytometals.com/Articles/Art102.htm


Metallurgy of Mo in alloy steel & iron Temper embrittlement may occur when steels are slowly cooled after tempering through the temperature range between 450 and 550 °C. This is due to the segregation of impurities such as phosphorus, arsenic, antimony and tin on the grain boundaries. The molybdenum atom is very large relative to other alloying elements and and impurities. It effectively impedes the migration of those elements elements and thereby provides resistance to temper embrittlement. http://www.imoa.info/molybdenum_uses/moly_grade_alloy_steels_irons/tempering.php Other/ 其他阅读 Other reference: http://www.twi.co.uk/tech http://www.twi.co.uk/technical-knowl nical-knowledge/faqs/mate edge/faqs/material-faqs/faq-w rial-faqs/faq-what-is-tempe hat-is-temperrembrittlement-and-how-can-it-be-controlled/

回火脆化学习重点: 1. 高温现象: 650°F to 1100°F, 2. 原理: 材料的回火脆化,主要是由于晶界杂质偏聚导致是沿晶开裂 3. 受影响材质:, 2.25Cr1Mo ~ 3Cr1Mo低合金钢与轴钢,不涵盖普通碳钢, 4. 最好的缓解方法是控制母材/焊材的锰,硅,磷,锡,锑,砷的成分, 5. 其他缓解方法: 控制材料强度(?)与热处理受感温度, 6. 这种脆化现象不能在高于受感温度热处理逆转恢复. 7. 除了低温冲击功,不影响其他高低温机械性能. 8. 非API 510/570考试题非API 510/570考试题

4.2.4 Strain Aging 时效伸张 (不是API510/570考试项)


Graphitisation

800° 800°F for C Steel

Plain carbon steel

875° 875°F for for C ½ Mo Steel Steel Spheroidization

850oF ~ 1400oF

Plain carbon + Low alloy steel up to 9% Cr

Tempered Embrittlement

650° 650°F~ 1070° 1070°F

2 ¼ Cr-1Mo Cr-1Mo low alloy steel, steel, 3Cr1Mo (lesser extent), & HSLA Cr-Mo-V rotor steels

Strain Aging


pre-1980’s carbon steels with a large grain size and C-0.5 Mo

885oF embrittlement

600° 600°F~ 1000° 1000°F


受影响的材质是那些老工艺的炼钢方法的普通碳钢与 0.5Mo钢 – 含有高成分的关键杂质元素与粗晶粒.

4.2. 4.2.4 4 Strain Agin Ag ing g 伸张时效

4.2.4.1 Description of Damage Strain aging is a form of damage found mostly in older vintage carbon steels and C-0.5 Mo low alloy steels under the combined effects of deformation and aging at an intermediate temperature. This results in an increase in hardness and strength with a reduction in ductility and toughness. 4.2.4.2 Affected Materials Mostly older (pre-1980’s) carbon steels with a large grain size and C-0.5 Mo low alloy steel. When susceptible materials are plastically deformed and exposed to intermediate temperatures, the zone of deformed material may become hardened and less ductile. 一般上受影响的是1980 一般上受影响的是1980年或更早前的碳钢年或更早前的碳钢((特别是大粒径 / C- ½ Mo), 当这些敏感的材料, 敏感的材料, 经过塑性变形和接触中间温度作业时，这变形材料区可能变硬和延展性与韧性降低。

Most of the effects of cold work on the strength and ductility of structural steels can be eliminated by thermal treatment, such as stress relieving, normalizing, or annealing. However, such treatment is not often necessary. 伸张时效对强度和韧性的影响能以热处理逆转恢复.

http://link.springer.com/article/10.1007%2Fs11668-006-5014-3#page-1 http://link.springer.com/article/10.1007%2FBF02715166#page-1 http://matperso.mines-paristech.fr http://matperso.min es-paristech.fr/Donnees/d /Donnees/data03/386ata03/386-belotteau0 belotteau09.pdf 9.pdf

韧性减低/抗拉曾强

拉力

AISC- Guide to Design Design Criteria for Bolted Bolted and Riveted Riveted Joints

拉力

AISC- Guide to Design Design Criteria for Bolted Bolted and Riveted Riveted Joints

4.2.4.3 Critical Factors关键因素 Factors关键因素 a) Steel Steel compositio composition n and manufact manufacturing uring process process determin determine e steel suscept susceptibilit ibility. y. b) Steels Steels manufac manufacture tured d by the Besseme Bessemerr or open hearth hearth proces process s contain contain higher levels of critical impurity elements than newer steels manufactured by the Basic Oxygen Furnace (BOF) process. c) In general general,, steels steels made made by by BOF and and fully fully killed killed with aluminum aluminum will will not be be susceptible. The effect is found in rimmed ri mmed and capped steels with higher levels of nitrogen and carbon, but not in the modern fully killed carbon steels manufactured manufactured to a fine grain practice. 受感性强材质: 受感性强材质: 含有高成分的关键杂质元素的转炉或平炉炼钢法(老炼钢法),  含大量的氢与碳元素的压盖钢/半镇静钢/沸腾钢 

不受影响材质: 

碱性氧气转炉炼钢法, 铝镇静钢,细晶粒实践钢.

d) Strain Strain aging aging effects effects are are observed observed in materia materials ls that have been been cold cold worked worked and placed into service at intermediate temperatures without stress relieving. 冷加工件( 冷加工件(无热处理) 无热处理)用于中等温度服务. 用于中等温度服务. e) Strain Strain aging aging is a major major concern concern for for equipmen equipmentt that contains contains crack cracks. s. If susceptible materials are plastically deformed and exposed to intermediate temperatures, the zone of deformed material may become hardened and less ductile. This phenomenon has been associated with several vessels that have failed by brittle fracture. 塑性变材料当接触到中等温度时, 变形的区域会变硬与减少韧性,如这材料带裂缝时会导致设备脆性断裂. f) The pres pressur suriza izatio tion n sequen sequence ce versu versus s temper temperatu ature re is a criti critical cal issu issue e to prevent brittle fracture of susceptible materials.加压顺序与温度是预防时效 materials.加压顺序与温度是预防时效伸张开裂的关键方法. g) Strain Strain aging can can also occur occur when when welding welding in the the vicinity vicinity of cracks cracks and notches in a susceptible material. 焊接加热也会加剧带裂纹的受感材料焊接加热也会加剧带裂纹的受感材料..

Bessemer Process

Bessemer Process

Bessemer Process

Bessemer Process

Open hearth Process

Open hearth Process

Open hearth Process

Open hearth Process

Basic Oxygen Process

碱性氧气转炉炼钢法



Metallurgy for Dummies http://metallurgyfordummies.c http://metallurgy fordummies.com/steelmaking-te om/steelmaking-technology/ chnology/

Capped Steel半镇静钢 Steel半镇静钢,加盖钢: 加盖钢: 









It has characteristics similar to those of rimmed steels but to a degree intermediate between those of rimmed and semi-killed steels. A deoxidizer may be added added to effect effect a controlled running action when the steel steel is cast. cast. the the gas entrapped entrapped during solidification is in excess of that needed to counteract normal shrinkage, resulting in a tendency for the steel to rise in the mould. The capping operation caused the steel to solidify faster, thereby limiting the time of gas evolution, and prevents the formation of an excessive number of gas voids within the ingot. Capped steel is generally cast in bottle-top moulds using a heavy metal cap. Capped steel may also be cast in open-top moulds, by adding aluminum or ferro-silicon on the top of molten steel, to cause the steel on the surface to lie quietly and solidify rapidly.

4) Rimmed Steel 沸腾钢, 沸腾钢,不脱氧钢: 不脱氧钢: 











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In rimmed steel, the aim is to produce a clean surface low in carbon content. Rimmed Rimmed steel is also known as drawing quality steel. The typical structure results for a marked gas evolution during solidification of outer rim. They exhibit greatest difference in chemical composition across sections and from top to bottom of the ingot. They have an outer rim that is lower in carbon, phosphorus, and sulphur than the average composition composition of the whole ingot and an inner portion or core that is higher the average in those elements. In rimming, rimming, the steel is partially deoxidized. deoxidized. Carbon content is less than 0.25% and manganese content is less than 0.6%. They do not retain any significant significant percentage of highly oxidizable elements such as Aluminum, silicon or titanium. A wide variety of steels for deep drawing is made by the rimming process, especially where ease of forming and surface finish are major considerations. These steel are, therefore ideal for rolling, large number of applications, and is adapted to cold-bending, cold-forming and cold header applications.

应变时效学习重点: 应变时效学习重点: 1. 中等温度现象 1. 中等温度现象 – – ?°F to ?° ?°F, 2. 受感材质 2. 受感材质::含有高成分的关键杂质元素的转炉或平炉炼钢法含有高成分的关键杂质元素的转炉或平炉炼钢法,,未经过热处理冷加工件. 理冷加工件.粗晶粒钢. 粗晶粒钢. 3. 受感设备 3. 受感设备:: 高厚度非热处理受感材质设备高厚度非热处理受感材质设备.. 4. 碱性氧气转炉炼钢法 4. 碱性氧气转炉炼钢法,,铝镇静钢, 铝镇静钢,细晶粒实践钢不受影响细晶粒实践钢不受影响.. 5. 蓝脆性为别名 5. 蓝脆性为别名.. 6. 非 6. 非 API 510/570考试题非 510/570考试题非 API 510/570考试题 510/570考试题

4.2.5 885 F (475 C) embrittlement 885° 885°F 脆化脆化-铁素体不锈钢/ 铁素体不锈钢/双相钢 (不是 API510/570 API510/570考试项考试项))

885°F (475°C) embrittlement 600°F~ 1000°F

Graphitisation

800° 800°F for C Steel

Plain carbon steel

875° 875°F for for C ½ Mo Steel Steel Spheroidization

850oF ~ 1400oF

Plain carbon + Low alloy steel up to 9% Cr

Tempered Embrittlement

650° 650°F~ 1070° 1070°F

2 ¼ Cr-1Mo Cr-1Mo low alloy steel, steel, 3Cr1Mo (lesser extent), & HSLA Cr-Mo-V rotor steels

Strain Aging


pre-1980’s carbon steels with a large grain size and C-0.5 Mo


600° 600°F~ 1000° 1000°F

300*, 400 & Duplex SS containing ferrite phases

受影响的材质:含铁素土的不锈钢. * 锻与铸件奥氏体不锈钢.

4.2.5 885 F (475 C) Embri mb ri ttlement tt lement 4.2.5.1 Description of Damage 

885° 885°F (475° (475°C) embrittlement is a loss in toughness due to a metallurgical change that can occur in stainless steel containing a ferrite phase, as a result of exposure in the temperature range 600° 600°F~1000° F~1000°F (316° (316°C to 540° 540°C).

4.2.5.2 Affected Materials a) 400 400 Ser Serie ies s SS SS-- ferr ferrit itic ic & mar marte tens nsit itic ic (e.g., 405, 409, 410, 410S, 430, and 446). b) Duplex Duplex stainles stainless s steels steels such such as Alloys Alloys 2205, 2205, 2304, 2304, and and 2507. 2507. c) Wrought Wrought and and cast cast 300 Series Series SS contai containing ning ferrite ferrite,, particula particularly rly welds welds and and weld overlay. 高温现象: 600° 600°F to 1000° 1000°F 含有铁素体相不锈钢 (铁素体/马氏体/双相/奥氏体-全包含)由于冶金的变化韧性的损失现象.

885 F (475 C) embri ttlement tt lement

Embrittlement Embrittlement of stainless steels containing ferrite phase upon extended exposure to temperatures between 730° 730 °F and 930° 930°F (400° (400°C and 510° 510°C ). This type of embrittlement is caused by fine, chromium-rich precipitates precipitates that segregate at grain boundaries: time at temperature directly influences the amount of segregation. Grain-boundary segregation of the chromium-rich precipitates increases strength and hardness, decreases ductility and toughness, and changes corrosion resistance. This type of embrittlement can be reversed by heating above the precipitation range. 885° 885°F 脆化, 脆化,这种类型的脆化是由于富含铬的析出物在晶界处偏析出这种类型的脆化是由于富含铬的析出物在晶界处偏析出..晶界偏析的富含铬的析出增加强度和硬度,,降低塑性和韧性和耐腐蚀变化的富含铬的析出增加强度和硬度降低塑性和韧性和耐腐蚀变化((减弱). 减弱).这种脆这种脆化现象能在高于析出温度热处理逆转恢复.. 化现象能在高于析出温度热处理逆转恢复 http://www.keytometals.com/page.asp http://www.keytometals .com/page.aspx?ID=CheckAr x?ID=CheckArticle&site=kts&LN ticle&site=kts&LN=CN&NM=102 =CN&NM=102

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Most refining companies limit the use of ferritic stainless steels to nonpressure boundary applications because of this damage mechanism.

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885° 885°F embrittlement embrittlement is a metallurgical change change that is not readily apparent apparent with metallography but can be confirmed through bend or impact testing (Figure 4-6).

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The existence of 885° 885 °F embrittlement can be identified by an increase in hardness in affected areas. Failure during bend testing or impact testing of samples removed from service is the most positive indicator of 885° 885°F embrittlement.

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885° 885°F embrittlement is reversible by heat treatment to dissolve precipitates, followed by rapid cooling. The de-embrittling heat treatment temperature is typically 1100° 1100°F (593° (593°C) or higher and may not be practical for many equipment items. If the de-embrittled component is exposed to the same service conditions conditions it will re-embrittle faster than it did initially.

4.2.5.3 Critical Factors 关键因素 a) The alloy alloy compositio composition, n, particula particularly rly chromium chromium conten content, t, amount amount of ferrit ferrite e phase, and operating temperature are critical factors. 铬,铁素体相的数量和操作温度 b) Increasin Increasing g amounts amounts of ferrit ferrite e phase increas increase e susceptib susceptibility ility to damage damage when operating in the high temperature range of concern. A dramatic increase in the ductile-to-brittle transition temperature will occur. 越来越多的铁素体相的增加损伤的易感性(韧脆转变温度显著提高) c) A primary primary considera consideration tion is operat operating ing time time at temperat temperature ure within within the the critical critical temperature range. Damage is cumulative and results from the precipitation of an embrittling intermetallic phase that occurs most readily at approximately 885° 885°F (475° (475°C). Additional time is required to reach maximum embrittlement at temperatures above or below 885° 885 °F (475° (475°C). For example, many thousands of hours may be required to cause embrittlement at 600° 600°F (316° (316°C). 损伤是因在受感温度操作时损伤是因在受感温度操作时,,金属间项 (intermetallic phase)的溢出 phase)的溢出//沉淀在晶间导致的. 沉淀在晶间导致的.

d) Since 885°F embrittlement can occur occur in a relatively short period of time, it is often assumed that susceptible materials that have been exposed to temperatures temperatures in the 700° 700°F to 1000° 1000°F (371° (371°C to 538° 538°C) range are affected. 受感温度一般上定义为700 受感温度一般上定义为 700°°F至1000° 1000°F 之间 e) The effect effect on on toughnes toughness s is not pronounc pronounced ed at the the operating operating tempe temperatu rature, re, but is significant at lower temperatures experienced during plant shutdowns, startups or upsets.对韧性的影响体现在较低于操作温度例如在 upsets. 对韧性的影响体现在较低于操作温度例如在停机, 停机,启动和颠覆状态时. 启动和颠覆状态时. f) Embri Embritt ttlem lement ent can can result result from from tem temper pering ing at high higher er temp tempera eratur tures es or by holding within or cooling through the transformation range. 在受感温度回火热处理或当冷却时在受感((转变) 在受感温度回火热处理或当冷却时在受感转变)温度停留会导致885 温度停留会导致885°°F脆化. 脆化.

Fig. 2—Microstructure of solution-annealed 304LN stainless steel

Fig. 3—Oxalic acid etched microstructures of 304LN stainless steel sensitized for (a) 1 h, (b) 25 h, (c) 50 h, and (d) 100 h.

4.2.5. 2.5.7 7 Inspectio Inspect ion n and Monit on itor orin ing g

a) Impact Impact or bend bend testing testing of sample samples s removed removed from servic service e is the most most positive positive indicator of a problem. b) Most Most cases cases of embrittl embrittleme ement nt are found found in the form form of cracki cracking ng during during turnarounds, or during startup or shutdown when the material is below about 200° 200°F (93° (93°C) and the effects of embrittlement are most detrimental. c) An increas increase e in hardness hardness is is another another method method of evaluati evaluating ng 885 885°F embrittlement.

Impact energy and brinell hardness as function of time exposure qt 475 °C 475oC Embrittlement in a Duplex Stainless Steel UNS S31803

475oC Embrittlement in a Duplex Stainless Steel UNS S31803 http://www.scielo.br/scielo.php?pid=S1516-14392001000400003&script=sci_arttext

http://www.sciencedirect.com/science http://www.scienced irect.com/science/article/pii/S /article/pii/S092150 0921509309000 9309000197 197

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885° 885°F (475° (475°C) Embrittle Embrittlement ment of of stainless stainless steels steels in alloys alloys containing a ferrite phase (Ferritic/Martensitic/Duplex (Ferritic/Martensitic/Duplex stainless steel and ferrite phases in austenitic stainless steel e.g. weld areas) 影响材质: 影响材质: 含铁素体的不锈钢

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Grain-boundary segregation of the chromium-rich precipitates increases strength and hardness, decreases ductility and toughness, and changes corrosion resistance (lower). 含富铬金属间(intermetallic)在晶间溢出导致脆化.

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This type of embrittlement can be reversed by heating above the precipitation range.可以通过加热逆转恢复 range.可以通过加热逆转恢复

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Impact testing/bend test & hardness testing used to evaluate susceptibility. 冲击试验,弯曲试验,硬度试验作为易感性的评估.

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Restrict the used of ferritic steel to non-pressure boundary application. 限制铁素体不锈钢用于非受压用途限制铁素体不锈钢用于非受压用途..

4.2.6 Sigma-Phase Embrittlement “西格玛” 西格玛”相脆化 (不是API510/570考试项)

Sigmaig ma-P Phase Embrit Embr ittl tle ement 1000o F~1700o F


600° 600°F~ 1000° 1000°F

300*, 400 & Duplex SS containing ferrite phase

Sigma phase embrittlement

1000° 1000°F~ 1700° 1700°F


受影响的材质:含铁素体的不锈钢, * 锻与铸件奥氏体不锈钢

4.2. 4.2.6 6 Sigma Sigm a Phase Phase Embrit Embr ittl tlement ement 4.2.6.1 Description of Damage

Formation of a metallurgical phase known as sigma phase can result in a loss of fracture toughness in some stainless steels as a result of high temperature temperature exposure. 4.2.6.2 Affected Materials a) 300 Seri Series es SS wrou wrought ght meta metals, ls, weld weld met metal, al, and and casti castings ngs.. Cast Cast 300 Series Series SS including the HK and HP alloys are especially susceptible to sigma formation because of their high (10-40%) ferrite content. b) The 400 400 Serie Series s SS and and other other ferr ferriti itic c and marte martensi nsitic tic SS SS with with 17% Cr or more are also susceptible (e.g., Types 430 and 440). c) Dupl Duplex ex stai stainl nles ess s stee steels ls.. 受影响的材质: 受影响的材质: 铁素体不锈钢, 铁素体不锈钢,含铁素体的马氏体, 含铁素体的马氏体,奥氏体不锈钢和双相不锈钢奥氏体不锈钢和双相不锈钢.. 脆化原因: 脆化原因: 在受感温度下, 在受感温度下,西格玛相形成,在铁素体项析出导致脆化. http://www.hindawi.com/journals/isrn.metallurgy/2012/732471/

西格玛玛相脆化 Sig igmama-P Phase Emb Embri ritt ttlement lement 西格 Description: Embrittlement Embrittlement of iron-chromium alloys caused by precipitation at grain boundaries of the hard, brittle intermetallic sigma phase σ during long periods of exposure to temperatures between approximately approximately 565oC and 980oC (1050oF and 1800oF). Sigma phase embrittlement results in severe loss in toughness and ductility and can make the embrittled material structure susceptible to intergranular corrosion. F)之间,硬而脆的金在长时间暴露在温度约 565oC ~ 980oC (1050oF ~ 1800oF) 之间,硬而脆的金属间化合物(σ 属间化合物( 相)在铁素体晶界处析出,, σ相脆化导致的韧性和延展性严重损失 σ相)在铁素体晶界处析出 σ相脆化导致的韧性和延展性严重损失与导致易受晶间腐蚀. http://www.keytometals.com/page.asp http://www.keytometals .com/page.aspx?ID=CheckAr x?ID=CheckArticle&site=kts&LN ticle&site=kts&LN=CN&NM=102 =CN&NM=102

4.2.6.3 Critical Factors 关键因素 a) Alloy compo compositio sition, n, time time and tempera temperature ture are are the critic critical al factors factors.. 化学成分, 化学成分, 时间, 时间, 温度都是关键因素. 温度都是关键因素. b) In suscept susceptible ible alloys, alloys, the the primary primary factor factor that that affects affects sigma sigma phase phase formation is the time of exposure at elevated temperature. 易感材料; 易感材料;时间与经历温度为主要因素.. 与经历温度为主要因素 c) Sigma Sigma phase phase occurs occurs in ferritic ferritic (Fe-Cr) (Fe-Cr),, martens martensitic itic (Fe-Cr), (Fe-Cr), austeniti austenitic c (FeCr-Ni) and duplex stainless steels when exposed to temperatures in the range of 1000° 1000°F to 1700° 1700°F (538° (538°C to 927° 927°C). Embrittlement can result by holding within or cooling through the transformation range. 铁素体, 铁素体,马氏体, 马氏体, 奥氏体, 奥氏体,双相钢, 双相钢,当停留或冷却途径1000 当停留或冷却途径1000°°F to 1700° 1700°F 温度时,产生σ相析出. d) Sigma Sigma forms forms most rapidl rapidly y from the the ferrite ferrite phase phase that exists exists in 300 300 Series Series SS and duplex SS weld deposits. It can also form in the 300 Series SS base metal (austenite phase) but usually more slowly. σ相以较快的速度在铁素体相析出,但也会在奥氏体项较慢的速度析出.

e) The 300 300 Series Series SS can can exhibit exhibit about about 10% 10% to to 15% sigma sigma phase. phase. Cast Cast austenitic stainless steels can develop considerably more sigma. 相在奥氏体不锈钢以10%~15%表现出来表现出来,,铸件可能还高. 铸件可能还高. σ 相在奥氏体不锈钢以10%~15% f) Format Formation ion of sigma sigma phase phase in aust austeni enitic tic stain stainles less s stee steels ls can also also occur occur in in a few hours, as evidenced by the known tendency for sigma to form if an austenitic stainless steel is subjected to a post weld heat treatment at 1275° 1275°F (690° (690°C). σ相在奥氏体的析出只需几个小时,这脆化趋向可以从1275 这脆化趋向可以从1275°°F焊接热处理后, 出现σ相的到证明. g) The tensile tensile and and yield yield strength strength of of sigmatize sigmatized d stainless stainless steel steels s increases increases slightly slightly compared compared with solution solution annealed annealed material. material. This increase in strength is accompanied accompanied by a reduction in ductility (measured by percent elongation and reduction in area) and a slight increase in hardness. σ相脆化后,抗拉强度.硬度相比固溶退火材料略有增加, 同时,延展性与韧性减少.

Σ(σ)phase in austenitic matrix http://www.intecho pen.com/books/met allurgy-advancesin-materials-and processes/homogeni zation-heattreatment-toreduce-the-failureof-heat-resistantsteel-castings

Σ(σ)phase in austenitic matrix

h) Stainless Stainless steels steels with with sigma sigma can normall normally y withstand withstand norma normall operating operating stresses, but upon cooling to temperatures below about 500° 500 °F (260° (260°C) may show a complete lack of fracture toughness as measured in a Charpy impact test. Laboratory tests of embrittled weld metal have shown a complete lack of fracture toughness below 1000° 1000 °F (538° (538°C) 一般上材料在正常操作温度时不受西格玛相脆化影响,但是当材料温度降至 500° 500°F材料完全缺乏韧性(实验室导致完全缺乏韧性的温度可能高至实验室导致完全缺乏韧性的温度可能高至1000 1000°°F). i) The meta metallu llurgi rgical cal chan change ge is actu actuall ally y the prec precipi ipitat tation ion of of a hard, hard, brit brittle tle intermetallic compound that can also render the material more susceptible to intergranular corrosion. The precipitation rate increases with increasing content.缺乏韧性是因硬脆性金属间化合物沉 chromium and molybdenum content.缺乏韧性是因硬脆性金属间化合物沉淀在晶间.随着铬和钼含量提高,沉淀率相应加速.

σ相脆化- 缺乏韧性是因硬脆性金属间(intermetallic-sigma phase)化合物沉淀在晶间.随着铬和钼含量提高,沉淀率相应加速.

Cr% & Mo% 铬和钼含量增加

The precipitation rate increases σ 相析出增加

4.2.6.4 Affected Units or Equipment a) Common Common examples examples include include stainle stainless ss steel steel cyclones, cyclones, piping piping ductwo ductwork rk and valves in high temperature FCC ( fluidized catalytic cracking )Regenerator service. b) 300 Series Series SS weld weld overlays overlays and tube-to tube-to-tube -tubeshee sheets ts attachm attachment ent welds welds can be embrittled during PWHT treatment of the underlying CrMo base metal. c) Stainless Stainless steel steel heater heater tubes tubes are suscepti susceptible ble and and can be embritt embrittled. led.

FCC (fluidized catalytic cracking ) Regenerator service



http://www.phxequip.com/plant.73/fluid-catalytic-cracker-unit.aspx



Stainless steel heater tubes

Stainless steel heater tubes

tube-to-tubesheets attachment




4.2.6.5 Appearance or Morphology of Damage 损伤外观形态 a) Sigma Sigma phase phase embrittl embrittlemen ementt is a metallu metallurgica rgicall change change that is not readily readily apparent, and can only be confirmed through metallographic examination and impact testing. (Tables 4-1 and 4-2)外观上不能体现损伤 4-2) 外观上不能体现损伤,,只能依靠金相分析和冲击试验 b) Damage Damage due to sigma sigma phase phase embritt embrittlemen lementt appears appears in the form form of crackin cracking, g, particularly at welds or in areas of high restraint. σ相脆化一般上以开裂的形态出现特别是在焊缝与高抑制区域. c) Tests Tests performe performed d on sigma sigmatize tized d 300 Series Series SS (304H) (304H) samples samples from from FCC FCC regenerator internals have shown that even with 10% sigma formation, the Charpy impact toughness was 39 ft-lbs (53 J) at 1200° 1200 °F (649° (649°C). 材料: 材料: 304H 敏化度: 敏化度: 10%σ相 10%σ相温度/冲击功: 649° 649°C / 53J

设备: 设备:催化裂化再生器材料: 材料: 304H 敏化度: 敏化度: 10%σ相 10%σ相 649°C / 53J 温度/冲击功: 649° 新材料的机械性能: 新材料的机械性能: SPECIFICATION FOR HEAT-RESISTING CHROMIUM AND CHROMIUM-NICKEL STAINLESS STEEL PLATE, SHEET, AND STRIP FOR PRESSURE VESSELS ASTM SA-240

SPECIFICATION FOR HEAT-RESISTING CHROMIUM AND CHROMIUM-NICKEL STAINLESS STEEL PLATE, SHEET, AND STRIP FOR PRESSURE VESSELS ASTM SA-240

d) For the 10% 10% sigmatize sigmatized d specimen, specimen, the the values values ranged ranged from from 0% ductilit ductility y at room temperature to 100% at 1200° 1200 °F (649° (649°C). Thus, Thus, althou although gh the the impact impact toughness is reduced at high temperature, the specimens specimens broke in a 100% ductile fashion, indicating that the wrought material is still suitable at operating temperatures. See Figures 4-7 to 4-11.敏化 4-11. 敏化材材料的室温料的室温延展性或许降至为零.但在1200 但在1200°°F材料的延展性可能不受任何的影响材料的延展性可能不受任何的影响.. e) Cast austen austenitic itic stainles stainless s steels typically typically have have high ferrite/ ferrite/sigm sigma a content content (up to 40%) and may have very poor high temperature ductility.铸造奥氏 ductility.铸造奥氏体不锈钢敏化都可能高至40%的σ相,这导致很差的高温塑性/延展性.

Evaluation of Sigma Phase Embrittlement of a Stainless Steel 304H Fluid Catalyst Cracking Unit Regenerator Cyclone 不锈钢 304H催化裂化再生旋风器σ相脆化评价. Author Aut hors: s: Ali Ali Y. Al-Ka Al-Kawai waiee and Abd Abdelh elhak ak Ker Kermad mad ABSTRACT Testing was performed on a 304H stainless steel sample s ample removed from a Fluid Catalyst Cracking Unit (FCCU) regenerator cyclone after 25 years of service to check for sigma phase formation. Sigma phase is a nonmagnetic inter-metallic phase composed mainly of iron and chromium (FeCr), which forms in ferritic and austenitic stainless steels during exposure at the temperature range 1,050 °F to 1,800 °F (560 °C to 980 °C), causi causing ng loss of ductility ductility and toughne toughness. ss. Cracking Cracking may also occur if the component was impact-loaded or excessively stressed during shutdown or maintenance work. This article discusses the effect of sigma phase embrittlement on the FCCU regenerator cyclone after extended high temperature service. http://www.saudiaramco.com/content/dam/Publications/Journa l%20of%20Technology/Spring2011/Art%2012%20%20JOT%20Internet.pdf

Table 3. Micro-hardness Micro-hardness testing. Test load: 200 g, Calibration Block Hardness: 256 + 10 HV, Measured Hardness of the calibration block: 258 VHN.

Table 2. Impact testing (Test Method: ASTM E23)

Fig. 1. Cyclone sample, as received.

Fig. 2. Micrograph showing carburized layer at the outer (top) surface, 100x (As received).

Fig. 3. Micrograph showing the microstructure at the outer (top) surface, 100x (Heat treaded).

Note: solution annealing annealing at 1,066 1,066 °C for four four hours, hours, follow followed ed by a water water quench before testing.

Fig. 4. Micrograph showing sigma formation at the center of the sample. Estimated volume fraction 7%, 100x (As received).

Fig. 5. Micrograph showing the microstructure at the center of the heat treated sample, 100x (Heat treated).


Fig. 6. Micrograph showing sigma phase at the inner (bottom) surface of the original sample, 100x (As received).

Fig. 7. Micrograph showing the microstructure at the inner surface of the heat treated sample, 100x (Heat treated).


Fig. 8a. SEM fractography fractography showing showing the brittle fracture surface surface (Top - As received) received)

Fig. 8b. SEM fractography showing showing the ductile ductile fracture (Bottom - Heat treated) of of the impact tested samples.

4.2.6.6 Prevention / Mitigation a) The best best way to prevent prevent sigma sigma phase phase embritt embrittleme lement nt is to use use alloys alloys that are are resistant to sigma formation or to avoid exposing the material to the embrittling range. 最好的预防方法是不用易敏材料与避免使材料暴露在脆化温度范围作业(这牵涉到设定合适的IOW) b) The lack lack of fracture fracture ductility ductility at room room temperatu temperature re indicates indicates that that care should should be taken to avoid application of high stresses to sigmatized materials during shutdown, as a brittle fracture could result. 室温断裂韧性不足是σ相脆化损伤机理的特点. 这显著地影响设备在启动,关断与瞬态状态的使用; 在设备处于低温状态时避免设备受到高应力(设备随着温度提高增加设备受压).* c) The 300 300 Series Series SS can can be de-sig de-sigmatiz matized ed by soluti solution on annealin annealing g at 1950 1950°°F (1066° (1066°C) for four hours followed by a water quench. However, this is not practical for most equipment. σ相脆化损伤可以可以通过加热逆转恢复(温度 1950° 1950°F固溶退火). 然而这往往并不是在役设备实用的修护方案. Note* 注意设备压力试验时可能导致低温脆裂的危险注意设备压力试验时可能导致低温脆裂的危险..

d) Sigma phase phase in welds welds can can be minimize minimized d by controlli controlling ng ferrite ferrite in the the range range of 5% to 9% for Type 347 and somewhat less ferrite for Type 304. The weld metal ferrite content should be limited to the stated maximum to minimize sigma formation during service or fabrication, and must meet the stated minimum in order to minimize hot short cracking during welding. 奥氏体不锈钢铁素体含量的控制用于减少σ相脆化的形成. e) For stainl stainless ess steel steel weld weld overlay overlay clad Cr-Mo Cr-Mo compo components nents,, the expos exposure ure time time to PWHT temperatures should be limited wherever possible.铬钼覆盖层焊后热处理尽量减少暴露时间.

What causes knife-line attack? For stabilized stabilized stainless stainless steels steels and alloys, alloys, carbon is bonded with stabilizers (TiC or NbC) and no weld decay occurs in the heat affected zone during welding. In the event of a subsequent heat treatment or welding (above 1200oC), however, first the TiC / NbC may dissociated into free Ti, Nb and C, on cooling precipitation of chromium carbide Cr 23C6 is possible and this leaves the narrow band adjacent to the fusion line susceptible to intergranular corrosion.

What causes weld decay? As in the case of intergranular corrosion, grain boundary precipitation, notably chromium carbides in non-stabilized stainless steels, is a well recognized and accepted mechanism of weld decay. In this case, the precipitation of chromium carbides is induced by the welding operation when the heat affected zone (HAZ) experiences a particular temperature range (550oC~850oC). The precipitation of chromium chromium carbides consumed consumed the alloying element element - chromium chromium from a narrow band along the grain boundary and this makes the zone anodic to the unaffected un affected grains. The chromium depleted zone becomes the preferential path for f or corrosion attack or crack c rack propagation if under tensile stress.

Anodic site

4.2.6.7 Inspection and Monitoring 检验与监测 a) Physical Physical testin testing g of samples samples removed removed from from service service is the most most positive positive indicator of a problem. 设备采样机械试验时最好的方法确认损伤机制设备采样机械试验时最好的方法确认损伤机制.. b) Most Most cases cases of embri embrittle ttlement ment are found in the the form form of cracking cracking in in both wrought and cast (welded) metals during turnarounds, or during startup or shutdown when the material is below about 500° 500 °F (260° (260°C) and the effect effects s of embrittlement are most pronounced. σ相脆化开裂失效模式一般出现于设备温度处于低于500°F (260°C) 状态例如当设备周转,启动,关断时. 4.2.6.8 Related Mechanisms 相关机制 Not applicable.不适用 applicable.不适用

Figure 10: 10: Shaeffler diagram showing showing the embrittlement region of theσ phase [33]. http://www.hindawi.com/journals/isrn.metallurgy/2012/732471/

http://www.metalconsult.com/failure-analysis-furnace-tubes.html

http://www.metalconsult.com/failure-analysis-furnace-tubes.html

http://www.metallograf.de/start-eng.htm?/untersuchungen-eng/sigmaphase/sigmaphase.htm

http://www.industrialheating http://www.indu strialheating.com/articles/9 .com/articles/90371-sigm 0371-sigma-phase-e a-phase-embrittlement mbrittlement http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1517-70762009000300017

Table 4: Chemical composition of ferrite austenite and sigma phases at 900 oC

Polishing markings

Improperly etched specimen showing little or no sign of sigma phase

NaOH etched

Oxalic acid etchedDuplex SS

Sigma-phase embrittlement

高温现象:1000 高温现象:1000oF~1700oF 影响材质:铁铬合金  影响材质: 原理:σ相脆化损伤机理: σ相脆化损伤机理: 是当铁铬合金暴露在高温下是当铁铬合金暴露在高温下,, 硬,脆性的σ相金属间  原理: 化合物晶界沉淀引起的脆性现象.. 化合物晶界沉淀引起的脆性现象解决方法: σ相脆化损伤可以可以通过加热逆转恢复 σ相脆化损伤可以可以通过加热逆转恢复((温度1950 温度1950°°F固溶退火). 固溶退火).  解决方法: 然而这往往并不是在役设备实用的修护方案.. 然而这往往并不是在役设备实用的修护方案 510/570考试项  非 API 510/570 

API510/570-Ex A PI510/570-Exam am

4.2.7 Brittle Fracture 脆性破裂 API 510/570考试学习科目


Brittle Fracture Below DTBTT DTBT: Ductile to brittle transition temperature.


No shear lip, little micro void coalescence, little deformation deformation


4.2.7 2.7 Britt Bri ttle le Fracture Fractu re 脆性断裂 4.2.7.1 Description of Damage 损伤描述

Brittle fracture is the sudden rapid fracture under stress (residual or applied) where the material exhibits little or no evidence of ductility or plastic deformation. 脆性断裂脆性断裂- 在应力( 在应力(残余或应用) 残余或应用)作用下突然快速断裂. 作用下突然快速断裂.材料表现出很少的延展性, 少的延展性, 塑性变形. 塑性变形. 4.2.7.2 Affected Materials 受影响材质 Carbon steels and low alloy steels are of prime concern, particularly older steels. 400 Series SS are also susceptible. 受影响的材质有; 受影响的材质有; 碳钢, 碳钢, 低合金钢与铁素体/ 铁素体/马氏体不锈钢 Affected Materials Ferritic/Martensitic Ferritic/Martensitic STEELS STEELS 只对铁素体/ 只对铁素体/马氏体钢材影响


4.2.7.3 Critical Factors 关键因素 a) When When the the criti critical cal com combin binati ation on of three three fact factors ors is is reache reached, d, brit brittle tle fractu fracture re can can occur: 1. The The mat mater eria ials ls’’ frac fractu ture re toug toughn hnes ess s (res (resis ista tanc nce e to to cra crack ck like like flaw flaws) s) as as measured in a Charpy impact test;断裂韧性 test; 断裂韧性 2. The The size size,, shap shape e and and stre stress ss con conce cent ntra rati tion on eff effec ectt of a flaw flaw;; 应力的形状与大小 3. The The amo amoun untt of of res resid idua uall and and appl applie ied d str stres esse ses s on on the the flaw flaw.. 残余或外加应力 b) Suscep Susceptib tibili ility ty to brit brittle tle fractu fracture re may may be be incre increase ased d by the presen presence ce of of embrittling phases. 晶体脆化相存在会增加脆裂易感性 c) Stee Steell clea cleanl nline iness ss and and gra grain in siz size e have have a sig signi nifi fica cant nt inf influ luen ence ce on on toug toughn hnes ess s and resistance to brittle fracture.钢的纯净度和晶粒大小显著地影响材料韧性 fracture.钢的纯净度和晶粒大小显著地影响材料韧性和断裂抗拒能力.


d) Thicke Thickerr mater material ial sect section ions s also also have have a lower lower resis resista tance nce to brit brittle tle fractu fracture re due to higher constraint which increases triaxial stresses at the crack tip. 较厚的材料因更高的应力约束,增加了在裂纹尖端的三轴应力;导致较低的断裂阻力 d) In most most cases, cases, britt brittle le frac fractur ture e occur occurs s only only at at temp tempera eratu tures res below below the the Charpy impact transition temperature (or ductile-to-brittle transition temperature), the point at which the toughness of the material drops off sharply. 一般上脆裂发生在低于韧脆转变温度.


Definition of Brittle Fracture 脆性断裂定义 a steel member may experience a brittle fracture. Three basic factors contribute to a brittle-cleavage type of fracture. They are; • • •

a triaxial state of stress, a low temperature, and a hig high h str strai ain n rat rate e or or rap rapid id rate rate of load loadin ing. g.

All these factors need not not be present. Crack often propagates by cleavage cleavage – breaking of atomic bonds along specific crystallographic planes (cleavage planes), propagate rapidly without further increase in applied stress (applied or residual) with little indication of plastic deformation. In contrast, a ductile fracture occurs mainly by shear, shear, usually preceded by considerable plastic deformation.





Figure 7: The fracture examination using a SEM on C1 and C2 revealed features typical of transgranular fracture (left and and middle) middle) and signatures signatures of intergranular cracking (left and right). The presence presence of both both intergranular intergranular and transgranular transgranular features indicates a mixed-mode fracture morphology. http://www.drillingcontractor.org/tubular-fracturing-pinpointing-the-cause-14544


In Case 2 from Oklahoma, the pin connection twisted off while making up the pin connection of a saver sub. http://www.drillingcontractor.org/tubular-fracturing-pinpointing-the-cause-14544


Figure 4: The fracture fracture on the Case Case 1 sub showed showed a grainy texture texture and “chevron “chevron marks” that point toward the initiation site, which is typical typical morphology morphology for brittle cracking


Figure 5: The fracture on C3 exhibited a small fatigue region that was followed by brittle fracture. The fracture surface had a grainy appearance and presented a minuscule shear lip, which is also typical of a brittle fracture


Various stages during ductile fracture 韧性断裂 are schematically shown in above figure. (a) Necking, 缩颈 (b) Cavity formation (microvoid), 微孔形成 (c) Cavity coalescence to form a crack (microvoid coalescence), 微孔的聚结 (d) Crack propagation, 裂缝蔓延 (e) Fracture (shear fracture). 断裂 (剪切断裂)




Brittle fracture of a shaft caused by a small fatigue crack close to the keyway. The fatigue would be expected to start at the keyway root but actually began at a surface defect. http://www.surescreen.com/scientifics/library-of-failures.php






http://www.wermac.org/misc/pressuretestingfailure2.html


4.2.7.4 Affected Units or Equipment 受影响的单元或设备 a) Equipmen Equipmentt manufac manufactured tured to the ASME Boiler Boiler and Pressu Pressure re Vessel Vessel Code, Code, Section VIII, Division 1, prior to the th e December 1987 Addenda, were made with limited restrictions on notch toughness for vessels operating at cold temperatures. temperatures. However, this does not mean that all vessels fabricated prior to this date will be subject to brittle fracture. fracture. Many Many designers designers specified supplemental supplemental impact tests on equipment that was intended to be in cold service. ASME锅炉和压力容器规范 ASME锅炉和压力容器规范1987 1987年 12月前,因为对低温操作设备缺乏材料韧性年12月前要求的限制,这些设备可能有脆裂的隐患. 然而虽然不是规范要求,有的设计会因设备低温操作,对材质附加低温冲击要求. b) Equipmen Equipmentt made made to the the same same code after after this date date were were subject subject to to the requirements of UCS 66 (impact exemption curves). 引用 ASME VIII DIV1 UCS 66 对材料冲击要求宽松条款的设备对材料冲击要求宽松条款的设备..


c) Most processes processes run run at elevat elevated ed tempera temperature ture so so the main main concer concern n is for britt brittle le fracture during startup, shutdown, or hydrotest/tightness hydrotest/tightness testing. Thick wall equipment on any unit should be considered. 在设备因周转, 在设备因周转,启动, 启动,停机时低温状态 d) Brittle Brittle fracture fracture can can also occur occur during during an auto-refr auto-refrigera igeration tion event event in units units processing light hydrocarbons such as methane, ethane/ethylene, ethane/ethylene, propane/propylene, or butane. This includes alkylation units, olefin units and polymer plants (polyethylene and polypropylene). Storage bullets/spheres for light hydrocarbons may also be susceptible. 蒸发自动冷却服务. 蒸发自动冷却服务. e) Brittle Brittle fracture fracture can can occur occur during ambien ambientt temperat temperature ure hydrote hydrotestin sting g due to high stresses and low toughness at the testing temperature. 室温试压时

UCS-66 MATERIALS.

The main material property that API 510 / ASME VIII is concerned with is that of resistance to brittle fracture. The fundamental issue is therefore whether a material is suitable for the minimum design metal temperature (MDMTdesign) for which a vessel is designed. This topic is covered by clause UCS-66 of ASME VIII.

Steps: 1. UG-20 UG-20 for for exem exemptio ption n on impact impact testin testing. g. 2. UCS-66. • Iden Identi tifi fied ed mate materi rial al Grou Group p A, A,B,C, B,C,D. D. • Figu Figure re UCSUCS-66 66 to dete determ rmin inee the the allo allowa wabl blee MDM MDMT. T. • Figu Figure re UCS UCS-6 -66. 6.1 1 to dete determ rmin inee the the redu reduct ctio ion n in MDMT MDMT bas based ed on coincident ratio. 3. UCS-68 UCS-68(c) (c) to dete determi rmine ne on furth further er reduct reduction ion in MDMT. MDMT.

Figure UCS 66.1 Coincident Ratio The Coincident Ratio is based on a vessel’s extra thickness due to its design calculations which were based on its Maximum Temperature. Meaning that; As metal’s temperature increases its strength decreases, hotter hotter means weaker, weaker, therefore therefore the allowable allowable stress is decreased decreased during during calculations resulting in vessel that requires thicker walls when hot than when it is operating at its coldest temperature, the MDMT. This ratio takes credit for the extra wall thickness that is present, but not needed needed to resist pressure pressure at the MDMT. The The following following graphic graphic will help. Usually when there is a drop in temperature there is also a drop in the pressure. pressure. The The two operating operating condition conditionss are calculated calculated and and the Ratio is determined. This Ratio is given on the exam and you need only use the table to apply this rule.

How to use FIG. UCS-66 & FIG. UCS-66.1 to determine allowable impact test value (MDMTallowable)

Steps: 1. Dete Determ rmin inee mate materi rial al grou group. p. 2. Determine MDMT allowable on the graph. 3. If Desi Design gn MDMT MDMT high higher er than than MDMT allowable, no test requires. 4. If MDMT allowable is higher than design design MDMT MDMT goto FIG. FIG. UCSUCS66.1

Steps: 5. If the the coi coinc ncid iden entt rat ratio io is 0.70 0.70 reduction of 30oF from the MDMT allowable. The revised MDMT’ allowable = 59oF. 6. If the the re revise vised d MDM MDMT T’ allowable is higher than the design MDMT, check on item 7. 7. If mat mater eria iall is P1, P1, UCS UCS-6 -68( 8(c) c) If postweld heat treating is performed when when it is not otherwise a requirement of this Division, a reduction of 30oF. The resulting MDMT allowable may be colder than 55oF.

Once the MDMT allowable allowable had been ascertained, ascertained, further further reductions reductions are possible by within -55ºF capping with exception 1. Low Low coi coinc ncid iden entt str stres ess s rat ratio io 2. postweld postweld heat heat treating treating is is performe performed d when it it is not other otherwise wise a require requirement ment of this Division on P1 materials.

- 55oF

UCS-66 (b2) For minimum design metal temperatures colder than -55ºF (48ºC), impact testing is required for all materials, except as allowed in (b)(3) below and in UCS-68(c). UCS-66 (b3) When the minimum design metal metal temperature temperature is colder colder than 55ºF (-48ºC) and no colder than -155ºF (-105ºC), and the coincident ratio defined in Fig. UCS-66.1 is less than or equal to 0.35, impact testing is not required.

UCS-66 (b2) For minimum design metal temperatures colder than -55ºF (48ºC), impact testing is required for all materials, except as allowed in (b)(3) below and in UCS-68(c). UCS-68(c) If postweld heat treating is performed when it is not otherwise a requirement of this Division, a 30ºF (17ºC) reduction in impact testing exemption temperature temperature may be given to the minimum permissible temperature from Fig. UCS-66 for P-No. 1 materials. The resulting exemption temperature temperature may be colder than -55ºF (-48ºC).


4.2.7.5 Appearance or Morphology of Damage a) Cracks Cracks will typical typically ly be straight, straight, non-branch non-branching, ing, and and largely largely devoid devoid of any associated plastic deformation deformation (no shear lip or localized necking around the crack) (Figure 4-6 to Figure 4-7). 宏观: 宏观:直,不分枝, 不分枝,并在很大程度上没有任何相关的塑性变形并在很大程度上没有任何相关的塑性变形.. b) Microsco Microscopical pically, ly, the the fracture fracture surface surface will be compose composed d largely largely of cleavage, cleavage, with limited intergranular cracking and very little microvoid coalescence. 微观: 微观: 主要为分裂( 主要为分裂(少量的沿晶开裂?) 少量的沿晶开裂?)与非常小的微孔聚合与非常小的微孔聚合




Crack propagation propagation (cleavage) (cleavage) in brittle materials materials occurs through through planar sectioning of the atomic bonds between the atoms at the crack tip.




4.2.7.6 Prevention / Mitigation 预防/缓解 a) For new new equipme equipment, nt, brittle brittle fracture fracture is is best best prevent prevented ed by using using material materialss specifically designed for low temperature operation including upset and autorefrigeration events. Materials with controlled chemical composition, special heat treatment and and impact test verification verification may be required. Refer Refer to UCS 66 in Section VIII of the ASME BPV Code. 低温设备选材合适冲击要求材料 b) Brittle fracture is an “event” driven damage damage mechanism. mechanism. For existing materials, where the right combination of stress, material toughness and flaw size govern the probability of the event, an engineering engineering study can be performed performed in accordance accordance with API 579-1/ASME FFS-1 , Section 3, Level 1 or 2. 脆裂为“事件”驱动的损伤机制(因素:应力, 韧性和裂纹尺寸)应用FFS-1适用性分析,评估设备完整性. c) Preventa Preventative tive measu measures res to minimize minimize the the potential potential for for brittle brittle fracture fracture in existing existing equipment are limited to controlling the operating conditions (pressure, temperature), minimizing pressure pressure at ambient temperatures temperatures during during startup and shutdown, and periodic inspection at high stress locations. 维持 IOW 操作参数, 周转期间启动,关断设备受压与温度控制与在高应力区的定期检查.


d) Some reduc reduction tion in the the likelihoo likelihood d of a brittle brittle fractu fracture re may be achieve achieved d by: 缓解行动有; 缓解行动有; 1. Perfor Performi ming ng a post post weld weld heat heat trea treatm tment ent (PWH (PWHT) T) on the the vesse vessell if it was not not originally done during manufacturing; or if the vessel has been weld repaired/modified while in service without the subsequent PWHT. 焊后热处理 2. Perfor Perform m a “war “warm” m” pre-st pre-stres ress s hydrot hydrotest est follo followed wed by a lowe lowerr temp tempera eratur ture e hydrotest to extend extend the Minimum Safe Operating Operating Temperature Temperature (MSOT) (MSOT) envelope. 周转期间水压试验/ 周转期间水压试验/温度控制. 温度控制.


4.2.7.7 Inspection and Monitoring 检验与监测 a) Inspectio Inspection n is not normal normally ly used used to mitiga mitigate te brittle brittle fractur fracture. e. 检验不能用来缓解脆性开裂 b) Susceptible vessels should be inspected for pre-existing flaws/defects. 易感容器的存在缺陷的监测


4.2.7.8 Related Mechanisms 相关机理 Temper embrittlement (see 4.2.3), strain age embrittlement (see 4.2.4), 885 oF (475oC) embrittlement (see4.2.5), titanium hydriding (see 5.1.3.2) and sigma embrittlement (see 4.2.6). 脆性破裂作为形态定义时,, 上述损坏机理, 脆性破裂作为形态定义时上述损坏机理, 破断形态可以归类为” 破断形态可以归类为”脆性破裂” 脆性破裂”

Temper embrittlement















Microvoid due to plastid yielding & ductile fracture (non creep type)


Microvoid due to plastid yielding & ductile fracture (non creep type)


Further reading: http://www.sut.ac.th/engineering/me http://www.sut.ac.th/eng ineering/metal/pdf/MechMe tal/pdf/MechMet/14_Brittle%2 t/14_Brittle%20fracture%2 0fracture%20and%20im 0and%20impact%20testin pact%20testing.pdf g.pdf http://lecture.civilengineer http://lecture.civ ilengineeringx.com/structura ingx.com/structural-analysis/structu l-analysis/structural-steel/bri ral-steel/brittle-fracture/ ttle-fracture/ http://www.keytometals.com/articles/art136.htm http://people.virginia.edu http://people .virginia.edu/~lz2n/mse209 /~lz2n/mse209/Chapter8.p /Chapter8.pdf df http://www.keytometals.com/page.asp http://www.keytometals.co m/page.aspx?ID=CheckArti x?ID=CheckArticle&site=kts&LN cle&site=kts&LN=CN&NM=136 =CN&NM=136 http://www.techtransfer.com/resources/w http://www.techtransfer.com /resources/wiki/entry/3645 iki/entry/3645//


Brittle Brit tle Fra Fractur cture e

低温现象: 低温现象:室温/ 室温/低于400 低于400oF, 影响材质:铁素体/ 铁素体/马氏体钢, 马氏体钢,  影响材质: 焊后热处理作为预防与缓解方法,,  焊后热处理作为预防与缓解方法周转期间设备处于低温状态时的受压控制(MSOT), (MSOT),  周转期间设备处于低温状态时的受压控制应用FFS-1合适性分析合适性分析,,评估带缺陷的设备可用性评估带缺陷的设备可用性,,  应用FFS-1 导致脆性开裂的因素有;; (1) 低韧性铁素体钢材, (2) 服务导致脆化,例如; 回火  导致脆性开裂的因素有脆化, 脆化,应变时效脆性,885oF脆化,钛氢化,西格玛的脆化. 

API571-Part3

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