Applied Mechanics Lab – MEC 424/AHA/MCM Rev. 01-2014
UNIVERSITI TEKNOLOGI MARA FAKULTI KEJURUTERAAN MEKANIKAL _____________ _______ _____________ ______________ _____________ _____________ ______________ _____________ _____________ ______________ _____________ ________ __
Program : Bachelor of Engineering (Hons) Mechanical (EM220/EM221) Course : Applied Mechanics Lab Code : MEC 424 Lecturer : MOHAMAD ZULFAZLI ARIEF BIN ABD LATIF Group : EMD4M13 _____________ _______ _____________ ______________ _____________ _____________ ______________ _____________ _____________ ______________ _____________ ________ __
MEC 424 - LABORATORY REPORT TITLE
No 1 2 3
:
The Jominy End-Quench Test
NAME
STUDENT ID
MOHAMAD RAHIMAN BIN MUSTAPHA
LABORATORY SESSION
:
06/04/2018 (DATE)
REPORT SUBMISSION
:
13/04/2018 (DATE)
SIGNATURE
2016218544
*By signing above you attest that you have contributed to this submission and confirm that all work you have contributed to this submission is your own work. work. Any suspicion of copying or plagiarism plagiarism in this work will result in an investigation investigation of academic msconduct and may result in a “0” on the work , work , an “F” in the course, or possibly more severe penalties .
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Applied Mechanics Lab – MEC 424/AHA/MCM Rev. 01-2014
Abstract The Jominy End Quench test is useful in determining the hardenability of a material. A sample, such as specimen given which is used in this experiment, is transformed entirely into a single solid phase through heating to a high temperature. It is then quenched by exposing one of its ends to a cooling source, such as water. The region of the sample that is put in contact with this cooling source drops in temperature more rapidly which limits growth in the material's grains. Other regions of the sample cool more slowly which allows for the grains in these areas to grow to greater sizes. The result of this is a single substance containing many different solid phases, each contributing differently to the hardness of the sample. Hardness readings are then taken along the length of the sample to establish the effects of changing temperature after heat treatment on the material's characteristics and behavior. In this experiment the Jominy End Quench test was performed on a specimen steel sample to investigate the effects of heat treatment followed by different rates of cooling.
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Applied Mechanics Lab – MEC 424/AHA/MCM Rev. 01-2014
Contents Abstract ........................................................................................................................................ 2 1.
List of Table .................................................. ........................................................................ 4
2.
List of the Figures ................................................... .............................................................. 5
3.
Introduction .................................................. ........................................................................ 6
4.
Objective of the Experiment ................................................................................................. 8
5.
Theoretical Background ................................................. ...................................................... 9
6.
Apparatus ............................................. ............................................................................... 13
7.
Experimental Procedure ................................................. .................................................... 14
8.
Result
9.
Discussion and Conclusion
10. Reference 11. Appendices
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Applied Mechanics Lab – MEC 424/AHA/MCM Rev. 01-2014
1. List of Table Table 1: The Data of the Hardness
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Applied Mechanics Lab – MEC 424/AHA/MCM Rev. 01-2014
2. List of the Figures Figure 1 : Schematic of Jominy end-quench test process. ......................................................................... 6 Figure 2 : Correlation of hardenability and continuous cooling information for eutectoid steel. ............. 7 Figure 3: The iron-iron carbide phase diagram. ........................................................................................ 9 Figure 4 : Continuous cooling transformation diagram for eutectoid diagram. ...................................... 10 Figure 5 : Continuous cooling transformation diagram for 4340 steels. ................................................. 11 Figure 6 : Jominy end Quench Machine .................................................................................................. 13 Figure 7 : Rockwell Hardeness Machine. ................................................................................................ 13 Figure 8 : Optical Microscope ................................................................................................................. 13 Figure 9 : Jominy end quench fixture. ..................................................................................................... 14
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Applied Mechanics Lab – MEC 424/AHA/MCM Rev. 01-2014
3. Introduction
In engineering field, the properties and behaviour of metals and alloys play a vital role especially during manufacturing and performance during their service life. The most common example of properties enhancement is heat treatment of metals and alloys. Such treatment modifies microstructure, producing a variety of mechanical properties that are important in manufacturing, such as improved formability and machinability.
The Jominy end quench test is used to measure the hardenability of a steel, which is a measure of the capacity of the steel to harden in depth under a given set of conditions. Information about the hardenability of steels is necessary to be able to select the appropriate combination of alloy steel and heat treatment to manufacture components of different size to minimize thermal stresses and distortion. The Jominy end quench test is the standard method for measuring the hardenability of steels. This describes the ability of the steel to be hardened in depth by quenching.Hardenability depends on the chemical composition of the steel and also be can affected by prior processing conditions, such as the austenitizing temperature. It is not only necessary to understand the basic information provided from the Jominy test, but also to appreciate how the information obtained can be used to understand the effects of alloying in steels and the steel microstructure.
Figure 1 : Schematic of Jominy end-qu ench test process.
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Applied Mechanics Lab – MEC 424/AHA/MCM Rev. 01-2014
Hardenability is the ability of a steel to partially or completely transform from austenite to some fraction of martensite at a given depth below the surface, when cooled under a given condition. For example, a steel of a high hardenability can transform to a high fraction of martensite to depths of several millimetres under relatively slow cooling, such as an oil quench, whereas a steel of low hardenability may only form a high fraction of martensite to a depth of less than a millimetre, even under rapid cooling such as a water quench. Hardenability therefore describes the capacity of the steel to ha rden in depth under a given set of conditions.
Steels with high hardenability are needed for large high strength components, such as large extruder screws for injection moulding of polymers, pistons for rock breakers, mine shaft supports, aircraft undercarriages, and also for small high precision components such as diecasting moulds, drills and presses for stamping coins. High hardenability allows slower quenches to be used (e.g. oil quench), which reduces the distortion and residual stress from thermal gradients. Steels with low hardenability may be used for smaller components, such as chisels and shears, or for surface hardened components such as gears. Hardenability can be measured using the Jominy end quench test.
Figure 2 : Correlation of hardenability and continuous cooling information for eutectoid steel.
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Applied Mechanics Lab – MEC 424/AHA/MCM Rev. 01-2014
4. Objective of the Experiment
To learn how to perform the Jominy end quench test.
To understand the relation between hardness to the cooling rate of the specimen after been heated (quenching) using the Jominy test method.
To understand microstructure changes to the cooling rate of the specimen after been heated (quenching) using the Jominy test method.
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Applied Mechanics Lab – MEC 424/AHA/MCM Rev. 01-2014
5. Theoretical Background
To understand heat treatment of steels requires an understanding of the Fe-C phase diagram shown in Figure 1. A steel with 0.76 wt%C is said to be a eutectoid steel. A steel with a carbon content less than 0.76 wt% is hypoeutectoid and greater than 0.76 wt% is hypereutectoid. The region marked austenite (γ) is face-centered-cubic and ferrite (α) is body-centered-cubic.
Figure 3: The iron-iron carbide phase diagram.
The microstructure, and hence the properties, of the alloy depends on its composition. If one very slowly cools a hypoeutectoid steel from a point in the austenite region, the final microstructure would contain proeutectoid ferrite (α) and pearlite pearlite (α + Fe3C). With a hypereutectoid steel, the proeutectoid phase would be cementite (Fe3C).
The size, type, and distribution of phases present can be altered by cooling at a rate faster than is required for thermodynamic equilibrium. Steels are often cooled so rapidly that metastable phases appear. One such phase is martensite, which is body-centeredtetragonal phase and which only occurs during very rapid cooling.
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Applied Mechanics Lab – MEC 424/AHA/MCM Rev. 01-2014
Much of the information on non-equilibrium distribution, size, and type of phases has been obtained from experiments. The results can be presented in a continuous cooling transformation diagram for eutectoid composition as shown in Figure 2. The final microstructure (martensite and/or pearlite) depends on the cooling rate. For pearlite formation, slower cooling causes coarse pearlite while fast cooling causes fine pearlite to form. Cooling rates faster than the critical cooling rate result in martensite.
Figure 4 : Continuous cooling transformation diagram for eutectoid d iagram.
Martensite causes hardness in steels. Unfortunately, hardness in steels also produces brittleness. The brittleness is usually associated with low impact energy and low toughness. To restore some of the toughness and impact properties, it is frequently necessary to “temper” the steels. This is accomplished by heating the steel up to a temperature between 500 and 1000 degrees F. Tempering removes some of the internal stresses and introduces recovery processes in the steel without a large decrease in hardness and strength. To obtain the desired mechanical properties it is necessary to cool steel from the proper temperature at the proper rates and temper them at the proper temperature and time.
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Applied Mechanics Lab – MEC 424/AHA/MCM Rev. 01-2014
In a practical sense it is not possible to heat-treat all parts of the specimen to the same level. The difference is due to the thickness for volume effect. Basically, when a part is quenched in water or some other media, the heat must be conducted out through the surface. This leads to a temperature gradient ∆T/∆y between the surface and the center of the part being heat-treated. The temperature gradient varies with time, being less steep at later times. Thus the temperature of the center lags in time behind the temperature of the surface. This means that cooling rate varies as a function of depth. The greater the depth, the slower the cooling rate. Different cooling rates can lead to a different hardness in the center than at the edge. The edge could transform to martensite and the center to pearlite.
The resulting microstructure also depends on the composition of the alloy. Figure 3 shows the continuous cooling transformation diagram for 4340 steel (0.40 wt%C, 1.85 wt%Ni, 0.80 wt%C, and 0.25 wt% Mo). The presence of alloying elements other than Carbon shift the pearlite (as well as the proeutectoid phase) and bainite formation to longer times, thus decreasing the critical cooling rate. In fact, one of the reasons for alloying elements is to facilitate the formation of martensite so that totally martensitic structures can develop in relatively thick cross sections. The ability of a steel alloy to develop martensite is related to a property called hardenability. It is a measure of the rate at which hardness drops off with distance into the interior of a specimen as a result of diminished martensitic content.
Figure 5 : Continuous cooling transformation diagram for 4340 steels.
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Applied Mechanics Lab – MEC 424/AHA/MCM Rev. 01-2014
The Jominy End-Quench Test
One standard procedure that is widely used to measure hardenability of steel is the Jominy endquench test. In this test water is sprayed on one end of a bar of steel while it is hot. This leads to a one dimensional heat transfer cooling. Except near the surface of the bar the temperature is controlled by that flow along the length of the bar. Moving axially inward from the quenched end of the bar, the temperature and the rate of change of temperature are changing. The temperature is higher and the rate is slower away from the quenched end. If hardness is measured as a function of distance from the end, a hardness profile can be obtained which applies to any part made from the same steel.
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Applied Mechanics Lab – MEC 424/AHA/MCM Rev. 01-2014
6. Apparatus
Apparatus
Function
To heat and drop the specimen.
Figure 6 : Jominy end Quench Machine
To observe the hardness of the specimen.
Figure 7 : Rockwell Hardeness Machine.
To observe the microstructures of specimen.
Figure 8 : Optical Microscope
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Applied Mechanics Lab – MEC 424/AHA/MCM Rev. 01-2014
7. Experimental Procedure
1. Preheat the furnace to 900 ̊C. 2. Place the Jominy specimen in the furnace and soak for one hour. 3. Turn the water on at the Jominy sink. Adjust the free water column to about 2.5 in. Swivel the baffle plate to block the water column so that there is no contact between water and the test specimen when the test specimen is initially placed on the fixture. 4. Remove the Jominy specimen from the furnace and place it in the fixture as shown in Figure 1. Swivel the baffle out of position so that the water impinges on the bottom of the specimen without wetting the sides of the specimen. Leave water running for about 15 minutes.
Figure 9 : Jominy end q uench fixture.
5. Remove the Jominy specimen from the fixture and grind a flat on the side of the specimen. 6. Take readings at an interval of 1mm up to 10mm by measuring the Rockwell C hardness. 7. Repeat the step 6 with the interval of 5 mm up to 50 mm and interval 0f 10 mm up to 100 mm. 8. Plot the data for Rockwell Hardness versus Distance from quenched end.
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