Industrial-Electronics-Lecture-Notes-07-Automatic-Welding.pdf

Industrial Electronics (2nd Sem 2013-2014)

3/17/2014

Fernando Victor V. de Vera, ECE, M.Tech

[email protected] [email protected] University of the East - Manila Campus College of Engineering Electronics Engineering Department

AUTOMATIC WELDING

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Weldi!  Weldi! is a fabrication or scultural rocess

t!at "oins materials# usuall$ metals or t!ermolastics# b$ causin% coalescence&  '!is is often done b$ meltin% t!e orieces and addin% a filler material to form a ool of molten material (t!e eld ool) t!at cools to become a stron% "oint# it! ressure sometimes used in con"unction it! !eat# or b$ itself# to roduce t!e eld& +fvictordevera ©2013

Ot"er #roce$$e$ %i&ilar to Weldi!  %olderi! 

* rocess in !ic! to or more metal items are "oined to%et!er to%et!er b$ meltin% meltin% and floin% a filler metal metal (solder) into t!e "oint# t!e filler metal !avin% a loer meltin% oint t!an t!e ad"oinin% metal

 'ra(i! 

a metal-"oinin% rocess !ereb$ a filler metal is !eated above meltin% oint and distributed distributed beteen to or more close-fittin% arts arts b$ caillar$ action& '!e filler metal is brou%!t sli%!tl$ above its meltin% (liuidus) temerature temerature !ile rotected b$ a suitable atmos!ere# usuall$ a flu,& It t!en flos over t!e base metal (non as ettin%) and is t!en cooled to "oin t!e orieces to%et!er& +fvictordevera ©2013

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Eer!) %o*rce$ for Weldi!  as flame  Electric arc  .aser  Electron

beam

 riction  ltrasound


Da!er$ Ivolved it" Weldi!  urns  Electric s!oc  ision dama%e  In!alation of oisonous %ases and fumes  E,osure

to intense ultraviolet radiation


Weldi! #roce$$e$  *rc  as  esistance  Ener%$

eam

 Solid State


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Arc Weldi!  ses a eldin% oer sul$

to create and maintain an electric arc beteen an electrode and t!e base material to melt metals at t!e eldin% oint&  oer source5 6 or *  Electrodes5 consumable or non-consumable  '!e eldin% re%ion is sometimes rotected b$ some t$e of inert or semi-inert %as# non as a shielding gas# and filler material is sometimes used as ell& +fvictordevera ©2013

#oer %*,,l)  ommon 

CON%TANT CU--ENT •



8eldin% oer Sul$5

9ost often used for manual eldin% rocesses suc! as %as tun%sten arc eldin% and s!ielded metal arc eldin%# because t!e$ maintain a relativel$ constant current even as t!e volta%e varies&

CON%TANT .OLTAGE •

9ost often used for automated eldin% rocesses suc! as %as metal arc eldin%# flu, cored arc eldin%# and submer%ed arc eldin%&


Arc Weldi! #oer %*,,l)  '!e

len%t! of t!e arc is directl$ related to t!e volta%e# and t!e amount of !eat inut is related to t!e current&


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Weldi! Electrode$  Electrode$ 

sed to conduct c urrent t!rou%! a oriece to fuse to ieces to%et!er&

 T),e$/ 

onsumable Electrodes



:on-onsumable


Weldi! Electrode$


Co$*&ale Weldi! Electrode$  ses

direct current and electrodes can be c!ar%ed eit!er be ositive or ne%ative&

 rocesses5 

S!ielded metal arc eldin%



as metal arc eldin%


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Co$*&ale Weldi! Electrode$  '!e ositivel$ c!ar%ed anode ill !ave a

%reater !eat concentration# so# c!an%in% t!e olarit$ of t!e electrode !as an imact on eld roerties& 

If t!e electrode is ositivel$ c!ar%ed# t!e base metal ill be !otter# increasin% eld enetration and eldin% seed&



* ne%ativel$ c!ar%ed electrode results in more s!allo elds& +fvictordevera ©2013

NoCo$*&ale Weldi! Electrode$  an use eit!er t$e of direct current# as

ell

as alternatin% current&  rocesses5 

as tun%sten arc eldin%


NoCo$*&ale Weldi! Electrode$  8it! Direct C*rret 5 

'!e electrode onl$ creates t!e arc and does not rovide filler material



ositivel$ c!ar%ed electrode causes s!allo elds#



:e%ativel$ c!ar%ed electrode maes deeer elds&


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NoCo$*&ale Weldi! Electrode$  8it! Alterati! C*rret 

esults in medium-enetration elds&

 6isadvanta%e5 

'!e arc must be re-i%nited after ever$ =ero crossin%&



se a suare ave attern instead of t!e normal sine ave# main% raid =ero crossin%s ossible and minimi=in% t!e effects of t!e roblem&


Arc Weldi! #roce$$e$  S!ielded  as

9etal *rc 8eldin% (S9*8)

9etal *rc 8eldin% (9*8)

 lu,-ored

*rc 8eldin% (*8)

 as 'un%sten *rc 8eldin% ('*8) 

lasma *rc 8eldin% (*8)

 Submer%ed

*rc 8eldin% (S*8)


%"ielded Metal Arc Weldi! %MAW  *lso

>manual metal arc eldin%? (99*) or >stic eldin%?&  Electric current is used to strie an arc beteen t!e base material and consumable electrode rod# !ic! is made of filler material (t$icall$ steel) and is covered it! a flu, t!at rotects t!e eld area from o,idation and contamination b$ roducin% carbon dio,ide (@2) %as durin% t!e eldin% rocess&  '!e electrode core itself acts as filler material# main% a s earate fi ller unnecessar$& +fvictordevera ©2013

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Ga$ Metal Arc Weldi! GMAW  *lso non as >metal i nert %as (9I)? eldin%  * semi-automatic or

automatic rocess t!at uses a continuous ire feed as an electrode and an inert or semi-inert %as mi,ture to rotect t!e eld from contamination&

 Since t!e electrode is

continuous# eldin% seeds are %reater for 9*8 t!an for S9*8&


4l*5Cored Arc Weldi! 4CAW  ses similar euiment but uses ire

consistin% of a steel electrode surroundin% a oder fill material&  '!is

cored ire is more e,ensive t!an t!e standard solid ire and can %enerate fumes and/or sla%# but it ermits even !i%!er eldin% seed and %reater metal enetration&


Ga$ T*!$te Arc Weldi! GTAW  *lso >tun%sten inert %as ('I)?

eldin%  * manual eldin% rocess t!at uses a nonconsumable tun%sten electrode# an inert or semi-inert %as mi,ture# and a searate filler material&  seful for eldin% t!in materials&  an be used on nearl$ all eldable metals# t!ou%! it is most often alied to stainless steel and li%!t metals& +fvictordevera ©2013

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#la$&a Arc Weldi! #AW  *lso uses a tun%sten electrode but uses lasma

%as to mae t!e arc&  '!e arc is more concentrated t!an t!e '*8 arc# main% transverse control more critical and t!us %enerall$ restrictin% t!e tec!niue to a mec!ani=ed rocess&  ecause of its stable current# t!e m et!od can be used on a ider ran%e of material t!icnesses t!an can t!e '*8 rocess and it is muc! faster&  It can be alied to all of t!e same materials as '*8 e,cet ma%nesium# and automated eldin% of stainless steel is one imortant alication of t!e rocess&  * variation of t!e rocess is plasma cutting# an efficient steel cuttin% rocess& +fvictordevera ©2013

%*&er!ed Arc Weldi! %AW *

!i%!-roductivit$ eldin% met!od in !ic! t!e arc is struc beneat! a coverin% la$er of flu,& '!is increases arc ualit$# since contaminants in t!e atmos!ere are bloced b$ t!e flu,&  '!e sla% t!at forms on t!e eld %enerall$ comes off b$ itself# and combined it! t!e use of a continuous ire feed# t!e eld deosition rate is !i%!&  8orin% conditions are muc! imroved over ot!er arc eldin% rocesses# since t!e flu, !ides t!e arc and almost no smoe is roduced& +fvictordevera ©2013

Ga$ Weldi!  '!e most common %as eldin% rocess is

oxyfuel welding # also non as >o,$acet$lene eldin%?&  It is one of

t!e oldest and most versatile eldin% rocesses# but in recent $ears it !as become less oular in industrial alications& It is still idel$ used for eldin% ies and tubes# as ell as reair or&


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Ga$ Weldi!  '!e euiment is relativel$ ine,ensive and

simle# %enerall$ emlo$in% t!e combustion of acet$lene in o,$%en to roduce a eldin% flame temerature o f about 3100 C&  '!e flame# since it is less concentrated t!an an electric arc# causes sloer eld coolin%# !ic! can lead to %reater residual stresses and eld distortion# t!ou%! it eases t!e eldin% of !i%! allo$ steels&  * similar rocess# %enerall$ called o,$fuel cuttin%# is used to cut metals& +fvictordevera ©2013

-e$i$tace Weldi!  esistance eldin% involves t!e %eneration of

!eat b$ assin% current t!rou%! t!e resistance caused b$ t!e contact beteen to or mo re metal surfaces&  Small ools of molten metal are formed at t!e eld area as !i%! current (1000D100#000 *) is assed t!rou%! t!e metal&  Efficient and cause little ollution# but t!eir alications are some!at limited and t!e euiment cost can be !i%!& +fvictordevera ©2013

-e$i$tace Weldi!  Sot

8eldin%

 S!ot

8eldin%

 Seam

8eldin%

 @t!ers5 

utt



las!



ro"ection



set +fvictordevera ©2013

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%,ot Weldi!  Sot eldin% is a

oular resistance eldin% met!od used to "oin overlain% metal s!eets of u to 3 mm t!ic&  'o electrodes are simultaneousl$ used to clam t!e metal s!eets to%et!er and to ass current t!rou%! t!e s!eets&  *dvanta%es5     

efficient ener%$ use limited oriece deformation !i%! roduction rates eas$ automation no reuired filler materials&

 6isadvanta%e5 

8eld stren%t! is si%nificantl$ loer t!an it! ot!er eldin% met!ods& +fvictordevera ©2013

%"ot ad %ea& Weldi!  %6OT Weldi! 

an be used to sot eld stainless steel

 %EAM Weldi! 

elies on to electrodes to al$ ressure and current to "oin metal s!eets&



ses !eel-s!aed electrodes t!at roll alon% and often feed t!e oriece# main% it ossible to mae lon% continuous elds (li e in bevera%e cans)& +fvictordevera ©2013

Eer!) 'ea& Weldi!  MET6OD%/ 

.*SE eam 8eldin% - emlo$s a !i%!l$ focused laser beam&



Electron eam 8eldin% - done in a vacuum&

 '!e

to rocesses are uite similar# differin% most notabl$ in t!eir source of oer&


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La$er ad Electro 'ea& Weldi! C6A-ACTE-I%TIC%/  E,tremel$ fast  Easil$ automated  i%!l$ roductive&  er$ !i%! ener%$ densit$  

9aes dee eld enetration ossible 9inimi=es t!e si=e of t!e eld area&

DI%AD.ANTAGE%/  er$ !i%! euiment costs  Suscetibilit$ to t!ermal cracin% +fvictordevera ©2013

%olid %tate Weldi!  '!e materials bein%

"oined are not melted&  T7#E%5 

ltrasonic 8eldin%



old



E,losion 8eldin%



6iffusion ondin%



riction 8eldin%



E,ot!ermic 8eldin%



i%! freuenc$ eldin%



ot ressure eldin%



Induction eldin%



oll eldin%

 

Electroma%netic ulse eldin% o-E,trusion


Ultra$oic Weldi!  sed to connect t!in s!eets or ires made of metal or

t!ermolastic b$ vibratin% t!em at !i%! freuenc$ and under !i%! ressure&  '!e euiment and met!ods involved are similar to t!at of resistance eldin%# but instead of electric current# vibration rovides ener%$ inut&  8!en eldin% lastics# t!e materials s!ould !ave similar meltin% temeratures# and t!e vibrations are introduced verticall$&  ltrasonic eldin% is commonl$ used for main% electrical connections out of aluminum or coer# and it is also a ver$ common ol$mer eldin% rocess& +fvictordevera ©2013

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E5,lo$io Weldi!  Involves t!e "oinin% of materials b$ us!in%

t!em to%et!er under e,tremel$ !i%! ressure&  '!e ener%$ from t!e imact lastici=es t!e materials# formin% a eld# even t!ou%! onl$ a limited amount of !eat is %enerated&  '!e rocess is commonl$ used for eldin% dissimilar materials# suc! as t!e eldin% of aluminum it! steel in s!i !ulls or comound lates& +fvictordevera ©2013

Geo&etr) of Weld 8oit$ 'A%IC T7#E%/

*& utt "oint & orner "oint & '-"oint 6& .a "oint E& Ed%e "oint


Geo&etr) of Weld 8oit$  ommon 8eldin% Foint

'$es5 1& Suare butt "oint 2&  butt "oint 3& .a "oint 4& '-"oint


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9*alit) of Weld$  actors

influence t!e stren%t! of elds and t!e material around t!em 

8eldin% met!od



*mount and concentration of ener%$ inut



8eldabilit$ of t!e base material# fill er material# and flu, material



'!e desi%n of t!e "oint



Interactions beteen all t!ese factors&


A*to&atic Weldi! Seuence of @eration in main% a 8eld5  Suee=e  8eld  old  elease  Standb$


%:*ee(e Iterval  '!e eldin% electrodes come forard to en%a%e

t!e metal&  '!e$ are alloed to ress a%ainst t!e surfaces for

a s!ort time before t!e eldin% current starts&  '!is

is done to allo t!e electrodes to conform to t!e curvature of t!e surfaces and to mae erfect electrical contact&

 suall$ lasts about 1sec# but

can be ad"usted b$

t!e oerator& +fvictordevera ©2013

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Weld Iterval  '!e

eldin% transformer is ener%i=ed&

 urrent

flos don from t!e oer source toards t!e electrode and t!rou%! t!e metalto-metal contact# t!ereb$ creatin% a eld&

 suall$ taes about 2-10 secs lon%&


Weld Iterval

 '!e

eldin% current is turned on and off in s!ort bursts# called ulsations&  SI:'E*.S5  6EAT ; '!e ortion of t!e eld in !ic! t!e

current is floin%&  COOL ; '!e ortion !ere t!e current is absent& +fvictordevera ©2013

.ariale$ t"at Affect t"e 9*alit) of Weld$ 1& ulsations er eld interval 2& $cles er eat subinterval 3& $cles er ool subinterval 4& onduction *n%le


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6old Iterval  Electrode ressure is maintained on t!e metal

surfaces# but t!e eldin% current is turned off&  '!is is done to allo

fused metal of t!e eld to !arden before t!e mec!anical force e,erted b$ t!e electrodes is removed&

 .asts about 1 sec&


-elea$e ad %tad) Iterval$  -ELEA%E 

'!e eldin% electrodes are retracted&

 %TAND'7 

8aits for t!e ne,t c$cle to commence&


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Industrial-Electronics-Lecture-Notes-07-Automatic-Welding.pdf

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