Zul Coldwork

8/17/2019 Zul Coldwork

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Whe the pro%essi ( temper"ture of the me%h" i%"& #eform"tio of stee& is "1o0e the re%r'st"&&i)"tiotemper"ture, the pro%ess is terme# "s hot !or$i (5 other!ise, it is %o !or$i (*

>or hot !or$i ( pro%esses, &"r(e #eform"tio %" 1e su%%essi0e&' repe"te#, "s the met"& rem"i s soft" # #u%ti&e* The h"r# ess of the m"teri"& %" ot 1e %o tro&&e# "fter hot ro&&i ( " # it is " fu %tio of%hemi%"& %ompositio " # the r"te of %oo&i ( "fter ro&&i (* The h"r# ess is (e er"&&' &o!er th" th"tof %o ro&&i ( " # the re9uire# #eform"tio e er(' is &esser "s !e&&* =o!e0er most met"& !i&&experie %e some surf"%e oxi#"tio resu&ti ( i m"teri"& &oss " # poor fi "& surf"%e fi ish*

Co !or$i ( pro%esses "&&o! #esir"1&e met"& 9u"&ities th"t %" ot 1e o1t"i e# 1' hot !or$i (, su%h"s e&imi "ti ( errors "tte #i ( shri $"(e* As su%h, " mu%h more %omp"%t " # hi(her #ime sio "&"%%ur"%' met"& %" 1e o1t"i e# !ith %o !or$i (* >urthermore, the fi "& pro#u%ts h"0e " smoothersurf"%e ?1etter surf"%e fi ish@ th" those of hot !or$i ( " # the stre (th, h"r# ess "s !e&& "s thee&"sti% &imit "re i %re"se#* =o!e0er, the #u%ti&it' of the met"& #e%re"ses #ue to str"i h"r#e i ( thusm"$i ( the met"& more 1ritt&e* As su%h, the met"& must 1e he"te# from time to time ?" e"&e#@ #uri (the ro&&i ( oper"tio to remo0e the u #esir"1&e effe%ts of %o !or$i ( " # to i %re"se the !or$"1i&it'of the met"&*;

=ere "re / 1e efits of %o !or$i ( of stee&s th"t m"$e " #iffere %e to 'our m"%hi i ( oper"tio s:

Increa ed Strengt!

“It is !i#e&' $ o! th"t %o !or$i ( pressure %h" (es i the properties of the met"&* Whe " 1"r of%o ro&&e# stee& %o #r"!i ( !or$ throu(h the mo, " si( ifi%" t i %re"se i 'ie " # te si&estre (th is o1t"i e#* At the s"me time, the re#u%tio i "re" " # per%e t e&o ("tio #e%re"se#* The(r"ph 1e&o! sho!s the effe%t of %o #r"!i ( o the te si&e properties of 2 i %h #i"meter stee& 1"rrou #*

Figure ": #ec!anical $ro%ertie & C!ange re ulting fro' & Cold (ork

There "re t!o import" t &esso s i this (r"ph: 2@ As stre (th properties i %re"se, #u%ti&it' me"sures#e%re"se5 6@ Bp to "1out 2/4 %o re#u%tio , 'ie stre (th i %re"ses "t " mu%h (re"ter r"te th"

te si&e stre (th* The first /4 of %o !or$ resu&ts i the (re"test i %re"se i stre (th* ;


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I'%ro)ed Surface Fini !

=ot ro&&e# stee& 1"rs fi ish "t hi(h temper"tures, " # so the surf"%e h"s " rou(h h"r# s%"&e %o sists of0"rious iro oxi#es* This s%"&e is h"r# " # "1r"si0e %o sisti ( of 6 3 23.3 Di er to&er" %es %" 1e he 1' 'oure9uipme t !he proper&' si)e# 1"r (oi ( i to the m"%hi e* Simi&"r&', the str"i(ht h"ir 1etter resu&t i&ess ru out " # "&&o! hi(her spee#s i pro#u%tio * ;

T!eor+

“Co !or$i ( is the p&"sti% #eform"tio sh"pi ( pro%ess of met"&s !hi%h is performe# 1e&o!re%r'st"&&i)"tio temper"ture* Bsu"&&', re%r'st"&&i)"tio temper"ture is -34 of me&ti ( poi ttemper"ture ?TR 3*-3xTH@* A#0" t"(es "re5 o oxi#es o the surf"%e "fter oper"tio , o

h'#ro(e em1ritt&eme t, &o!er %osts for pro%ess " # e9uipme t, h"r#e i ( from str"i *Dis"#0" t"(es "re5 stress i the 1o#' therefore most&' it ee#s re%o0er' pro%ess, mu%h more&o"# po!er e%essit' for p&"sti% #eform"tio , it 1e%omes 1ritt&e #epe #s to %o !or$i (

per%e t"(e*

+efore !or$ h"r#e i (, the &"tti%e of the m"teri"& exhi1its " re(u&"r, e"r&' #efe%t free p"tter?"&most o #is&o%"tio s@* The #efe%t free &"tti%e %" 1e %re"te# or restore# "t " ' time 1'" e"&i (* As the m"teri"& is !or$ h"r#e e# it 1e%omes i %re"si (&' s"tur"te# !ith e!#is&o%"tio s, " # more #is&o%"tio s "re pre0e te# from u%&e"ti ( ?" resist" %e to #is&o%"tioform"tio #e0e&ops@* This resist" %e to #is&o%"tio form"tio m" ifests itse&f "s " resist" %eto p&"sti% #eform"tio 5 he %e, the o1ser0e# stre (the i (*

I met"&&i% %r'st"&s, irre0ersi1&e #eform"tio is usu"&&' %"rrie# out o " mi%ros%opi% s%"&e 1'#efe%ts %"&&e# #is&o%"tio s, !hi%h "re %re"te# 1' f&u%tu"tio s i &o%"& stress fies !ithi the


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m"teri"& %u&mi "ti ( i " &"tti%e re"rr" (eme t "s the #is&o%"tio s prop"("te throu(h the&"tti%e* At orm"& temper"tures the #is&o%"tio s "re ot " ihi&"te# 1' " e"&i (* I ste"#, the#is&o%"tio s "%%umu&"te, i ter"%t !ith o e " other, " # ser0e "s pi i ( poi ts or o1st"%&esth"t si( ifi%" t&' impe#e their motio * This &e"#s to " i %re"se i the 'ie stre (th of them"teri"& " # " su1se9ue t #e%re"se i #u%ti&it'*

Su%h #eform"tio i %re"ses the %o %e tr"tio of #is&o%"tio s !hi%h m"' su1se9ue t&' form&o! " (&e (r"i 1ou #"ries surrou #i ( su1 (r"i s* Co !or$i ( (e er"&&' resu&ts i hi(her 'ie stre (th "s " resu&t of the i %re"se# um1er of #is&o%"tio s " # the ="&&


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Figure 1: Ro&&i (


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Figure 5: i%$erMs Test H"%hi e

$rocedure

2* Ro&&i ( of three pie%es of %opper i or#er to re#u%e thi%$ ess 1' the fo&&o!i ( per%e t:i* 234ii* .34iii* /34

6* The ro&&e# s"mp&e is %ut i to / pie%es*.* >or e"%h pie%es :

I* Keep o e ro&&e# pie%eII* A e"& o e pie%e "t 6333C for .3 mi utesIII* A e"& o e pie%e "t .33 3C for .3 mi utesI * A e"& o e pie%e "t 833 3C for .3 mi utes

-* The h"r# ess testi ( is me"sure# for e"%h of the "1o0e s"mp&e "fter ro&&i ( or" e"&i (*

/* The s"mp&e is o1ser0e usi ( mi%ros%ope*8* Re%r'st"&&i)"tio temper"ture is #etermi e#*

OB6ECTI-E

• To #o %o !or$i ( o %opper " # o1ser0e " ' %h" (es i mi%rostru%ture• To " e"& the %o !or$e# met"& " # fi # out %r'st"&&i)"tio temper"ture*

RESULTS AND DISCUSSION


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Condition Thickness, % D1 D2 Hardness, HVUntreated Unrolled 52.8 45.7 764.0

10 40.0 2 .1 155!.0

!0 !5.4 2!.8 2116.0 50 !!.8 !2.2 1702.0

200 "C Unrolled 108.8 108.6 157.0 10 108.2 114.2 150.0 !0 10 .0 102.1 166.0

50 .2 87.4 21!.0!00 "C Unrolled 102.5 105.4 172.0

10 8.! 8.2 1 2.0 !0 7. 6.2 1 7.0

50 87.8 88.0 240.0600 "C Unrolled 114.4 106. 151.0

10 111.8 107.8 154.0 !0 10 . 10 .1 155.0

50 108.5 102.4 167.0

0 10 20 30 40 50 600

500

1000

1500

2000

2500

Hardness against Cold Working

Untreated

200300600

Cold Working, %

Hardness, HV


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7ra%! 1 : Gr"ph of ="r# ess "("i st Co Wor$i (

#icro tructure of co%%er at different te'%erature:

2* B tre"te#

B ro&&e# 234

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6* At 633 3C


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B ro&&e# 234

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.* At .33 3C


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B ro&&e# 234

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-* At 833 3C


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B ro&&e# 234

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DISCUSSION:

There "re umerous errors th"t "ffe%t our resu&ts me" i (fu&&':


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2* The pre%isio or #ime sio of the %opper "s !e %ut it !"s ot up to &e0e&, !hi%h me" s,the si)e of the %opper "re u e0e *

6*

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