stainless steel making

8/13/2019 Stainless Steel Making

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STAINLESS STEEL MAKING

Harry Brearley of Sheffield

Thomasfirth & sons and John & Co


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B#2$s &R#%$s


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IntroductionIn 113 Harry Brearley of Sheffield

de'elo(ed )hat is )idely re*arded as the first+r,st less$ or stainless steel a (rod,-t thatre'ol,tionised the metall,r*y ind,stry and.e-ame a maor -om(onent of the modern )orld

He .e*an his -areer in the steel ind,stry at thea*e of t)el'e as a la.o,rer in a lo-al steel )ors


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Steel -ontain not less than 1012 Cr )ith or )itho,talloyin* element!i4 Mo4 C,4 S4 Ti4 !.4 !4et-5

SS are *enerally -hosen )here -orrosion and o6idationresistan-e is im(ortant"o) S7#

In .esides 4 often ha'e *ood -ree( stren*th as -ross sli(of s-re) dislo-ation is diffi-,lt

Cr forms a (assi'e film on steel s,rfa-e Corrosion

resistan-e is im(arted .y the formation of a(assi'ation layer -hara-teri8ed .y9

i5 Insol,.le -hromi,m o6ide film on the s,rfa-e of the metal Cr2:35

ii5 ;e'elo(s )hen e6(osed to o6y*en and im(er'io,s to )ater and air

iii5 S,s-e(ti.le to sensiti8ation4 (ittin*4 -re'i-e -orrosion and a-idi-

en'ironmentsi'5


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Stainless steels may -lassified as

AISI -lasses for SS9

200 series ? Cr4 !i4Mn300 series ? Cr4 !i !on Ma*neti-

>00 series ? Cr only

@00 series ? lo) Cr 12

00 series ?


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eneral 0 to @0 (er-ent that of (lain-ar.on steel

Melting Temperature

%01@>0 DC

Martensiti-9 1>001@30 DC

7erriti-9 1>001@30 DC

A,steniti-9 13E01>@0 DC

Coeicient o ThermalE!pansion

reater -oeffi-ient than(lain-ar.on steels

"igh Strength

#6hi.it hi*h stren*th atroom and ele'atedtem(erat,res

Surace #reparation

S,rfa-e films m,st .eremo'ed (rior to )eldin*

Spot Spacing

"ess sh,ntin* is o.ser'edthan (lain-ar.on steels


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#roperties o Stainless Steel

Electrical Resistivity

Thermal Conductivity

Melting Temperature

%01@>0 DC

Martensiti-9 1>001@30 DC

7erriti-9 1>001@30 DCA,steniti-9 13E01>@0 D

Coeicient o Thermal E!pansion

"igh Strength

Surace #reparation

Spot Spacing


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:6y*en lan-in* of stainless steel .ath forde-ar.,ri8ation )as first introd,-ed in 13ori*inally it

)as meant to remo'e -ar.on .elo) the reF,ired le'el)itho,t re*ard to o6idation of -hromi,m

Before 1E04The maority of SS )ere made in #A7

"ater4 SS are (rod,-in* .y #A7A:; /=:;

A((li-ation 9 2005 Chemi-al ind,stry4 sanitary fittin* & ho,sehold

>005 Ho,se hold4 .lades4 ni'es&

trans(ortation @005 C,tlery 4s,r*i-al instr,ments and hi*h

F,ality .all .earin* 4n,-lear (lants4 shi(s & steelt,r.ine .lades


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#hysicochemical principle

#llin*ham ;ia*ram


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>/3Cr Go2 ? 2/3 Cr2:3

2CG:2 ?2C:

A.o'e the eF,ation are in eF,ili.ri,m at 1220 C

3C:G2Cr ? Cr2:3G3C ?0Minim,m reF,ired tem(erat,re is m,-h a.o'e

than 1220 C 1 atm

thermodynami- & ineti-s so 1%00 C not 1220C


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Limitation o classical process

1 A hi*h of SS s-ra( -ant .e ,sed in-har*e

2 :nly "C 7erro-hrome )hi-h is F,ite-ostly -an .e ,sed for ad,stin* the

finishin* -om(osition

3 At the tem(erat,re of 1%00 C anda.o'e dama*e to f,rna-e refra-tory linin*

is se'ere>A -om(lete heat taes a.o,t % ho,rs

from -har*in* to finishin* this restri-ts(rod,-ti'ity of the f,rna-e


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Modern technology

To -arry the de-ar.,ri8ation at lo)tem(erat,re )itho,t o6idi8ation of -hromi,m

Th,s a te-hnolo*y )hi-h -an ,se hi*h

-ar.on ferro -hrome and to de-ar.,ri8e the.ath at sele-ti'ely lo)er tem(erat,res )o,ld.e reF,ired

"o) (rod,-tion -ost

Red,-tion in (ress,re of C: -an .ea-hie'ed either .y 'a-,,m or .y ,sin* ami6t,re of ArG:2


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In a-t,al (ra-ti-e 4red,-tion of


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Argon *!ygen 3ecar4uri5ation


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S&etch o A*3


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Molten -har*e from ar- or ind,-tion f,rna-eis transferred to this 'essel and .lo)n )ith Ar o6y*en mi6t,re

In sta*e 1 :6y*en to ar*on ratio is 391 )hen-ar.on is red,-ed to 30

In sta*e 2 the ratio red,-ed to 291 .ath .lo)nto a.o,t 00012 -ar.on

In sta*e 3 a 192 .lo) red,-e the -ar.on to aslo) as 002

Maor -han*e in .lo)in* (ra-ti-e has .eendire-t s,.stit,tion of nitro*en for ar*onthro,*ho,t sta*e 1


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Thermodynamics o reaction in A*3

"ie iron4 Cr is -a(a.le of e6hi.itin* a 'aria.leCr2G/Cr3G ratio in sla*4 de(endin* on the o6y*en(otential and .asi-ity

In red,-in* sla* 4 Cr: is dominant )hereas in

o6idi8in* 4 Cr2:3 is the maor s(e-ies ie let ,s-onsidered as Cr2:3

Cr2:35 G > C ? >KC:L G3Cr

7 7 C C M l Hil d


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7or 7e Cr C Melt Hilty and a'eney

7or 7e Cr!i C Melt Hilty and a'eney

Here


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Nhen -ar.on has .een remo'ed to ne-essary le'el4the .ath is red,-ed .y 7eSi to re-o'er the Cr from sla*

The heat is finished .y deo6idation .y 7eSi additionit also red,-es .a- )hate'er -hromi,m is in sla* atendE5

Alon* )ith 7eSi4 lime is added to (rod,-e a sla* Sla*formation and sla* metal rea-tion is fa-ilitated .y ar*onstir ,sed thro,*ho,t this (eriod Sla* )as not remo'ed,ntil -hromi,m )as )on .a- in .ath

It is also effe-ti'e in o.tainin* *ood s,l(h,r remo'al,sin* ar*on stirrin* at end

so far -har*e material )as OOOO


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3irect stainless steel ma&ing

Nhere s-ra( and ferro alloy are e6(ensi'e orare not a'aila.le 4alternati'e (ro-ess ro,teha'e .een de'elo(ed that ,se -hromi,m orealon* )ith hot metal as -har*e

In Ja(an se'eral s,-h installation are in ,se 4the most )ell no)n of )hi-h is that

ANASAI ST##" C:R


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SR2KC8 process o direct SS ma&ing
http://var/www/apps/conversion/tmp/scratch_3/Outokumpu%20Tornio%20Works%20-%20From%20Chrome%20Ore%20to%20Stainless%20Steel.mp4http://var/www/apps/conversion/tmp/scratch_3/Outokumpu%20Tornio%20Works%20-%20From%20Chrome%20Ore%20to%20Stainless%20Steel.mp4


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Nitrogen pro4lem in stainless steel

!itro*en is no)n for a*es to -a,se strain.rittleness in steel

That is the reason )hy it )as e(t .are

minim,m for most steel its -reate serio,s(ro.lem in deformation d,rin* rollin*

It$s a interstitial element and strain ironlatti-e This )as the reason )hy .asi- Bessemer

steel )ere not (referred for many a((li-ation

Ar-elor Mittal
http://var/www/apps/conversion/tmp/scratch_3/Stainless%20Steel%20Production%20Process%20-%20ArcelorMittal%20Ch%C3%A2telet%20Site.mp4http://var/www/apps/conversion/tmp/scratch_3/Stainless%20Steel%20Production%20Process%20-%20ArcelorMittal%20Ch%C3%A2telet%20Site.mp4


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Conclusion

15 SS are )idely (rod,-ed .y #A7QA:; ro,te25 In A:; 4 Ar is ,sed to dil,te the other *ases or

red,-e the (artial (ress,re of C:

35 Hi*h tem(erat,re (referred to o6idi8e only

Car.on .,t not a -hromi,m

>5 7eSi added to re-o'er the o6idi8ed -hromi,mfrom sla* and ill the molten .ath

@5 se of "C 7eCr and =:; are e6(ensi'e(ro-ess

5 Some time !itro*en is re(la-e for Ar and !i-elas )ell

stainless steel making

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