U . S.

Department of Commerce Research Paper RP1878

National Bureau of Standards Volume 40, April 1948

Part of the Journal of Research of the National BurEau of Sta ndards

Stabilization of Austenitic Stainless Steel

By Samuel J. Rosenberg and John H. Darr
A stu dy was m a de of t he resistance to in tergra nui a r atta ck of 23 18 % Cr- 10 % 1\i
a ustenitic co rros ion-res istin g steels in 12 different ini t ial co ndi t io ns. Suscept ibili ty to
intergranul a r attack was determin ed a fter seven se nsit izin g t rcat me nLs; foll owed b y exp os ure
for a m ax imum of 1.4 d ays in a boilin g a cidified copper s ulfate sol ut io n.
It ,,as fo und t hat max imum s usce pt ibili ty to in tergran ula r at tack was de velop ed by
se nsit iz ing e ither 8 o r 21 d a~' s at ' ,020 F. Th e straigh t ca rb on a uste n itic sLeels were quite
v ulner ab le to attack , alt ho ug h dec rcase in ca rbon co n ten t dec reased the deg ree of v uln e r-
ab ili ty. Th e eolum bium - a nd t ita ni u m-t reate d steels we re sa t isfactor ily resis lan t to attac k
provid ed the Cbl C or Ti l C rat ios we re s u.tri ciently hi g h. These !"atiOH va ri ed , dep e ndin g on
the initial co ndi t ion of the steel. Th e carbon con te nt of the t reated steels h a d no influ e nce
upon t he res istance to in te rg ra nu la r attack , t he p re do min at ing fa cto r bein g lhe Cb/C or
T il C r a Li o.

1. Introduction cally, th is type of corros ion is particularly pro-

nounced in some 18- 8 st eels tha t have been sub-
An undes irable charact eri s ti c of th e au stenitic jected t o mod erately elev ated temperatures (700
s tainless steels is th eir susceptibility to inter- to 1,400 F ) and are eith er imultaneou sly or
. gran ular em bri l tlement after exposure to moder - subsequ entl y subj ec ted to corrosive conditions.
a t ely eleva ted t emperatures. This susceptibility Exposlll"e to th ese elevated t emp erature causes
to embrittlem ent may be decreased or eliminated, the precipitation of what are generally conceded
i. e., th e s teels may be stabilized against inter - to be chromium carb ides a t th e grain boundaries,
granular embri ttlem ent, by the addition of and s teels having such carbide precipitation have
titanium or columbium , usually in conjunction been found to be more or l ess s usceptible to intel"-
with a stabilizing heiLt treatm ent. granular corrosion, whereas steels th a t do not
A diversity of opinion as to the relative amounts exhibit this structure are generally immune.
of t itanium or columbium necessary for effective Annealed 18..:.8 stainless st eel (qu enched from
s tabilization , the injurious efrect of carbon con- t empera tures in the neighborhood of 1,800 to
tent, and the necessity for stabilizing h eat treat - 2,000 F ) th eoretically cons ists of m eta stable
m ents, led the Bureau of Aeronautics, Navy austenite, . in this case a s up ersaturated solid
D epartment, to r equ es t the National Bureau of solution of carbon or of cluomiuffi carbide in
S tandard s to und ertake a study of fa ctors affec ting chromium-nickel austenite. U pon r eheating t o
the stabilization of th e 18- 8 typ e of st eels. This mod erately eleva ted t emperatures, chromium car-
p aper summarizes the results of su ch an inves~ bide (Cr4 C) precipitates a t the grain boundaries.
t igation. One school of thought believes that this precipita-
tion reduces the cluomium content of the metal
II. Theory of Sensitization and Stabiliza- near the grain boundaries to a level below that
tion necessary to resist corrosion. This appears to be
the most prevalent view. Others believe that
Intergranular embrittlemen t (or corrosion- internal strains resulting from the precipitation
the t erms are usually used synonomou sly) may of carbides, and from the formation of alpha iron
be considered as a disease of 18- 8 st eels, al thou gh from the metastable austenite, are the cause of
it is not p eculiar to the e st eels alon e. Specifi- intergranular corrosion. Still anoth er belief is

Austenitic Stainless Steel 321

that the electrolytic effect resulting from a differ- chromium-nickel austenite than is the chromium
ence in potential between grains and grain bound- carbid e. . Thc two elements mos t frequ en tly used
aries is responsible. Regardless of the under- are titanium and columbium [6, 7] . It is known
lying theory, however, it is generally agreed that that these elem ents are more strongly carbide
the presence of chromium carbides distributed in forming than is chromium , and evidence is avail-
the form of a thin, nearly continuous network at able that the titanium and columbium carbides
thc grain boundari es is an indication of material are considerably less soluble in 18- 8 austenite
that is susceptible to intergranulal' corrosion. The than is chromium carbide. Theoretically, if th e
larger isolated carbides that result after sufficient carbon of 18- 8 stainless steel is fixed by either of
time at temperature has been allowed from coa- these stabilizing elem ents, that is, precipitated as
lescence of th e precipitated carbides and for re- TiC or CbC, no chromium carbide would pre-
plenishment by diffusion of chromium in the de- cipitate at the grain boundaries upon subsequent
pleted areas do not appear to be associated with reheating to sensitizing temperatures, and the
intergranular corrosion. steel thereafter would exhibit no intercrystalline
The earliest efforts to prevent intergranular embrittlement upon exposure to a corroding
embrit tlement were directed toward the manu- medium.
facture of 18- 8 with low carbon conten t on the Th e atomic weight of carbon is 12.01 , and that
theory that precipitation of chromium carbide of titanium is 49.90, and since titanium forms a
would thereby be minimized or even eliminated carbide corresponding to TiC, it is n ecessary,
[1, 2, 3].I It was also suggested that a treatment theoretically, to have about four times as much
at about 1,600 F resulted in a decreased sus- titanium as carbon in order to fix all the carbon as
ceptibility to intergranular corrosion upon sub- titanium carbide. Columbium has an atomic
sequ ent exposure at lower temperatures. This weight of 92 .91 , and as columbium forms a carbide
stabilizing (sometimes termed desensitizing) corresponding to CbC, the th eoretical minimum
treatment was presumed to precipitate sufficient amount of columbium that must be added to fix
chromium carbid es as coalesccd particles, and also the carbon is slightly less than eight times the
to p ermit diffusion of chromium, so that th e amount of carbon.
amount of carbon that would b e available to Stabilization consists in reheating the Cb- or
precipitate as fine chromium carbides at lower Ti-tl'eated steels wi thin t he temperature range
(sensitizing) temperatures would be negligible. 1,550 to 1,800 F , u sually at about 1,600 F .
It was also rcported that decreasing the aus- At these temperatures, t he precipitation of titan-
tenitic grain size diminished the severity of inter- ium and columbium carbides within the austenitic
granular attack [4] by providing extra grain grains is facilitated . Th e slight amount of carbon
boundary area for precipitation of carbides; that r emaining in solid solution after this tr eatment is
cold rolled matcrial was more r esistant to inter- (theoretically) insufficient to cause any dele terious
granular attack [3] because of the availability of effects (in the form of Cr 4C precipitated at the
numerous slip planes for the precipitation of grain boundaries) upon subsequent reheating to
carbides upon subsequent h eating ; and that the sensitizing temperatures.
addition of elements that caused the formation
of delta ferrite was also beneficial [5] in that, III. Materials
because of t h e lower solubility for carbides, Most of the steels used in this investigation were
precipitation occurred in the areas of delta ferrite. experimental melts, although a few commercial
The most commonly used m ethod of preventing steels were included . The experimental steels
intergranular corrosion in 18- 8 consists in adding were melted in an induction furnace and poured
a strongly carbide-forming element to the steel. into 3-in. square big end up tapered molds
The function of this elem ent is t o combine with equipped with hot tops. Each experimental heat
the carbon, thus allowing the chromium to r emain weighed about 75 pounds, and all were ma de in t he
in solid solution in th e austenite. To be effective foundry of the Naval R esearch Laboratory. The
this alloy carbide should be less soluble in th e ingots were shaped on all four sides as much as
1 Figures in brackets indicate the literat ure references at the en d of this
necessary to produce clean surfaces, following
paper. which they were hot forged to slabs about 3 in.

322 Journal of Research

 wide by 1 in. thi ck. Some of these ingots were insoluble nitrogen, this as umption appeared Lo be
forged at the Rustles Iron and Steel Division, quite plausible. The revised percentage of
American Rolling Mill Co. , Baltimore, Md . ; all titanium and columbium and the revised r atios of
others were forged at the Naval Research Labora- TilC and CblC were calculated after allowing for
I t ory. The slabs were surface ground on four sides the amounts of titanium a nd columbium combined
and rolled into O.050-in. strip at the American with the acid insoluble nitrogen and are included
Rolling Mill Co ., Middletown, Ohio, the schedule in table 1.
of operations being a,s follows :
IV. Procedure
(1) Hot roll at 2,000 to 2,200 F to 0.125 in.
and straighten.
Specimens 3 in. long by %in. wide and 0.050 in.
(2) Anneal 6 minutes at 1,950 to 2,000 F
nominal thickness were taken longitudinally to
and air cool.
the direction of rolling. A small hole was punched
(3) Pickle.
in one end of each specimen so that groups of
(a) 2}6 minutes in 10-percent H 2S0 4 at
specimens could be strung on wire for sensitizing
190 F .
treatments. All such tr eatments wer e carried
(b) 45 minutes in cau stic permanganate
out in furnaces of th e ver tical muffle typ e, elec-
at 200 F .
trically h eated , and constructed especially for
(c) 10 minutes in l %-percent HF plus 10
this work. The inside dimensions of the muffles
per cent HN0 3 at 130 F .
were 4 in. diam eter by 18 in. long. T emp erature
(4) Cold roll to 0.080 in. and straighten.
variation wi thin th e working length of each
(5) Ann eal 6 minutes at 1,950 to 2,000 F and
furnace wer e less than 10 F . Each furnace was
air cool.
controlled hy an individual r ecording potentiom-
(6) Pickle.
eter controller.
(b) and (c) only under (3) above.
Corrosion tes ts for development of inter-
(7) Cold roll to 0.050 in. and straighten .
granular embri ttlem ent w ere conducted in a boil-
The final strip thus had a cold r edu ction of 37)6 ing acidified copper sulfate solution con tain ed in
percent. Al thou gh the sequ ence of fabri cation 2-liter widemouth ed Erlenmey er flasks. These
was no t known, all commercial st eels wer e flasks were equipped with ground glass joint for
furni shed in cold rolled strips 0.050 in. thick , the fittin g th e r eflux condensers. Specimen were
same as the experimental steels. laid in glass racks so th at there was no m etallic
Chemical analyses of all the steels were made on contact between specimens. No more than seven
samples cut from the finished strip ; th ese analyses specimens wer e placed in an individual flask , and
are given in table 1. All experimental steels were material of straight 18- 10, 18- 10 Cb , and 18- 10
made to the base analysis of 18 percent clu-omium , Ti was always segregated in differ ent flasks. A
10 percent nickel , 1% percent manganese, and minimum of 35 ml of acidified copper sulfate
0.40 percent silicon. solution per square inch of surface area was used.
During the progress of this investigation a The solution was changed every 48 hoUl's at
question was raised as to the effect of nitrogen on which tim & all specimen s wer e examined ; those
the Cb/C or TilC ratio. Analyses for nitrogen showing definite evidence of intergranular attack
were therefore mad e, both chemically and by were r emoved . Where evidence of attack, as
vacuum fu sion. It is known that nitrogen com- indicated by a change in color of the solution,
bines with both titanium and columbium. The occurred in less than 2 days, the run was inter-
acid-soluble and acid-insoluble nitrogen can be rupted to remove the failed specimen or speci-
separa ted by treatment of th e steel with dilute m ens, and the solution was changed. 11aximum
sulfuri c acid. For purposes of calculation (as time of exposure in the acidified copper sulfate
noted in table 1), it was assumed that all of the solution was 14 days .
acid insoluble nitrogen was combined with either Preliminary t ests indicated the n ecessity of
titanium or columbium, as th e case might be. carefully controlling certain factors. The origi-
Considering the fa ct that the steels that contained nal choice of concentration for the boiling copper
no titanium or columbium also contain ed no acid sulfate- sulfuric acid solu tion was 13 g of

Austenitic Stainless Steel 323

 TABLE 1. Analyses of the test ateels
8teels designated by the prefix "8" are laboratory m e lts; t hose designated by the prefix "0" arC com mercial melts.

Perccntage of- Ratio Percentage of nitrogen Percentage R at io (re-

-----,-------;---,------c--.. . , - - - . - , - - - - - - - - Percent- (chemical an alys is) (revised) vised)"
age of ni- I - - - , - - - , - - - -- - - - - - - - - - - -
8teel No. trogCI1
Acid in-
o Mn 8i Or Ni Ob Ti Ob/O Ti/O (vacuum
fusIOn ) Total Acid soluble Ob Ti Ob/ O TilO
soluble (by d if-
ference)

0-1.. _____________ 0. 025 0.70 0. 50 19,7 8.8 ___________________________ _ 0.041 0.039 0.039 0,000
0 - 10 _____________ . 026 .59 .40 17,2 12.6 . 026 . 026 . 025 .001
8-37 ______________ .044 1.10 .33 17.8 10.5 . 049 ,053 . 053 . 000
8- 4 _______________ .072 I. 13 . 45 18,0 10.2 .036 .036 .035 . 001
8-23 ______________ . lI 3 1.11 .3 7 17. 6 10.2 . 041 . 039 . 039 . 000

8- 26 ______________ .068 1. 21 .37 17.8 10.0 0,50 7.4 . 065 . 061 . 04l . 020 0,37 5.4
8- 6 _______________ .070 1. 23 ,54 17,6 10.1 .61 8.7 .056 .054 . 034 . 020 . 48 6.9
8- 12 ____________ __ .074 1. 23 .38 17.9 10.0 .75 10.1 . 051 .047 . 024 .023.GO 8. 1
0-3 ._____ __ _______ . 060 1. 69 .67 17.7 H.O .71 1l.8 . . 032 . 035 .015 . 020 . 58 9.7

8 - 27 ___________ .__ .087 1.19 . 40 17.8 10.1 . 76 8. 7 .059 .057 .030 . 027 . 58 6.7

8- 28 _______ ___ ____ . 115 1. 22 .40 17,7 9,9 ,92 8,0 . 04 5 . 045 . 022 .023 . 77 6.7
8- 17 ______________ . 117 I. 21 . 40 18.0 10, 1 1. 14 9.7 .039 .040 .0l6 . 024 . 98 8.3
S-18 ____________ ._ .132 1.18 .40 17,9 10, I 1. 47 11. 1 .044 . 046 . 014 . 032 1. 26 9.5

8-34 ______ . ______ . .067 1.17 .45 17,7 10. 2 O. 26 3. 9 .031 .039 . 001 . 038 0,13 1. 9
S-21. _____________ .071 1. 49 .4 1 17,9 to. 1 ,32 4.5 .027 .031 .002 ,029 .22 3,1
0 - 6_______________ .064 L 32 ,40 18,3 10.0 .35 5,5 .0 12 . 013 . 002 . Oil ,3 1 4,8
8-39 _______ .______ .065 1. 23 .53 18.2 10,1 ,36 5,5 .023 . 023 . 001 ,022 .28 4.3
0 - 2_________ ______ .070 1. 52 .50 17,8 9,6 . 50 7. 1 . OlD . OlD . 001 .009 . 47 6.7
0 - 8 ______________ .075 L 25 . 52 18.0 10,6 . 59 7,9 . 006 . 007 , 001 .006 . 57 7.6

S- 25 ______________ . 082 1.23 . 40 17.7 9. 9 .37 4. .5 .017 .022 . 001 . 021 . 30 3.7

8-35 __________ .____ . 107 1.29 . 42 17. 5 9. i .44 4,1 .012 .016 . 001 . 015 .39 3.6
8-36 ______________ . 109 1. 35 . 48 17,5 10.0 ______ _ .54 5.0 . 022 .018 . 001 . 48 4.4
8- 32 ____________ ._ .105 1. 44 .40 18.0 9.9 1------- .61 5,8 .016 .017 . 001 :~:~ :::::::1 . 56 5.3

"T he revised percentages of 1'i and Ob were calculated by assumi n g t hat aLi of the aeid insoluble nitrogen was combined as TiN o r ObN. According to the
atomic weig hts of tbese elements. I part of nitrogen will combine with 3.43 parts of titanium or 6.64 parts of colum b ium by we igh t . Multiplying these figures
by the amount. of acid insohlblcIlitrogen in the titanium- and colu mbium trcated steels, respectivel y, and s ubtracting the results fro m the amounts of titanium
and columbium present ill the steels gives the revised amounts of t itan ium or columbium available fol' combinat ion wit b car bOll. The revised Til e and Cbl C
ratios were then obtained by dividing the redsed percentages of t itani um .and col umbium by the carbon contents

CuS045H 20, 47 ml of concentrated H 2S0 4, and temperature. In order to eliminate the variable
distilled water to make 1 liter of solu tion. This which scale would introduce, it was decided to
solut ion, which has b een used by some investi- remove all scale. Polishing was tried and proved
gators, corresponded to 0.8 percent of CUS04 and to be too time-consuming; pickling was therefore
8.2 p ercent of H 2S0 4 , and the ratio of CUS04 to adop ted with a schedule of operations as follows:
H 2S0 4 proved too low to prevent surface cor- (1 ) Pickle in 8 percent H 2S0 4 +4 percent HCI at
rosion in many of the steels. Since the r esultant 160 0 F for 10 minutes; wash, scrub , and dry; (2)
corrosion complicated the evaluation of inter- pickle in 10 p ercent HN0 3 + 1 percent HF at
granular embrittlement, this solution was dis- 160 0 F for 5 minutes; wash , scrub , and dry; (3)
carded in favor of that containing 100 g of passivate in 20 p ercent HN0 3 at 125 0 F for 15
CuS0 4 5H 20 , 100 ml of concentrated H 2S0 4 (sp gr minutes; wash and dry.
1.84), and 900 ml of distilled water. This solution To ascertain whether the m ethod of scale
correspond ed to 5.4 percent of CUS04 and 15.4 r emoval influenced the 8usceptibility to inter-
percen t of H 2S0 4 by weight. . granular attack, check tests were made on certain
Th e scale that form ed on specimens during specimens both as p ickled and as polished . The8e
sensitization was influenced by both t ime and tests showed that the m ethod of 8cale removal

324 Journal of Research

 had no detectabl e effeet on Lh e p eClmens t hat
were extrem ely v ulnerable Lo inte rgranular em-
brittlement. With specim ens t h at wer e modef-
, ately vulnerabl e, it appeared that th e extent of
inter-granular attack was gr eater in specimens
that had b een pickled th an in specimens that h as
b een polish ed . Typi cal microstru ctures of such
specimens after corrosion are shown in figure 1.
Since it i frequ ently comm ercial practice to
finish stainle s steeis by pickling, it appeared
logical to test t h e s teels as fini sh ed in th at manner.
Th e suscep t ibility to inter-gr anular attack of
t h e various steels was d et ermined for 12 different
init ial conditions, as listed in tables 2 to 24. A
few steels wer e t ested in only five different initial
conditions, as m ay b e seen from th e par ticul ar
tablp- involved.
In t h e first series of tests (carri ed ou t on th e cold
rolled steels), sp ecimens from each steel were
tested in 16 sens itized conditions. Four sensitiz-
ing temperatures were used - 840, ] ,020, ] ,200,
and 1,380 F. Single spec imens were held at each
sensitizing temper atu re for 2 hours, 2, 8, and 2 1
days. After exposure to t h e boiling copper sulfate
-"1 - .
. " ,.- .- ........
solut ion, it was apparen t t h at cer tain of Lllese
.. ~ '".
sensitizing treatm ents wer e quite iIU10CUOUS and
could b e di scarded. It was decided, th erefore,
to decrease t h e number of sens itizing cond it ions
to seven in all- t hese were 21 days at 40 F;
2 hours, 2, 8, and 2] days at 1,020 F; and 2 hours
and 2 days at 1,200 F. A control specimen, n ot
sensitized, was included in each series .
E valuation of intergranular embrittlem ent was
made by observations of: (a) ch an ge in electrical 0
1&1
resistivity, (b) loss in m etallic ring when th e test %
(I)

specimen was dropped on a steel plate, (c) extent ::::;

o
of cracks occurring after- bend tests of 180, and Q.

(d) appearance of t h e corroded sections under th e

B
mi croscop e. The in terpretation of th ese variou s
tests was frequently influenced by the per sonal
factor , particularly in cases where only sligh t F I GU R E 1. Effect of method of scale removal on susce ptibility
to inter granular attack.
eviden ce of failure existed. Frequently, also,
eviden ce of failure by one method was not cor- A, Extremely vulnerable material after 2 days in t be boiling acidified copper
suJfate solu tion . Unetehed. X IOO. B, L ess vulnerable ma terial after6days
roborated b y anoth er . in the boiliug acidified copper sulfate solu tion. U netched . X500.

Austenitic Stainl ess Steel 325

778365-48- -5
 TABLE 2. Effects of variotts tTeatments tt pon the suscepti bility to inteTgmnulaT attack of steel C- l
(Oarbon= 0.025%-n o stabilizing clement)

Treatment of steel su bseq uent to cold-rolling Sensitizin g treatmen t

Annealin g Stabilizing None 21 d ays 2 hours 2 days 8 days 21 days 2 hou rs 2 days
at 840F at 1,020F at 1,020 at 1,020 o F at 1,020F at 1,200F at 1,200
- - - - - -- - - - 1 - - - - - -- - - -1 - --- - - - - - - - - - - - - - - - - - - - - -
None . __________ . ___________________ N one _______ ______ -_________________ A A A D- E+ D- A A
Do. ________ _____ ___ _____________ y, bour at 1,600F , A. C ___________ A A- A 0 D- D- A A
Y, hour at 1,800F , W. Q -- ---------- N one. ____________________________ _ A A A DE DE E A- A
Do _____ _____ ____________________ y, hour at 1,600 F, A. C ____ ______ A A A B DE E+ A A
Do ______________________________ 2 bours at l,600o F, A. C ___________ A A- A B DE DE A- A
;-2 bour at 1,800 F, A_ C ___ _________ N onc _____ __________ ____ _______ __ __ A A A C- D CD A- A
Do ______________________________ 1 ho ur at l,600 F, A. C ____________ A A A C- D D A A-
3 min . at 1,975 F , W. Q - - ---------- N one ____________________ __ ________ A A A CD D CD A A
C ____________
Do_ - - -_.- - - - - - - - - - - - -- - - - - - - - - - I bou r at I ,600F , A . A A A BC CD CD A A
3 min at 1,975 F , A_ C ______________ None. _. _. _________________________ A A A B- DE C A A
Do__________________ ____ ___ _____ Yo hour at 1,600 F , A . 0 __________ A A A D D A A-
D+
D o______________________________ 2 hours at 1,600 F , A. 0 ___ ____ ___ A A A C- D- D+ A- A-

TABLE 3. Effect of various treatments upon the susceptibility to intergmmdar attack of steel C- tO
(Carbon= 0.026%-no stabiliziug clement)

Treatment of steel subsequent to cold-rolling Sensitizing t reatmen t

21 days 2 h ours 2 days

Stabilizing 8 days 21 days
None 2 hours 2 days
Annealing at 840F a t 1,020 oF at 1,020 ./<' at I ,020F at 1,020 oF at 1,200oF at 1.200
- - - - - - - - - -- - 1 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
None _______________ . _______________ N one __ _______________ ______ _______ A B+ A B- A A- A- A
Do ____________________ ___ _--- --- J.1i bour at 1,600 F ,A. C __________ A A A- DE E E A- B-
J.1i hour at 1,800 F, W. Q ----------- None ________________ __ ____________ A- A A E+ E E AB C-
Do __ ____________________________ y, hou r at 1,600 F, A. C _______ ___ A A A E+ E E A B-
Do __ ______________________ --- --- 2 hours at 1,600 F, A. C __________ .'1.- A A E+ E E A- BC
J.1i hour at 1,800 F , A. C __ __________ None __________ ____________________ A A A E+ E E AD CD
Do ____ __ ________________________ C ____________
I hour at 1,600 o F , A. A A A E E E AB 0
3 min at 1,975 F , W. Q ------------- K one ___________________________ ___ A A A E E E A- A-
Do _____________________ - __ --- --- I hour at 1,600 F, A. C ___ ________ A A A E+ E E A- BC
3 min at 1,975 :b' , A. C ________ __ ____ Ko ne ___________ __ _________________ A A A D+ E E A BC
Do ____________ ___ _______________ 0 ___ _______ A
Yo hour at 1,600 0 F, A. A A D+ E E A C+
Do __ _ -- - - - - ------ -- -- -- - --- - - - - - 2 hours at 1,600 F, A. C __________ A A A D E E A C-

TABLE 4. Effect of vari ou s tTe atments upon the susceptibility to inteTgmnu lar attack of steel 8 - 37
(Carbon ~ 0.044 %-n o stabili zin g element)

Treat ment of steel subseq uent t o cOld-rolling Sensitizing treatm ent

Stabilizing NOll e 21 days 2 hours 2 da ys 8 days 21 da ys 2 h()u rs 2 days

Annealin g at 840F a t 1,020F at I,020 F at 1,020 at 1.0200F at 1,200F at 1,200 oF
------------1-----------1-------------------------
No ne __________________ ____________
TOlle ____________________ __ ___ _ ____ _ A AB A E+ E D+ AB A
Do ______________________________ Yo bour at 1,600 0 F , A. C ______ ____ A D AB E E E B+ A
Y, hour a t 1,800 0 1?, W. Q ----------- None _____________________________ _ A A- A E+ E E D+ D-
Do _________________________ _____ Y, hour at 1,600 l~, A. 0 __________ A A A- DE E E A E
Do ______________________________ 2 hours at 1.600 F,A . 0 __________ A A- A- CD E E BC D

326 Journal of Research

L
 TABLE 5. E,O'ect of vario ~,s treatments upon the susceptibiLity to intergTanular attack of steel 8 - 4
(Carbon= 0.072%-1l0 stabi lizing elemellt)

Treatment of steel subseq uent to cold-rolling Sens itizin g treatmen t

~
i ---------------------,---------------------------------------,----,-----,-----,-----,------
An nealing Stabilizing N on e 21 da ys 2 hOll rs 2 days 8 days 21 days 2 hOllrs 2 days
at 840 ll' at 1,020o F at 1,02QoF at 1,020 0 }? at 1,020 oF at 1,200 0 } "' at 1,200 F'
__-----------------1-------------------11----- ----- - ---- ----- ----- ----- ----- -----
N one. _____ . __ . _____________________ Nono _____________ ___ __ ______ ______ A D+ DE E E E E A
Do ___ _______________________ ____ y,
hour a t 1,600 0 F , A. C __________ B E E F- E E CD A .1
Y, hour at I,SOOo F , W. Q. ----------- N one ______________ _____ ___ . _. ___ ._ A A- A E E E E E
I
I D o ______________________________ y, hour at 1,600 F, A. C __________ DE E E E E E E E
)? D o______________________________ 2 hours at 1,600 F. A. C ____ ______ D E E E E E E E+
C ______ ___ ___ N one ______________________________
Y, hour a t 1,SOOo .F, A. A D A ]~ E E E E
D o ______________________________ 1 hour a t 1,600 F , A. C ___________ C- F. E E E E E D
3 min at 1,975 F , W. Q.------------- N on o__ ___ __ ___ __ _____ ___ __________ A A A DE E E E E
D o ______ ________________________ 1 hour at ] ,600 1", A . C ___________ D E E+ E ].;+ E+ DE E
3 min a t 1,975 F , A . C ____ __________ Non e ___________________ . ____ .. ____ A A A D E E E E
Do ______________________________ Y, hour at 1,600 Y, A. C __________ C D D E E E E E
D o __ ____________________________ 2 hours a t 1,600 Y , A. C __________ C+ E+ E+ E+ E E E E

T A BLl o 6_ E,O'ect of various t1'eatments upon the su sce ptibi li ty to inte1'granular attack of steel 8-23
(Carbon = 0. 11 3%-no stabilizing clemen t)

T reatm en t of steel su bsequenL to cold-rOiling Sensitizing t reatm en t

Annealing Stabilizi ng Non e 21 da ys 2 bours 2 days 8 da ys . 21 d ays 2 hours 2 days

a L8401' at 1.020F at 1,0200F a t ],020F a t 1,020 o F a t 1,200F aL 1,200F
----- - - - - - - - - 1 - - - - - - - - - - - - 1 - - - - - - - - - - - - - - - - ----- - - - - - - - - -----
N one. ____ __. ___________ . ___________ N one _____________________________ A D DE E E E E A
Do ______________________________ y, hom a L 1,600 F, A. C __________ E
0+ E E+ E E+ D A
Y, hour a t 1,SOOo F W. Q - ---------- None. _____________________________ A B+ D+ E E E E E
Do ______________________________ Y, hour a t 1,600 F , A . C ____ ______ E+ E+ E E+ lH E E E
Do ______________________________ 2 hours a t I,Goo :F, A. C __________ j) E E E E E+ E BC

TABLE 7. Ejlect of vw'ious t1'ealments u pon the su scepti bili ty to intel'granu /m' attack of steel 8 -26
(Carbon = 0.068%, co lumbium = 0. 50%; CbjC= i.4 )

'rreatm ent of steel subsequ en t to cold -ro ll in g Sensi tizin g treat men t

AnnealiJl g Stabilizing Ton e 21 days 2 hours 2 days 8 days 21 dAYs 2 hOllrs 2 days
a t 840 F qL1,020 oF a t 1,0201" a t 1,020F at 1 , 0200 ~' a t 1,200 F at 1,200F
----- - - - - - - - - - - 1 - - - - - - - - - - - - - ----- --------- - - - ----------- - - - - - - - -
K ooe _______________________________ N one________ ___ ___________________ A 13+ A- D n+ A A A
D o ______________________________ C __ _________
J.1! hour a t 1600 F , A . A A A D DE D+ A A
J.1! h our a t 1,800 F, W. Q.- -- -- -- ---- N onc. __ . __________________________ A A A E+ E E A A
D o______________________________ y, hour a t 1,600 F , A. C ________ __ A A A D E+ E+ A A
D o_____________________________ . 2 hours a t ] ,600 1",A. C ____ ___ ___ A A A D+ E+ E A A /'
J.1! haUl' at 1,800 F , A . C - - - - - - - - - - - 1\TOIle. ___ __________________________ A A A DE E E+ AB A
Do ______________________________ 1 hour a t 1,600 F,A . C ___________ A A A E+ E+ E+ A- A
3 min at 1,975 F , W , Q. ---- -.- .---- N one ___ . _________________ __ _____ __ A A A C- E E BC A-
D o_____________________________ _ 1 haUl' a t 1,6000 Ii', A. C ____________
r 3 mill a t ],975 F , A .
C ______________ None ____ __________________________
D o______________________________ y, hour a t 1,600 1", A. C __________
A
A
A
A
A
A
A
A
A
])

E+
DE
DE
E+
E
D
E
E+
A-
A
A-
A
A-
A-
Do ______________________________ 2 hou rs at 1,600 F , A . C ______ ___ _ A D-
A A E E+ A- A-

Austenitic Stainless Steel 327

 TABLE 8. Effect, of various treatments 1,pon the susceptibility to intergranular attack of steel 8 - 6
(Carbon ~ 0.070%, columbium ~ 0.61 % ; Cb/C ~8 .7)

Treatment of steel subsequent to COld-rolling Sensitizing troatment

Annealing Stabilizing None 21 days 2 hours 2 days 8 days 21 days I 2 h ours ? clays
at 8{0F a t 1.0200F at 1,020 0 F at 1,020 0F at 1,02OF at 1.200F at 1,200F
----------1-----------1------------------------
None ___ ___________ ._____ ________ __ _ l'\ one _______________ ____ __________ _ A B AB B+ AB AB A- A
Do ______________________________ Yo hour at 1,600 F, A . C _________ _ A A A C- C- B A A
Yo hour a t 1,800 F , W . Q ___________ None _______________________ -- - --- - A A A C+ D- E+ A A
Do ______________________________
Do ___ ___ ________________________
Yo hour at 1,600 F, A. C _________ _
2 hours at 1,600 F, A. C _________ _
A
A
A
A
A
A
D+
C-
E+
E+
E+
D-
A
A
A
A
I
0;;
,
Yo hour at 1.800 F , A. C __________ __ None ________ : ____________________ _ A A A BC D C A A
Do ______________________________ 1 hour at 1,600 F, A. C __________ _ A A A D D- D- A A
3 min at 1,975 F, W . Q_____________ None ______________ __ _____________ _ A A A B+ E E A A
Do ______________________________ 1 hour at 1,600 F , A . C ___ __ _____ _ A A A C E D A A
3 min at 1,975 F , A. C ______________ N one ________ _____________________ _ A A A C DE E+ A- A-
Do _____ ____________ __ ___ ________ Yo hOllr at 1,600 F, A. C _________ _ A A A D E+ E A- A-
Do __________ ____________________ 2 hours at 1,600 F, A . C _________ _ A A A DE DE E A A-

TABLE 9. Effect of various treatments upon the susceptibility to intergranular attack of steel 8 - 12
(Carbon~0.074 %, columbium ~ O,75 %; Cb/C~lO.l)

'freatment of stoel subsequent to cold-rolling Sensitizing treatment

Stabilizing 21 days 2 hours 2 days 8 days 21 days 2 hours 2 d ays

Annealing None at 840F at 1,020F at 1,0200F at 1,0200F at 1,02OF at 1,200 o F at 1,200 0F
---------1---------1------------------------
Nonc ____ __ _______________ .____ _____ None . - --- ~ ____ _____ ------ --- ----- A AB A- B+ A A- A A
Do ___ __ ________________ . ___ . ____ Y. hour at 1,600 F, A . C _________ _ A A A A A A A A
Y. hour at 1,800 F, W . Q ___________ None _______________________ _____ _ A A A A A A- A A
Do ______________________________ Y. hour a t 1,600 F, A. C _________ _ A A A A A A- A A
Do __ ___________________________ . 2 hou rs at 1,600 F, A. C ___ ______ _ A A A A A A A A
Yo hour at 1,800 F, A . C ____________ None _ - --------------------------- A A A A A- A- A A
Do ______________________________ 1 hour at 1,600 F, A . C __________ _ A A A B+ B B- A- A
3 min at ] ,975 F, \ \T. Q _____________ None . - _____ . __. __________ . ______ _ A A A A B D+ A A
Do ___________________________ ___ 1 hour at 1,600 F, A . C _________ __ A A A B+ B B A A
3 min at 1,975 F, A. C _______ ______ None ____ _____ ___________________ _ A A A A- AB C- A

1I
A
Do ____________________ . _________ Y. hour at 1,600 F, A. C _________ _ A A A AB C- C A A
Do ______________________________ 2 hours at 1,600 F, A. C _________ _ A A A C+ C C A A-

TABLE 10. Effect of various treatments upon the susceptibility to intergranulm- attack of steel C- 3
(Carhon~O.060%, colum biurn~O.71%; Cb/C~11.8) J,
Treatment of steel subsequent to cOld- roliing Sensitizing treatment

Stabilizing None 21 days 2 hours 2 days 8 days 21 days 2 hours 2 days

Annealing at 840F at 1,020 0 }' at 1,0200F at 1,0200F at J,0200F a t 1,"001' at 1,200F
- - - - -- - - -1- - - - - -- - -1- - - - -- - - - - - -------------
None _______ ____________ ---- -- - -- - -. Nonc ________ _________ ___________ _ A A- A A A A- A A-
Do __ ________________ .--------- - y. hour at 1,600 F, A. C ______ ___ _ A A A A A A A A
Y. hour at 1,800 F , W. Q ----------. None _____ __ ______ __ _____________ _ A A A A A A A A
Do __________ _____ ___ ---- - - --- - -- y. hour at 1,600 F, A. C __ _______ _ A A A A A- A- A A
Do ______ _. _____________________ _ 2 hours at 1,600 F, A. C _________ _ A A A A A A A A
Yo hour at 1,800 F, A. C ___________ _ None _________________________ ___ _ A A A A A A A A
Do ________________ ------ ----- - -- I honr at 1,600 F, A. C __________ _ A A A A A- A- A- A
3 min at J,975 F, W. Q____________ _ l\Tone __ ___ _______ ._ .. __ . ____ _____ A A A A A A A A
Do _____________________________ _ 1 hour at 1,600 F, A . C __________ _ A A A A A A A A
3 min a t 1,975 F, A. C _____________ None __ __________________________ _ A A A A A A A- A
Do ___ ___________________________ Y. ho ur at J,6000 F, A. C _________ _ A A A A A A A A
Do __ . ___________________________ 2 hours at 1,600 F , A . C _________ _ A A A A A A A A

328 Journal o f Research

 T ABL], 11. Effect of various treatments 1ipon the susceptibility to intel'gmmilar attack of steel 8 -27
(Carboo=0.087%, colum bium=0.i6%; Cb/C=8.7)

Treatment of steel subseq uent to cO ld- roiling Sensithing treatment

Annealing Sta bilizing None 21 days 2 hours 2 days 8 days 21 days 2 hours 2 days
at 840 !!' at 1,0201' at 1,02OF at 1,020 0F at 1,020.1<' at 1,2OO 0 !!' at 1,200 0F
------------1------------1-------------------------
Nooe ________ . ______________________ None . _. ____ __. _____ __ ______ . _____ A B+ A D A A A- A
Do ______________________________ 0 __________
~ hour at 1,600 F , A . A A A 0- 0 A13 A A
~ bour at 1,800 ]~, W. Q------.---- None . - - - - - - - - - - - ----- -- - -- - - - - --- A A A D DE E+ A A
Do _________________________ _____ ~ hour at 1,600 F, A. 0 _______ ___ A A A D E+ E+ A A
';!< Do ______________________________ 2 hours at 1,600 F , A. 0 __________ A A A OD E+ D A A

T ABLE 12 . Effect of various treatments u pon the suscep t.i bility to intel'gmmilar attack of steel 8 - 28
(03rbon = 0.115%, eO]lllnbium = 0.92%; Ob/0=8.0)

Treatment of steel subsequent to cold-rolling Sensitizing treatmen t

Annealing Stabili7.ing Non e 21 days 2 hours I

2 days 8 days 21 days 2 hours 2 days
at 840F at 1,02OF at 1,02OF at 1,02OF at 1,0201' at 1,2001' at 1,200' 1'
------------1------------1------------------------
None __________________________ -- --- None ______________________________ A B A- 0- D+ A- A- A
Do ______________________________ ~ hour at 1,600 F, A. 0 __________ A A A BO A A
D+ D+
N one __________ _______________ _____
~ bour at 1,800' F, W. Q------ - - - - A A A ])8 E E A A
i Do ___________________ . - - - -- --- -- ~ bour at 1,600 F,A . 0 __________ A A A D E+ E+ A A
Do __________________________ ____ 2 hours at 1,600 F,A. C ________ :_
{ A A A 0- E+ DE A A
Y2 bour at 1,800 F, A. 0 __________ __ N one ______________________________ A A A DE DE E+ A- A
I Do ___________________ -- - - -- --- -- 1 bOll r at 1,600 l' A. 0 ________ ___ A A A D DE D- B+ A
3 min at 1,975 F , W. Q ------------- N one ______________________________ A A A D+ E E D- A
Do _______________________ -_ -- - __ I hour at 1,600 F,A. 0 ___________ A A A OD E 0- A- A
C ______________ N one _______ . ______________________ A A A DE E A- A
3 min at 1,975 F, A. E+
Do _________________ -- ---- ------- ~ bour at 1,600 F,A . 0 __________ A A A D- E+ E+ A- A
Do _______________________ -- -- - __ 2 bours at ],600 0 F, A. C _________ . A A A E+ E+ DE A- A-

TABLE 13_ Effect of various treatments 1ipon the susceptibility to inle1'granular attack of steel 8 - 17
(Oar bon=0. 117%, colum bium = 1.14%; Ob/0=9.7)

Treatment of steel subsequen t to cold-rolling Sensitizing treatment

Sta bilizing None 21 days 2 hours 2 days 8 days 21 clays 2 bOll rs 2 days
.Anneal ing at 840F at 1,020'1' at 1,020' 1' at 1,020F at 1,0200 ~' at 1,2001' at 1,200' .!!'
----------1----------1-------------------------
None __________________ - ____ - ----- -- ~T onc ______________________________ A B+ A- AB AD A- A A
Do ________________________ -- -- -- ~ hOllr at 1,600 F, A. 0 __________ A A A A A A A A
~ bour at 1,800 F, W. Q----------- N ono ______________________________ A A A A A B+ A A
Do ____________________________ -- ~ hour at 1,600 F , A. 0 __________ A A A AD D An A A
Do _________________ ___ __________ 2 hours at 1,61l0 F,A. 0 ________ . _ A A A A A A A A
~ bour at 1,800 F,A. C. ___________ N one ___________________________ -.. - A A A A AD A A A
Do ____________________ . _________ 0 ___________ Be DO A A
1 hour at 1,600 0 F A. A A A D+
3 min at 1,975' F, W . Q------------- None ______________________________ A A A A- 0+ D+ A A
Do ___ ___________________________ 1 bour at 1,600 F, A. 0 ___________ A A A D+ B B A A
"oue _____ ______________________ ___
3 min at 1,975' F,A. 0 ____________ __ A A A A- D- CD A A
Do ____________________ . _________ 0 ______ ____ A D 0 A- A
~ bour at 1,600 F,A. A A D+
Do ______________________________ 2 hours at 1,600 F , A. 0 __________ A A A 0- C A- A-

Austenitic Stainless Steel 329

 TABLE 14. E:O'ect of various l1'eatments tlpon the susceptibility to intergranttlar attack of steel S - 18
(Carbon = 0.132%, columbi um =1.47% ; Cb/C=ll.1 )

Treatment of steol subseqn ent to coldrolling Sensitizing treatment

Annealing Stabilizing Tone 21 days 2 hours 2 days 8 days 21 days 1 2 bours 2 days
at 840F at 1,02OF at 1,020 F at 1,02OF at 1,0200F at 1,2000F at 1,200F
------ ------------1--- ---
None _______________________________ N one. ____________________________ A A- A- 21 - A- A
A A
Do __ . ___________________________ y, hour at 1,600 F, A. C . ____ ._. __ A A A A A A A A
Y, bour at 1,800 F, ' V . Q - -_ ._.-._-- None __ ________________________ __ ~
A A A A A A- A A
Do ___________ . ________________ . Y, hour at 1,600 F , A. C. ______ . __ A A A A A A- A A
~
Do __ ___________________________
2 hours at 1,600 :F A. C .. _____ . __ A A A A A A A A
Y, bour at 1,800 F , A. C . __________ . None _________________ ____________ A A A A A A A A
Do __ . _________ . _________________ 1 hour at 1,600 F,A. C ___________ A A A A- A- A A
B+
3 min at 1,975 F , 'V. Q _._---_._._-- None. ______ ________________ . _____ A A A A A B A A
Do _. _______________ . ___________ 1 hour at 1,600 F, A. C . ___ . ______ A A A A A- A- A A
3 min at 1,975 F, A. C . ____ ._._. __ . 1\To 1l e. _ -- _ --- ------- -- ---- ------.- A A A A- A- B+ A A
Do _________ C . _________
----------------.- Y2 hour at 1,600 F, A. A A A A B+ B A A
Do _____________________ . _______ 2 bours at 1,600 F,A. C .. ________ A A A A A- A- A A
j
~
TABLE 15. Effect of various t1'eatments upon the stlsceptibility to inte1'granular attack of steel S - 34
(Carbon = 0.067%, tita n ium=O.26%; T i/ C=3.9)

'l'reatment of st eel s ubsequent to eoldrolling Sensitizin g treatm ent

Am1ealing Stabilizing N on e 21 days 2 hours 2 days 8 days 21 days 2 hours 2 days

at 840F at 1,020 0F at 1,020 F at J,0200F at J,02OF a t 1,200F at 1,2001"
-------------1--------- - - - - - - - - - - - - - - - - - - - - - - - - ----
N one ___________________ ____________ None _____________________________ A B D- E+ DE B+ A
C+
Do _______________ ._. ___________ y, hour at 1,600 F,A. C . _____ . ___ A E+ D E E E+ A- A
Y, bOll I' a t 1,800 F , ",V. Q -.--------- None _____________________________ A A A E E E DE C-
Do _______________ . __________ . __ Y, hour at 1,600 F, A. C . ___ ._. ___ A E D E E E n B
Do __ _____ . _______ . ____ . ________ 2 hours at 1,600 F,A. 0 ._._. ___ ._ A D D+ E E E C+ A-
y, hour at 1,800 F , A . C ._ None. ____________________ . _______ A A A E E E DE CD
Do ______________________ . ______ 1 bour at 1,600 F , A. C _____ . ___._ A C B- E E E C+ A
3 min at ] ,975 F, ",V. Q .------------ None _________________ . _, _________ A A A C+ E E E+ E
Do _________________________ . ____ I hour at 1,600 F , A . C ___ . _____ ._

l
AB D+ CD E+ E E C- D+
3 min at 1,975 F A. C ____ . ___ . ___ . None - --------------------------- A A A B- E+ E E+ E i
Do __ ______________ . ____________ Y2 hour at 1,600 0 F , A. C. _____ . ___ A BC B+ E E E C E
Do _______ , ____________ . ___ . __ .. 2 bours at l,6000 F,A. C , ________ . A- B- B- DE E E C+ CD

TABLE 16. E:O'ect of various treatments tipon the suscepti bility to intel'gmnular attack of steel S-21
(Carbon=O.071%, titanium=0.32%; Ti/C = 4.5)

Treatment of steel subsequent to coldrolling Sensitizing treatm ent

A1Ulcaltng Stabilizing None 21 da ys 2 hours 2 days 8 days 2l days 2 hours 2 days

at 840F at 1,020 0F at 1,02O F at 1,020 0F at 1,0200F at 1,200 o F at 1.2OOF
_ _ - - - - - - - -1- - - - - - - - - - 1 - - - - - - - - - - - - - - - - - - - - - - - -
N one _______________________________ None ______________________________ A C- B D DE D B+ A
Do . _______________________ , _____ y, hour at 1,600 F, A . C _. ________ A AB AB E+ E+ E+ A- A
Y, bour at 1,800 F W. Q .. --------- J\Tone _______ -- ________ ___________ -- A A A E E E D A- ~
Do . ___________ . _________________ y, bour a t 1,600 F, A. C _. ___ . ___ . A CD B E E E A A
Do. ______ . ____ . ___________ ______ 2 hOUl'sa t 1,600 F, A . C _._. _____ . A A- AB E AD A-
E+ E+
Y, bour at 1,800 F, A . C . ___________ None. _____________________________ A A A E E E D+ B+
Do . ______ . _____ .. _____ . _________ 1 h our a t 1,600 F,A . C ._._._, ____ A B+ A- CD D- D BC A
3 min at 1,975 F , W . Q------------- None ______________________________ A A A D+ E E E DE
Do .___________________________ ._
1 hour at 1,600 F, A . C ._._._. ____ A BC B+ E+ E E B- B
3 min a t 1,975 F , A. C. _____________ None ______________________________ A A A DE E+ E+ DE E+
Do ____________________ . _________ y, hour at 1,600 F,A . C _. ___ , ____ A AB AB E+ E E BC CD
Do ._. ___________________________
2 bours at 1,600 F,A . C _, ________ A- A- B D- E E BC C

330 Journal of Research

 T ABLE 17. EjJect of vaTious t1'eatments upon the susceptibility to 1:nln'gTUmdar attack oj .~te el S- 39
(Carbon=0.065% . titani um =0.36% ; Ti/ C =5 .5)

Tl'catmellt of s lecl s u bscqucnt io cold-ro llin g Sensitizing treatment

A nnealing Stabilizing None 21 days 2 hours 2 days 8 clays 21 days 2 hours 2 da y~

at 84QoF at J,020 F at 1,020oF fit l ,020 oF at 1,200 F at I. 020F at i,200o P
--- - - - - - - - - 1 - - - - - - - - - - - 1 1 - - - - - - - - - - - - - - - -- - - -- - - -
None. _ ____ _________________________ N OIle. _________________ ______ _____ _ A B+ A A- B+ A A A-
Do ______________________________ Yo bour at 1,600 F, A . C _________ _ A A A A A A A A
Yo hour at 1,800 F, W. Q ___________ None ___ ___ ___ ____ __ ______________ _ A A A A- C- C- A- A
Do ______________________________ Yo hour a t 1,600 F, A. C ___ __ ___ __ A A A AD B- BC A A
Do _____________________________ _ 2 b oursat 1,600 F, A. C _________ _ A A A D- BC BC A- A
Yo hOllr at 1,800 F, A. C __________ __ NOllC __________________________ ___ _ A A A BC C- CD AD A
Do ______________________________ 1 hour at 1,600 F , A. C _________ __ A A A BC BC B A A
3 llIin at 1,975 F, W . Q _____________ NOlle _____________________________ _ A A A A E+ E A- A-
Do _________________ __ ___ ___ _____ 1 h our at 1,600 F, A. C __________ _ A A A B C BO A- A-
3 min a t 1,975 F, A. C ______________ Non e _____________ ___ _____________ _
Do _______________________ ____ ___ Yo hour at 1,600 F, A. C __________ _
A A A AB D+ E A A-
A A A AD D D A A
Do ________________________ ______ 2 h ou r s at 1.600" F, A. C _________ _ A A A C+ C+ CD A A-

(
!
TAB I, E 18_ E,O'ect oj various treatments 1lpon the s1lscepti bility to inteTgranular allack of steel C- 6
(C arbon = O.OG4 %, titanium = 0.35% , 'l'i/ C =5.5)

Trca tment of s tccl s u b sequcnt to cold-rolling Scn sitizing tl'ca tment

Annealin g StabiliziJl g N 1 21 days 2 bours 2 clays 8 clays 21 days 2 hours 2 d ays

l one at 8400F at 1,020 0 F at 1,020 F at 1,020 0l? at 1,020 F 3t 1,200 F at 1,200 F
- - - - - - - - - - - - 1 - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
None . _ . __ . ____ ._______ __ _____ __ __ __ None _____________ . __ _____ ______ ___ A A A 11 A- A A A
Do _. ____________________________ Yo hour at 1,600 F, A. 0 __________ A A A A A A A A
Yo hour at 1, 00 F , W . Q ___________ Nonc ______________________________ A A A A- AU C- A A
Do _____________________________ Yo hour at 1,600 F, A . C __________ A A A A- A- A- A A-
D o _____________________________ 2 bOllI's at 1,600 ]'- , A. C _________ A- A- A A A A- A A
Yo haul' at 1,800 F, A. C ____________ NO ll c ____________________________ A A A AU c.: C- A- A
D o ____________________________ 1 hour at 1,600 10', A . 0 ___________ A A A- BC n- A A
3-min at. 1,975 F , 'V. Q ____________ None , ______________________ ._____ A A A it D D- A A-
Do ____________________________ 1 hour at 1,600 F, A . C ___________ A A A AB -13 C- A A
3-min a t 1.975 F, A. C _____________ No n e ______________________________ A A A A D+ ll+ A B
Do _____________________________ Yo haUl' at 1.600 F, A . C__ ________ A A A U+ CD D A A-
Do _____________________________ 2 h o urs at 1,600 F, A. C __________ .A A A 0+ 0+ C+ A li.-

T ABLE 19. EIJect of various t1'eatments upon the susceptibility to intergmnulw' attack of steel C-2
(Carbon = 0.070% , ti ta nium = 0. 50%; Ti/ C = 7.1)

Treatment of stcel s u bsequent to COld -roilin g Sen s itizing treatm ent

Ann ealing Stabi liz ing None I at

21 days 2 hours 2 days 8 clays 21 days 2 hours 2 days
840 F at 1,020 ), a t I,020 o F at 1,020 1' at 1.020 o F at 1,200 1' at 1,2()()OF
---__---------1------------ ---- ---- ---- - - - ---- ---- ---- ----
Nonc __ ___ ____ _____ __ __ __ _ ___ __ _____ Nouc _______ _______ ____ ______ ____ __ A C- A AB A D- A A
Do ____ __ ________________________ Yo h a ul' at 1,600 F , A. C __________ it A A A A A A A
Yo h our at 1,800 F, W. Q ____________ No n e _____________________________ _ A A A A .A A A A
Do ___ _____ ______ ______ ________ __ Yo h our at 1,600 F, A . C __________ A A A A A A A A
Do __________________ ______ ______ 2 ho urs at 1,600 F, A . C __________ A A A A A A A A
Yo hour at 1,800 F, A . C ____________ None ______________________________ A A A A B+ B+ A A
Do ___________ ___________________ 1 hour at 1,600 F, A . C ___________ A A A A A A- A- A
3 min at 1,975 F, W . Q _________ __ __ No n c ______________________________ A A A A BC D A A
Do ______________________ ____ ____ 1 hourat 1,600 F, A. C ___________ A A A A A A- A A
3 min at 1,975 F, A. C ______________ Nonc ________ ____________________ _. A A A A B+ D+ A A
Do ______________________________ Yo hour at 1,600 F, A. 0 __________ A A A A A- A- A A-
Do ______________________________ 2 ho u r s at 1,600 F, A . C . _________ A- A- A A A- A A A

Austenitic Stainless Steel 331

 TABLE 20. Effect of various treatments 1tpOn the susceptibility to intergmnular attack of steel C- 8
(Carbon~0.075%, titanium~0.59% ; '['i/ C ~7.9)

Treatment ofstoel subsequent to cold-rolling Sensitizing treatment

~
21 days 2 bours 2 days 8 days 21 days 2 hours 2 days
Annealing Stabilizing None at 840F at 1,020F at 1,020 o F at 1,020F at 1,020 o F at l,200 0 F at .l,200F I
- - - - - - - - - - - - - - - 1 - - - - - - - - - - - - - 1 - - - - - - - - - -- - -- - - - - - - - - - - - - - - - - - -
None _______________________________ None ______________________________ A- B+ A A AB B+ A A
Do ___________ __ _________ ____ ____ ),j! hour at 1,000 F , A. C __________ A A A A A A A
A
),j! bour at 1,800 F, ",\V . Q----------- Nono ______ ______ __________________ A A A A A A A A
Do ______________________________ ),j! bour at 1,000 F,A. C __________ A A A A- A A A A
Do _______________________ ._. ____ 2 hours at 1,600 F,A . C . _________ A A A A A
"
A A A
),j! hour at 1,800 F A . C ____________ None ______________________________ A A A A- A A A A
Do _________________ . ____ __ ______ I honr at 1,6000 F, A . C ____ _______ A A A A A A- A- A
3min at 1,975 F, W. Q----------- - - None ____________________________ __ A A A A A A- A A
Do __________ .. __ . _. _____________ 1 bour at 1,600 F, A. C ________ _._ A A A A A A A A
3 min at 1,975 F, A. C ______ ________ None ______________________________ A A A A A B A A
Do __________ . _._. _______________ }-2 hour at 1,600 F, A. C _____ . ____ A A A A A A A A
Do _____________________________ 2 hours at 1,000 F A. C __________ A A A A A- A- A A

Tabl e 21. Effect of various treatments upon the susceptibility to intergmnular attack of steel S- 25
~
(Carbo n ~0.082%, titan i um~0.37%; 'ri/C = 4.5)

'[' reatment of steel subsequent to coldrolling Sensitizing treatment

21 days 2 bours 2 days 8 days 21 days 2 hours 2 days

,I
Annealing Stabilizing None at 840F at 1,020F at 1,020F at 1,020F at 1,020F at 1,200o F at 1,200F "\
- - - - - - - - - - - 1 - - - - - - - - - _ _ - - - - - - - - - - - - - - - - - - - -- - - -
None __________ _____________________ None ______________________________ A CD B C- D+ B+ A A
Do ______________________ . _______ ),j! hour at 1,600 l?, A . C . _________ A AB A E+ E+ D+ A- A
),j! bour at 1,800 F , ' V. Q -- .. ------- i\Tone ____ _________________________ _ A A A E E E B A-
Do _____________________________ . ),j! hour at 1,000 F, A. C __________ A B- A- E E+ E A- A
Do ___ .... _______________________ 2 hours at 1,600 F , A. C __________ A A A- DE DE E+ A- A-

TABL1D 22. Effect of various treatments upon the suscepti bility to intergranular attack of steel S-35
(Car bon ~0.107%, titanium=0.44%; Ti/ C = 4.1)

'rrcatment of stecl subsequent to cold-rolling Sensitizing treatmcnt

Annealing Stabilizing None 21 days 2 hours 2 days 8 days 21 days 2 hours 2 days
at 840F at 1,020F at 1,020 F at 1,020 0 F at 1,020F at 1,200 0 F at 1,200.!!'
- ------------1-------------1--- ---------------- - - - - - -
None ___________________________ . ___ None ____________ __________________ A E+ D+ DE C+ B A A
Do ____________ . _______ __________ ),j! hour at 1,000 F, A. C __________ A AB A- DE E D A- A
),j! hour at 1,800 F, " '. Q ----------- None ____________ __ ______________ __ A A A E E E D A
Do __ _______________________ . ____ ),j! hour at 1,000 F, A . C .. ________ A C B E E E A A
Do ______ .. __________________ . __ . 2 hours at 1,600 F,A . C __________ A A A DE E+ E AB A-
),j! hour at 1,800 F,A. C ____________ None ___________________________ __ _ A A A D- E DE ,B- A
Do _________________________ . ____ 1 hour at 1,600 F, A. C ___________ A B+ A- D DE D BC A
3 minat 1,975 Ii' , W. Q------------- None _______ _______________________ A A A C- E E E DE
Do ________________ .. __ . _________ 1 hour at l,OOOo F, A. C ___________ A B+ AB D- E E B- AB
3minat 1,975 F , A. C . _________ . ___ 1\Tone . __________ ___________ ________ A A A DE E E D- E+
Do ______________________ _. ______ ),j! hour at 1,000 F, A. C ___ _______ A B A DE E E B+ C+
Do ______ ... ___ . ____________ . ____ 2 hours at 1,000 F,A. C. _______ __ A B+ B D- E E B C+

332 Journal of Research

 T ABLE 23. E.ffect oj variolLs treatments upon the susce pti bili t y to intergramdar attack oj steel -36
(Carbon=O.109%, titanium = O.54%; '1'i/ C=5.0)

Treatment of steel subsequent to cold rollin g Sen sitizing t reatment

Annealin g Stabi lizin g 21 days 2 h ou rs 2 days 8 days 21 days 2 h ours 2 da ys

None at 840F at 1,020 0 F at 1,020F a t 1,020 0 F at 1,020 F at 1,200j<' at. 1.200 0 F
- - - - - - - - - - - 1 - - - - - - - - - - 1- - - - - - - - - - - - - - - - - - - - - - - -
None _______________________________ None _______________________ _____ __ 13 - D- A
A A 13 + 13 + A
Do __________________________ ____
Yo hou r at 1,600 F, A. C __________ A A ~ A A A A A
Yo hour at 1,800 F , W. Q- -- ------- None _________________ _______ ______ A A A C+ C E+ A A
Do ______________________________ Yo bour at 1,600 F,A. C ___________ A A A A A A A A
Do ___ ___________________________
:; 2 hours at 1,600 F, A. C oo _______ _ A A A A A A A A
Yo boul' at 1,8000 ]1', A. C __ __________ None _____________ __ _______________ A A A 13 - C+ BC A13 A
Do _______ ____ ___________________
1 b our at 1,600 F, A. C ___________ A A A 13 13 A- A A
3 min at 1,975 F, W . Q------------- None. ________ __ ___________________ A A A 13 + E+ E C+ A
Do _________ _____________________ 1 bour at ],600 0 F, A. C ___________ A A A A- A- U A A
3 min at 1,975 F, A . r. ------.-.----- None ______________________________ A A- A C+ DE E A- A
Do ______________________________ Yo hour at 1,600 F, A. C __________ A A- A A- BC B- A A
Do ______________________________ 2 hours at 1,600 F , A. C __________ A A A C+ BC C- A- A-

T A BLE 24. E.(Ject oj various treatments tLpon the susce ptibili ty oj intergramdw' (Lttack oj steel 3 -32
(Cal'bon = 0. I05%, titani um =0.6 1%; Ti / C=5.8 )

Treatm en t of steel su bseq u ent to cold-rolling Sen siti zing treatment

Annea lin g Stabilizing None 21 da ys 2 ho urs 2 days 8 days 21 da ys 2 hou rs 2 clays

at 840F at I,020F at i,020F at 1,0201' at I,020 0 ]!' at 1,2001' at 1,200F
-__--------1-----------1---------------------- ---
N one _______________________________ None ______________________________ A 13 + A C AB 13 + A A
Do ____________ __________________ C __________
Y" hour at 1,600 F , A. A A A A A A A A
Yo boul' at 1,800 F , W. Q ----------- Nonc ______________________________ A A A A B+ A A-
Do ________________ ______________ C __________
Do ______________________________
J1i hou r at 1,600 F, A . "- A A A A A A A
2 bours at 1,600 F, A . C _________ _ A A A A A A A A
___________ _____________________________
Y" hour at 1,800 F , A . C~ ~ro n e

A A A 13+ B A A A
Do ______________________________
I hour at 1,600 F, A. C __________ ~
A A A A n A'fI A A
No uc ______________________________ A
3 min. at 1,975 }' , W. Q------------ A A A A- D D A
D o______________________________ 1 bour at 1,600 F, C ___________ A
A. A A A A- A- A- A
C _____________ None ______________________________
3min. at 1,975' F, A. A A A B+ C+ DE A A
Do ______________________________
J1i bour at ] ,600 0 1', A. C _________ _ A A A A- B+ B- A A
Do ______________________________ 2 h OlifS at ] ,600 0 F, C __________
A. A A A A- n BC A J\.

v _Results and Discussion of this statement is shown in figure 2 . This figure

shows the microstructur e of a straig'ht carbon
All specimens were examined for carbide dis- (0.09 %) austenitic steel, initially as cold rolled,
tribution subsequ ent to sen sitizing. The type of after sensitizing 2 hours at 1,200 F (fig. 2, A)
distribu tion of th e precipitated carbides was no t and after sensitizing 2 days at 1,200 0 F (fig. 2, B).
an infallible indication of t he resistance to inter- Both micrographs show a precipita tion of carbides
granular attack. Steels in which the carbides at th e grai.n boundaries and on various lip planes,
were distributed randomly were usually r esistant and it is evident that the microstru ctures resulting
to intergranular attack. However , steels that from the two treatments are indistinguishable.
contained carbides at the grain boundaries, even
The behavior of these two specimens after ex-
though th ese carbides were distribu ted as a con-
tinuou s network, either were or wer e not sus- posm e to the boiling acidified copper sulfate solu-
cepLible to intel'granular attack, depending onLhe tion, however, differed radically (fig. 2, c). The
time-tempera ture relation during sensitization. left side of the micrograph, which corresponds to
Frequently the microstructures of susceptible and specimen A, was exposed 2 days and suffered
unsusceptible specimen of the sam e st eel ap- sever e intergranular corrosion . The right side
peared quite similar. A rath er striking illustration of the micrograph, which corresponds to specimen

Austenitic Stainless Steel 333

r------------------------------------ ----

present a detailed account of the test data pro-

cured. All data were assembled in tabular form
for study. Thc performance of each specimen
was then rated on the basis of each of the four
methods of evaluation (electrical r esistivity,
metallic ring, bend test, and microstructure after
corrosion) _ An arbitrary system of appraisal was
used, as follows:
A. Completely immune to intergranular attack:
Electrical r esistivity, no increase; metallic ring, ~
no impairmen t; bend tes t, no evidence of cracks;
microstru cture, no evidence of intel'granular at-
tack.
B . Practically immune to intergranular attack:
Electrical resistivity, not more than 12 percent
increase; metallic ring, slightly dead; bend test,
slight cracks; microstructure, slight intergranular
attack in extreme surface layers only.
C . Moderately vulnerable to intergranulal' at-
tack: Electrical r esistivity, more than 12 p er cent
but not more than 25 p ercent increase; metallic
ring, slight ; bend test, cracked ; microstru cture,
moderately severe intergranular attack in surface
layers only.
D . Vulnerable to intergranular attack: elec-
t rical r esistivity, more than 25 percent increase;
metallic ring, dead; bend test, broke; microstruc-
ture, intcrgranular attack,
E. Extremely vLllnerable; Same as D , but
OCCUlTing in a few days.
The foUl' ratings obtained for each individual
specimen wer e then averaged by assigning' nu-
merical values to the ratings (A = 4, B =3, C = 2,
D = I , E = O) and converting to the appropriate
letter symbol. PIllS or minus signs were used to
FIGU RE 2. Structure of strai ght carbon (0.09 %) a1lstenitic indicate averages falling slightly above or below
stainless steel, initially as cold-rolled , before and after expo- letters, respeetively, and averages falling midway
sure to the boi ling acidified copper sulfate solution. between two letters were denoted by bo th letters.
A , Sensitized 2 hours at 1,200 0 F . H eavy carbid e precipita tion at grain These averages were then used to prepare tables
boundaries and on slip planes. Etched electrol yticalJy 10 min utes in 10per-
cent sodiwn cyanide. X500. B, Sensit ized 2 days at 1,200 0 F . H eavy car- 2 to 24, inclusive, which summarize qualitatively
h ide precipitation at grain boundaries and on slip planes. Etched electro- the performance of each steel after various an-
lytically in lO-percen t sodi um cyanide. X500. C, Specimens A and B after
exposure to boiling acidified copper sulfate solution . Left side of micrograph , nealing, stabilizing, and sensitizing treatments.
which corresponds to A, was exposed 2 days and snfl'ered severe intergranular The averaged letter symbols may be considered
attack. Right side of micrograph , which corres ponds to B, was exposed 14
days and sbowed no evidence of in tergranlllar attack, yet both had t he same as an order of m erit, bearing in mind that the
type of carbide precipitation, The massive gray globules attached to speci- differences b etween A and B are rather slight, and
men shown on left of C are parti cles of co pper deposited from t he acidified
copper sulfate solu tion, Unetched, X250, those between D and E are very large. Since
specimens were exposed to the boiling acidified
B , was exposed 14 days and showed no evidence copper-sulfate solution for a maximum t ime of 14
whatever of lntergranular attack. , days, specimens that were rated Band C, and in
As a total of well over 2,500 individual speci- many cases even D , might have been rated as
mens were tested, it is obviou sly impractical to satisfactory had they been subjected to the cor-

334 Journal of Research

 roding solution for the more or less standardized attack. The ratio of clll'omium to nickel in teel
time of only 2 days. C- 1 (table 2) was such that, in the pre ence of
A noteworthy feature ho"m by these tables is low carbon, appreciable amounts of delta ferrite
that the sensiLi zing temper-atme of 1,200 F, were present in the miCTostr ucture. Steel C- 10
which is commonly specified, is too high to effect (table 3) con tained lower chromium and higher
maximum susceptibility to intergranular attaek. nickel so that no delta ferrite existed. This latter
Exposme to a sensitizing temperature of 1,020 F steel proved generally to be the more susceptible to
is mu eh more effective, provided the time of ex intergranular attack except that, in the initially
posure is quite long. A period of 8 or 21 days at cold-rolled condition, it was practically immune.
1,020 F appeared to be the most severe sensitiz- The performance of the individual columbium-
ing treatment of those used. It was not unusual and titanium-treated steels may be st udied by
for steels that showed complete immunity to inter- Teference to the appropriate table, but a mOTe
granular attack after sensitizing either 2 hours or readily comprehensible presentation is given in
2 days at 1,200 F to be definitely vulnerable to table 25. In this Lable only the worst averaged
intergranular attack after sensitizing for either 8 rating of each steel, as presented in tables 7 to
01' 21 days at 1,020 F. It is possible thaI, a 24, inclusive, is used. The steels are arranged in
shorter period of time at a temperatme higher table 25 in order of CblC or Ti/C ratio without
than 1,020 F , but lower than 1,200 F , would be regard to the carbon content. It will be' observed
equally effe ctive in causing m axi.:mum sen itiza tha t, for all 12 initial conditions studied , th e
tion. This possibility, however, was not explored performance of the steels improves as the CblC
dllring this invest igation. or TilC ratios increase. Apparently the carbon
Considering the steels that contained no stabiliz- con tent within the range studied (0.06 to 0. 13%)
ing elements (tables 2 to 6, inclusive), it is appar- had little, if any, effect upon susceptibility to in-
ent that all of these were quite v ulnerahl e to tergranular attack, the predominating factor being
intergranular attack after certain sensitizing the CblC or TilC ratio. The rating of tne vari-
treatments. D ecrease in carbon content decreased ous steels, as given in table 25, are plotted, as an
o the degr ee of vulnerabili ty, but even the two very order of meri t, against the CblC and TilC ratios
low-carbon steels tested were quite lI scep tible to in figures 3 and 4.
TAB IJ " 2.5. Quali tative rating of resistance of test steels to intergranular allack

Coldroll ed Annealed M h r at 1,800 0 F , .A nnealed Yz hI' ai Annealed 3 min a t Annealed 3 min at 1,975 Ii',
Hatio (37)1!%) W . Q. 1,800 F , A. C. 1,975 F , W. Q. A. C.

Steel No . Percent 8ta bil No sta- 8 ta bi! 8tabi! No sta- 8tabil No sta Stabi! No s ta- 8 lab il Stabi!
age of C No sta ized >1! bil izing i w d 7f izecl 2 bilizi ng ized 1 b il izi ng ized 1 b ilizing ized >1! ized 2
bilizing b r at hI' at hI' at hI' at hI' at h I' at
C b/C 'ri /C hI' at t reat- 1,600
treat
m ent 1,600 F . treat-
me nt 1.600 F, 1,600 F , treat- 1,600
mcnt F, treat 1,600
m ent F , mont F , 1,600 F,
A. C. A. C. A. C. A. C. A. C. A. C. A. C.

8-20 ...... _........ 0. 068 7.4 D DE E E+ E E E+ E DE E E E

8-28 ...... _........ . 11 5 8.0 C- D+ E E+ E+ E+ DE E E E lH E+
8-6 ....... _...... _. . 070 8.7 :B C- E+ E+ E+ D- D- E E E+ E E
8- 27 ..... __........ . 087 8.7 B C- E+ E+ E+ --- ---- -- --- ---- -- - ---- ----- ---- ----- ------ --- - ------- -
8- 17 _______________
8-12 ...... _........
. ll7
.074
9. 7
10.1
B+
B+
A
A
B+
A-
B
A-
A
A
An
A-
nc
13 - -~'H' B
13
CD
C-
D
C-
C-
C
8-18 ..... ___ ...... _ . 132 11..1 A- A A- A- A A B+ 13 A- n+ 13 A-
C-3 ... _.. __ .... .... .060 11 . 8 A- A A A- A A A- A A A- A A

8-31. .......... _... . 067 3.9 E+ E E E E E E E E E E E

8-35.... _.......... . 107 4. 1 E+ E E E E E DE E E E E E
8- 21. .... . _....... _ . 071 4.5 DE E+ E E E E D- E E E+ E E
8- 25 ............... .082 4.5 D+ E+ E E E+ --------- ------- -- --------- -- - - - - --- ---- - - --- ------ --- - -- --. _--
8- 36 ...... _........ . J09 5.0 D- A E+ A A C+ 13 E B E BC C-
8-39 .... _...... .. . _ . 065 5.5 13+ A C- BC BC CD 13 0 E C E D CD
0-6 .......... __ .... .064 5.5 A- A C- A- A- C- BO D- C- E+ D C+
8-32...... _.. _ ---- .105 5.8 C A C- A A B B D A- DE B- BC
0 - 2................ . 070 7. 1 C- A A A A 13+ A- D A- D+ A- A-
0 - 8 .... __ ._ ..... _. _ . 075 7. 9 B+ A A A- A A- A- A- A B A A-
T his table was prepar ed from tables 7 to 24, ill clusive, using only the worst a veraged rating of each steel in each initial condition. For lOstallce, steel 8- 26.
as coldrolled and st abilized ~ bour at 1,600 F, was ra ted DE as tested after sensitizing 8 days at 1,020 F (sec table 7). Although for all other conditions of
sensitiza tion the ratings we re higher than DE . this worst rati ng was used in t bis summ ary table.

Austenitic Stainless Steel 335

 Cold Rolled
A r--'---'---'f
-(:;r=~- ~
Cold Rolled
At----=-.:c.c.::..,r=~---f.. -t------I.. ---1-
B ~--+----t---~ / I
I ;2.1 "
No stab, /ZI ng rea men
I I t B
Stabili zed y, h f :
'X
,
<--
--~
No ,tabil izi ng
/ 1'" I I I at 1600F i/o" treatment
C ~--+---~~~~~----L---~~ C
j>f. ,I StabJii zed Yt hr at 1600F, A C. , l/ X

I /' il
>st.
D~---+~~,+----4-----+----+----i----~ D
~' ~' T
I: X
/
E ~--~~~~~~~~~--~~ E ~--~--~~.~~~--~--~----~--~
Annealed Vz hr: at IBOOF, W. Q. Ann ea led Yz hr at 1800.~~_~_~~:11- ___ !lll _
Ar------------r-- ~~J-~D_~ ,_~
Stabilized Z hr.
at 1600"F, A . C ~
I (1--= -.:=e A
Stabi lized Yz hr
at 1600F, A.C - r -!
/i>
L
/ /'
B r---'---,---~~-r---L---L--~ B
If,t---L No sta'bilizinq Stabilized z: hr "'---- : @
I

I I,' trealment at 1600F. A C. ; I

C r---~--~----++~~------------~ C
II i '- Stabilized Yz hr : ~X No stabilizi ng

D ~~---+---+/~-r--'---'---i
.I at 1600F, A C.
D
! 7-----+- treatment

, I
.-.~
: I
E~--~C~~~~~--~--~----~--1 E ~~_ .~i-~X ~~ __ __~~
A Annealed Yz hr. at IBOO" f, A C -x----x-~--_; Annealed Vz hr ot IBOOF, A. C.
A
No stob iilzl n.g I /V .... Stabili zed J hr I _/.J--....:-~
treatment~/~ ... ~ ... , at 1600"F, A.C , ',........,...1;
~I ,,/
B r---'---'---~+--r~-r--_+--~ :'= B
~ I . ~\
!...

L:"
i C 1------+----+----t-r>I't'
---.. -r--\-L-----'----l ...
0
C ;/~ ~~----'-----1
" I/~ ,
!...
'0 II,' StabJl,zed I hr No stabilizing
... / " at 1600F, A.C. "
'U
L- I treatment
~ D X~,~---+----'---~r----l a D
I

a x'/'
.. , ....
,I.e '-/
E ~-..........X ........ E1 - - - ' - -
" ,- -'--.. . . .-
-Jx-.J. . . . . - -......-""1
Annealed 3 min at 1975f, W. Q
A Stabilized I hr. ---t'/ A
Annealed 3 mi n at 1975 F, W. Q
,-----~
____ , ,-
x'
at 1600F, A .C.-........
B ~---r----,---~-r~~~X~--r---~
/' I
B I
" /
;'
.
Stab ilized I hr ~,'
"
I II at 1600F. A . C. "
/
C ~--+---+---~~-r,-~~--~--~ C
, ]I / .'- ..
,,
I
:
I 2~
No stobJi lzinq
treotment I
/
D ~--~--~----~+-~----,----.--~ D ~--~---+--~Ir--X ~X;--~----j
//' " X / / No ,tab ili zing
~ / '-... Ire at ment
E~--J->~~~:~~~--~--~~ E ~--'-- __.:....X-X:-:;;..<'---------1
A ~ nnealed 3 min at 1975"F, AC "'" Ann eale d 3 min at 19 75F, A .C.
Stab il ized Z hr
at 1600F, A C ----+-- ~.('
I p//,:X
A
h0 7 ,/Ft!-
Stab ili ;ed Yz
I
at 1600 F, A . C. J
Br---L------------r-,~--_+--~ B ~
No stabilizing treatmen~L ~: Stabilized Z hr. '"
at 1600F, A .C. ~'~
/ I

C r---~--~----+---~ff---~--~---i ~ C
J

p '~at 1600F,A.C
D ~---+----r----+:T.~,r-,~r----r----'---~
J1.~' Stabilized Yz hr
D
loil: ~
/
~ ~' ' _~ X.,?
I X
X ...- / No stabilizing
treatment
E L.-_-J....~@ ....1...._....._ _.1..-_-'-_-' E '---------. II~X- ><-""""'-----------......
7 B 9 10 II II: 3 4 567
Rat io, cb/c Rat io, Tifc
FIGURE I nfluence of ratio of Cb/C and of initial heat
3. FIGURE 4. Influence of ratio of Ti/ C and of initial heat
treatment upon resistance to intergranular attack. treatment upon resistance to intergranular attack,
See page 334 for explanation of significance of letters representing order See page 334 for explanation of sign ificance of lett~rs representing order of
of merit. merit.

336 Journal of Research

 Regardless of the initial condition of the steels, 3. In Lhe columbium- and titanium-bearrug
increase in CblC or TilC to the higher ratios had steels, carbon content within the range of 0.06
a markedly beneficial effect upon the resistance to to 0.13 per cent had no influence upon the r e ist-
intergranular embrittlement. The ratio r equired ance to intergranular attack, except insofar as it
for substantial immunity varied with the initial influenced the CblC or Ti/C ratios. teels
condition of the steel. Of the initial conditions having similar ratios ot stabilizing clemen t to
studied, those conferring maximum immunity to carbon had approximately the same degree of
intergranular attack wer e as cold rolled or as susceptibility to intergranular attack r egardless
quenched from 1,800 F in water. Increase in of the carbon content.
annealing temperature from 1,800 to 1,975 F 4. Both the columbium- and titanium-treated
impaired the resistance to intergranular attack. steels exhibited greater resistance to intergranular
The deleterious effect of high er annealing temper- attack as cold rolled or annealed at 1,800 F and
atures upon susceptibili ty to intergranular attack water quenched than as annealed at 1,800 F and
has been shown by other investigators [8]. Air air cooled , or as annealed at 1,975 F and either
cooling instead of water quenching after annealing water quenched or air cooled.
was also detrimental. The stabilizing treatment 5. Stabilizing heat treatments at 1,600 F had a
appeared to be quite necessary for the titanium- n egligible effect upon the r esistance to inter-
treated steels but was generally of only slight granular embrittlem cnt of the columbium-treated
benefit to the columbium-treated steels. In fact, teels. The p erformance of Lhe titanium-Lreated
a superimposed stabilizing treatment appeared steels carrying the higher ratios of TiIC, however,
actually to be d etrimental to the columbium- was markedly improved by such treatments.
treated teels as air cooled from 1,800 F. The Variation in time of the stabilizing treatments
data indicated no significant differences between from ~f to 2 hours had no eff ect.
stabilizing periods of }f and 2 hours at 1,600 F . 6. When properly treated, substantially com-
plete immunity to intergranular attack: may be
VI. Summ ary a n d Conclusions obtained wiLh a minimum ratio of Cb/C= 10 and
TijC = 5. For more "fool-proof" immunity, it is
Data arc presented on the r esistance to inter- believed that the e ratios should be 12 and
granular embrittlement of 23 austenitic corrosioD - r espectively.
, resisting steels (18% Cr-10 % Ni base composition) It should be emphasized that the data and con-
in 12 different initial conditions. Suscep tibility to clusions given in this paper r efer only to the
intergranular a tta ck was determined after seven susceptibility of the test steels to intergranular
different sensitizing treatments, followed by a attack as developed under test conditions consid-
maximum of 14 days exposure in a boiling erably more severe than those normally used.
acidified copper sulfate solution. The following
conclusion appear warranted:
1. Of the various sensitizing treatments utilized ,
maximum susceptibility to intergranular attack The author are indebted to Lt. D ennis J .
was developed by either 8 or 21 days at 1,020 F. Carney and James Darby, Naval R esearch Labo-
The commonly used sensitizing treatment of 2 ratory, for assistance in melting the experimental
hours at 1,200 F was ineffective in developing steels ; to G. N . Goller, Rustless Iron and Steel
susceptibili ty in any but the most vulnerable Division, American Rolling Mill Co., Baltimore,
steels. Md., for forging many of the steels; to M. E.
2. The straight cm'bon austenitic corrosion- Carruthers and H. r. White, American Rolling
r esisting steels were very susceptible to intergran- Mill R esearch Laboratory, Middletown, Ohio, for
ular embrittlement. The susceptibility decreased assistance in rolling the experinlental steels; to
as t he carbon content decreased but, with the J. L . Hague and J . T . Sterling, National Bureau
exception of one low-carbon steel in the cold- of Standards, for the chemical and vacuum fusion
rolled condition only, even the very low carbon analyses, respectively, and to Albert L ewis,
steels (0.025 % C) were vulnerable r egardless of National Bureau of Standards, for assistance in
heat treatment. the early phases of the work.

Austenitic Stainless Steel 337

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This investigation was made possible by the [4] H . D. Newell , Trans. Am. Soc. Steel Trea ting 19.
generous support of the Bureau of Aeronautic , 673 (1932) .
Navy Department, and the friendly cooperation [5] P . Payson, Trans. Am. Inst . Mining Met. Engineers
100. 306 (1932).
of N. E. Promisel and B. A. Kornhauser of that
[6] E . C. Bain, R. H . Abom, and J . J . B. Rutherford, I
Bureau. Trans. Am. Soc. Steel Treating 21. 481 (1933) .
VII. References [7] Frederick M. Becket and Russell Franks, Trans. Am.
11] B. St.rauss, H . Schottky, and J. Hinnilber, Z. anorg. Inst . Mining Met . Engineers 113, 143 (1934).
Chem. 188, 309 (1930) . [8] L . B . Pfeil and D . G . Jones, J . Iron Steel Ins t . 127. I
[2] Robert H . Aborn and Edgar C. Bain, Trans. Am. Soc. 337 (1933).
Steel Treat ing 18, 837 (1930) .
[3] E . Houdremont and P . Schafmei ster, Arch. Eisen-
hilttenswsen I, 187 (1933) . WASHINGTON, D ecember 16, 1947.

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338 Journal of Research

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