RESIDUAL STRESS IN CLAD AND UNCLAD DIGESTERS 00595
6
8/7/2019 RESIDUAL STRESS IN CLAD AND UNCLAD DIGESTERS 00595 http://slidepdf.com/reader/full/residual-stress-in-clad-and-unclad-digesters-00595 1/6 RESIDUAL STRESS IN CLAD AND UNCLAD PULP DIGESTERS A. Garner, N.J. Stead, D.L. Singbeil Pulp and Paper Research Institute of Canada 3800 Wesbrook Mall Vancouver, B.C. Canada V6S 2L9 ABSTRACT Residual stress was measured in clad and unclad carbon steel digesters before and after stress re- lief anneal. Laboratory measurements were also made on test plates. Stress relief anneal was found to be successful for carbon steel, but only marginally so for austenitic stainless steel cladding. INTRODUCTION The large pressure vessels called digesters are used to cook wood chips in the kraft process. They can be up to 8.2 m diameter x 61 m high (27'dp x 200'). They can be subject to stress corrosion cracking if made from carbon steel (1). To minimise this risk, these digesters are post-weld heat-treated (PWHT) on-site after erection to relieve residual stress. In North America, digesters can also be made partly or fully from 304L roll-clad carbon steel and these too are PWHT. Unlike carbon steel, stainless steels such as 304L or 309L weld deposit are not generally susceptible to stress corrosion cracking in alkaline sulphide kraft: liquors. However, cracking of 304L cladding is known to occur in the vapour phase of kraft digesters (2,3). Direct measurement of residual stress was undertaken during construction of two continuous di- gesters, one clad and one unclad. Stress measurements were also made on full thickness laboratory weldments (4). One of the main objectives was to assess residual stress levels after PW HT of a clad ves- sel. Copyright • 2000 by NACE International.Requests or permission to publish this manuscript in any form in part or in whole must be in writing to NACE ternational, Conferences Division, P.O. Box 218340, Houston, Texas 77218-8340. The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association. Printed in U.S.A. 00595 CORROSION 2000 Paper No.
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Transcript of RESIDUAL STRESS IN CLAD AND UNCLAD DIGESTERS 00595
8/7/2019 RESIDUAL STRESS IN CLAD AND UNCLAD DIGESTERS 00595
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R E S I D U A L S T R E S S I N C L A D A N D U N C L A D P U L P D I G E S T E R S
A . G a r n e r , N . J . S t e a d , D .L . S i n g b e i l
P u l p a n d P a p e r R e s e a r c h I n s t i t u t e o f C a n a d a
3 8 00 W e s b r o o k M a l lV a n c o u v e r , B . C .
C a n a d a V 6 S 2 L 9
A B S T R A C T
R e s id u a l s t r e s s w a s m e a s u re d in c l a d a n d u n c l a d c a rb o n s t e e l d ig e s t e r s b e fo re a n d a f t e r s t re s s r e-
l i e f a n n e al . L a b o r a t o r y m e a s u r e m e n t s w e r e a l s o m a d e o n t e s t p l a te s . S t re s s r e l ie f a n n e a l w a s f o u n d to
b e s u c c e s s fu l f o r c a rb o n s t e el , b u t o n ly ma rg in a l ly s o fo r a u s t e n i ti c s t a in l e s s s te e l c l a d d in g .
I N T R O D U C T I O N
T h e l a rg e p r e s s u re v e s s e l s c a l l e d d ig e s t e rs a r e u s e d to c o o k w o o d c h ip s i n t h e k r a f t p ro c e s s . T h e y
can be up to 8 .2 m d ia m eter x 61 m h ig h (27'dp x 200 ' ) . Th ey can be sub jec t to s t ress cor ros io n c rack in g
i f ma d e f ro m c a rb o n s t e e l ( 1 ). T o m in im i s e th i s r i s k , t h e s e d ig e s t e r s ar e p o s t -w e ld h e a t - t r e a t e d (P W H T )
o n - s i t e a f te r e re c t i o n t o r e l i e v e r e s id u a l s t re s s . I n N o r th A m e r i c a , d ig e s t e r s c a n a l s o b e ma d e p a r t l y o r
fu l l y f ro m 3 0 4 L ro l l - c l a d c a rb o n s t e e l a n d th e s e t o o a r e P W H T . U n l ik e c a rb o n s t e e l , s t a in l e s s st e e l s
s u c h a s 3 0 4 L o r 3 0 9 L w e ld d e p o s i t a r e n o t g e n e ra l l y s u s c e p t ib l e t o s t r e s s c o r ro s io n c r a c k in g in a lk a l in e
s u lp h id e kr af t: l i q u o rs . H o w e v e r , c r a c k in g o f 3 0 4 L c l a d d in g i s k n o w n to o c c u r i n t h e v a p o u r p h a s e o f
kra f t d iges te rs (2 ,3 ) .
D i r e c t m e a s u r e m e n t o f re s i d u a l s t re s s w a s u n d e r t a k e n d u r i n g c o n s t ru c t i o n o f t w o c o n t i n u o u s d i -
g e s t e r s , o n e c l a d a n d o n e u n c l a d . S t r e s s me a s u re m e n t s w e re a l s o ma d e o n fu l l t h i c k n e s s l a b o ra to ry
w e ld m e n t s ( 4 ) . O n e o f t h e ma in o b j e c t i v e s w a s t o a s s e s s r e s id u a l s tr e s s l e v e l s a f t e r P W H T o f a c l a d v e s -
sel .
Copyright
• 200 0 by NACE In ternat iona l .Reque sts or permiss ion to pub l ish th is man uscr ip t in any form in par t or in whole mus t be in wr i t ing to NACEte r na ti ona l , C on fe r ences D iv i s i on , P .O . B ox 218340 , H ous ton , Texas 77218 - 8340 . The ma te r i a l p resen ted and t he v iew s exp r essed i n t h i s
pap er are so le ly those o f the author (s) and are not necessa r i ly endorsed b y the Ass oc ia t ion. Pr in ted in U .S.A.
00595CORROSION2000
Paper No.
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E X P E R I M E N T A L T E C H N I Q U E S
Laboratory WeidmentsR o u g h b l a n k s f o r th e c i r c u l a r p a t c h t e st w e l d s ( C P T W ) s p e c i m e n s w e r e f l a m e - c u t fr o m 3 8 m m
( 1 .5 " ) th i c k p la t e s o f t h e A S T M A 5 1 6 G r a d e 7 0 s t ee l. T h e b l a n k s w e r e t h e n m a c h i n e d t o a d i a m e t e r o f
2 5 4 m m ( 1 0 " ) a n d o p p o s i n g 1 52 r n m ( 6 " ) d i a m e t e r g r o o v e s w e r e c u t i n to e a c h f a c e o f th e s p e c i m e n s .
E a c h s p e c i m e n w a s s h i e l d e d m e t a l ar c ( S M A ) w e l d e d w i t h 3 t u rn ( 0 .1 2 5 i n c h ) d i a m e t e r E 7 0 1 8 w e l d
e l ec t rodes (F i gu re s 1 ,2 ). Spec i m ens w ere p rehea t ed t o 95°C (200°F ) be fo re w e l d i ng and t he m ax i m um
w e l d i n te r p a s s te m p e r a t u r e w a s r e s tr i c te d t o 1 5 0 ° C ( 4 0 0 ° F ) . A i r - b l a s t c o o l i n g w a s e m p l o y e d t o s p e e d
c o o l i n g b e t w e e n w e l d p a s s e s a n d t o i n d u c e s o m e w h a t h i g h e r s tr e ss l e v e l s in t h e s a m p l e s . E a c h g r o o v e
w a s f i ll e d i n w i t h b e t w e e n 1 5 a n d 1 8 w e l d p a s s e s . D u r i n g w e l d i n g , t h e s p e c i m e n s w e r e r e s t r a i n e d b y
t a c k - w e l d i n g t h e m t o t h e w o r k b e n c h t o p r e v e n t d i s to r t io n ( a n d t h u s t o m i n i m i z e r e l i e f o f r e si d u a l
s tr e ss e s) . E a c h s p e c i m e n w a s f ir s t w e l d e d c o m p l e t e l y o n o n e s id e , th e n o n t h e o t h e r a n d t h e f a c e s o f t h e
s p e c i m e n s w e r e s u b s e q u e n t l y s k i m m e d o n a l a t h e t o a s m o o t h , p la n a r p r o f i le .
Figure 1: SMAW welding o f the 254 turn (10 inch) diameter circularweld patch test (CWPT) specimen.
Figure 2: Circular we ld patch test (CWPT ) specimen between weldingpasses.
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T h e C P T W s p e c i m e n s w e r e P W H T s t re s s r e l ie v e d f o l l o w i n g g u i d e li n e s f or p o s t - w e l d h e a t t r e a tm e n t
g i v e n i n th e a p p l i c a bl e p o r ti o n s o f t h e A S M E B o i l e r a n d P r e s s u r e V e s s e l C o d e . S p e c i m e n s w e r e
w r a p p e d i n s t a in l e s s s te e l f o il t o p r e v e n t e x c e s s iv e o x id a t i o n , a n d h e a t e d t o 5 9 0 ° C ( 1 1 0 0 ° F ) f o r o n e a n d
a h a l f h o u r s . T h e y w e r e t h e n l e f t in t h e f iw n a c e a n d a l l o w e d to c o o l s l o w ly b a c k t o r o o m t e m p e r a tu r e .
I n c o n e l 8 2 ( A W S E R .N iCr -3 ) a n d 3 0 9 L ( A S T M A 1 6 7 ) w e ld o v e r l a y s w e r e a l s o a p p l i e d t o p r e v i -
o u s l y p r e p a r ed C P T W s p e c im e n s . A l l w e l d o v e r l a y w a s a p p l i e d b y a m e t a l in e r t g a s ( M I G ) w e l d i n g
p r o c e s s . S p e c im e n s w e r e m o u n te d h o r i z o n t a l l y o n a r o t a t i n g p e d e s t a l a n d a n a u to m a t i c w e ld in g h e a d
w a s u s e d t o a p p l y th e o v e r l ay . S p e c i m e n s w e r e p r e h e a t e d t o 9 5 ° C ( 2 0 0 °F ) a n d a m a x i m u m i n te r p a ss
w e ld t e m p e r a tu r e o f 1 5 0 ° C ( 3 0 0 ° F ) w a s m a in t a in e d a t a l l t im e s . A p p r o x im a te ly 8 p a s s e s w e r e a p p l i e d
o v e r t h e c a r b o n s t e e l w e ld o n b o th f a c e s o f e a c h s p e c im e n , s t a r ti n g o n th e o u t s id e d i a m e te r a n d w o r k in g
to w a r d s t h e c e n t r e o f t h e s p e c im e n .
D i g e s t e r T e s t s
O n - s i t e m e a s u r e m e n t s w e r e m a d e i n tw o K a m y r c o n t in u o u s d ig e s t e r s d u r in g c o n s t r u c t i o n . I n t h e
u n c l a d v e s s e l , r e s id u a l s t r e s s e s w e r e m e a s u r e d c lo s e t o tw o c i r c u m f e r e n t i a l w e ld s e a m s b e f o r e a n d a f t e rP W H T . T h e w e l d s e a m s c h o s e n w e r e t h e u p p e r tr a n s it i o n w e l d ( w e l d " E " ) a n d a w e l d i n th e c o o k i n g
z o n e ( w e ld "N " ) . C i r c u m f e r e n t i a l w e ld s a r e l a b l e d i n a lp h a b e t i c a l o r d e r fr o m th e t o p o f t h e d ig e st e r . I n
e a c h c a s e , s t r e s se s w e r e m e a s u r e d i n b a s e m e ta l c l o s e t o t h e f u s io n l in e . M a te r i a l s a n d p r o c e d u r e s p e c i -
f i c a t i o n s w e r e t y p i c a l fo r d ig e s t e r c o n s t r u c t i o n a n d c lo s e ly m a tc h e d t h e l a b o r a to r y w e ld m e n t s . T h e
P W H T w a s c a r ri e d o u t o n th e c o m p l e t e v e s s e l u s i n g g a s f i re d d i re c t h e a ti n g f o l l o w i n g s ta n d a r d A S M E
p r o c e d u r e .
T h e s e c o n d d ig e s t e r t e s t e d w a s m a d e f i' om 3 0 4 L r o l l c l a d A S T M A 5 1 6 G r a d e 7 0 c a r b o n s t ee l . T h e
c l a d la y e r w a s 3 m m ( 0 .1 2 5 i n c h ) t hi c k . C i r cu m f e r e n t ia l w e l d s w e r e S A W E 7 0 1 8 w i t h 3 0 8 L ( A S T M
A 1 67 ) G T A W c a p p i n g pa s s es . A s i m i l a r A S M E P W H T p r o c e d u r e w a s p e r f o r m e d o n t h is c o m p l e t e v es -
s e l a f t e r e r e c t i o n . Re s id u a l s t r e s s e s w e r e m e a s u r e d o n tw o w e ld s e a m s o n t h e i n s id e c l a d s u r f a c e o n3 0 8 L w e ld m e ta l b e f o r e a n d a f t e r P W H T in s im i l a r lo c a t i o n s .
R e s i d u a l S t r e ss M e a s u r e m e n t s
T h e b l i n d h o l e d r i l l i n g m e th o d w a s u s e d t o m e a s u r e r e s id u a l s u r f a c e s t r e s s e s i n t h e t e s t s p e c im e n s
( 5 ). A M e a s u r e m e n t G r o u p R S - 2 0 0 m i l l i n g g u id e a n d h ig h - s p e e d ( 4 0 0 ,0 0 0 r p m ) a i r t u r b in e w e r e e m -
p lo y e d , a lo n g w i th a M o d e l P - 3 5 0 A s t r a in i n d i c a to r a n d S B- 1 s w i t c h a n d b a l a n c e u n i t. M e a s u r e m e n t s
G r o u p E A - 0 6 - 0 6 2 R E - 1 2 0 o r T E A - 0 6 - 0 6 2 R K - 1 2 0 s t ra i n g a g e r os e t te s w e r e u s e d t h r o u g h o u t t h e w o r k
a n d S S W h i t e F G d e n t a l c a r b id e b u r r s w e r e u s e d t o d r i l l t h e h o l e s .
Be f o r e r e s id u a l s t r e s s e s w e r e m e a s u r e d , t h e s u r f a c e a t t h e d e s i r e d l o c a t i o n w a s p r e p a r e d t o a 6 0 0 g r i t
f i n i s h . T h e s m o o th e d a r e a w a s t h e n t h o r o u g h ly c l e a n e d a n d a s t r a in g a g e r o s e t t e c e m e n te d o n to t h es p e c im e n ( F ig u r e 3 ). A f t e r c o n n e c t i n g t h e r o s e t te t o t h e s t r a in i n d i c a to r t h r o u g h t h e s w i t c h a n d b r id g e
u n i t , t h e m i l l i n g g u id e w a s p o s i t i o n e d o v e r t h e r o s e t t e a n d a h o l e d r i l l e d t h r o u g h t h e c e n t r e o f t h e ro s e t t e
in 0 .0 0 5 " i n c r e m e n t s ( F ig u r e 4 ) . A f t e r e a c h i n c r e m e n t , t h e d r i l l w a s s t o p p e d a n d t h e r e l i e v e d s t r a in s
m e a s u r e d . I n m o s t c a s e s , t h e m a jo r i t y o f t h e r e s id u a l s t r e s s e s w e r e r e l i e v e d i n t h e f i r s t t h r e e o r f o u r i n -
c r e m e n t s . T h e n o m in a l h o l e d i a m e te r w a s 1 .6 m m ( 0 .0 6 2 " ) a n d t h e m a x im u m h o le d e p th d r i l le d w a s 1 .3
m m ( 0 .05 0 " ) . M e a s u r e d s t r a in v a lu e s w e r e c o n v e r t e d t o r e s id u a l s t re s s b y c o n v e n t io n a l a n a ly s e s . A l l r e-
s idua l s t ress va lues repor ted a re the to ta l s t ress re l ieve d a f te r d r i l l ing a ho le dep th o f 1 m m (0 .040") .
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No te t h a t r e s id u a l s t r es s m e a s u r e m e n t s o f t h is t y p e a r e g e n e r a l l y c o n s id e r e d t o b e a c c u r a te t o w i th in
a b o u t _ +10 % . As t h e r e s id u a l t e n s i l e s t r e ss e s a p p r o a c h t h e y i e ld s t r e n g th o f t h e m a te r i a l ( >5 0 % ) , t h e a c -
c u r a c y o f t h e m e a s u r e m e n t d e c r e a s e s d u e t o p l a s t ic d e f o r m a t io n a r o u n d t h e d r i l l e d h o l e . T h e p r e c i s i o n
o f t h e r e s id u a l s tr e s s m e a s u r e m e n t t e c h n iq u e wa s d e t e r m in e d b y m e a s u r in g t h e r e s id u a l s t r es s p r e s e n t i n
a b lo c k o f A5 1 6 Gr a d e 7 0 s t e e l f r o m w h ic h r e s id u a l s t r e s s e s h a d b e e n r e m o v e d b y s e a l i n g i t i n f o il ,
h e a t i n g i t t o 7 0 0 ° C ( 1 3 0 0 ° F ) f o r 2 4 h o u r s , a n d t h e n f u r n a c e c o o l in g . Re s id u a l t e n s i l e s tr e s s e s m e a s u r e d
in t h e t e s t b lo c k we r e l e s s t h a n 6 M P a ( 0 .8 k s i ) .
Figure 3: Two strain gage rosettes mounted on a multipass 308L stainless steel
weld. Also sh own are support mou nts for the milling guide.
Figure 4: P ositioning the drill prior to blind hole drilling in-situ, w ith a high-
speed turbine drill and a millin g guide.
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Re s u l t s
T h e h i g h e s t t e n s il e s tr e ss e s m e a s u r e d o n e a c h k i n d o f w e l d m e n t a n d c o n d i t i o n a r e s h o w n i n T a b l e 1 .
I t c an be seen t ha t t he PW H T w as e f f ec t i ve i n r em ov i ng r e s i dua l t en s i l e s t r e s s i n ca rbon s t ee l i n t he
l a b o r a t o r y a n d f i e ld w e l d m e n t s . S t r e ss e s c l o se t o t h e y i e l d w e r e l o w e r e d t o n e g l i g ib l e v a lu e s b y P W H T .
C l a d w e l d m e n t s i n th e l a b o r a t o r y C P T W w e r e f o u n d t o h a v e r e l a t i v e l y m o d e r a t e r e s i d u a l s tr e ss a f t e r
w e l d c l add i ng . In con t r a s t, c l ad d i ges te r s w e re foun d to hav e h i gh r e s i dua l s t r e s se s i n t he w e l d m e t a l (68
t o 8 6 k s i ) w h i c h r e m a i n e d q u i t e h i g h a f te r P W H T ( 4 2 to 5 1 k s i) .
D i s c u s s i o n
A s e x p e c t e d a n d i n - li n e w i t h o t h e r m e a s u r e m e n t s i n d ig e s te r s ( 6 -8 ) , P W H T w a s f o u n d t o l o w e r
s t re s s i n ca rbon s t ee l t o a po i n t w he re s t re s s co r ro s i on sh ou l d no t be a conce rn . T he sam e ca nno t be s a i d
fo r s t a in l e s s s t ee l c l ad ves se l s , w h e re PW H T w as foun d on l y pa r t i a l l y e f f ec t i ve i n low er i ng s t re s s i n
309L s t a i n le s s s t ee l w e l d m e t a l . T h i s f i nd i ng i s subs t an t i a l l y con f i rm e d by t heo re t i ca l and ex pe r i m e n t a l
ve r i f i ca t i ons f rom o t he r i ndus t r i e s fo r aus t en i ti c s t ee l c l add i ng on t he i n s i de o f a ve s se l o r o n a f l a t su r -
f a ce , c o n s t r a i n e d b y c a r b o n s te e l ( 9 -1 1 ) . T h e l o w e r c o e f f i c ie n t o f t h e r m a l e x p a n s i o n o f c a r b o n s t ee l
m eans t ha t t he ca rbon s t ee l she l l sh r i nks l e s s on coo l i ng a f t e r PW H T and t h i s cons t r a i n s t he s t a i n l e s s
c l a d d i n g in t e n s io n . T h e c l a d d i n g w i ll r e m a i n i n t e n s i o n a t a m b i e n t a n d o p e r a t in g ( > 1 7 0 ° C ) t e m p e r a -
t u r e s . A n y c o m p r e s s i v e s t r e s s e s , w h i c h m a y h a v e b e e n p r o d u c e d i n t h e c l a d d i n g , f o r e x a m p l e d u r i n g
ro l l i ng o f t he c l ad p la t e , a re r e l i eved du r i ng PW H T and so a re no l on ge r p re sen t to coun t e rac t t he coo l -i ng - re l a t ed t ens i l e s tr e s s i n t he c l ad l aye r .
S t a i n l e s s s t ee l s a r e no t gene ra l l y su scep t i b l e t o s t r e s s co r ro s i on c rack i ng i n t yp i ca l k ra f t l i quo r s .
H o w e v e r , f i e l d e x p e r i e n c e h a s s h o w n t h a t s tr e ss c o r r o s i o n d o e s o c c u r i n v a p o u r - s p a c e c l a d d in g . S i m i -
l a r l y , a c i d c l ean i ng w i t h H C I a l so ca r r i e s a r isk o f s tr e s s co r ro s i on fo r aus t en i t i c s ta i n l e s s st eel s . T h i s
p a p e r h a s s h o w n t h a t a u s te n i ti c s ta i n le s s s t ee l c l a d d i n g m u s t d e p e n d o n m a t e r i a l i m m u n i t y r a t h e r th a n
s t re s s r educ t i on to avo i d s t r e s s co r ro s i on .
I t h a s r e c e n t l y b e c o m e a c o m m o n E u r o p e a n p r a c t ic e t o m a k e d i g e s t er s f r o m s o l id d u p l e x s t a in l e ss
s te e l, t y p i c a l l y 2 2 0 5 . T o a v o i d u n w a n t e d p h a s e t r a n s f o r m a t i o n s , c o n v e n t i o n a l P W H T a r e n o t d o n e o n
2205 o r o t he r du p l ex s t a i n l e s s s tee l s. T he se s t ee ls a r e s i gn i f i can t l y m o re r e s i s t an t t o s t r e s s co r ro s i onc rack i ng t han t he au s t en i ti c s ta i n l e s s s tee l s u sed fo r c l add i ng i n m o s t N or t h A m e r i can d i ges t e r s.
Co n c l u s i o n s
• D i r e c t o n - s i te m e a s u r e m e n t s i n k r a ft p u l p d i g e st e rs h a v e s h o w n t h a t p o s t w e l d h e a t t r e a tm e n t c a n b e
succes s fu l fo r s t r e ss r e l i e f o f ca rbo n s t ee l bu t i s on l y m arg i na l l y so fo r aus t en i t ic s t a i n le s s c l add i ng ;
m o de ra t e l y h i gh s t r e s se s w e re m easu r ed o n t he i n t e r i o r s t a i n le s s s t ee l d i ges t e r su r f ace a f te r PW H T .
• C l ad su r f aces can be sub j ec t t o vapo u r phase c rack i ng i n d i ges t e r s s ince r e s i dua l s tr e s s leve l s can
r e m a i n h i g h e v e n a f t e r P W H T .
A c k n o w l e d g e m e n t s
W e w o u l d l i k e t o a c k n o w l e d g e th e h e l p o f A n d r 6 M e n a r d a n d F r e d H e r b e r t in p r e p a r in g t h e l a b o r a-
t o r y w e l d m e n t s . T h e s u p p o r t a n d e n c o u r a g e m e n t o f m e m b e r s o f t h e T A P P I D i g e s t e r C r a c k i n g R e s e a r c h
C o m m i t t e e , t h r o u g h w h i c h t h is w o r k w a s p a r t i a ll y fu n d e d , i s a c k n o w l e d g e d w i t h t h a n k s .
8/7/2019 RESIDUAL STRESS IN CLAD AND UNCLAD DIGESTERS 00595
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T a b l e 1
T e s t L o c a ti o n M a x i m u m M e a s u r e d R e s i d u a l S t re s s
A s W e l d e d
MP a ( k s i )
A f t er P W H T
MP a ( k s i )
1 . C i r c u l a r p a t c h t e s t w e l d s
Ca r b o n s t ee l we l d m e t a l
3 0 9 L we l d o v e r l a yI n c o n e l 8 2 we l d o v e r l a y
2 . D i g e s t e r s
Ca r b o n s t e e l t o p w e l d
Ca r b o n s t ee l b o t t o m w e l d
Cl a d t o p we l d
C l a d b o t to m w e l d
2 3 0 ( 3 3 )
170 (24)1 0 0 ( 1 5 )
4 4 0 ( 6 4 )
4 6 0 ( 6 6 )
590 (86)
4 7 0 ( 6 8 )
- 1 4 ( 2 )
30 (4 )
7 ( 1 )
360 (52)
3 0 0 ( 4 3 )
R e f e r e n c e s
1 . S ingbe i l , D.L . , 'Pu lp and Pape r Canada",Vol . 87 , (3 ) pT93 (1986) .
2 . Cla rke , S . J . and S ingbe i l , D.L . , "Pu lp and Paper Indus t ry Cor ros ion P rob lems" , NACE Vol . 8 , p294
(1995) .
3 . W e n s l e y , A . " P u l p a n d P a p e r I n d u s t r y Co r r o s i o n P r o b l e ms " , V o l . 9 p 2 7 ( 1 9 9 8 ) .
4 . S ingbe i l , D.L . and G arne r , A. , "M ate r ia l s Pe r fo rm ance" , V o l . 27 , p38 , (1988) .
5 . AS T M E 8 3 7 - 8 9 " S t a n d a r d T e s t Me t h o d f o r De t e r mi n i n g Re s i d u a l S t r e s s e s b y t h e Ho l e - Dr i l l i n g
S t r a in - Ga g e M e t h o d " , Am e r i c a n S o c i e t y fo r T e s t in g a n d M a t e r ia l s ( 1 9 8 9 ).
6 . M o s k a l , M . D. " P u l p a n d P a p e r In d u s t r y Co r r o s i o n P r o b l e ms " , N A CE Vo l . 5 p l , ( 1 9 8 6) .
7 . T h o m a s , P . E . a n d Wh y t e , D . M . , " Ap p i t a " Vo l . 3 7 , p 7 4 8 ( 1 9 8 4 ).
8 . M o s k a l , M . D. , " p u l p a n d P a p e r I n d u s t r y Co r r o s i o n P r o b l e ms " , NA CE , V o l . 4, p 3 2 , (1 9 8 3 ) .
9 . J anov ic , A and Luc ia , A.C . , " In t . J . P res . Ves . & P ip ing" , Vo l . 22 , p l 11 (1986) .
10 . Faure , F . , "P roc . 4 h In t. Conf . on R es idua l S t re s s" , p1188 (1994) .
11 . P luye t t e , E . and Sprane l , J .M. , "P roc . 4 h In t. C one on R es idua l S t re s s" , p860 , (1994) .
