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E L S E V I E R
Journal o f Mater ia ls P rocess ing Techno logy 54 (1995) 186-192
J~lrmlhff
M a t e r i a l s
P r o c e s s i n g
T e c h n o l o g y
S h e a r s p i n n i n g t e c h n o l o g y f o r m a n u f a c t u r e
t u b e s o f s m a l l b o r e
Ra jn i sh P ra k a sh a '* , R .P . S in g h a l b
Punja b Engineering Col lege , Chandigarh, Ind ia
b Nat ional Phys ica l Labora tory , New Delh i , Ind ia
Received 1 April 1994
o f l o n g t h i n w a l l
I n d u s t r i a l s u m m a r y
Me tal sp inn ing is a p rocess in which the defo r mat io n s t resses are local ized to a smal l reg ion . The mate r ia l i s ma de to f low and m ove
o v er t h e ro t a t i n g m an d re l w i th t h e h e lp o f a sp in nin g to o l m o u n ted o n a s ad d le an d m o v in g a lo n g th e p ro f il e o f t h e m an d re l . T h e
p ro cess h as b een in u se fo r a l o n g t im e to p ro d u ce ax i - sy m m et r i c sh ap es an d tu b u la r p ro d u c t s w i th sm a l l L/D ra t io . However , the
conven t ional p rocess fa i l s to p roduce long , th in -wal l , smal l -bore tubes . The p rocess has been modif ied to sp in long , smal l -bore ,
th in - tubes in hard - to -w ork m ater ia ls such as CP t i tan ium, Inco loy 825 , Inconel 600 and S tain less s teel AISI-304 . The tec hno logy o f
ma k ing tubes in the abo ve mater ia ls has been developed . The effect o f feed, ro l ler p rof i le , perce n tage reduct ion and lubr ican ts used on
the su rface fin ish and the pow er consum pt ion whe n work ing wi th AISI-304 is repor ted . I t is observed that the me chan ical p roper t ies
o f the p rodu ct im prove considerab ly , c lose d imensional to lerances are ob tained on ou ts ide and ins ide d iam eters and the wal l
th ickness , and h igh reduct ions are possib le wi thou t in te rmed iate anneal ing . The new process i s economical ly v iab le fo r p roducing
tubes in h igh-s t reng th m ater ia ls , -par t icu lar ly when the vo lum e o f p rodu ct ion is no t h igh . The special featu res o f the modif ied mac h ine
are given also.
I . I n t r o d u c t i o n
T h e p h i l o s o p h y o f m o v i n g t h e m e t a l r a t h e r t h a n r e -
m o v i n g it a n d s i m u l t a n e o u s l y r e d u c i n g t h e f o r m i n g
f o r c e s a n d t h u s p r e s s c a p a c i t y le d t h e m e t a l - w o r k i n g
i n d u s t r y t o l o c a l i z e t h e d e f o r m a t i o n z o n e t o a s m a l l
v o l u m e o f t h e w o r k p i e c e , t h e r e b y e f f e c t i n g s a v i n g s i n
m a t e r i a l s a n d e n e r g y f o r s e c u ri n g t h e r e q u i r e d f i na l
s h a p e .
S p i n n i n g i s o n e s u c h p r o c e s s , i n w h i c h t h e s t r e s s e s a r e
l o c a l iz e d t o a s m a l l r e g i o n a n d t h e m a t e r i a l i s m a d e t o
f l o w a n d m o v e o v e r t h e m a n d r e l w i t h t h e h e l p o f a s p i n -
n in g t o o l i . e . r o l l e r .
T h e p r o c e s s h a s b e e n i n u s e f o r a l o n g t i m e f o r p r o d u -
c i n g c o n i c a l a n d a x y - s y m m e t r i c a l s h a p e s a n d t u b u l a r
p r o d u c t s w i t h a l a r g e d i a m e t e r - t o - l e n g t h r a t io [ 1 - 5 ] . I n
t h e c a s e o f c o n e s p i n n i n g t h e a x i a l t h i c k n e ss o f t h e p r o d -
u c t c h a n g e s a s p e r t h e S i n e l a w , w h i c h s t a t e s :
t = t o s i n ~ , ( 1)
w h e r e t i s t h e s p u n t h i c k n e s s , t o i s t h e t h i c k n e s s o f t h e
b l a n k a n d a is th e s e m i - c o n e a n g l e o f t h e m a n d r e l . H o w -
* Correspo nding aut hor.
e v e r , t h is l a w d o e s n o t a p p l y i n t h e c a s e o f t u b u l a r
p r o d u c t s , a s t h e s e m i - c o n e a n g l e o f t h e m a n d r e l i s z e r o ,
a n d t h e p e r c e n t a g e r e d u c t i o n i n t h e w a l l t h ic k n e s s b e i n g
g i v e n b y
t o - - t
- - x 1 0 0 % . ( 2 )
to
2 . C o n v e n t i o n a l t u b e s p i n n i n g
T w o p r o c e s s e s i n t h e s h e a r s p i n n i n g o f t ub e s a r e
r e c o g n i z e d, t h e s e b e i ng : (i) t h e F o r w a r d o r D r a w i n g
t y p e ; a n d ( i i) t h e B a c k w a r d o r E x t r u d i n g t y p e ;
o f t u b e s p i n n i n g , b o t h b e i n g w e l l d e s c r i b e d , w i t h
f o r w a r d s p i n n i n g u s u a l l y b e i n g p r e f e r r e d E 6 1 0 ].
T h e m a i n f e a t u r e s o f th e p r o c e s s a r e s h o w n i n F i gs . l (a )
and (b ) .
H o w e v e r , t h i s c o n v e n t i o n a l t u b e s p i n n i n g p r o c e s s i s
n o t s u i t a b l e f o r t h e s h e a r s p i n n i n g o f l o n g t h i n - w a l l ,
s m a l l - b o r e t u b e s , a s t h e m a n d r e l i n t h i s c a s e h a s t o b e
l o n g a n d t h i n , a n d w i l l t h e r e f o r e t e n d t o s a g w h e n h e l d
b e t w e e n t h e h e a d - s t o c k a n d t h e t a i l - s t o c k . D u e t o s a g -
g i n g it w il l n o t b e p o s s i b l e t o r o t a t e t h e w o r k p i e c e a l o n -
g w i t h t h e m a n d r e l , m a k i n g t h e c o n v e n t i o n a l s p i n n i n g
p r o c e s s u n w o r k a b l e .
0924-0136/95/ 09.50 © 1995 Elsevier Science S.A. All righ ts reserved
S S D I
0 9 2 4 - 0 1 3 6 ( 9 5 ) 0 1 9 4 0 - G
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R. Prakash, R.P. Singhal / Journal o f Materials Processing T echnology 54 (1995) 186-192
187
a)
r -
ER TR VE
2
b)
= 2
:~ . ' . . _ . 1 ~
. . . ~
Fig. 1. Spinning of tu bul ar products: (a) forward tu be spinning;
(b) backw ard ube spinn ing 1, mand rel; 2, workpiece;3, followerblock;
4, antifrictioncentre; 5, form ing rollers).
3 . M o d i f i e d s h e a r s p i n n i n g
T o b r i n g t h e l o n g , t h i n - w a l l a n d s m a l l - b o r e t u b i n g s
w i t h i n t h e c a p a b i l i t y o f t h e s h e a r s p i n n i n g p r o c e s s , t h e
e x i s t in g p r o c es s h a s b e e n m o d i f i e d a n d a n e w m a c h i n e
d e v e l o p e d ( c o u r t e s y U N D P ) . T h i s is c a p a b l e o f s h e a r
s p i n n i n g t h i n - w a l l ( 0 . 7 5 - 1 . 0 0 m m ) , s m a l l - b o r e ( 2 5 -
3 0 m m ) t u b e s i n l o n g l e n g t h s ( 10 m ) w i t h h i g h d i m e n -
s i o n a l t o l e r a n c e s . S i n c e t h e m a n d r e l h u g s t h e w o r k p i e c e
d u r i n g s p i n n i n g, n o r m a l l y i t c a n n o t b e r e m o v e d f r o m t h e
t u b e m a n u a l l y . T h e r e f o r e , a m a n d r e l r e m o v e r s i m i l a r to
the low-power hydrau l i c d raw-bench has been deve loped
a l so . The m odi f i ed ve rs ion of the m achine has the fo l lowing
bas ic features , and is shown in F igs . 2 and 3. ( i ) The tube
(12) wi th the m an dre l (13) (com pos i te ) m ove s l inea r ly and
the spinn ing tools , i . e . the rol lers (4), rota te . ( i i ) Th e rol lers
(4) a re m o unt ed o n a hy drau l i ca l ly ac tua ted th ree - jaw
chuck (3) replacing i ts original three jaws. ( i i i ) The work-
piece (12) is s l id and clamped over the well- lubricated
m an dre l (13) . ( iv ) The m achine i s adequa te ly ins t rum ented
so tha t the va r ious pa ram ete rs can be recorded and op t i -
mized. (v) Tube s in th e s ize range o f 15-3 2 m m outs ide
d iam ete r , and of 0 . 75-1 .00 m m wal l th ickness and 7000 m m
length can be p roduced on the m achine . (v i ) A th ree- ro ll e r
sys tem ins tead of the usua l two-ro l l er sys tem has been used
to ensure self-a l ignment of the assembly and good concen-
tr ic i ty in the sp un produ ct . (vi i ) A hyd raul ical ly actua ted
6
Fig. 2. Schematic view of the shear spinning machine (1, gripper 3 -jaw chuck; 2, slides; 3, h ydraulic chuck; 4, spinning rollers; 5, ball screw;
6, ball screw nu t; 7, rotatin g cylinder; 8, contr ol pane l; 9, instrum ent panel; 10, loa d cell; 11, cover guard (splash guard)).
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188
R. Prakash , R .P. S inghal / Journal o f Materia ls Processing Technology 54 (1995) 18 6-192
c h u c k ( 3 ) i s u s e d s o t h a t t h e r o l l e r s a r e c l o s e d o n t h e
c o m p o s i t e ( w o r k p i e c e ) a f t e r t h e c h u c k h a s a t t a i n e d f ul l
s p e e d . T h i s r e d u c e s t h e i n s t a n t p u l l i n g l o a d i . e . t h e a x i a l
f o r c e , a t t h e s t a r t a n d m a k e s t h e s p i n n i n g o p e r a t i o n
s m o o t h .
3.1. Technical speci fications o f the mach ine
S iz e r a ng e O D
I D
W a l l t h i c k n e s s W T :
L e n g t h
S p e e d o f t h e c h u c k :
P u l l i n g s p e e d ( f e e d )
( 8 0 - 2 0 0 r p m v a r i a b l e )
R e v e r s e s p e e d
C h u c k d i a m e t e r
C l a m p i n g f o r c e
H y d r a u l i c p o w e r p a c k
P r e s s u r e
4 0 m m m a x . ( 1 5 m m t o
3 2 m m )
1 2 m m m i n .
2 5. 5 m m m a x .
1 0.5 m m
0 .7 5 m m
1 0 00 0 m m m a x .
1 52 8 r p m m a x . ( 1 5 00 r p m
n o r m a l )
5 0 8 r p m m i n .
7 50 m m p e r m i n u t e m a x .
2 8 m m p e r 2 8 r a i n m a x .
( 0 . 2 5 - 2 m m p e r r e v o l u t i o n )
5 m / m i n f i x e d (2 0 0 r p m )
4 0 0 m m ( 1 6 i n )
1 0 0 0 k g f
4 0 H P , 1 8 0 0 r p m , m o t o r
s u i t a b l e f o r 4 4 0 V , 3 p h a s e ,
5 0 c / s A C s u p p l y
2 .0 5 M P a ( 3 0 00 p si ) m a x .
1 .5 M P a (2 2 0 0 p s i )
R e v e r s in g m o t o r
L u b r i c an t m o t o r
M a n d r e l r e m o v e r
: 2 H P g e a r e d m o t o r s u i t a b l e
f o r 4 4 0 V , 3 p h a s e , 5 0 c / s A C
s u p p l y
: 2 H P , 3 0 0 0 r p m s u i t a b l e f o r
4 4 0 V , 3 p h a s e , 5 0 c / s A C
s u p p l y
: D r i v e n b y th e s a m e h y d r a u -
l ic p o w e r p a c k a s m a i n m a -
c h i n e
A s c h e m a t i c v i e w o f t h e m a c h i n e i s s h o w n i n F i g. 2 , t h e
s p i n n i n g a r r a n g e m e n t i s s h o w n i n F ig . 3 a n d t h e r o l l e r
a s s e m b l y w i t h f e e d s c r e w i s s h o w n i n F i g . 4 .
4 . E x p e r i m e n t a l s e t - u p
W i t h t h e p r e s e n t s e t - u p i t i s p o s s i b l e t o s h e a r s p i n a n
i n i ti a l w a l l t h i c k n e s s o f 4 m m s a t i s f a c t o r i l y , th e t u b e
b e i n g i n t h e a n n e a l e d c o n d i t i o n a t t h e c o m m e n c e m e n t o f
t h e o p e r a t i o n . A n a r e a r e d u c t i o n o f 7 0 8 0 % w a s p l a n -
n e d , te s t p ie c e s a t r e d u c t i o n s o f a b o u t 4 0 , 6 0 a n d 8 0 %
b e i n g c ut a n d e v a l u a t e d f o r m e c h a n i c a l p r o p e r t i e s , s u r -
f a c e f in i sh a n d a c t u a l d i m e n s i o n s . T h e w o r k w a s c o n d u c -
t e d o n s t a i n l e s s s t e e l A I S I - 3 0 4 u s i n g d i f f e r e n t l u b r i c a n t s ,
t h e l a t t e r b e i n g u s e d s o a s t o b e a b l e t o o p t i m i z e t h e
l u b r i c a n t w i t h r e s p e c t t o t h e s u r f a c e f i n i s h a n d p o w e r
c o n s u m p t i o n .
C
C h u c k r o t a fe a b o u t
i t s ax i s Z
I I -- I'/ /15.~ -L,.~--)---~.
II ROLLE
-
D)
Fig. 3. Tube -spinn ing arran gem ent (1, grippe r chuck ; 4, rolle r; 10, load cell; 12, work piece ; 13, ma ndre l; 14, key; 15, clam ping ring).
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R. Prakash, R .P. Singhal / Journal o f Materials Processing Tec hnology 54 (1995) 186-192 189
4.
[ - -
/ ( ~ 4.1. Set-up or spinning
/ @ (i) P re f o r m
t ; i
i i q
, I ~ [ ,
~ J / / / / ~ (ii) P e r ip h e r a l sp eed
of ro l lers
] i I ; ' , , , , ' - ~ 5 2 f f ( ii i) F eed ( P u l l in g s p eed )
L_. '- - ( iv) Lu br ic ant
I
Fig . 4 . Rol ler asse mb ly with the feed screw. (2 , f ixed s lide; 2a, move abl e
s l ide; 4 , ro l ler w ith brg; 12 , workp iece; 13 , screw for feed) .
( v i ) M an d r e l
L e n g t h
I n s id e d i a m e t e r
Wal l t h i ck n es s
Surface f in ish
C o n c e n t r i c i t y
M a n d r e l
T u b e
M a t e r i a l
H a r d n e s s
D i a m e t e r
N u m b e r
D i a m e t e r
L e n g t h
H a r d n e s s
Surface f in ish
8 0 0 m m
1 8 m m
4 m m
as mach in ed ( 3 to
5 g in)
w i th in 0 . 2 mm
1 3 0 m/min .
7 5 0 m m / m i n , m a x .
N ev e r s e i ze
( co mmer c ia l n ame)
S i l i con g r eas e w i th
g r a p h i t e p o w d e r
a d m i x e d 1 0 % s o l u b l e
o i l i n w a te r
A I S I D 2
58 Rc
8 0 m m
th r ee a t 1 2 0 ° i n t e r v a l
1 7 .8 mm
1 0 0 0 0 m m
5 5 R c ( b y co ld w o r k in g )
0 .5 gm
T h e f o l l o w i n g l u b r i c a n t s , i n a d d i t i o n t o t h e N e v e r
s e iz e o n t h e m a n d r e l a n d t h e 1 0 % s o l u b l e oi l o n r o l l er s ,
were iden t i f i ed .
( 1) L u b k o t e ( p r o p r i e t a r y i t e m , g r a p h i t e p o w d e r i n
mineral oi l ) .
T a b l e 1
Lu b r i can t : Lu b k o te ( g r ap h i t e ad m ix ed w i th m in e r a l o i l) (1 k g f /mm 2 = 0 . 1 M P a )
R e d u c t i o n H a r d n e s s U T S 0 . 2 % E l o n g a t i o n S u r fa c e
( % ) ( mV P N ) ( k g f /mm 2 ) p r o o f s t r e s s ( % ) f in i s h
(kgf /m m 2) (g in)
D i m e n s i o n s
( m m )
60 413 120.6 not reco rded 12.3 0 .8 OD 20.90
(42Rc) ID 17.78
75 440 138.9 9.4 0.6 O D 19.82
(44.5Rc) ID 17.85
90 460 64.0 4.3 0.6 O D 18.63
(46Rc) ID 17.93
Tab le 2
Lu b r i ca n t : Gr ap h i t e p o w d er in ca s to r o i l ( 1 k g f /mm 2 = 0 . 1 M P a)
R e d u c t i o n H a r d n e s s U T S 0 . 2 % E l o n g a t i o n S u r fa c e
( % ) ( mV P N ) ( k g f /mm 2 ) p r o o f s t r e s s ( % ) f in i s h
(kgf /mm e) (gm)
D i m e n s i o n s
( m m )
44 378.4 113.6 102.0 12 0.65
(38.5Rc)
50 395.2 118.4 104.6 12 0.80
(40.5Rc)
60 407 121.3 105.0 12 0.65
(41.5Rc)
70 438 132.9 110.0 11 0.80
(44.5Rc)
80 452 143.8 119.8 10 0.65
(45Rc)
OD 22.00
ID 18.10
OD 21.55
ID 18.12
OD 21.04
ID 18.14
OD 20.33
ID 18.22
OD 19.50
ID 18.30
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190 R. Prakash, R.P. Singhal / Journal o f Materials Processing Technology 54 (1995) 186-192
( 2) G r a p h i t e p o w d e r ( 3 2 5 m e s h ) c a s t o r o i l a d m i x e d t o
p r e p a r e a m i x t u r e i n t h e f o r m o f a p a s t e .
( 3) O x a l a t e c o a t i n g a c h i e v e d b y a c h e m i c a l r e a c t i o n a t
9 0 1 0 0 ° C w i t h k n o w n c h e m i c a l s ( b o u g h t f ro m M / s
P y r e n e R a i , B o m b a y ) h a v i n g l u b r i c i t y .
( 4 ) M o S 2
p o w d e r ( 3 2 5 ) a d m i x e d i n c a s t o r o i l t o p r e -
p a r e a m i x t u r e i n t h e f o r m o f a p a s t e .
( 5 ) C o p p e r c o a t i n g b y t h e e l e c tr o - d e p o s i t i o n m e t h o d .
T h e r e s u l ts a r e g i v e n i n T a b l e s 1 - 5 . T h e m i c r o h a r d n e s s
r e a d i n g s w er e t a k e n a t 1 0 0 g m l o a d a n d t h e s u rf a ce
f i n i s h e s a r e a l l s p e c i f i e d a s ' R a ' v a l u e s , t h e s u r f a c e r o u g h -
n e s s b e i n g m e a s u r e d o n p i e c e s c u t f r o m s p u n s a m p l e s
w i t h d i f f e r e n t r e d u c t i o n s u s i n g 2 P e r t h o m e t e r , a s t y l u s -
t y p e o f s u r fa c e - r o u g h n e s s m e a s u r i n g i n s t r u m e n t . T h e i n -
s i d e d i a m e t e r w a s m e a s u r e d w i t h a t h r e e - a n v i l i n t r a m i k
( i n s i d e m i c r o m e t e r ) , l e a s t c o u n t o f 0 . 01 m m , a n d t h e o u t -
s i d e d i a m e t e r w a s m e a s u r e d w i t h e x t e r n a l m i c r o m e t e r ,
a l s o o f le a s t c o u n t o f 0 . 01 m m . T h e d i a m e t e r s w e r e m e a s -
u r e d a t b o t h e n d s a n d t h e a v e r a g e d i a m e t e r p r e s e n t e d
i n d i c a t e d i n t h e r e s u l t s .
5 . O b s e r v a t i o n s
B a s e d o n t h e o b s e r v a t i o n s i t c a n b e s a i d t h a t t h e
m i c r o h a r d n e s s d o e s n o t c h a n g e a p p r e c i a b ly a ft er a r e-
d u c t i o n o f a b o u t 6 0 % . W i t h t h e u s e o f d if f er e n t lu b r i -
c a n t s t h e s ur f a c e f i n i s h o n O D o f t h e t u b e i m p r o v e d b u t
d i d n o t s h o w a n y r e a l l y s i g n i f i c a n t c h a n g e , r e m a i n i n g
b e t w e e n 0 . 5 a n d 0 . 8 l am ( R a v a l u e s ) . I t i s c o n c l u d e d t h e r e -
f o r e , t h a t a l u b r i c a n t i s d e s i r a b l e t o c a r r y a w a y t h e h e a t
g e n e r a t e d d u r i n g s p i n n i n g a n d t o i m p r o v e t h e s u r f a c e
T a b l e 3
L u b r i c a n t : O x a l a t e c o a t i n g ( 1 k g f / m m 2 = 0 .1 M Pa)
R e d u c t i o n H a r d n e s s U T S 0 . 2 %
( % ) ( m V P N ) ( k g f / m m 2 ) p r o o f s t r e s s
( k g f / m m 2 )
E l o n g a t i o n S u r fa c e D i m e n s i o n s
{ % ) f i n i s h ( m m )
(p.m)
49 373 116.0 105.8 12.5 0.65 O D 21.72
(38.5R c) 1D 18.15
68 401 127.2 109.4 12.0 0.60 O D 20.44
(41Rc) ID 18 .16
83 432 136.7 116.0 11.0 0.50 O D 19.35
(43 .5Rc) ID 18 .30
T a b l e 4
L u b r ic a n t : M o S 2 a d m i x e d w i t h c a s t o r o i l ( 5 0 : 5 0 ) ( 1 k g f / m m 2 = 0 . 1 M P a )
R e d u c t i o n H a r d n e s s U T S 0 . 2 % E l o n g a t i o n S u r f a c e
( % ) ( m V P N ) ( k g f / m m z ) p r o o f s t r e s s ( % ) f i n is h
( k g f / m m 2 ) ( p m )
40 356 110.6 97 .0 13 0 .75 O D
( 3 6 . 5 R c ) I D
50 378 .3 113 .0 97 .8 12 0 .65 O D
( 3 8 . 5 R c ) I D
61 408 .0 122.4 98 .7 12 0 .70 O D
( 4 1 . 5 R c ) I D
73 438 .0 133.3 100.9 Sa mp le 0 .75 O D
( 4 4 .5 R c ) t e a r e d I D
D i m e n s i o n s
( m m )
22 .30
18.10
21 .67
18.16
20 .90
18.16
20 .06
18.25
T a b l e
5
L u b r i c a n t : C o p p e r c o a t i n g ~ ( t h i c k n e s s 0 . 0 1 m m ) ( 1 k g f / m m 2 = 0 . 1 M P a )
R e d u c t i o n H a r d n e s s U T S 0 . 2 % E l o n g a t i o n S u r f a c e
( % ) ( m V P N ) ( k g f / m m z ) p r o o f s t r e s s ( % ) f i n is h
(kg f /m m z) (p .m)
53 378.4 108.9 95.0 12 0.85
(38 .5Rc)
68 425.6 123.2 107.0 C o u l d n o t 0 .95
( 4 2 . 5 R c ) b e m e a s u r e d
81 438 .0 137.5 116.9 11 0.95
(44 .5Rc)
O D
I D
O D
I D
O D
I D
D i m e n s i o n s
( m m )
21.41
18.12
20 .37
18.15
1 9 . 4 2
18.36
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191
f in is h . D i f f e r e n t l u b r i c a n t s d o n o t s h o w a n y c h a n g e i n t h e
r e s u l t s a n d s o a n y g o o d g r e a s e c a n b e u s e d a s l u b r i c a n t
o n t h e o u t s i d e d i a m e t e r o f t h e t u b e . T e n p e r c e n t s o l u b l e
o i l i s a d e q u a t e o n t h e r o l l e r s t o c o o l t h e m d u r i n g t h e
p r o c e s s .
T h e s u r f a c e f i n is h i s o f th e o r d e r o f 0 . 9 5 g m , w h i c h
i s c o m m e r c i a l l y a c c e p t a b l e a n d c a n b e o b t a i n e d e a s i l y .
T h e c o n c e n t r i c i ty w a s f o u n d t o b e 8 % o f th e w a l l th i c k -
n e s s o f t h e s p u n t u b e . T h e o u t s i d e d i a m e t e r c a n b e
c o n t r o l l e d t o w i t h i n 0 . 0 5 t o 0 . 0 8 m m w i t h t h e h e l p o f
t h e m i c r o m e t e r s c r e w s u s e d f o r d r i v i n g t h e r o l l e r s . T h e
p r e c i s i o n - g r o u n d m a n d r e l e n s u r e s t h a t t h e i n s i d e d i a -
m e t e r c a n b e m a i n t a i n e d w i t h i n t h e l im i t s o f c o m m e r c i a l
t o l e r a n c e s .
T h e m e c h a n i c a l p r o p e r t i e s w e r e i m p r o v e d c o n s i d e r -
a b l y , a s e x p e c t e d . T h e t e n s i l e s t r e n g t h o f t h e s t a i n l e ss
s te e l A I S I -3 0 4 i n c r e a s e d f r o m 6 5 k g f / m m 2 t o a b o u t
1 4 5 k g f / m m 2 a t a b o u t 8 0 % r e d u c t io n a n d t h e
y i e ld s t r e n g t h ( 0 . 2% p r o o f s t re s s) f o r m 4 4 k g f / m m 2
t o a b o u t 1 3 5 k g f / m m 2. T h e d u c t i li t y d e c r e a s e d t o
b e l o w 1 0 % .
A m a x i m u m r e d u c t io n o f 8 0 % m a y b e p l a n n e d
s a fe l y a n d m a y b e a c h i e v e d w i t h o u t i n t e r m e d i a t e a n n e a l -
i n g . A n 8 3 % r e d u c t i o n s a m p l e o f st a i n le s s s te e l
d e v e l o p e d c r a c k s i n o n e o f th e e x p e r i m e n t s . I f th e
f i n i s h e d s i ze o f t h e t u b e c a n n o t b e a c h i e v e d w i t h u p t o
8 0 % r e d u c t i o n , t h e t u b e s h o u l d b e r e m o v e d f ro m t h e
m a n d r e l a n d a n n e a l e d b e f o r e c o n t i n u i n g w i th t h e p r o c e s s
f u r t h e r .
T h e s p e e d , t h e f e ed a n d t h e r o l l e r p r o f i l e a r e o t h e r
f a c t o r s w h i c h , a p a r t f r o m a f f e c t i n g t h e s u r f a c e f in i s h o n
t h e s p u n t u b e , a f fe c t t h e p r o d u c t i o n c a p a b i l i t y o f t h e
m a c h i n e . T h e m a x i m u m s p e e d s a r e n o t c r i t i c a l i n t h e
s h e a r s p i n n i n g p r o c e s s , b u t f e e d h a s a m a r k e d e f f ec t o n
t h e s u r f a c e f i n i s h o f t h e s p u n t u b e . I f th e f e e d r a t e i s
i n c r e a s e d t h e s u r f a c e f i n i s h b e c o m e s c o a r s e r . T h e r e f o r e ,
a c o m p r o m i s e h a s t o b e e s t a b li s h e d b e t w e e n t h e f e e d , t h e
s p e e d a n d t h e r o l l e r p ro f il e s k e e p i n g t h e p r o d u c t i o n
c a p a b i l i t y , t h e s u r f a c e f i n is h o n t h e s p u n p r o d u c t a n d t h e
p r o d u c t m i x i n v i e w .
T h e t e c h n o l o g y is e c o n o m i c a l l y v i a b le , e s p e c ia l ly w h e n
t h e v o l u m e o f p r o d u c t i o n i s l o w , b e c a u s e o f t h e f lo w c o s t
o f e q u i p m e n t a s a g a i n s t t h e c o s t o f c o n v e n t i o n a l t u b e -
m a k i n g p r o c e s s e s , v i z . h o t e x t r u s i o n o r p i e r c i n g f o l l o w e d
b y d r a w i n g o r p i l g e r i n g , w h i c h a r e h i g h l y c a p i t a l i n t e n -
s iv e . F u r t h e r t h e y i e l d o f t h e f i n i s h e d p r o d u c t i n t h e c a s e
o f t h e c o n v e n t i o n a l p r o c e s s e s e s p e c ia l ly w h i ls t w o r k i n g
w i t h h a r d - t o - w o r k m a t e r i a l s , is v e r y l o w , r e s u l t in g i n
h i g h e r c o s t o f c o n v e r s io n . T h i s is s u b s t a n t i a t e d f u r t h e r
d u e t o : ( i) t h e r e d u c t i o n p e r p a s s i n t h e c a s e o f s p i n n i n g
b e i n g a s h i g h as 4 0 % a g a i n s t a r e d u c t i o n o f 1 0 - 1 5 % i n
c o n v e n t i o n a l p r o c e s se s , (ii) t h e m a x i m u m r e d u c t i o n b e -
f o r e i n t e r m e d i a t e a n n e a l i n g b e i n g a b o u t 8 0 % a g a i n s t
4 0 - 5 0 % i n th e c o n v e n t i o n a l p ro c e s s , r e s u lt i n g in a n
h i g h e r d i s c a r d o f t u b e a t t h e l e a d i n g e n d d u e t o s u c c e s si v e
p o i n t i n g ; a n d ( iii ) t h e n u m b e r o f d r a w i n g p a s s e s t o o b -
t a i n f in a l d i m e n s i o n s b e i n g g r e a t e r in t h e c a s e o f c o n v e n -
t i o n a l p r o c e s s e s t h a n i n s p i n n i n g r e s u l t i n g i n h i g h e r c o s ts
o f th e c o n v e r t i o n .
6. Conclus ions
W i t h t h e f o r e g o i n g d i s c u s s i o n o f t h e r e s u l t s, i t is c o n -
c l u d e d t h a t t h e t e c h n o l o g y o f m a n u f a c t u r i n g s e a m le s s,
l o n g , t h in - w a l l t u b e s h a s b e e n d e v e l o p e d f o r s p e c if i c
u s a g e . T h e m a i n f e a t u r e o f t h e t e c h n o l o g y a r e a s f o ll o w s .
(1 ) T h e m e c h a n i c a l p r o p e r t i e s o f t h e s h e a r s p u n t u b e
i m p r o v e c o n s i d e r a b l y .
(2 ) A t o t a l r e d u c t i o n o f 8 0 % c a n b e a c h i e v e d w i t h o u t
i n t e r m e d i a t e a n n e a l i n g . T h e r e d u c t i o n is , h o w e v e r , a c h -
i eved i n s eve r a l pas ses .
(3 ) C o o l a n t a n d l u b r i c a n t s a r e n e c e s s a ry f o r i m p r o v -
i n g t h e f i n i s h , a n d t o c a r r y a w a y t h e h e a t g e n e r a t e d
d u r i n g t h e p r o c e s s . D i f f e r e n t l u b r i c a n t s d o n o t h a v e s i g -
n i f ic a n t ef fe c ts o n t h e p o w e r c o n s u m p t i o n , t h u s a n y
g o o d - q u a l i t y g r e a s e c a n b e u s e d in a d d i t i o n t o t h e c o o l -
an t .
( 4 ) T h e d i m e n s i o n a l t o l e r a n c e s b o t h o n t h e o u t s i d e
a n d t h e i n si d e d i a m e t e r o f t h e s p u n t u b e a r e b e t t e r t h a n
t h o s e a c h i e v e d b y a n y o t h e r t u b e - m a k i n g p r o c e s s , a n d
t h e c o n c e n t r i c it y is w i t h in c o m m e r c i a l l y - a c c e p t a b l e
l imi t s .
Ac kno w l e dg e me nt s
T h e s e c o n d a u t h o r is g ra t e fu l t o t h e D i r e c t o r , N P L , f o r
p e r m i s s i o n t o p r e s e n t t h i s p a p e r . H e i s g r a t e f u l t o t h e l a te
D r . B . K . A g g a r w a l a , E x - d e p u t y D i r e c to r , N P L , N e w
D e l h i f o r h i s g u i d a n c e . H e w o u l d a l s o l i k e t o p l a c e o n
r e c o r d t h e h e l p r e n d e r e d b y s e v e r a l c o l l ea g u e s w o r k i n g i n
t h e w o r k s h o p , d e s i g n o f f ic e a n d m e t a l f o r m i n g s e c t i o n s o f
N P L . T h e a u t h o r s a r e th a n k f u l t o U N D P f o r p r o v i d in g
t h e s p in n i n g m a c h i n e f o r N P L , w i t h o u t w h i c h t h i s w o r k
w o u l d n o t h a v e b e e n p o s s i bl e .
References
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workin g forces, B u l l . J S ME , 22 (167) (1979) 776-784.
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