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Use of manganese sulphide in PM applications
PM
CRACK INITIATION AND GROWTH IN POROUS LIQUID PHASE S I N T E R E D IRON-PHOSPHORUS ALLOYS
H~]. Rack et al, (Clemson Univ, USA). A model for crack initiation a n d growth in porous liquid p h a s e sintered Fe-P alloys was presented. The model was developed from microstructural and property evidence. Crack initiation was found to be associated with residual pores. The second stage involved a n increase in t h e n u m b e r of cracked pores a n d increased plastic strain. Final failure was associated with joining u p of t h e cracks. It was suggested t h a t increase in ductility of s i n t e r e d Fe-P alloys can be a t t a i n e d t h r o u g h pore s h a p e control a n d prior powder particle bonding. MECHANICAL R E S P O N S E OF SURFACE AUSROLLED S I N T E R E D S T E E L
R . ~ Queeney et al, (Pennsylvania State Univ, USA). The application of surface ausrolling to s i n t e r e d 4680 steel was r e p o r t e d . Rea u s t e n i t i z a t i o n of t h e steel resulted in a reduction in porosity from 15% to 6% a n d t h e ausrolling of t h e m e t a s t a b l e a u s t e n i t e r e d u c e d t h e p o r o s i t y to less t h a n 1%. E n h a n c e m e n t of m e c h a n i c a l p r o p e r t i e s w a s r e l a t e d to t h e t h e r m o m e c h a n i c a l t r e a t m e n t given to t h e steel. The objective was to use ausrolling to s h a p e gear t e e t h to reduce machining. IMPROVEMENTS IN THE CORROSION RESISTANCE OF PM STAINLESS STEELS
I(,H. Moyer a n d W. Jones, (Magna-Tech PM Laboratories, USA). The p a p e r described c h a n g e s in the p r o c e s s i n g of PM s t a i n l e s s steel w h i c h r e s u l t e d in i m p r o v e d c o r r o s i o n a n d mechanical properties. High t e m p e r a t u r e sintering in H has given greater d e n s i f i c a t i o n a n d lower c o n t a m i n a t i o n f r o m C, N, S a n d O. T h e i m p r o v e d properties were discussed and the commercial significance was considered. DENSIFICATION OF IRON-HIGH CARBON MIXED POWDERS BY ROTARY COLD SWAGING AT LOW TEMPERATURES
A. Kobylanski et al, (Ecole National Superlure des Mines, Paris, France). The use of rotary swaging (RS) was reviewed a n d it was suggested t h a t HIP could be used for t h e consolidation of long cylindrical bars. Plastic flow of m e t a l s in h a m m e r swaging was i n v e s t i g a t e d a n d c o m p u t e r modelled. It was f o u n d t h a t h a m m e r r o t a t i o n a n d m a c h i n e geometry result in a large c o m p o n e n t of torsional strain. RS at 7000°C was applied to p u r e Fe powder a n d to a Fe-0.9%C-1%Mn mixed p o w d e r enclosed in a i r t i g h t c o n t a i n e r s . Complete densification was a t t a i n e d after
LITERATURE
REVIEW
a few swaging passes. The torsional strains in RS generate additional frictional forces which contribute to densification. P r o c e s s i n g a t low t e m p e r a t u r e r e t a i n s original particle composition a n d enables a dual p h a s e microstrncture, with good mechanical properties, to be obtained. PROBLEM OF MECHANICAL RELIABILITY OF PM S T E E L S
A. Molinari et al, (Univ of Trento, Italy). The mechanical reliability of PM steel p a r t s w a s d i s c u s s e d w i t h r e g a r d to p e r f o r m a n c e criteria. It was n o t e d t h a t pores play a significant p a r t in fracture by acting as stress c o n c e n t r a t o r s a n d t h a t t h e fracture of PM steels often show evidence of plastic deformation. In this study statistical analysis, applied to t h e reliability of PM steels, has been improved by the establishment of a more suitable e s t i m a t o r a n d set size. The results were applied to austenitic stainless a n d ferritic/ pearlitic steels. CONSIDERATION OF INCOMPLETE DENSIFICATION OF VACUUM S I N T E R E D FINE CARBONYL IRON POWDER
K. Hayashi and T-W. Lim, (Univ of Tokyo, Tokyo, J a p a n ) . Research into t h e densification of fine c a r b o n y l Fe p o w d e r d u r i n g v a c u u m sintering a n d t h e effects of additions of A1, Nb, Mn, Mo, Cr, Ti, V a n d W were reported. The iron was found to densify only to 94% b u t additions of Al, Nb, Ti, V or use of a n Fe powder with a low C c o n t e n t resulted in complete densification. It was suggested t h a t the incomplete densification was due to oxidation of C by oxide impurities in t h e Fe powder. MACHINABILITY OF SINTERED STAINLESS STEEL
H.D. Ambs, (SCM Metal P r o d u c t s Inc, Cleveland, Ohio, USA) Drilling e x p e r i m e n t s on 303, 304 a n d 316 stainless steel were described. The influence of density a n d m i c r o s t r u c t u r e on machinability were considered. Interstitial impurities C, N a n d O were t a k e n into account. Recommendations for m a x i m i z a t i o n of machinability were made. USE OF MANGANESE SULPHIDE IN PM APPLICATIONS
D.S. Madan, (Elkem Development Center, Pittsburg, Pennsylvania, USA). Machinability a n d t h e use a n d role of MnS in e n h a n c i n g t h e machinability of PM steels was discussed. E x p e r i m e n t s on the effects of MnS a n d s t r u c t u r e / p r o p e r t y relationships on t h e m a c h i n a b i l i t y of steels were described. Mechanical properties were m e a s u r e d a n d machinability was assessed by drilling for a n u m b e r of alloys. The role of
MnS in e n h a n c i n g the m a c h i n a b i l i t y of steel was verified. E F F E C T S OF MANGANESE SULPHIDE PARTICLE SIZE ON THE FRACTURE P R O P E R T I E S OF LOW ALLOY STEEL
Y.T. Chen, (Pitney Bowes, Stamford, Connecticut, USA) Fracture t o u g h n e s s (F]') a n d transverse r u p t u r e s t r e n g t h (TRS) of a PM steel, R3755, containing MnS in t h e range 0.55 to 0.95% were investigated with respect to MnS particle size, in t h e range of 5 to 40 ~t. Microstructure a n d fracture analysis were used to verify a p r o p o s e d fracture analysis were used to verify a p r o p o s e d fracture model and optimum conditions for p r o d u c t i o n of a free cutting low alloy steel were established. CHARACTERISTICS OF A NEW SINTERHARDENING LOW ALLOY STEEL
R.J. C a u s t o n et al, ( H o e g a n a e s Corp, Riverton, New Jersey, USA). Sinter-hardening, which occurs w h e n a sufficiently fast cooling r a t e from t h e sintering furnace is used, was reviewed a n d some steels w h i c h are c a p a b l e of s i n t e r - h a r d e n i n g w e r e c o n s i d e r e d . The effect of" cooling rates of s t r u c t u r e a n d tensile, i m p a c t a n d fatigue properties of selected steels were reported. CHARACTERISTICS OF ATOMIZED IRON POWDER WITH HIGH COMPRESSIBILTIY AND IMPROVED COMPACTIBILITY
S. Saito et al, ( K a w a s a k i Steel Corp, Kawasaki, J a p a n ) The development of a high compressibility atomized Fe powder with improved compactibility was described. The i m p r o v e m e n t s were o b t a i n e d by control of particle shape, size a n d size d i s t r i b u t i o n a n d i m p u r i t y levels by optimization of the process conditions. When c o m p a c t e d with 1% Zn s t e a r a t e at pressure of 490 MPa a green density of 7.05 g/cm 3, 0.14 g/cm 3 higher t h a n with conventional atomized powder, was attained. Ejection force was 15% lower. DEVELOPMENT OF WEAR RESISTANT HYPEREUTECTOID F E R R O U S MATERIALS WITH GOOD S I N T E R E D STRENGTH
A~F. deRege a n d L.F. Pease, (Domfer Metal Products Ltd, USA). Wear resistance tests and other m e c h a n i c a l property tests were carried out on high carbon steels as a function of %C. At high C c o n t e n t s good wear resistance was reported. Optical and electron m i c r o s c o p y w e r e u s e d to i n v e s t i g a t e carbide morphology a n d d i s t r i b u t i o n a n d a n e x p l a n a t i o n of t h e p r o p e r t y levels was given.
MPR September 1991 71
CRACK INITIATION AND GROWTH IN POROUS LIQUID PHASE S I N T E R E D IRON-PHOSPHORUS ALLOYS
H~]. Rack et al, (Clemson Univ, USA). A model for crack initiation a n d growth in porous liquid p h a s e sintered Fe-P alloys was presented. The model was developed from microstructural and property evidence. Crack initiation was found to be associated with residual pores. The second stage involved a n increase in t h e n u m b e r of cracked pores a n d increased plastic strain. Final failure was associated with joining u p of t h e cracks. It was suggested t h a t increase in ductility of s i n t e r e d Fe-P alloys can be a t t a i n e d t h r o u g h pore s h a p e control a n d prior powder particle bonding. MECHANICAL R E S P O N S E OF SURFACE AUSROLLED S I N T E R E D S T E E L
R . ~ Queeney et al, (Pennsylvania State Univ, USA). The application of surface ausrolling to s i n t e r e d 4680 steel was r e p o r t e d . Rea u s t e n i t i z a t i o n of t h e steel resulted in a reduction in porosity from 15% to 6% a n d t h e ausrolling of t h e m e t a s t a b l e a u s t e n i t e r e d u c e d t h e p o r o s i t y to less t h a n 1%. E n h a n c e m e n t of m e c h a n i c a l p r o p e r t i e s w a s r e l a t e d to t h e t h e r m o m e c h a n i c a l t r e a t m e n t given to t h e steel. The objective was to use ausrolling to s h a p e gear t e e t h to reduce machining. IMPROVEMENTS IN THE CORROSION RESISTANCE OF PM STAINLESS STEELS
I(,H. Moyer a n d W. Jones, (Magna-Tech PM Laboratories, USA). The p a p e r described c h a n g e s in the p r o c e s s i n g of PM s t a i n l e s s steel w h i c h r e s u l t e d in i m p r o v e d c o r r o s i o n a n d mechanical properties. High t e m p e r a t u r e sintering in H has given greater d e n s i f i c a t i o n a n d lower c o n t a m i n a t i o n f r o m C, N, S a n d O. T h e i m p r o v e d properties were discussed and the commercial significance was considered. DENSIFICATION OF IRON-HIGH CARBON MIXED POWDERS BY ROTARY COLD SWAGING AT LOW TEMPERATURES
A. Kobylanski et al, (Ecole National Superlure des Mines, Paris, France). The use of rotary swaging (RS) was reviewed a n d it was suggested t h a t HIP could be used for t h e consolidation of long cylindrical bars. Plastic flow of m e t a l s in h a m m e r swaging was i n v e s t i g a t e d a n d c o m p u t e r modelled. It was f o u n d t h a t h a m m e r r o t a t i o n a n d m a c h i n e geometry result in a large c o m p o n e n t of torsional strain. RS at 7000°C was applied to p u r e Fe powder a n d to a Fe-0.9%C-1%Mn mixed p o w d e r enclosed in a i r t i g h t c o n t a i n e r s . Complete densification was a t t a i n e d after
LITERATURE
REVIEW
a few swaging passes. The torsional strains in RS generate additional frictional forces which contribute to densification. P r o c e s s i n g a t low t e m p e r a t u r e r e t a i n s original particle composition a n d enables a dual p h a s e microstrncture, with good mechanical properties, to be obtained. PROBLEM OF MECHANICAL RELIABILITY OF PM S T E E L S
A. Molinari et al, (Univ of Trento, Italy). The mechanical reliability of PM steel p a r t s w a s d i s c u s s e d w i t h r e g a r d to p e r f o r m a n c e criteria. It was n o t e d t h a t pores play a significant p a r t in fracture by acting as stress c o n c e n t r a t o r s a n d t h a t t h e fracture of PM steels often show evidence of plastic deformation. In this study statistical analysis, applied to t h e reliability of PM steels, has been improved by the establishment of a more suitable e s t i m a t o r a n d set size. The results were applied to austenitic stainless a n d ferritic/ pearlitic steels. CONSIDERATION OF INCOMPLETE DENSIFICATION OF VACUUM S I N T E R E D FINE CARBONYL IRON POWDER
K. Hayashi and T-W. Lim, (Univ of Tokyo, Tokyo, J a p a n ) . Research into t h e densification of fine c a r b o n y l Fe p o w d e r d u r i n g v a c u u m sintering a n d t h e effects of additions of A1, Nb, Mn, Mo, Cr, Ti, V a n d W were reported. The iron was found to densify only to 94% b u t additions of Al, Nb, Ti, V or use of a n Fe powder with a low C c o n t e n t resulted in complete densification. It was suggested t h a t the incomplete densification was due to oxidation of C by oxide impurities in t h e Fe powder. MACHINABILITY OF SINTERED STAINLESS STEEL
H.D. Ambs, (SCM Metal P r o d u c t s Inc, Cleveland, Ohio, USA) Drilling e x p e r i m e n t s on 303, 304 a n d 316 stainless steel were described. The influence of density a n d m i c r o s t r u c t u r e on machinability were considered. Interstitial impurities C, N a n d O were t a k e n into account. Recommendations for m a x i m i z a t i o n of machinability were made. USE OF MANGANESE SULPHIDE IN PM APPLICATIONS
D.S. Madan, (Elkem Development Center, Pittsburg, Pennsylvania, USA). Machinability a n d t h e use a n d role of MnS in e n h a n c i n g t h e machinability of PM steels was discussed. E x p e r i m e n t s on the effects of MnS a n d s t r u c t u r e / p r o p e r t y relationships on t h e m a c h i n a b i l i t y of steels were described. Mechanical properties were m e a s u r e d a n d machinability was assessed by drilling for a n u m b e r of alloys. The role of
MnS in e n h a n c i n g the m a c h i n a b i l i t y of steel was verified. E F F E C T S OF MANGANESE SULPHIDE PARTICLE SIZE ON THE FRACTURE P R O P E R T I E S OF LOW ALLOY STEEL
Y.T. Chen, (Pitney Bowes, Stamford, Connecticut, USA) Fracture t o u g h n e s s (F]') a n d transverse r u p t u r e s t r e n g t h (TRS) of a PM steel, R3755, containing MnS in t h e range 0.55 to 0.95% were investigated with respect to MnS particle size, in t h e range of 5 to 40 ~t. Microstructure a n d fracture analysis were used to verify a p r o p o s e d fracture analysis were used to verify a p r o p o s e d fracture model and optimum conditions for p r o d u c t i o n of a free cutting low alloy steel were established. CHARACTERISTICS OF A NEW SINTERHARDENING LOW ALLOY STEEL
R.J. C a u s t o n et al, ( H o e g a n a e s Corp, Riverton, New Jersey, USA). Sinter-hardening, which occurs w h e n a sufficiently fast cooling r a t e from t h e sintering furnace is used, was reviewed a n d some steels w h i c h are c a p a b l e of s i n t e r - h a r d e n i n g w e r e c o n s i d e r e d . The effect of" cooling rates of s t r u c t u r e a n d tensile, i m p a c t a n d fatigue properties of selected steels were reported. CHARACTERISTICS OF ATOMIZED IRON POWDER WITH HIGH COMPRESSIBILTIY AND IMPROVED COMPACTIBILITY
S. Saito et al, ( K a w a s a k i Steel Corp, Kawasaki, J a p a n ) The development of a high compressibility atomized Fe powder with improved compactibility was described. The i m p r o v e m e n t s were o b t a i n e d by control of particle shape, size a n d size d i s t r i b u t i o n a n d i m p u r i t y levels by optimization of the process conditions. When c o m p a c t e d with 1% Zn s t e a r a t e at pressure of 490 MPa a green density of 7.05 g/cm 3, 0.14 g/cm 3 higher t h a n with conventional atomized powder, was attained. Ejection force was 15% lower. DEVELOPMENT OF WEAR RESISTANT HYPEREUTECTOID F E R R O U S MATERIALS WITH GOOD S I N T E R E D STRENGTH
A~F. deRege a n d L.F. Pease, (Domfer Metal Products Ltd, USA). Wear resistance tests and other m e c h a n i c a l property tests were carried out on high carbon steels as a function of %C. At high C c o n t e n t s good wear resistance was reported. Optical and electron m i c r o s c o p y w e r e u s e d to i n v e s t i g a t e carbide morphology a n d d i s t r i b u t i o n a n d a n e x p l a n a t i o n of t h e p r o p e r t y levels was given.
MPR September 1991 71