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Low alloy car parts high temperature sintered
PM
SPECIAL
FEATURE
Low alloy car parts high temperature sintered Ferrous Pill p a r t s f o r high performance applications in cars n e e d greater strength than conventional steel sintered components. High temperature sintering on its own does not achieve this strength says Tokyo Sintered Metals Corp. The Japanese company s e t out to develop a technique which combined heat treatment with high temperature sintering. Kazuo Shimada explains.
errous sintered parts play an important role in automotive applications. In Japan the car industry consumes more than 80% of the total production of these components. But conventional ferrous sintered parts lack the static and fatigue strengths, and the wear resistance of components made of machined wrought steel or nodular cast iron. To obtain these improved properties, Tokyo Sintered Metals considered sintering
F
FIGURE 1: Tensile strength as a function of sintered density; alloy powders type A, B, B' and C.
1600
I I
I
i
1500
1400
i i
J
!
~
i .
!
: :
/
c/ /!
1300 =
!
1200
i
m
i F
i
~
i
1100
....... A
m
1000 , ,..~ . ~,?y,,Iz/,.,:,H,m,
, .Xl/., % .
. .,~,//////2~ z//A V,,~ ~/,, ? 2 ~/~
.............................
......
900
Y
800
Conventional Sintered Steel
700 ]
E
600
J
6.8
6.9
7.0
7.1
7.2
Density (g/cm 3) 24 MPR September 1992
7.3
7,4
40
!
B '
30
25
:eel
_E
6.8
6.9
7.0
7.1
7.2
7.3
7.4
Density (g/crn 3)
FIGURE 2: Impact energy as a function of sintered density; alloy powders type A, B, B' and C.
at a high temperature. However, it was impossible to obtain the target specifications by using ordinary high temperature sintered materials. Therefore, we were obliged to develop a new technology. In the early stages of development ferrous sintered material with similar properties to those of bearing steel and nodular cast iron were required. These were used to replace conventional components i.e. rotor and cam rings of vane type oil pumps in a power steering system. The t a r g e t level for fatigue s t r e n g t h was 350 MPa ( u n n o t c h e d ) . The cam ring, which has to have a long life, required superior wear resistance to nodular cast iron ring. The high compressibility low alloy steel powders used were: a partially prealloyed steel powder, HSgan~s Distaloy AE, (Type A) and a water atomized 4100 alloy steel powder (Type B), Kawasaki Steel's 4100V. Specimens were pressed in steel dies at a pressure of 490 to 686 MPa. Sintering was carried out at 1250°C for 1 hour in a pusher type furnace, in a nitrogen based atmosphere (S vol% hydrogen). All the sintered specimens were carburized at 900°C for 2.5 hours, then q u e n c h e d in oil and tempered at 180°C for 1 hour. Both the tensile strength and the impact
strength increased with the increase in sintered density, as shown in Figures 1 and 2. Type A powder was superior to Type B powder and a significant improvement was observed c o m p a r e d with conventional Fe-2%Ni compacts sintered at 1150°C. The results of the fatigue tests are shown in Figure 3. The unnotched fatigue endurance limits of both Type A and Type B powders were over 350 MPa, the target level of development. The relationship between the tensile strength and the fatigue strength of these powders is shown in Figure 4. The fatigue strength of Type A powder was comparable with t h a t of heat-treated alloy steels. The results of the rotary wear tests by a block-on-disk abrasive wear test machine are shown in Figure 5. Wear resistance of Type B powder was superior to Type A powder, and t h a t of both powders was much better t h a n the wear resistance of nodular cast iron. There was a further requirement for improving the properties of Type B powder. To investigate this the h e a t - t r e a t m e n t procedure was modified by eliminating the carburizing process. Type B (4100V) powder was m i x e d with 0.5% of g r a p h i t e powder, and the mixure was compacted to 687 MPa. Sintering was carried out at 1250°C in a nitrogen base (8 vol% hydrogen) a t m o s p h e r e and subsequent heatt r e a t m e n t was p e r f o r m e d at 850°C in v a c u u m , t h e n q u e n c h e d into oil a n d tempered at 180°C for 1 hour.
Unnotched
500 v
i
a.
4OO
u)
"",
NM~C~Vo.
~/
i
Conventional
i
"',. ~,_,. . .Sintered ! . . . . . . . .Steel . . . . ~-..~ I
3OO
I
107
106
108
Number of Cycles to Failure FIGURE 3: S-N response of unnotched sintered type A and type B alloy
powders. 600
I
Alloy Alloy Steel Steel n
I
500
--v
:E
v
r-
e-
4OO
cO
I
v,~
.... ~
---
C
== 300
FIGURE 5: Wear response of alloy powders
type A, B, B', C and nodular cast iron block-ondisk test.
T
m m
200
~~
ConventionalSinteredsteel I I i
100 400
~ . . 'WroughtCarbonSteel "//~//~ (headitmated)
600
800
1000
1200
1400
1600
Tensile Strength (MPa) FIGURE 4: Relationship between tensile strength and fatigue strength; alloy
powders type A, B, B' and C. X
I,
..° oO°
i 10 5O Running "Rme (h) saclv~,,=e~ : a.Tum/= Load
Temperature ekaf~e ro~hnum han~mm= 8urlm~ r a m
:118N • Power ~ m . t n ¢ g~d : 8--28"C : 0~0-0.22pmRz :Ama~ : HRC (1~ : 0.34~mR=
100
The results are shown in Figures 1, 2, 4 and 5 as Type B' powder. The mean tensile strength and i m p a c t strength were increased to values similar to those of Type A powder. Wear resistance of Type B' powder was also improved compared with B powder. Finally high t e m p e r a t u r e sintering of Type C powder was developed to increase t h e t o u g h n e s s of s i n t e r e d p a r t s . The nominal composition of Type C powder was Fe-7%Ni-2.5%Cu-l%Mo-0.7%C, Type A powder (Distaloy AE) was m i x e d with ternary alloy (60%Ni-25%Cu-9%Mo) and 0.7% graphite powder's and compacted at up to 687 MPa, then vacuum sintered at MPR September 1992 2 5
PM
SPECIAL
FEATURE
1250°C. As shown in Figures 1 a n d 2, t h e h i g h e s t m e a n values of tensile strength and i m p a c t s t r e n g t h w e r e obtained without heat-treatment. Superior wear resistance was also obtained as shown in Figure 5. As a result of experiments, Type A powder was used to fabricate a rotor and cam ring (Figure 6a) of a vane-type oil p u m p in a power steering system. The cost reduction by introducing both sintered p a r t s made of Type A powder w a s e s t i m a t e d to be 30% compared with conventional parts. Later, Type B and Type B' powders were used for the cam ring because of the better wear resistance they provided and theirlower powder prices. FIGURE 6: Tokyo Sintered Metal's rotor and cam (middle left), shift lever (top), shutter (bottom) and gear (middle right).. Other high temperature sintered parts m a d e using Type A powder include: • a manual transmission shiftlevel,shown in Figure 6b, which replaced a forged wrought steel component; • a s h u t t e r used in a d a m p i n g force control shock absorber, shown in Figure 6c. This p a r t controls oil flow of a shock FOR REGULAR UPDATES ON THE absorber system. A half-collar part was LATEST DEVELOPMENTS IN ALL successfully fabricated which had the required strength and toughness; and A R E A S OF ADVANCED • a gear for angle adjusting of an external MATERIALS mirror, shown in Figure 6d, was fabricated by using Type C powder. The sizing SEND FOR YOUR F R E E ADVANCED MATERIALS process could be eliminated by precise T EC HN O LO G Y INFORMATION PACK N O W control of dimensional change during sintering. In this case the required PHONE: +44 (0) 865 512242 impact strength was achieved. High static strength, high impact resistance, FAX: +44 (0) 865 310981 high fatigue strength and wear resistant ferrous sintered parts for cars have been or write to: developed using a high t e m p e r a t u r e sintering technique with or without heat-treatElsevier Advanced Technology, Meyfleld House, m e n t (i.e. carburizing, q u e n c h i n g and 256 Banbury Road, Oxford, OX2 7DH, UK tempering) using high compressibility low alloy steel powders. These ferrous sintered p a r t s replaced conventional bearing steel and nodular cast iron components. At present, the production of automotive parts using this process is about 150 tonnes per month; nearly 25% of the total ferrous sintered parts fabricated at Tokyo Sintered Metals Corp. In the near future, demand for reduction in the weight of cars will become critical, a n d s m a l l e r p a r t s with t h i n n e r cross sections will be required, therefore further improvement of properties is underway. For such applications high t e m p e r a t u r e sintering will be a key technology.
!LIII
26 MPR September 1992
SPECIAL
FEATURE
Low alloy car parts high temperature sintered Ferrous Pill p a r t s f o r high performance applications in cars n e e d greater strength than conventional steel sintered components. High temperature sintering on its own does not achieve this strength says Tokyo Sintered Metals Corp. The Japanese company s e t out to develop a technique which combined heat treatment with high temperature sintering. Kazuo Shimada explains.
errous sintered parts play an important role in automotive applications. In Japan the car industry consumes more than 80% of the total production of these components. But conventional ferrous sintered parts lack the static and fatigue strengths, and the wear resistance of components made of machined wrought steel or nodular cast iron. To obtain these improved properties, Tokyo Sintered Metals considered sintering
F
FIGURE 1: Tensile strength as a function of sintered density; alloy powders type A, B, B' and C.
1600
I I
I
i
1500
1400
i i
J
!
~
i .
!
: :
/
c/ /!
1300 =
!
1200
i
m
i F
i
~
i
1100
....... A
m
1000 , ,..~ . ~,?y,,Iz/,.,:,H,m,
, .Xl/., % .
. .,~,//////2~ z//A V,,~ ~/,, ? 2 ~/~
.............................
......
900
Y
800
Conventional Sintered Steel
700 ]
E
600
J
6.8
6.9
7.0
7.1
7.2
Density (g/cm 3) 24 MPR September 1992
7.3
7,4
40
!
B '
30
25
:eel
_E
6.8
6.9
7.0
7.1
7.2
7.3
7.4
Density (g/crn 3)
FIGURE 2: Impact energy as a function of sintered density; alloy powders type A, B, B' and C.
at a high temperature. However, it was impossible to obtain the target specifications by using ordinary high temperature sintered materials. Therefore, we were obliged to develop a new technology. In the early stages of development ferrous sintered material with similar properties to those of bearing steel and nodular cast iron were required. These were used to replace conventional components i.e. rotor and cam rings of vane type oil pumps in a power steering system. The t a r g e t level for fatigue s t r e n g t h was 350 MPa ( u n n o t c h e d ) . The cam ring, which has to have a long life, required superior wear resistance to nodular cast iron ring. The high compressibility low alloy steel powders used were: a partially prealloyed steel powder, HSgan~s Distaloy AE, (Type A) and a water atomized 4100 alloy steel powder (Type B), Kawasaki Steel's 4100V. Specimens were pressed in steel dies at a pressure of 490 to 686 MPa. Sintering was carried out at 1250°C for 1 hour in a pusher type furnace, in a nitrogen based atmosphere (S vol% hydrogen). All the sintered specimens were carburized at 900°C for 2.5 hours, then q u e n c h e d in oil and tempered at 180°C for 1 hour. Both the tensile strength and the impact
strength increased with the increase in sintered density, as shown in Figures 1 and 2. Type A powder was superior to Type B powder and a significant improvement was observed c o m p a r e d with conventional Fe-2%Ni compacts sintered at 1150°C. The results of the fatigue tests are shown in Figure 3. The unnotched fatigue endurance limits of both Type A and Type B powders were over 350 MPa, the target level of development. The relationship between the tensile strength and the fatigue strength of these powders is shown in Figure 4. The fatigue strength of Type A powder was comparable with t h a t of heat-treated alloy steels. The results of the rotary wear tests by a block-on-disk abrasive wear test machine are shown in Figure 5. Wear resistance of Type B powder was superior to Type A powder, and t h a t of both powders was much better t h a n the wear resistance of nodular cast iron. There was a further requirement for improving the properties of Type B powder. To investigate this the h e a t - t r e a t m e n t procedure was modified by eliminating the carburizing process. Type B (4100V) powder was m i x e d with 0.5% of g r a p h i t e powder, and the mixure was compacted to 687 MPa. Sintering was carried out at 1250°C in a nitrogen base (8 vol% hydrogen) a t m o s p h e r e and subsequent heatt r e a t m e n t was p e r f o r m e d at 850°C in v a c u u m , t h e n q u e n c h e d into oil a n d tempered at 180°C for 1 hour.
Unnotched
500 v
i
a.
4OO
u)
"",
NM~C~Vo.
~/
i
Conventional
i
"',. ~,_,. . .Sintered ! . . . . . . . .Steel . . . . ~-..~ I
3OO
I
107
106
108
Number of Cycles to Failure FIGURE 3: S-N response of unnotched sintered type A and type B alloy
powders. 600
I
Alloy Alloy Steel Steel n
I
500
--v
:E
v
r-
e-
4OO
cO
I
v,~
.... ~
---
C
== 300
FIGURE 5: Wear response of alloy powders
type A, B, B', C and nodular cast iron block-ondisk test.
T
m m
200
~~
ConventionalSinteredsteel I I i
100 400
~ . . 'WroughtCarbonSteel "//~//~ (headitmated)
600
800
1000
1200
1400
1600
Tensile Strength (MPa) FIGURE 4: Relationship between tensile strength and fatigue strength; alloy
powders type A, B, B' and C. X
I,
..° oO°
i 10 5O Running "Rme (h) saclv~,,=e~ : a.Tum/= Load
Temperature ekaf~e ro~hnum han~mm= 8urlm~ r a m
:118N • Power ~ m . t n ¢ g~d : 8--28"C : 0~0-0.22pmRz :Ama~ : HRC (1~ : 0.34~mR=
100
The results are shown in Figures 1, 2, 4 and 5 as Type B' powder. The mean tensile strength and i m p a c t strength were increased to values similar to those of Type A powder. Wear resistance of Type B' powder was also improved compared with B powder. Finally high t e m p e r a t u r e sintering of Type C powder was developed to increase t h e t o u g h n e s s of s i n t e r e d p a r t s . The nominal composition of Type C powder was Fe-7%Ni-2.5%Cu-l%Mo-0.7%C, Type A powder (Distaloy AE) was m i x e d with ternary alloy (60%Ni-25%Cu-9%Mo) and 0.7% graphite powder's and compacted at up to 687 MPa, then vacuum sintered at MPR September 1992 2 5
PM
SPECIAL
FEATURE
1250°C. As shown in Figures 1 a n d 2, t h e h i g h e s t m e a n values of tensile strength and i m p a c t s t r e n g t h w e r e obtained without heat-treatment. Superior wear resistance was also obtained as shown in Figure 5. As a result of experiments, Type A powder was used to fabricate a rotor and cam ring (Figure 6a) of a vane-type oil p u m p in a power steering system. The cost reduction by introducing both sintered p a r t s made of Type A powder w a s e s t i m a t e d to be 30% compared with conventional parts. Later, Type B and Type B' powders were used for the cam ring because of the better wear resistance they provided and theirlower powder prices. FIGURE 6: Tokyo Sintered Metal's rotor and cam (middle left), shift lever (top), shutter (bottom) and gear (middle right).. Other high temperature sintered parts m a d e using Type A powder include: • a manual transmission shiftlevel,shown in Figure 6b, which replaced a forged wrought steel component; • a s h u t t e r used in a d a m p i n g force control shock absorber, shown in Figure 6c. This p a r t controls oil flow of a shock FOR REGULAR UPDATES ON THE absorber system. A half-collar part was LATEST DEVELOPMENTS IN ALL successfully fabricated which had the required strength and toughness; and A R E A S OF ADVANCED • a gear for angle adjusting of an external MATERIALS mirror, shown in Figure 6d, was fabricated by using Type C powder. The sizing SEND FOR YOUR F R E E ADVANCED MATERIALS process could be eliminated by precise T EC HN O LO G Y INFORMATION PACK N O W control of dimensional change during sintering. In this case the required PHONE: +44 (0) 865 512242 impact strength was achieved. High static strength, high impact resistance, FAX: +44 (0) 865 310981 high fatigue strength and wear resistant ferrous sintered parts for cars have been or write to: developed using a high t e m p e r a t u r e sintering technique with or without heat-treatElsevier Advanced Technology, Meyfleld House, m e n t (i.e. carburizing, q u e n c h i n g and 256 Banbury Road, Oxford, OX2 7DH, UK tempering) using high compressibility low alloy steel powders. These ferrous sintered p a r t s replaced conventional bearing steel and nodular cast iron components. At present, the production of automotive parts using this process is about 150 tonnes per month; nearly 25% of the total ferrous sintered parts fabricated at Tokyo Sintered Metals Corp. In the near future, demand for reduction in the weight of cars will become critical, a n d s m a l l e r p a r t s with t h i n n e r cross sections will be required, therefore further improvement of properties is underway. For such applications high t e m p e r a t u r e sintering will be a key technology.
!LIII
26 MPR September 1992