- Email: [email protected]
Japanese PM Industry showcases rich new products and design
in business
Japanese PM Industry showcases rich new products and design The Japan Powder Metallurgy Association (JPMA) exhibit much to be positive about in the Japanese PM industry, as their report on 2007 paints a picture of confidence and innovation, says Rob Stringer.
T
he JPMA report on 2007 gives an account of PM production and powder shipments, before presenting the winning developments in design, material, new powders and innovation from the JPMA awards last year. Despite some slight decreases, total volume of Japanese PM production in 2007 was up overall, with a strong 4 per cent increase on the previous year at 121 153 tonnes. Broken down into types of goods manufactured, total production of bearings was 7 954 tonnes – slipping to 99.9 per cent of the previous year’s total while electric contacts had fallen further to 93.9 per cent with 93 tonnes. Production of machine parts, however, was up 4.3 per cent from 2006 at 110 665 tonnes, while friction materials shot up 8.5 per cent to 788 tonnes. Production of other components also rose with a 6.3 per cent increase on the previous year to 1 653 tonnes. Production volume of Japanese machine parts in 2007 (Figure 1) continued trends of positive growth for the sixth consecutive year, as well as maintaining record high volumes for five consecutive years. This is attributed to an economy kept strong by such factors as the export of vehicles. When compared to the same periods of the previous year, the quarterly trend demonstrated comprehensive growth of 3.4 per cent for January to March, 6.6 per cent for April to June, 1.9 per cent for July to September and 5.7 per cent for October to December. Total production sales amounted to ¥135 billion, a 5.9 per cent rise over the previous year.
8
MPR September 2008
Sintered parts remain to be predominantly manufactured for automobile usage, with production volume amounting to 101 386 tonnes – a 3.8 per cent increase on the
previous year. Vehicle parts accounted for 91.6 per cent of all machine parts, indicating a continued high dependence on the automobile industry.
Figure 1: Production of machine parts and bearings
0026-0657/08 ©2008 Elsevier Ltd. All rights reserved.
58.1 per cent of total production – a 3.1 per cent increase on the previous year. Other uses of bearings totalled 3 335 tonnes – a 7.2 per cent drop from the previous year, continuing a trend of decrease over three consecutive years.
Powder shipments
The sum of other machine parts not used in vehicles amounted to 9 280 tonnes, exhibiting the first increase in three years with a 10.3 per cent growth from the previous year. Assessments in the report for the total weight of sintered parts used in one car took their figures from 2006, when the total in Japan was 8.6 kg, 19.5 kg for the US and 9.3 kg in Europe. The figure is particularly high in the US because larger parts such as the connecting rod and bearing cap are already being sintered whereas in Japan, other production methods are currently being used. Consequently, the Japanese industry plans to follow their lead. Figure 2 illustrates production volume of sintered machine parts applied to respective sections of automobiles in 2006, based on a demand structure survey by the JPMA. 51.1 per cent were used in engine parts, slipping from 51.5 per cent the previous year; 24 per cent were for use in drive train parts, a decrease from 24.5 per cent in 2005, while a slight increase was seen in chassis parts, up from 14 per cent in 2005 to 14.2 per cent in 2006.
1.7 per cent and the final quarter, October to December, was up 3.7 per cent. Production sales amounted to ¥15.8 billion, an increase of 7.8 per cent on the previous year. An increase in the production of complicated products requiring high reliability was also seen. As with machine parts, the highest demand for bearings in 2007 was seen in the automobile industry. Production volume for vehicles was 4 620 tonnes, 5.7 per cent up on the previous year, and continued a trend of steady increase over four years. This included bearings for millers and door locks, which contributed
The report largely displayed strengthened figures for Japanese powder shipment in 2007. Iron powder shipments amounted to 228 624 tonnes in total, rising 2 per cent from the previous year. Among this, domestic shipment for PM use was 131 869 tonnes – a 3.9 per cent increase on the previous year. A rise of 6.8 per cent from 2006 was seen in copper powder shipments, totalling 8 939 tonnes. Shipments for PM use amounted to 6 691 tonnes – a 6.2 per cent growth on the previous year. Records for stainless steel shipments for PM usage in 2007 were not yet available but the report recalled strong growth of over 10 per cent every year from 2001 to 2004, while 2005 brought a lesser increase of 3.6 per cent at 4 718 tonnes, and 2006 saw a decrease of 3.2 per cent to 4 104 tonnes. Domestic shipment of MIM powder in 2006 was 507 tonnes, indicating a 20.7 per cent increase from 2005.
The JPMA awards 2007 A multitude of design developments were detailed in the JPMA report for 2007 with
Bearings The quarterly trend in Japanese production volume of bearings in 2007, when compared with the same period in the previous year, showed a 5.3 per cent fall from January to March, while April to June was up 0.2 per cent, July to September was up
10
MPR September 2008
Figure 2: Breakdown of machine parts for automobile (2007)
metal-powder.net
categories given to new designs, new materials, new powders and further innovation. Contributing to new designs, Sumitomo Electric Industries developed a 4WD part used for connecting the carrier of a high torque unit to a low torque output gear shaft. With high density and a complicated shape, the part has an outside spline on the flange, which is inserted into an internal spline of a carrier. The flange has nine
holes for weight reduction located near the boss. The boss has an internal spline, and an output gear shaft is inserted into this spline for torque transfer to an output shaft. The internal spline has a back taper for compaction in order to allow smooth insertion of this shaft. Using PM production, a 6 per cent weight reduction of the original forging design could be achieved.
Sumitomo PM sprocket and housing body for electro magnetic actuated VCT systems.
Guide plates from Porite for an overload clutch in a hammer drill.
12
MPR September 2008
Compaction without machining is attained by designing a compacting tool structure and an improved ejection process. The internal spline of the boss requires impact strength and hertzian fatigue strength which is achieved with a density of 7.0 g/cm3 minimum and induction hardening. The density of the compaction process is 6.9 g/cm3 due to the position of the internal spline. A back taper and density of over 7.0 g/cm3 is achieved through a sizing process. Sizing and material shape may be optimised through finite element analysis. Sumitomo Electric Industries also oversaw the development of “highly efficient PM internal gear pump rotors with newly developed teeth profiles”. These PM internal pump rotors are used in automotive oil pumps for engines, automatic transmissions, continuously variable transmissions and fuel feed pumps of diesel engines. Despite recent focus on the strong demand for low fuel consumption of automobiles, the energy loss of oil pumps is about 10 per cent while the energy loss of automatic transmission oil pumps is about 20-30 per cent. Customer demand for efficient oil-pumps is consequently strong. The energy loss of geared fuel pumps depends on friction loss influenced by the side face of rotors and the outside surface of an outer rotor. In order to reduce the loss, new teeth profiles have been developed to increase the theoretical discharge volume from the same diameter of an outer rotor. The conventional teeth profile of the inner rotor has one base circle. Displacement distance relating to the discharge volume is determined by the base circle and number of teeth. As the theoretical discharge volume depends on the displacement distance and one base circle, the newly developed inner rotor’s profile has two base circles to enlarge the displacement distance. The outer rotor profile is generated from that of the inner profile. The optimisation of the design parameters was carried out through theoretical calculation and by evaluating a sample test. The theoretical discharge volume of the newly developed internal rotors was 12% higher than that of the same sized conventional rotors. As long as the required actual discharge volume stays constant, the downsizing of the rotor as well as energy loss reduction can be achieved. This downsizing enables the drive torque
metal-powder.net
of a newly developed oil pump a 10% reduction compared with the original. Also from Sumitomo Electric Industries came the development of a PM sprocket combined with a housing body for electro magnetic actuated variable cam timing (VCT) systems. The VCT system is used for almost all new model vehicles and is generally actuated by the oil hydraulic system. However, due to recent market demands such as high engine performance, low fuel consumption and low emission, the electro magnetic actuated VCT was developed. The PM sprocket consists of a timing sprocket and a housing body. Due to the part’s complicated shape, the sprocket and housing are made separately by conventional processes and joined together with screw bolts. The housing sprocket is compacted in one compacting stroke. Mitsubishi Materials PMG Corporation developed sintered parts with multiple teeth for a steering tilt of an automobile, consisting of a tooth lock and two cams. These applications aim to increase the expansion and contraction of holding power, due to the connection mechanism of the gear which satisfies the collision safety level, in order to develop the new steering column. The system consists of tooth lock A, possessing 22 teeth, and cam A, which has an uneven surface. Form and flatness for the tooth lock were achieved through optimisation of the die form and rationalisation of the operation. Level precision and density equalisation of cam A were attained through die constitution such as unification of the upper punch and rationalisation of the operation. The result was that highly accurate mass production of a part with high intensity could be achieved. A guide plate for the overload clutch in a hammer drill was developed by the Porite Corporation. Due to its complex shape, the part was originally manufactured through metal injection moulding (MIM); consequently, the shape of the product was reviewed. The tooling structure was improved and the grooves were pressed by the same punch for accuracy of size. The eight grooves were increased to ten for dispersion of the groove load, and keyway was added to the inside for torque transmission. A machining process was added to keep the height accuracy of the groove. Product cost through PM production was cut by 40 per cent. The final new development in design was in long thin-walled helical gear parts
14
MPR September 2008
Hitachi connecting rods using sinter forged aluminium alloy.
Oil-impregnated sintered bearings from Mitsubishi applied in the flow regulating valve for gas in an exhaust gas recirculation unit.
with a non-regular shape on the inside, also from the Porite Corporation. The product is a planet gear for the gear box used to revolve the washing drum of an automatic washing machine. It has involute serration on the inside and a helical gear on the outside. In the past, the application was produced through broach processing on the inside and gear cutting on the outside. It can now be produced by powder metallurgy without post-processing. In order to attain product accuracy, the tooling structure, material and press work were reviewed. Density distribution between ups and downs was found to be 0.03-0.04 Mg/m3, runout accuracy was under 0.025 mm and helix deviation was JIS 2nd class. Also, the tolerance width to press in the resin bush was 0.08mm. Consequently, the long thin-wall complex shape such as in this product is now manufacturable. The section for developments in materials begins with Mitsubishi Materials PMG
Corporation for their powder magnetic core material with low iron losses equivalent to steel plates. Iron losses of conventional powder magnetic cores of insulated iron powder with a phosphate coating are large at low frequencies. This developed material has achieved low iron losses with the distinction of the conventional powder core through the development of a new insulation material and coating technology. The development has four essential processes: the gaseous reaction method, the film structure having a compositional gradient continuous to iron oxide on the powder surface, the selection of film materials with thermal expansivity similar to iron substrate to prevent the occurrence of the ‘cracking by heating’ cycle, and the selection of more thermostable materials than iron oxide to prevent the composition and structure change above 600°C. It was noted that the vapour pressure of magnesium metal was high at a relatively low
metal-powder.net
temperature, so a Mg-Fe-O heat-resisting insulation coating made by magnesium vapourisation was adopted. Consequently, the powder magnetic cores of the developed insulation coating powders have lower iron losses than the steel plate at every frequency, so the cores are able to be used at a wide frequency range. Hitachi Powdered Metals Co. Produced a high wear resistant valve seat material for compressed natural gas (CNG) engines. The material makeup is 50 per cent hard particle (Co-50-9Cr-3Si) dispersed into a 5 per cent molybdenum steel matrix with precipitated CrS Solid lubricant. The study of alternative fuels for vehicles is pertinent due to the rising price of gasoline as well as other environmental concerns. This has increased demand for CNG engines which can reduce the amount of carbon dioxide and other harmful gases in its emissions. CNG engines require their valve seat materials to have very high wear resistance, due to the environment being drier than in gasoline and diesel engines. In such dry conditions, metal on metal contact occurs between the valve seat and the valve, leading to increased adhesive wear. The 5 per cent molybdenum steel base matrix was chosen for the new valve seat material due to its superior hardness from room temperature to high temperature, preventing adhesive wear. Also, the 50 per cent high performance hard particle was dispersed into the matrix to improve overall wear resistance. The precipitation of the CrS solid lubricant into the matrix also aids wear resistance. The material was introduced into the market in 2006 and contributed to an increase in engine durability as well as a decrease in maintenance frequency for engine manufacturers. The same company also looked into the high performance of sinter forged aluminium alloy. The material is an Al-Zn-MgCu alloy that improves tensile strength. It is applied to connecting rods of a general purpose engine by the sinter-forged method. Generally, sintered aluminium parts have been produced by the extrusion method or the sinter-gorging method that uses rapidly solidified Al-Si alloy powder. The extrusion material suffered from low yields and long processes while sinter-forged material was insufficient in tensile strength. A new original pre-mix powder was therefore developed. This
16
MPR September 2008
aimed at the substitution of connecting rods made of the aluminium-forged alloy that had already been put into production use along with the development of a new engine. High strength is achieved in the Al-Zn-Mg material in the base, wear resistance is attained by adding crb hard particle, and the improvement of plasticity is achieved by adding the pure aluminium powder. As a result, the product has lowered the cost and improved the fatigue strength by 18 per cent or more compared with a general aluminium-forged material. Also, a 20 per cent higher engine output was accomplished. Another development from Mitsubishi Materials PMG Corporation was the oilimpregnated sintered bearing applied as a bearing in the flow regulating valve for gas in an exhaust gas recirculation (EGR) unit. Used under a high temperature corrosion environment, the Cu-Ni-Sn-C-P material has improved corrosion resistance and abrasion resistance from the addition of nickel and phosphorous. Free graphite is distributed to solid solution blanks of Cu-Ni-Sn-P system as a solid lubricant and nickel provides corrosion control while phosphorous provides strength improvement. Impregnated oil with an excellent high-temperature lubricity is also used to aid the application’s performance in severe conditions. JFE Steel Corporation along with Toyota Motor Corporation and Fine Sinter Co. Developed a new alloyed steel powder, which gives sintered parts improved fatigue strength, by a conventional belt furnace sintering at a temperature of 1200°C or less. The developed powder gives a higher green density due to its lower molybdenum content of a pre-alloyed steel powder. At the same time, molybdenum-rich regions bonded on the surface of the powder particle exist as the alpha-iron phase during sintering which promotes efficient sintering. A warm compacted, mesh-belt sintered and carburised, quenched and tempered (CQT) treated specimen shows higher fatigue strength than that made of conventional molybdenum pre-alloyed steel powder through the same process. This is also the same as, or more than that of a high temperature sintered specimen made from the conventional diffusionalloyed steel powder. A sintered parts manufacturer has already been applying this powder as the raw mate-
rial of a high-strength part for automotive engines with advantages of sintering cost, productivity improvement and enhanced flexibility in the manufacturing process. The powder also gives an advantage over conventional diffusion-alloyed steel powder in terms of raw material cost reduction. An innovative offering came from Fine Sinter Co, who looked into the sintering of a low cost VCT rotor by means of machining at the green stage. The product is a rotor of a hydraulic actuator for an automotive engine VCT system. The design of the oil path was optimised and the following angle path side and proceeding angle side, totalling to seven oil paths, were formed through green machining and compacting as a current manufacturing line. As a result, in comparison with machining as sintered, the cutting speed was five times faster and the machining expense could be reduced by 60 per cent. In green machining it is important to factor in the prevention of burr occurrence and the invasion of foreign materials such as swarfs. Appropriate cutting tools are essential. Finally, the Porite Company introduced a low cost sintered oil-impregnated bearing with superior low and high temperature properties for an in-car motor. A Fe-Cu-SnZn-C type material with lower amounts of non-ferrous constituents compared to presently available copper based materials was developed. By using optimum impregnated oil, similar or better properties compared to conventional materials were attained at a lower cost. The material is used for in-car motors due to its highreliability over a wide temperature range. A 43 per cent reduction in raw material cost was achieved by using this material. Due to finer air pockets in this raw material, the permeability of the bearing was improved by 20 per cent resulting in augmentation of the oil film formation. The oxide film formation, due to the addition of zinc, improved corrosion resistance. Additionally, a reduction in the formation of hard ferrous impurities to one third improved the sliding contact properties with respect to the shaft. Results indicate that, compared to the present use of ball bearings and separate sintered bearings for low and high temperature applications respectively, this research makes it possible to use a single material in oil-impregnated bearings under various conditions.
metal-powder.net
Japanese PM Industry showcases rich new products and design The Japan Powder Metallurgy Association (JPMA) exhibit much to be positive about in the Japanese PM industry, as their report on 2007 paints a picture of confidence and innovation, says Rob Stringer.
T
he JPMA report on 2007 gives an account of PM production and powder shipments, before presenting the winning developments in design, material, new powders and innovation from the JPMA awards last year. Despite some slight decreases, total volume of Japanese PM production in 2007 was up overall, with a strong 4 per cent increase on the previous year at 121 153 tonnes. Broken down into types of goods manufactured, total production of bearings was 7 954 tonnes – slipping to 99.9 per cent of the previous year’s total while electric contacts had fallen further to 93.9 per cent with 93 tonnes. Production of machine parts, however, was up 4.3 per cent from 2006 at 110 665 tonnes, while friction materials shot up 8.5 per cent to 788 tonnes. Production of other components also rose with a 6.3 per cent increase on the previous year to 1 653 tonnes. Production volume of Japanese machine parts in 2007 (Figure 1) continued trends of positive growth for the sixth consecutive year, as well as maintaining record high volumes for five consecutive years. This is attributed to an economy kept strong by such factors as the export of vehicles. When compared to the same periods of the previous year, the quarterly trend demonstrated comprehensive growth of 3.4 per cent for January to March, 6.6 per cent for April to June, 1.9 per cent for July to September and 5.7 per cent for October to December. Total production sales amounted to ¥135 billion, a 5.9 per cent rise over the previous year.
8
MPR September 2008
Sintered parts remain to be predominantly manufactured for automobile usage, with production volume amounting to 101 386 tonnes – a 3.8 per cent increase on the
previous year. Vehicle parts accounted for 91.6 per cent of all machine parts, indicating a continued high dependence on the automobile industry.
Figure 1: Production of machine parts and bearings
0026-0657/08 ©2008 Elsevier Ltd. All rights reserved.
58.1 per cent of total production – a 3.1 per cent increase on the previous year. Other uses of bearings totalled 3 335 tonnes – a 7.2 per cent drop from the previous year, continuing a trend of decrease over three consecutive years.
Powder shipments
The sum of other machine parts not used in vehicles amounted to 9 280 tonnes, exhibiting the first increase in three years with a 10.3 per cent growth from the previous year. Assessments in the report for the total weight of sintered parts used in one car took their figures from 2006, when the total in Japan was 8.6 kg, 19.5 kg for the US and 9.3 kg in Europe. The figure is particularly high in the US because larger parts such as the connecting rod and bearing cap are already being sintered whereas in Japan, other production methods are currently being used. Consequently, the Japanese industry plans to follow their lead. Figure 2 illustrates production volume of sintered machine parts applied to respective sections of automobiles in 2006, based on a demand structure survey by the JPMA. 51.1 per cent were used in engine parts, slipping from 51.5 per cent the previous year; 24 per cent were for use in drive train parts, a decrease from 24.5 per cent in 2005, while a slight increase was seen in chassis parts, up from 14 per cent in 2005 to 14.2 per cent in 2006.
1.7 per cent and the final quarter, October to December, was up 3.7 per cent. Production sales amounted to ¥15.8 billion, an increase of 7.8 per cent on the previous year. An increase in the production of complicated products requiring high reliability was also seen. As with machine parts, the highest demand for bearings in 2007 was seen in the automobile industry. Production volume for vehicles was 4 620 tonnes, 5.7 per cent up on the previous year, and continued a trend of steady increase over four years. This included bearings for millers and door locks, which contributed
The report largely displayed strengthened figures for Japanese powder shipment in 2007. Iron powder shipments amounted to 228 624 tonnes in total, rising 2 per cent from the previous year. Among this, domestic shipment for PM use was 131 869 tonnes – a 3.9 per cent increase on the previous year. A rise of 6.8 per cent from 2006 was seen in copper powder shipments, totalling 8 939 tonnes. Shipments for PM use amounted to 6 691 tonnes – a 6.2 per cent growth on the previous year. Records for stainless steel shipments for PM usage in 2007 were not yet available but the report recalled strong growth of over 10 per cent every year from 2001 to 2004, while 2005 brought a lesser increase of 3.6 per cent at 4 718 tonnes, and 2006 saw a decrease of 3.2 per cent to 4 104 tonnes. Domestic shipment of MIM powder in 2006 was 507 tonnes, indicating a 20.7 per cent increase from 2005.
The JPMA awards 2007 A multitude of design developments were detailed in the JPMA report for 2007 with
Bearings The quarterly trend in Japanese production volume of bearings in 2007, when compared with the same period in the previous year, showed a 5.3 per cent fall from January to March, while April to June was up 0.2 per cent, July to September was up
10
MPR September 2008
Figure 2: Breakdown of machine parts for automobile (2007)
metal-powder.net
categories given to new designs, new materials, new powders and further innovation. Contributing to new designs, Sumitomo Electric Industries developed a 4WD part used for connecting the carrier of a high torque unit to a low torque output gear shaft. With high density and a complicated shape, the part has an outside spline on the flange, which is inserted into an internal spline of a carrier. The flange has nine
holes for weight reduction located near the boss. The boss has an internal spline, and an output gear shaft is inserted into this spline for torque transfer to an output shaft. The internal spline has a back taper for compaction in order to allow smooth insertion of this shaft. Using PM production, a 6 per cent weight reduction of the original forging design could be achieved.
Sumitomo PM sprocket and housing body for electro magnetic actuated VCT systems.
Guide plates from Porite for an overload clutch in a hammer drill.
12
MPR September 2008
Compaction without machining is attained by designing a compacting tool structure and an improved ejection process. The internal spline of the boss requires impact strength and hertzian fatigue strength which is achieved with a density of 7.0 g/cm3 minimum and induction hardening. The density of the compaction process is 6.9 g/cm3 due to the position of the internal spline. A back taper and density of over 7.0 g/cm3 is achieved through a sizing process. Sizing and material shape may be optimised through finite element analysis. Sumitomo Electric Industries also oversaw the development of “highly efficient PM internal gear pump rotors with newly developed teeth profiles”. These PM internal pump rotors are used in automotive oil pumps for engines, automatic transmissions, continuously variable transmissions and fuel feed pumps of diesel engines. Despite recent focus on the strong demand for low fuel consumption of automobiles, the energy loss of oil pumps is about 10 per cent while the energy loss of automatic transmission oil pumps is about 20-30 per cent. Customer demand for efficient oil-pumps is consequently strong. The energy loss of geared fuel pumps depends on friction loss influenced by the side face of rotors and the outside surface of an outer rotor. In order to reduce the loss, new teeth profiles have been developed to increase the theoretical discharge volume from the same diameter of an outer rotor. The conventional teeth profile of the inner rotor has one base circle. Displacement distance relating to the discharge volume is determined by the base circle and number of teeth. As the theoretical discharge volume depends on the displacement distance and one base circle, the newly developed inner rotor’s profile has two base circles to enlarge the displacement distance. The outer rotor profile is generated from that of the inner profile. The optimisation of the design parameters was carried out through theoretical calculation and by evaluating a sample test. The theoretical discharge volume of the newly developed internal rotors was 12% higher than that of the same sized conventional rotors. As long as the required actual discharge volume stays constant, the downsizing of the rotor as well as energy loss reduction can be achieved. This downsizing enables the drive torque
metal-powder.net
of a newly developed oil pump a 10% reduction compared with the original. Also from Sumitomo Electric Industries came the development of a PM sprocket combined with a housing body for electro magnetic actuated variable cam timing (VCT) systems. The VCT system is used for almost all new model vehicles and is generally actuated by the oil hydraulic system. However, due to recent market demands such as high engine performance, low fuel consumption and low emission, the electro magnetic actuated VCT was developed. The PM sprocket consists of a timing sprocket and a housing body. Due to the part’s complicated shape, the sprocket and housing are made separately by conventional processes and joined together with screw bolts. The housing sprocket is compacted in one compacting stroke. Mitsubishi Materials PMG Corporation developed sintered parts with multiple teeth for a steering tilt of an automobile, consisting of a tooth lock and two cams. These applications aim to increase the expansion and contraction of holding power, due to the connection mechanism of the gear which satisfies the collision safety level, in order to develop the new steering column. The system consists of tooth lock A, possessing 22 teeth, and cam A, which has an uneven surface. Form and flatness for the tooth lock were achieved through optimisation of the die form and rationalisation of the operation. Level precision and density equalisation of cam A were attained through die constitution such as unification of the upper punch and rationalisation of the operation. The result was that highly accurate mass production of a part with high intensity could be achieved. A guide plate for the overload clutch in a hammer drill was developed by the Porite Corporation. Due to its complex shape, the part was originally manufactured through metal injection moulding (MIM); consequently, the shape of the product was reviewed. The tooling structure was improved and the grooves were pressed by the same punch for accuracy of size. The eight grooves were increased to ten for dispersion of the groove load, and keyway was added to the inside for torque transmission. A machining process was added to keep the height accuracy of the groove. Product cost through PM production was cut by 40 per cent. The final new development in design was in long thin-walled helical gear parts
14
MPR September 2008
Hitachi connecting rods using sinter forged aluminium alloy.
Oil-impregnated sintered bearings from Mitsubishi applied in the flow regulating valve for gas in an exhaust gas recirculation unit.
with a non-regular shape on the inside, also from the Porite Corporation. The product is a planet gear for the gear box used to revolve the washing drum of an automatic washing machine. It has involute serration on the inside and a helical gear on the outside. In the past, the application was produced through broach processing on the inside and gear cutting on the outside. It can now be produced by powder metallurgy without post-processing. In order to attain product accuracy, the tooling structure, material and press work were reviewed. Density distribution between ups and downs was found to be 0.03-0.04 Mg/m3, runout accuracy was under 0.025 mm and helix deviation was JIS 2nd class. Also, the tolerance width to press in the resin bush was 0.08mm. Consequently, the long thin-wall complex shape such as in this product is now manufacturable. The section for developments in materials begins with Mitsubishi Materials PMG
Corporation for their powder magnetic core material with low iron losses equivalent to steel plates. Iron losses of conventional powder magnetic cores of insulated iron powder with a phosphate coating are large at low frequencies. This developed material has achieved low iron losses with the distinction of the conventional powder core through the development of a new insulation material and coating technology. The development has four essential processes: the gaseous reaction method, the film structure having a compositional gradient continuous to iron oxide on the powder surface, the selection of film materials with thermal expansivity similar to iron substrate to prevent the occurrence of the ‘cracking by heating’ cycle, and the selection of more thermostable materials than iron oxide to prevent the composition and structure change above 600°C. It was noted that the vapour pressure of magnesium metal was high at a relatively low
metal-powder.net
temperature, so a Mg-Fe-O heat-resisting insulation coating made by magnesium vapourisation was adopted. Consequently, the powder magnetic cores of the developed insulation coating powders have lower iron losses than the steel plate at every frequency, so the cores are able to be used at a wide frequency range. Hitachi Powdered Metals Co. Produced a high wear resistant valve seat material for compressed natural gas (CNG) engines. The material makeup is 50 per cent hard particle (Co-50-9Cr-3Si) dispersed into a 5 per cent molybdenum steel matrix with precipitated CrS Solid lubricant. The study of alternative fuels for vehicles is pertinent due to the rising price of gasoline as well as other environmental concerns. This has increased demand for CNG engines which can reduce the amount of carbon dioxide and other harmful gases in its emissions. CNG engines require their valve seat materials to have very high wear resistance, due to the environment being drier than in gasoline and diesel engines. In such dry conditions, metal on metal contact occurs between the valve seat and the valve, leading to increased adhesive wear. The 5 per cent molybdenum steel base matrix was chosen for the new valve seat material due to its superior hardness from room temperature to high temperature, preventing adhesive wear. Also, the 50 per cent high performance hard particle was dispersed into the matrix to improve overall wear resistance. The precipitation of the CrS solid lubricant into the matrix also aids wear resistance. The material was introduced into the market in 2006 and contributed to an increase in engine durability as well as a decrease in maintenance frequency for engine manufacturers. The same company also looked into the high performance of sinter forged aluminium alloy. The material is an Al-Zn-MgCu alloy that improves tensile strength. It is applied to connecting rods of a general purpose engine by the sinter-forged method. Generally, sintered aluminium parts have been produced by the extrusion method or the sinter-gorging method that uses rapidly solidified Al-Si alloy powder. The extrusion material suffered from low yields and long processes while sinter-forged material was insufficient in tensile strength. A new original pre-mix powder was therefore developed. This
16
MPR September 2008
aimed at the substitution of connecting rods made of the aluminium-forged alloy that had already been put into production use along with the development of a new engine. High strength is achieved in the Al-Zn-Mg material in the base, wear resistance is attained by adding crb hard particle, and the improvement of plasticity is achieved by adding the pure aluminium powder. As a result, the product has lowered the cost and improved the fatigue strength by 18 per cent or more compared with a general aluminium-forged material. Also, a 20 per cent higher engine output was accomplished. Another development from Mitsubishi Materials PMG Corporation was the oilimpregnated sintered bearing applied as a bearing in the flow regulating valve for gas in an exhaust gas recirculation (EGR) unit. Used under a high temperature corrosion environment, the Cu-Ni-Sn-C-P material has improved corrosion resistance and abrasion resistance from the addition of nickel and phosphorous. Free graphite is distributed to solid solution blanks of Cu-Ni-Sn-P system as a solid lubricant and nickel provides corrosion control while phosphorous provides strength improvement. Impregnated oil with an excellent high-temperature lubricity is also used to aid the application’s performance in severe conditions. JFE Steel Corporation along with Toyota Motor Corporation and Fine Sinter Co. Developed a new alloyed steel powder, which gives sintered parts improved fatigue strength, by a conventional belt furnace sintering at a temperature of 1200°C or less. The developed powder gives a higher green density due to its lower molybdenum content of a pre-alloyed steel powder. At the same time, molybdenum-rich regions bonded on the surface of the powder particle exist as the alpha-iron phase during sintering which promotes efficient sintering. A warm compacted, mesh-belt sintered and carburised, quenched and tempered (CQT) treated specimen shows higher fatigue strength than that made of conventional molybdenum pre-alloyed steel powder through the same process. This is also the same as, or more than that of a high temperature sintered specimen made from the conventional diffusionalloyed steel powder. A sintered parts manufacturer has already been applying this powder as the raw mate-
rial of a high-strength part for automotive engines with advantages of sintering cost, productivity improvement and enhanced flexibility in the manufacturing process. The powder also gives an advantage over conventional diffusion-alloyed steel powder in terms of raw material cost reduction. An innovative offering came from Fine Sinter Co, who looked into the sintering of a low cost VCT rotor by means of machining at the green stage. The product is a rotor of a hydraulic actuator for an automotive engine VCT system. The design of the oil path was optimised and the following angle path side and proceeding angle side, totalling to seven oil paths, were formed through green machining and compacting as a current manufacturing line. As a result, in comparison with machining as sintered, the cutting speed was five times faster and the machining expense could be reduced by 60 per cent. In green machining it is important to factor in the prevention of burr occurrence and the invasion of foreign materials such as swarfs. Appropriate cutting tools are essential. Finally, the Porite Company introduced a low cost sintered oil-impregnated bearing with superior low and high temperature properties for an in-car motor. A Fe-Cu-SnZn-C type material with lower amounts of non-ferrous constituents compared to presently available copper based materials was developed. By using optimum impregnated oil, similar or better properties compared to conventional materials were attained at a lower cost. The material is used for in-car motors due to its highreliability over a wide temperature range. A 43 per cent reduction in raw material cost was achieved by using this material. Due to finer air pockets in this raw material, the permeability of the bearing was improved by 20 per cent resulting in augmentation of the oil film formation. The oxide film formation, due to the addition of zinc, improved corrosion resistance. Additionally, a reduction in the formation of hard ferrous impurities to one third improved the sliding contact properties with respect to the shaft. Results indicate that, compared to the present use of ball bearings and separate sintered bearings for low and high temperature applications respectively, this research makes it possible to use a single material in oil-impregnated bearings under various conditions.
metal-powder.net