The winners of the Japan Powder Metallurgy Association (JPMA) 2007 Powder Metallurgy Awards highlight the capabilities of PM and demonstrate the continuing advances of Japan’s PM industry. Many of the winners are evidence of the continuing potential for PM applications in the automotive industry.
New Design Category
Sumitomo Electric Industries Ltd
Sumitomo Electric Industries Ltd (SEI) received three awards in the Japan Powder Metallurgy Association’s (JPMA) New Design Category.
The first was for the development of a high density, complex shaped PM gear (Fig. 1) which is inserted into the internal spline of the 4WD planetary carrier and transfers the torque from the high torque input gear shaft to the low torque output gear shaft. This part, which was originally designed for cold forging, has an external spline on the flange and this spline is inserted into the internal spline of the carrier.
The flange itself has nine holes located near the boss giving 6% weight reduction. The boss has an internal spline and an output gear shaft is inserted into this spline for torque transfer to the output shaft. The internal spline has a back taper to facilitate die compaction and ejection from the die, and to allow for smooth insertion of the shaft. The 7.0 g/cm3 density parts are sized and induction hardened and meet the requirements for impact strength and hertzian fatigue strength.
The second award given to SEI in this category is for gear pump rotors (Fig.2) having a newly developed tooth profile which are used in automotive oil pumps (engine, automatic transmission, CVT, fuel feed in diesel engines, etc).
It is stated that the energy losses of oil pumps due to friction losses is around 10% for engine pumps and 20-30% in pumps for automatic transmissions. The friction loss is influenced by the side face of rotors and outside surface of the outer rotor. Therefore in order to improve their operating efficiency by increasing the theoretical pump discharge volume new tooth profiles were developed.
The conventional profile of the internal rotor has one base circle, and the displacement distance which relates to discharge volume is decided on this base circle and the number of teeth. The newly developed profile of the inner rotor has two base circles in order to increase displacement distance, and the profile between these circles is an involute curve. The design of the outer rotor is generated from the profile of the internal rotor.
As a result the theoretical discharge volume of the newly designed internal rotors is 12% higher than that of equivalent size conventional rotors. This allows for around 10% downsizing of the pump and reduces energy losses.
A PM sprocket combined with housing body (Fig.3) produced by SEI and used in an electro magnetic actuated variable-cam-timing (VCT) system was also given an award in the New Design Category. VCT systems are used for almost all new model vehicles and these are normally hydraulically actuated.
The newly developed electro magnetic CVT is said to improve engine performance and reduce fuel consumption and emissions. The PM sprocket and housing is compacted as one piece.
Mitsubishi Materials PMG Corp
Mitsubishi Materials PMG Corp. received an award in this category for sintered parts used in the steering tilt mechanism (Fig. 4) of a new car steering column which meets requirements for collision safety.
The part acting as a tooth lock comprises 22 teeth and is required to have guaranteed dimensional tolerances as well as high strength and flatness. The surface of the cam is different and is required to have an uneven surface.
Porite Corp. received two awards in this category. The first is a guide plate (Fig. 5) of an overload clutch used in a hammer drill. This complex shaped part was produced by MIM but it was redesigned as a press and sintered part which was able to match the dimensional accuracy and strength of the MIM part.
The product requires tight dimensional accuracy of the groove and its height to control idle torque during overload, and to retain the spring and roller.
In the new design the number of grooves was increased from 8 to 10 for dispersion of the load on the groove and an inner keyway was added for torque transmission. The redesign for PM resulted in a cost reduction of 40% for this part.
The second part receiving an award for Porite Corp. in this category was a thin-wall helical gear (Fig.6) having irregular internal shape. The part is a planetary gear used in the gearbox of a revolving drum in an automatic washing machine. The gear was previously manufactured by broaching and gear cutting. The PM helical gear is produced to close dimensional accuracy in order to meet requirements for quiet operation in the washing machine.
New Materials Category
Mitsubishi Materials PMG Corp
Mitsubishi Materials PMG Corp. received two awards in this category. The first was for a new insulated iron powder used for cores in magnetic sensors (Fig. 7), and which are said to have lower losses than steel sheet at every frequency making them suitable for a wide frequency range.
The company uses a gaseous reaction method to achieve the uniform thin insulating film on irregular shaped atomized iron powders with no loss in compressibility of the resulting insulated powder. The new heat resistant insulating coating is based on Mg-Fe-O which is achieved by magnesium vaporisation onto the iron powder particles.
The second award given to Mitsubishi Materials was for a new Cu-Ni-Sn-C-P self-lubricating bearing material (Fig. 8) capable of withstanding abrasion, corrosion and operating at high temperatures in the flow regulating valve of EGR units in automotive engines.
The excellent high temperature lubricity of the new bearing material is achieved by free graphite distribution as a solid lubricant in the Cu-Ni-Sn-P material system. Ni is included to enhance corrosion resistance and the addition of P improves strength. As a result the new sintered bearing has replaced the more expensive carbon bushing in this application.
Hitachi Powdered Metals Co Ltd
Hitachi Powdered Metals Co Ltd also received two awards in this category. The first is for a new valve seat material (Fig. 9) used in CNG engines which have reduced CO2 and other harmful emissions compared with petrol/diesel engines. However, in providing reduced emissions the CNG engines require valve seats to have very high wear resistance.
The new material introduced in 2006 is made up of 50% hard particles (Co50-Cr9-Si3) dispersed in a steel matrix containing 5%Mo with precipitated CrS solid lubricant.
The 5%Mo steel base matrix containing the 50% hard particles was chosen because of its superior hardness at room and elevated temperatures, lack of adhesive wear, and overall improved wear resistance. Also the precipitation of the CrS solid lubricant into the matrix was said to further help improve wear resistance.
The second award was for a new high strength PM Al-Zn-Mg-Cu alloy that is used to powder forge aluminium connecting rods (Fig.10) for general purpose engines.
Previously rapidly solidified Al-Si powder has been used for PM aluminium parts made by extrusion or powder forging; however, the process route was longer, costlier and the PF parts had insufficient tensile strength.
The new Al-alloy powder is based on a premixed powder using optimised mixing methods aimed at controlling alloy segregation during powder compaction and element change during sintering. High strength is achieved by using an Al-Zn-Mg base material, wear resistance is improved by addition of CrB hard particles, and plasticity is achieved by adding pure Al powder.
The resulting powder results in 18% higher fatigue properties compared with a general Al-forged material, and in addition to lower cost the new PM Al-Zn-Mg-Cu alloy product offers a 20% improvement in engine performance.
JFE Steel Corp
JFE Steel Corp. , Toyota Motor Corp, and Fine Sinter Co Ltd, received the JPMA award for New Powders in 2007 for an Mo alloyed steel powder (Fig.11) which provides improved fatigue strength when sintered in a conventional belt furnace at temperatures of 1200OC or lower.
The new atomised prealloyed powder produced by JFE Steel gives high green density due to its lower Mo content whilst at the same time the Mo-rich regions bonded to the surface of the powder particles exist as an alpha-phase during sintering and promote sinterability of the material.
Warm compacted, mesh-belt furnace sintered and CQT heat treated parts made from the new powder show higher fatigue strength compared with conventional Mo prealloyed powder, and it is also comparable in strength to high temperature sintered specimens made from diffusion alloyed steel powder but at lower cost. The developed powder is being used to produce high strength PM parts for car engines with resulting lower sintering costs and productivity improvements.
Fine Sinter Co Ltd
Fine Sinter Co Ltd received an award in this category for a low cost sintered rotor (Fig. 12) used in the hydraulic actuator of a variable cam timing (VCT) system. This part contains the rotor which has following angle oil path slits and a sprocket which has preceding angle oil path slits.
The design of the seven oil paths has been optimised with the oil paths shaped by machining the compacts in the green state after compaction in a consecutive production line.
As a result the cutting speed in machining of the oil paths slits was five times faster than machining in the as-sintered state, and the cost of machining was reduced by 60%. Fine Sinter also optimised the machining of the compacts in the green state such as the prevention of burrs and swarf material entering the compacts as well as selection of the best cutting tool material for the application.
Porite Corp. received the other award in the Effort Prize category for its low cost Fe-Cu-Sn-Zn-C bearing material (Fig. 13) which is said to offer superior low and high temperature properties for oil-impregnated bearings used for in-car motors. This ferrous-based PM bearing material realises a 43% reduction in raw material costs compared with conventional Cu-based materials.
The permeability of the bearing has been improved by 20% due to the finer air pockets of the material resulting in augmentation of the oil film formation and lowering of the friction coefficient.
The formation of an oxide film due to the addition of Zn improved corrosion resistance, and one-third reduction in the formation of hard ferrous impurities improved the sliding contact properties of the bearing with respect to the shaft.
For more information please visit the JPMA website