The winners of the Japan Powder Metallurgy Association (JPMA) 2005 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 Sintered Alloy Ltd
Sumitomo Electric Sintered Alloy Ltd received an award for a stopper part (Fig. 13) made from sintered Fe-Ni-Cu-Mo-C and used in the retractable mechanism of a side mirror.
The PM stopper part was successful in replacing a diecast part previously used, through a redesign of the retractable mirror which included downsizing and a more sophisticated mechanism requiring and a thinner shaped stopper.
Because of the thin shape there were risks of chipping and cracking of the compacts, and to prevent this, special mechanical devices were developed for part handling during compaction and sizing. To guarantee crack-free parts an automatic resonance acoustic device was installed in the production line
Mitsubishi Materials Corporation
Mitsubishi Materials Corp. was given three awards in the New Design category. The first was for a sintered stainless steel pulley (Fig. 14) used in a high output 4-stroke outboard marine engine. The new outboard engine has improved fuel efficiency with reduced emissions and is aimed at replacing 2-stroke marine engines. PM competed with aluminium diecasting for this new application but preference was given to the PM stainless material because of its higher strength and wear resistance.
A problem was encountered with compacting the stainless steel powder which had a tendency to stick to the tool surfaces. To resolve this problem the amount of internal lubricant was increased; however, to prevent segregation of the lubricant in the powder mix, a liquid binder was first used to coat the powder particles and then admixing the lubricant. The lubricant was extracted in the vacuum furnace prior to sintering. A further problem of surface scratches on the pulley during sizing was solved by developing a special oil.
The second award presented to Mitsubishi Materials Corp. was for a sintered and steam treated piston part used in a swing compressor (Fig. 15).
The PM part is produced without the need for sizing or machining by using an improved method of compaction (tapered die) and a powder having good flowability to give high density and strength. The piston parts are steam treated to make them airtight.
Mitsubishi Materials received a further award for five PM parts (Fig. 16) used in the seat belt retraction mechanism device of a PCS (Pre-Crash Safety) system in cars. The reliability of operation in an emergency is key to the PCS system and the PM parts are compacted at room temperature to a green density of 6.9 – 7.0 g/cm3 to give the required strength and wear resistance. The corrosion resistance of the PM parts is assured by plating and resin impregnation.
Porite Corp. received an award for a Nakanige sintered bearing (Fig. 17) used in slim type CD/DVD spindle motors. The design of the bearing features improved accuracy of the inner diameter thereby reducing machining by reaming and assembly of the part into the brass housing. The one-piece design is compacted using two upper punches and three lower punches.
It has replaced the previous need for two PM bearings or one Nakanige PM bearing and then assembling into the brass housing. The new PM bearing offers a cost saving of up to 50%.
Porite Corp received a further award for a new long life PM bearing (Fig. 18) used in a high speed DLP colour wheel motor used in home projection systems. The PM bearing is expected to operate at 10,800 rpm and temperatures of 85°C near the projector lamp. This required the selection of a suitable lubricating oil containing additives to give low viscosity, and avoid oxidation and evaporation at the high operating temperatures.
A wool felt oil system was used in the housing assembly design to reduce noise levels. A clearance of 3 microns or less is achieved between the bearing ID and shaft in order to reduce the clearance noise factor. The PM bearing successfully passed the 70,000 hr operating life requirement of the DLP motor.
Hitachi Powdered Metals Co Ltd
Hitachi Powdered Metals Co Ltd received an award for a complex shaped synchroniser hub (Fig. 19) used in a manual automotive transmission. Because the hub is used only to synchronise with the reverse gear, only one face needs to feature the synchroniser ring and cone, keys and sleeve.
The hub features stoppers on one face of the part to avoid keys, shaft and sleeve from coming off from the part. Key slots have lids on one end to cover the entire area of slots, but the design of the slots was changed from the original two crest type to a lid design for ease of compaction. The lids are compacted in a CNC press for optimum density control and using a stepped die containing die inserts.
New materials category
Hitachi Powdered Metals Co Ltd
Hitachi Powdered Metals Co Ltd received an award in the New Materials category for its newly developed Fe-Cu-Sn-C-P-MgSiO3-MnS sintered valve guide material (Fig. 20) which competed successfully with brass and cast iron valve guides currently used in IC engines.
The new material gives both good wear resistance against the valve stem and good machinability. This is achieved by dispersing a lot of free graphite, addition of MgSiO3 and MnS, and decreasing the phosphorus content.
The new valve guide material has almost equal machinability to cast iron, and has much higher wear resistance when compared with cast iron and brass. The PM steel also has the same anti-seizure performance as brass for non-coated valve stems.
Mitsubishi Materials Corporation
Mitsubishi Materials Corp. received an award for its new powder forged valve seats (Fig. 21) for both cast iron and aluminium cylinder heads used in car and truck engines. The PF valve seat is made from Fe-C-Cr-Mo-Co-Ni-Nb-CaF2 to meet the stringent dry operating environment required for low emissions. High adhesive wear resistance was achieved by using CaF2 instead of Pb.
MMC produces two types of PF valve seats: one has higher adhesive wear resistance using Fe-Mo hard particles, and the other has lower valve attack properties by partially substituting Fe-Mo by Co-Mo hard particles.
Fine Sinter Co Ltd
A copper-based friction brake lining material (Fig. 22) developed by Fine Sinter Co Ltd for use on high-speed trains traveling at speeds of 300 km/hr or more, received an award in the New Materials category.
In this development, downsizing of the brakes and dramatic improvements in wear resistance of the new friction material at high temperatures allow braking speeds up to 320 km/hr, and the material is expected to get approval for speeds up to 350 km/hr.
The improvement was obtained by switching from a conventional Cn-Sn matrix in the friction material to a Cu-Sn-Ni-Cr-Fe matrix also containing ceramic and graphite additives to improve energy absorption.
Suruga Seiki Co Ltd
Suruga Seiki Co Ltd received an award for a new magnetic sensor gear component (Fig. 23) used in spindle motors. The PM process allowed the complex sensor gear to be produced as one part compared with a two-part assembled gear previously used.
The sensor is produced by compacting the gear teeth to double the length of the required plural-teeth gear. The rectangular groove on the component’s outer circumference is machined central to the direction of part thickness.
Finally, all the sintered teeth except one are shaved to half their length using a shaving blade with one tooth groove in the blade. The combination of PM processing and machining of the magnetic sensor yielded a 70% cost reduction.
Fine Sinter Co Ltd
Two awards in this catetory were given to Fine Sinter Co Ltd for new PM applications. The first is a high density sloping stainless steel sensor (Fig. 24) which monitors exhaust gases to a maniverter. The sloping shape is required to make a joint with the complex shaped maniverter.
Because the angle of slope is 20° or more it makes it difficult to compact due to sliding of the stainless powder. The company overcame this problem by splitting the end of the lower punch. The PM sensor is airtight and meets requirements for corrosion resistance at high temperatures and weldability.
The second award given to Fine Sinter Co Ltd is for a complex sintered part used in a manual automotive transmission. The part (Fig. 25) has six projected shapes which guide a pin on a countering part to improve gear shift feeling when changing vehicle speed.
The relatively thin projections on the part required careful control of the powder compacting operation in order to achieve uniform density throughout the part and avoid cracks both during compaction and part handling. The sintering and heat treatment operations also had to be optimised in order to prevent part distortion.
For more information please visit the JPMA website