Yasuaki Morioka

Recent advances in production of steel powders for high strength PM parts

Kawasaki has recently developed three series of low alloy steel powders: 1) A new type of Ni-Cu-Mo alloy steel powder; 2) A low oxygen alloy steel powder by vacuum annealing; 3) A composite type alloy steel powder. This paper describes recent advances in alloy steel powders, in particular their production methods and the properties of these low alloy steel powders. Furthermore, a new composite type alloy steel powder for ultra high strength parts will also be presented.

Alloyed steel powder for high strength PM parts

Abstract In Japan many car makers are now developing new engines offering high performance and good fuel economy. Sintered products for use in such engines must have higher performance and smaller size than that of the present components, coupled with high strength, high toughness and good fatigue properties. The maximum tensile strength of sintered compacts is about 1300 MPa and to obtain a greater strength it is necessary to add alloying elements, raise the sintered density and heat-treat the parts. Simultaneously to obtain high toughness adequate chemical composites must be selected and the microstructure of sintered compacts controlled. Yasuaki Morioka describes the characteristics of a new alloyed steel powder ‘KIP Sigmaloy 2010’ developed by Kawasaki Steel for ultra high strength PM parts, and the features of sintered compacts made from this powder.

Sintered Manganese Steel. (Part III)

Effects of repressing and resintering on the physical and mechanical properties of sintered compacts were studied.The results obtained were as follows :(1) Microstructures of sintered compacts have a large effect on the repressing ratio and the increase in density. Ferritic and austenitic structures give large repressing ratios.(2) On repressing sintered compacts containing Mn 10% and C 1.2% which might show martensitic structure, pre-sintering at a lower temperature and pre-pressing at a lower compacting pressure are recommended, while, for the compacts containing Mn 20% and C 2.0% which might show austenitic structure, pre-sintering at a higher temperature and prepressing at a higher compacting pressure are recommended.(3) On cyclic sintering and pressing, tensile strength and elongation of sintered compacts of ferritic and austenitic structures are saturated by a single process of repressing and resintering, but those of martensitic structure are not saturated even by repressing and resintering three times. Repressing is less effective for martensitic structures than for ferritic or austenitic structures.(4) Mechanical properties of sintered manganese steel are much affected by repressing and resintering treatments. Tensile strength of about 35-40kg/mm2, elongation of about 8-13%, and impact energy of about 2-6kg-m/cm2 can be obtained for austenitic manganese steel.