Patent ID: 7014677

Claim:
An iron based sintered body which is enveloped in a cast light metal alloy member, having a composition comprising, in % by mass, 0.5 to 2.5% of C, 5 to 40% of Cu, and the balance being Fe and inevitable impurities, a structure containing pores, said pores being isolated or partially connected to each other, wherein the value defined by [(the volume of fully connected pores)/(the total volume of pores)×100(%)] is 50 or less, and the volume ratio of the pores relative to a total volume of the sintered body is 13–35% by volume, and free Cu phases dispersed in a matrix, an average thermal expansion coefficient from room temperature to 200° C. of 13.5×10 −6 /° C. or less, and a surface roughness Rz of 26 to 100 μm.