Iron based sintered body excellent in enveloped casting property in light metal alloy and method for producing the same

Abstract

An iron based sintered body suitable for being enveloped in a light metal alloy such as an aluminum alloy by casting, and a method for producing the same. A mixed powder is prepared by mixing an iron based powder, a copper powder and a graphite powder blended so that the Cu content and the C content are 5 to 40% by mass and 0.5 to 2.5% by mass, respectively, in the mixed powder. A lubricant powder and a fine particle powder for improving machinability may be further added in the mixed powder. Then, the mixed powder is filled into a mold formed to a green compact, and is sintered into a sintered body so that the sintered body has a desired average thermal expansion coefficient. The surface of the sintered body may be adjusted to have a surface roughness Rz of 10 to 100 μm optionally by applying a shot blast treatment or by a shot blast treatment and an additional steam treatment. This process permits the sintered body to be enhanced in adhesive property and bonding strength while being improved in enveloping casting property when the sintered body is enveloped in the light metal alloy by casting. A martesitic stainless steel powder or ferritic stainless steel powder may be used instead of the pure iron powder, or Cr, Mo and W powders may be further blended.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a division of U.S. patent application Ser. No. 10 / 743,325, filed Dec. 23, 2003, which claims priority to Japanese patent application JP 374650 / 2002, filed Dec. 25, 2002, the entire disclosures of which are herein incorporated by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The invention relates to an iron based sintered body, particularly to an iron based sintered body excellent in enveloped casting property in a light metal alloy. The iron based sintered body is used as being enveloped in a light metal alloy member such as an aluminum alloy by casting. [0004] 2. Description of the Related Art [0005] Automobile parts made of an aluminum alloy as a kind of light metal alloys are widely used for making the automobile parts lightweight and for enhancing heat-release ability thereof. However, the aluminum alloys are insufficient in material characteristics as automobile structural members...

AI Technical Summary

Benefits of technology

[0011] (1) An iron based sintered body 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 and free Cu phases dispersed in a matrix, an average thermal expansion coefficient from room temperture to 200° C. of 13.5×10−6 / ° C. or less, and a surface roughness Rz of 10 to 100 μm, and being excellent in an enveloped casting property in a light metal alloy.

[0018] (8) The iron based sintered body in any one of the above items (1) to (7), in which the structure further comprises 0.1 to 5% by mass of fine particles for improving machinability having a particle diameter of 150 μm or less and comprising at least one element selected from the group consisting of MnS, CaF2, BN and enstatite.

[0028] (18) The method for producing the iron based sintered body in any one of the above items (14) to (17), wherein the mixed powder is further blended any one of a Cr powder, Mo powder, W powder, Fe—Cr powder, Fe—Mo powder and Fe—W powder is blended, alone or in combination, as an alloy element powder so that the mixed powder comprises, in % by mass, 40% or less in total of at least one element selected from the group consisting of 30% or less of Cr, 10% or less of Mo, 3% or less of Ni, 3% or less of Si, 2.5% or less of Mn, 5% or less of V, 5% or less of Ti, 3% or less of Nb and 5% or less of W relative to the total amount of iron based powder, copper powder, graphite powder, fine particle powder for improving machinability and alloy element powder in the mixed powder.

Problems solved by technology

However, the aluminum alloys are insufficient in material characteristics as automobile structural members including poor mechanical properties such as strength, wear resistance and rigidity as well as high thermal expansion coefficient as compared with usually used cast iron.

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