Ferrous sintered alloy and process for producing the same as well as ferrous-sintered-alloy member

Abstract

A process for producing ferrous sintered alloy according to the present invention is characterized in that it is equipped with: a compaction step of pressure compacting a raw-material powder in which an Fe-system powder is mixed with a reinforcement powder, thereby turning the raw-material powder into a powder compact; and a sintering step of heating this powder compact in an oxidation preventive atmosphere, thereby sintering the powder compact; and said reinforcement powder is an Fe—Mn—Si—C powder comprising an Fe alloy or an Fe compound that includes: Mn in an amount of from 58 to 70%; Si in an amount making a compositional ratio of the Mn with respect to the Si (i.e., Mn/Si) that is from 3.3 to 4.6; and C in an amount of from 1.5 to 3%; when the entirety is taken as 100% by mass. This Fe—Mn—Si—C powder is procurable inexpensively relatively; besides, ferrous sintered alloys, which are obtained using that, are better in terms of various characteristics than are conventional ferrous sintered alloys. Therefore, it is possible to intend to turn Cu-free ferrous sintered alloys, which are good in terms of their own characteristics, into low-cost ones.

Description

TECHNICAL FIELD[0001]The present invention is one which relates to a ferrous sintered alloy that is good in terms of strength and dimensional stability, and that makes it feasible to be free from Cu, or to be free from Ni, at low cost; and to a process for producing the same; as well as to a ferrous-sintered-alloy member that comprises that ferrous sintered alloy.BACKGROUND ART[0002]In order to cut the manufacturing costs of structural members such as mechanical parts, it is possible to think of utilizing a ferrous-sintered-alloy member in which a powder compact, which is made by pressure compacting a raw-material powder whose major component is iron, is heated to sinter it. When using a ferrous-sintered-alloy member, it becomes feasible as well to obtain products (or sintered bodies) that approximate the final configurations, and so it is possible to intend to reduce the manufacturing costs and material costs of structural members, due to cutting the machining processes, upgrading ...

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Benefits of technology

[0060]Here, Mn is an effective element in upgrading the strength of ferrous sintered alloy especially. When Mn is too less, its advantage is effected poorly. In reality, however, a ferrous sintered alloy with sufficient strength is obtainable even if Mn is a trace amount depending on the types of alloying elements being included in the raw-material powder. On the other hand, when Mn becomes excessive, the elongation of the resulting ferrous sintered alloy decreases so that the ductility declines, and then dimensional changes increase as well so that the dimensional stability is harmed. Hence, when the entire ferrous sintered alloy is taken as 100%, although the upper and lower limits of Mn are selectable arbitrarily within the aforementioned numerical range, it is preferable especially that numerical values, which are selected arbitrarily from the group consisting of 0.1%, 0.3%, 1.2%, 1.5%, 1.8% and 2.1%, can make the upper and lower limits.

[0061]Although Si contributes to upgrading the strength of ferrous sintered alloy, it greatly contributes to the dimensional stability of ferrous sintered alloy especially. In particular, this tendency appears greatly in a case where Si and Mn coexist with each other. Whereas Mn has such an action that tends to increase the dimensions of ferrous sintered alloy, Si has such an action that tends to decrease the dimensions of ferrous sintered alloy. It is believed that both of the elements that coexist with each other result in canceling those tendencies one another and then in

Problems solved by technology

Accordingly, they of themselves eventually come to result in raising the production costs of ferrous sintered alloys.

Furthermore, although Cu is an element that becomes the cause of hot brittleness in iron and steel materials, it is an element that is difficult to remove by smelting, and the like.

Consequently, ferrous sintered alloys that employ

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