Claims
- 1. A injection-molded product which has been sintered and heat treated and which consists of 0.5 to 3% by weight of at least one metal selected from the group consisting of Cr and Mn, 0.3 to 1% by weight of C, and a balance of Fe, said product having a Vickers hardness Hv of at least 700.
Priority Claims (2)
| Number |
Date |
Country |
Kind |
| 1-260068 |
Oct 1989 |
JPX |
|
| 2-177230 |
Jul 1990 |
JPX |
|
CROSS-REFERENCE TO RELATED APPLICATION
The present application is a divisional of application Ser. No. 591,976, filed Oct. 2, 1990, now abandoned.
The present invention relates to an alloy steel for use in injection-molded sinterings produced by powder metallurgy, which sinterings are particularly improved in hardenability.
Sinterings having three-dimensionally complicated shapes are currently manufactured by powder metallurgy using an injection molding process. This process comprises the steps of kneading a binder with a metal powder such as pure iron, an Fe-Ni system alloy, an Fe-Ni-C system alloy, high speed steel, precipitation-hardened steel, stainless steel, and sintered carbide, then injection-molding the kneaded mixture and then sintering the debindered molding. Sintered alloys produced by this method are in general, subjected to post treatment or working. In this regard, sizing, followed by treatments such as milling, swaging or punching, tapping, barrel-polishing, and the like, as well as heat treatments such as hardening-tempering, softening, magnetic annealing, aging, and HIP treatment (hot isostatic pressing), can be employed to thereby obtain the final products. There have been, widely increasing demands that the as-sintered products have excellent post workability and that they possess favorable abrasion resistance, which should result from favorable surface hardenability upon hardening and tempering. Fe-Ni-C alloys have been considered to be the best at achieving such results. In this regard, sintered Fe-Ni-C alloys have good post workability indeed; however, their hardenability is yet to be improved. That is, it is not possible to obtain an oil-hardened and tempered product therefrom which yields a hardness (Hv) which exceeds 700, and therefore the abrasion resistance is a disadvantage.
It is an object of the present invention to provide an alloy steel for use in injection-molded sinterings produced by powder metallurgy which exhibits post workability which is comparable to that of Fe-Ni-C alloys and which at the same time yields a surface hardness exceeding Hv 700 after heat treatment.
The aforementioned object is accomplished by an alloy steel for use in injection-molded sinterings produced by powder metallurgy, which comprises, by weight, from 0.5 to 3% of Cr and/or Mn, from 0.3 to 1% of C, and a balance of Fe.
The alloy of the present invention comprises Cr and/or Mn as essential elements for improving hardenability, and C also as an essential element to maintain favorable hardenability. When the Cr and/or Mn accounts for less than 0.5% by weight, and/or C for less than 0.3% by weight, the hardenability of the resulting alloy remains still unsatisfactory; when the amount of Cr and/or Mn exceeds 3% by weight, and/or that of C exceeds 1% by weight, the post-workability is impaired since the resulting as-sintered product becomes too hard. Accordingly, the Cr and/or Mn content is set to a range of from 0.5 to 3% by weight and C content is confined in the range of from 0.3 to 1% by weight.
The object of the present invention is now achieved by preparing a metallic powder as above stated and sintering the injection-molding obtained therefrom following a powder metallurgy process.
US Referenced Citations (3)
Divisions (1)
|
Number |
Date |
Country |
| Parent |
591976 |
Oct 1990 |
|
Patent Grant
5141554
