JPH075930B2 - High precision sintered parts manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a method for producing a high-precision sintered part having wear resistance and toughness.

<Prior Art> Conventionally, in a method of manufacturing a sintered component, sizing is a normal process when powder molding-sintering is performed to obtain a product with high dimensional accuracy. Then, in order to obtain a material having higher wear resistance and toughness and a high hardness, heat treatment such as carburizing, quenching, and tempering is performed thereafter.
After this heat treatment, those having insufficient dimensional accuracy are usually further subjected to machining such as grinding.

<Problems to be solved by the invention> However, in the conventional method of producing a sintered part having high toughness, high strength, and wear resistance, in order to perform heat treatment after sizing, non-uniformity of the sintered part, Due to holes and the like, it is difficult to obtain high dimensional accuracy. Then, in order to improve the precision thereof, it is usually necessary to perform mechanical processing such as grinding after the heat treatment, but there is a drawback that this is very expensive. Ordinary machining may be difficult depending on the shape of the sintered part.

In addition to this, sizing can usually be done with hardness (Hv).
Was less than 300, and sizing was difficult if the hardness was more than 300.

<Means for Solving Problems> The present invention has found a method of sizing sintered parts after quenching and tempering, which was considered to be impossible by the above-mentioned conventional methods, whereby high toughness and high strength were obtained. Therefore, we succeeded in obtaining a highly accurate sintered part having wear resistance at low cost.

That is, the present invention, in the production of sintered parts, powder molding,
After sintering, apply a carburizing inhibitor to the sizing part before quenching and perform partial carburizing, then temper it, and generate stress only in the sizing part to generate compression pressure in the hardened part. It is a method for manufacturing high-precision sintered parts characterized by sizing, applying carburizing prevention material to unnecessary places before quenching to perform partial carburizing, and generating stress in uncarburized places during sizing, The dimensional accuracy is improved by producing compressive stress in the hardened part.

And in order to ensure this partial carburization, it is desirable that the density of the material is 7.2 g / cm ³ or more.
It is preferable that the amount is not less than / cm ³ and it is preferably subjected to coring after sintering. Further, in order to improve the sizing property of the hardened sintered part, it is preferable to perform a phosphoric acid film treatment before the sizing.

<Action> In the present invention, the carburizing preventive material is applied to a portion that does not require hardness,
By carburizing only the places that require hardness such as wear resistance and then quenching, sizing can be easily performed on the places that are not carburized, and compressive stress is generated, which causes cracks in the quench-hardened part. It is possible to deform it without generating it.

In the above, in order to make partial carburization more reliable, it is preferable to reduce the number of continuous voids, for which the density is 7.2 g / cm ³
The above is effective. There are various methods for increasing the density to 7.2 g / cm ³ or more, but the coining method is the most effective for setting the required point to the required density.

In order to improve the sizing property, it is also preferable to perform a phosphoric acid film treatment on the surface, which can improve the surface lubricity and prevent baking of the mold and parts. If the sizing property is particularly difficult due to the shape of the part, etc., set the hardness after full-face carburizing, quenching, and tempering to Hv300-500 so that the elongation property of the hardened part of the part is 1% or more to facilitate sizing. Good.

Further, the alloy composition of the parts is preferably low carbon and low alloy steel for improving the density and sizing after heat treatment.

<Example> 55 mmφ × 37 mmφ × 10 m of composition of 2% Ni-0.5% Mo-balanced Fe
Sintered parts were manufactured using the conventional method shown in Table 1 and the steps and conditions according to the method of the present invention using the parts of m size.

The results are shown in Table 1.

<Effects of the Invention> As described in detail above, according to the method of the present invention, it is possible to obtain a high-precision sintered part having wear resistance and toughness, and it is possible to obtain a cam ring for a vane pump or a pump rotor using a trochoid curve. The pump parts such as the outer rotor can be manufactured with high wear resistance and high precision without the need for expensive grinding, and the industrial value thereof is very large.

Claims (1)

[Claims] 1. In the production of a sintered part, after powder molding, sintering, and before quenching, a carburizing inhibitor is applied to the sizing portion to carry out partial carburizing and then tempering, and further only to the sizing portion. A method for producing a high-precision sintered component, which comprises sizing so as to generate stress to generate a compression pressure in a hardened part.