JPH0324257A - Production of bearing parts - Google Patents

Abstract

PURPOSE:To inexpensively produce long service life bearing parts causing no deterioration in hardness at the time of high-temp. tempering treatment by applying carbonitriding treatment to bearing parts composed of high-carbon chromium bearing steel so that specific surface carbon concentration and specific nitrogen concentration are obtained and further exerting hardening. CONSTITUTION:Bearing parts are formed by subjecting a stock of high-carbon chromium bearing steel to rolling and then to forging. Subsequently, carbonitriding treatment is applied to the above bearing parts, by which surface carbon concentration and surface nitrogen concentration are regulated to 1.2-1.8wt.% and 0.3-1.0wt.%, respectively. Then, the hearing parts are hardened and further subjected, if necessary, to tempering at a temp. as high as service temp. or above. C and N allowed to penetrate into the surface of the above bearing parts are infiltrated into interstice in Fe lattices and increase surface hardness, and further, this surface hardness is not dissipated even by high-temp. tempering. By this method, the long-life bearing parts can be obtained while obviating the necessity of the use of expensive heat resisting steel, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention is particularly useful when the ambient temperature or bearing temperature is between 150 and 150°C.
The present invention relates to a method of manufacturing bearing components used to assemble bearings suitable for use in conditions of 300°C.

Prior Art and Problems of the Invention Bearing parts are usually formed by rolling a material made of high carbon chromium bearing steel such as JISSU J2 and then hot, warm or cold forging, and then It was manufactured by subjecting it to a hardening treatment to improve its performance.

By the way, if the ambient temperature or bearing temperature is 150-300℃
Bearing parts used in bearings used under conditions such as
Dimensional changes may occur during use. In order to prevent this dimensional change, conventionally, after the above-mentioned quenching treatment, tempering was performed at a temperature 50° C. or more higher than the operating temperature.

However, when tempering is performed at a high temperature of 200°C or higher,
There is a problem that the hardness decreases and the life span decreases.

Therefore, it has been considered to manufacture the device using heat-resistant steel such as AISI M50 as the material, but in this case, there is a problem that the cost increases.

An object of the present invention is to provide a method for manufacturing a bearing component that solves the above-mentioned problems.

Means for Solving the Problems A method of manufacturing a bearing component according to the present invention involves forming a bearing component from high carbon chromium bearing steel, and then subjecting it to carbonitriding treatment to reduce the surface carbon concentration to 1.2 to 1.8. It is characterized by setting the weight percent and surface nitrogen concentration to 0.3 to 1.0 weight percent, and further quenching.

In the above, C and N are supersaturated in the bearing parts made of high carbon chromium bearing steel by carburizing and nitriding, so that even if the bearing parts are hardened and then tempered at high temperatures, the hardness of the bearing parts is maintained. It has the property of preventing the decline of

In other words, when bearing parts made from high-carbon chromium bearing steel are subjected to carburizing and nitriding to make the surface layer supersaturated with C and N, C and N invade the voids in the Fe lattice, causing the lattice to deteriorate. Distortion increases. This lattice strain increases the hardness. Moreover, this lattice strain is extremely stable in terms of temperature, and does not disappear even if tempering is performed at a high temperature of 200° C. or higher. However, if the surface carbon concentration and surface nitrogen concentration of the bearing component are below the above lower limit values, the above effects cannot be obtained, and if they exceed the upper limit values, abnormal phases such as retained austenite and free carbides will precipitate on the surface. Hardness decreases or becomes brittle. Therefore, the carbonitriding treatment should be performed so that the surface carbon concentration is within the range of 1.2 to 1.8% by weight and the surface nitrogen concentration is within the range of 0.3 to 1.0% by weight.

The above-mentioned carbo-nitriding treatment is performed alone or in combination with carburizing treatment or nitriding treatment. Specifically, there are, for example, the following five methods.

■ A method of performing carbo-nitriding treatment at a temperature range of 800 to 900°C.

(2) A method in which a carburizing treatment is performed in a temperature range of 900 to 950°C, and then a carbonitriding treatment is performed in a temperature range of 800 to 860°C.

(2) A method in which nitriding is carried out in a temperature range of 750 to 800°C, and then carburizing is carried out in a temperature range of 800 to 900°C.

■ In the method of ■ above, after the carburizing treatment, an additional 800
A method of performing carbonitriding treatment in a temperature range of ~900°C.

(2) A method in which nitriding is performed in a temperature range of 750 to 800°C, and then carburizing and nitriding is performed in a temperature range of 800 to 900°C.

Among the above five methods, methods (1) to (2) are preferred.

Moreover, in the above, sub-zero treatment may be performed after oil quenching. When sub-zero treatment is performed, retained austenite transforms into martensite, resulting in even greater hardness.

Finally, the ambient temperature or bearing tolerance during use (
Bearing parts are manufactured by tempering at a temperature that is 50°C or more higher than 150°C to 300°C.

Note that bearings having bearing parts manufactured by the method of the present invention are not only used under conditions where the ambient temperature or bearing temperature is 150 to 300°C, but also under normal temperature conditions. Available for use.

Effects of the Invention Even if a bearing component manufactured by the method of the present invention is subjected to a tempering treatment at a high temperature, its hardness will not decrease. Therefore, the life of a bearing with a bearing component manufactured by the method of the invention is significantly improved compared to a bearing with a bearing component manufactured by a conventional method. Moreover, the cost is lower than that using heat-resistant steel.

Example Examples of the present invention will be shown below along with comparative examples.

From high carbon chromium bearing steel (JIS S U J 2),
The bearing parts were formed in the usual manner. The bearing parts were then subjected to heat treatment under the conditions shown in the table below, and the surface Rockwell C hardness (HRC), surface carbon concentration, and surface nitrogen concentration were measured. In addition, a bearing was assembled using each bearing part, and the bearing was subjected to a load of 5 at the test temperature shown in the table below.
A life test was conducted under the conditions of 00 kgf and 2000 rpm, and the LIO life was determined with a calculated life of 240 hours.

These results are also summarized in the table below.

(Left below) As is clear from the results in the table above, the bearing parts manufactured by the method of this invention have a harder surface than those manufactured by the conventional method, and the bearing parts assembled using this The lifespan of has been significantly improved.

Further, the pre-tempering treatment was performed under the conditions of Examples 1 and 2 and Comparative Example 1 and Comparative Example 2, and subsequent tempering treatments were performed at various temperatures to adjust the tempering temperature and surface Rockwell C. We investigated the relationship with hardness. The results are shown in the drawing.

As is clear from the drawings, at each tempering temperature, the surface hardness of bearing parts manufactured by the method of the present invention is higher than that of bearing parts manufactured by the conventional method, and even at higher tempering temperatures, the surface hardness remains. The degree of decrease in temperature is small.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the tempering temperature and the Rockwell C hardness of the surface when the tempering treatment is performed at various temperatures. Above Figure 1

Claims (1)

[Claims] After bearing parts are formed from high carbon chromium bearing steel, they are carburized and nitrided to reduce the surface carbon concentration to 1.2 to 1.8.
A method for producing a bearing component, which comprises adjusting the weight percent and surface nitrogen concentration to 0.3 to 1.0 weight percent, and further quenching.