JPH0112812B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention aims to increase the hardness of the surface layer of extremely small steel balls (hereinafter simply referred to as steel balls) made of hardened steel with a diameter of 0.6 to 3 mm, thereby increasing the compressive residual stress. The present invention relates to a surface hardening treatment method for obtaining a layer.

(Prior art) It is widely known that the rolling fatigue life of bearings can be extended by increasing the hardness of the surface layer of bearing parts made of ordinary hardened steel and creating a large compressive residual stress layer. A typical method for this purpose is disclosed in Japanese Patent Publication No. 49-38406.

In other words, this means does not require special carburizing or nitriding treatment on bearing parts made of ordinary hardened steel, but by simultaneously processing the rolling surface of bearing parts before quenching by cold rolling, or The surface portion of the raceway surface of a bearing component that has been formed into a required shape in advance is subjected to mechanical hardening processes such as cold rolling, shot pinning, shot blasting, and tumbler to eliminate dislocations and atoms on the surface portion of the raceway surface. A hardened layer with increased lattice defects such as vacancies is formed, and the amount of dissolved carbon and alloying elements in the hardened layer portion is increased during quenching to reach the Ms point (the temperature at which martenside transformation begins during the cooling process of quenching). The rolling fatigue life of the rolling fatigue life is extended by making the stress lower than that inside the rolling surface and creating a large compressive residual stress layer on the surface of the raceway.

(Problems to be Solved by the Invention) However, although the above-mentioned means are extremely effective means in themselves, on the other hand, generally, the method is formed before quenching to form a hardened layer, and then during quenching, Because it increases the amount of dissolved carbon and alloying elements in the hardened layer, its shape tends to change after quenching, making it difficult to obtain a perfect circle, and the structure tends to collapse, resulting in a loss of mechanical strength. It is inherent.

The present invention has focused on such problems, and has solved the aforementioned problems by finding an appropriate mechanical surface hardening means after quenching and tempering, thereby extending the rolling fatigue life of bearings and reducing the occurrence of surface flaws due to handling of steel balls. The purpose is to reduce the number of

(Means for Solving the Problems) That is, the feature of the present invention that achieves the above object is that, as shown in FIG. After quenching and tempering, the steel ball is housed in the lower part of the cylinder 2, a pipe 3 is provided in the center of the cylinder, and the steel ball B in the lower part of the cylinder is blown up into the pipe 3 from the upper end of the pipe. This is a method in which the ball is sprayed onto the shielding plate 4 at the top, which is slightly difficult to reach, and allowed to fall naturally to the bottom of the hitting cylinder, and this operation is repeated to hit the entire surface of the steel ball.

Here, the steel balls treated in the present invention have a diameter of
It is a steel ball made of hardened steel with a diameter of 0.6 to 3 mm, and it is important that it is hardened and tempered before being placed into the cylinder.

If it is not hardened, the surface is likely to become uneven, which will impede quality.

In addition, the structure of the cylinder needs to include a pipe in the center of the interior that serves as a passage for blowing up steel balls, and a shielding plate that blocks the steel balls being blown up and allows them to fall naturally to the sides. There must be enough room between the top end of the pipe and the shielding plate for the steel ball to collide with the steel ball, turn to the side, and fall naturally.

This margin is not necessarily constant depending on the size of the steel ball and the pressure of the air blown up, but it is sufficient to provide about 40 mm.

Also, the pressure to blow up the steel ball should be selected depending on the hitting conditions, but in practice it should be 3 to 5 kgf/cm ²
It is the rank.

Then, the method of the present invention is continued by repeating the blowing up by the jetted air, hitting the shielding plate, and falling naturally downward, and the processing time is 2 to 5 hours. Of course, it goes without saying that it is not limited to this.

The diameter of the pipe is set appropriately depending on the conditions such as the diameter of the steel ball, but for example, the diameter is 316 mm and the height is 840 mm.
In the case of a steel cylinder, the central steel pipe has an inner diameter of 10
mm, outer diameter 50mm, height 370mm, and 1
The throughput per cycle is 20-100Kg.

(Function) When a steel ball is to be processed by the method described above, the steel ball is quenched and tempered, and then the steel ball is housed in the lower part of the cylindrical body 2.

In this state, when compressed air is injected into the pipe inside the cylinder by an appropriate drive source as injection air, the steel balls flow in from both sides of the lower part of the pipe, are blown up inside the pipe, and hit the shielding plate at the upper end. It naturally falls downward from the side as shown by the arrow.

Since the steel balls to be processed are accumulated in the lower part of the cylinder, the falling steel balls will fall on top of them and be struck again.

Thereafter, by repeating the process of flowing into the pipe, blowing up, hitting, and falling naturally for a predetermined period of time, the entire surface of the steel ball will be hit uniformly.

(Example) Hereinafter, specific embodiments of the method of the present invention will be described with further reference to examples of implementation apparatus shown in the accompanying drawings.

First, regarding the implementation apparatus, FIG. 1 shows an example of an apparatus for implementing the method of the present invention, in which a cylinder 2 held on a holding table 1 and used to implement the present invention is arranged.

The cylinder body 2 consists of a lower cylinder body 2a which is the main part thereof, and an upper cylinder body 2b which is fitted into the upper part of the lower cylinder body 2a, and which are separable from each other. The steel ball is removed from the body 2a and placed into the lower cylindrical body 2a.

A steel pipe 3 is erected in the center of the lower cylindrical body 2a, and a jet air inflow pipe 6 connected to an external compressed air source (not shown) is connected to the lower end of the pipe 3. A shielding plate 4 made of a cemented carbide steel plate is provided above the pipe 3 with a required gap.

The upper cylindrical body 2b is provided with an escape 5 to release the jet air that has flowed into the pipe as shown by the arrow, and the lower cylindrical body 2a can be raised and lowered by a lever 7, so that the inside of the pipe can be raised and lowered. We are trying to make it easier to take out the steel balls.

Next, when carrying out the treatment of the present invention using the above-mentioned apparatus, first, the steel balls to be treated are quenched and tempered, and then the upper cylinder 2b of the cylinder 2 is removed and the required amount of steel balls is removed. Enter B.

Then, the injection air flows in from the lower part of the pipe 3,
At the same time, a steel ball is made to flow in through the gap between the lower end of the pipe and the cylindrical body 2, and the jet air blows the steel ball up through the pipe 3, causing the air to escape upward, while the steel ball collides with the shielding plate 4 and is ejected to the side. , let it fall naturally downward.

Thereafter, by repeating this process, the steel balls positioned at the inner bottom of the cylinder 2 are sequentially blown up, collided with each other, and allowed to fall naturally to undergo a hardening process. After the required time has elapsed,
Stop.

In this way, when the processing is completed, operate the lever 7,
The lower cylindrical body 2a is brought down and the treated steel balls are taken out.

Thereafter, the steel balls taken out are completed into products according to normal processes such as polishing.

FIGS. 2 and 3 show the relationship between hardness and depth from the surface, as well as the distribution of compressive residual stress, for steel balls with a diameter of 3 mm that have been surface hardened as described above.

First, in FIG. 2, it can be seen that the hardness of the surface layer of the steel ball hardened by the method of the present invention increases by more than HV30 compared to the case without surface hardening, and approaches HV890.

Moreover, it is understood from FIG. 3 that a good compressive residual stress layer can be obtained in the surface layer within about 25 μm from the surface.

(Effect of the invention) As described above, the present invention is made of hardened steel with a diameter of 0.6~
In this method, after quenching and tempering a 3 mm microscopic steel ball, mechanical surface hardening treatment is performed using air jet peening. It has a remarkable effect on improving the quality of conventional steel balls, extending the rolling fatigue life of bearing parts, and reducing surface flaws caused by handling of steel balls. There is expected.

In addition, since the method of the present invention involves quenching and tempering in advance as described above, the smoothness of the surface is ensured, and the surface does not deform due to blowing up, hammering, or natural falling. Furthermore, since the steel balls are rotatable, uniform hardening can be applied to the entire surface, which is extremely effective in improving quality.

[Brief explanation of drawings]

FIG. 1 shows one of the apparatuses for carrying out the method of the present invention.
A front cross-sectional schematic diagram showing an example, FIG. 2 is a hardness distribution diagram of the steel ball surface layer, and FIG. 3 is a residual stress distribution diagram of the steel ball surface layer. 2... Cylindrical body, 3... Pipe, 4... Shielding plate.

Claims (1)

[Claims] 1 Processing of extremely small steel balls with a diameter of 0.6 to 3 mm made of hardened steel. After the extremely small steel balls are quenched and tempered, they are housed in the lower part of a cylinder and are injected into a pipe provided at the center of the cylinder. It is blown up by air, sprayed and hit against the shielding plate at the upper end of the pipe, and allowed to fall naturally from the upper end onto a very small steel ball housed in the lower part of the cylinder, and this process is repeated to hit the entire surface of the steel ball. A surface hardening treatment method for extremely small steel balls.