JPH04180516A - Production of carburized and quenched gear - Google Patents

Abstract

PURPOSE:To improve fatigue strength by applying shot peening to the dedendum part of a carburized and quenched gear and removing the rough surface by means of electropolishing. CONSTITUTION:After shot peening is applied to the dedendum part of a carburized and quenched gear, the part between the surface, in which ruggedness is formed, and a position at a depth of about 20mum from the surface is removed by electropolishing. By this method, the maximum residual compressive stress formed by shot peening is allowed to appear, as it is, at the surface, by which a carburized and quenched gear excellent in fatigue strength and having high strength can be produced.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method of manufacturing a carburized and quenched gear.

[Conventional technology]

Shot peening is often applied to charcoal-hardened gears to increase their root fatigue strength and surface fatigue strength.

[Problem to be solved by the invention]

However, while shot peening has the effect of increasing fatigue strength by generating residual compressive stress due to plastic deformation of the surface, it also roughens the surface texture, which causes a slight decrease in fatigue strength due to residual compressive stress. There is.

The present invention has been proposed in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a high-strength carburized and quenched gear with excellent fatigue strength in which the maximum residual compressive stress obtained by shot peening is exposed as it is on the surface. With the goal.

[Means to solve the problem]

To this end, the present invention is characterized in that shot peening is applied to the root portion of the carburized and quenched gear, and then approximately 20 μm of the surface layer of this portion is removed by electrolytic polishing.

[Effect]

According to this configuration, the rough surface texture caused by strong shot peening on the surface is removed by electrolytic polishing.

As a result, the maximum residual compressive stress on the surface before electrolytic polishing is exposed as a large residual compressive stress on the surface as a result of electrolytic polishing, so the fatigue strength is lower than that of the conventional surface treatment using only beaning. It doubles compared to things.

5 Example 2 An example of the present invention will be explained with reference to the drawings. Figure 1 is a diagram of the residual stress distribution due to peening, and the second diagram shows the surface of a carburized and quenched specimen when peened. Fig. 3 is a cross-sectional view showing the unevenness of the surface when the second test piece was subjected to electrolytic polishing;
figure.

FIG. 5 is a micrograph showing the metal structure of the surface of the test piece shown in FIGS. 2 and 3, respectively.

As shown in Fig. 1, the residual compressive stress in the shot-peened portion of the tooth surface of a carbon-burning gear is approximately 50 kg/mm'' at the surface, but at a depth of approximately 20 μm from the surface. It shows a wedge-shaped distribution that reaches a maximum of 100 ig/mm'' and gradually decreases with increasing depth.

Therefore, in the present invention, after shot peening, the portion from the surface to a depth of about 20 μm is removed by electrolytic polishing.

In this case, after electrolytic polishing, the 20 μm depth shown in Figure 1 will be exposed as the surface, and the residual compressive stress on this surface will be lOOkg,z'mm''. surface residual compressive stress of 50 kg,
/mm2 doubles, indicating large fatigue strength.

Incidentally, when examining the unevenness on the surface of a test piece that had been subjected to two 37-tooth beaning, it was found that as shown in FIG. 2, unevenness with a maximum roughness Rmax = 5 μm had occurred.

When the surface of this test piece is subjected to electrolytic polishing, the maximum roughness Rmax=3 μm is obtained as shown in FIG. 4, and the size of the unevenness is halved compared to that shown in FIG.

When the surface structure of the test piece was examined using microscopic photographs, it was found that when shot peening was applied to the charcoal-charred surface shown in Fig. 2, rough concessions were observed as shown in Fig. 4; It was found that the surface after electrolytic polishing shown in FIG. 3 had a dense structure as shown in FIG.

〔Effect of the invention〕

In short, according to the present invention, after performing non-top peening on the tooth root portion of a carburized and hardened gear, the surface layer of this portion is removed by approximately 20 μm by electrolytic polishing, thereby achieving the maximum The present invention is extremely useful industrially because it provides a method for manufacturing a high-strength carburized and quenched gear with excellent fatigue strength in which residual compressive stress is directly exposed on the surface.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the distribution of residual compressive stress in the first step of an embodiment of the present invention, FIG. Figure 3 is a cross-sectional view showing the unevenness of the surface when the test piece in Figure 2 is subjected to electrolytic polishing, and Figures 4 and 5 are the cross-sectional views of the specimen shown in Figure 2.
FIG. 4 is a micrograph showing the metallographic structure of the surface of the test piece shown in FIG. 3. Applicant Mitsubishi Motors Corporation Representative Patent Attorney Masaru Tsukamoto Figure 1 View #t-3g distance βm Figure 3 Procedural Amendment 1990: February 1'? Director General of the Japan Patent Office
1゜2=- Engineering Case Description 1990 Patent Application No. 3082 b 2 No. 2 Title of Invention Method for manufacturing carburizing and quarrying gear 3 Person making amendment Relationship to the case Applicant postal code 1”o8 Address Tokyo 5-33-8 Shiba, Minato-ku Name (
628) Mitsubishi Motors Corporation 4 Agent Zip code 160 Address Odakyu Shinanomachi Apartment Room 205, 5-3 Minamimotomachi, Shinjuku-ku, Tokyo Subject of amendment Drawing 6 Contents of amendment (11 Figures 4 and 5) Correct as shown in the attached sheet.

Claims (1)

[Claims] A method for producing a carburized and quenched gear, which comprises performing shot peening on the tooth root portion of the carburized and quenched gear, and then removing approximately 20 μm of the surface layer of this portion by electrolytic polishing.