JPH0849014A - Method for manufacturing high hardness steel member having high toughness part - Google Patents

Abstract

PURPOSE:To attain the reduction in stages and energy and to attain the reduction in the cost in the production of many kinds in small quantities by heating the desired part to a tempering temp. for forming a high toughness part on a high strength steel, holding it to the temp. for certain time and thereafter executing cooling. CONSTITUTION:For example, a high toughness part 10b (hatched part) is formed on the inside of the tooth 10a of a gear 10 of eutectoid carbon to secure its toughness and to prevent the chipping of the tooth, and furthermore, the hardness of the surface layer part 10 is maintained to secure its wear resistance. For this purpose, in a liq. having the boiling poing higher than the tempering temp., e.g. in oil, electrodes 11 and 12 having a cross-sectional shape same as that of the hatched part 10b are abutted on both edge faces of the gear 10, and D.C. electric current is flowed. Thus, the application of tempering treatment to the place other than the high toughness part 10b can be prevented. By flowing the electric current to the place to form the high toughness part 10b, it is heated to the tempering temp. of the Al transformation point or below, and it is held to the same temp. for several second to several tens seconds and is thereafter cooled in a liq.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a high hardness steel member having a high toughness portion.

[0002]

2. Description of the Related Art Conventionally, in a gear used as a power transmission means, the wear resistance of the tooth surface is ensured in order to reduce the wear caused by meshing with another gear, and the tooth of the gear is prevented from being chipped. In order to do so, it is common to secure toughness (tenacity) inside the teeth.

In order to satisfy the above-mentioned demand, as disclosed on page 149 of "Machine / Metal Materials for Young Engineers-Supplemental Edition-" issued by Maruzen Co., Ltd. on November 30, 1979. It is generally practiced to carry out a carburizing treatment to harden only the surfaces of the gear teeth to improve wear resistance and ensure internal toughness.

Methods for carrying out carburizing include gas carburizing and solid carburizing. For example, in gas carburizing, the work is placed in a furnace and the carburizing gas such as propane or butane is used.
After holding at 00 to 950 ° C. for 0.5 to 10 hours, it is necessary to hold again at 100 to 200 ° C. for 1 to 3 hours to perform tempering.

On the other hand, in solid carburization, a work and a solid carburizing agent in which a charcoal powder is mixed with a promoter such as sodium carbide in an amount of 10 to 30% are used in a carburizing box made of an iron plate so that the carburizing agent is in good contact with the work. Fill it with a lid and put it in a furnace for 850-1
It is heated at 000 ° C. for 1 to 15 hours.

The time required for carburizing depends on the thickness of the carburized layer formed on the work and the material.

[0007]

As described above, the carburizing process requires a large number of man-hours and a large amount of energy for keeping the inside of the furnace constant at high temperature, resulting in high cost. For this reason, in order to reduce the cost, a large amount of works are carburized at one time, but in the case of a large number of products in small quantities, the cost is inevitably high.

It is a technical object of the present invention to provide a method for manufacturing a member which is low in cost, has a hard work surface, and has toughness secured in an arbitrary portion.

[0009]

In order to solve the above technical problems, the technical means taken in the invention of claim 1 is to heat a desired portion to a tempering temperature in order to form a high toughness portion in high hardness steel. Then, the temperature is maintained for a certain period of time and then cooled.

The technical means taken in the second aspect of the present invention is that the desired portion is sandwiched by electrodes to form a high toughness portion in high hardness steel, an electric current is caused to flow therethrough, and the material is heated to the tempering temperature and kept constant at the temperature. Hold for time and then cool.

The technical means taken in the invention of claim 3 is that the electric current is direct current so as to prevent tempering of the portion other than the desired portion to be the high toughness portion.

In order to prevent the oxidation of the work, the technical means taken in the invention of claim 4 is to carry out heating, holding and cooling in a liquid having a low electric conductivity and a boiling point higher than the tempering temperature. .

[0013]

According to the invention of claim 1, the desired portion for which high toughness is to be imparted to the high hardness steel is heated to the tempering temperature, held at that temperature for a certain period of time, and then cooled, whereby the desired portion is tempered. Is given.

In a second aspect of the present invention, a desired portion for imparting high toughness to high hardness steel is sandwiched by electrodes to pass an electric current,
The desired portion is tempered by heating to the tempering temperature, holding at that temperature for a certain period of time, and then cooling.

According to the third aspect of the present invention, by applying a direct current to the desired portion to be the high toughness portion, it is possible to prevent the portion other than the desired portion from being tempered.

According to the invention of claim 4, since the heating, holding and cooling are performed in the liquid, the work is not oxidized.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment according to the present invention will be described with reference to the drawings.

FIG. 1 is a model diagram of a workpiece being heated, and FIG. 2 is an enlarged view of gear teeth. In the figure, the gear 10 of the work, which is a high hardness steel, is eutectoid carbon steel, and has a hardness of about 600 to 800 in the Vickers hardness test. The gear 10 has a high toughness portion 10 inside the tooth 10a.
It is desirable to form b (hatched portion in FIG. 2) to secure toughness to prevent tooth chipping and to maintain the hardness of the surface layer 10c to secure abrasion resistance. Therefore, as shown in FIG. 1, an electrode having the same cross-sectional shape as the shaded portion in FIG. 2 on both end faces of the gear 10 in a liquid (for example, oil) having a low conductivity and a boiling point higher than the tempering temperature. 11 and 12 are brought into contact with each other, and a direct current is passed. Therefore, the high toughness portion 10b
It is possible to prevent tempering treatment from being applied to a portion other than the above. Further, the magnitude of the voltage and the current at this time may be freely set depending on the size of the portion to be heated and the processing time.

A portion to be the high toughness portion 10b is heated to a tempering temperature below the A1 transformation point by flowing an electric current, kept at that temperature for several seconds to several tens seconds, and then gradually cooled in a liquid. The temperature and holding time at this time may be freely set depending on the hardness of the high toughness portion 10b desired to be secured by tempering and the size of the portion. Alternatively, it may be taken out into the air for air cooling.

By the above method, the hardness of the portion to be the high toughness portion 10b is reduced by tempering while maintaining the hardness of the surface of the tooth 10a of the gear 10 to a Vickers type of about 300 to 500 to improve the toughness. be able to.

In this embodiment, since it is not necessary to carry out carburizing treatment, the number of steps and energy can be small, the cost can be reduced, and the processing is carried out one by one, so that it is possible to deal with a wide variety of products in small quantities. . Furthermore, since a current is applied to the desired portion 10b for which high toughness is desired to be heated to the tempering temperature, it is possible to easily perform a local treatment. Further, since the work is prevented from being oxidized because it is heated, held and cooled in the liquid, the surface of the gear layer 10 can be tempered while being cooled.
0c is prevented from being tempered.

In this embodiment, eutectoid carbon steel is used for the work, but it may be properly used depending on the application. Further, although the gear 10 is used for the work, it is not particularly limited to this and can be used for other metal products such as a shaft.

[0023]

According to the inventions of claims 1 and 2, since it is not necessary to carry out carburizing treatment, man-hours and energy can be reduced and the cost can be reduced, and at the same time, one by one can be processed. It can be applied to other products.

Further, in the second aspect of the present invention, since electric current is applied to the desired portion where high toughness is desired to be applied and heating is performed up to the tempering temperature, local treatment can be easily performed.

According to the third aspect of the present invention, by applying a direct current to the desired portion, it is possible to prevent the tempering process from being applied to a portion other than the desired portion.

In the invention of claim 4, since the work is prevented from being oxidized because it is heated, held, and cooled in the liquid, the tempering can be performed while cooling the surface of the high hardness member. As a result, the surface is prevented from being tempered.

[Brief description of drawings]

FIG. 1 shows a model diagram of a work being heated.

FIG. 2 shows a plan view of the gear teeth.

[Explanation of symbols]

 10 ... Gear (work) 10a ... Tooth 10b ... High toughness part 11, 12 ... Electrode

Claims (4)

[Claims] 1. A high hardness steel having a high toughness portion characterized in that a desired portion is heated to a tempering temperature to form a high toughness portion in high hardness steel, held at the temperature for a certain period of time, and then cooled. Manufacturing method of steel member. 2. In order to form a high toughness portion in a high hardness steel, a desired portion is sandwiched by electrodes, an electric current is applied, the tempering temperature is heated to the tempering temperature, the temperature is maintained for a certain time, and then the tempering is cooled. A method for producing a high hardness steel member having a characteristic high toughness portion. 3. The method for manufacturing a high hardness steel member having a high toughness portion according to claim 2, wherein the current is direct current. 4. The heating, the holding, and the cooling are performed in a liquid having a low electrical conductivity and a boiling point higher than the tempering temperature, according to any one of claims 1 to 3. Of manufacturing a high hardness steel member having a high toughness part.