JPH093546A - Induction hardening method - Google Patents

Abstract

PURPOSE: To form a hardened layer having uniform depth on a surface of projecting ad recessed parts and to improve the quality of a product, in an induction hardening method. CONSTITUTION: A addendum 13 of gear 11 is heated by a prescribed first time with a first output value according to the vol. of the recessed part with a comparatively low first high frequency induction current concentrating an induction eddy current on the addendum. An addendum 14 is heated by a second time shorter than the first time with second output value according to the vol. of the projecting part with a second high frequency induction current higher than the first high frequency induction current concentrating the induction eddy current on the addendum. By this method, the hardened layer 15 having almost uniform depth is formed on the surfaces of the addendum 13 and the addendum 14 of the gear 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction hardening method for forming a hardened layer having a predetermined depth by applying induction hardening to a member such as a gear, a rack, or a spline having an uneven surface.

[0002]

2. Description of the Related Art FIG. 3 schematically shows a conventional gear machining operation.

As shown in FIG. 3, the gear is machined 10
1-assembly work 102-transportation work 103-gas carburizing and quenching 104-transportation work 105-disassembling work 106-polishing work 107. In this working process, the gas carburizing and quenching 104 is a process for diffusing carbon on the surface of the gear. By hardening after carburizing to form a hardened layer, the surface has high wear resistance and rich toughness. It is for manufacturing a gear having a core.

However, in this gas carburizing and quenching 104, since many gears are heated in the furnace, the heat treatment requires a long time and a large amount of energy (electricity, electricity,
(Gas) is used, and there is a problem that the cost becomes high. Further, since a large number of gears are processed at one time, there is a problem that the transportation work such as supply to the furnace and discharge from the furnace becomes complicated, and the transport efficiency is poor and the gear manufacturing efficiency is not good. Further, there is a problem that energy loss becomes large when manufacturing a small amount of gears.

Therefore, as a surface hardening treatment for gears, an induction hardening method is considered in place of the gas carburizing hardening.

FIG. 4 shows an outline of an apparatus showing a general induction hardening method.

As shown in FIG. 4, a coil 113 is arranged in a spiral shape along the surfaces of the components 111 and 112, and a high frequency current of 1 to 500 kHz is passed through the coil 113. Then, the eddy current 115 mainly induced by the alternating magnetic flux 114 is concentrated on the surface layers of the components 111 and 112, and the surface layers are rapidly heated by the Joule heat of this current.
Then, when the quenching temperature is reached, quenching is performed by an appropriate method to quench-harden and a hardened layer is formed on the surfaces of the components 111 and 112.

[0008]

However, when the surface hardening treatment of the gear is performed by using the above-mentioned induction hardening method, the following problems occur. That is, as shown in FIG. 5, the gear 11 is configured such that a large number of teeth 12 are evenly formed on a disk-shaped outer peripheral surface. When surface-hardening the gear 11, the tooth top 13 and the tooth top 14 of the gear 11
Then, it is necessary to form the hardened layer 15 having substantially the same depth.
However, in the above-described induction hardening method, by passing a high frequency current through the coil 113 along the outer peripheral surface of the gear 11, the eddy current 115 induced by the alternating magnetic flux 114 rapidly heats and hardens the surface layer. Forming layers.

Therefore, as shown in FIG. 6 (a), when the heating time is short, the hardened layer 15 is formed only on the periphery of the tooth tip 14 of the gear 11 and the hardened layer 15 is formed on the tooth root 13. Not done. Therefore, there is a problem that the surface of the tooth base 13 cannot have a sufficient hardness, and wear is caused early during use. On the other hand, as shown in FIG. 6B, when the heating time is long, the hardened layer 1 is formed on the entire teeth 12 of the gear 11.
5 is formed. Therefore, the tooth top 13 and the tooth tip 14
Although it has a sufficient hardness on the surface of the tooth 12, a hardened layer is formed up to the core of the tooth 12, and the tooth 12 becomes brittle and may be damaged if an impact or the like acts during use.

The present invention solves such a problem, and an object of the present invention is to provide an induction hardening method in which a hardened layer having a uniform depth is formed on the surface of irregularities to improve the quality of products. And

[0011]

The induction hardening method of the present invention for achieving the above object is an induction hardening method of forming a hardened layer having a predetermined depth by subjecting a member having an uneven portion on its surface to induction hardening. In above, after heating with a relatively low high frequency current that concentrates an induced eddy current on the concave surface of the member, heating with a relatively high high frequency current that concentrates an induced eddy current on the convex surface of the member Then, a hardened layer having a substantially uniform depth is formed on the surface of the uneven portion of the member.

Further, the induction hardening method of the present invention is an induction hardening method in which a member having an uneven surface is subjected to induction hardening to form a hardened layer having a predetermined depth. The induction eddy current is concentrated on the convex surface of the member after heating for a predetermined first time at a first output value corresponding to the volume of the concave portion by a relatively low first high-frequency current that concentrates the current. First
A second high-frequency current higher than the high-frequency current causes the second output value corresponding to the volume of the convex portion to heat for a second time shorter than the first time, thereby hardening the surface of the uneven portion of the member to a substantially uniform depth. It is characterized by forming a layer.

[0013]

[Function] By heating with a relatively low high-frequency current that concentrates the induced eddy current on the concave surface of the member, and then by heating with a relatively high high-frequency current that concentrates the induced eddy current on the convex surface, The hardened layer having a substantially uniform depth is formed only on the surface of the uneven portion of the member, and the hardened layer is not formed inside.

After heating for a predetermined first time at a first output value corresponding to the volume of the recess by a relatively low first high frequency current that concentrates the induced eddy current on the surface of the recess of the member, the surface of the protrusion is heated. On the other hand, the second high frequency current higher than the first high frequency current for concentrating the induced eddy current is used to heat the second output value corresponding to the volume of the convex portion for a second time shorter than the first time, so that this member can be heated in a short time. A hardened layer having a substantially uniform depth is formed on the surface of the uneven portion.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic diagram of gear teeth heat-treated by an induction hardening method according to an embodiment of the present invention, and FIG. 2 is a graph showing heating temperature with respect to heating time for carrying out the induction hardening method of the present embodiment. Indicates. It should be noted that the members having the same functions as those of the related art are designated by the same reference numerals, and the duplicated description will be omitted.

In the induction hardening method of this embodiment, as shown in FIG.
After heating by the high frequency current at the first output value according to the volume of the tooth root 13 for a predetermined first time, the tooth tip 14 of the gear 11 is heated by the second high frequency current higher than the first high frequency current. By heating at a second output value according to the volume of 14 for a second time shorter than the first time, a hardened layer 15 having a substantially uniform depth is formed on the tooth surface of the gear 11.

More specifically, the induction hardening gear 11 has a module 2.0, a pressure angle of 14.5 °, a number of teeth of 74, a standard pitch circle diameter of 166.8 mm, and a tooth depth of 6 mm. When induction hardening is applied to the gear 11, first, as shown in FIGS. 1 (a) and 2, a relatively low first high frequency current of 3 kHz is applied at a first output value of 1000 kw for a predetermined first time 1 The gear 11 is heated (preheated) to 800 ° C. for 0.8 s. Then, the hardened layer 15 having a predetermined depth is formed only on the tooth root 13 of the gear 11. Next, FIG. 1 (b)
As shown in FIG. 2, the current of the second high frequency 200 kHz higher than the first high frequency 3 kHz is applied to the gear 11 at the second output value 600 kw for the second time 0.8 s shorter than the first time 1.8 s.
Is heated to 900 ° C. (main heating). Then, the gear 11
The hardened layer 15 having a predetermined depth is formed only on the tip 14 of the tooth.

Therefore, a hardened layer 15 having a depth of 0.3 to 0.6 mm is formed at the root 13 of the gear 11, and a hardened layer 15 having a depth of 0.3 to 0.6 mm is also formed at the tooth tip 14. The hardened layer 15 having a substantially uniform depth is continuously formed on the gear 11.

As described above, according to the induction hardening method of the present embodiment, the first lower comparatively lower than the tooth root 13 of the gear 11 is used.
A high-frequency current is used to heat the first output value for a predetermined first time to form a hardened layer only on the tooth root 13, and thereafter, the tooth tip 1
4 is heated by the second high frequency current higher than the first high frequency current at the second output value for the second time shorter than the first time to form the hardened layer only on the addendum 14 of the gear 11. The hardened layer 15 having a substantially uniform depth can be formed on all the surfaces.

In the above-mentioned embodiment, the member to be induction hardened is a gear. However, the member is not limited to this, and any member having an uneven portion on the surface such as a rack or spline may be used.
By induction hardening according to the induction hardening method of the present invention, a hardened layer having a predetermined depth is formed, and the same effects as the above can be obtained.

[0022]

As described above in detail with reference to the embodiments, according to the induction hardening method of the present invention, after heating with a relatively low high frequency current for concentrating the induced eddy current on the concave surface of the member, By heating with a relatively high high-frequency current that concentrates the induced eddy current on the surface of the convex portion, a hardened layer having a substantially uniform depth is formed on the surface of the concave and convex portion of this member. Only the surface of the uneven part of the member has a substantially uniform depth, is not formed inside, and manufactures a member consisting of a surface with high wear resistance and a core with high toughness. It is possible to improve.

Further, according to the induction hardening method of the present invention, a predetermined first output value corresponding to the volume of the recess is provided by the relatively low first high frequency current which concentrates the induced eddy current on the surface of the recess of the member. After heating for the first time, the second high frequency current, which is higher than the first high frequency current that concentrates the induced eddy current on the surface of the convex portion, produces a second output value corresponding to the volume of the convex portion, which is shorter than the first time. By heating for only 2 hours, a hardened layer having a substantially uniform depth is formed on the surface of the uneven portion of the member, so the member is subjected to induction hardening in two steps with different frequencies, output values and heating times. As a result, the hardened layer can be formed with a substantially uniform depth only on the surface of the uneven portion of this member.

[Brief description of drawings]

FIG. 1 is a schematic view of teeth of a gear heat treated by an induction hardening method according to an embodiment of the present invention.

FIG. 2 is a graph showing a heating temperature with respect to a heating time for carrying out the induction hardening method of the present embodiment.

FIG. 3 is a schematic view showing a conventional gear machining operation.

FIG. 4 is an apparatus diagram showing a general induction hardening method.

FIG. 5 is a schematic view of a gear that has been subjected to a surface hardening treatment.

FIG. 6 is a schematic view of a gear that has been surface hardened by a general induction hardening method.

[Explanation of symbols]

 11 gear 12 tooth 13 tooth root 14 tooth tip 15 hardened layer

Claims (2)

[Claims] 1. An induction hardening method for forming a hardened layer having a predetermined depth by subjecting a member having a concavo-convex portion to an induction hardening to a relatively low high frequency for concentrating an induced eddy current on the recessed surface of the member. After heating with an electric current, by heating with a relatively high high-frequency current that concentrates the induced eddy current on the convex surface of the member,
A method for induction hardening, comprising forming a hardened layer having a substantially uniform depth on the surface of the uneven portion of the member. 2. An induction hardening method for forming a hardened layer having a predetermined depth by subjecting a member having a concavo-convex portion on its surface to induction hardening, which is relatively low for concentrating induced eddy currents on the concave surface of the member. A second high voltage higher than the first high frequency current for concentrating the induced eddy current on the surface of the convex portion of the member after heating for a predetermined first time with a first output value according to the volume of the concave portion by the first high frequency current; By heating with a second output value corresponding to the volume of the convex portion by a high frequency current for a second time shorter than the first time, it is possible to form a hardened layer having a substantially uniform depth on the uneven surface of the member. Characteristic induction hardening method.