JPS6237320A - Manufacture of machined parts - Google Patents

Abstract

PURPOSE:To provide satisfactory machinability to steel stock and satisfactory strength to machined parts by heating the stock in the air, quenching it in water and subjecting the surface layer to tempering by high frequency heating, machining and induction hardening. CONSTITUTION:Steel stock for machined parts is heated in the air and quenched in water to regulate the internal hardness Hv to >=300. The surface layer of the stock is tempered by high frequency heating to lower the hardness Hv to <=300, and after the surface layer is machined, the hardness Hv of the surface layer is increased to >=300 by induction hardening.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a machined part, and more particularly to a method for manufacturing a part that undergoes a cutting process after being quenched and tempered.

[Conventional technology]

Conventionally, cut parts such as drive shafts, crankshafts, connecting rods, etc. are often hardened and tempered to improve their strength.

In this case, when quenching and tempering are performed after cutting,
In order to prevent decarburization and oxidation of the component surface, it is necessary to perform heat treatment in an atmosphere such as RX gas.

However, since the use of RX gas increases the cost of heat treatment, the conventional method has been to first quench and temper the material of the machined part in the atmosphere, and then perform the cutting process.

[Problem that the invention seeks to solve]

However, in the conventional method, there has been a problem in that the hardness of the part cannot be increased to Hv (Vickers hardness) or higher by heat treatment to avoid deterioration of machinability during cutting.

Further, even when higher hardness is required from the viewpoint of component strength, there is a problem in that the hardness must be lowered to Hv300 or less.

Therefore, an object of the present invention is to soften the surface layer of a part for cutting during cutting, and increase the hardness of the part to a value higher than a desirable value in terms of strength when the part is completed, thereby achieving both part strength and machinability. The purpose of the present invention is to provide a method for manufacturing machined parts that can be machined.

(Means for solving the problem) For this reason, the method for manufacturing a machined part according to the present invention is as follows:
The inside of the machined part is made to have a hardness of Hv300 or more, and only the surface layer part is machined with the hardness reduced to Hv300 or less, and then the surface layer is also increased to Hv300 or more. .

Specifically, the material of the cutting part made of steel is heated in the atmosphere and then quenched in water, the surface layer of the cutting part is tempered by high-frequency heating, and then the cutting part is subjected to the cutting process. The parts for cutting are induction hardened.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 is a graph showing the hardness distribution in the cross section of a drive shaft, which is a machined part manufactured by the method of the present invention.
FIG. 2 is a graph showing the hardness distribution in the cross section of the round steel bar material after tempering, FIG. 3 is a graph showing the hardness distribution in the cross section of the drive shaft manufactured by the method of the comparative example, and FIG. The figures are the same (a graph showing the hardness distribution in the cross section of the round steel bar material after tempering, and FIG. 5 is a front view showing the schematic structure of the drive shaft manufactured by the method of the present invention.

The drive shaft 2, which is a machined part according to the method of the present invention, is manufactured in the following order.

First, for the manufacture of drive shafts, a diameter of 26 fins, 545C
A round steel bar material (not shown) is prepared.

Next, this round steel bar material is heated to 880° C. in the atmosphere and then quenched in water.

Next, this round steel bar material is tempered by high-frequency heating at a frequency of 100 kHz, centering on the surface layer. As shown in FIG. 2, the hardness distribution in the cross section of the round steel bar material after tempering is Hv 200 near the surface layer (approximately 2 depths from the surface) and Hv 350 at the center.

Next, cutting is performed on the outer periphery of this round steel bar material to finish the drive shaft 2 into a desired shape. The cutting allowance removed by this cutting process is about 2 mm deep from the surface of the round steel bar material. Therefore, cutting can be easily performed within this range.

Next, drive shaft 2 finished in this way
is heated with high frequency at a frequency of 400 kHz to perform induction hardening on the surface layer.

This completes the heat treatment of the drive shaft 2.

The hardness distribution within the cross section of the drive shaft 2 is
As shown in the figure, the hardness of the surface layer has increased to HV400 or higher.

That is, the strength of the component as a whole is improved.

Although the present invention has been described above based on specific embodiments, it is not limited thereto, and various other embodiments can be considered by those skilled in the art within the scope of the claims.

For example, cutting parts can be applied not only to drive shafts but also to crankshafts, connecting rods, etc.

Moreover, the frequency of the high frequency can be set to an arbitrary value for tempering the surface layer, taking into account the cutting allowance of the cutting process.

(Comparative product) A drive shaft of the same shape and made of the same material as the product of the present invention was heated in the atmosphere as in the conventional method except for the tempering of the round steel bar material, and the other processes were the same as those of the product of the present invention. Manufactured using.

As shown in FIG. 4, the hardness of this comparative product during tempering is approximately Hv230, which allows cutting of the surface layer of the round steel bar material.

Further, as for the hardness distribution of the drive shaft manufactured by this method, as shown in FIG. 3, the internal hardness remains at about Hv200.

In other words, the internal strength of the parts is insufficient.

Next, measurements made to evaluate the performance of the machined parts according to the method of the present invention and the results thereof will be explained.

As is clear from a comparison between FIG. 1 and FIG. 3, the internal hardness of the drive shaft produced by the method of the present invention is increased by about Hv100 or more without impairing machinability compared to the comparative example.

Furthermore, the torsional strength of the drive shaft manufactured by the method described above was measured. The results are shown in Table 1 along with comparative examples.

Table 1 As is clear from this table, the torsional strength of the drive shaft manufactured by the method of the present invention is about 8% higher than that of the drive shaft manufactured by the method of the comparative example.
% has improved.

〔Effect of the invention〕

As explained above, the method for manufacturing a machined part according to the present invention involves increasing the hardness of the interior of the machined part to HV300 or higher, lowering the hardness only near the surface layer to HV300 or lower, and then performing cutting. Since the surface layer portion is also increased to 1-iv3oo or more, it is possible to achieve both component strength and machinability, which is an excellent effect.

[Brief explanation of drawings]

FIG. 1 is a graph showing the hardness distribution in the cross section of a drive shaft, which is a machined part manufactured by the method of the present invention.
FIG. 2 is a graph showing the hardness distribution in the cross section of the round steel bar material after tempering, FIG. 3 is a graph showing the hardness distribution in the cross section of the drive shaft manufactured by the method of the comparative example, and FIG. The figure is a graph showing the hardness distribution in the cross section of the round steel bar material after tempering, and FIG. 5 is a front view showing the schematic structure of a drive shaft manufactured by the method of the present invention. 2--------Driveshaft Applicant Toyota Motor Corporation Figure 1 Figure 2 Figure 8 Figure 4

Claims (1)

[Claims] The material of the cutting part made of steel is heated in the atmosphere and then quenched in water, the surface layer of the cutting part is tempered by high frequency heating, and then cutting is performed, and then the cutting part is A method for producing machined parts, characterized by induction hardening.