JPS6048565B2 - High frequency heat treatment method - Google Patents

Description

[Detailed Description of the Invention] Recently, in heat treatment methods using high-frequency induction heating, a method in which steel parts are locally surface-hardened and then immediately tempered by induction heating is particularly effective in that it can contribute to shortening the process. Although there are many examples of industrial use, the present invention relates to a method of induction heating using a single-shot method for induction hardening and tempering using a semi-loop heating coil.

Conventionally, the method of performing dawn heating and tempering by induction heating generally used separate oscillators for dawn heating and tempering, but with the intention of reducing equipment costs, a single oscillator was used to perform dawn warming and tempering. A method has been adopted in which the heat treatment is completed in the process from loading to unloading by continuously performing reconstitution.

When performing heating and rapid cooling for dawning and then heating and cooling for tempering using the same heating coil using one oscillator, the object to be heated is, for example, S45CB with cross-sectional shape as shown in Figure 1
In the case of a flanged shaft, for example, a semi-loop type heating coil 2 as shown in FIG.
By rotating the object to be heated 1 around its axis inside the heating coil 2, the surface layer portion is induction heated over the entire circumference.

In order to perform induction heating over the entire surface of the object to be heated 1 at a uniform surface temperature and at the same heating rate, it is possible to perform induction heating over the entire surface of the object to be heated 1 at a uniform surface temperature and at the same heating rate. This is extremely difficult due to various factors such as the difference in level, shape, size, and ratio of diameter to length of each part of the R part (hereinafter referred to as the R part). In addition, even if the surface temperature of each part of the object to be heated 1 is approximately uniform and the rate of temperature rise can be made constant, the inside of the large diameter part 12, the R part 14, and other parts (small diameter part) The difference in the amount of heat loss due to heat conduction causes a difference in the amount of heat storage, and the cross-sectional temperature distribution does not necessarily show a uniformity, resulting in a difference in the depth of the hardened layer after quenching.
The hardening depth becomes shallower in the order of the other portions: the large diameter portion 12 and the R portion 14. In order to prevent this, when surface hardening of the heated object 1 is performed, cores 31, 3, 2, made of a ferromagnetic material such as ferrite or a laminated silicon steel plate as a heat-strengthening material are installed at required locations on the square pipe 21. 33
, 34 and 35 are installed as shown in FIG.
This is done as follows using . That is, when the object to be heated 1 is induction heated due to the dawn as described above, the stepped shape is designed and manufactured in such a shape that the temperature rise due to induction heating is slightly faster than in other parts. part 1
1, 13 The temperature 1 of the large diameter portion 12 and the R portion 14 first reaches the magnetic transformation point K as shown in FIG. After that, the temperature rise slows down. Then, the temperature 2 of the other parts eventually reaches the magnetic transformation point K. At the time T when the temperature 2 of this part reaches within the predetermined quenching temperature range K, ~K2,
Stop induction heating. Immediately, the surface layer of the object to be heated 1 is cooled with a cooling liquid, for example, a 3% soluble PQ liquid, and the quenching is completed. However, when the same heating coil 2 is used to temper the hardened layer of the object to be heated 1 by applying a high-frequency current with a lower power density than during quenching after quenching, the temperature rise curve is It will look like Figures 3 and 4.

1 and 3, 2 and 4 indicate the temperature rise of the corresponding parts, including the stepped portions 11 and 13, and the large diameter portion 12.
As shown in FIG. 4, the difference between the temperature 3 of the R portion 14 and the temperature 4 of the other portions becomes larger as the heating time becomes longer.

In order to eliminate this drawback, measures are taken to reduce the temperature difference as much as possible by utilizing heat conduction loss, radiation loss, etc. through low power density and long-time heating. However, when the heating coils are the same, Since there is no change in the trend, considerable temperature differences occur. As a result, uneven softening occurs due to temperature differences, and surface hardening and internal hardness distribution become uneven, making it impossible to achieve the desired quality. In order to eliminate this inconvenience, as a means of bringing 3 and 4 in FIG.
There is a method of lowering the temperature to match temperature 4.

The former is carried out by adding and replenishing the heat-strengthening material to the heated part corresponding to temperature 4, and the latter is carried out by removing part or all of the heat-strengthening material in the heated part corresponding to temperature 3. can be easily determined by conducting some experiments. The present invention operates a heat-strengthening material support part (hereinafter referred to as "support part") so that the heat-strengthening material attached to the support part can be attached to and detached from the heating coil during heating for tempering. It is an object of the present invention to provide an induction heat treatment method that can perform tempering with improved quality and improve the efficiency of the heat treatment operation by eliminating the above-mentioned drawbacks of The present invention will be described in detail below based on drawings showing embodiments thereof.

FIG. 5 is a partially exploded plan view schematically showing the main parts of the heating coil and the object to be heated according to the present invention.

In the figure, reference numeral 1 denotes a heated object similar to the conventional one shown in FIGS. 1 to 3, 2 a heating coil itself similar to the conventional one, and cores 31', 32', 33', similar to the conventional one, 34
', 35' are fixed to the heating coil full 2' in the same manner as in the prior art. The rectangular vibrator 21' of the heating coil 2' has a core 36 made of ferrite or laminated silicon steel plate similar to the cores 31' to 35', which can be attached and detached, for example, in the following manner. That is, cores 36, 36 are core 3
1' to 34'. In a substantially similar example, a support part 36L361 is formed to have a U-shaped cross section and is provided at the tip of, for example, an air cylinder 4, 4' for driving, which is disposed at an appropriate position on the side of the square vibrator 21', 21'. It has been installed through.
When the heating coil 2' is used to harden the object 1 to be heated, the air cylinders 4 and 4 are not operated, and when tempering is performed, compressed air is supplied to the air cylinders 4 and 4 and the air cylinders 4 and 4 are operated. There is. As a result, in the former case, the rods 41, 41 and the cores 36, 36 are in the positions shown by solid lines in FIG.
, 21'. On the other hand, in the latter case, the rods 41, 41 and the cores 36, 36 are shown in FIG.
At the position shown by the dotted chain line, the cores 36, 36 are connected to the core 31.
The square vibrators 21' and 21' are attached to the required positions 211' and 211' in substantially the same state as those of ' to 34'. In addition, the shape and dimensions of the cores 36, 36 and the square vibrator 21'
, 21' can be easily determined by conducting some experiments. Using the heating coil 2' constructed as described above and the conventional heating coil 2, the surface layer portion of the similarly formed object to be heated 1 was heat-treated, and the results are as follows.

That is, first, the heating coils 2' and 2 have an output of 150 KW) an input of 140 to 150 KW from an inverter with a frequency of 10 KHz.
Immediately after induction heating the surface layer of the object to be heated 1 by supplying high-frequency current for 5.5 seconds each, for example, Soluble PQ3
% liquid to complete the surface hardening.
Thereafter, a high frequency current of 12.0 KW was supplied from the inverter to the heating coils 2' and 2 for 9.5 seconds, respectively.
Then, the surface hardness of each part (a) near the stepped portion 13 of the object to be heated 1) near the required locations 211' and 211', b) near the square vibrator 23 (see Figures 3 and 5) is shown in Table 1. As shown in the figure, there were variations in the induction heating by the heating coil 2. However, in induction heating by the heating coil 2', the surface hardness of each part of the object to be heated 1 marked with ANb and c can be approximately the same, and a uniform hardened surface layer can be obtained.

As detailed above, in the case of the method of the present invention, it is possible to perform tempering with improved quality, improve the efficiency of heat treatment work, and also temper the object to be heated in which residual heat remains immediately after quenching. In some cases, the present invention has excellent effects, such as being able to reduce the energy required for tempering by the amount of residual heat.

In the above-described embodiment, the cores 36, 36 are removed from the square vibrator 21', 21' when the object to be heated 1 is hardened, and the cores 36, 36 are removed from the square vibrator 2 when tempering the object 1.
Although the configuration is such that the cores 1' and 21' are added to the required portions 211' and 211', the configuration is not limited to this, and a configuration may also be adopted in which part of the cores 31' to 35' are removed when tempering. In this case, the shapes and dimensions of the cores 31' to 35' to be removed and the locations to be removed may be determined by some experiments.

Further, in the above-described embodiment, an air cylinder is used to drive the support portions 361, 361, but the invention is not limited to this, and it goes without saying that an appropriate device such as a solenoid may be used.

[Brief explanation of the drawing]

FIG. 1 is a partially exploded plan view schematically showing the main parts of a conventional heating coil and an object to be heated. FIG. 2 is an external view schematically showing the heating coil 2. FIG. A partially fragmented plan view schematically showing the fixed state and the main part of the heated object,
FIG. 4 is a graph of the temperature rise due to induction heating in each part of the object to be heated 1, and FIG. 5 is a graph of the heating coil 2 according to the present invention.
' and - It is a partially fragmented plan view schematically showing the main part of the object to be heated. 1...Object to be heated, 2, 2'...Heating coil, 11, 13...Stepped portion, 12
......Large diameter part, 14...R part, 21
, 23, 21', 23'...) corner vibrator, 31
, 32, 33, 34, 35, 31', 32', 33',
34', 35', 36... Heat strengthening material, 36
1...Support part.

Claims (1)

[Claims] 1 In a high-frequency heat treatment method for hardening and tempering the object to be heated by high-frequency induction heating, the same heat-strengthening material is attached in different amounts during heating for hardening and heating for tempering. An induction heat treatment method characterized by quenching and tempering an object to be heated using a heating coil.