JPS58167719A - High-frequency quenching method - Google Patents

Abstract

PURPOSE:To perform highly-accurate high-frequency quenching with a relatively simplified installation, when the outer surface of a work is high-frequency induction heated by a heating coil and then rapidly cooled by the supply of a coolant, by managing the heating and the cooling on the basis of the expansion of the work. CONSTITUTION:The relationship between the heating temp. and expansion of a round steel work W, e.g. S 40C, is shown in the drawing. The outer surface W1 of the work W is induction-heated up to a high temp. D above the completion of the point C by applying a high-frequency electric current to a heating coil 20 surrounding the work W, and then the heating is stopped when the work W reaches the predetermined value of expansion. Thereafter, the work W is rapidly cooled until it passes through a temp. G where its contraction becomes the largest by supplying a coolant from a jacket 30 for spraying a coolant. On this occasion, the preset expansion of the work W from its end part w1 at a restricted side along its axis toward its opposite end part w2 at a free side is detected by a precise length-measuring means 10 provided at the axially end part of the work W, and said heating is finished. On the other hand, the cooling is stopped by detecting the contraction to preset length in the same way. The quenching is performed in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is characterized by stopping the induction heating of the outer peripheral surface of the workpiece by applying a high-frequency current to a heating coil, and rapidly heating the outer peripheral surface of the workpiece by supplying refrigerant from a refrigerant injection jacket to the outer peripheral surface of the workpiece. When cooling is stopped, a predetermined elongation is performed using a stacking length measuring device, respectively.
This paper relates to an induction hardening method controlled by detection of shrinkage.

Until now, in the work of induction heating the workpiece by passing a high-frequency current through a heating filter that surrounds the workpiece, and then supplying a refrigerant to the outer peripheral surface of the heated object to rapidly cool it and perform induction hardening, the heating conditions were The cooling conditions have been controlled by the amount of high-frequency electric power and the heating time H, the injection amount of refrigerant at a predetermined temperature (J/s 6g), and the injection cooling time. In other words, the stoppage of heating and cooling is regulated by a set timer. (For power supply voltage fluctuations, an automatic voltage regulator is used) and for refrigerant temperature settings, a constant temperature maintenance device is used to maintain uniform heating and cooling conditions, improve repeatability, and reduce variations in heat treatment quality. Efforts have been made to minimize this. However, this conventional method requires high precision IL&V and automatic voltage adjustment equipment, which results in high costs, and indirect quenching management that does not directly grasp information on the state of heating and cooling of the workpiece to be quenched.
The current situation is that high-quality electric fields require a great deal of effort and man-hours despite the use of expensive equipment, which is affected by disturbance factors such as variations in the accuracy of component equipment and back-up in the installation accuracy of coils. .

In view of the above-mentioned points, the present invention was developed with the intention of performing induction hardening work on pipe passing from a standpoint different from the conventional work management based on heating power and heating time. The elongation of the steel member to be quenched, which can be most closely related to the quenching quality of hardened layer #1 stones, etc., is captured by the Keikoku Rancho device, and the final quenching of the steel is carried out during heating and cooling. The purpose of this invention is to provide a high-precision frequency hardening method using a relatively simple device with a configuration that allows for a more direct grasp of quality.

An embodiment of the present invention will be described below based on the drawings.

Figure 1 is an explanatory diagram showing one embodiment of the present invention, and Figure 2 is a chart showing the relationship between temperature change and elongation of medium carbon steel (for example, 840C).

To explain the raw salt of the method of the present invention using the examples shown in Fig. 1 and Fig. 2, in the workpiece (8) of 840C (annealed trench II) round steel as the member to be quenched, As the heating temperature increases, the elongation changes in the form of a buried line as shown in FIG. At position (8), contraction occurs due to Ac1 transformation, and then, as Ad transformation progresses within a certain temperature range, there is a slight contraction, and the 0 point (b) indicates simple thermal expansion. In general heat treatment, the heating temperature for rounding during quenching is a temperature point (C) that is 80 to 6 G' higher than the point where Ad transformation is completed (C).
1) is considered the standard, but since high-frequency heating is rapid heating, it is expected that the temperature will shift to even higher temperatures.

It is well known that the heating temperature for induction hardening is actually determined by various factors such as the steel type, preheat treatment condition, heating rate, quality specifications of the hardened product, etc., but in actual work, this heating temperature In general, the final quality and related properties of the quenched product are determined by various combinations of heating power and heating time, not by temperature measurement. The present invention examines the elongation of the product to be hardened in the heated state, which is directly related to the final quality, especially the surface hardness, hardened layer thickness, etc.
ob), and when the preset value is reached, the heating is stopped and the heated surface (rIi<Wh) is rapidly cooled, and cooling is performed exactly as shown by the broken line in Figure 2 to reach the maximum shrinkage point. (G) and then cooled to the complete cooling range where martensite is generated (C), or slowly cooled after passing through the maximum contraction point (G) to slow martensitic formation and minimize dimensional changes as much as possible. There is a device that performs cooling to suppress the temperature.

Regarding the steel materials used for induction hardening, including 840C in this example, the average linear expansion coefficient between θ℃ and heating temperature 700'C is approximately 18~l 6 Very narrow, and if we exclude the contraction at the time of change, C
The m coefficient of linear expansion in the region (a) is the *g coefficient of 21 in the region (b) where the temperature is higher than the point. Therefore, the coefficient of linear expansion above point C can be estimated to be 16×10−·7° C. or higher.

Currently commercially available precision length measurement 1) (10b) reading and 9 accuracy (1
-) To explain the results of the examination as to whether the method of the present invention is practicable at K, the temperature rise above point C
Extension of the length of the heated area 'gIts with respect to 'C' Δ1MI
It is expressed by the linear equation.

Δj2jxxsaxto''''6 cod-1,6jx/100 x 10 m Reading and accuracy of the length measuring device... Since it is l-, it is 1.6 gx/10
0 = 1, that is, #x*@1$, the change in length corresponding to the synergistic change in temperature and length with the minimum unit of 6 can be measured.

The control range of the heating temperature in the heat treatment 11 is ±6° C. even when it is particularly strict, and in the case of frequency hardening, a suitable range is about ±16° C. since rapid heating is particularly required. Therefore xm80
If it is ℃, it becomes l # 12.2■.

This indicates that when performing induction hardening of the 840C round steel of this example, a hardened feldspar of approximately 2.2 mm is sufficient. The minimum quenching radiation currently available is 585w.
Ruru once. Induction hardening is surface hardening and the temperature from To-4 to the core is not heated to the same temperature, so the III expansion indicated by the temperature rise on the surface is stoichiometrically different from the expansion in the relatively low temperature part of the main part. (Although it would be a national challenge to analyze it mathematically, each part of the core of the round steel of the workpiece is in a state of elongation corresponding to its temperature. In other words, as shown in Figure 2 above) When the state of change shown in the temperature-elongation curve as shown approaches the final heating stage, the elongation of each region from the outer peripheral surface qυ region (b) to the core region (a) influences each other, and the overall Appears as elongation.2O including this example
N80-1 has a total length of 200 to SOO■ feldspar! According to the experimental results when the outer periphery of the workpiece @cwo was rapidly heated by 1 & 9 waves, the following equation was established as the relation between the surface heating temperature and the elongation in the axial direction.

Elongation m - Surface heating temperature (qx Feldspar in the heated area of heating spinning -
× Average coefficient of linear expansion in that temperature range
If the thickness/diameter ratio of the heating layer becomes even smaller, the value of K is expected to become smaller than above, but it is up to the person who selects the appropriate value of K to change the heating temperature. This means that the elongation Fi can be estimated. It is thought that even if the surface is rapidly heated at the quenching heating temperature of normal steel, the value of J)K will not fall below 0.6 due to the relatively large heat conduction wheel. Now, if we assume X-O,S, then the minimum unit of the measurable synergistic value of temperature and length is; L, S lx (0,6)/100-1, l! x=1
88, xm at 80°C becomes 4.4-.

Even if the outer circumferential surface is very narrow, the mast's 11-unit length measuring device can be used. As described above, judging from the basic experimental results of the present invention, Takamei's method can heat the entire length of a long round steel by applying a load on a narrow part. is applicable.

The induction hardening method according to this embodiment is based on a construction that controls the outer periphery ffi (Wl) of the workpiece (8), which is an axially symmetrical rotating body made of 540C round steel that rotates by one rotation drive from a drive source such as a motor. A frequency current is applied to the loop heating coil ■ from the input terminal (2) to generate an induced current at the wrinkle outer circumference ll1 (Wl), and after induction heating to a high temperature (b) above the end of point C, a predetermined elongation value is achieved. When the temperature reaches the temperature (6), the heating is cut off and the refrigerant is injected from the refrigerant injection jacket (to) to rapidly cool the workpiece until it passes at least the temperature (6) at which the contraction is maximum. ) is applied to the rotary drive side (Wl
))] The other free end side (! The war fishing that thermally expands toward the illusion)
(d)
The supply of high-frequency current is interrupted and terminated via the controller (10c) by being biased toward the workpiece (8) and detected through the nine-finger support shaft, and then the heated outer periphery 1i(
(10b) starts cooling the refrigerant, and the supply of the refrigerant is started by detecting the contraction up to -1 at the preset rotation axis by the cough column length machine (10b). ) It is possible to perform induction hardening by stopping the process. These optimum elongation and thinning values are calculated and determined empirically at the trial stage.

L Experimental Example] It is certain that there is a certain relationship between elongation and quenching quality.

The entire length of 840C normalized material (diameter 2511 x length 8001) was surface hardened using lolGig, a 250 m high frequency oscillator, and the cooling was performed under the same conditions for 1 uet of complete cooling, and the input was 0.411 H/- once. is energized as shown in the table below.

The induction hardening apparatus of the embodiment used in this method, as shown in Fig. In this process, centering is carried out by supporting on a pair of rollers. ＆：'il■
is suitable for mass production, and is set so as to surround the upper half of the workpiece P over the entire length of the workpiece (2) using an appropriate lifting device. High frequency power generator without automatic voltage regulator (100)
The heating coil receives a high frequency current from the input terminal (2) and heats the outer periphery of the rotating workpiece (rli #t) by induction. The elongation due to induction heating is measured by a measurement sensor made of super metal (lea ) (for example, N1kon's Digimicro MU-
601 etc.). Precision length measurement 11
When the (job) detects the elongation of the rotating wheel of a predetermined workpiece (support), it sends the KM signal to the controller (loc), and the high frequency current is turned on and off according to the command from the controller (10c).

At the same time, the cough suppressant works (10c) and, in response to the command from the operator, the cooling liquid is sprayed onto the heated outer peripheral surface (Wl) of the jacket member. In the case of the coolant temperature tube 1lFi of the present invention, the number of management steps can be significantly reduced compared to the conventional method. The shrinkage of the workpiece (b) due to this rapid cooling is similarly caused by the measurement sensor (10
When the needle side is detected by the length measuring device (Iυ) through the length measuring device (Iυ) and the contraction up to the set axis length is detected, the detection signal is sent to the controller (1
0c) is received and in response to the command, the electric valve of the cooling system that leads to the cooling liquid injection jacket is closed and the injection of the cooling liquid is stopped. Furthermore, as an applied example, the length measuring device [phase] of the present invention is equipped with a digital When coupled with a readout system, the expansion and contraction processes can be visualized and heat treatment applications such as tying selection to switch from rapid cooling to gradual cooling are possible.

In this way, the part to be quenched is elongated directly from the workpiece.
According to the method of the present invention, which detects the state of contraction using a precision side length measuring device, rust can be detected from various factors such as fluctuations in power supply voltage, accuracy of the heating timer, and misalignment of the relative position between the workpiece and the coil. There is no non-uniformity in the heating generated and non-uniform cooling due to variations in the temperature and flow rate of the cooling liquid, etc.
In other words, further improvement in quenching quality is expected.Furthermore, if a digital read-out system is connected to the length measuring device (10b), the progress of heat treatment can be observed during heating or cooling, allowing for optimal heat treatment. It is possible to enjoy excellent effects such as being able to apply

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention! The light diagram and the iris diagram 2 are charts showing the relationship between temperature change and elongation of carbon steel materials. (Explanation of symbols) 10... Precision length measuring device, 20... Heating coil, 80
... Refrigerant injection jacket, W... Work, Wl ・
... Workpiece outer circumferential surface, Wl, Wl... End of workpiece. −1 above

Claims (1)

[Claims] (1) A high-frequency current is applied to the heating coil (■) that emulates the outer circumference of the workpiece (material) to induce induction heating of the outer circumferential surface of the axilla, and after death, the refrigerant is supplied from the refrigerant injection jacket to rapidly cool the workpiece. In the induction hardening method for hardening, induction heating of the outer peripheral surface (Wl) of the workpiece by the application of the high-frequency current is performed using a precision length measuring device ( ) Centered and nine armpit work (8)
The elongation is terminated by detecting the elongation at the preset free end in the axial direction, and then cooling of the heated outer circumferential surface (1) is started, and the supply of the refrigerant in the round direction of the cooling is stopped at the precise Length measurement device - length υ of workpiece set in advance
9 Frequency quenching method □) The elongation of the workpiece ■ in the preset axial direction is controlled by one end 1a (wl) of the workpiece (material). A patent claim in which the shaft is restrained in one direction, and the other end (W) is set as a free end, and p is detected at the free end (-) by a precision length measuring device (2).
The induction hardening method described in Section E1.