JP6438734B2 - Work heating and quenching methods - Google Patents

Description

  The present invention prepares a workpiece in which the first shape portion and the second shape portion are axially continuous via a stepped portion and an annular heating coil, and at least one of the workpiece and the heating coil in the workpiece longitudinal direction. The present invention relates to a method for heating a workpiece that is induction-heated while being translated, and a quenching method.

  In order to induction-harden the surface of a workpiece such as a solid or hollow round bar in which the large-diameter portion and the small-diameter portion are adjacent in the axial direction, or a long member in which the concave portion and the convex portion are adjacent in the axial direction, High-frequency moving quenching is performed in which a heating coil is moved along the longitudinal direction of a workpiece and heated.

  In high-frequency moving quenching, the heating coil is placed close to and opposed to the surface of the large diameter portion or the convex portion, and the step portion between the large diameter portion and the small diameter portion or the step portion between the convex portion and the concave portion is passed through. It is moved to the concave portion, or conversely, the step portion is passed from the small diameter portion or the concave portion to the large diameter portion or the convex portion, and heated sequentially. At that time, after passing through the stepped portion, the coil gap between the heating coil and the surface of the small-diameter portion or the concave portion facing the heating coil is the gap between the heating coil and the edge portion of the large-diameter portion or the edge portion of the convex portion. A region that is larger than the distance between them occurs according to the size of the stepped portion.

  For this reason, there is a problem that the coil gap is large on the surface of the small-diameter portion or the recess surface in the region near the stepped portion, so that heat generation is insufficient and the temperature necessary for quenching is not reached. On the other hand, at the edge part of the large diameter part and the edge part of the convex part, since the coil gap is small, the heating coil continues to generate heat even after passing through, causing overheating and causing the occurrence of cracking. There is.

  Even when the stepped portion is small, by controlling the heating coil moving speed and power supply output of power, quenching can be performed continuously on the workpiece surface, but very complicated moving speed control and power control are possible. Is indispensable, and moreover, it is necessary to perform a condition setting operation in which the quenching test is actually performed a plurality of times.

  For example, as shown in Patent Document 1 below, it is conceivable to use a low frequency during heating in order to sufficiently generate heat in the recess near the stepped portion and prevent melting of the tip portion. However, when heating the large-diameter portion or the convex portion, the depth of heat generation becomes very deep, causing problems such as insufficient surface heating temperature and a deeper hardened layer with heat treatment specifications, resulting in greater deformation.

Japanese Patent No. 4926728

  According to the present invention, it is easy to heat a workpiece in which the surface of the workpiece in which the first shape portion and the second shape portion having a small cross-sectional shape are continuous in the axial direction via the stepped portion is continuously heated to a predetermined temperature range. The object is to provide a method and a quenching method.

In the heating method for a workpiece of the present invention that achieves the above object, the first shape portion and the second shape portion having a smaller cross-sectional shape than the first shape portion are provided with a step edge portion at the boundary portion on the first shape portion side. A workpiece that is continuous in the axial direction through a stepped portion and an annular heating coil are prepared, and while supplying power to the heating coil, at least one of the workpiece and the heating coil is parallel to the longitudinal direction of the workpiece. A method of heating a work by induction heating each surface of a first shape portion, a second shape portion, and a stepped portion by moving the first shape portion and the second shape by electric power combining high frequency and low frequency One of the parts is heated, the ratio of the low frequency of power is increased to heat the stepped part, and the ratio of the low frequency of power is decreased to heat the other of the first shape part and the second shape part It is a method to do.

  The workpiece quenching method of the present invention that achieves the above object is to heat the workpiece sequentially from one end side to the other end side by the workpiece heat treatment method as described above, and inject cooling liquid from a cooling jacket that moves with the heating coil. Thus, the workpiece is quenched and quenched in sequence.

According to the workpiece heating method of the present invention, the surface of the workpiece in which the first shape portion and the second shape portion having a small cross-sectional shape are continuous in the axial direction via the stepped portion is continuously heated to a predetermined temperature range. Easy to do.
Further, according to the work quenching method of the present invention, the first shape portion and the second shape portion having a small cross-sectional shape are continuously provided at a predetermined depth on the surface of the work which is continuous in the axial direction through the step portion. It is easy to quench the range.

It is a schematic sectional drawing which shows the workpiece | work heated and quenched by the heating and quenching method in embodiment of this invention. (A) shows the correlation of the current density with respect to the depth from the surface when the high frequency: low frequency is 100: 0 in the power supply unit in the embodiment of the present invention, and (b) shows the high frequency: low frequency is 0. : Shows the correlation of the current density with respect to the depth from the surface when 100 is set, and (c) shows the depth with respect to the depth from the surface when the high frequency: low frequency is set to 50:50 by synthesizing the high frequency and the low frequency. The correlation of current density is shown, and (d) is a graph showing the correlation of current density with respect to the depth from the surface at a single frequency. (A)-(e) is sectional drawing explaining the process of the heating and quenching method in embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[work]
As shown in FIG. 1, the workpiece 10 to be heated and quenched in this embodiment includes a first shape portion 11 on both ends, and a second shape portion 12 having a smaller cross-sectional shape than the first shape portion 11. , Having a shaft. In the workpiece 10, the first shape portion 11 and the second shape portion 12 are provided continuously in the axial direction via the step portion 13.
The cross-sectional shape of the outer surface orthogonal to the axis in each of the first shape portion 11 and the second shape portion 12 has a circular shape. For example, the radius of the first shape portion 11 is 10 mm or more than the radius of the second shape portion 12. It is getting bigger.

  The step portion 13 is a portion where the cross-sectional shape orthogonal to the axis changes suddenly, and may be an orthogonal surface orthogonal to the axis, but here is a curved surface including a surface inclined in the axial direction. At the boundary portion between the stepped portion 13 and the first shape portion 11, an angular stepped edge portion 13 a is formed so that a corner is formed in the cross-sectional shape of the outer surface along the axial direction. Further, a curved surface is formed between the step portion 13 and the second shape portion 12.

[Heating device]
An apparatus for continuously heating and quenching the outer surface of the work 10 along the axial direction, which is the longitudinal direction, is an annular heating that surrounds the first shape portion 11 of the work 10 and is mounted as shown in FIG. A coil 110, a power supply unit 100 that supplies power to the heating coil 110, a cooling jacket 90 that is arranged behind the heating coil 110 and moves integrally with the heating coil 110, and the heating coil 110 and the cooling jacket And a driving device 80 that moves the head 90 in one direction along the axis while adjusting the moving speed.

  The power supply unit 100 is configured to be able to supply the heating coil 110 as electric power by combining high frequency and low frequency while adjusting the ratio. The power supply unit 100 includes a low-frequency output device that supplies, for example, power having a frequency of 50 Hz to less than 50 kHz to the heating coil 110, and a high-frequency power that is higher than the frequency of the low-frequency output device, for example, 1 kHz to 400 kHz. A high-frequency output device to be supplied to 110.

  Here, the magnitude of the AC power supplied from the high frequency output device and the low frequency output device to the heating coil 110 can be adjusted, and the heating coil can be adjusted by adjusting the output ratio between the high frequency output device and the low frequency output device. 110 can be supplied.

In the power supply unit 100 of this embodiment, a pseudo frequency can be adjusted by arbitrarily setting an output power ratio (DT) between a low frequency and a high frequency, and can be output at an arbitrary timing. When the pseudo frequency is adjusted, the current penetration depth can be adjusted.
For example, when the power supply unit 100 supplies the heating coil 110 with a high frequency: low frequency ratio of 100: 0, the correlation of the current density with respect to the depth from the workpiece surface is as shown in FIG. Then, FIG. 2B is obtained. When the output power ratio (DT) is adjusted and the high frequency and the low frequency are combined at 50:50 and supplied to the heating coil 110, the correlation L1 at the low frequency and the high frequency are shown in FIG. Correlation obtained by combining the correlation L2 in FIG. As shown in FIG. 2 (d), this correlation L3 is equivalent to a correlation at a single frequency between a high frequency and a low frequency, and can be treated as pseudo single frequency power.
Therefore, by applying such a power supply unit 100 to high-frequency moving quenching, moving heating can be performed while supplying a pseudo frequency suitable for the shape of each heating portion of the workpiece 10 to the heating coil 110. It becomes.

[Heating and quenching method]
A method for continuously heating and quenching the outer surface of the workpiece 10 along the axial direction using such an apparatus will be described.
In this apparatus, as shown in FIG. 3A, first, the workpiece 10 is supported in a substantially vertical direction so as to be rotationally driven, and the heating coil 110 is disposed oppositely around the outer periphery of the workpiece 10 with a predetermined gap. A cooling jacket 90 is disposed and mounted in the vicinity below 110.

  In this state, as shown in FIG. 3A, the annular heating coil 110 is disposed to face the starting position on the end side in the heating region of the first shape portion 11. The power supply unit 100 moves the heating coil 110 upward in one direction along the axis from the start position while supplying the heating coil 110 with electric power obtained by combining high frequency and low frequency with a predetermined DT ratio. Thereby, the surface of the 1st shape part 11 is induction-heated one by one. Further, the cooling jacket 90 is made to follow the movement of the heating coil 11, and immediately after the heating, the quenching treatment is sequentially performed by quenching with the coolant from the cooling jacket 90.

As shown in FIG. 3B, the heating coil 110 reaches the step portion 13. Thereafter, the low frequency ratio of the power supplied to the heating coil 110 by the power supply unit 100 is increased. As a result, the stepped portion 13 is induction-heated and cooling by the cooling jacket 90 is continued.
In the step portion 13, it is preferable to increase the ratio of the low frequency most. In that case, for example, electric power consisting only of a low frequency can be supplied to the heating coil 110. In this embodiment, since the step edge portion 13a is provided at the boundary between the first shape portion 11 and the step portion 13, the ratio of the low frequency is most increased in the vicinity of this portion.

  Further, in this embodiment, since the stepped portion 13 on the second shape portion 12 side from the stepped edge portion 13a has a surface inclined with respect to the axial direction, high frequency and It is preferable to move the heating coil 110 while gradually changing the ratio to the low frequency. Thereby, the distribution in the thickness direction of the heat treatment structure on the surface in the vicinity of the stepped portion 13 can be made smooth.

  After the heating coil 110 passes through the step portion 13 and faces the second shape portion 12, the power supply unit 100 reduces the low frequency ratio of the power again. And as shown in FIG.3 (c), by supplying this electric power to the heating coil 110 and moving, the 2nd shape part 12 is induction-heated, and also cooling by the cooling jacket 90 is continued, and a 2nd shape part is continued. 12 is sequentially quenched. The ratio between the high frequency and low frequency of the power when heating the second shape portion 12 and the ratio between the high frequency and low frequency of the power when heating the first shape portion 11 can be arbitrarily set. Depending on the conditions, these ratios may be the same.

Thereafter, as shown in FIG. 3D, the heating coil 110 reaches the step 13 on the opposite side. Therefore, the low frequency ratio of the power supplied to the heating coil 110 by the power supply unit 100 is increased again. As a result, the stepped portion 13 is induction-heated and cooling by the cooling jacket 90 is continued.
In this step portion 13, similarly to the step portion 13 described above, in the shape change portion or step edge portion 13 a where the inclination with respect to the axis is steep, it is preferable to increase the ratio of the low frequency most, and the electric power consisting only of the low frequency is increased. It can also be supplied to the heating coil 110. Further, since the step portion 13 has a surface inclined with respect to the axial direction, the heating coil 110 may be moved while gradually changing the ratio between the high frequency and the low frequency.

  After the heating coil 110 passes through the step portion 13 and faces the first shape portion 11 on the other side, the power supply unit 100 again reduces the low frequency ratio of the power. And as shown in FIG.3 (e), by supplying this electric power to the heating coil 110 and moving, the 1st shape part 11 is induction-heated to the end position, and also cooling by the cooling jacket 90 is made to the end position. Continuously quenching the first shape portion 11 sequentially. The ratio between the high frequency and the low frequency of the power at this time can be arbitrarily set according to the condition between the high frequency and the low frequency of the power when heating the first shape portion 11 and the second shape portion 12 described above. Yes, depending on conditions.

  In such a series of heating periods, power is constantly supplied to the heating coil 110 from the start position of the first shape portion 11 on one side to the end position of the first shape portion 11 on the other side through the second shape portion 12. The heating coil 110 may be moved continuously. Preferably, while moving the heating coil 110 at a constant speed from the start position to the end position, that is, while moving the heating coil 110 within a predetermined speed range, the pseudo frequency is set as described above, Heating is performed by supplying electric power after adjusting the current value to be suitable for each part.

  As described above, according to the method of heating and quenching the workpiece 10, the first shape portion 11 is heated by the electric power obtained by combining the high frequency and the low frequency, and the ratio of the low frequency of the electric power is increased. The part 13 is heated, and then the second shape part 12 is heated again by reducing the low frequency ratio of the power. Therefore, the pseudo frequency of power supplied when heating the stepped portion 13 can be made lower than the pseudo frequency of power supplied when heating the first and second shape portions 11 and 12.

As a result, the step portion 13 can be heated by increasing the eddy current density at a position deeper than the surface compared to the first shape portion and the second shape portions 11 and 12, and the step portion 13 has a sudden shape change portion. Even if it exists, it is possible to heat a deeper and wider range.
Therefore, when heating the vicinity of the stepped portion 13, eddy currents concentrate on the stepped edge portion 13 a of the first shape portion 11, the stepped edge portion 13 a is overheated, or the surface of the second shape portion 12 near the stepped portion 13. Insufficient heating can be prevented.

  Further, by appropriately changing the ratio between the high frequency and the low frequency while moving the heating coil 110, the first shape portion 11 and the second shape portion 12 having different cross-sectional shapes are connected via the step portion 13. However, it is easy to heat the surface continuously within a predetermined temperature range, preferably substantially uniformly. For this reason, unlike the conventional single-frequency heating, complicated control such as finely changing the moving speed or finely adjusting the power output according to the part shape and position is unnecessary.

  Further, the cooling jacket 90 is moved following the heating coil 110, and quenching is performed by heating and quenching sequentially, so that the first shape portion 11 and the second shape portion 12 having different cross-sectional shapes are stepped portions. It is easy to quench the surface of the workpiece 10 that is continuous in the axial direction via the steel sheet 13 so as to be continuously within a predetermined depth range, preferably a substantially uniform hardened layer depth.

  As described above, according to the method of heating and quenching the workpiece 10, the ratio between the high frequency and the low frequency in the power when heating the first shape portion 11 and the second shape portion 12 is arbitrary depending on the condition. If the heating coil 110 is continuously moved at a constant speed and the entire surface is heated, the surface of the workpiece 10 with the stepped portion can be continuously heated more easily.

In addition, the said embodiment can be suitably changed within the scope of the present invention. For example, although the example which has the 1st shape part 11 in the both ends and the 2nd shape part 12 in the longitudinal direction center side was illustrated above, the shape of a workpiece | work is not limited.
For example, it may be a left-right asymmetric shape, and may have one or more other shape portions in addition to the first shape portion 11 and the second shape portion 12. In that case, a step part may be provided in part or all between the shape parts adjacent to each other.

In addition, each shape portion may have a shape in which a non-circular cross-sectional shape is continuous in the axial direction, and is not limited to a solid shape but may be hollow.
Furthermore, even if a convex part or a recessed part is provided in the 1st or 2nd shape part, and these convex parts and a recessed part are arrange | positioned adjacent to another shape part and an axial direction through a level | step difference part. Similarly, the present invention can be applied. In that case, it is also possible to heat the convex part or the concave part by moving and heating at a high frequency and increasing the low frequency ratio in the vicinity of the step part that changes from the convex part to the concave part.

  Moreover, although the said embodiment demonstrated the example which heats the 2nd shape part 12 after heating the 1st shape part 11, the heating coil 110 moves in parallel with the longitudinal direction of the workpiece | work 10 with respect to the workpiece | work 10. If the heating can be performed, the first shape portion 11 can be heated after the second shape portion 12 is heated.

  Furthermore, although the said embodiment demonstrated the example which supplies the electric power combined by the overlap system (OLP) which superimposes and outputs a low frequency and a high frequency on a time axis as the electric power supply part 100 to the heating coil 110, It is not limited. For example, the work 10 may be induction-heated using a power supply unit that supplies power synthesized by a hot switching method (HSW) that alternately outputs a low frequency and a high frequency on the time axis. Of course it is possible.

Although the example which moved the heating coil 110 along the longitudinal direction, ie, an axial direction was demonstrated above, the workpiece | work 10 can also be moved. In addition, the present invention can be applied even if the relative moving speed of the heating coil 110 is appropriately changed in each of the shape portions 11 and 12 and the step portion 13. For example, the stepped portion 13 can be heated more reliably by slowing or stopping the relative movement speed of the heating coil 110 in the vicinity of the stepped portion 13.
Further, in the above description, the workpiece 10 is arranged in the vertical direction and the heating and quenching process is performed.

DESCRIPTION OF SYMBOLS 10 Work 11 1st shape part 12 2nd shape part 13 Step part 13a Step edge part 90 Cooling jacket 100 Electric power supply part 110 Heating coil 130 High frequency output device 140 Low frequency output device 150 Control means

Claims (4)

A workpiece in which the first shape portion and the second shape portion having a smaller cross-sectional shape than the first shape portion are axially continuous via a step portion having a step edge portion at a boundary portion on the first shape portion side ; An annular heating coil, and while supplying power to the heating coil, moving at least one of the workpiece and the heating coil in parallel with the longitudinal direction of the workpiece, the first shape portion and A work heating method for induction heating each surface of the second shape part and the step part,
One of the first shape part and the second shape part is heated by the electric power obtained by combining high frequency and low frequency, the ratio of the low frequency of the electric power is increased to heat the stepped part, and the electric power A method for heating a workpiece, wherein the other of the first shape portion and the second shape portion is heated by decreasing a low frequency ratio.   The method for heating a workpiece according to claim 1, wherein each surface of the first shape portion, the second shape portion, and the step portion is heated while continuously moving the heating coil at a constant speed.   The method of heating a workpiece according to claim 1 or 2, wherein the stepped portion formed of a surface inclined in the axial direction is heated by gradually changing a ratio between a high frequency and a low frequency while moving the heating coil.   A workpiece quenching method in which the workpiece is heated by the workpiece heating method according to any one of claims 1 to 3 and a coolant is sprayed from a cooling jacket that moves together with the heating coil to rapidly quench the workpiece. .

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