JP2015010238A - Heat treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat treatment method, when a workpiece requiring different characteristics in different regions in one workpiece is subjected to quenching treatment and tempering treatment, its treatment can easily be performed in a short time while securing quality.SOLUTION: When the first region 11 and the second region 12 obtained by separating a workpiece W to a traverse direction are subjected to quenching treatment and tempering treatment, the first region 11 and the second region 12 are subjected to quenching treatment, and thereafter, the first region 11 and the second region 2 are made different temperatures, and tempering treatment is simultaneously performed, thus the hardness of the first region and the hardness of the second region are differentiated.

Description

  The present invention relates to a heat treatment method for quenching and tempering a workpiece in which a first region and a second region are spaced apart in the transverse direction.

  2. Description of the Related Art Conventionally, a construction machine or the like uses a large swivel wheel in which gear teeth are provided on one of the inner periphery or the outer periphery and a rolling surface such as a ball or roller of a bearing is provided on the other. In such a large turning wheel, both the gear teeth and the rolling surface are subjected to heat treatment for quenching and tempering (for example, Patent Document 1 below).

  In such a large turning wheel, the inner periphery having gear teeth is required to be heat-treated so as to improve toughness and durability. On the other hand, the outer periphery having rolling wheels is required to be heat-treated so as to ensure hardness and improve rolling characteristics. Therefore, the required characteristics are different between the inner periphery and the outer periphery.

  Thus, when quenching the swirling wheels having different heat treatment conditions, for example, the tempering process has been performed by searching for and specifying conditions that can simultaneously achieve the required characteristic range of the inner periphery and the required characteristic range of the outer periphery. For example, after quenching by induction heating and quenching each of the inner and outer circumferences, the entire workpiece is slowly heated by furnace heating, and then tempered by heating it within a predetermined narrow temperature range and allowing it to cool. It was.

  In addition, in order to quench only the inner circumference having the gear teeth of the turning wheel, for example, as in Patent Document 2 below, each tooth portion of the inner ring is induction-heated by a high-frequency current and rapidly cooled, and predetermined cooling is performed. It has been proposed to self-temper using residual heat by immediately stopping cooling when the temperature is reached.

JP 2008-231396 A JP 2007-204834 A

  However, when the inner circumference and the outer circumference of a large-sized annular workpiece are tempered by quenching after quenching by furnace heating, there is a problem that the processing time is long and the productivity is poor. If induction heating is used to temper the inner circumference and outer circumference in order after quenching, the work process requires a lot of work, and the temperature range required during tempering is narrower than that during quenching, and at a low temperature, There was also a problem that the quenching quality deteriorated due to the heat during one heating affecting the other.

  The present invention is a heat treatment method capable of easily heat-treating in a short time while ensuring the quality when heat-treating a workpiece having different characteristics required in different regions in one work by quenching and tempering. The purpose is to provide.

  In the heat treatment method of the present invention that achieves the above object, the first region and the second region are quenched when quenching and tempering the first region and the second region that are spaced apart in the transverse direction on the workpiece. After the treatment, the hardness of the first region and the hardness of the second region are made different by tempering the first region and the second region at different temperatures at the same time.

In the tempering treatment of this heat treatment method, it is preferable to heat the first region to heat the second region to a predetermined tempering temperature range. In that case, in the tempering process, it is preferable that the first region is induction-heated by the first heating coil.
Furthermore, the first region is quenched by induction heating with the first heating coil and the second region is quenched by induction heating with the second heating coil, and then the first region and the second region are quenched. It is particularly preferable that the first region and the second region are tempered by induction heating and cooling the first region with the first heating coil.

  The heat treatment method of the present invention is a heat treatment method for quenching and tempering a first region and a second region that are spaced apart from each other in the transverse direction of the workpiece, and the temperature distribution is applied to the workpiece after heating in the quenching treatment. The first region and the second region may be tempered at the same time by rapidly cooling to form, stopping the rapid cooling in a state where the high temperature portion is equal to or higher than the tempering temperature range, and dissipating heat. In that case, it is preferable to rapidly cool so as to form a temperature distribution in the transverse direction of the workpiece, and when the temperature at a predetermined position in the transverse direction reaches a predetermined temperature, the rapid cooling is stopped to dissipate heat.

  In this heat treatment method, a first region having a large number of gear teeth is provided on one of the inner periphery and the outer periphery, and a second region having a rolling surface is provided on the other. It can be suitably used for quenching and tempering a workpiece for a swivel wheel.

  According to the present invention, the first region and the second region subjected to the quenching treatment are tempered at different temperatures, so that it is possible to form the first region and the second region having different hardnesses in the same workpiece. Thus, the quality of each of the first area and the second area can be ensured. In addition, since the first region and the second region are tempered simultaneously, labor and time required for the tempering process can be reduced. Therefore, it is possible to provide a heat treatment method capable of easily performing heat treatment in a short time while ensuring quality.

(A)-(f) is a schematic sectional drawing explaining the heat processing process of 1st Embodiment of this invention. It is a graph which shows a time-dependent change of the temperature of the 2nd field in the heat treatment process of a 1st embodiment of the present invention. (A)-(e) is a schematic sectional drawing explaining the heat processing process of 2nd Embodiment of this invention. It is a graph which shows the time-dependent change of the temperature of the 1st field in the heat treatment process of a 2nd embodiment of the present invention. In each embodiment of this invention, it is a partial front view which shows the workpiece | work which heat-processes.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First Embodiment]
The workpiece W to be heat-treated in this embodiment is an annular intermediate work product made of a steel material that has been processed in advance for a large toothed swivel ring, and is formed in an annular shape as shown in FIG. The first region 11 and the second region 12 are provided apart from each other.

  In the workpiece W, the first region 11 is provided continuously on the inner periphery, and has a large number of gear teeth 13. The second region 12 is provided continuously on the outer periphery, and has a rolling surface 14 such as a ball or roller of a bearing. The large number of gear teeth 13 are extended in the axial direction over the entire thickness direction, that is, between the two end faces. The rolling surface 14 is provided in a concave shape in a part in the thickness direction.

  In the present embodiment, the whole of the gear teeth 13 from the bottom to the cutting edge is subjected to a quenching process and a tempering process, and the inner surface of the rolling surface is subjected to a quenching process and a tempering process, thereby heat-treating the workpiece W. During the heat treatment, the metal heat-treated structures formed in the inner peripheral first region 11 and the outer peripheral second region 12 may be continuous, but in this example, they are not continuous.

  As shown in FIG. 1, the heat treatment apparatus to be used is supported by a support means (not shown), and is also supported by a first heat treatment means 21 arranged on the inner periphery of the work W rotating in the circumferential direction, and a support means (not shown). And a second heat treatment means 22 disposed on the outer periphery of the work W rotating in the circumferential direction.

  The first heat treatment means 21 includes an annular first heating coil 23 that is disposed on the inner periphery of the workpiece W and can be opposed to a large number of gear teeth 13, and a first cooling nozzle that can inject coolant onto the inner periphery of the workpiece W. 25. The second heat treatment means 22 is arranged on the outer periphery of the work W, and is formed in an annular second heating coil 24 that can face the rolling surface 14, and a second cooling nozzle 26 that can inject a coolant onto the outer periphery of the work W. Have.

  In order to heat treat the workpiece W, a first region quenching process is performed as shown in FIGS. 1A and 1B, and then a second region quenching process is performed as shown in FIGS. 1C and 1D. Thereafter, a tempering step is performed as shown in FIGS. FIG. 2 shows an example of the change over time of the surface temperature in the second region 12 of the workpiece W in the second region quenching step and the tempering step.

In the first region quenching step, as shown in FIG. 1A, the first region 11 is heated by high-frequency induction by the first heating coil 23, so that the entire gear teeth 13, that is, the tooth bottom and the tooth bottom, go inward. The surface and the inside of the protruding part are heated to the quenching temperature range. The quenching temperature range is, for example, a temperature equal to or higher than the A3 transformation point.
Next, as shown in FIG. 1B, the first region 11 heated by jetting the coolant from the first cooling nozzle 25 to the first region 11 is rapidly cooled.

  In the second region quenching step, as shown in FIG. 1C and P11 in FIG. 2, the second region 12 is subjected to high-frequency induction heating with the second heating coil 24 to thereby quench the inner surface of the rolling surface 14. As shown in FIG. 1 (d), the liquid is sprayed from the second cooling nozzle 26 to the second region 12, and the heated second region 12 is rapidly cooled.

  In the tempering process, as shown in FIG. 1 (e) and P12 in FIG. 2, the first region 11 is brought to a predetermined first tempering temperature range by high-frequency induction heating the first region 11 with the first heating coil 23. In addition to heating, the rolling surface of the second region 12 is heated to a predetermined second tempering temperature range by, for example, heat transfer.

In the tempering process, the characteristics obtained according to the heating temperature change. Therefore, both the first tempering temperature range and the second tempering temperature range are temperatures below the A1 transformation point, and are appropriately set according to the required characteristics. In this embodiment, in order to keep the hardness of the rolling surface 14 in the second region 12 high and suppress the hardness of the gear teeth 13 in the first region 11 to improve toughness, for example, the first tempering temperature range is set to 250. While setting to +/- 20 degree | times, you may set a 2nd tempering temperature range 20-50 degree | times lower than a 1st tempering temperature range.
In order to achieve such a first tempering temperature range and a second tempering temperature range at the same time, for example, a method of adjusting electric conditions such as power and frequency supplied to the first heating coil 23 can be adopted. .

  Various conditions are set using, for example, FEM analysis using various parameters such as workpiece W shape, material, coil shape, arrangement, frequency, electric power, etc., heating time, heat transfer rate, heat capacity, etc. It can be set in advance by simulation using a model.

In this way, after heating the second region 12 to the second tempering temperature range, preferably after simultaneously setting the first region 11 to the first tempering temperature range, by radiating heat in the atmosphere, etc., cooling by slow cooling, The first area 11 and the second area 12 are tempered.
This completes the heat treatment.

  According to the heat treatment method as described above, the first region 11 and the second region 12 subjected to the quenching treatment are tempered at different temperatures, so that the first region 11 and the second region having the different hardness in the same workpiece W are processed. Region 12 can be formed. In addition, since the first region 11 and the second region 12 are tempered simultaneously, labor and time required for the tempering process can be reduced.

  In this embodiment, since a large number of gear teeth 13 and rolling surfaces 14 provided on the inner and outer circumferences can be tempered to a desired degree, the gear teeth 13 are sufficiently tempered and hardened. The toughness and durability can be improved by reducing the thickness, and rolling characteristics such as balls and rollers of the bearing can be improved by suppressing tempering of the rolling surface 14 and maintaining sufficient hardness.

  In the tempering process of this embodiment, since the first region 11 and the second region 12 are heated by heating the first region 11, the first region 11 is strongly heated to transfer the second region 12 to, for example, heat transfer. Can be heated weaker. At this time, since the second region 12 is heated to the second tempering temperature range, the second region 12 can be set to a predetermined hardness, and the hardness of the first region 11 can be made lower than that of the second region 12. .

  In the tempering process of this embodiment, since the first region 11 is induction-heated by the first heating coil 23, the heating temperature and temperature rise of the first region 11 can be set by appropriately setting electrical conditions such as frequency and power. Speed can be adjusted. Therefore, it is possible to heat the first region 11 to a predetermined first tempering temperature range and to heat the second region 12 to a predetermined second tempering temperature range. Each can have a desired hardness.

  In this embodiment, the first region 11 is induction-heated by the first heating coil 23 and rapidly cooled, and the second region 12 is induction-heated by the second heating coil 24 and rapidly quenched to quench the treatment. The region 11 and the second region 12 can be quenched to a desired hardness. And if the 1st area | region 11 and the 2nd area | region 12 are tempered by inductively heating and cooling the 1st area | region 11 with the 1st heating coil 23, it is not necessary to provide another installation for tempering. Accordingly, the first region 11 and the second region 12 can be subjected to quenching and tempering processes to a desired hardness, respectively, with simple equipment.

[Second Embodiment]
The second embodiment is the same as the first embodiment except that the order of the steps and the heating method are different.

  In this embodiment, in order to heat-treat the annular workpiece W shown in FIG. 5, as shown in FIGS. 3 (a) and 3 (b), a second region quenching step is performed, and then FIGS. 3 (c) and 3 (d). As shown in FIG. 3, the first region quenching step is performed, and the tempering step is performed as shown in FIG. FIG. 4 shows an example of the change over time of the surface temperature in the first region 11 of the workpiece W in the first region quenching step and the tempering step.

  In the second region quenching step, as shown in FIG. 3A, the second region 12 is heated by high frequency induction heating with the second heating coil 24 to heat the inner surface of the rolling surface 14 to a quenching temperature range, As shown in FIG. 1B, the coolant is jetted from the second cooling nozzle 26 to the second region 12 to rapidly cool the second region 12.

In the first region quenching step, as shown in FIG. 3C and P21 in FIG. 4, the first region 11 is subjected to high frequency induction heating by the first heating coil 23, so that the gear teeth 13 as a whole, that is, the tooth bottom and the teeth. The surface and the inside of the part protruding inward from the bottom are heated to a predetermined quenching temperature range.
Subsequently, as shown in FIG. 3D, the first region 11 is rapidly cooled by injecting the coolant from the first cooling nozzle 25 to the first region 11.

  In the second embodiment, when cooling after heating in the first quenching step, the workpiece W is rapidly cooled so as to form a temperature distribution in the transverse direction, that is, in the radial direction. For example, the coolant may be brought into contact with the first region 11 and the second region 12, and the temperature distribution may be formed so that the first region 11 and the second region 12 have a lower temperature than the inside. The temperature distribution is formed so that the first region 11 has a lower temperature than the second region 12 by bringing the coolant directly into contact with the first region 11.

Then, in the middle of cooling, the injection of the coolant from the first cooling nozzle is stopped and the rapid cooling is stopped, so that the workpiece W is gradually cooled and tempered as shown in P22 of FIG. 3 (e) and FIG. Apply.
When the rapid cooling is stopped, a temperature distribution is formed in the workpiece W, and thus a high-temperature portion is formed in a part of the workpiece W in the transverse direction. In this embodiment, the cooling is stopped when the temperature of the high temperature portion is at least equal to or higher than the first tempering temperature range.

  The timing for stopping the rapid cooling may be set according to, for example, the rapid cooling time, but in this embodiment, it is set based on the surface temperature at the predetermined position X in the transverse direction of the workpiece W, and the surface temperature is set to the predetermined temperature. Rapid cooling is stopped when it reaches. This position is preferably determined in advance based on the size and shape of the workpiece W. For example, it can be set by simulation or preliminary experiment.

  Thereby, the heat of the high temperature part is diffused to the low temperature side. And the temperature of the 2nd field 12 is made into the 2nd tempering temperature range, and after that, heat dissipation is continued and it cools slowly. In that case, a temperature distribution is formed at the time of rapid cooling so that the temperature of the first region 11 is in the first tempering temperature range, the second region 12 is in the second tempering temperature range, and the first region 11 is in the first tempering temperature range. The tempering temperature range is preferable. As a result, the first region 11 and the second region 12 can be tempered simultaneously with different temperatures, and the heat treatment is completed.

  According to the heat treatment method for the workpiece W as described above, the same effects as those of the first embodiment can be obtained. Further, according to the second embodiment, since the first region 11 and the second region 12 are tempered by stopping the rapid cooling during the quenching process and dissipating heat, the quenching process is performed using the heat during quenching. And tempering treatment. In particular, at the time of rapid cooling, by forming a temperature distribution on the workpiece W, the first region 11 and the second region 12 are set to different temperatures, so that the tempering process can be easily performed.

  In this embodiment, since the temperature distribution is formed in the transverse direction of the workpiece W, the residual heat can be diffused in the transverse direction after stopping the rapid cooling, and the first region 11 provided in the transverse direction is spaced apart from the first region 11. While the second region 12 is set to a different temperature, it is possible to prevent temperature variation in each region, and the tempering process can be easily performed.

In addition, the above embodiment can be suitably changed within the scope of the present invention.
For example, in the above description, the work W in which the gear teeth 13 are provided on the inner periphery and the rolling surfaces 14 are provided on the outer periphery has been described. However, the gear teeth 13 are provided on the outer periphery, and the rolling surfaces 14 are provided on the inner periphery. Even for the workpiece W, the inner and outer circumferences may be reversed.
Although the workpiece | work W which has the gear tooth 13 in the 1st area | region 11 and has the rolling surface 14 in the 2nd area | region 12 was demonstrated, it is not limited at all. Here, the work W having a structure in which different characteristics are required in the first region 11 and the second region 12 can be similarly applied.
Furthermore, in the above description, the example in which the first region 11 and the second region 12 are provided on the inner periphery and the outer periphery has been described. However, the first region 11 and the second region are provided on one end surface and the other end surface of the annular workpiece W. 12 may be provided. The same applies not only to the annular workpiece W but also to workpieces W of other shapes.
In the above, in order to quench the first region 11 by heating and quenching the second region 12 by heating and quenching, in the first embodiment, after first heating and quenching the first region 11 first, Two regions 12 were heated and quenched. On the other hand, in the second embodiment, the first region 11 is heated and quenched after the second region 12 is first heated and quenched. However, the order of the quenching process in the first region 11 and the second region 12 is arbitrary and may be reversed. Furthermore, it is also possible to quench the first region 11 and the second region 12 at the same time by heating the first region 11 and the second region 12 simultaneously or by rapidly cooling them.

W Work 11 First region 12 Second region 13 Gear teeth 14 Rolling surface 21 First heat treatment means 22 Second heat treatment means 23 First heating coil 24 Second heating coil 25 First cooling nozzle 26 Second cooling nozzle

Claims (7)

A heat treatment method for quenching and tempering a first region and a second region that are spaced apart in a transverse direction on a workpiece,
After quenching the first region and the second region, the first region and the second region are simultaneously tempered at different temperatures, whereby the hardness of the first region and the hardness of the second region Is a heat treatment method.   The heat treatment method according to claim 1, wherein, in the tempering process, the second region is heated to a predetermined tempering temperature range by heating the first region.   The heat treatment method according to claim 2, wherein in the tempering process, the first region is induction-heated by a first heating coil.   The first region is quenched by induction heating with the first heating coil, and the second region is induction heated by the second heating coil and quenched to quench the first region and the second region. Then, the first region and the second region are tempered by induction heating and cooling the first region with the first heating coil. A heat treatment method for quenching and tempering a first region and a second region that are spaced apart in a transverse direction on a workpiece,
After heating in the quenching process, the workpiece is quenched so as to form a temperature distribution, and the first region and the second region are dissipated by stopping the rapid cooling in a state where the high temperature portion is equal to or higher than the tempering temperature range. A heat treatment method in which different temperatures are tempered at the same time.   The heat treatment method according to claim 5, wherein rapid cooling is performed so as to form a temperature distribution in the transverse direction of the workpiece, and the rapid cooling is stopped when the temperature at a predetermined position in the transverse direction reaches a predetermined temperature to dissipate heat.   For the toothed swivel wheel formed in an annular shape and provided with the first region having a large number of gear teeth on one of the inner periphery and the outer periphery and the second region having a rolling surface on the other. The heat treatment method according to claim 1, wherein the workpiece is quenched and tempered.

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