JP2006291248A - Method and equipment for high frequency induction heat treatment, thin member and thrust bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and equipment for high frequency induction heat treatment which achieve restraining of deformation of a material to be treated and achieve severe temperature control, and a thin member having restrained deformation and stabilized quality and to inexpensively provide a thrust bearing having long life and stable quality. <P>SOLUTION: The method for high frequency induction heat-treatment is provided with a temperature control process for hardening, a hardening timing control process, and a hardening cooling process. The temperature control process for hardening includes a heating process for hardening, a temperature measuring process for controlling the hardening temperature and a temperature adjusting process for hardening. The hardening timing control process includes a temperature measuring process for controlling hardening timing and a hardening timing adjusting process. In the hardening cooling process, the cooling is performed while restricting the material to be treated by using a die. The cooling is performed by using the die as the cooling member for removing the heat from the material to be treated to thereby cool the material to be treated from a temperature of ≥A<SB>c1</SB>point to a temperature ≤M<SB>s</SB>point. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a high-frequency heat treatment method, a high-frequency heat treatment facility, a thin member, and a thrust bearing, and more specifically, a high-frequency heat treatment method including a quench hardening process, a high-frequency heat treatment facility used in the high-frequency heat treatment method, and a high-frequency heat treatment method thereof The present invention relates to a thin-walled member manufactured by using and a thrust bearing provided with the thin-walled member.

  Products such as automobiles that use bearings are becoming more sophisticated and functional. Under such circumstances, the bearings are also required to have higher performance, for example, longer life. Further, from the viewpoint of improving price competitiveness, bearings are also required to be reduced in price.

  On the other hand, thin bearing members for bearings used in bearings are likely to be deformed during quenching in the manufacturing process. When the deformation of the race member is large, the life of the bearing provided with the race member is reduced.

  In general, a thin bearing race which is a thin race member for a bearing employs, as a material, SPCC (defined in JIS G3141), SCM415 (defined in JIS G4053), etc., which are low carbon steel. And after these raw materials are shape | molded in a required shape, it hardens by hardening after performing a short-time carburizing process, and the hardness required as a bearing ring is ensured. Further, high carbon steel such as SUJ2 (specified in JIS G4805), SAE1070, etc. may be adopted as a material. In this case, after these materials are formed into a required shape, they are quenched and hardened by being heated in an atmospheric furnace and then quenched to ensure the necessary hardness for the race. Cooling in the quench hardening is generally oil quenching in which a bearing ring, which is an object to be processed, is immersed in quenching oil for cooling, or blast quenching in which wind is blown to the bearing ring to cool. However, the thin bearing ring having a small thickness is likely to be deformed during quenching by the conventional quench hardening method described above.

On the other hand, as a method for suppressing deformation of the steel material when quenching the steel material, a method of setting the scale thickness of the steel plate surface when press quenching the steel plate to 10 μm or less has been proposed. Thereby, a molded part with good shape accuracy can be manufactured (for example, refer to Patent Document 1). Moreover, in the press hardening method of steel materials, the method of immersing in a cooling fluid in the state which restrained steel materials using the metal mold | die is proposed (for example, refer patent document 2). Thereby, the deformation | transformation and bending which generate | occur | produce in the case of hardening can be reduced also in high hardness steel materials. In addition, there has been proposed a method of quenching by constraining the outer diameter of the thin ring and the end face in the width direction with a collet (constraining member). Thereby, the deformation | transformation which generate | occur | produces in the case of quenching is suppressed (for example, refer patent document 3).
JP 2003-231915 A JP-A-7-157822 JP-A-5-33060

  However, even when a bearing is manufactured by applying the above-described method for suppressing deformation that occurs during quenching to a thin-walled bearing member for bearings, the life of the bearing is sufficient, considering the recent high required characteristics. Absent. Moreover, if the cost increases due to these measures, it will be against the above-mentioned demand for lower prices. Furthermore, when using induction hardening, which has been attracting attention in recent years, for quenching and hardening thin bearing members for bearings, the heating temperature tends to be excessive or insufficient. For this reason, strict temperature control is required to stabilize the quality of the bearing thin bearing member, but at present, no processing method or apparatus has been established.

  Accordingly, an object of the present invention is to produce a high-frequency heat treatment method capable of suppressing deformation of an object to be processed and capable of strict temperature control, a high-frequency heat treatment facility for performing the heat treatment method, and the heat treatment method. By providing a thin member whose deformation is suppressed and the quality is stable, and the thin member as a bearing ring, a long-life and stable quality thrust bearing is provided at low cost.

In the induction heat treatment method according to the present invention, a quenching temperature control step for adjusting the temperature of the workpiece and a workpiece whose temperature is controlled by the quenching temperature control step are cooled and hardened by quenching. A quenching timing control step for adjusting the quenching timing of the steel, and a quenching cooling step for cooling the workpiece to the quenching timing adjusted in the quenching timing control step. The quenching temperature control process includes a quenching heating process for heating the object to be processed by high-frequency heating, and a quenching temperature control temperature measuring process for acquiring temperature data for quenching temperature control that is temperature data of the object to be processed. Based on the temperature data for quenching temperature control acquired in the temperature measurement process for quenching temperature control, the heating temperature of the workpiece is controlled by outputting the quenching temperature control signal to the power source and controlling the power output. And adjusting the quenching temperature control step. The quenching timing control process includes the quenching timing control temperature measurement process for acquiring quenching timing control temperature data, which is the temperature data of the workpiece, and the quenching timing acquired in the quenching timing control temperature measurement process. And a quenching timing adjustment step of adjusting the heating time based on the control temperature data and outputting a quenching start signal. In the quenching and cooling process, cooling is performed based on the output of the quenching start signal while restraining the workpiece using a mold, and the cooling is performed as a cooling member for removing heat from the workpiece. by using a mold, it is carried out by cooling the object to be treated from a temperature above a _c1 point to M _s point or lower.

  In general, in induction hardening, first, a power output transition (power output pattern) consisting of parameters of power and time is determined as a heating condition (power control). The heating condition is determined by actually heat-treating the sample of the object to be processed while changing the power and time in consideration of the shape and material of the object to be processed. Here, in quenching of steel products, it is necessary to rapidly cool an object to be processed after it has been kept at a predetermined temperature for a predetermined time. However, it is difficult to accurately grasp the heating history of the workpiece by the above method (power control). Therefore, the heating conditions are experimentally determined by investigating the quality, such as hardness and microstructure, of the workpiece obtained by actually performing the heat treatment. As described above, the problem of the high-frequency heat treatment is that the heating history of the object to be processed cannot be accurately grasped and that the determination of the heating conditions requires experience and labor.

  On the other hand, in the high frequency heat treatment method of the present invention, heating of the workpiece is controlled using temperature and time as parameters (temperature control). Therefore, it is possible to accurately grasp the heating history of the object to be processed, and quenching can be performed by quenching after giving the necessary heating history to the object to be processed. As a result, it is not necessary to investigate the quality of the workpiece, such as the hardness and microstructure obtained by performing the heat treatment to determine the heating conditions, and the above-mentioned problems of the high-frequency heat treatment are solved. The quality of the object to be processed can be stabilized.

  Furthermore, since cooling is performed while restraining the workpiece using a mold in the quenching and cooling step, deformation of the workpiece to be generated during quenching can be suppressed.

Further, by cooling the quenching cooling step using the above mold as a cooling member for removing heat from the object to be processed, the object to be treated a cooling from a temperature above A _c1 point to M _s point below the temperature It is carried out by doing. Accordingly, since it is not necessary to use a cooling medium such as oil, it becomes easy to keep the working environment clean.

The _Ac1 point means a point corresponding to a temperature at which the steel starts to transform from ferrite to austenite when the steel is continuously heated. Further, the M _s point means a point corresponding to a temperature at which martensite formation starts when the austenitized steel is cooled.

  Preferably, in the high-frequency heat treatment method, the quenching timing control temperature data acquired in the quenching timing control temperature measurement step is temperature data of a portion of the workpiece that is difficult to rise in temperature.

  When the workpiece is heated rapidly by high frequency heating, the temperature of the workpiece is not necessarily uniform. In such a case, when cooling (quenching) is performed without giving a sufficient heating history to a relatively low temperature part in the object to be processed, the part is in an insufficiently hardened state, There is a risk that the workpiece will be defective. On the other hand, the occurrence of defective products can be suppressed by adjusting the quenching timing of the object to be processed based on the temperature data of the portion of the object to be processed where it is difficult to increase the temperature.

  It should be noted that the part where the temperature is difficult to rise in the workpiece is the amount of magnetic flux intrusion determined from the shape of the workpiece and the positional relationship between the workpiece and the high-frequency heating device in the entire workpiece. It refers to relatively few sites, preferably the least. For example, when induction heating is performed with the upper surface of an annular flat ring having a planar shape facing an induction coil of a high-frequency heating device and holding the lower surface with a jig, the portion where the temperature is difficult to rise is the lower surface, particularly the lower surface It is the vicinity which is in contact with the jig | tool.

  Preferably, in the above-described high-frequency heat treatment method, the quenching temperature control temperature data acquired in the quenching temperature control temperature measurement step is temperature data of a portion where the temperature is likely to rise in the workpiece.

  As described above, when the workpiece is rapidly heated by high-frequency heating, the temperature of the workpiece is not necessarily uniform. In such a case, when the temperature is extremely high (overheating) in a portion having a relatively high temperature in the workpiece, the amount of retained austenite in the portion after quenching becomes extremely large. There is a risk of problems such as abnormalities. On the other hand, the occurrence of defective products can be suppressed by adjusting the heating temperature of the object to be processed based on the temperature data of the part where the temperature is likely to rise in the object to be processed.

  In addition, the part where the temperature is likely to rise in the workpiece is the amount of magnetic flux intrusion determined from the shape of the workpiece and the positional relationship between the workpiece and the high-frequency heating device in the entire workpiece. It refers to relatively many sites, preferably the most sites. For example, when performing induction heating with the induction coil of a high-frequency heating device facing the upper surface of an annular flat ring having a planar shape and holding the lower surface with a jig, the portion where the temperature is likely to rise is the upper surface, particularly the upper surface In the vicinity of the coil.

  Preferably, the induction heat treatment method further includes a tempering step performed after the quenching and cooling step. The tempering step includes a tempering temperature control step for adjusting the temperature of the workpiece and a tempering end timing control step for adjusting the tempering end timing. The tempering temperature control process includes a tempering heating process for heating the object to be processed, a tempering temperature control temperature measuring process for acquiring temperature data for tempering temperature control that is temperature data of the object to be processed, and a tempering process. Based on the tempering temperature control temperature data acquired in the temperature measurement process for tempering temperature control, the tempering temperature control signal is output to the power source and the power output is controlled to adjust the heating temperature of the workpiece. And a return temperature adjusting step. The tempering end timing control process is acquired in a tempering end timing control temperature measurement process for acquiring temperature data for tempering end timing control, which is temperature data of the workpiece, and a tempering end timing control temperature measurement process. And a tempering end timing adjusting step for adjusting the heating time based on the tempering end timing control temperature data and outputting a tempering end signal.

  In tempering a steel product, the toughness and dimensional stability of the workpiece can be improved by applying a predetermined amount of heat to the quench-hardened workpiece to be softened. On the other hand, by performing the heat treatment by the temperature control as described above, it is possible to accurately grasp the heating history of the workpiece. As a result, it is possible to accurately determine the heating conditions necessary for tempering, and it is possible to reduce margins such as the heating time expected for performing reliable tempering. For this reason, tempering can be completed in the minimum necessary time, and productivity can be improved.

The induction heat treatment equipment according to the present invention is an induction heat treatment equipment used in the above-described induction heat treatment method. This induction heat treatment equipment has a quenching temperature control means for adjusting the temperature of the workpiece, a quenching timing control means for adjusting the quenching timing of the workpiece, and removing heat from the workpiece. Quenching and cooling means. Quenching cooling means is used as a cooling member for cooling the object to be treated from a temperature above A _c1 point to M _s point below the temperature by removing heat from the object to be processed while restraining an object to be processed Includes molds.

  According to the induction heat treatment equipment of the present invention, since the induction hardening method described above can be performed, time and experience are not required for determining the treatment conditions, and the quality of the workpiece can be stabilized. Furthermore, deformation of the workpiece can be suppressed. Furthermore, it becomes easy to keep the working environment clean.

  Preferably, in the induction heat treatment equipment, the quenching timing control means includes quenching timing control temperature measuring means for acquiring quenching timing control temperature data that is temperature data of the workpiece, and quenching timing control temperature measurement. A quenching timing adjusting means for adjusting the heating time based on the quenching timing control temperature data from the quenching timing control temperature measuring means and outputting a quenching start signal to the quenching cooling means. Have.

  This makes it easier to determine processing conditions and stabilizes the quality of the workpiece.

  Preferably, in the above induction heat treatment equipment, the quenching temperature control means acquires quenching heating means for heating the workpiece by induction heating, and quenching temperature control temperature data that is temperature data of the workpiece. Quenching temperature control means and quenching temperature control signal based on quenching temperature control temperature data from quenching temperature control temperature measuring means connected to quenching temperature control temperature measuring means Quenching temperature adjusting means for outputting to the heating means.

  This makes it easier to determine processing conditions and stabilizes the quality of the workpiece.

  Preferably, in the high-frequency heat treatment facility, the quenching timing control temperature data acquired by the quenching timing control temperature measuring means is temperature data of a portion where the temperature of the workpiece is difficult to rise.

  Thereby, generation | occurrence | production of inferior goods can be suppressed by adjusting the quenching time of a to-be-processed object based on the temperature data of the site | part which does not rise easily in a to-be-processed object.

  Preferably, in the high-frequency heat treatment equipment, the quenching temperature control temperature data acquired by the quenching temperature control temperature measuring means is temperature data of a portion where the temperature of the workpiece is likely to rise.

  Thereby, generation | occurrence | production of inferior goods can be suppressed by adjusting the heating temperature of a to-be-processed object based on the temperature data of the site | part where temperature rises easily in a to-be-processed object.

  Preferably, the high-frequency heat treatment facility further includes a tempering temperature control means for adjusting the temperature of the workpiece and a tempering finish timing control means for adjusting the tempering finish timing of the workpiece.

  Thereby, it becomes possible to perform heat treatment by temperature control even in the tempering step, and the heating history of the workpiece can be accurately grasped. As a result, tempering can be completed in the minimum necessary time, and productivity can be improved.

  Preferably, in the above induction heat treatment equipment, the tempering temperature control means includes a tempering heating means for heating the object to be processed, and a tempering temperature for acquiring temperature data for tempering temperature control which is temperature data of the object to be processed. Control temperature measuring means and a tempering temperature control signal connected to the tempering temperature control temperature measuring means based on the tempering temperature control temperature data from the tempering temperature control temperature measuring means Tempering temperature adjusting means for outputting to Further, the tempering end timing control means includes a tempering end timing control temperature measuring means for acquiring temperature data for tempering end timing control, which is temperature data of the workpiece, and a tempering end timing control temperature measuring means. Tempering end timing adjusting means for adjusting the heating time based on temperature data for tempering end timing control from the temperature measuring means for tempering end timing control connected to output a tempering end signal.

  As a result, the processing conditions can be determined more easily, and tempering can be completed in the minimum necessary time, thereby improving productivity.

  Preferably, in the high-frequency heat treatment equipment, the temperature data for tempering end timing control acquired by the temperature measuring means for tempering end timing control is temperature data of a portion where the temperature is unlikely to rise in the workpiece.

  As a result, by adjusting the tempering end timing of the object to be processed based on the temperature data of the part where the temperature is difficult to rise in the object to be processed, it is possible to avoid that the part is insufficiently tempered and to generate defective products. Can be suppressed.

  The thin member of the present invention is manufactured using the above-described high-frequency heat treatment method. According to the thin-walled member of the present invention, it is possible to reduce the cost because it is easy to determine the processing conditions, and it is possible to provide a thin-walled member that is suppressed in deformation during quenching and has a stable quality. it can.

  Here, in the present invention, the thin member refers to a member having a thickness of 3 mm or less at the thickest portion.

  The thin member may be used as a bearing ring of a thrust bearing. Since the thin member has excellent characteristics as described above, it is suitable as a bearing ring of a thrust bearing.

  The thrust bearing of the present invention includes a raceway ring that is the thin member and a rolling element that is disposed on a rolling surface of the raceway ring.

  According to the thrust bearing of the present invention, since the thin member having the above-described excellent characteristics is provided as the race, the thrust bearing having a long life and stable quality can be provided at low cost.

  As is clear from the above description, according to the high-frequency heat treatment method of the present invention, it is possible to provide a high-frequency heat treatment method that suppresses deformation of an object to be processed and enables strict temperature control. Moreover, according to the induction heat treatment equipment of the present invention, an induction heat treatment equipment for carrying out the induction heat treatment method of the present invention can be provided. Moreover, according to the thin member of this invention, a thin member with which the deformation | transformation was suppressed and the quality was stabilized can be provided. Further, according to the thrust bearing of the present invention, it is possible to provide a thrust bearing having a long life and stable quality at a low cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a diagram showing an outline of a heat treatment method according to Embodiment 1 which is an embodiment of the present invention. Moreover, FIG. 2 is a figure which shows the outline of the induction heating apparatus for hardening among the induction heat treatment equipment of Embodiment 1. FIG. FIG. 3 is a diagram showing an outline of a die restraint cooling device as a quenching cooling means in the heat treatment equipment of the first embodiment. FIG. 4 is a diagram showing an outline of the high-frequency heating apparatus for tempering in the high-frequency heat treatment equipment of the first embodiment. With reference to FIG. 1 to FIG. 4, the high-frequency heat treatment method and high-frequency heat treatment equipment of the first embodiment (when the bearing ring of the thrust bearing is heat-treated) will be described.

  Referring to FIG. 2, quenching high-frequency heating apparatus 2 included in the induction heat treatment facility of Embodiment 1 is a quenching temperature control for adjusting the temperature of raceway ring 11 as a workpiece to be heated. Means, and quenching timing control means for adjusting the quenching timing of the race 11. The quenching temperature control means includes quenching induction coil 22 and power supply 27 as quenching heating means, quenching temperature control thermometer 23 as quenching temperature control temperature measuring means, and quenching temperature control. As a quenching temperature adjusting means for connecting a quenching temperature control signal to the power supply 27 based on the quenching temperature control temperature data from the quenching temperature control thermometer 23 by connecting to the thermometer 23 and the power supply 27 A quenching temperature control device 25 (for example, a personal computer or the like) is provided.

  Further, the quenching timing control means includes a quenching timing control thermometer 24 as a quenching timing control temperature measuring means, a quenching timing control thermometer 24, and a mold-constrained cooling device 3 as a quenching cooling means. As a quenching timing adjusting means for adjusting the heating time based on the quenching timing control temperature data from the quenching timing control thermometer 24 and outputting a quenching start signal to the die restraint cooling device 3 A quenching time adjusting device 26 (for example, a personal computer) is provided.

  Furthermore, the quenching high-frequency heating device 2 includes a quenching turntable 21 made of a material having heat insulation properties and insulation properties (for example, ceramic). Further, the quenching turntable 21 has a protruding portion 21A for setting the raceway ring 11 as an object to be processed.

  Referring to FIG. 3, mold restraint cooling device 3 as quenching cooling means included in the induction heat treatment equipment of Embodiment 1 includes lower restraint mold 31 and upper restraint mold 32, and upper restraint mold 32. A downward load can be applied from above the mold by a pressing weight, a hydraulic cylinder, or the like.

  Referring to FIG. 4, tempering high-frequency heating apparatus 5 included in the induction heat treatment facility of Embodiment 1 is tempering temperature control for adjusting the temperature of raceway ring 11 as a workpiece to be heated. And a tempering end timing control means for adjusting the tempering end timing of the race 11. The tempering temperature control means includes a tempering induction coil 52 and a power source 57 as tempering heating means, a tempering temperature control thermometer 54 as tempering temperature control temperature measuring means, and a tempering temperature control. As a tempering temperature adjusting means that is connected to a thermometer 54 and a power source 57 and outputs a tempering temperature control signal to the power source 57 based on tempering temperature control temperature data from the tempering temperature control thermometer 54. A tempering temperature adjusting device 56 (for example, a personal computer) is provided.

  Further, the tempering end timing control means includes a tempering end timing control thermometer 54 (also serving as a tempering temperature control thermometer) as a tempering end timing control temperature measuring means, and a tempering end timing control. A tempering unit that is connected to the thermometer 54 and the power source 57 to adjust the heating time based on the tempering end timing control temperature data from the tempering end timing control thermometer 54 and outputs a tempering end signal to the power source 57 A tempering end time adjusting device 56 (also serving as a tempering temperature adjusting device) is provided as end time adjusting means.

  Furthermore, the tempering high-frequency heating device 5 includes a tempering rotary table 51 made of a heat insulating and insulating material (for example, ceramic). Further, the tempering rotary table 51 has a protruding portion 51A for setting the raceway ring 11 as an object to be processed.

  Next, the procedure of the high-frequency heat treatment will be described with reference to FIGS. As shown in FIG. 1, in the heat treatment method of the first embodiment, a quenching temperature control step and a quenching timing control step are first performed among the quench hardening steps. Specifically, referring to FIG. 2, raceway ring 11 is set so as to be in contact with the upper portion of protruding portion 21 </ b> A of quenching turntable 21. Next, a high frequency current is passed through the induction coil 22 for quenching, and the race 11 is induction heated. At this time, the race 11 is rotated by the quenching rotary table 21 in order to perform uniform heating.

  At this time, the quenching temperature control device 25 converts the temperature data (quenching temperature control temperature data) of the upper surface inner peripheral portion 11B, which is the portion where the temperature is most likely to rise in the race 11, to the quenching temperature control thermometer 23. To get through. Then, the quenching temperature control device 25 determines a necessary power output from the target temperature and the quenching temperature control temperature data, and causes the power supply 27 to output the necessary power to the quenching induction coil 22. Thereby, the race 11 is heated to the target temperature.

  On the other hand, the quenching timing adjusting device 26 uses the quenching timing control thermometer 24 to convert the temperature data (quenching timing control temperature data) of the lower surface jig contact portion 11C, which is the most difficult part of the race 11 to rise in temperature. To get through. Then, the quenching timing adjusting device 26 determines the quenching timing from the heating history to be given to the race 11 and the already given heating history, and outputs a quenching start signal to the die restraint cooling device 3. Thereby, the quenching temperature control process and the quenching timing control process of FIG. 1 are completed.

Next, a quenching and cooling process is performed as shown in FIG. Specifically, referring to FIG. 3, the race ring 11 that has been subjected to the quenching temperature control process and the quenching timing control process and has been heated to a temperature not _lower than the _{Ac 1} point is quenched by a moving means (not shown). It is carried from the high frequency heating device 2 to the mold restraining cooling device 3. The raceway ring 11 is immediately sandwiched between the lower restraint die 31 and the upper restraint die 32 of the die restraint cooling device 3, and a press weight is placed on the upper restraint die 32. As a result, the bearing ring 11 is restrained by the lower restraint die 31 and the upper restraint die 32, and the heat is removed by the lower restraint die 31 and the upper restraint die 32 as cooling members, whereby the _Ms point is obtained. It is rapidly cooled to the following temperature. Thereby, the quenching cooling process of FIG. 1 is complete | finished.

  Here, since the thickness of the bearing ring 11 is 3 mm or less and the heat capacity is small, it is sufficient to contact the lower restraint die 31 and the upper restraint die 32 without using a cooling medium such as oil and water. It is possible to cool rapidly.

  Next, a tempering step is performed as shown in FIG. Specifically, referring to FIG. 4, raceway ring 11 is set so as to be in contact with the upper side of protruding portion 51 </ b> A of tempering rotary table 51. Next, a high-frequency current is applied to the tempering induction coil 52, and the race 11 is induction-heated. At this time, the race 11 is rotated by the tempering rotary table 51 in order to perform uniform heating.

  At this time, the tempering temperature adjustment device 56 acquires the temperature data (tempering temperature control temperature data) of the race 11 via the tempering temperature control thermometer 54. Then, the tempering temperature adjusting device 56 determines a necessary power output from the target temperature and the tempering temperature control temperature data, and causes the power source 57 to output the tempering induction coil 52. Thereby, the race 11 is heated to the target temperature.

  On the other hand, the tempering end timing adjusting device 56 which also serves as the tempering temperature adjusting device is a temperature data (temperature data for tempering end timing control) of the lower surface jig contact portion 11C which is the most difficult part of the race 11 to rise in temperature. ) Is obtained through a tempering end timing control thermometer 54 that also serves as a tempering temperature control thermometer. Then, the tempering end timing adjustment device 56 determines the tempering end timing from the heating history to be given to the race 11 and the already given heating history, and outputs a tempering end signal to the power source 57 to stop heating. Is done. Thereby, the tempering process of FIG. 1 is complete | finished.

  Next, preferable conditions in the case where the race 11 is quenched and hardened using the mold restraint cooling device 3 described above will be described based on specific examples.

  For example, as a processing condition in the case of quenching and hardening the raceway ring 11 having an inner diameter of 60 mm, an outer diameter of 85 mm, and a thickness of 1 mm made of SAE1070 using the mold restraint cooling device 3, the heating temperature is 900 ° C. to 1050 ° C. The heating time is preferably 0.5 seconds to 5 seconds, the restraint (press) pressure is preferably 11.7 kPa or more, and the restraint time is preferably 2 seconds or more. The material of the upper restraint mold restraint part 32A of the upper restraint mold 32 and the lower restraint mold restraint part 31A of the lower restraint mold 31 is the surface of the upper restraint mold restraint part 32A and the lower restraint mold restraint part 31A. From the viewpoint of preventing damage, it is preferable to have a hardness equal to or higher than the hardened and hardened race ring 11, for example, hardened and hardened bearing steel, carbon steel, and stainless steel are preferable. . Moreover, the material of the lower restraint die 31 and the upper restraint die 32 is preferably a material having high thermal conductivity and corrosion resistance.

  Further, regarding the size of the lower restraint die 31 and the upper restraint die 32, it is necessary that the heat capacity difference with the raceway ring 11 to be hardened by hardening is large, and the lower restraint die 31 and the upper restraint die 32 are required. The volume of each is preferably 50 times or more the volume of the race 11. It is to be noted that the lower restraint die 31 and the upper restraint die 32 and the race ring 11 to be hardened by hardening are necessary by using a cooling means including a coolant circulation means for flowing a coolant such as water into the die. It is possible to reduce the volume ratio, and thus the mold restraint cooling device 3 can be made compact. In addition, the same effect can be obtained by using a cooling means including a cooling gas supply member for blowing and cooling a gas such as air to the lower restraint die 31 and the upper restraint die 32. In this case, dust attached to the lower restraint die 31 and the upper restraint die 32 can be removed by blowing the gas.

  The accuracy of the lower restraint mold restraint portion 31A and the upper restraint die restraint portion 32A is preferably high because it affects the accuracy of the raceway ring 11 to be hardened and hardened. That is, it is preferable that warpage and undulation are small and the surface roughness is small (polishing finish level).

  The heating and cooling in the quench hardening treatment can be performed in an air atmosphere, but preferably in an atmosphere that suppresses oxidation, for example, in a gas atmosphere having poor reactivity such as nitrogen.

  Usually, when the bearing ring 11 is manufactured under the above-described conditions, if the tempering temperature is 150 ° C. or less, the bearing ring 11 having a surface hardness of 730 HV and a raceway warpage of 30 μm or less can be manufactured.

  Next, preferable conditions in the case where the quench hardening process of FIG. 1 is performed on the raceway ring 11 using the above-described quenching high-frequency heating device 2 will be described based on specific examples.

  FIG. 5 is a TTA (Time Temperature Authentication) diagram of JIS SUJ2 material. FIG. 6 is an explanatory diagram showing the relationship between the quenching temperature and the holding time for explaining a method of integrating the value of the carbon diffusion distance Dep from the temperature transition. In the upper left graph of FIG. 6, the temperature transition on the quenching temperature control side and the quenching timing control side is shown with the time t on the horizontal axis and the temperature T on the vertical axis. The upper right diagram is an enlarged view of the area α of the upper left graph. Further, the lower part shows a calculation formula for integrating the value of the correction Dep from the temperature transition. With reference to FIG. 5 and FIG. 6, a specific example in which the SUJ2 material raceway ring is quenched and cured using the above-described quenching high-frequency heating device 2 will be described.

  For example, from the viewpoint of strength, 180 ° C. is used as a standard value when quenching and hardening a raceway ring 11 having an inner diameter of 60 mm, an outer diameter of 85 mm, and a thickness of 1 mm made of SUJ2 using the above-described quenching high-frequency heating device 2. The tempering hardness when tempering is HRC58 or higher, and the retained austenite amount is set to 12% or less from the viewpoint of dimensional stability. A TTA (Time Temperature Authentication) diagram of the SUJ2 material showing the relationship between the quenching temperature and the holding time necessary to satisfy this standard is shown in FIG. Region A in FIG. 5 is a range that does not satisfy the hardness standard, region B is a range in which the amount of retained austenite does not satisfy the standard, and region C is a range that satisfies any heat treatment standard. Hardness tends to meet specifications as the quenching temperature and time increase. On the other hand, the austenite amount does not satisfy the standard as the quenching temperature and time increase.

  As is apparent from the TTA diagram of FIG. 5, in order to satisfy the heat treatment quality standard, it is easier to control the heat treatment quality by setting conditions at a relatively low temperature for a long time. In order to take advantage of the short-time treatment of the high-frequency heat treatment, it is desirable to perform treatment at as high a temperature as possible for a short time. The heat pattern at the temperature measurement position of the quenching temperature control thermometer can be determined based on the balance between the reduction in the number of heat treatment steps and the ease of control. If a relationship diagram (TTA diagram) between the heating time and the holding time with respect to the heat treatment quality according to the type of material can be created, the conditions can be determined according to the diagram, so the heat treatment apparatus of the present invention is a material It can be used regardless of the type.

  Referring to FIG. 2, the determined heating condition is input to a quenching temperature adjusting device 25 such as a personal computer. The quenching temperature control device 25 is connected to a quenching temperature control thermometer 23 and a power source 27, and based on the quenching temperature control temperature data from the quenching temperature control thermometer 23, PID (Proportional Integral). A high-frequency current flowing through the induction coil 22 for quenching can be controlled by outputting a quenching temperature control signal to the power source 27 by differential control. Thereby, the heat pattern of the upper surface inner peripheral portion 11 </ b> B that is the portion where the temperature is most likely to rise in the race 11 can be controlled. At the same time, the quenching timing control temperature data acquired by the quenching timing control thermometer 24 is taken into the quenching timing adjusting device 26 such as a personal computer, and it is determined whether the heating is sufficient from the heat pattern, Adjust the time of quenching. The determination of the quenching time is made based on whether or not the heat pattern of the lower surface jig contact portion 11C, which is the part where the temperature is most difficult to rise in the raceway ring 11, falls within the specifications on the TTA diagram.

  For example, the following equations (1) and (2) can be used to determine whether or not the values are within the standard on the TTA diagram.

The structure of the steel before quenching is a distribution of iron and carbide in which some carbon is dissolved. In the quenching, carbon in the carbide needs to be dissolved in iron, but it can be considered that the time during which carbon is uniformly dissolved in iron corresponds to the carbon diffusion distance Dep. From this point of view, quenching can be performed when the value of Dep reaches a certain value D ^* ep.

  Actually, since the heat pattern of the lower surface jig contact portion 11C, which is the portion where the temperature is most difficult to rise in the race 11, changes every moment, the value of Dep needs to be integrated as shown in FIG. . When the temperature increase of the bearing ring 11 is started, the temperature rising pattern on the quenching timing control side (the lower surface jig contact portion 11C of the bearing ring 11 shown in FIG. 2) indicates that the penetration of magnetic flux is on the quenching temperature control side (see FIG. 2). The temperature rises with a delay compared to the quenching temperature control side because it is smaller than the inner peripheral portion 11B) of the upper surface of the bearing ring 11 shown. Usually, when the temperature exceeds 723 ° C., the austenitization of iron starts, but when the heating rate is fast, the iron heating transformation temperature changes, so the temperature for calculating the diffusion distance does not change with the heating rate. Must not.

Referring to FIG. 2, the heating rate varies depending on the capability of the power source 27, the shapes of the induction coil 22 for quenching and the race 11, etc. It is preferable to do this. From the point where the temperature on the quenching timing control side exceeds the heating transformation temperature, as shown in FIG. 6, the region α diffusion distance is calculated by the equation in the figure. When Dep at any time exceeds D ^* ep, quenching is started immediately. The value of D ^* ep is preferably as small as possible within a range in which a predetermined heat treatment quality can be maintained from the viewpoint of shortening the heat treatment time. However, from the standpoint of quality stability, it is desirable to use a set value with some safety.

  In the thrust bearing of the first embodiment, the raceway ring 11 which is the thin member of the first embodiment subjected to the high-frequency heat treatment by the above-described method and the rolling elements arranged on the rolling surface of the raceway 11 are combined. A thin-walled thrust roller bearing can be manufactured.

  FIG. 7 is a schematic cross-sectional view showing a configuration of a thin-walled thrust roller bearing that is the thrust bearing of the first embodiment. The configuration of the thrust bearing of the first embodiment will be described with reference to FIG.

  As shown in FIG. 7, the thin-walled thrust roller bearing 1 includes, for example, a pair of race rings 11, 11, rollers 12 as a plurality of rolling elements, and an annular cage 13. The roller 12 is disposed between the pair of raceways 11 and 11 in contact with the rolling surfaces 11A and 11A of the raceways 11 and 11. Further, the rollers 12 are arranged at a predetermined pitch in the circumferential direction by a cage 13 and are held so as to be able to roll. Thereby, each of the race rings 11 and 11 can rotate relatively to each other.

(Embodiment 2)
FIG. 8 is a diagram showing an outline of a mold-restrained tempering device in the induction heat treatment facility of Embodiment 2 which is an embodiment of the present invention. With reference to FIG. 8, the high frequency heat treatment method and high frequency heat treatment equipment of the second embodiment (when the bearing ring of the thrust bearing is heat treated) will be described.

  The high-frequency heat treatment method, high-frequency heat treatment equipment, thin-walled member, and thrust bearing in the second embodiment have basically the same configurations as the high-frequency heat treatment method, high-frequency heat treatment equipment, thin-walled member, and thrust bearing in the first embodiment. . However, the second embodiment is different from the first embodiment in that a mold-restrained tempering device is used instead of the tempering high-frequency heating device 5 of the first embodiment.

  Referring to FIG. 8, the die restraint tempering device 6 included in the induction heat treatment facility according to the second embodiment includes a lower restraint die 61 for tempering and an upper restraint die 62 for tempering. A downward load can be applied from above the upper upper restraint mold by a press weight, a hydraulic cylinder, or the like. Furthermore, the tempering lower restraint mold restraint part 61A and the tempering upper restraint mold restraint part 62A, which are parts restraining the raceway ring 11, and the contact part between the raceway ring 11 and the raceway ring 11 respectively serve as restraint part temperature measuring means. One end of the thermocouples 63 and 64 is connected, and temperature data for tempering (temperature data for tempering temperature control and temperature data for tempering end timing control) that is the temperature of the race 11 can be acquired. The other ends of the thermocouples 63 and 64 are connected to a mold heating control device 65 such as a personal computer that receives the temperature data for tempering from the thermocouple and controls the heating of the mold. The apparatus 65 is connected to a mold heating device 66 as mold heating means for heating the mold connected to the tempering lower restraint mold 61 and the tempering upper restraint mold 62. As the mold heating device 66, for example, a device that heats the tempering lower restraint die 61 and the tempering upper restraint die 62 by supplying electric power to a heating wire or the like can be used. Further, as the mold heating device 66, for example, a device that heats the lower tempering die 61 and the upper tempering die 62 for tempering by induction heating may be used.

  Next, the tempering process using the die restraint tempering device 6 will be described. The bearing ring 11 on which the quench hardening process has been performed is carried from the die restraint cooling device 3 to the die restraint tempering device 6 by a moving means (not shown). The bearing ring 11 is sandwiched between a tempering lower restraint die 61 and an tempering upper restraint die 62 heated by the die heating device 66, and is further pressed to the tempering upper restraint die 62. A weight is placed. As a result, the race 11 is heated while being restrained by the tempering lower restraint die 61 and the tempering upper restraint die 62. Here, the mold heating control device 65 controls the output of the mold heating device 66 based on the tempering temperature data, and determines the tempering end time from the amount of heat given to the race 11 in the tempering step. . When the tempering end time is reached, the heating is stopped and the restraint of the race ring 11 by the tempering lower restraint die 61 and the tempering upper restraint die 62 is released. It is taken out from the die restraint tempering device 6. Thereby, the tempering process of FIG. 1 is complete | finished.

  In the first and second embodiments, the quenching high-frequency heating device 2, the tempering high-frequency heating device 5, and the mold-restraining tempering device 6 are provided with thermometers as temperature measuring means. This thermometer may be a non-contact type thermometer such as a radiation thermometer, or may be a contact type thermometer such as a thermocouple if possible on the layout of the apparatus. Further, at least one thermometer may be provided, but it is preferable to provide a plurality of thermometers if the layout of the apparatus is possible. When a plurality of thermometers are provided, it is preferable to control the apparatus so that the heat treatment is completed in a short time while reducing the difference in temperature measured by each thermometer. Further, a quenching temperature adjusting device 25 such as a personal computer, a quenching time adjusting device 26, a tempering end timing adjusting device 56, a tempering temperature adjusting device 56, and a mold heating control device 65 are provided as necessary. Alternatively, a single personal computer or the like may serve as a plurality of devices.

  Examples of the present invention will be described below. The quenching high-frequency heating device 2 of FIG. 2 and the mold of FIG. 3 described in the above-described first embodiment for a thrust bearing race ring having an inner diameter of 60 mm, an outer diameter of 85 mm, and a thickness of 1 mm made of SUJ2. The quench hardening process of FIG. 1 was implemented using the constrained cooling device 3. The temperature on the quenching temperature control side was set to 950 ° C. On the other hand, conventional induction hardening was performed on similar thrust bearing rings. Specifically, after heating by the condition of the output to the induction coil and the heating time (1.5 seconds) that the operator has determined to be optimal from the color of the raceway being heated, the die restraint cooling of FIG. It hardened and hardened by cooling using the apparatus 3 (comparative example).

  Ten of each of the above-described examples and comparative examples were produced, and the hardness, the amount of retained austenite, the amount of dimensional change before and after quenching, the amount of warpage of the races, and the presence or absence of incompletely quenched structure The investigation was conducted. The results of measurement and investigation are shown in Table 1.

  In Table 1, the maximum hardness is the maximum value of the hardness in each of 10 samples. Further, the hardness unevenness indicates the maximum value in each of 10 samples by measuring the difference between the maximum hardness and the minimum hardness in each sample. Further, the difference in the amount of retained austenite indicates the difference between the maximum value and the minimum value obtained by measuring the amount of retained austenite at a position of 0.05 mm from the surface of the raceway for each of 10 samples. The maximum value of the outer diameter dimensional difference is a value obtained by measuring a change in the outer diameter before and after quenching and showing the maximum value in each of ten samples. The maximum value of warpage is the difference between the maximum value and the minimum value of the height from the horizontal plane to the top surface of the track ring when the track ring is placed on the horizontal plane so that the rolling surfaces of the track ring face each other. The maximum value of the difference in each of 10 samples is shown. In addition, in order to investigate the occurrence of incompletely hardened structure, the microstructure of each of the 10 samples after quenching was investigated, and the presence of a part that was not a martensite structure (incompletely hardened structure) was investigated. It is a result.

  Referring to Table 1, when the raceway of the example and the raceway of the comparative example are compared, the hardness of the raceway of the example is smaller than that of the raceway of the comparative example, although the hardness is smaller. ing. In addition, the difference in the amount of retained austenite is smaller in the examples than in the comparative example, and the change in outer diameter due to quenching and the amount of warpage are also small. Further, in the example, an incompletely hardened structure was not generated, whereas in the comparative example, an incompletely hardened structure was generated in a portion where the jig for holding the raceway was in contact with the raceway.

  Such a difference between the example and the comparative example is considered to be caused by a variation in temperature among the race rings during heating and a variation in heating conditions between the race rings. Specifically, in the embodiment, the actual temperature of the bearing ring during heating is measured, and heating is performed accordingly. In addition, heating is controlled so as to reduce a temperature difference between a portion where the temperature is likely to rise and a portion where the temperature is difficult to rise while confirming that the portion where the temperature is difficult to rise is sufficient in the race. For this reason, an incompletely hardened structure does not occur even in a region where the temperature is difficult to rise, and variations in quality (hardness, amount of retained austenite, dimensions) are small.

  On the other hand, in a comparative example, it heats on the fixed conditions which the operator judged to be the optimal from the color of the raceway under heating. Therefore, it is difficult to consider the temperature at all parts in the race. For this reason, a difference in quality among the bearing rings is likely to occur, and in a region where the temperature of the bearing rings is difficult to rise, heating is insufficient and an incompletely hardened structure is generated. In addition, since heating is performed with the power supply output and the heating time being constant, if a difference occurs in the setting position when setting the race ring in the heating device, a difference occurs in the actual heating temperature. Therefore, a difference in quality is easily generated between the races.

  From the above results, it can be seen that according to the induction hardening method of the present invention, quality variation between the race rings and within the race rings can be reduced as compared with the conventional induction hardening method. Moreover, according to the induction hardening method of this invention, it turns out that malfunctions, such as generation | occurrence | production of incompletely hardened structure, can also be suppressed.

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The high-frequency heat treatment method, high-frequency heat treatment equipment, thin-walled member, and thrust bearing of the present invention are a high-frequency heat treatment method, high-frequency heat treatment equipment that controls heating based on the temperature of an object to be processed, and a thin-walled member and thrust bearing manufactured using the same. It is applied particularly advantageously.

2 is a diagram showing an outline of a heat treatment method according to Embodiment 1. FIG. It is a figure which shows the outline of the induction heating apparatus for hardening among the induction heat treatment equipment of Embodiment 1. FIG. It is a figure which shows the outline of the metal mold | die constrained cooling device as a quenching cooling means among the heat processing facilities of Embodiment 1. FIG. It is a figure which shows the outline of the high frequency heating apparatus for tempering among the high frequency heat treatment equipment of Embodiment 1. FIG. It is a TTA (Time Temperature Authentication) diagram of a JIS SUJ2 material. It is explanatory drawing which shows the relationship between the quenching temperature and the holding time for demonstrating the method of integrating | accumulating the value of the carbon diffusion distance Dep from temperature transition. 1 is a schematic cross-sectional view showing a configuration of a thin-walled thrust roller bearing that is a thrust bearing of Embodiment 1. FIG. It is a figure which shows the outline of a metal mold | die restraint tempering apparatus among the high frequency heat processing equipment of Embodiment 2. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Thin-walled thrust roller bearing, 2 High-frequency heating apparatus for quenching, 3 Mold restraint cooling apparatus, 5 High-frequency heating apparatus for tempering, 6 Mold restraint tempering apparatus, 11 Race ring, 11A Rolling surface, 11B Inner surface of upper surface Part, 11C bottom jig contact part, 12 rollers, 13 cage, 21 quenching rotary table, 21A protrusion, 22 quenching induction coil, 23 quenching temperature control thermometer, 24 quenching time control temperature 25, quenching temperature control device, 26 quenching time control device, 27 power supply, 31 lower restraint die, 31A lower restraint die restraint, 32 upper restraint die, 32A upper restraint die restraint, 51 quenching Rotation table for tempering, 51A protrusion, 52 induction coil for tempering, 54 thermometer for tempering temperature control (thermometer for tempering end timing control), 56 temperature adjusting device for tempering (tempering end time adjusting device) 57 power supply, 61 tempering lower restraint die, 61A tempering lower restraint die restraint, 62 tempering upper restraint die, 62A tempering upper restraint die restraint, 63 thermocouple, 64 thermocouple, 65 gold Mold heating control device, 66 Mold heating device.

Claims (6)

A quenching temperature control process for adjusting the temperature of the workpiece,
A quenching timing control step of adjusting the quenching timing for cooling and quenching the workpiece whose temperature is controlled by the quenching temperature control step; and
A quenching cooling step for cooling the object to be treated at the quenching time adjusted in the quenching time control step,
The quenching temperature control step includes:
A heating process for quenching in which the workpiece is heated by high-frequency heating;
A temperature measurement process for quenching temperature control for obtaining temperature data for quenching temperature control, which is temperature data of the workpiece,
Based on the quenching temperature control temperature data acquired in the quenching temperature control temperature measurement step, the heating temperature of the workpiece is controlled by outputting a quenching temperature control signal to a power supply and controlling the power supply output. Including a quenching temperature adjustment process for adjusting
The quenching time control step is
A temperature measurement process for quenching timing control that acquires temperature data for quenching timing control that is temperature data of the workpiece,
A quenching timing adjustment step of adjusting a heating time based on the quenching timing control temperature data acquired in the quenching timing control temperature measurement step and outputting a quenching start signal,
In the quenching cooling step, based on the output of the quenching start signal, the cooling is performed while restraining the workpiece using a mold,
The cooling by the use of the mold as the cooling member for removing heat from the object to be treated, the is performed by cooling the object to be treated from a temperature above A _c1 point to M _s point below the temperature A high-frequency heat treatment method. A tempering step further performed after the quenching and cooling step;
The tempering step includes
A temperature control step for tempering for adjusting the temperature of the workpiece;
Including a tempering end timing control step for adjusting the tempering end timing,
The temperature control process for tempering includes
A heating step for tempering for heating the workpiece;
A tempering temperature control temperature measurement step for obtaining temperature data for tempering temperature control, which is temperature data of the object to be processed,
Based on the temperature data for tempering temperature control acquired in the temperature measuring step for tempering temperature control, the heating temperature of the object to be processed is controlled by outputting a tempering temperature control signal to a power source and controlling power output. A tempering temperature adjusting step for adjusting
The tempering end timing control step includes:
A tempering end timing control temperature measurement step for obtaining temperature data for tempering end timing control, which is temperature data of the workpiece,
A tempering end timing adjustment step of adjusting a heating time based on the temperature data for tempering end timing control acquired in the temperature measurement step for tempering end timing control and outputting a tempering end signal. 2. The high frequency heat treatment method according to 1. A high-frequency heat treatment facility used in the high-frequency heat treatment method according to claim 1,
Quenching temperature control means for adjusting the temperature of the workpiece;
Quenching timing control means for adjusting the quenching timing of the workpiece;
Quenching and cooling means for removing heat from the workpiece,
The quenching cooling means, cooling for cooling the temperature the object to be processed from the A _c1 point or a temperature below M _s point by removing heat from the object to be processed the processing object while constraining the Induction heat treatment equipment containing a mold used as a member. Tempering temperature control means for adjusting the temperature of the workpiece;
The induction heat treatment equipment according to claim 3, further comprising a tempering end timing control means for adjusting the tempering end timing of the workpiece.   A thin-walled member manufactured using the high-frequency heat treatment method according to claim 1. A bearing ring that is the thin member according to claim 5;
A thrust bearing comprising a rolling element disposed on a rolling surface of the raceway.

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