JP5311719B2 - Induction hardening method, mechanical member, rolling member, and manufacturing method of mechanical member - Google Patents

Description

  The present invention relates to an induction hardening method, a mechanical member, and a rolling member, and more specifically, induction hardening by heating a workpiece by induction heating and induction hardening, and induction hardening by induction hardening. The present invention relates to a mechanical member and a rolling member that are manufactured by being implemented.

  In recent years, the environment in which machine parts are used is increasing with the improvement in performance of industrial machines and transport machines that use rolling bearings such as rolling bearings, hubs, constant velocity joints, and machine parts including shafts. It has become even more severe. Therefore, for mechanical members including rolling elements such as race rings and rolling elements and shafts that make up mechanical parts, higher strength and longer life, especially higher strength and longer life in harsh environments. Is required.

  The environment in which machine parts are used is diverse. For example, surface damage due to poor lubrication occurs when used in a high temperature environment, and damage due to corrosion occurs when used in a corrosive environment. Also, in machine parts that operate at high speed, as a countermeasure against creep, members are often fitted with high fit and used in a state where tensile stress acts on the surface. The resulting decrease in strength becomes a problem.

On the other hand, by carrying out surface hardening treatment by carburizing quenching or induction hardening for the purpose of improving the material constituting the machine member or generating a compressive stress on the surface of the machine member, Measures for achieving high strength and long life have been proposed. (For example, see Patent Documents 1 to 5).
JP 2005-291340 A JP 2000-80446 A JP 2002-102927 A JP 2005-299854 A JP-A-6-57324

  However, the surface hardening treatment by carburizing and induction hardening is not necessarily sufficient in terms of rigidity and strength because the inside of the mechanical member is not hardened. For example, in rolling rings and rolling elements of rolling bearings that are rolling members, there are problems such as the occurrence of case cracks due to insufficient internal strength and insufficient crack strength when a large load is applied. There is. In addition, the shaft has problems such as insufficient torsional strength due to insufficient internal strength. In addition, for the purpose of improving corrosion resistance and heat resistance, when high alloy steel containing a large amount of alloy elements such as chromium (Cr) is adopted for steel constituting the mechanical member, the hardenability of the material is increased, The countermeasure of quenching and hardening only the surface layer portion of the machine member by induction hardening has a problem that it is difficult to control the heat treatment.

  Furthermore, measures by improving the material cause an increase in material cost, and adopting carburizing and quenching with a long processing time or other complicated heat treatment process causes an increase in manufacturing cost. This is contrary to the recent demand for cost reduction and is a major obstacle to the adoption of the countermeasure.

  Therefore, an object of the present invention is to provide an induction hardening method capable of increasing the strength and extending the life of an object to be processed while suppressing an increase in manufacturing cost. Another object of the present invention is to provide a mechanical member and a rolling member that have a high strength and a long life even in a harsh environment while suppressing an increase in manufacturing cost.

In the induction hardening method in one aspect of the present invention, the whole object to be treated is heated by high frequency heating and cooled from a temperature of A ₁ point or higher to a temperature of M _S point or lower, whereby the whole object to be treated is cooled. This is an induction hardening method for quench hardening. The induction hardening method includes a temperature control step in which the temperature of the object to be processed is adjusted, and a high temperature quenching in which the stress applying part, which is a part to which compressive stress is to be applied, is at a temperature of A ₁ point or higher. A state in which the quenching control unit that is heated to a temperature and is a part other than the stress applying unit is at a temperature of A1 or higher and is heated to a low-temperature quenching temperature that is lower than the high-temperature quenching temperature. And a quenching control step of quenching and hardening the entire workpiece by cooling the workpiece to a temperature equal to or lower than the _MS point.

In general, in the induction hardening process, only a part of the surface layer portion of the workpiece is heated, and is hardened by hardening from a temperature of A ₁ point or higher to a temperature of M _S point or lower. Here, when the steel constituting the object to be processed by quench hardening undergoes martensitic transformation, the transformation involves expansion of the volume, so that extremely high compressive stress remains in the hardened and hardened surface layer portion. As a result, a portion of the surface layer portion has not only high hardness but also crack generation and growth are suppressed, so that a long life can be obtained by imparting high fatigue strength to the workpiece.

  However, in consideration of the recent severe use environment of mechanical members as described above, in mechanical members subjected to induction hardening that quenches and hardens only a part of the surface layer portion, other hardened and hardened other members There is a problem due to insufficient strength of the part.

  On the other hand, the present inventor has improved the fatigue strength by leaving the compressive stress in a part of the surface layer portion of the object to be processed (mechanical member), and securing the overall strength by improving the hardness of other portions. As a result of intensive studies on compatible heat treatment methods, the following findings were obtained.

That is, the heating temperature entire article to be treated by being cooled to a temperature below M _S point from the temperature of the _one or more points A, even if the entire article to be treated is quench-hardened, a different by site By cooling and quenching and hardening, the concentration of carbon dissolved in the steel substrate constituting the object to be processed (solid solution carbon concentration) is changed depending on the part, and is practically large enough for the desired part. The compressive stress can be imparted. In other words, by increasing the solute carbon concentration of the desired part relative to other parts, the expansion rate of the part due to quenching is made larger than other parts, and compressive stress remains in the part. It is possible to make it.

According to the induction hardening method in one aspect of the present invention, in the temperature control step, the temperature of the object to be processed is adjusted, and in the quenching control step, a stress applying portion that is a portion to which compressive stress is to be applied is provided. Since it is cooled to a temperature equal to or lower than the _MS point from the state of being heated to a temperature higher than that of the part, the solid solution carbon concentration in the stress applying portion is relatively higher than that of the other part. As a result, compressive stress is applied to the stress applying portion, and the fatigue strength is improved. On the other hand, since the portions other than the stress applying portion are colder than the stress applying portion, the portions other than the stress applying portion are cooled to a temperature not higher than the M _S point from the temperature of A ₁ point or higher, and are hardened and hardened. Is sufficiently secured. As a result, it is possible to increase the strength and life of the workpiece. Furthermore, the induction hardening method according to one aspect of the present invention does not employ a heat treatment method including carburizing and quenching with a long treatment time or other complicated heat treatment steps, so that the above-described excellent performance can be achieved while suppressing manufacturing costs. Characteristics can be imparted to the workpiece. In addition, by using high-frequency heating for heating the object to be processed, for example, it becomes easy to change the temperature of the object to be processed between a part close to the induction coil and a part far from the induction coil.

  As described above, according to the induction hardening method in one aspect of the present invention, there is provided an induction hardening method capable of increasing the strength and extending the life of an object to be processed while suppressing an increase in manufacturing cost. be able to.

  Preferably, in the induction hardening method according to the first aspect, the temperature control step is based on a temperature measurement temperature measurement step in which the temperature of the workpiece is measured and information on the temperature measured in the temperature control temperature measurement step. And a temperature adjusting step for outputting a temperature control signal for controlling the heating state of the workpiece, and a heating step for heating the workpiece by high-frequency heating based on the temperature control signal. Furthermore, the quenching control process is based on the temperature measurement process for quenching in which the temperature of the stress applying part and the quenching control part of the workpiece is measured, and the temperature information measured in the temperature measurement process for quenching, Heating time is adjusted so that the stress applying part is heated to the high-temperature quenching temperature and the quenching control part is heated to the low-temperature quenching temperature, the timing at which the workpiece should be cooled is determined, and a cooling start signal And a cooling process in which the workpiece is quenched and hardened by cooling the workpiece based on the cooling start signal.

  In the induction hardening, unlike the quenching method in which the object to be processed is heated through the atmosphere in the furnace like a general atmosphere furnace, the object to be processed is directly heated by induction heating. Therefore, in order to measure the temperature of the workpiece, it is necessary to directly measure the temperature of the workpiece. However, induction hardening equipment is often provided with a drive mechanism for rotating the object to be processed to uniformly heat the object to be processed, and it is difficult to install a contact-type thermometer. There are many cases.

  Thus, in induction hardening, it is not easy to measure the temperature of the workpiece, and it is difficult to control the heat treatment (temperature control) according to the heat treatment conditions of temperature and time. Therefore, in general, in the induction hardening, heat treatment control (power control) based on heat treatment conditions of electric power and time is often employed. In the induction hardening by this power control, the heating history applied to the workpiece is not always clear.

  In contrast, in a preferred embodiment of the induction hardening method according to one aspect of the present invention, in the temperature control step, the temperature data of the workpiece is fed back in real time to heat the workpiece to a desired temperature. In the quenching control process, the temperature information of both the stress applying part and the quenching control part of the workpiece is acquired in real time, and the cooling timing is determined based on this information to quench and cure the workpiece. can do. Therefore, it becomes easy to adjust the heating time so that the stress applying part is heated to the high-temperature quenching temperature and the quenching control part is heated to the low-temperature quenching temperature.

  Here, the quenching control unit can be a part where the penetration of the magnetic flux is the smallest and the temperature rise is small in the workpiece, for example. Moreover, in order to give a clear compressive stress to a stress provision part, it is preferable that high temperature quenching temperature is 20 degreeC or more higher than low temperature quenching temperature. Furthermore, in order to give a sufficient compressive stress to the stress applying part, it is more preferable that the high temperature quenching temperature is 50 ° C. or higher than the low temperature quenching temperature.

Induction hardening method according to another aspect of the present invention, by cooling the whole from heating to A ₁ point or more temperature M _S point below the temperature of the object to be processed by high-frequency heating, the whole of the object This is an induction hardening method for quench hardening. The induction hardening method includes a temperature control step in which the temperature of the object to be processed is adjusted, and a quenching temperature at which the stress applying part, which is a part to which compressive stress is to be applied, is at a temperature of A ₁ point or higher. The workpiece is heated to the quenching temperature for a shorter time than the stress applying portion and the workpiece is heated to a temperature lower than the M _S point. And a quenching control step of quenching and hardening the entire workpiece by cooling.

According to the induction hardening method in another aspect of the present invention, in the workpiece, the stress applying portion, which is a portion to which compressive stress is to be applied, is at a temperature of A ₁ point or more than the portion other than the stress applying portion. Heated to a certain quenching temperature for a long time. Therefore, similarly to the induction hardening method according to one aspect of the present invention, the solute carbon concentration is relatively higher in the stress applying portion than in the portion other than the stress applying portion. As a result, compressive stress is applied to the stress applying portion, and the fatigue strength is improved and the life is extended. On the other hand, since the portion other than the stress applying portion is a shorter time than the stress applying portion, it is quenched and hardened by being cooled to a temperature not higher than the _MS point from a state heated to a temperature of A ₁ point or higher. The strength of portions other than the stress applying portion is also sufficiently secured. As a result, it is possible to increase the strength and life of the workpiece. Furthermore, the induction hardening method according to another aspect of the present invention does not employ a heat treatment method including carburizing and quenching with a long treatment time or other complicated heat treatment steps, so that the above-described excellent performance can be achieved while suppressing manufacturing costs. Characteristics can be imparted to the workpiece. In addition, by using high-frequency heating for heating the workpiece, for example, the time during which the workpiece is held at the quenching temperature can be easily changed between the portion near the induction coil and the portion far from the induction coil. Can be made.

  As described above, according to the induction hardening method according to another aspect of the present invention, there is provided an induction hardening method capable of increasing the strength and extending the life of a workpiece while suppressing an increase in manufacturing cost. be able to.

  In the induction hardening method according to the other aspect of the present invention, preferably, the temperature control step includes a temperature control temperature measurement step in which the temperature of the workpiece is measured, and a temperature measured in the temperature control temperature measurement step. A temperature adjusting step for outputting a temperature control signal for controlling the heating state of the workpiece based on the information; and a heating step for heating the workpiece by high-frequency heating based on the temperature control signal. It is out. The quenching control process is based on the temperature measurement process for quenching in which the temperatures of the stress application part and quenching control part of the workpiece are measured, and the temperature information measured in the temperature measurement process for quenching. The heating time is adjusted so that the part is heated to the quenching temperature, and the quenching control part is heated to the quenching temperature for a shorter time than the stress applying part, and the timing for cooling the workpiece is determined. It includes a cooling timing adjustment step in which a cooling start signal is output and a cooling step in which the workpiece is quenched and hardened by cooling the workpiece based on the cooling start signal.

  Thereby, in the temperature control process, the temperature data of the workpiece is fed back in real time to heat the workpiece to a desired temperature, and in the quenching control process, the stress applying portion and the quenching of the workpiece are quenched. Information on both temperatures of the control unit is acquired in real time, and based on this, the timing of cooling can be determined, and the workpiece can be hardened by hardening. Therefore, it becomes easy to adjust the heating time so that the stress applying part is heated to the quenching temperature for a desired time and the quenching control part is heated to the quenching temperature for a shorter time than the stress applying part. .

  Here, the quenching control unit can be a part where the penetration of the magnetic flux is the smallest and the temperature rise is small in the workpiece, for example. Further, in order to give a clear compressive stress to the stress applying part, the time during which the quenching control part is held at the quenching temperature or higher is the time during which the stress applying part is held at the quenching temperature. It is preferable that it is 1/3 or less. Furthermore, in order to give a sufficient compressive stress to the stress applying part, the time during which the quench control part is held at the quenching temperature or higher is the time during which the stress applying part is held at the quenching temperature. It is more preferable that it is 1/5 or less.

  The mechanical member according to the present invention is produced by quenching and hardening by the induction hardening method of the present invention. According to the mechanical member of the present invention, the workpiece is hardened and hardened by the induction hardening method of the present invention, which can increase the strength and extend the life of the object while suppressing an increase in manufacturing cost. Thus, it is possible to provide a mechanical member having high strength and a long life even under a severe environment while suppressing an increase in manufacturing cost.

  The rolling member according to the present invention is produced by quenching and hardening by the induction hardening method of the present invention. According to the rolling member of the present invention, the workpiece is hardened and hardened by the induction hardening method of the present invention, which can increase the strength and extend the life of the object while suppressing an increase in manufacturing cost. Thus, it is possible to provide a rolling member having high strength and a long life even in a harsh environment while suppressing an increase in manufacturing cost.

  The mechanical members of the present invention are, for example, mechanical members made of steel such as gears and shafts, rolling rings and rolling elements of rolling bearings, rolling members such as outer races, inner races and rolling elements of constant velocity joints. Can be applied to.

  As is clear from the above description, according to the induction hardening method of the present invention, there is provided an induction hardening method capable of increasing the strength and extending the life of the workpiece while suppressing an increase in manufacturing cost. Can be provided. Furthermore, according to the mechanical member and the rolling member of the present invention, it is possible to provide a mechanical member and a rolling member that have a high strength and a long life even under a severe environment while suppressing an increase in manufacturing 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 schematic cross-sectional view showing a configuration of a rolling bearing inner ring as a mechanical member (rolling member) in the first embodiment which is an embodiment of the present invention. With reference to FIG. 1, the structure of the rolling bearing inner ring in Embodiment 1 is demonstrated.

  Referring to FIG. 1, a rolling bearing inner ring 1 as a rolling member in the first embodiment has an annular shape. The rolling bearing inner ring 1 is formed with a rolling surface 1C for rolling while a ball or the like as a rolling element is in contact with the outer peripheral surface 1A. Further, the rolling bearing inner ring 1 rolls with respect to the shaft or the like so that the shaft or the like penetrating the inner peripheral portion of the rolling bearing inner ring 1 comes into contact with the shaft and the rolling bearing inner ring 1 can rotate integrally. An inner peripheral surface 1B for fixing the bearing inner ring 1 is provided.

And the rolling bearing inner ring | wheel 1 is hardened by the induction hardening method in Embodiment 1 demonstrated below, and is produced. Therefore, the rolling region 1D including the rolling surface 1C as the stress applying portion is heated to a high-temperature quenching temperature that is a temperature equal to or higher than A ₁ and is a quenching control portion that is a portion other than the stress applying portion. As the inner peripheral surface 1B is heated to a low-temperature quenching temperature lower than the above-mentioned high-temperature quenching temperature at a temperature equal to or higher than A ₁ point, it is quenched by cooling to a temperature below the _MS point. It is cured. As a result, the rolling region 1D has a higher solute carbon concentration than other regions of the rolling bearing inner ring 1. Therefore, compressive stress is applied to the rolling surface 1C, and the rolling bearing inner ring 1 is hardened and hardened as a whole. Therefore, the rolling bearing inner ring 1 has high strength and long life even under harsh environments while suppressing an increase in manufacturing cost.

  In order to make the rolling bearing inner ring 1 have higher strength and longer life, the region to which the compressive stress is applied is preferably not only the surface but also a region having a certain depth. The depth of the running region 1D from the rolling surface 1C is preferably 1/20 or more of the wall thickness (thickness in a plane perpendicular to the rolling surface 1C). On the other hand, when the depth of the rolling region 1D exceeds 1/3 of the wall thickness, the tensile stress generated in the inner peripheral surface 1B is increased to balance the compressive stress generated in the rolling region 1D, and the inner peripheral surface 1B There is a risk that the strength falls below the allowable range. Therefore, the depth of the rolling region is preferably 1/3 or less of the wall thickness.

  Next, the induction hardening equipment in Embodiment 1 which is one embodiment of the present invention will be described. FIG. 2 is a schematic diagram showing the configuration of the induction hardening equipment in the first embodiment. With reference to FIG. 2, the structure of the induction hardening equipment in Embodiment 1 of this invention is demonstrated.

  With reference to FIG. 2, the induction hardening equipment 90 in Embodiment 1 is a high frequency used in an induction hardening method in which the entire rolling bearing inner ring 1 as an object to be processed is heated and hardened by induction heating. Quenching equipment. The induction hardening equipment 90 includes a temperature control device 50 for adjusting the temperature of the rolling bearing inner ring 1 and a quenching control device 60 for adjusting the timing at which the heated rolling bearing inner ring 1 should be cooled. I have.

  The temperature control device 50 acquires temperature data of the rolling bearing inner ring 1 and outputs a temperature information based on the temperature data of the rolling bearing inner ring 1. A temperature controller 4 connected to the radiation thermometer 3 and outputting a temperature control signal for controlling the heating state of the rolling bearing inner ring 1 based on the temperature information from the first radiation thermometer 3, and the temperature controller 4 And a heating device 2 that heats the rolling bearing inner ring 1 by high-frequency heating based on a temperature control signal from the temperature control device 4. The induction coil included in the heating device 2 is disposed so as to surround the outer peripheral side of the rolling bearing inner ring 1.

  The quenching control device 60 includes a first radiation thermometer 3 and a second radiation thermometer 5, a cooling timing adjusting device 6, and a cooling device 7 as temperature measuring devices for quenching. A first radiation thermometer 3 and a second radiation thermometer 5 as temperature measuring devices for quenching are a rolling surface 1C (surface facing the induction coil) and a quenching control unit which are stress applying portions of the rolling bearing inner ring 1. Each of the inner peripheral surface 1B (the surface on the back side of the surface facing the induction coil) is acquired, and temperature information based on the temperature data of the rolling bearing inner ring 1 is output. The cooling timing adjusting device 6 is connected to the first radiation thermometer 3 and the second radiation thermometer 5, and based on the temperature information from the first radiation thermometer 3 and the second radiation thermometer 5, the rolling surface 1 </ b> C is The heating time is adjusted so that the inner peripheral surface 1B is heated to the low-temperature quenching temperature while being heated to the high-temperature quenching temperature, the timing at which the rolling bearing inner ring 1 should be cooled is determined, and the cooling start signal is output. It has a function. The cooling device 7 is connected to the cooling timing adjusting device 6 and has a function of quenching and hardening the rolling bearing inner ring 1 by cooling the rolling bearing inner ring 1 based on a cooling start signal. The cooling device 7 is a quenching liquid jetting device that cools, for example, by spraying a cooling liquid onto the rolling bearing inner ring 1.

  Here, the first radiation thermometer 3 is installed as both a temperature measuring device for temperature control and a temperature measuring device for quenching control. In addition, the temperature adjustment device 4 and the cooling timing adjustment device 6 are each a personal computer, for example, and one personal computer may serve as both the temperature adjustment device 4 and the cooling timing adjustment device 6.

  The type of the temperature measuring device used for the temperature control temperature measuring device and the quenching temperature measuring device may be a radiation thermometer as described above, but if it is possible in the layout of the device, it is a contact type such as a thermocouple. A thermometer may be used.

  Next, the induction hardening method in Embodiment 1 which is one embodiment of the present invention using the above-described induction hardening equipment will be described. FIG. 3 is a diagram showing an outline of the induction hardening method according to the first embodiment which is one embodiment of the present invention.

Referring to FIGS. 2 and 3, induction hardening process 10 in the present embodiment, the object to be treated by high-frequency heating M _S point from the temperature of the _one or more point A by heating the whole (the rolling bearing inner ring 1) This is an induction hardening method in which the rolling bearing inner ring 1 is quenched and hardened by cooling to the following temperature. The induction hardening method 10 includes a temperature control step 20 in which the temperature of the rolling bearing inner ring 1 is adjusted, and a rolling surface 1C as a stress applying portion that is a portion to which compressive stress is to be applied in the rolling bearing inner ring 1 is A _1. are heated to a high temperature quenching temperature is a temperature above the point, and the inner peripheral surface 1B of the quenching controller is a temperature not lower than a ₁ point, which is a portion other than the rolling contact surface 1C, the high temperature hardening A quench control step 30 for cooling the rolling bearing inner ring 1 to a temperature not higher than the M _S point from a state where it is heated to a low-temperature quenching temperature that is lower than the temperature.

  And the temperature control process 20 is based on the temperature measurement temperature measurement process 23 in which the temperature of the rolling bearing inner ring 1 is measured and the temperature information measured in the temperature control temperature measurement process 23. The temperature control process 24 in which the temperature control signal for controlling a state is output, and the heating process 22 in which the rolling bearing inner ring | wheel 1 is heated by high frequency heating based on a temperature control signal are included.

  The quenching control process 30 includes a quenching temperature measurement process 35, a cooling timing adjustment process 36, and a cooling process 37. In the quenching temperature measurement step 35, the temperatures of the rolling surface 1C and the inner peripheral surface 1B of the rolling bearing inner ring 1 are measured. In the cooling timing adjustment step 36, the rolling surface 1C is heated to the high-temperature quenching temperature and the inner peripheral surface 1B is heated to the low-temperature quenching temperature based on the temperature information measured in the quenching temperature measurement step 35. The heating time is adjusted so that the timing at which the rolling bearing inner ring 1 should be cooled is determined, and a cooling start signal is output. In the cooling step 37, the rolling bearing inner ring 1 is quenched and hardened by cooling the rolling bearing inner ring 1 based on the cooling start signal.

The solid solution carbon concentration on the rolling surface 1C is obtained by quenching and hardening the rolling bearing inner ring 1 as an object to be processed by the induction hardening method 10 in the first embodiment using the induction hardening equipment 90 in the first embodiment. Becomes relatively higher than other parts. As a result, rolling the contact surface 1C compressive stress is applied, thereby improving the fatigue strength, the rolling surface part other than 1C also, quenching is cooled from a temperature of more than ₁ point A to M _S point below the temperature Since it is cured, sufficient strength is ensured. As a result, the rolling bearing inner ring 1 can have high strength and a long life.

  Furthermore, the induction hardening method according to the first embodiment does not employ a heat treatment method including carburizing and quenching with a long treatment time or other complicated heat treatment steps, so that the above-described excellent characteristics can be achieved while suppressing manufacturing costs. Can be applied to the rolling bearing inner ring 1. Further, by using high frequency heating for heating the rolling bearing inner ring 1, the rolling bearing inner ring 1 can be easily rolled at a part close to the induction coil (rolling surface 1C) and a part far away (inner peripheral surface 1B). The temperature of the inner ring 1 can be changed.

  Furthermore, in the temperature control process 20, the temperature data of the rolling bearing inner ring 1 is fed back in real time to heat the rolling bearing inner ring 1 to a desired temperature, and in the quenching control process 30, the rolling surface 1C and the inner circumference are heated. Information on both temperatures of the surface 1B is acquired in real time, and based on this, the timing of cooling can be determined, and the rolling bearing inner ring 1 can be hardened and hardened. Therefore, it becomes easy to adjust the heating time so that the rolling surface 1C is heated to the high-temperature quenching temperature and the inner peripheral surface 1B is heated to the low-temperature quenching temperature.

  From the above, according to the induction hardening method in the first embodiment, there is provided an induction hardening method capable of increasing the strength and extending the life of the rolling bearing inner ring 1 while suppressing an increase in manufacturing cost. Can do.

Note that the _point A when heated steel refers to a point that the structure of the steel corresponds to the temperature to start the transformation from ferrite to austenite. Further, the M _S point when the steel was austenitized is cooled, it refers to a point corresponding to a temperature to initiate the martensite.

(Embodiment 2)
Next, an induction hardening method, induction hardening equipment, and a mechanical member (rolling member) according to Embodiment 2, which is an embodiment of the present invention, will be described. The induction hardening method, induction hardening equipment and mechanical member (rolling member) in the second embodiment are basically the induction hardening method, induction hardening equipment and mechanical member (rolling member) in the first embodiment. It has the same composition as.

  However, the induction hardening method in the second embodiment is different from the first embodiment in the induction control equipment 30 in the induction control process 30 and in the induction control apparatus 60. Further, the rolling bearing inner ring 1 as the mechanical member (rolling member) in the second embodiment is different from the rolling bearing inner ring 1 in the first embodiment due to this.

  That is, in the induction hardening equipment 90 according to the second embodiment, the cooling timing adjusting device 6 of the quenching control device 60 is connected to the first radiation thermometer 3 and the second radiation thermometer 5, and the first radiation thermometer. 3 and the temperature information from the second radiation thermometer 5, the rolling surface 1C is heated to the quenching temperature, and the inner peripheral surface 1B is heated to the quenching temperature for a shorter time than the rolling surface 1C. Thus, the heating time is adjusted, the timing at which the rolling bearing inner ring 1 should be cooled is determined, and the cooling start signal is output. Moreover, in the induction hardening method 10 in Embodiment 2, in the cooling timing determination process 36 of the quench control process 30, based on the temperature information measured in the quenching temperature measurement process 35, the rolling surface 1C is formed. The heating time is adjusted so that the inner circumferential surface 1B is heated to the quenching temperature and heated to the quenching temperature for a shorter time than the rolling surface 1C, and the timing at which the rolling bearing inner ring 1 should be cooled is determined. Then, a cooling start signal is output.

The solid solution carbon concentration on the rolling surface 1C is obtained by quenching and hardening the rolling bearing inner ring 1 as an object to be processed by the induction hardening method 10 in the embodiment 2 using the induction hardening equipment 90 in the embodiment 2. Becomes relatively higher than other parts. As a result, rolling the contact surface 1C compressive stress is applied, thereby improving the fatigue strength, the rolling surface part other than 1C also, quenching is cooled from a temperature of more than ₁ point A to M _S point below the temperature Since it is cured, sufficient strength is ensured. As a result, the rolling bearing inner ring 1 can have high strength and a long life.

  Furthermore, since the induction hardening method in Embodiment 2 does not employ a heat treatment method including carburizing and quenching with a long treatment time or other complicated heat treatment steps, the above excellent characteristics can be achieved while suppressing manufacturing costs. Can be applied to the rolling bearing inner ring 1. In addition, by using high-frequency heating for heating the rolling bearing inner ring 1, the quenching temperature can be increased between the part close to the induction coil (rolling surface 1 </ b> C) and the part far away (inner peripheral surface 1 </ b> B) of the rolling bearing inner ring 1. It becomes easy to change the holding time.

  Furthermore, in the temperature control process 20, the temperature data of the rolling bearing inner ring 1 is fed back in real time to heat the rolling bearing inner ring 1 to a desired temperature, and in the quenching control process 30, the rolling surface 1C and the inner circumference are heated. Information on both temperatures of the surface 1B is acquired in real time, and based on this, the timing of cooling can be determined, and the rolling bearing inner ring 1 can be hardened and hardened. Therefore, the heating time can be adjusted so that the rolling surface 1C is heated to the quenching temperature for a desired time and the inner peripheral surface 1B is heated to the quenching temperature for a shorter time than the rolling surface 1C. It becomes easy.

  As described above, by implementing the induction hardening method in Embodiment 2 using the induction hardening equipment in Embodiment 2, the rolling bearing inner ring 1 is increased in strength and extended in life while suppressing an increase in manufacturing cost. be able to.

  Examples of the present invention will be described below. Even when the steel constituting the mechanical member is, for example, a bearing steel such as JIS SUJ2 or a carbon steel such as JIS S53C, the induction hardening method of the present invention can be applied effectively, but 3% by mass. In the case of steel containing the above chromium (for example, AISI M50, JIS SKH4, JIS SUS440C, JIS SUS420J2, etc.), since the heating temperature during quenching becomes high (for example, 1000 ° C. or higher), induction hardening of the present invention is performed. The method is easy to control and suitable for application.

  In this example, AISI M50 was adopted as a material, and a test for confirming the effect of the induction hardening method of the present invention was performed. The test method will be described below.

  As an example of the present invention, a ring-shaped test piece having an outer diameter of φ60 mm, an inner diameter of φ45 mm, and a width of t15 mm was produced from a steel material of AISI M50, and then quenched and hardened by the method of the second embodiment. The stress applying portion was the outer peripheral surface, and the quenching control portion was the inner peripheral surface. The heating temperature was 1150 ° C. for both the outer peripheral surface and the inner peripheral surface, and the time after reaching 1150 ° C. was changed to three levels for quenching.

  On the other hand, as a comparative example, a ring-shaped test piece having an outer diameter of φ60 mm, an inner diameter of φ45 mm, and a width of t15 mm was produced from a steel material of AISI M50 as in the above example, and then held at 1110 ° C. in an atmosphere furnace for 600 seconds and then rapidly cooled. Thus, a test piece subjected to quenching was also produced.

  And the test to investigate the rolling fatigue life of the ring-shaped specimen when the hardness of the outer peripheral surface and the inner peripheral surface, the compressive stress of the outer peripheral surface, the hardness distribution from the outer peripheral surface to the inner peripheral surface and the shaft is press-fitted Carried out.

  Next, the test method will be described. Regarding the hardness of the outer peripheral surface and the inner peripheral surface, the hardness of the outer peripheral surface and the inner peripheral surface was measured with a Rockwell hardness meter. The compressive stress of the outer peripheral surface was measured by a stress parallel to the circumferential direction using an X-ray stress measuring device. The hardness distribution is determined by cutting a hardened and hardened ring-shaped test piece along a surface perpendicular to the outer peripheral surface and using a Vickers hardness tester to measure the hardness in the direction perpendicular to the outer peripheral surface from directly under the outer peripheral surface toward the inner peripheral surface. To investigate. Furthermore, the rolling fatigue life of the ring-shaped test piece when the shaft was press-fitted was investigated as follows.

  FIG. 4 is a schematic diagram showing the configuration of a ring rotation fatigue tester used for investigating the rolling fatigue life of a ring-shaped test piece when a shaft is press-fitted. A method for investigating the rolling fatigue life of the ring-shaped test piece will be described with reference to FIG.

  With reference to FIG. 4, the ring rotation fatigue testing machine 70 includes a drive roll 73 having a cylindrical shape, a load roll 72, and a guide roll 75. The drive roll 73, the load roll 72, and the guide roll 75 are arranged so that the rotation axes are parallel and the outer peripheral surface can contact the ring-shaped test piece 71. The ring rotation fatigue testing machine 70 further includes an oil supply nozzle 74, and the oil supply nozzle 74 can supply lubricating oil to the test piece 71.

  In the rolling fatigue life test, a ring-shaped test piece 71 having a shaft 76 press-fitted on the inner periphery is set so as to come into contact with the drive roll 73, the load roll 72, and the guide roll 75 on the outer peripheral surface. This was implemented by being driven by the rotation of the drive roll 73 and being guided by the guide roll 75 and rotating while being subjected to stress compressed in the radial direction by the roll 72. And the time until a crack generate | occur | produces in an outer peripheral surface was investigated, and the said time was made into the rolling fatigue life. The test piece had an outer diameter of 60 mm, an inner diameter of 45 mm, a width of t15 mm, a load of 107.8 kN, a rotation speed of 4000 rpm, and the lubricating oil was turbine oil VG68. In addition, the press-fit shafts were two levels of 80 μm and 120 μm thick with respect to an inner diameter of 45 mm, and as a result, the fitting stress on the outer peripheral surface of the ring-shaped test piece 71 was two levels of 200 MPa and 310 MPa, respectively. Two tests were performed for each axis.

  Next, the results of the above test will be described. Table 1 is a table showing the hardness of the outer peripheral surface and the inner peripheral surface and the compressive stress of the outer peripheral surface of the examples and comparative examples of the present invention, together with the quenching conditions of each test piece. With reference to Table 1, the hardness of the outer peripheral surface of Examples A to C was 61 to 61.5 HRC, and the hardness of the outer peripheral surface of the comparative example was 61.5 HRC, which was almost the same hardness. On the other hand, the hardness of the inner peripheral surface is higher as the heating time is longer, but even Example A, which has the lowest hardness, has a hardness of 52 HRC or more, and is as severe as being used as a rolling surface. Unless it is used under the proper conditions, the hardness is sufficient. Also, the larger the ratio of the heating time of the outer peripheral surface to the heating time of the inner peripheral surface, the greater the compressive stress of the outer peripheral surface, and in the comparative example where the heating time of the inner peripheral surface and the outer peripheral surface is the same, compression The stress was zero.

  FIG. 5 is a diagram showing the measurement results of the hardness distribution in the direction perpendicular to the outer peripheral surface from directly below the outer peripheral surface to the inner peripheral surface of the ring-shaped test piece of Example A. In FIG. 5, the horizontal axis represents the depth from the outer peripheral surface, and the vertical axis represents the hardness. With reference to FIG. 5, the hardness distribution of the ring-shaped test piece will be described.

  Referring to FIG. 5, the test piece of Example A having the largest hardness difference between the inner peripheral surface and the outer peripheral surface was also hardened by a general induction hardening method in which only the surface layer portion was hardened and hardened. In the member, the region where the hardness formed immediately below the surface is not rapidly decreased, but rather has a hardness distribution close to that of a carburized and quenched member in which the hardness gradually decreases. From this, it can be seen that in the mechanical member quenched and hardened by the induction hardening method of the present invention, when a large load is applied, internal cracks occurring in a region where the hardness sharply decreases are suppressed.

  Tables 2 and 3 are tables showing the results of the rolling fatigue life test when the fitting stress on the outer peripheral surface is 200 MPa and 310 MPa, respectively, together with the magnitude of the compressive stress applied to the outer peripheral surface.

  With reference to Table 2, when the fitting stress of an outer peripheral surface is 200 MPa, it turns out that the lifetime becomes long, so that the compressive stress of an outer peripheral surface is large. And the lifetime of the Example of this invention is 3 times or more of the lifetime of a comparative example. Here, “> 300” in the table indicates that the test was stopped without cracking on the outer peripheral surface even after 300 hours had elapsed from the start of the test.

  Referring to Table 3, when the fitting stress on the outer peripheral surface is 310 MPa, the life is reduced as a whole as compared with the case of Table 2 as the fitting stress on the outer peripheral surface is increased. However, even in this case, the life of the example of the present invention is more than three times the life of the comparative example.

  As described above, the mechanical member quenched and hardened by the induction hardening method of the present invention does not have a sharp decrease in hardness inside the member, and has a sufficient hardness in the entire member. Therefore, it was found that even when a large load is applied, the occurrence of internal cracks and plastic deformation inside the member are suppressed. In addition, since the mechanical member quenched and hardened by the induction hardening method of the present invention can apply a sufficiently large compressive stress to a desired portion of the surface, for example, the fit is large, and the tensile stress is applied to the surface. It has been found that even when used in an environment in which the above works, the machine member has a long life.

  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 induction hardening method, the mechanical member and the rolling member of the present invention are an induction hardening method in which an object to be processed is quenched by induction heating, a mechanical member and a rolling member produced by performing the quenching. Can be applied particularly advantageously.

FIG. 3 is a schematic cross-sectional view showing a configuration of a rolling bearing inner ring as a mechanical member (rolling member) in the first embodiment. It is the schematic which shows the structure of the induction hardening equipment in Embodiment 1. FIG. It is a figure which shows the outline of the induction hardening method in Embodiment 1. FIG. It is the schematic which shows the structure of the ring rotation fatigue testing machine used in order to investigate the rolling fatigue life of the ring-shaped test piece at the time of press-fitting a shaft. It is a figure which shows the measurement result of the hardness distribution in the direction perpendicular | vertical to the outer peripheral surface from the directly outer peripheral surface of the ring-shaped test piece of Example A toward an inner peripheral surface.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Rolling bearing inner ring, 1A outer peripheral surface, 1B inner peripheral surface, 1C rolling surface, 1D rolling area, 2 Heating device, 3 1st radiation thermometer, 4 Temperature control device, 5 2nd radiation thermometer, 6 Cooling timing Control device, 7 Cooling device, 10 Induction hardening method, 20 Temperature control process, 22 Heating process, 23 Temperature control process for temperature control, 24 Temperature control process, 30 Quenching control process, 35 Temperature measurement process for quenching, 36 Cooling timing determination process, 50 temperature control device, 60 quenching control device, 70 ring rotation fatigue tester, 71 ring-shaped test piece, 72 load roll, 73 drive roll, 74 oil supply nozzle, 75 guide roll, 76 axis, 90 high frequency Quenching equipment.

Claims (7)

An induction hardening method in which the whole object to be treated is hardened and hardened by heating the whole object by high frequency heating and cooling from a temperature of A ₁ point or more to a temperature of M _S point or less,
A temperature control step in which the temperature of the workpiece is adjusted;
In the object to be processed, a stress applying part which is a part to which compressive stress including the surface of the object to be processed is applied is heated to a high-temperature quenching temperature which is a temperature of A ₁ point or more, and the stress applying part site der except is, the quenching controller including the surface of the object to be treated is at a temperature of more than ₁ point a, and is heated to a low temperature quenching temperature is a temperature lower than the hot quenching temperature An induction hardening method comprising: a quenching control step of quenching and hardening the entire workpiece by cooling the workpiece to a temperature equal to or lower than the _MS point from the state. The temperature control step includes
A temperature control temperature measurement step in which the temperature of the object to be processed is measured,
Based on the temperature information measured in the temperature control temperature measurement step, a temperature adjustment step for outputting a temperature control signal for controlling the heating state of the workpiece,
A heating step in which the object to be processed is heated by the high-frequency heating based on the temperature control signal,
The quench control process includes
A quenching temperature measurement step in which the temperature of the stress applying portion and the quenching control portion of the workpiece is measured,
Based on the temperature information measured in the quenching temperature measurement step, the stress applying part is heated to the high-temperature quenching temperature, and the quenching control part is heated to the low-temperature quenching temperature. A cooling timing adjustment step in which time is adjusted, a timing at which the workpiece is to be cooled is determined, and a cooling start signal is output;
The induction hardening method of Claim 1 including the cooling process in which the said to-be-processed object is quench-hardened by cooling the said to-be-processed object based on the said cooling start signal. An induction hardening method in which the whole object to be treated is hardened and hardened by heating the whole object by high frequency heating and cooling from a temperature of A ₁ point or more to a temperature of M _S point or less,
A temperature control step in which the temperature of the workpiece is adjusted;
In the object to be processed, a stress applying part which is a part to which compressive stress including the surface of the object to be processed is applied is heated to a quenching temperature which is a temperature of A ₁ point or more, and other than the stress applying part sites der of is, the shorter time than the quenching controller said stress applying portion including the surface of the object, from a state which is heated to the quenching temperature, the treatment object M _S following point An induction quenching method comprising: a quenching control step of quenching and hardening the entire workpiece by cooling to a temperature. The temperature control step includes
A temperature control temperature measurement step in which the temperature of the object to be processed is measured,
Based on the temperature information measured in the temperature control temperature measurement step, a temperature adjustment step for outputting a temperature control signal for controlling the heating state of the workpiece,
A heating step in which the object to be processed is heated by the high-frequency heating based on the temperature control signal,
The quench control process includes
A quenching temperature measurement step in which the temperature of the stress applying portion and the quenching control portion of the workpiece is measured,
Based on the temperature information measured in the quenching temperature measurement step, the stress applying unit is heated to the quenching temperature, and the quenching control unit is shorter than the stress applying unit at the quenching temperature. A cooling timing adjustment step in which a heating time is adjusted so that the workpiece is heated, a timing at which the workpiece is to be cooled is determined, and a cooling start signal is output;
The induction hardening method of Claim 3 including the cooling process by which the said to-be-processed object is quench-hardened by cooling the said to-be-processed object based on the said cooling start signal.   A mechanical member produced by quenching and hardening by the induction hardening method according to any one of claims 1 to 4.   A rolling member produced by quench hardening by the induction hardening method according to any one of claims 1 to 4.   The manufacturing method of a mechanical member provided with the process of quench-hardening with the induction hardening method of any one of Claims 1-4.

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