JP6583714B2 - Induction hardening method - Google Patents

Description

  In the present invention, a work (mechanical part or structural part) such as an internal gear in which an area to be quenched and an area that is not desired to be quenched (hereinafter referred to as a quenching avoidance area) are mixed near the inner diameter portion. The present invention relates to an induction hardening method in which hardening is performed using an induction heating device.

  As a prior art of a high-frequency heating device that heats a pinion gear or the like, for example, one described in Patent Document 1 below is known.

  The high-frequency heating device disclosed in Patent Document 1 has a region to be heated and a region not to be heated on the outer periphery, and heats a work (object to be heated) such as a pinion gear in which the two regions are close to each other. In addition, a high-frequency coil that inserts a workpiece into the internal space and a non-ferrous metal ring that enters between the high-frequency coil and a region of the workpiece that is not to be heated are provided.

  The nonferrous metal ring generates a magnetic flux in the opposite direction to the magnetic flux generated by the eddy current flowing in the region to be heated when the high frequency coil is energized. This cancels and weakens the magnetic flux in the region that is not desired to be heated, and suppresses heating in that region.

JP 2002-343550 A

  Among the workpieces to be quenched using the high-frequency heating device, there is a workpiece 10 as shown in FIG. 3, that is, a cylindrical workpiece in which a region 11 to be quenched and a quenching avoidance region 12 are present close to the inner diameter portion. .

  The workpiece 10 is held and held by the chuck claw 5a or the like. In this state, as shown in FIG. 3, the high-frequency coil 2 is inserted inside the region 11 to be quenched, and the coil 11 is energized to heat the region 11 to be quenched to a required temperature (quenching temperature).

  At this time, in order to prevent the quenching avoidance region 12 from being heated to the quenching temperature, conventionally, the shape of the high frequency coil 2, the position of the high frequency coil 2 with respect to the workpiece 10, the output of the coil, the energization time, and the like are strictly managed. Was taken.

  However, in response to this, the quenching avoidance region 12 may be hardened due to slight variations in the quenching conditions such as the size of the workpiece 10, the shape of the high-frequency coil, the position of the coil relative to the workpiece 10, and the output.

  Then, the nonferrous metal piece as shown by patent document 1 was inserted in the quenching avoidance area | region 12, and the magnetic flux which generate | occur | produces in the quenching avoidance area | region 12 by the function of the piece was examined.

  However, depending on the size of the workpiece, a small-diameter pin (hereinafter referred to as a shield pin) having a diameter of less than 20 mm may be used as a non-ferrous metal piece for canceling the magnetic flux.

  The small-diameter shield pin is difficult to adopt an internal cooling structure from the viewpoint of space restrictions and securing a cross-sectional area.

  Even if a small-diameter shield pin that cannot be cooled internally is made of copper having a low electrical resistance, it will be distorted by overheating or damaged due to thermal deterioration if eddy currents flow repeatedly.

  For this reason, the use of shield pins has to be abandoned, especially when quenching small-sized workpieces that are mass-produced.

  It is an object of the present invention to employ a shield pin even in induction hardening of a small size work, and to reliably prevent the quenching avoidance area from being hardened while stably hardening the work area of the work. To do.

In the induction hardening method according to one aspect of the present invention, a high-frequency coil is inserted into a cylindrical workpiece in which a region to be quenched and a quenching avoidance region are mixed in the vicinity of the inner diameter portion. It is a method of quenching using a high-frequency heating device provided,
Inserting a shield pin made of non-ferrous metal that generates a magnetic flux in the opposite direction to the magnetic flux generated in the region to be quenched by energizing the high-frequency coil, inside the quenching avoidance region of the workpiece,
After the region to be quenched is heated to the quenching temperature by the high-frequency heating device, a cooling liquid is sprayed onto the workpiece, and the shield pin is simultaneously cooled every time one workpiece is quenched with the cooling fluid.

  According to the present invention, distortion and thermal degradation due to overheating of the shield pin are suppressed, and it is possible to quench the small size mass-produced product in a short cycle and to surely prevent the quenching avoidance region from being quenched. Become.

It is sectional drawing which shows the one aspect | mode of the high frequency heating apparatus utilized for implementation of this invention. It is sectional drawing which shows one form of the induction hardening method using the induction heating apparatus of FIG. It is explanatory drawing of the induction hardening by the conventional method of the workpiece | work which the area | region which should be hardened, and a quenching avoidance area | region exist close to an internal diameter part.

[Description of Embodiment of the Present Invention]
One aspect of the induction hardening method according to the present invention will be described below. The workpiece to be quenched by this method is a mixture of a region to be quenched and a quenching avoidance region in the vicinity of the inner diameter portion.

  The workpiece is, for example, an internal gear. The internal gear has the following structure, that is, an inner tooth to be hardened and a hole such as a shaft hole close to the inner tooth. Some holes do not want to be baked in order to reduce the attack force on the mating member inserted into the hole, and the inner diameter of the hole is smaller than the tip diameter of the inner tooth.

  The high frequency coil of the high frequency heating device is inserted inside the region to be quenched of the workpiece, and the region to be quenched is heated to the quenching temperature by energizing the high frequency coil.

  In addition, the heating by the high frequency coil is performed by previously providing a nonferrous metal shield pin that generates a magnetic flux in a direction opposite to the magnetic flux generated in the region to be quenched by energizing the high frequency coil, inside the quenching avoidance region of the workpiece. Insert and do.

  Next, when the region to be quenched is heated to the quenching temperature, a coolant is sprayed on the workpiece. Each time one workpiece is quenched with the coolant, the shield pin is also cooled at the same time.

  The coolant used at this time may be a polymer-containing water-soluble coolant used for the purpose of suppressing rapid cooling and preventing cooling cracking of the workpiece.

  The shield pin is preferably made of a material having good thermal conductivity and low electrical resistance, such as copper.

  According to this method, since the shield pin is cooled every time one workpiece is quenched, distortion and thermal deterioration due to overheating of the shield pin are reliably suppressed.

[Details of the embodiment of the present invention]
Specific examples of the induction hardening method according to one embodiment of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and it is intended that all the changes within the meaning and range equivalent to a claim are included.

  A specific example of the high-frequency heating device is shown in FIG. The high-frequency heating device 1 of FIG. 1 includes a high-frequency coil 2 held at a fixed position, a cooling liquid injection pipe 3 also held at a fixed position, and a lifting table 4 disposed immediately below the high-frequency coil 2. The workpiece holder 5 and the shield pin 6 installed on the lifting table 4 are provided.

  Two injection tubes 3 are provided in a centrally symmetrical arrangement obliquely above the high-frequency coil 2. The jet outlet of the injection tube 3 faces the direction of the high-frequency coil 2, from which the coolant is blown toward the high-frequency coil 2.

  The workpiece holder 5 shown in the figure is a scroll chuck made of carbon steel for machine structure (S45C). The workpiece holder 5 that grips the workpiece 10 with the chuck claws 5 a is installed on a workpiece placement surface (upper surface) 4 a of the lifting table 4.

  The shield pin 6 is a pin made of non-ferrous metal (it is made of copper) and is erected at the center of the workpiece placement surface 4a. Further, a waste liquid groove 4b through which the cooling liquid is allowed to escape is provided on the work placement surface 4a.

  The workpiece 10 to be quenched is placed on the lifting table 4 of the high-frequency heating apparatus 1 configured as described above so that the region 11 to be quenched is on the top and the quenching avoidance region 12 is on the bottom, and the workpiece 10 is mounted on the workpiece holder. Hold at 5.

  At this time, the shield pin 6 on the workpiece placement surface 4 a is allowed to enter the inside of the quenching avoidance region 12.

  When the work 10 is set on the work placement surface 4a, the lifting table 4 is raised to a predetermined position, and the high frequency coil 2 is introduced inside the region 11 to be hardened, as shown in FIG.

  Thereafter, the high-frequency coil 2 is energized, and the surface on the inner diameter side of the region 11 to be quenched is heated to a quenching temperature (for example, about 900 ° C.). The heating can be realized by energizing for several seconds (for example, about 5 seconds) although it depends on the output of the high frequency coil 2 and the like.

  When the region 11 to be quenched of the workpiece 10 is heated to a target temperature, the energization of the high-frequency coil 2 is stopped, the coolant is sprayed from the spray pipe 3, and the coolant is sprayed inside the workpiece 10 to be quenched. Cool the entire area of the inner diameter of the work including

  By the spraying, the shield pin 6 inserted inside the quenching avoidance region 12 of the workpiece is also cooled together.

  When the cooling by spraying the coolant is performed for a predetermined time (this may be several seconds), the lifting table 4 is lowered to the initial position, and the work held by the work holder 5 is released and the hardened work is taken out.

  According to this method, since the shield pin 6 is forcibly cooled every time one workpiece 10 is quenched, distortion and thermal deterioration of the shield pin 6 are suppressed.

  Further, by performing forced cooling, the quenching cycle (processing time per piece) can be shortened, and when the workpiece is a mass-produced product, the productivity can be improved.

  In the region 11 to be quenched, induction hardening of the spline of the iron-based sintered alloy cylindrical body having a spline having a groove bottom diameter d2 = φ22 mm and an inner diameter (tooth diameter) d1 = φ20 mm was performed by the method of the above embodiment.

  The cylindrical body has a shaft hole having an inner diameter d = φ18.7 mm that becomes the quenching avoidance region 12 on the side opposite to the spline forming portion. The separation distance from the spline forming part to the shaft hole is 1.5 to 2.0 mm.

  A high frequency coil having an outer diameter D1 = φ18.5 mm was inserted inside the spline of the cylindrical body, and a shield pin having an outer diameter D = φ16.7 mm was inserted into the shaft hole. The amount L of the shield pin entering the shaft hole is L = 2.4 mm.

  The high frequency coil used was one having an output of 95 to 96 A, a voltage of 250 V to 350 V, and a frequency of 100 kHz so that the bottom of the spline was sufficiently burned.

  The cylindrical body is heated with the high-frequency coil for about 5 seconds, and then the heated portion of the cylindrical body is cooled by spraying a water-soluble coolant containing a polymer as a cooling liquid. At the same time, the sprayed water-soluble cooling is performed. The shield pin was also cooled with the agent.

  As a result of investigating the state of the shield pin when the treatment was repeated 100,000 times, almost no distortion and thermal deterioration of the shield pin were observed.

DESCRIPTION OF SYMBOLS 1 High frequency heating apparatus 2 High frequency coil 3 Injection pipe 4 Lifting table 4a Workpiece mounting surface 4b Waste liquid groove 5 Work holder 5a Chuck claw 6 Shield pin 10 Workpiece 11 Region to be quenched 12 Quenching avoidance region

Claims (1)

Insert a cylindrical workpiece in which the inner diameter of the quenching avoidance region is smaller than the inner diameter of the region to be quenched, inside the region to be quenched, in which the region to be quenched and the quenching avoidance region are mixed close to the inner diameter portion. A method of quenching using a high-frequency heating device equipped with a high-frequency coil,
A magnetic flux in the direction opposite to the magnetic flux generated in the region to be quenched by energization of the high-frequency coil is placed inside the quenching avoidance region of the workpiece with the region to be quenched up and the quenching avoidance region in the downward direction. Insert a non-ferrous metal shield pin whose outer diameter (D) is smaller than the outer diameter (D1) of the high-frequency coil to be generated, the shield pin from the lower side of the work, and the high-frequency coil from the upper side of the work Each inserted from the inside of the workpiece,
After heating the region to be quenched with the high-frequency heating device to a quenching temperature, spray a coolant on the workpiece, and simultaneously cool the shield pin each time one workpiece is quenched with the coolant ,
As the high-frequency heating device, a high-frequency coil held at a fixed position, and a fixed position above the high-frequency coil so as to blow coolant from the obliquely upper side of the outer diameter side of the high-frequency coil toward the high-frequency coil. The held coolant injection pipe, the lifting table arranged immediately below the high frequency coil, the workpiece holder installed on the workpiece mounting surface of the lifting table , and the center of the workpiece mounting surface Using a device having the shield pin with a diameter of less than 20 mm ,
On the work placement surface of the lifting table, place the work in an orientation where the work should be quenched and the quenching avoidance area is down, and insert the shield pin inside the quenching avoidance area of the work, The elevating table is raised to a position where the high-frequency coil is inserted into the region to be quenched of the work held by the work holder, and at this position is heated by the high-frequency coil and a cooling liquid ejected from the injection pipe. cormorant row of cooling,
Induction hardening method.

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