JP2007131938A - Induction hardening device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction hardening device capable of reliably preventing occurrence of scales and rough surface without using any quartz tube having possibility of problem in durability, and enhancing the heat treatment quality. <P>SOLUTION: The induction hardening device M comprises a chamber 11 for maintaining its inside in an airtight manner while a work W as a material to be hardened is set inside, inert gas atmosphere forming means 13, 14, 15, 20 for substituting the atmosphere in the chamber 11 with inert gas, an inert gas blowing means 16 equipped in the chamber 11 for substituting the surface of the work W with inert gas by blowing the inert gas to the work W, an induction heating coil 12 equipped in the chamber 11 to heat the work W, a water spraying means 17 equipped in the chamber 11 to spray hardening water on the heated work W to cool the work, and a deaerator 32 for deaerating hardening water to be sprayed by the water spraying means 17. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an induction hardening apparatus suitable for induction hardening of a workpiece having a complicated surface shape such as a ball screw shaft.

  In general, the induction hardening apparatus includes an induction heating coil and a cooling means. An induction current is generated in the work placed in the coil by flowing an induction current through the induction heating coil, and then heated by the cooling means. It is rapidly cooled to quench and harden the surface layer of the workpiece.

  In such an induction hardening apparatus, the surface of the workpiece is violently oxidized during heating by the induction heating coil and between cooling and cooling by the cooling means, resulting in scale and rough skin. There's a problem. Once scale is generated on the surface of the workpiece, it must be removed by buffing in the subsequent process, which increases the burden on the subsequent process. In addition, once rough skin occurs, it is difficult to remove it by buffing, and there is a problem that the burden on the subsequent process is further increased. In particular, in a rolled ball screw shaft that does not grind the thread groove after quenching, there is a problem that if the scale or rough surface occurs, good rotation accuracy of the ball screw shaft cannot be obtained.

  Therefore, in this type of induction hardening apparatus, measures are usually taken to prevent oxidation, and one of the measures is to perform quenching in a chamber maintained in an inert gas atmosphere such as nitrogen gas. Is.

  The other is that the workpiece is surrounded by a quartz tube (non-magnetic tube) instead of the chamber, and the workpiece inside is heated by a high-frequency heating coil from the outside through the quartz tube. Immediately after the work is taken out, it is rapidly cooled by a cooling means (for example, see Patent Document 1).

  In the induction hardening apparatus 100 described in Patent Document 1, as shown in FIG. 2, the ball screw shaft 101 as a material to be hardened moves from the heating zone K toward the cooling zone R. In the heating zone K, a quartz tube 102 surrounding the ball screw shaft 101 is disposed, and a high-frequency heating coil 103 is provided on the outer periphery of the quartz tube 102. The cooling zone R is equipped with a cooler 104, and a shielding body 105 that shields the exit of the quartz tube 102 to the cooling zone R is disposed between the cooling zone R and the heating zone K.

  In addition, in the induction hardening apparatus 100 described in Patent Document 1, since the workpiece 101 is heated in the quartz tube 102 that is almost closed except for the inlet, convection of air around the workpiece 101 can be prevented, The amount of oxygen around the workpiece 101 can be extremely reduced. Therefore, even when the workpiece reaches a high temperature, the surface can be prevented from being oxidized, and the generation of scale and the like can be suppressed.

Japanese Patent No. 3057611

  By the way, in the case of a conventional apparatus for quenching inside a chamber maintained in an inert gas atmosphere, if the surface shape of the workpiece is very complicated like a ball screw shaft, it remains in details (local parts) such as screw grooves. There is a problem that the oxygen which is being removed cannot be sufficiently removed, and the quality of the heat treatment is deteriorated.

  In addition, in the induction hardening apparatus 100 described in Patent Document 1, it is necessary to immediately cool the workpiece 101 that comes out of the quartz tube 102, so the quartz tube 102 and the cooler 104 must be disposed close to each other, As a result, problems with the durability of the quartz tube 102 were likely to occur.

  Furthermore, in the induction hardening apparatus 100 described in Patent Document 1, the stage in which the quenching water is sprayed even when heated in a state with little oxygen due to the influence of dissolved oxygen contained in the quenching water that is the cooling liquid. There was a problem that a large amount of scale would occur.

  The present invention has been made to eliminate such inconveniences, and its purpose is to reliably prevent the occurrence of scale and rough skin without using a quartz tube that may cause problems in durability. An object of the present invention is to provide an induction hardening apparatus that can improve heat treatment quality.

The above object of the present invention can be achieved by the following constitution.
(1) A chamber capable of keeping the inside airtight with a work as a material to be hardened set therein, an inert gas atmosphere forming means for replacing the atmosphere in the chamber with an inert gas, and equipment provided in the chamber An inert gas spraying means for spraying an inert gas toward the workpiece to replace the surface of the workpiece with the inert gas, a high-frequency heating coil that is mounted in the chamber and heats the workpiece, and is mounted in the chamber An induction hardening apparatus comprising: water injection means for injecting quenching water onto a heated workpiece and cooling; and a deaeration device for degassing the quenching water injected by the water injection means.

  According to the induction hardening apparatus of the present invention, the interior of the chamber is maintained in an inert gas atmosphere, and further, an inert gas is blown toward the surface of the workpiece, so that oxygen in details such as screw grooves of the workpiece is reliably removed. Therefore, oxidation during heating can be prevented. Further, since the workpiece is cooled by spraying quenching water after heating in the same chamber, oxygen does not come into contact with the workpiece, so that oxidation of the workpiece can be reliably prevented. Furthermore, since the work is injected with degassed quenching water, the work can be reliably prevented from being oxidized by dissolved oxygen. Thereby, without using a quartz tube that may cause a problem in durability, the occurrence of scale and rough skin can be reliably prevented, and the quality of heat treatment can be improved.

Hereinafter, an embodiment of an induction hardening apparatus according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a partially cutaway perspective view for explaining a schematic configuration of an embodiment of an induction hardening apparatus according to the present invention.

  The induction hardening apparatus M of the present embodiment includes a chamber 11 that can hold a ball screw shaft (work) W as a material to be hardened in an airtight state and an atmosphere in the chamber 11 with an inert gas. An inert gas supply port 13 for replacement and an exhaust port 14 for exhausting internal air are provided so as to face the surface of the ball screw shaft W in the chamber 11, and the inert gas is supplied toward the ball screw shaft W. An inert gas spray nozzle device (inert gas spray means) 16 that sprays and replaces the surface of the ball screw shaft W with an inert gas; a high-frequency heating coil 12 that is provided in the chamber 11 and heats the ball screw shaft W; A water injection nozzle device (water injection means) 17 that is provided in the chamber 11 and injects quenching water onto the heated ball screw shaft W to cool it, and the water injection nozzle device 1. It is provided with degasser 32 for degassing quenching water for injection, a by.

  The chamber 11 is surrounded by a partition wall and is configured to be partially opened and closed. For example, the chamber 11 is configured to allow the ball screw shaft W to be taken in and out by opening and closing the upper wall portion. Yes. A work set unit 19 for setting the ball screw shaft W in a vertical posture is provided at the center of the chamber 11. The ball screw shaft W is stably held by the work set unit 19 by upper and lower rotating rods (not shown), and if necessary, around the axis as indicated by an arrow A (regardless of direction). Rotated. If the length is short, the ball screw shaft W may be fixedly held at a fixed position. If the length is long, the ball screw shaft W is moved in the axial direction (vertical direction) as necessary by operating the rotating rod. It is supposed to be made.

  The high-frequency heating coil 12 is disposed at a position surrounding a part of the periphery of the ball screw W held by the work set unit 19 by the rotating rod.

  Further, the water injection nozzle device 17 has a large number of injection nozzles that inject quenching water toward the surface of the ball screw shaft W held by the work set unit 19, and at a position that does not interfere with the high-frequency heating coil 12. Two are provided opposite to each other. The inert gas spray nozzle device 16 has a number of injection nozzles that inject inert gas toward the surface of the ball screw shaft W, which is also held by the work set unit 19, and includes the high-frequency heating coil 12 and water. It arrange | positions in the position which does not interfere with the injection nozzle apparatus 17. FIG.

  An inert gas supply port 13 for supplying an inert gas into the chamber 11 is open to the inside of the chamber 11 and is connected to an inert gas supply device 20 disposed outside the chamber 11. Further, the exhaust port 14 opens at a position away from the inert gas supply port 13 and is connected to the exhaust device 15. In this embodiment, the inert gas supply port 13, the inert gas supply device 20, the exhaust port 14, and the exhaust device 15 constitute an inert gas atmosphere forming means. An inert gas supply device 20 is also connected to an inert gas blowing nozzle device 16 which is an inert gas blowing means.

  The inert gas supply device 20 supplies an inert gas heating device 21 that heats an inert gas to be supplied to an appropriate temperature (about 40 to 60 ° C.) and an inert gas heated to an appropriate temperature. And an injection pump 22 which is fed into the nozzle 13 and the inert gas blowing nozzle device 16 to be injected into the chamber 11.

  Further, a quenching water circulation device 30 is connected to the water injection nozzle device 17 via a pipe 18, and this quenching water circulation device 30 sends the quenching water collected from the chamber 11 after injection again to the water injection nozzle device 17. A buffer tank 31 for storing the quenching water recovered from the chamber 11, a deaeration device 32 for removing dissolved oxygen contained in the quenching water, and a water jet nozzle device for removing the quenching water after degassing 17 and an injection pump 33 that injects the toner toward the ball screw shaft W. Here, soft water containing less mineral substances is used as quenching water. As the inert gas, a gas such as argon gas can be used, but nitrogen gas is used from the viewpoint of cost.

  Next, a procedure for quenching the ball screw shaft W using the induction hardening apparatus M of the present embodiment will be described.

  First, the ball screw shaft W is inserted into the chamber 11 and supported by the rotating rod, so that the ball screw shaft W is set on the work set unit 19. After the setting, the chamber 11 is sealed, the exhaust device 15 is operated, the residual air inside is exhausted, and an inert gas is introduced into the chamber 11 instead. That is, after exhausting the inside of the chamber 11, the inert gas (nitrogen gas) heated to an appropriate temperature (about 40 to 60 ° C.) by the inert gas heating device 21 is introduced into the chamber 11 from the inert gas supply port 13. Introducing the chamber 11 replaces the inside of the chamber 11 with an inert gas atmosphere. At the same time, the remaining inert gas is blown onto the surface of the ball screw shaft W from the inert gas blowing nozzle device 16, thereby efficiently removing oxygen remaining in details such as screw grooves on the surface of the ball screw shaft W. At this time, it is preferable to spray the inert gas while rotating the ball screw shaft W by the rotating rod.

  If the oxygen on the surface of the ball screw shaft W is removed by direct blowing of the inert gas in this way, the amount of gas used can be reduced as compared with the case where the gas is passively replaced with only the atmospheric gas. In addition, the time required for gas replacement can be shortened. In addition, spraying a large amount of inert gas that is not heated may significantly reduce the surface temperature of the ball screw shaft W and cause local instability in heat treatment quality, so it is preferable to spray a heated inert gas. .

  When the gas inside the chamber 11 and the surface of the ball screw shaft W is replaced with an inert gas, the high frequency heating coil 12 heats the ball screw shaft W at that stage. When the predetermined heating is completed, the high-frequency heating coil 12 is moved from the periphery of the ball screw shaft W, and the quenching water deaerated by the deaeration device 32 is sprayed from the water spray nozzle device 17 toward the surface of the ball screw shaft W. And quenching. Further, it is preferable to rotate the ball screw shaft W by the rotating rod also during the heating and water jetting.

  Therefore, according to the induction hardening apparatus M of the present embodiment, the inside of the chamber 11 is replaced with an inert gas atmosphere, and further, the heated inert gas is directly blown onto the surface of the ball screw shaft W. Since detailed oxygen can be reliably removed, oxidation during heating can be prevented. Further, since the ball screw shaft W is cooled by spraying quenching water after heating in the same chamber 11, oxygen does not contact the ball screw shaft W, so that the oxidation of the ball screw shaft W can be reliably prevented. Further, since the degassed quenching water is sprayed onto the surface of the ball screw shaft W, it is possible to reliably prevent oxidation of the ball screw shaft W due to dissolved oxygen. As a result, without using a quartz tube that may cause a problem in durability, it is possible to reliably prevent the occurrence of scale and rough skin, and to improve the quality of heat treatment. The scale down time can be shortened or reduced.

It is a partially cutaway perspective view for demonstrating schematic structure of one Embodiment of the induction hardening apparatus which concerns on this invention. It is sectional drawing for demonstrating the conventional induction hardening apparatus.

Explanation of symbols

M Induction hardening machine W Ball screw shaft (workpiece)
11 Chamber 12 High-frequency heating coil 13 Inert gas supply port (inert gas atmosphere forming means)
14 Exhaust port (inert gas atmosphere forming means)
15 Exhaust device (inert gas atmosphere forming means)
16 Inert gas spray nozzle device (inert gas spray means)
17 Water injection nozzle device (water injection means)
18 Pipe 19 Work set part 20 Inert gas supply device (inert gas atmosphere forming means)
21 Inert gas heating device 22 Injection pump 30 Quenched water circulation device 31 Buffer tank 32 Deaeration device 33 Injection pump

Claims (1)

A chamber capable of keeping the inside airtight in a state where a work as a material to be hardened is set inside,
An inert gas atmosphere forming means for replacing the atmosphere in the chamber with an inert gas;
An inert gas spraying means that is provided in the chamber and sprays an inert gas toward the workpiece to replace the surface of the workpiece with the inert gas;
A high-frequency heating coil mounted in the chamber for heating the workpiece;
Water injection means installed in the chamber and injecting quenching water onto the heated workpiece for cooling;
An induction hardening apparatus comprising: a deaeration device for degassing quenching water sprayed by the water spraying means.

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