JP2010209395A - Method and apparatus for improving surface stress of high frequency-induction hardened article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for improving the surface stress in a high frequency-induction hardened article by which the improvement of the surf stress at the hardening-boundary part can simply and effectively be performed and the occupancy space can be saed. <P>SOLUTION: The high frequency-induction hardening is performed with Joule-heat developed by flowing electric alternating current into a coil 2 wound around a heat-treatment portion of the article 1 to be heat-treated. Thereafter, low-speed water injecting-flow is injected from an injecting nozzle 4 arranged toward the hardening-boundary part 7 developed near the hardening part 6, and a cavitation injecting-flow 10 developed by injecting high-speed water injecting-flow into the low-speed water injecting-flow, is injected toward the hardening-boundary part. The surface stress is improved so that the hardening-boundary part 7 developed to a tension-stress by performing the high frequency-induction hardening, becomes the compress-stress with this cavitation injecting-flow 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for improving the surface stress of an induction-hardened product and a surface stress improving apparatus therefor.

  For example, in Patent Document 1, for the purpose of improving the fatigue strength of the fillet R portion of the nitrided crankshaft, it is generated by a high-pressure fluid and a low-pressure fluid injected from a high-pressure nozzle and a low-pressure nozzle surrounding the high-pressure nozzle. Cavitation peening is a surface stress improvement processing technology that applies compressed residual stress to a processed object by using the impact force when the cavitation bubbles collapse on the processed object surface. It is described to do.

  On the other hand, in the induction hardening treatment, the fatigue strength is improved by compressing the residual stress, but a boundary portion is generated near the quenched portion due to partial heating. Since the tensile boundary stress is given to the boundary portion, it becomes a starting point of fatigue failure.

  If the cavitation peening of Patent Document 1 is used to improve the surface stress of the boundary portion, the tensile residual stress in the boundary portion can be removed.

JP 2008-213067 A

  However, since it is necessary to carry out cavitation peening by carrying the work to a cavitation peening apparatus in a place different from the induction hardening apparatus after performing induction hardening as described in Patent Document 1, the setup is troublesome and The problem of requiring a lot of space remains.

  Accordingly, an object of the present invention is to provide a method for improving the surface stress of an induction-hardened product and a surface stress improving apparatus thereof that can easily improve the surface stress at the boundary portion and can be well-prepared and can be realized in a small space. .

  In the method of improving the surface stress of the induction-hardened product of the present invention, after heat-treating the heat-treated part of the heat-treated part, a low-speed water jet is introduced into the atmosphere from an injection nozzle disposed toward the quenching part generated in the vicinity of the quenching part. And a cavitation jet generated by jetting a high-speed water jet into the low-speed water jet.

  The apparatus for improving surface stress of an induction-hardened product according to the present invention is arranged with a low-pressure nozzle around the high-pressure nozzle, which is arranged toward a quenching portion generated in the vicinity of a quenching portion that is quenched by an induction hardening device. A cavitation peening device having an injection nozzle and injecting a cavitation jet formed by a low-speed water jet from the low-pressure nozzle and a high-speed water jet injected from the high-pressure nozzle at the center thereof is provided.

  According to the method of improving the surface stress of the induction-hardened product of the present invention, immediately after performing induction hardening, a cavitation jet is jetted from the jet nozzle arranged toward the quenching zone generated in the vicinity of the quenching portion. The boundary 7 that has become the tensile residual stress is improved to the compressive residual stress by the cavitation jet. Therefore, according to the method of the present invention, it is possible to speedily improve the surface stress at the burned-in portion and increase the fatigue strength.

  According to the surface stress improving apparatus for induction hardening of the present invention, since the injection nozzle of the cavitation peening apparatus is arranged toward the quenching part generated in the vicinity of the quenching part quenched by the induction hardening apparatus, induction hardening is performed. Then, the cavitation peening can be performed immediately after quenching without carrying out the troublesome setup of carrying the heat-treated part to another place and performing cavitation peening. Moreover, according to this invention, space saving can be carried out with respect to the system which arrange | positions an induction hardening apparatus and a cavitation peening apparatus independently in another place.

FIG. 1 is a diagram showing an example of improving the surface stress of a part to be heat-treated. FIG. 2 is a diagram showing an example of improving the surface stress of a connecting rod as a part to be heat treated. FIG. 3 is a diagram showing an example in which the surface of the fillet R portion of the crankshaft is improved as a heat-treated part. FIG. 4 is a diagram showing an example of improving the surface stress of a gear as a heat-treated part.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

“Embodiment 1”
FIG. 1 shows a surface stress improving method and apparatus for an induction hardened product in which surface stress is improved by performing cavitation peening after induction hardening is performed on a general heat-treated part. First, the surface stress improving apparatus will be described.

  The surface stress improving apparatus according to the first embodiment includes an induction hardening apparatus that performs induction hardening on the heat-treated component 1 and a cavitation peening apparatus.

  The induction hardening apparatus includes a coil 2 wound around a heat treatment part of the component 1 to be heat treated, and an AC current supply unit 3 for supplying an AC current to the coil 2. The alternating current supply unit 3 supplies the coil 2 with an alternating current having a predetermined strength according to the material of the heat-treated component 1. In this induction hardening apparatus, the heat treatment site is quenched by Joule heat generated by applying an alternating current to the coil 2.

  The cavitation peening apparatus includes an injection nozzle 4 that injects a cavitation jet toward a quenching portion that is generated in the vicinity of the quenching portion, and a fluid supply unit 5 that supplies fluid to the injection nozzle 4.

  The nozzle tip of the spray nozzle 4 is disposed toward the quenching zone 7 generated in the vicinity of the quenching zone 6 quenched by the induction hardening apparatus. The injection nozzle 4 includes a high-pressure nozzle 8 that injects a high-speed water jet and a low-pressure nozzle 9 that injects a low-speed water jet. The high-pressure nozzle 8 and the low-pressure nozzle 9 are arranged on a concentric axis, and are arranged so that the low-pressure nozzle 9 surrounds the periphery of the high-pressure nozzle 8 as a center.

  The fluid supply unit 5 supplies water, coolant, or a fluid containing a rust inhibitor to the high pressure nozzle 8 and the low pressure nozzle 9 at a predetermined pressure. High pressure water is supplied to the high pressure nozzle 8. Low pressure water lower than the high pressure water supplied to the high pressure nozzle 8 is supplied to the low pressure nozzle 9. The reason why the pressure has a height difference is to generate a cavitation jet.

  In this cavitation peening apparatus, when a high-speed water jet is jetted from the high-pressure nozzle 8 and a low-speed water jet is jetted from the low-pressure nozzle 9 provided around the high-pressure nozzle 8, the nozzle tip of the jet nozzle 4 The cavitation jet is jetted toward the burning boundary part 7 from. The cavitation jet here is assumed to be jetted directly into the atmosphere, not underwater.

  Next, a method for improving surface stress will be described. First, the coil 2 is wound around the heat treatment part of the heat treated part 1 made of a round bar or the like. Next, an alternating current is supplied from the alternating current supply unit 3 to the coil 2. Then, the coil 2 to which the alternating current is applied generates heat, and the heat treatment portion corresponding to the portion where the coil 2 is wound is heated and quenched by the generated Joule heat. In FIG. 1, the quenching part 6 is indicated by oblique lines.

  Next, high pressure water is supplied from the fluid supply unit 5 to the high pressure nozzle 8, and low pressure water is supplied to the low pressure nozzle 9. Then, a cavitation jet 10 is jetted from the jet nozzle 4 arranged toward the quenching zone 7 generated in the vicinity of the quenching zone 6. The quenching boundary portion 7 occurs at the boundary between the quenched part and the unheated part. Cavitation peening is a surface stress improvement technique that applies a compressive residual stress to the component 1 to be processed by using an impact force when bubbles contained in the cavitation jet 10 collapse on the surface of the component 1 to be processed.

  When the cavitation jet 10 is jetted toward the border 7, the compressive residual stress is applied to the border 7 to which the tensile residual stress is applied by induction hardening in response to the impact force at the time of bubble collapse. The surface stress of the boundary 7 is improved from the tensile residual stress to the compressive residual stress by receiving the jet of the cavitation jet 10. The fatigue strength of the boundary 7 is improved by improving the surface stress to compressive residual stress.

  As described above, according to the surface stress improving method of the first embodiment, immediately after performing induction hardening, a cavitation jet flows from the injection nozzle 4 disposed toward the quenching boundary 7 generated in the vicinity of the quenching section 6. Since 10 is injected, the boundary 7 that has become the tensile residual stress is improved by the cavitation jet 10 to the compressive residual stress. Therefore, according to the method of the present embodiment, the surface stress of the boundary 7 can be improved speedily and the fatigue strength can be increased.

  On the other hand, according to the surface stress improving apparatus of the first embodiment, the cavitation peening injection nozzle 4 is disposed toward the quenching part 7 generated in the vicinity of the quenching part 6 quenched by the induction hardening apparatus. Cavitation peening can be performed immediately after quenching without carrying out the troublesome preparation of carrying out cavitation peening by carrying the heat-treated part 1 to another place after quenching. Moreover, according to the apparatus of Embodiment 1, space saving can be carried out with respect to the system which arrange | positions an induction hardening apparatus and a cavitation peening apparatus independently in another place.

“Embodiment 2”
The second embodiment is an example in which a heat-treated part is a connecting rod, and a cavitation jet is sprayed aiming at a burning boundary portion of the connecting rod. As shown in FIG. 2, after performing induction hardening by the Joule heat which generate | occur | produces alternating current to the coil 2 wound around the heat processing part of the connecting rod 11, the injection nozzle arrange | positioned toward the quenching part produced | generated in the vicinity of a hardening part 4. Cavitation jet 10 is sprayed from 4.

  Specifically, the I section portion of the connecting rod 11 (the connecting portion portion in the form of a rod with the circular small end portion to which the piston is attached and the semicircular large end portion to which the crankshaft is attached) is connected to the inside of the coil 2. In the state where the coil 2 is inserted and disposed, the I section portion is induction-quenched by energization of the coil 2, and then the cavitation jet 10 is blown from the injection nozzle 4 to the boundary portion.

  In Embodiment 2, since the site | part which induction-hardens is wide, the injection nozzle 4 is arrange | positioned toward each of the two quenching boundary parts. Since the induction hardening apparatus and the cavitation peening apparatus according to the second embodiment have the same configuration as the apparatus according to the first embodiment, description thereof will be omitted.

  In the second embodiment, if the cavitation jet 10 is injected immediately after induction hardening of the connecting rod 11, the surface stress of the boundary portion that has been subjected to tensile compression can be improved to a compressive residual stress as in the first embodiment. , Fatigue strength can be increased.

“Embodiment 3”
The third embodiment is an example in which a heat treatment component is a crankshaft, and a cavitation jet is sprayed aiming at a fillet R portion that becomes a burned-in portion of the crankshaft 1. As shown in FIG. 3, after performing induction hardening by Joule heat that generates an alternating current on the coil 2 wound around the heat treatment portion of the crankshaft 12, in the boundary portion (fillet R portion) generated in the vicinity of the quenched portion. The cavitation jet 10 is sprayed from the jet nozzle 4 arranged so as to face.

  In the third embodiment, as in the second embodiment, the injection nozzles 4 are arranged toward the two fillet R portions, respectively. Since the induction hardening apparatus and the cavitation peening apparatus according to the third embodiment have the same configuration as the apparatus according to the first embodiment, the description thereof is omitted.

  In the third embodiment, if the cavitation jet 10 is blown immediately on the fillet R portion after induction hardening of the crankshaft 12, the surface stress of the boundary portion that has been subjected to tensile compression is compressed and retained as in the first and second embodiments. Stress can be improved, and fatigue strength can be increased. Moreover, according to Embodiment 3, the fillet roll process (process which presses and rolls a roller to a fillet R part) which removes a tensile residual stress becomes unnecessary, and therefore it is necessary to use a large-scale facility fillet roll processing apparatus. Disappear.

“Embodiment 4”
The fourth embodiment is an example in which a heat-treated part is a gear part and a cavitation jet is sprayed aiming at a tooth surface of the gear part. As shown in FIG. 4, the coil 2 wound around the heat treatment portion (tooth surface formed on the outer periphery) of the gear part 13 is induction-quenched by Joule heat that generates an alternating current, and then is generated near the quenched portion. A cavitation jet 10 is sprayed from the injection nozzle 4 arranged toward the border (tooth tip and tooth bottom).

  In the fourth embodiment, unlike the first to third embodiments, the coil 2 is arranged so as to cover the tooth surface of the gear component 13 attached to the rotating shaft 14 from the outer periphery. Further, in the fourth embodiment, as in the first embodiment, the injection nozzle 4 is arranged toward the tooth surface (tooth tip and tooth bottom). Since the cavitation peening apparatus according to the fourth embodiment has the same configuration as the apparatus according to the first embodiment, the description thereof will be omitted.

  In the fourth embodiment, after the gear part 13 is rotated and induction-hardened, the cavitation jet 10 is sprayed immediately on the tooth tip and the tooth bottom while the gear part 13 is also rotated. By carrying out like this, in Embodiment 4, the surface stress of the tooth tip and root which became tension compression can be improved into compression residual stress, and fatigue strength can be raised.

  The present invention can be used for a technique for improving the surface stress of an induction-hardened product by cavitation peening.

1 ... Heat-treated parts 2 ... Coils (high-frequency heat treatment equipment)
3… AC current supply unit (high frequency heat treatment equipment)
4 ... Injection nozzle (cavitation peening device)
5. Fluid supply part (cavitation peening device)
6 ... Quenching part 7 ... Quenching part 8 ... High pressure nozzle (jet nozzle)
9 ... Low pressure nozzle (jet nozzle)
10 ... Cavitation jet 11 ... Connecting rod (heat treated part)
12 ... Crankshaft (heat treated parts)
13. Gear parts (heat treated parts)

Claims (6)

After performing induction hardening by Joule heat generated by passing an alternating current through the coil wound around the heat treatment part of the heat treated part,
A cavitation jet generated by injecting a low-speed water jet into the atmosphere and injecting a high-speed water jet into the low-speed water jet from an injection nozzle arranged toward the quenching zone near the quenching section A method of improving the surface stress of an induction-hardened product, characterized by spraying on the part. A method for improving the surface stress of an induction-hardened product according to claim 1,
A method for improving the surface stress of an induction-hardened product, wherein the heat-treated part is a connecting rod, and a cavitation jet is blown toward the burned-out portion of the connecting rod. A method for improving the surface stress of an induction-hardened product according to claim 2,
A method for improving the surface stress of an induction-hardened product, characterized in that a cavitation jet is blown onto the quenching area in a state where the I section of the connecting rod is inserted and arranged inside the coil. A method for improving the surface stress of an induction-hardened product according to claim 1,
A method for improving the surface stress of an induction-hardened product, wherein the heat-treated component is a crankshaft and a cavitation jet is sprayed toward a fillet R portion of the crankshaft. A method for improving the surface stress of an induction-hardened product according to claim 1,
A method for improving the surface stress of an induction-hardened product, characterized in that the heat-treated component is a gear component and a cavitation jet is blown toward the tooth surface of the gear component. An induction hardening apparatus that has a coil wound around a heat treatment part of a part to be heat treated, and quenches the heat treatment part by Joule heat generated by applying an alternating current to the coil;
It has an injection nozzle that is arranged toward the quenching zone generated in the vicinity of the quenching section and surrounds the periphery of the high-pressure nozzle with a low-pressure nozzle, and the low-speed water jet from the low-pressure nozzle and the center An apparatus for improving the surface stress of an induction-hardened product, comprising a cavitation peening device for injecting a cavitation jet generated by a high-speed water jet injected from a high-pressure nozzle.

Images