JPH0533310B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal surface hardening device, and more specifically, a device for ejecting plasma gas from a first nozzle tip to melt the surface of a workpiece, and supplying powdered high-hardness metal to the melted part. A hardened layer with excellent wear resistance is formed on a predetermined portion of the workpiece, and a shielding gas is supplied from a second nozzle chip that surrounds the first nozzle chip in an electrically insulated state to harden the hard metal. The present invention relates to a metal surface hardening device which makes it possible to accurately inject the plasma gas onto the workpiece by preventing the plasma gas from adhering to the first nozzle tip and to avoid damage to the first nozzle tip.

Camshafts, rocker arms, and the like installed in automobiles must be used continuously over long periods of time, and therefore, it is particularly desirable that their sliding parts have extremely excellent wear resistance. For this reason,
Conventionally, various processing treatments have been applied to the camshaft, rocker arm, etc. in order to form a sliding contact portion with high hardness and excellent wear resistance.

For example, when casting and molding such camshafts, rocker arms, etc., a chiller is placed in the sliding contact area, and the supplied molten metal is rapidly cooled by the chiller to form a hardened chill layer. There is a way to do it. However, this cold metal does not provide sufficient hardness to the sliding contact portion, resulting in the inconvenience that products such as camshafts, rocker arms, etc. cannot be used for a long period of time.

Therefore, a method has been devised in which a high hardness metal such as Cr or Mo is added to the molten metal and a chilled metal is used to form a high hardness chill layer at the portion that will become the sliding contact part. However, in order to form a chill layer having a desired hardness using this type of Cr, Mo, etc., it is necessary to add a certain amount or more of the high hardness metal to the molten metal. Moreover, during the hardening process, a considerable amount of this high-hardness metal gets mixed into parts other than the sliding contact parts.
Therefore, the workpiece taken out after casting has a high hardness as a whole, and when it is attempted to finish the workpiece after molding, it is pointed out that cutting is difficult.

The present invention has been made to overcome the above-mentioned disadvantages, and includes a first nozzle chip that injects plasma gas, a second nozzle chip that surrounds the first nozzle chip in an electrically insulated state, and a second nozzle chip that surrounds the first nozzle chip in an electrically insulated state. and a shield cap that holds a tube for supplying powdered high-hardness metal, and sprays plasma gas onto the workpiece through the first and second nozzle tips to target a predetermined portion of the workpiece. The high-hardness metal is supplied while being melted to form a hardened layer with excellent wear resistance on the workpiece, and in particular, the high-hardness metal adheres to the first and second nozzle tips to generate a double arc. It is an object of the present invention to provide a metal surface hardening device that prevents the above-mentioned nozzle tip from being damaged, thereby making it possible to reliably inject a plasma arc onto a workpiece and avoid damage to the nozzle tip as much as possible.

In order to achieve the above object, the present invention comprises: a first nozzle chip having an electrode therein and defining a narrow nozzle opening for ejecting plasma gas; and a first nozzle chip that is electrically insulated from the first nozzle chip. a second nozzle chip that is maintained and surrounds the first nozzle chip to supply shielding gas to the tip of the first nozzle chip and has a cooling water opening formed therein; a shield cap that supplies shield gas toward the plasma gas; and a first hole and a second hole that are coaxially formed at a predetermined angle and are integral with the second nozzle tip and the shield cap. and a metal introduction tube which is fitted into the plasma gas and supplies high-hardness metal powder or granules toward the plasma gas.

Next, preferred embodiments of the metal surface hardening apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

1 and 2, reference numeral 10 indicates a metal surface hardening device according to the present invention. In this case, the device 10 includes a hollow shield cap 1.
2, and a first having a conical tip 14 at its lower end.
a nozzle tip 16; and the first nozzle tip 1.
6 and the shield cap 12 and defines a first passage 18 and a second passage 20 for shielding gas; High-hardness metal powder introduction tubes 24a, 2 held in
4b.

That is, the main body 26 that constitutes the device 10
The main body portion 26 has a substantially cylindrical shape, and a screw hole 28 is formed in the inner peripheral surface of the main body portion 26 . Then, the electrode 30 is disposed within the main body portion 26, and a threaded portion 32 formed at one end of the first nozzle tip 16 is screwed into the screw hole 28. A hole 34 for inserting the electrode 30 is formed in the center of the first nozzle chip 16, and a plasma gas deriving nozzle 36 with a smaller diameter is formed on the exit side of the hole 34 via a step.
are formed in communication. Furthermore, the first nozzle tip 1
An opening 38 is defined between the outer periphery of the main body 26 and the inner periphery of the main body 26, and cooling water is supplied to the opening 38. Note that it is preferable that a sealing O-ring 40 be interposed at the joint between the first nozzle tip 16 and the main body portion 26.

On the other hand, a shield gas ejection member 42 is fixed to the outer peripheral portion of the main body portion 26, and the ejection member 42 is fixed to the outer peripheral portion of the main body portion 26.
A passage 44 communicating with a shielding gas supply source (not shown) is formed inside 2. The ejection member 42
A step 46 is formed on the outer periphery of the nut member 50, and an insulator 48 is disposed in contact with the step 46, and one end of the nut member 50 is engaged with the insulator 48.
In this case, the insulator 48 is preferably made of a heat-resistant resin material such as ceramic or Teflon. Therefore, the second nozzle tip 22 and the shield cap 12 are integrally supported by the main body 26 via the nut member 50.

A threaded portion 52 that is screwed into the nut member 50 is formed at one end of the outer periphery of the second nozzle tip 22, and a relatively large diameter screw is formed in the center of the second nozzle tip 22 from the end side where the threaded portion 52 is provided. An opening 54 is formed and an insulator 56 is placed in the opening 54.
is interposed. Therefore, the second nozzle tip 2
2 and the ejection member 42 are electrically insulated via respective insulators 48 and 56. Further, the insulator 5
6, the ejection member 42, the main body portion 26, and the first nozzle tip 16 define a chamber 58, and this chamber 58 communicates with a shielding gas supply source (not shown) via the ejection member 42.

A cover member 59 formed to correspond to the shape of the outer circumferential surface of the first nozzle chip 16 is fixed to the inner peripheral part of the second nozzle chip 22, and a cooling water opening is provided between the cover member 59 and the second nozzle chip 22. A section 60 is defined. An insulator 62 is fitted and engaged with the inner peripheral portion of the cover member 59, and this insulator 6
2 and the first nozzle tip 16, a thin first
A passageway 18 is defined. One upper end of the first passage 18 communicates with the chamber 58, and the other lower end of the first passage 18 communicates with the nozzle portion 36 of the first nozzle tip 16.
The nozzle part 64 is coaxial with the nozzle part 36 and has a slightly larger diameter than the nozzle part 36 . Further, a plurality of passages 66 are formed in the second nozzle tip 22, one end of which communicates with the chamber 58 and the other end of which communicates with the second passage 20. On the other hand, holes 68a and 68b are bored at a predetermined angle.

On the other hand, the shield cap 12 is fixed to the outer peripheral end of the second nozzle tip 22, and the second passage 20 defined between the shield cap 12 and the second nozzle tip 22 is connected to the ejection member through the passage 66 and the chamber 58. 42 and communicates with a passage 44 . Holes 70a and 70 are provided in the shield cap 12 and are coaxial with the holes 68a and 68b of the second nozzle tip 22.
b, and the introduction pipes 24a, 24b are integrally fitted into the holes 68a, 70a and 68b, 70b. In this case, the second nozzle chip 22 and the shield cap 12 are made of Cr-Cu.
It is preferable to use a material with excellent wear resistance and thermal conductivity, such as an alloy.

The metal surface hardening device according to the present invention is basically constructed as described above, and its operation and effects will be explained next.

First, the device 10 is positioned near a portion of the workpiece W that will be a sliding contact portion, and then the electrode 30 is connected to the negative side of a DC power source (not shown), while the workpiece W is connected to the positive side. Further, a working gas such as argon gas is supplied to the hole 34, and a shielding gas is supplied to the blowout member 42 from a shielding gas supply source (not shown). Therefore, an arc is generated between the electrode 30 and the work W, and this plasma gas is constricted by the nozzle part 36 of the first nozzle chip 16 and is turned into a high-speed plasma arc from the tip part 14 to the second nozzle chip 22. It is led out to the outside via the nozzle section 64.

In this case, as shown in FIG.
The shielding gas supplied to the chamber 58 passes from the passage 44 to the chamber 58.
After being introduced into the shield gas, a part of the shielding gas enters the relatively thin first passage 18, and the other shielding gas passes through the second passage 20 via the plurality of passages 66, and enters the respective nozzle portions 36, 64. is blown onto a plasma arc derived from Therefore, the diameter of the plasma arc can be further reduced due to the convergence effect of the gas flow and the thermal pinch effect due to cooling by the shielding gas supplied from the circumferential direction, and the plasma arc can be applied to a desired portion of the workpiece W. This is effectively melted by injecting a high-temperature, high-speed plasma arc. As a result, it becomes possible to form a molten pool 72 in the workpiece W.

On the other hand, powdered high-hardness metal 74 is supplied into the plasma arc from the respective introduction pipes 24a and 24b. In this case, the high hardness metal 74 is
Various metals can be selected, such as single substances such as Cr, Mo, Ni, W, V, and Nb, alloys of these metals with each other or with other metals, and compounds with carbon and the like. Further, at this time, the high hardness metal 74 is supplied alone or in combination of two or more kinds.

The high hardness metal 74 supplied into the plasma arc from the respective introduction pipes 24a and 24b is heated by the plasma arc and mixed into the molten pool 72 at high speed. Here, the ejection pressure of the plasma arc acts on the high hardness metal 74, and the device 10
Since the movement of the high hardness metal 74 is controlled to be displaced in a predetermined direction above the workpiece W, the high hardness metal 74 is stirred and uniformly dispersed within the molten pool 72. At this time, if the high-hardness metal 74 is easily melted, it will be melted in the molten pool 72, while if it is difficult to melt, it will be dispersed in the molten pool 72.

In this way, after displacing the device 10 and forming the molten pool 72 at a predetermined portion of the workpiece W,
The power supply to the electrode 30 and the workpiece W is stopped. Next, when the work W is cooled for a predetermined period of time, a hardened layer in which the high hardness metal 74 is uniformly dispersed or mixed is formed on a desired surface layer portion of the work W.

By the way, as described above, the diameter of the plasma arc generated between the electrode 30 and the workpiece W is suitably reduced by the shielding gas supplied through the respective passages 18 and 20. Therefore, the high hardness metal 7 supplied from the respective introduction pipes 24a and 24b
4, to form a good molten pool 72 in the workpiece W without any inconvenience such as diffusion of the plasma arc, and to achieve a uniform mixing effect of the high hardness metal 74 on the workpiece W. I can do it.

Furthermore, in this case, if the high-hardness metal 74 supplied into the plasma arc from the respective introduction pipes 24a and 24b adheres to the first nozzle tip 16 when the device 10 is driven, the arc from the tip 14 of the nozzle tip 16 , that is, double arcs often occur. When a double arc occurs in this way, the energy of the plasma arc injected onto the workpiece W becomes unstable, and, for example, the plasma arc does not travel straight, making it impossible to accurately inject it to a desired location on the workpiece W. At the same time, the first nozzle tip 16 may be damaged.

However, in the present invention, the first nozzle tip 1
A second nozzle chip 22 is provided completely electrically insulated from the first nozzle chip 16 via insulators 48, 56, and 62 so as to surround the second nozzle chip 6, and the second nozzle chip 22 and the first nozzle chip 16 are connected to each other. A shield gas passage 18 is defined between them. Therefore, the shielding gas is injected to the tip 14 of the first nozzle tip 16 through the first passage 18, and the introduction pipes 24a, 24 are injected into the tip 14.
It is possible to prevent the high hardness metal 74 supplied from b from adhering.

Furthermore, in order to maintain the second nozzle tip 22 electrically insulated from the first nozzle tip 16,
For example, even if the high hardness metal 74 adheres to the second nozzle tip 22, a double arc will not occur between the second nozzle tip 22 and the work W. Moreover, by constantly cooling the second nozzle tip 22 with the cooling water supplied to the opening 60, the high hardness metal 74 is prevented from melting and adhering to the second nozzle tip 22, and the second nozzle tip 22 can be easily cooled from the second nozzle tip 22. It can be easily removed. As a result, the workpiece W is prevented from adhering to the first nozzle tip 16 with the high hardness metal 74.
It is possible to achieve highly accurate surface hardening work by accurately injecting a plasma arc. Further, it is possible to reduce damage to the first nozzle tip 16 as much as possible and to use the apparatus 10 extremely efficiently.

As described above, according to the present invention, a hardened metal is supplied to the plasma arc while generating a plasma arc between an electrode and a workpiece, and a hardened layer with excellent wear resistance is obtained on the workpiece. A shielding gas is supplied to the first nozzle chip that injects the plasma arc, surrounding the second nozzle chip in an electrically insulated state, and preventing the attachment of high-hardness metal from the second nozzle chip to the first nozzle chip. . Therefore, it is possible to prevent the occurrence of an arc between the first nozzle tip and the workpiece due to the attachment of high-hardness metal to the first nozzle tip. Therefore, it is possible to accurately inject the plasma arc onto a desired portion of the workpiece, and it is possible to form a highly accurate hardened layer. Moreover,
No arc is generated between the first nozzle tip and the workpiece, and the wear and tear of the first nozzle tip is reduced as much as possible, making it possible to use the apparatus effectively. Furthermore, since the second nozzle tip is maintained in an electrically insulated state from the first nozzle tip, even if high-hardness metal adheres to the second nozzle tip, an arc will not occur between the second nozzle tip and the workpiece. There is no risk of this occurring.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments, and various improvements and changes in design can be made without departing from the gist of the present invention. Of course.

[Brief explanation of the drawing]

Fig. 1 is a partially omitted exploded view of a metal surface hardening device according to the present invention, Fig. 2 is a partially omitted front vertical sectional view of the device of the present invention, and Fig. 3 is a partially omitted front view showing the operation of the device of the present invention. FIG. 10...device, 12...shield cap, 1
6... Nozzle tip, 18, 20... Passage, 22
...Nozzle tip, 24a, 24b...Introduction pipe,
26... Body part, 30... Electrode, 36... Nozzle part, 42... Ejection member, 48, 56, 62... Insulator, 64... Nozzle part.

Claims (1)

[Scope of Claims] 1. A first nozzle chip having an electrode therein and defining a narrow nozzle opening for ejecting plasma gas; a second nozzle chip that surrounds the nozzle chip and supplies shielding gas to the tip of the first nozzle chip, and has a cooling water opening formed therein; a shield cap for supplying shielding gas through the nozzle tip, and a first hole and a second hole that are coaxially formed at a predetermined angle in the second nozzle tip and the shield cap, A metal surface hardening device comprising: a metal introduction pipe that supplies powder or granules of high hardness metal toward the plasma gas. 2. In the device according to claim 1,
Fix the shield cap to the second nozzle tip,
A metal surface hardening device in which the second nozzle tip and the shield cap are integrally attached to the device body.