JPH0469031B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an improvement of a plasma torch used for overlay welding using powder, and for example, for overlay welding on the face surface of engine valves for automobiles and ships. The present invention relates to a plasma torch for powder overlay welding which is applied to various other types of overlay welding.

(Prior Art) Conventionally, when manufacturing engine valves for automobiles, for example, overlay welding is often performed to improve the heat resistance and wear resistance of the valve face.

In this overlay welding, it is required that the welding to the material to be overlaid, such as a valve, be complete, and that the composition of the overlay weld metal be close to that of the overlay material before overlay welding. Attempts are also underway to adopt plasma overlay welding using powder during overlay welding.

The plasma torch for powder overlay welding used in this case supplies plasma working gas from between a rod-shaped electrode and a torch inner cylinder arranged around the rod-shaped electrode, and also supplies plasma working gas from between a rod-shaped electrode and a torch inner cylinder arranged around the rod-shaped electrode. There is a configuration that includes a shielding gas supply path that supplies overlay welding powder into the plasma arc from between the torch outer cylinder and supplies shielding gas surrounding the plasma arc from the end of the torch outer cylinder. There was a method in which the powder for overlay welding was melted by a plasma arc while shielding the outside air with the shielding gas, and the overlay welding was performed on the surface of the overlay material.

However, conventional plasma torches for powder overlay welding have the problem that the shielding gas may not surround the plasma arc uniformly, and areas with less shielding gas may not be sufficiently isolated from the outside air. Was. Therefore, there was an idea to provide a shield gas flow regulator at the end of the torch outer cylinder, which is the open end of the shield gas supply path.
Splash of powder and molten metal generated during overlay welding adheres to the shield gas regulator, increasing shield gas passage resistance within the shield gas regulator, making it difficult to smoothly supply the required amount of shield gas. There were problems such as not being able to do it.

Therefore, the shielding gas supply passage is formed into a torch axis parallel gas supply passage running in the same direction as the torch axis, and a torch axis centripetal gas supply passage communicating with this at an angle and facing the torch axis direction. There was also the idea of providing a shield gas flow regulator inside the gas supply path parallel to the torch axis (Utility Model No. 54-184326).
However, when the rectified shielding gas flows into the torch axis centripetal gas supply path, it flows at an angle, and the distance from the shielding gas rectifier to the open end of the shielding gas supply path is large. As a result, rectified shielding gas may not be supplied around the plasma arc, and
There is a problem in that a small amount of shielding gas may not be able to uniformly surround the plasma arc and effectively isolate it from the outside air.

(Purpose of the Invention) This invention was made by focusing on the above-mentioned conventional problems. Even if the shielding gas is supplied uniformly around the plasma arc, the flow of the shielding gas is uniform in the horizontal section, so that It is possible to isolate from the outside air extremely effectively and for a long time, and by generating a stable plasma arc, it is possible to perform overlay thermal spraying using powder extremely well, and it also provides shielding. It is an object of the present invention to provide a plasma torch for powder overlay welding that can reduce the amount of gas supplied.

(Structure of the Invention) A plasma torch for powder overlay welding according to the present invention supplies plasma working gas from between a rod-shaped electrode and a torch inner cylinder arranged around the rod-shaped electrode, and also supplies a plasma working gas to the torch inner cylinder arranged around the rod-shaped electrode. The overlay welding powder is supplied into the plasma arc from between the and the torch outer cylinder,
In the plasma torch for powder overlay welding, the powder overlay welding plasma torch is configured to include a shielding gas supply path that supplies shielding gas surrounding the plasma arc from an end of the torch outer cylinder, wherein the shielding gas supply path has a cross section toward its open end. The method is characterized in that the shielding gas supply path has a constricted shape whose width gradually decreases, and that a shielding gas flow regulator is provided in a portion of the shielding gas supply path that is inside the opening end of the shielding gas supply path and forms the constricted shape. It is said that

The electrode of the plasma torch according to the present invention has a rod shape, and is made of, for example, a high melting point metal (or alloy) such as tungsten. In this case, it is possible to form the entire electrode from a high-melting point material such as tungsten, but it is also possible to form the plasma arc generation part from the above-mentioned high-melting point material and the other parts from a conductive water-cooled pipe. can.

The torch inner cylinder is disposed so as to surround the rod-shaped electrode, and is configured to supply plasma working gas from between the rod-shaped electrode and the torch inner cylinder. Further, the torch outer cylinder is arranged so as to surround the torch inner cylinder, and the overlay welding powder is supplied into the plasma arc from between the torch inner cylinder and the torch outer cylinder. be. The powder for overlay welding is one obtained by pulverizing heat-resistant alloys, wear-resistant alloys, etc. used for overlay use, for example, by liquid spraying, gas spraying, or the like.

Further, a shielding gas supply path is provided for supplying shielding gas surrounding the plasma arc from an end of the torch outer cylinder, so that the plasma arc and the overlay welding portion are isolated from the outside air.

In this case, the shielding gas supply path is not made to have a constant width cross-section up to its opening end, but the shielding gas supply path is made into a narrow shape whose cross-sectional width gradually decreases toward the opening end, and the shielding gas supply amount is A good shielding effect can be obtained even when the amount is reduced.

A shielding gas flow regulator is provided in the shielding gas supply path so that the shielding gas flows uniformly around the plasma arc and does not form thick or thin portions of the shielding gas, but powder and molten metal generated during overlay welding are In order to prevent the splash from adhering to the shield gas regulator and increase the ventilation resistance of the shield gas regulator, a shield gas regulator is provided in the middle of the constricted portion of the shield gas supply path inside the opening end. A fluid is provided. As this shielding gas flow regulator, one formed of a net-like body, a sintered body, or the like made of metal or ceramic can be used.

(Embodiment) FIGS. 1 and 2 are diagrams showing an embodiment of a plasma torch for powder overlay welding according to the present invention, and this plasma torch 1 has a rod-shaped electrode connected to the cathode side of a power source (not shown). 2 at the center, and an inner torch cylinder 3 is disposed concentrically with and spaced apart from the rod-shaped electrode 2. In the illustrated example, the torch inner cylinder 3 is provided with a tip 4 at its lower end and is screwed, but these may be integrated. Then, the torch inner cylinder 3 and the tip 4
A cooling water passage 5 is provided therein, and a plasma working gas flow passage 6 is formed between the rod-shaped electrode 2 and the torch inner cylinder 3. A plasma working gas rectifier 8 having a plurality of plasma working gas passage holes 7 is disposed therein. This plasma working gas regulator 8 is
A plurality of plasma working gas passage holes 7 provided at equal intervals in the circumferential direction rectify the flow of the plasma working gas supplied from the top in the direction of the arrow, and the flow of the plasma working gas is made uniform in the horizontal cross section. In addition, it also functions as a holder for the rod-shaped electrode 2, and always holds the rod-shaped electrode 2 concentrically with the torch inner cylinder 3 to prevent the rod-shaped electrode 2 from being worn out on one side.

Furthermore, a torch outer cylinder 11 is arranged at intervals on the outer circumference of the torch inner cylinder 3, and a nozzle hole 12 is formed in the lower end portion of the torch outer cylinder 11. A powder supply path 13 is formed between the torch outer cylinder 11 and powder 14 for overlay welding can be supplied. A cooling water passage 15 is also formed in the nozzle portion of the torch outer cylinder 11. Furthermore, the torch outer cylinder 11 is provided with a shielding gas supply passage 17 that extends centripetally toward the axis of the torch, and the cross-sectional width of this shielding gas supply passage 17 gradually decreases toward its open end. It has a narrow shape so that a good shielding effect can be obtained even when the amount of shielding gas supplied is reduced.

Inside the shield gas supply path 17 provided in the torch outer cylinder 11, an annular shield gas rectifier 16 as shown in FIG. 2 is provided concentrically with the nozzle hole 12 to supply the shield gas. Road 17
The shielding gas supplied from the plasma arc is designed to uniformly shield the area around the plasma arc. At this time, in order to prevent powder and molten metal splash generated during overlay welding from adhering to the shielding gas regulator 16 and increasing its ventilation resistance, resulting in uneven or insufficient supply of shielding gas, The shield gas regulator 16 is provided at a position recessed inward from the open end of the shield gas supply path 17, and prevents the splash from adhering to the shield gas regulator 16 to keep the ventilation resistance of the shield gas regulator 16 constant. A good shielding effect against plasma arc is always obtained. The shield gas regulator 16 is formed of a stack of net-like bodies, or a sintered body of metal, ceramics, etc. having an appropriate air permeability (density).

During powder overlay welding, the rod-shaped electrode 2 is connected to the cathode side of a power source (not shown), and the anode side of the same power source is connected to the material to be overlaid (not shown).
At the same time, a plasma arc is generated between the material to be overlaid and the shield gas is supplied from the shield gas supply path 17 to isolate the plasma arc and the part to be overlaid from the outside air, and at the same time, a , the powder 14 is supplied into a plasma arc, melted, and then welded on the surface of the material to be overlaid.

At this time, a plasma working gas rectifier 8 is provided between the rod-shaped electrode 2 and the torch inner cylinder 3, and
Since the shielding gas supply path 17 is provided with the shielding gas rectifier 16, the plasma working gas and the shielding gas are uniform in horizontal cross section, preventing uneven wear of the rod-shaped electrode 2, and reducing the amount of powder. By uniformly supplying 14 and effectively shielding, good overlay welding is possible.

According to an example of implementation, compared to a plasma torch in which the sealing gas supply passage 17 has a shape in which the cross-sectional width becomes constant toward the open end, the shielding gas supply passage 17 is arranged in such a shape as shown in FIG. For a plasma torch with a narrow cross-sectional width that gradually decreases toward the open end, the shielding gas supply amount should be set at 70~
Even when it was reduced to 80%, the same shielding effect was obtained and good powder overlay welding could be performed.

(Effects of the Invention) As explained above, in the plasma torch for powder overlay welding according to the present invention, plasma working gas is supplied from between the rod-shaped electrode and the torch inner cylinder arranged around the rod-shaped electrode. and a shielding gas supply path for supplying overlay welding powder into the plasma arc from between the torch inner cylinder and the torch outer cylinder, and for supplying shielding gas surrounding the plasma arc from the end of the torch outer cylinder. In the plasma torch for powder overlay welding, the shielding gas supply path has a narrow shape whose cross-sectional width gradually decreases toward the open end, and the shielding gas Since the shielding gas flow regulator is provided in the part inside the opening end of the supply channel and in the constricted shape, the amount of shielding gas supplied to isolate the plasma arc and overlay welding part from the outside air can be reduced. Even when the amount of shielding gas is reduced, the supply of shielding gas can be made uniform around the plasma arc, and the flow of the shielding gas is uniform in the horizontal cross section, so plasma arc and overlay welding are possible. It is possible to isolate a part from the outside air extremely effectively and consistently over a long period of time, and to perform overlay welding using powder well by generating a stable plasma arc. It is possible to perform overlay welding with an excellent bead shape, and it has very excellent effects in that it is possible to reduce the amount of shielding gas supplied.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a plasma torch for powder overlay welding according to an embodiment of the present invention, and FIG. 2 is a plan view of the shield gas flow regulator shown in FIG. 1. 1... Plasma torch for powder overlay welding, 2...
Rod-shaped electrode, 3... Torch inner cylinder, 6... Plasma working gas flow path, 11... Torch outer cylinder, 13... Powder supply path, 14... Overlay welding powder, 16... Shield gas rectifier, 17... Shield gas supply path.

Claims (1)

[Claims] 1. Plasma working gas is supplied from between the rod-shaped electrode and the torch inner cylinder arranged around the rod-shaped electrode, and a plasma working gas is supplied into the plasma arc from between the torch inner cylinder and the torch outer cylinder for overlay welding. supply powder,
In the plasma torch for powder overlay welding, the powder overlay welding plasma torch is configured to include a shielding gas supply path that supplies shielding gas surrounding the plasma arc from an end of the torch outer cylinder, wherein the shielding gas supply path has a cross section toward its open end. The method is characterized in that the shielding gas supply path has a constricted shape whose width gradually decreases, and that a shielding gas flow regulator is provided in a portion of the shielding gas supply path that is inside the opening end of the shielding gas supply path and forms the constricted shape. A plasma torch for powder overlay welding.