JPH0645065B2 - Overlay welding method on shaft end - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is a method for welding a hardfacing material or the like to a shaft end of a valve or the like used in various internal combustion engines (gasoline, diesel engine, etc.) and turbines. Regarding

[Conventional technology]

 FIG. 4 shows an example of a conventional hardfacing welding method.

In the case of overlay welding on the shaft end, the axis 01 is clamped vertically, and the hard overlay welding 02 of stellite or the like is performed from the upper part by an automatic TIG welding method or a plasma powder overlay welding method.

Further, before, a material having good hardenability was joined to the end portion by friction welding or the like, and the shaft end was hardened by heat treatment (quenching).

[Problems to be solved by the invention]

As the operating conditions became stricter, the required hardness increased, and cost reduction was required, it became necessary to change from the quenching method to the hardfacing method such as stellite.

However, in the conventional overlay welding method, as shown in FIG.
In Fig. (a), the problem of insufficient build-up thickness due to defective bead shape 12 and in Fig. (b) the problem of surface scratches due to welding defects such as blowholes 13 could not be improved. Therefore, the defect rate was large and it was difficult to put it into practical use.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides an alternating magnetic field generated by passing an alternating rectangular wave current by providing an exciting coil at the tip of a welding torch, and Lorentz generated by the welding current. The molten metal is agitated by force. That is, a method of welding a hardfacing material such as stellite to the shaft end, in which the coaxial end is held by a clamp provided with a cooling means, and an exciting coil provided at the tip of a TIG welding torch or transfer plasma arc welding torch. An overlay welding method is provided for a shaft end, which is characterized in that an alternating current and a direct current are applied to the alloy and the molten metal is welded while being stirred alternately or in one direction.

[Action]

Since the overlay welding method for the shaft end of the present invention is the above-described welding method, by stirring the molten metal, the bead shape is flattened and the gas levitation effect causes a defective bead shape or a welding defect such as a blow hole. It is a build-up welding method that makes it possible to prevent

〔Example〕

Hereinafter, the present invention will be specifically described based on the embodiments shown in the drawings. FIG. 1 is a conceptual diagram of an apparatus applied to a method of overlay welding on a shaft end according to an embodiment of the present invention. FIG. 2 is an operation principle diagram of magnetic stirring according to the present embodiment. FIG. 3 is a graph showing the results of an effect test of magnetic field strength and magnetic field frequency for preventing undercuts and blowholes according to this example. The explanation will be given below.

In FIG. 1, targeting the end of the shaft 1 vertically held by a clamp 11 made of copper or the like that is water-cooled with cooling water 16, the alternating magnetic field generated by the exciting coil 14 provided at the tip of the TIG welding torch is used to generate stellite or the like. Stir the weld metal 2.
In the case of TIG welding, the welding material 3 is fed as a wire by the feeding roller 4 into the arc 6 at a constant speed. Also,
The clamp 11 grabs the end of the shaft 1 so as to radiate the burn-through due to overheating and the welding current.

Fig. 2 shows the operating principle of magnetic stirring, in which the molten metal is stirred by the Lorentz force generated by the alternating magnetic field generated by the DC welding current and the AC rectangular wave current. In the case of the exciting current, the magnetic field is the molten metal. Pass from top to bottom. Here, the current flowing from the electrode to the base material can be regarded as flowing radially from the center of the molten pool. Therefore, counterclockwise Lorentz force acts on the molten metal. Conversely, when the exciting current is, the magnetic field passes from bottom to top. Therefore, Lorentz force is generated in the clockwise direction. By repeating this, it becomes possible to prevent bead shape defects and welding defects such as blowholes by effective stirring, and also to refine the crystal grains of the weld metal and to make the structure uniform.

The table below shows an example of comparison of welding conditions and welding quality between the conventional method and the new method for TIG welding.
With 0G, 5Hz magnetic stirring, good welding was obtained without welding defects such as undercuts, uneven thickness, and blowholes.

The magnetic stirring conditions vary slightly depending on the physical properties of the molten metal (specific gravity, viscosity, etc.), but in the case of stellite, it can be seen from the effects of the magnetic field strength and magnetic field frequency on the undercut and blowhole prevention shown in FIG. As shown in Fig. 3, the magnetic field strength is 100-200G and the magnetic field frequency is 3
The proper range of ~ 10Hz exists in the frame.

As described above, the welding method has been described for TIG welding, but it can also be applied to the plasma powder overlay welding method using a transferable plasma arc.

〔The invention's effect〕

As described above in detail, in the present invention, the bead shape is flattened and the gas levitation effect is generated by stirring the overlay weld metal by the alternating magnetic field generated by the exciting coil provided in the welding torch. Not only welding defects such as defects can be prevented, but also the crystal grains of the weld metal can be made finer and the structure can be made uniform, which has a great effect on the quality improvement of the weld overlay on the shaft end.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an apparatus applied to a method of overlay welding on a shaft end according to an embodiment of the present invention, FIG. 2 is a working principle diagram of magnetic stirring according to the present embodiment, and FIG. FIG. 4 is a graph showing a result of an influence test of magnetic field strength and magnetic field frequency for preventing undercut and blowhole according to the embodiment, FIG. 4 is a conceptual diagram of an apparatus of a conventional hardfacing welding method, and FIG. 5 is a conventional welding method. Pertaining to
(a) is an explanatory diagram showing a bead shape defect, and (b) is an explanatory diagram showing an example of blowhole generation. 1 ... Shaft, 2 ... Welding metal, 3 ... Welding wire, 4 ... Feed roller, 5 ... Motor, 6 ... Arc, 7 ... Electrode, 8 ... Shield nozzle, 9 ... Shield gas, 10 ... DC welding power source, 11
... Clamp, 14 ... Exciting coil, 15 ... AC rectangular wave current, 16 ... Cooling water.

Claims (1)

[Claims] 1. A method for welding a hardfacing material such as stellite to the shaft end, wherein the coaxial end is held by a clamp provided with a cooling means and is provided at the tip of a TIG welding torch or a transfer plasma arc welding torch. A method of overlay welding on a shaft end, characterized in that an alternating current and a direct current are applied to the exciting coil and the molten metal is welded while alternately or unidirectionally stirring.