Analysis of Advantages and Disadvantages of Resistance Welding Technology

Resistance welding is to press the workpiece to be pressed between the two electrodes, and to pass current, and use the resistance heat generated by the current flowing through the contact surface of the workpiece and the adjacent region to heat it to a molten or plastic state, so as to form a metal bond. Ways.

In spot welding, the workpiece is welded only on a limited contact surface, the so-called "point", and forms a spheroidal nugget. Spot welding can be divided into single spot welding and multi spot welding. In the case of multi-spot welding, two or more pairs of electrodes are used, and a plurality of nuggets are formed in the same process.

Seam welding is similar to spot welding. During seam welding, the workpiece passes between two rotating disc electrodes (rollers) to form a continuous weld seam that is lapped before and after the strip weld.

Projection welding is a variant of spot welding. Prefabricated bumps on a workpiece. In the case of projection welding, one or more nuggets may be formed at the joint at a time.

During butt welding, the end faces of the two workpieces are in contact, and after being heated and pressurized by electric resistance, they are welded along the entire contact surface.

Resistance welding has the following advantages:

1) When the nugget is formed, it is always surrounded by the plastic ring, and the molten metal is isolated from the air, and the metallurgical process is simple.

2) The heating time is short, the heat is concentrated, so the heat affected zone is small, and the deformation and stress are also small. Usually, it is not necessary to arrange correction and heat treatment processes after welding.

3) There is no need for filler metal such as welding wire and welding rod, and welding materials such as oxygen, acetylene and argon, and the welding cost is low.

4) Simple operation, easy mechanization and automation, and improved working conditions.

5) High productivity and no noise and harmful gases. In mass production, it can be assembled on assembly lines together with other manufacturing processes. However, flash butt welding requires spark isolation and needs to be isolated.

Resistance welding defects:

1) There is still no reliable non-destructive testing method. The quality of welding can only be checked by the destructive test of process samples and workpieces, and by various monitoring techniques.

2) The lap joint of the point and seam welding not only increases the weight of the component, but also forms an angle around the nugget between the two plates, resulting in lower tensile strength and fatigue strength of the joint.

3) The equipment has high power and high degree of mechanization automation, which makes the equipment cost high and maintenance difficult, and the commonly used high-power single-phase AC welding machine is not conducive to the normal operation of the power grid. With the development of aerospace, electronics, automotive, household appliances and other industries, wear-resistant welding rods have received more attention from the society. At the same time, higher requirements have been placed on the quality of resistance welding. Fortunately, the development of microelectronics technology in China and the development of high-power thyristors and rectifiers have provided conditions for the improvement of resistance welding technology. At present, China has produced a secondary rectifying welder with excellent performance. Control boxes made of integrated components and microcomputers have been used for the matching of new welders and the modification of old welders. Advanced closed-loop monitoring technologies such as constant current, dynamic resistance, and thermal expansion have begun to be popularized in production. All of this will benefit the quality of resistance welding and expand its application.

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