High frequency quenching technology of cold drawn seamless tubing

Cold drawn seamless tubing is a steel pipe with high dimensional accuracy and good surface finish for mechanical structure and hydraulic equipment. Now due to the development of science and technology, the ordinary quenching technology of cold drawn seamless tubing has been upgraded to high-frequency quenching technology. At present, high-frequency quenching technology has been widely used.

High frequency quenching technology classification:

The original high-frequency quenching only uniformly heats the cold drawn seamless tubing, and now it is changed to the direct energization quenching method, that is, the resistance heating generated by directly passing the high-frequency current to the heated object. Due to the proximity effect and skin effect, the surface current density is high, so the tooth surface is fully heated and quenched.

The quenching part has developed from the original only the tooth surface, the tooth surface and the back surface to the tooth surface, the back surface and the shaft part. The back surface and the tooth surface are quenched by direct energization, and the shaft part is still quenched by moving. However, when the tooth surface and the back surface are treated twice, the hardness of a part of the quenched part (usually the back surface) will decrease due to the thermal influence of the second quenching. Heating coils suitable for various treatments can greatly improve the performance of cold drawn seamless tubing.

In addition to the direct energization method, there is also a quenching method in which a ring-shaped heating coil is used to move the object to be heated while simultaneously heating the tooth surface and the back surface (sometimes extending to the shaft). Since this method does not need a pressing device, the equipment cost is low, and the heating coil is not affected by the ring teeth and other parts, and can be shared. However, because it is difficult to fully quench the bottom of the tooth surface, it has not been promoted. In order to solve the above problems, a method of quenching the tooth surface and the back of the cold drawn seamless tubing has been developed.

In a static state, the columnar conductor is energized for a set time to induce induction heating of the tooth surface and the back surface. Because it is similar to the shape of the tooth surface and the back surface, all parts can be heated evenly; due to the rotation of the heated object, an induced current is generated when passing through the lower part of the columnar conductor to heat the side part, so as to obtain the overall heating and cooling of the whole. Quenching (if cooling after non-rotation heating, only the flanks and backsides are quenched).

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