Cold rolling rolls are generally quenched by medium frequency induction heating. The main domestic roller manufacturers generally use dual frequency quenching ( power frequency + intermediate frequency ) and double power frequency quenching ( power frequency + power frequency ) . Due to the large size of the power frequency induction heating device and the complicated power adjustment system, the investment amount and maintenance cost of the equipment are increased. The thyristor inverter type intermediate frequency power supply has small volume and simple structure, and double intermediate frequency quenching can be realized by using two intermediate frequency power sources. Regarding the research on the double intermediate frequency quenching of cold rolls, there is no precedent in China, so it is necessary to carry out research in this area.

Process characteristics of cold rolling double inductor quenching method

   At present, cold rolling rolls are generally subjected to induction heating quenching. Due to the skin effect and rapid heating of induction heating, this heating method has problems such as shallow heating layer and short austenitizing time. In order to solve these problems, an integral induction heating quenching method and a dual inductor progressive quenching method are generally employed. For the cold roll, especially the slender cold roll of the roll body, the two-inductor progressive quenching method represented by double-frequency quenching tends to be used. This is because the double-inductor progressive quenching has the following advantages compared with the overall induction heating quenching: 1 The progressive quenching method does not require the use of high-power induction heating equipment, and does not require the design and manufacture of complex and large inductors. 2 The progressive quenching method makes the temperature rise of the roll core not too high, which not only increases the depth of the hardened layer by the “self-quenching” effect of the roll, but also avoids the peak of the residual tensile stress appearing in the core or center of the roll with poor metallurgical quality. On the wall of the hole. 3 Due to the induction heating, the surface temperature of the roll is higher than the surface temperature ( this is determined by the characteristics of induction heating ) . When the whole induction heating is used for quenching, the secondary surface of the roll is in a high temperature for a long time, and it is easy to generate overheating. The use of double inductor progressive quenching, because there is a "heating interval" between the two inductors, at this time, the heat in the subsurface high temperature zone of the roller can be quickly transferred to the surface layer and the inner layer, so that the secondary surface of the roller is not prolonged. It is at a high temperature to avoid overheating. 4 Since there is no heating unevenness caused by magnetic field escape, etc., accurate temperature control can be easily realized.

   The double-sensor quenching method changes the heating process of the roller by the traditional single-sensor quenching method to the heating→heating→cooling type, thus overcoming the shortcomings of short austenitizing time and shallow heating depth. The performance index of the cold roll was significantly improved.