The weld area is heat treated using a medium frequency induction heating machine. How should the heating temperature be controlled?

The weld seam is heat treated using a medium frequency induction heating machine. The uniformity of its heating temperature is an important guarantee for the quality of the heat treatment of the welded pipe. Therefore, it is crucial to control and adjust the weld heating temperature. Today, the editor will tell you how to control the heating temperature in the weld area.

The heating temperature of the weld zone is transmitted to the control system through the temperature signal obtained by the infrared thermometer. After the PLC or PID regulator compares and calculates the temperature set value, it sends an instruction to the power adjustment system to adjust the power of the main heating coil to keep the heating temperature stable, thus completing the closed-loop control of the power temperature. This closed-loop control system can control a single heating coil or multiple heating coils. At present, in order to meet the needs of weld heat treatment, it is hoped that the temperature control accuracy of the intermediate frequency heating machine during transverse magnetic field heating can reach the following levels.

①Weld annealing treatment. The annealing temperature is below 750°C, and the temperature control accuracy is not less than ±25°C.

②Weld seam normalizing treatment. The normalizing temperature is 850-950℃, and the temperature control accuracy is not less than ±15℃.

③Weld quenching and tempering treatment. The quenching temperature is 880-960°C, and the temperature control accuracy should be less than ±10°C; the tempering temperature is 450-700°C, and the temperature control accuracy should be less than ±5°C.

The temperature control accuracy of transverse magnetic field heating welds is lower than that of longitudinal magnetic field heating. The latter realizes closed-loop automatic control of power temperature through a computer system, and its temperature control accuracy can reach the level of ±5°C. This temperature control precision significantly improves the uniformity and stability of the mechanical properties of steel during heat treatment.