Revealing the reasons why local temperature unevenness occurs when steel is heat treated using a medium-frequency induction diathermy furnace

Nowadays, more and more people use medium frequency induction diathermy furnaces to heat treat steel. However, during the operation, affected by many factors, the steel may produce some defects, such as local temperature unevenness, deformation, oxidation, etc. , thus greatly affecting the service life of steel. Today, we will take a look at the reasons for local temperature unevenness in steel.

When steel is continuously heated, local or section temperature unevenness occurs. This phenomenon is likely to occur under rapid heating conditions. The reasons for local temperature unevenness are as follows.

(1) The steel conveying speed is unstable. Under the condition of rapid heating, the fast forward speed of steel can reach 1.0-1.5m.s-1, and the heating speed can reach 50-100℃.S-1. In this case, when the transmission speed fluctuates ±(0.2-0.3) m.S-1, the steel temperature will fluctuate by 10-20°C. The instability of the transmission speed will bring large fluctuations in the heating temperature of the steel, which is one of the reasons for the uneven longitudinal temperature of the steel.

(2) Unstable rotation speed. When the rotation speed of the rotating steel material changes, it will also affect the forward speed, which will in turn affect the fluctuation of the heating temperature of the steel material, causing uneven longitudinal temperature.

(3) Fluctuation of heating power. The effect of heating power on the temperature of steel is obvious. The stability of the output power is the most important condition to ensure the uniform longitudinal temperature of the steel. This is why the induction heating rapid heat treatment production line must have a temperature-power automatic control system.

(4) The concentricity between the steel and the heating sensor is poor. When the steel and the sensor are not concentric, the steel surface temperature on the side with a small gap is high, and the temperature on the side with a large gap is low. Its influence can be alleviated when heating by rotating forward, but when the rotating speed is insufficient, it will still cause uneven longitudinal temperature of steel. Therefore, maintaining the concentricity of the heating steel and the inductor plays an important role in reducing the longitudinal temperature unevenness.

This article briefly analyzes the reasons for the uneven temperature defects when steel is heated. Only by understanding these can we find corresponding solutions to ensure the heat treatment quality of steel.