Unit energy consumption of steel pipes using medium frequency heating machine for induction heating quenching and tempering treatment

Some people say that the medium frequency heating machine is very energy-saving for quenching and tempering heat treatment of steel pipes, so many manufacturers are using it. So is this really the case? If you look at the unit energy consumption during induction heating and tempering treatment of steel pipes, you will understand.

Induction heating of steel pipes mainly uses intermediate frequency heating machines for quenching and tempering. Similar to bar and bar steel, the main factors affecting its unit energy consumption are heating temperature, heating speed and electrical efficiency of power supply system.

Under production conditions, the unit energy consumption during induction heating and tempering treatment of steel pipes is listed in the table below. Little data has been published on the unit energy consumption of induction heating quenching and tempering treatment of large-diameter steel pipes. The data listed in the table are for reference only. It can be seen that the unit energy consumption decreases significantly with the increase of productivity. In large-scale steel pipe induction heating and tempering treatment production lines, the unit energy consumption of oil well steel pipes can reach the level of 1000-1100MJ.t-1. In the induction heating quenching and tempering treatment production line of small high-strength steel pipes, the unit energy consumption of the steel pipes should be at the level of 1200-1400MJ.t-1.

Unit energy consumption of steel pipe induction heating and rapid heating, quenching and tempering treatment

We have studied the factors that affect the unit energy consumption during induction heating quenching and tempering of high-strength steel pipes with a diameter of 50-76mm, and obtained the following results.

(1) The relationship between induction heating temperature and unit energy consumption. According to the heating speed of induction heating carbon steel and low alloy steel pipes is 30-40℃.S-1, the relationship between the heating temperature and unit energy consumption during quenching and tempering heating when the power supply is directly inducted can be seen that the heating temperature and unit energy consumption Directly proportional to the straight line relationship.

(2) The relationship between heating rate and unit energy consumption. According to the relationship between the heating rate and the unit energy consumption of carbon steel and low alloy steel pipe at the quenching and tempering temperature, it can be known that when the heating rate reaches a certain value and continues to increase the heating rate, the decrease in unit energy consumption is not obvious, and becoming steady. This is because at the corresponding quenching temperature (900-920°C) and tempering temperature (700-710°C), they are respectively close to the theoretical value of the unit energy consumption.

(3) The relationship between the structure of the sensor and the unit energy consumption. Whether the sensor has an insulating bushing or not has a greater impact on heat energy loss and is directly related to unit energy consumption. According to experiments, it can be seen that as the heating temperature increases, the role of the insulating bushing increases, and the heat loss caused by radiant heat loss at high temperatures is serious. At a temperature of 900°C, the difference in unit energy consumption with and without an insulating bushing is about 200MJ.t-1, accounting for about 25% of the average unit energy consumption. Therefore, when steel pipes (including steel rods) are induction heated to temperatures above 700°C for heat treatment, an insulating bushing must be added to the inductor to reduce radiation heat loss.

To sum up, through the analysis of the factors affecting the unit energy consumption of steel pipe induction heating, we can know that in order to reduce the unit energy consumption, we must control the heating temperature as low as possible, choose a reasonable heating speed and an inductor with good thermal insulation performance.