Process analysis of heat treatment of screwdrivers using high-frequency induction heating machine

At present, the quenching of 45 steel screwdrivers is mostly heated by salt bath furnaces (small mesh belt furnaces are also used). The disadvantage is that the heating efficiency is low, and the preheating alone takes up to 2 hours, which is very labor-intensive. Some units use high-frequency induction heating machines for quenching, but since the workpieces need to be heated manually one by one, the production efficiency is not high. Through the modification and debugging of the high-frequency induction heating machine, induction heating was successfully applied in the automatic quenching line of screwdrivers.

A factory has modified the sensor of a 50kW high-frequency induction heating machine from a round shape to a flat shape. In this way, the screwdriver relies on the conveyor belt to pass through the sensor in rows for heating. After reaching the predetermined temperature, it passes through the tail of the sensor. Water spray device to complete the quenching of the screwdriver head. The weaver was changed from a round shape to a flat shape, which reduced the density of magnetic field lines in the sensor. The screwdriver must pass through the sensor smoothly, and the gap cannot be too small. If it starts with "一", the gap should be larger, so the load of the high-frequency induction heating power supply is very small, and you will encounter a lot of trouble during the debugging process. First, the tank pressure is too high. Even if the center tap of the quenching transformer and the output tap of the main vibration coil of a tank are all turned over, the tank pressure cannot be reduced. The screen current is not large and the gate current is too high. Considering that the quenching depth of the screwdriver head is required to be deep, the feedback capacitor can be increased to reduce the grid current and reduce the slot pressure. The capacitance of the second tank is increased to increase the screen current and suppress the tank voltage and gate current. _Finally, adjust the anode voltage to 6kV, anode current 2A, grid current 0.4A, and tank circuit voltage 4kV. At this time, the preparation work is basically normal, but the power output is not large and the heating speed is very slow. To address these problems, a magnetic conductor is added to the inductor. The magnetic permeability characteristics and driving effect of the magnet are used to change the influence of the ring effect of high-frequency current, so that the high-frequency magnetic field is concentrated at the opening of the magnet, reducing the effective gap between the inductor and the heating surface of the piece, and concentrating the magnetic lines of force. , the heating conditions are improved and the heating efficiency is increased. Finally, the equipment was adjusted to: anode voltage 6kV, cell voltage 3.SkV, screen current 2.3A, and grid current 0.3A. The output of the equipment is stable and the heating efficiency is very high.

Through the above-mentioned improvement of the screwdriver quenching process, the production efficiency has been improved, the working conditions have been improved, and the labor intensity has been reduced. Compared with the original salt bath furnace, it has the following characteristics:

①The power of the salt bath furnace is 45kW, and the power of the high-frequency equipment is 40kW (usable power).

② Output (4-6in screwdriver): Salt bath preheating for 2 hours, quenching 5,000 pieces/h. The high-frequency induction heating machine does not require preheating and can quench 4,000 pieces/h.

③Number of operators: 6 for salt bath furnace and 3 for high-frequency induction heating power supply. According to analysis, the labor intensity of salt bath quenching is about 5:1 compared with high-frequency induction quenching. Affected by mechanical transmission and operator proficiency, the potential of high-frequency induction hardening has not been fully exploited. If the speed of conveying workpieces is increased and high-frequency equipment with higher power is selected, such as 100kw, the production efficiency will be doubled.

This article briefly introduces the high-frequency heat treatment process of screwdrivers. I hope everyone can apply the knowledge learned today to work and produce high-quality screwdrivers that meet the requirements. If you want to know more about the heat treatment process of workpieces, you can search for information yourself or consult the editor.