Hot work molds are mainly used for high temperature pressing molds, and their functions are also very extensive in the industry. Due to the cold work hardening of high manganese steel and cutting is difficult, the use of high temperature annealing process can change the size, shape and distribution of carbide particles, thereby significantly improving the cutting performance of non-magnetic die steel. Therefore, there are certain requirements for the control of heating, so is there a requirement for the heating speed of hot work die steel? Let's find out together today!
At present, the widely used cold working die materials are cold working die steel and cemented carbide. The material properties, heat treatment method or process of making molds are important links in mold manufacturing. According to the requirements of manufacturing and use, it is more important to choose the material of the cold working mold reasonably.
The heating rate is a very important parameter during heat treatment and quenching. Usually, slow heating should be adopted, and the heating rate is less than 120℃/h, which is ideal. It can reduce the deformation of the workpiece during the heating process, and play a certain role in preventing quenching and cracking.
In actual production, the method of segmented heating is used to control the heating speed to achieve the effect of slow heating. The staged principle is to heat the preheating section before the phase change Ac1 and the preheating section after the phase change Ac1.
The low temperature stage below 550°C is the elastic stage of steel, and the plastic stage after this temperature is higher. The preheating stage before heating the phase transition Ac1 is to ensure the uniform phase transition of the workpiece and reduce the volume change caused by the phase transition. The preheating of carbon steel is usually at 450~550℃, and the preheating of high alloy steel can be carried out at 550~650℃ and 820~850℃.
The preheating factor is determined according to the furnace type and charge, and the preheating time must be longer than the final austenitization time in any state.
The workpiece heated by the salt bath furnace must be preheated, and it is unreasonable to control the heating rate of the workpiece heated by the box-type resistance furnace to be above 150°C/h.
The heating speed of hot work die steel needs to be controlled, and the operation process needs to be strictly controlled to better ensure the quality of hot work die steel.
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