Answer: If the mold is cold, the surface in contact with the high-temperature steel will expand in size, but the core will not expand when the temperature is low. As a result, the surface will be pulled apart and cracks will form. In addition, it is not good for the forged steel, because with the The contact temperature of the cool mold will drop rapidly, resulting in uneven temperature inside and outside the steel, uneven deformation and short forging time. The main technical development direction of forging dies is to improve the level of die design, adopt new die materials, and use high-efficiency and high-precision machining methods to achieve high-precision forgings under the condition of long die life. With the improvement of the overall level of my country's manufacturing industry, my country's forging die technology will reach the international advanced level, and some innovative and unique technologies will reach the international leading level.