Mold steel quenching is heating the mold steel to a certain temperature and keep it warm for a certain period of time, and then quickly cooling it. This process is called quenching. The main purpose of quenching is to make all or most of the structure of the mold steel change to austenite, obtain high toughness, and then quench at an appropriate temperature so that the product workpiece has the expected properties. Quenching is an extremely critical task in the heat treatment method to achieve the required comprehensive physical properties and wear resistance. Whether it is successful depends mainly on the heating rate, quenching temperature, holding time, and subsequent cooling method. For the heating rate, the temperature rise is too slow during heating, the product workpiece is easy to oxidize and carburize, the service life of the workpiece is low, and the cost is increased. However, if the temperature is raised too high, the surface and the center of the mold will cause a temperature difference. The greater the temperature difference, the greater the internal stress, and therefore, the greater the probability of deformation cracking.

The bending coefficient of stainless steel refers to the ratio of the minimum bending force required to the strength of the material itself under different material, thickness, and bending radius conditions. It is one of the important indicators to measure the bending performance of stainless steel. In the bending process of stainless steel, it is the ratio of the increase in the bend length after bending to the original length. Generally speaking, the bending coefficient of stainless steel is about 0.33.

1. Inferior thick-walled seamless stainless steel pipes are more likely to fold. Folding refers to various fold lines on the surface of thick-walled seamless stainless steel pipes. This generally runs through the entire longitudinal direction of the product. The reason for the folding is that inferior manufacturers, in pursuit of efficiency, press down too much, produce ears, and fold during the next rolling. The folded product will crack after bending, and the strength of the thick-walled seamless steel pipe will drop significantly.

2. Inferior thick-walled seamless stainless steel pipes are more likely to be scratched, because the equipment and facilities of inferior manufacturers are relatively simple, which is easy to produce burrs and scratch the surface of thick-walled seamless stainless steel pipes. Deep scratches may reduce the strength of thick-walled seamless stainless steel pipes.

3. The surface of inferior seamless stainless steel pipes is more likely to crack. The reason is that the quality of the blanks is poor. Most of them are adobes, which have many pores. The adobes are cracked due to the effect of thermal stress during the cooling process, and cracks appear after rolling.

4. Scarring is easy to occur on the surface of inferior seamless stainless steel pipes because the material of inferior thick-walled seamless stainless steel pipes is uneven, there are many impurities, and generally the equipment and facilities of inferior thick-walled seamless stainless steel pipe manufacturers are relatively backward, which is easy to stick to the steel. These impurities bite the rollers and easily cause scarring.