What are the common problems in austempering spiral welded steel pipes?

What are the common problems in austempering spiral welded steel pipes? Isothermal quenching is a key processing technology in the processing and manufacturing of spiral welded steel pipes. What are the common problems in the whole process of isothermal quenching? Isothermal quenching is one of the reasonable heat treatment methods to reduce the deformation and cracking of spiral welded steel pipes, but how to correctly choose this processing method should be based on the spiral material, size, strength, ductility, deformation and other requirements of the spiral steel pipe, and its actual work. The following is a summary of the issues that must be paid attention to during the isothermal quenching process for reference by heat treatment process operators.

If steel types with low cutting performance such as carbon steel spiral steel pipes are austempered, the heating temperature of the heat treatment should be appropriately increased. Isothermal quenching is limited by the steel grade and the size of the spiral steel pipe. When performing isothermal quenching, the basic standard is to ensure that the spiral steel pipe is not prone to high temperature changes during the entire refrigeration process.

Therefore, the steel type and size of the spiral steel pipe directly affect the quality of austempering. Generally designated as carbon steel spiral steel pipe. The reasonable thickness of carbon steel should not exceed 5mm, and the reasonable thickness of carbon steel should be less than 30mm. From the perspective of carbon content, carbon steel between 0.42% and 0.68% is not suitable for isothermal quenching, while carbon steel above 0.6% can be isothermal quenching. The temperature and time of isothermal quenching should be specified according to the characteristics of spiral steel pipe. The criterion is that all martensite becomes low martensite. Relevant refrigeration substances generally use nitrate bath solutions. To ensure temperature stability, refrigeration equipment should be added to the substance. In order to prevent the temperature of the material from increasing and affecting the quality of heat treatment.

In addition, the length of the isothermal process should be determined according to the completion of changes in the spiral welded steel pipe mechanism. Taking too long will reduce work efficiency, so complete it carefully. Some spiral steel pipes that are austempered are not quenched. However, for some product workpieces that have undergone toughening heat treatment, the internal residual martensite may transform into austenite during the subsequent air cooling process, so quenching must be performed to eliminate the ductility and smoothness of the spiral steel pipe. It must be noted that the quenching temperature should be lower than the isothermal process temperature.