Why does 304 stainless steel seamless pipe have surface hardening?

The outer surface of 304 stainless steel seamless pipe will harden after manufacturing. In fact, there are many reasons for this, the main reason is that there are some problems in the quenching process of processing, which is a common cause of outer surface hardening. Many people don’t know the principle yet. First, why does the outer surface of the 304 stainless steel seamless pipe harden?

1. Flame quenching: This is a quenching method that uses flames of oxygen, acetylene and other gases to stop heating;

2. Carburizing and quenching: In order to only increase the carbon content of the steel surface, the stainless steel seamless pipe is put into the carburizing agent, and the heating and carburizing and quenching are stopped. As the carburizing agent, there are liquid carburizing agents such as solid carburizing agents such as charcoal and coke, and gaseous carburizing agents such as carbon monoxide. When the heating is stopped in this carburizing agent, the carbon element will penetrate into the outside of the steel pipe, and only the outside of the steel pipe will become high carbon steel. The depth of the carburized layer can reach millimeters;

3. Nitriding: The method of infiltrating nitrogen into the surface of 304 stainless steel seamless pipe is called nitriding. There are other nitridations terminated by ammonia synthesis and liquid nitridations terminated by hydrogen acid. The advantage of this method is that only heating is required, no quenching and tempering are required, and because the heating temperature is lower than carburizing, the 304 stainless steel seamless pipe will not deform during heat treatment;

4. High-frequency quenching: Put the 304 stainless steel seamless tube into the high-frequency coil, connect the high-frequency current, and an induced current will be generated in the workpiece. But the high-frequency current is only concentrated on the outside of the steel pipe, so only the outside of the steel pipe is heated. This method of heating and quenching is called high-frequency induction heating and quenching.

304 stainless steel seamless pipe is a kind of hollow long round steel, which is widely used in petroleum, chemical, medical, food, light industry, mechanical instrumentation and other industrial transportation pipelines and mechanical structural components. In addition, when the bending and torsional strength are the same, the weight is lighter, so it is also widely used in the manufacture of mechanical parts and engineering structures, as well as in the production of various conventional weapons, barrels, shells, etc.

Author
Chase Liu