how to prevent steel seamless tubes surface decarbonization

It is well-known that steel or seamless tubes surface is easy to rust, however, what is the meaning of decarbonization?

The service life of steel products and steel seamless tubes is associated with its surface rust and decarburization. For instance, square tube service life mainly depends on its fatigue strength and abrasion resistance. If square pipe surface decarbonization exceeds, this will reduce carbide as reinforcement and wear-resistant phase on the surface which will directly affect the performance of reinforcement and wear-resistant. In addition, the surface decarbonization layer of tool steels and bearing steels is not removal clearly, will reduce the bearing steel surface hardness and wear resistances, and during the quenching, because of different changes in outer volume is easily formed cracks on the surface. Therefore, how to prevent the steel product and steel seamless tubes surface decarbonization is be paid more attention in the production process. AGICO adopt wire rod decarburization layer importing from Japan from 0.02 to 0.04.

Seamless Tubes
seamless steel tubes

Oxygen, water vapor and carbon dioxide are main gases to cause steel products surface decarbonization. When these oxidative gas contacts the surface of heated seamless pipes, oxidation and decarbonization occur at the same time; because solid carbon of iron has strong affinity with oxidative gas, the carbon on the surface is first off. Generally, oxidative gas is from the outside furnace; meanwhile, scale of steel product surface, rust and residue of after cold drawn on the surface of pipe can decompose after boiling heat and generate some oxidation gas through reaction. So, we can control atmosphere on purpose in the furnace in order to avoid seamless steel tube surface decarbonization effectively.

Solving the problem of steel products and seamless tubes surface decarbonization, the key is on the heat treatment process. Due to decarbonization and oxidation of steel seamless pipes are occurred at the same time, as long as makes the pipes contact air as far as possible in the heat treatment process to reach the purpose of improving the decarbonization.

Some effective measures to prevent decarbonization:
1 When heating, reducing the heating temperature and residence time of artifacts as much as possible; choosing reasonable heating speed so as to shorten the total time of heating;
2 Control the appropriate heating atmosphere to make the neutral or adopt protective gas heating;
3 During the thermal stress process, if some accidental factors make production disrupt, it should reduce furnace temperature to recovery production; if long time pause, it will affect the quality of steel products.
4 When high temperature heating, the surface of steel products or seamless tubes will make full use of mulch and coating protection to prevent oxidation and decarburization.
5 Correct operations will make decarbonization layer remove during processing completely.
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