At what temperature will the steel pipe begin to decarburize when annealed?

Decarbonization is not only related to temperature, but also depends on the type of metal or alloy, and depends on the heating medium. For example, silicon steel is easy to decarbonize, stainless steel is not easy to decarbonize, heat-resistant steel is not easy to decarbonize, if it is a reducing medium, you heat to the melting state will not decarbonize, if it is an oxidizing medium, it mainly depends on the level of oxidation, if it is heated in the air, the decarbonization situation is more difficult to say, only specific problem specific analysis, general carbon steel about 570 Degree produces strong oxidation decarburization.

Decarbonization or not has a lot to do with chemical composition, heating temperature, holding time, the existence form of carbon in the metallographic organization, and environmental atmosphere. Chemical composition alone cannot determine the heating temperature required to decarbonize the surface of the material.

The surface decarburization of steel materials is related to the carbon content or carbon equivalent. Taking 60Si2Mn as an example, the decarburization sensitive zone is about 1150-1250 degrees.

Decarbonization is also related to the heating atmosphere and heating time.

Another thing to consider is that oxidation and decarbonization generally exist at the same time, if the oxidation rate is greater than decarbonization, then even in the high temperature zone will not cause material decarbonization, but the surface oxide thickness increases. 35CrMo is generally used for the production of high-strength fasteners, which generally requires the spinning temperature not to exceed 880 degrees, the cooling speed in the range of 0.8-0.85 degrees /s, and the decarburization layer can be controlled between (0.2-0.4)D%. This decarbonized layer is tolerable and subsequent cold heading and mechanical properties can be guaranteed.