The chemical composition of medium frequency furnace is unstable, and some chemical elements are easy to over proof, and the content of carbon is relatively  high. So it is not suitable for deep processing. Second, because of the material reasons, the tube surface of medium frequency is easy to occur qualilty problem, such as peeling, pressing point, the light is dark. 

Refining furnaces and J3 are mainly of different carbon content, high carbon content, high hardness, brittle, they are not suitable for bending.