The convective heating more effectively breaks down stresses that are present in the part [caused by the manufacture of the steel/semi-finished product and cutting/shaping work] due to the more uniform heating. This is a pre-requisite for low distortion heat treatment. alarge temperature difference develops between the surface and the core. After 15 minutes the temperature difference is > 250°C. a slight temperature difference with the respect to the surface. After 15 minutes the temperature difference is < 100°C.