Thermal Descaling
A process in which components are heated in furnace atmospheres or by flame action to blast off scale layers through thermal stresses. This prepares the material for subsequent pickling steps.
When thermal descaling, you heat the workpiece so much that the scale layer flakes off due to the different thermal expansion of metal and scale. Then you remove the loose residue mechanically, e.g. with a wire brush or by quenching. If you don't get the scale off cleanly before welding, you'll get pores and poor bonding in the weld. But be careful not to leave the material in the oven too hot or too long, otherwise you'll strip its structural properties and it'll become soft or brittle. For the right temperature and holding time, you have to go by the material and the part thickness—there's no one-size-fits-all setting.