In the forging production process, the metal blank needs to be heated to a high temperature, steel reacts with oxygen on the billet surface, which will generate a layer of scale. If it can’t be removed before forging production, some pits may occur on the surface, which not only affects the appearance quality, but also reduces local strength, if these pits appear on machined parts of forging, will also reduce machining allowances, and have the risk of processing scrap.