In the process of steel plate production, there are three processes that produce oxide scale.

(1) Before hot rolling, the slab is heated and insulated in a heating furnace (1200-1250℃) to produce a primary oxide skin.The primary scale consists of a dense outer layer and a loose inner layer.

(2) After hot rolled slab comes out of the heating furnace, it is roughed after removing the primary oxide skin by high-pressure water.In the process of roughing and finishing rolling for a short time, the secondary oxide skin is red scale layer, which is composed of particles such as square iron ore (FeO) and hematite (Fe2O3). This oxide layer is thinner in thickness, and the interface stress between steel plate and scale is small, so the peeling property is poor.

3) During the cooling process after finishing rolling, the oxide scale is generated three times and kept at room temperature.The scale in the surface quality of hot rolled coil product is basically three times scale.If the secondary iron oxide sheet cannot be removed in the rolling process, it will form iron oxide sheet pressing defect in the rolling process. The iron oxide sheet is dark brown, boat shape and scattered on the surface of the defective steel sheet.Under the condition of continuous cooling, due to the influence of final rolling temperature, final cooling temperature, reddening temperature and cooling speed, the oxide layer with different composition will eventually be formed.

As the raw material of cold rolled strip steel, hot rolled steel sheet needs descaling before cold rolling.Pickling is often used to eliminate scale, but pickling can cause damage and pollution.Therefore, it is necessary to find an alternative acid-free descaling technology, which is generally common in the following categories:

1. Sand blasting method

2. Shot blasting

3. Abrasive water shooting scale method