How to improve the cleanliness of cold rolled plates

With the development of the market, users of cold-rolled strip steel not only pay attention to the dimensional accuracy and mechanical properties of the products, but also put forward higher and higher requirements for the surface cleanliness of cold-rolled steel plates. Cold-rolled sheet mills at home and abroad have conducted a series of explorations on the surface cleanliness of steel plates, mainly studying the rolling process and annealing process.

The spots on the surface of cold-rolled plates mainly refer to rust spots and emulsified spots. Corrosion can be divided into two types: yellow spots and black spots. The main condition for producing yellow spots is the chemical reaction between strip steel and hydrochloric acid, air and water to generate iron compounds; while the main chemical component of black spots is iron powder, because the heat treatment is a full hydrogen mask. In type annealing, H is used as a reducing atmosphere during annealing, and FeO(OH)3 is reduced to iron to form iron powder. Emulsification spots occur because the iron powder particles on the surface of the rolled strip absorb a large amount of concentrated oil, and the iron powder particles are wrapped into an oil film. The water vapor in the oil film forms a chemical reaction with the iron powder particles. to produce iron oxide. There are gaps between the iron powder particles, causing water vapor to oxidize with the additives and the steel plate. The oxidized part of the board surface forms a loose iron oxide layer. Emulsified spots are formed in the iron oxide layer of the body. The surface treatment process of cold rolled plates is crucial to improving the quality and corrosion resistance of the product. Pickling, pickling and oiling, galvanizing and spraying are common cold-rolled plate surface treatment processes. Each process has its applicable scenarios, advantages and disadvantages. When performing surface treatment of cold-rolled plates, it is necessary to select an appropriate process according to specific needs to ensure that the cold-rolled plates have good surface quality and corrosion resistance and meet various application requirements.