Pickling process of cold rolled strip
In addition to the task of removing the iron oxide scale on the strip surface, the continuous pickling line still has several functions:(1) trim the side of the strip with a disc shear.(2) regulating the quality of rolled steel, according to the production requirements of large volume of hot-rolled steel will be divided into small volumes, or several small steel coils merging into a large, in order to improve the production of cold rolling mill.(3) check and eliminate the harmful surface defects of strip steel after each process.(4) apply a layer of oil on the surface of the pickled steel strip, which can prevent rust and lubricate.
The continuous pickling line is divided into 3 sections according to the nature of the work:Inlet section: feeding, unwinding, strip surface, iron oxide crushing, straightening, shearing, shearing and welding;Pickling section: acid washing, hot and cold washing and drying;Exit section: shearing, oiling, and final take-up (take-up).
The pickling section can be divided into two ways: sulfuric acid pickling and hydrochloric acid pickling, but because hydrochloric acid pickling has more advantages, we can explain it by the acid washing mechanism of hydrochloric acid.The chemical reaction between hydrochloric acid solution and iron oxide scale is:FeO + 2HCl = FeCl2 + H2OFe2O3 + 6HCl = 2FeCl3 + 3H2OHydrochloric acid solution can quickly dissolve all kinds of oxide scales, pickling reaction can be carried out from the outer layer. Hydrochloric acid pickling is mainly chemical corrosion, and hydrochloric acid pickling is very harmful to metal matrix. Therefore,The structure is not sensitive to the efficiency of acid pickling of iron oxide scales, and the steel surface after pickling clean silver. The rate of acid washing reaction is closely related to the degree of cracking of strip iron before picklingOff.
Pickling process of cold rolled strip:Strip steel must be pickled before cold rolling, in order to remove the oxide scales on the surface of the steel coil which is harmful to the cold rolling, because the iron oxide sheet will damage the roller surface in cold rolling, and lead to defects on the strip surface. The most commonly used is continuous pickling of strip steel. The advanced cold rolling mill adopts continuous pickling line or Push-pull Pickling at high speed. Taking continuous pickling as an example, pickling is carried out continuously through several pickling tanks. To make the job line process continuous, the front end of a hot strip coil and the rear end of a steel coil are welded together. After pickling, the strip is cut and rolled according to the required roll weight and reel diameter.
