Pickling process of seamless steel pipe

During the rolling process of seamless steel tube, especially precision seamless steel pipe, the pickling process is very important. It can remove the oxide scale and rust on the surface. How does it happen?

The method of removing the oxide and rust on the surface of steel by acid is called acid washing. The oxide of iron (mill scale, rust) has a chemical reaction with the acid solution, which forms the salts dissolving in the acid solution and is removed. Sulfuric acid, hydroelectric acid, phosphoric acid, nitrite acid and other mixed acid are used for acid pickling. In pickling, be sure to add acid corrosion inhibitor to prevent the corrosion of the acid on the metal.

The main methods include dipping acid washing, spray pickling and acid ointment derusting. General use of dipping acid washing, spray pickling can be adopted in mass production. Steel parts are usually pickled in 10% ~ 20% (volume) sulfuric acid solution at a temperature of 40 degrees. When the iron content in the solution is more than 80g/L and the ferrous sulfate is more than 215g/L, the acid lotion should be replaced. At normal temperature, 20% ~ 80% (volume) hydroelectric acid solution is used for acid washing of steel. It is not easy to cause corrosion and hydrogen embitterment. As acid has a great corrosion effect on metal, it is necessary to add corrosion inhibitor. After cleaning, the surface of the metal is silver white, and the surface is passivized to improve the corrosion resistance of the stainless steel. In order to eliminate the surface adsorption of diatomite carrier and reduce the tail of cinematographic peak, the carrier should be treated with acid washing or alkali washing before use. Pickling is the use of 6mol/L hydroelectric acid soak 2H or concentrated hydroelectric acid to boil 30min, filter, wash with water to neutral, drying. Pickling can remove impurities such as iron, aluminum, calcium and magnesium on the surface, but can not remove the silanol. Acid pickling carrier is suitable for the analysis of acid samples.

The surface of the precision seamless steel pipe is deoiling and derusting, so as to prepare for the processing of the next process. In the process of production, the process of pickling is to remove the surface oxidation skin, after the lubrication treatment, the old process - copper plating), and then drawing deep processing. If the steel pipe is not washed, the surface may have oxide and oil pollution, the photostatting solution can not remove them, and the quality of photostatting will be reduced.