Why should the seamless steel pipe be pickled?

In the rolling of precision seamless steel tubes, especially in the production process of precision seamless steel tubes, how did the pickling process actually proceed? Today Raymond steel tube will soon unveil this mystery for you!

1. Summary of precision seamless steel pipe pickling

The method of removing oxide scale and rust from steel surface by acid solution is called acid pickling. Oxides of iron such as scale and rust (Fe3O4, Fe2O3, FeO, etc.) react with acid solution to form salts which are dissolved in acid solution and are removed. Sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid and mixed acid are used for acid pickling.

2. Commonly used medium for pickling seamless steel tubes:

Sulfuric acid, nitric acid, phosphoric acid and hydrofluoric acid. Acid pickling inhibitor must be added in acid pickling to prevent acid from corroding metal.

3. Acid cleaning process for precision seamless steel tubes

The main methods are pickling acid washing, spraying acid washing and acid ointment removing. In general, impregnation acid washing is widely used, and injection method can be used in mass production. Iron and steel parts are usually pickled in 10% to 20% (volume) sulfuric acid solution at a temperature of 40 degrees Celsius. When the iron content in solution exceeds 80g/L and ferrous sulfate exceeds 215g/L, acid pickling fluid should be replaced. It is not easy to overcorrosion and hydrogen embrittlement when steel is pickled with 20% - 80% (volume) hydrochloric acid solution at room temperature. Because of the corrosive effect of acids on metals, corrosion inhibitors are needed. After cleaning, the metal surface becomes silver white, and the surface is passivated to improve the corrosion resistance of stainless steel. In order to eliminate the adsorption on the surface of diatomite carrier and reduce the tailing of chromatographic peaks, the carrier should be treated by acid or alkali washing before use. Pickling is the carrier with 6mol/L hydrochloric acid soaking for 2 hours or concentrated hydrochloric acid heating soaking for 30 minutes, filtration, water washing to neutral, drying. Pickling can remove impurities such as Fe, Al, Ca and Mg on the surface, but can not remove silanol. Acid carrier is suitable for the analysis of acidic samples.

4. Effect of acid cleaning on precision seamless steel pipe

Oil and rust removal were carried out on the surface of precision seamless steel pipe in order to prepare for the next process treatment. In the production process, pickling process is to remove the surface oxide scale, after lubrication treatment (carbon steel - phosphorus saponification, stainless steel - tallow lime, copper - aluminum tube - oil), with the old process - copper plating), and then drawing deep processing. If the steel pipe is not pickled, the surface may have oxides and oil stains, phosphating solution nuclear energy can not remove them, phosphating quality will be reduced.