In the rolling of seamless steel tubes, especially in the production process of precision seamless steel tubes, how does the acid pickling process proceed? Today, the mysterious veil is unveiled for you!
The use of an acid solution to remove scale and rust from steel surfaces is called pickling. Iron oxides (Fe3O4, Fe2O3, FeO, etc.), such as scales and rust, chemically react with the acid solution to form salts that are dissolved in the acid solution and removed. Pickling acids include sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, and mixed acids.
Mainly impregnated pickling, jet pickling and acid paste rust removal. In general, the impregnation pickling method is generally used, and the spray method can be used in mass production. Steel parts are generally pickled in 10% to 20% (by volume) sulfuric acid solution at a temperature of 40°C. When the iron content in the solution exceeds 80g/L and the ferrous sulfate exceeds 215g/L, the acid solution should be changed. At room temperature, pickling of steel with 20% to 80% (by volume) hydrochloric acid solution is not prone to over-corrosion and hydrogen embrittlement. Due to the great effect of acid on metal corrosion, corrosion inhibitors need to be added. After cleaning, the metal surface becomes silver white, and the surface is passivated to improve the corrosion resistance of the stainless steel.
In order to eliminate the surface adsorption of the diatomaceous earth carrier and reduce the tailing of the chromatographic peaks, the carrier must be acid-washed or alkali-washed prior to use. Pickling is carried out by dipping the carrier with 6 mol/L hydrochloric acid for 2 hours or heating with concentrated hydrochloric acid for 30 minutes, filtering, washing with water to neutrality, and drying. Pickling removes impurities such as iron, aluminum, calcium, and magnesium on the surface but does not remove silanol groups. Pickling supports are suitable for the analysis of acidic samples.
Degreasing and derusting the surface of precision seamless steel tubes to prepare for the next process. In the production process, the pickling process is to remove the surface oxide skin, after the lubrication treatment (carbon steel – phosphorus saponification, stainless steel – tallow lime, copper aluminum – oiled), with the old process – copper plating), and then Carry out deep processing. If the steel pipe is not pickled and there may be oxides and oil on the surface, the phosphating solution cannot remove them and the quality of phosphating will be reduced.