Why pickle process for seamless steel pipe?
In the rolling of seamless steel pipes, especially in the production process of precision seamless steel pipes, how does that pickling process proceed? As a professional supplier of steel pipes, flanges and fittings, we will unveil this mystery for you!
1.Overview of precision seamless steel tube pickling
The method of removing scale and rust on the surface of steel with an acid solution is called pickling. Oxides such as Fe3O4, Fe2O3, FeO and the like react with the acid solution to form salts dissolved in the acid solution and removed. Pickling acids include sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid and mixed acids.
2.Common media for pickling of precision seamless steel pipes:
Sulfuric acid, nitric acid, phosphoric acid, and hydrofluoric acid. When pickling, be sure to add a pickling inhibitor to prevent acid from corroding the metal.
3.Precision seamless steel pipe pickling process
There are mainly immersion pickling method, spray pickling method and acid paste rust removal method. Generally, the dipping and pickling method is commonly used, and the spray method can be used in mass production. Steel parts are generally pickled in a 10% to 20% (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 pickling solution should be replaced.At normal temperature, the steel is pickled with a 20% to 80% (volume) hydrochloric acid solution, which is less prone to over corrosion and hydrogen embrittlement. Because acid has a great corrosive effect on metals, it is necessary to add a corrosion inhibitor.
After cleaning, the metal surface becomes silver-white, and at the same time, the surface is passivated to improve the corrosion resistance of stainless steel.In order to eliminate adsorption on the surface of the diatomite support and reduce chromatographic peak tailing, the support needs to be acid-washed or alkaline-washed before use. For pickling, the carrier is immersed in 6mol / L hydrochloric acid for 2h or concentrated hydrochloric acid for 30min, filtered, washed with water to neutrality, and dried. Pickling can remove impurities such as iron, aluminum, calcium, and magnesium on the surface, but it cannot remove silanol groups. Pickled carriers are suitable for the analysis of acidic samples.
4.Effect on pickling of precision seamless steel pipes
Degrease and rust the surface of precision seamless steel pipes to prepare for the next process. In the production process, the pickling process is to remove the oxide scale on the surface, and then subject to lubrication treatment (carbon steel-phosphorus saponification, stainless steel-tallow lime, copper-aluminum pipe-oil coating), and the old process-copper plating), and further drawing processing. If the steel pipe is not pickled, the surface may have oxides and oil stains, which cannot be removed by the nuclear energy of the phosphating solution, and the phosphating quality will be reduced.
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