Steel pickling is a treatment used to remove impurities, rust, and scale from a surface. Scale forms on the surface of the material during hot working processes. To prepare it for further processing, the steel must be pickled first. After cold rolling, the steel must be pickled again to restore the best corrosion-resistant properties.
How Is Steel Pickled?
Steel pickling may be done through a variety of methods. To see the technique used in a specific plant, you must ask the plant personnel. Some plants use a tank, while others use a tumbler. Other plants use a combination of both methods.
When using a tank, the steel is placed in a tank that contains an alkaline solution. The steel is kind of “bathed” in this solution for about 30 to 60 minutes. Tanks are usually heated and cooled to speed up the process.
Tumblers are used for pickling the steel. They were originally designed to remove the acidity from steel, hence their name. However, the process of steel pickling has evolved. Tumblers use a belt to agitate the steel. The belt moves at high speed with a constant downward motion. This downward motion brings the steel in contact with the alkaline solution. The steel can be bathed in the solution for a matter of minutes.
What Is The Effect Of The Pickling Process?
The pickling process removes impurities from the surface of the steel. The impurities may be in the form of rust, scale, chalk, or mill scale. These impurities are removed from the surface of the steel through the use of an alkaline solution.
Typically, the steel will be darker in color after being pickled. This is due to the fact that the pickling solution removes rust and impurities, which lighten the surface. Pickled steel is generally blue in color.
After the steel has been pickled, the process must be followed by a de-rusting process and then a rust-proof coating.
What Is The Effect Of The Pickling Process On The Properties Of Steel?
The pickling process causes the following changes to the properties of the steel:
- decrease in strength
- decrease in ductility
- decrease in hardenability
What Are Some Examples Of Pickling?
There are a few examples of steel pickling:
- The Twin Towers’ steel was pickled to remove the rust, mill scale, and other impurities.
- Pickling must be followed by a de-rusting process and then a rust-proof coating.
- Steel that comes from a mill is usually pickled again because it is pickled on arrival at the mill.
- Hot working processes, such as hot rolling, lead to scale formation. If a steel product is pickled, the scale will be removed from the surface.
- Smaller pickling machines are used in cars to restore their finish.
Conclusion
In conclusion, steel pickling is used to remove impurities, rust, and scale from the surface of a steel part or product. The removal of rust, scale and other impurities is done using an alkaline solution. The steel should be pickled before it is further processed. Pickled steel is generally blue.
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