Surface Cleaning in Forging Production

Sometimes, in order to reduce die wear, avoid oxide scales pressing into forgings, or prevent existing surface defects from expanding during forging, raw materials and intermediate blanks should also be cleaned up. The methods of removing local surface defects of forgings with raw materials and intermediate blanks are as follows:
(1) Wind shovel cleaning; 
(2) Grinding wheel cleaning ; 
(3) Flame cleaning. 
After cleaning, the grooves on the surface of the workpiece should be smooth and the width-height ratio of the grooves should be greater than 5.

There are three ways to clean the oxide scale of hot billet before forging:
(1) Tool clearance. The method of removing oxide skin with wire brush, scraper, scraper wheel and other tools.
(2) High-pressure water cleaning. The heated billet is sprayed from all sides to the billet at a speed of 0.2-0.5m/s through the high pressure water injection device. The oxide skin on the billet surface shrinks sharply and cracks when it is cold, and is quickly washed away by high-pressure water. Because the process time is very short, the temperature drop of the billet itself is very little, the cleaning effect is good and the efficiency is high.
(3) Billet removal. The oxide skin of some hot billets can be removed by using the blank-making step in hammer forging.

After forging or heat treatment, there are four kinds of cleaning methods widely used in production: drum cleaning, sand blasting cleaning, shot blasting cleaning and pickling. 
(1) Drum cleaning 
In a rotating drum, forgings are collided or ground with each other to remove oxide and burrs on the workpiece. The method is simple in equipment and convenient in use, but it has high noise. It is suitable for medium and small forgings.
(2) Sandblasting (shot) cleaning
Sandblasting or shot blasting are powered by compressed air. The working pressure of sand blasting is 0.2-0.3 MPa. The working pressure of shot blasting is 0.5-0.6 MPa. The quartz sand with 15-2 mm particles or the steel shot with 0.8-2 mm particles are sprayed onto the forgings through nozzles to remove oxide scales. Generally speaking, efficiency is low.
(3) shot blasting cleaning
Relying on the centrifugal force of the high-speed rotating impeller, the steel shot is projected onto the forging to remove the oxide scale. Commonly used steel pellets contain 0.5%-O.7% carbon and 0.8-2mm diameter. They are usually cast steel pellets and cut steel wire pellets. Shot blasting can also eliminate surface stress and micro-cracks while knocking down oxide scales. And can play a strengthening role. For the forgings quenched or tempered, the degree of processing strengthening is more obvious. The method is efficient, effective and noisy.
(4) acid cleaning
The pickling solution used for forgings of carbon steel and alloy steel is sulfuric acid or hydrochloric acid. The removal of oxidized skin mainly depends on the dissolution of oxidized skin itself in hydrochloric acid solution. The reaction of base metal with hydrochloric acid is much slower than that of oxide skin with hydrochloric acid. Acid cleaning has good effect and high efficiency, but it pollutes the environment greatly.