Do you really know what shot blasting is? What are the advantages and disadvantages?

Many have heard the term shot blasting, but what exactly is shot blasting and what are the benefits of shot blasting?

What is Shot Blasting?

Manufactured metal parts aren't ready for use right out of the mould. They often need a coat of paint, powder coating, or welding work. But before this can happen, the surface of the metal part must be clean.

Shot blasting prepares metal parts for further processing like painting or powder coating. This step is necessary to ensure the coat adheres properly to the part. Shot blasting can clean off contaminants like dirt or oil, remove metal oxides like rust or mill scale, or deburr the surface to make it smooth.

How Shot Blasting Works?

Shot blasting involves shooting a high-pressure stream of abrasive material (also known as shots or blasting media) against the surface of a metal part. Depending on the application, the shots may be propelled by a pressured fluid (like compressed air) or a centrifugal wheel (known as wheel blasting).

The shape, size and density of the shots will determine the final results. Types of metal abrasives used in shot blasting include steel grit, copper shots, and aluminum pellets. Other methods of shot blasting use silica sand, glass beads, synthetic materials like sodium bicarbonate (baking soda), and even agricultural materials like crushed kernels.

But sometimes we find that the casting surface will be blackened after shot blasting. Black spots on the surface can be removed, but it is difficult to treat those that have been immersed in the casting matrix.

The reasons for this are as follows:

1. Defects before shot peening brought by die casting process;

(1) excessive use of black oil in die casting;

(2) Punch oil splashing during die opening;

(3) Paint splashing during die casting;

2. The product is placed in wet temperature or time, and the surface is corroded, mildewed or dusty.

3. The dust removal device of shot peening machine is invalid, and the steel shot contains more dust.

4. The operator did not wear gloves according to the requirements, and directly touched the surface of the casting after shot peening with his hands, resulting in fingerprints.

5. After shot peening, it will be put for a long time. The surface will be covered with dust or splashed with water and oil. The environment will be humid and oxidized.

When the above situation occurs, corresponding measures should be taken:

1. Defects do not cover the whole casting surface. Control and management should be strengthened by die casting process.

2. After shot peening, the surface trace is shallow and can not be removed because it has been immersed in the casting matrix. The management of product placement should not be too long. If it needs to be placed for a long time, it must be covered and protected in suitable environment.

3. The surface color of the whole casting is black and dark. Restore dust removal or replace new steel balls;

4. Operators must be required to follow the operation instructions. Gloves must be worn.

5. Shot peening should be finished, packed and stored as soon as possible. If it needs to be stored for a period of time, strict protection must be carried out.