Shot blasting treatment is the process of using the centrifugal force of the impeller on the shot blasting machine during high-speed rotation to shoot the steel sand of the shot blasting machine at a high linear speed onto the surface of the processed metal, stone, road surface, glass and other workpieces, producing impact and grinding effects, removing impurities such as oxide skin, rust, floating ash, and producing a certain degree of roughness on the surface of the workpieces.

Common scope of shot blasting treatment:

Steel plates, stones, pipes, steel bars, discs, road surfaces, hardware accessories, automotive parts, castings, and so on, almost all cast steel parts, gray castings, malleable iron parts, ductile iron parts, etc. need to undergo shot blasting treatment.

Types of shot blasting equipment:

Through type shot blasting machine, track type shot blasting machine, hook type shot blasting machine, suspension chain type shot blasting machine, road surface shot blasting machine, stone shot blasting machine, wire shot blasting machine, steel plate shot blasting machine, pipeline shot blasting machine, steel pipe shot blasting machine, etc

Common shot blasting materials for shot blasting treatment:

Steel shot, aluminum shot, ceramic micro powder, steel sand, walnut sand, corn cob, glass beads, resin sand, plastic sand, etc.

Development history of shot blasting:

Shot blasting is a surface treatment method that has been applied in developed countries in Europe and America* The previous shot blasting machine was born 100 years ago and was initially used to remove impurities, oxide scales, and increase roughness on various metal or non-metal surfaces.

Introduction to shot blasting process:

1、 Purpose: Shot blasting can prevent high residual tensile stress on the surface of parts, generate compressive stress, and improve their fatigue strength.

2、 Scope of use: Generally, steel parts are used at temperatures exceeding 260 ℃, while aluminum parts are used at temperatures exceeding 170 ℃ and do not require shot blasting treatment. Because the use temperature is too high, the compressive stress generated by shot blasting will be eliminated and the expected effect will be lost.

3、 Process:

1. Selection of Pill Types:

(1.) The hardness of cast steel shot is generally HRC40-50. When processing hard metals, the hardness can be increased to HRC57-62. Cast steel pellets have good toughness and are widely used, with a service life several times that of cast iron pellets.

(2.) The hardness of cast iron shot is generally HRC58-65, which is brittle and easy to break, has a short service life, and is widely used. It is mainly used in situations where high shot blasting strength is required.

2. Selection of shot blasting size:

(1.) The shot blasting particle size is generally selected between 6-50 mesh, and the higher the shot blasting strength requirement, the relatively larger the shot blasting particle size.

(2.) The selection of shot blasting size is also limited by the shape of the shot blasted parts, and its diameter should not exceed half of the circular diameter inside the groove. Generally, the larger the shot blasting, the greater the impact energy, and the stronger the shot blasting intensity, but the coverage rate of shot blasting decreases. Therefore, it is advantageous to minimize the size of shot blasting while producing the required shot blasting intensity.

3. Selection of shot peening hardness

The hardness of shot blasting is generally greater than that of the parts. When its hardness is greater than the hardness of the part, the change in shot peening hardness value does not affect the shot peening strength. On the contrary, a decrease in the hardness value of shot blasting will result in a decrease in shot blasting strength.

4. The selection of shot blasting speed: Increasing the shot blasting speed will increase the shot blasting intensity, but if the speed is too high, it will increase the amount of shot blasting fragmentation. Shot blasting consumption has increased.

5. Adjustment of ejection angle

When in a vertical state, the shot blasting intensity is high, so shot blasting treatment is generally carried out in this state. If it is limited by the shape of the parts and it is necessary to shot at a small angle, the shot size and speed should be appropriately increased.

6. Crushing amount of shot blasting

The intensity of shot blasting is low, so it is necessary to regularly remove the broken shot, and the completeness rate of shot blasting should not be less than 85%.

7. Shot blasting time

The amount of shot blasting time depends on the shot blasting effect generated by the workpiece during the shot blasting process, and the principle is to achieve the required shot blasting intensity. (Usually around 30 minutes)

Additionally, it should be noted that shot peening strength is currently mostly measured using the Almen arc height meter as described in the American SAE standard J442. The Almen arc height gauge is made of standard size 70 carbon steel with a thickness of 0.8, 1.3, or 2.4mm and a hardness of HRC44-50. The sample is fixed on a special fixture, and one side is shot blasted. Then, the arc height of the bent steel bar sample is measured using the arc height gauge to obtain the shot blasting strength.