How to choose different metal abrasives?
Metal abrasive is a material with a sharp and hard surface. It is used to grind the surface of softer materials and is a mechanical surface metal treatment material. According to the particle shape, there are three types: shot, sand and column. Metal abrasives have a direct impact on the cleaning efficiency, cleaning cost and cleaning quality of steel surfaces. In the steel structure shot blasting and sand blasting process, the basis for the selection of metal abrasives is:
1. According to the ISO8501 standard, investigate the original state of the steel surface. For thicker steel plates with serious corrosion above grade C, abrasives with large mass and high hardness should be selected.
2. Select abrasives based on the cleanliness standards and roughness size specified in the coating design. The cleanliness level is high, the particle size and density of the abrasive should be moderate, and the specified roughness is large, and the particle size of the abrasive should be large.
3. According to the surface treatment method and equipment, for example, for steel shot and steel sand used in the shot blasting line, the particle size is 1.0~1.2mm** is appropriate; for copper slag used in open sandblasting equipment, the particle size is 0.6~1.8mm.
4. The type of coating and the specified film thickness and thickness are also the basis for the selection of abrasives. Because different types of primers have different requirements for the cleanliness and roughness of steel, especially when using alcohol-soluble inorganic silica primers, angular steel sand is used for sandblasting to increase the bite ability of the roughness to the primer. Generally, the roughness is controlled at one-third of the coating thickness.
When selecting abrasives, the following factors should be considered:
1. Particle size. Among the same type of abrasives, the larger the particle size, the stronger its cleaning ability. On the contrary, the smaller the particle size, the faster the speed decreases, and the weaker its cleaning ability.
2. Shape. The shape of the abrasive particles determines the shape of the steel surface after shot blasting.
3. Hardness. The hardness of the abrasive must be greater than the hardness of the steel surface.
4. Density. The density of abrasive is related to the recovery rate of abrasive. The higher the density, the higher the recovery rate. For example, quartz sand can only be used once, copper slag and other slag can generally be used three times, and steel sand and wire cut shot can be used more than 100 times.
5. Abrasives should be free of oil, dust, and moisture. Using contaminated abrasives will cause coating failure and early damage to the coating. In the coating of steel structures, there are strict requirements on the chlorine content in the abrasive.
