Analysis of commonly used abrasives for shot blasting machines
1) The commonly used abrasives for casting shot blasting include steel shot, steel grit, and steel wire cut shot. The characteristics of each product are as follows:
Steel shot: It is the most commonly used abrasive for cleaning castings, but because the metal abrasive industry is not standardized enough, the quality of steel shots on the market is uneven, and it is difficult to judge the quality of steel shots only through visual inspection. Quality steel shots not only bring higher consumption costs, but also reduce cleaning efficiency and increase equipment maintenance, dust removal, and labor costs.
Steel grit: In recent years, in order to improve cleaning quality and cleaning efficiency, and reduce labor costs, European and American foundry companies have used a mixture of steel shot and steel grit to clean castings, making full use of the respective advantages of steel shot and steel grit, and have achieved Very good results. Now some sole proprietorship or joint venture casting companies in China have also used steel grit for cleaning. The effect is very good, but the quality of steel grit is high, especially for the hardness, particle shape and gold of steel grit. The phase organization is very demanding.
Cut wire shot: Most of the cut wire shots in the domestic market are cut from scrap tire steel wire or wire rope. Most casting companies that use cut wire shot feel that the cut wire shot has a longer life, but the wear of the cut wire shot is low. In addition to its lack of pores and other defects, it also has a lot to do with its relatively low hardness and small force during polishing. The biggest defect is the low quality of shot blasting caused by its irregular shape and large wear on the equipment. , And are non-standard products, mostly produced by small-scale family factories. It is difficult to provide users with long-term protection in terms of supply and quality control. Therefore, most application fields are gradually giving up the choice of using steel wire shot.
2) Aiming at the commonly used abrasives for cleaning—steel shot and steel grit, the following will analyze the impact on its performance from its various indicators:
⑴ Abrasive material: The material is the most important factor affecting the quality of the abrasive. The use of high-quality raw materials, high-end smelting technology, and the addition of sufficient alloy components can obtain excellent materials. If the abrasive material is not good enough, it will directly reduce its Common quality problems for service life and use effect are: too high carbon (C) content, too low silicon (Si), manganese (Mn) alloy element content, too high sulfur (S) and phosphorus (P) harmful elements, etc. In particular, the content of harmful elements has a greater impact on performance and should be as low as possible.
⑵ The hardness of the abrasive: the hardness of the abrasive should be as high as possible, at least higher than HRC5-10 on the surface of the casting. High-hardness abrasives can clean the castings more thoroughly and improve the cleaning efficiency, but it must ensure higher internal quality to To ensure that the abrasive has sufficient resistance to crushing even under high hardness, many abrasive manufacturers make the hardness of the abrasive very low to create the illusion that the abrasive is not easy to break and the consumption is low, but it is not worth the loss for use, due to the low hardness of the abrasive , The kinetic energy of the shot blasting is completely absorbed by the deformation of the abrasive particles, and the surface of the casting cannot be cleaned well. It will also cause the increase of labor and kinetic energy costs due to the low cleaning efficiency.
⑶ The particle size of the abrasive, that is, the particle size of the abrasive. The particle size of the abrasive should be moderate, the particle size is too small, the roughness is small, but the impact force is small, which is easy to cause incomplete cleaning and low cleaning efficiency; the particle size is too large, the impact of a single particle is large, but it is cast on the casting per unit time The number of particles is small, which reduces the cleaning efficiency and increases the roughness.
⑷ Abrasive life: The life is the comprehensive performance of the abrasive. In the shot blasting process, the consumption of normal steel shots is a gradual wear process. In the repeated impact process, the steel shot will deform once after each impact. The surface will peel off a layer. The shape of the steel shot in use is a polygon like a football. The impact effect of each angle on the casting is equal. It will become smaller in use, and will be sucked away by the dust collector when it reaches a certain level. The process of reducing the quality of the steel shot is slower, and the low-quality steel shot will quickly become smaller, and even after a few times of beating, it will break and quickly become powdery, with poor material, hardness, and metallography. These are all reasons for the production of low-quality abrasives. Low-quality abrasives will inevitably bring higher shot blasting costs, lower cleaning speeds and greater dust pollution.
⑸ The kinetic energy of the abrasive: the force of the abrasive, which is related to the quality of the abrasive and the shot blasting process. As far as the abrasive is concerned, higher hardness and density and denser metallographic structure can make the abrasive have a Higher kinetic energy, resulting in greater force at work. The combination of longer life and greater kinetic energy is the manifestation of high-quality abrasives. According to the basic requirements of casting cleaning and the characteristics of abrasives, it is difficult for a single type and model of abrasives to meet higher cleaning requirements, especially considering the cast Cleaning costs, efficiency and environmental requirements are getting higher and higher. Therefore, when selecting high-quality abrasives, we should also pay attention to different types and reasonable mixing ratios of different types of abrasives. The use of high-performance mixed abrasives is also in many surface treatment fields around the world. Application trends.