Discuss the differences between shot blasting and sandblasting

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1. Shot blasting: Shot blasting involves using a high-speed rotating impeller to throw small steel or iron pellets at the surface of a part, causing them to impact that surface at high speed; this process enables the removal of the oxide layer on the part’s surface. At the same time, steel or iron pellets strike the surface of the part at high speed, causing the lattice structure on the surface to become distorted and deformed, which increases the surface hardness. This is a method for cleaning the surface of parts; shot blasting is often used to clean the surface of castings or to strengthen the surface of parts. Grenade blasting is generally used for irregular shapes, etc.; several nozzles are used together in various directions, resulting in high efficiency and low pollution. However, both shot blasting and sandblasting can use compressed air. Of course, blasting doesn’t necessarily require a high-speed rotating impeller. In the ship repair and construction industry, shot blasting (using small steel pellets) is generally used for the pre-treatment of steel plates (rust removal before painting) ； Sandblasting (mineral sand is used in the shiprepair and shipbuilding industries) is commonly applied to finished ships or ship segments, with the purpose of removing old paint and rust from the steel plates so that they can be repainted. In the ship repair and construction industry, the main purpose of shot blasting and sandblasting is to improve the adhesion of paint to steel plates. 2. Sandblasting: Sandblasting uses compressed air as a driving force to propel sand with a particle size of 40–120 mesh or pellets of about 0.1–2.0 mm toward the surface of the workpiece, thereby achieving the same effect on it. The size of the pellets varies, which affects the degree of treatment achieved. Shot blasting can also serve a strengthening purpose. Currently, equipment in China has fallen into a misconception, believing that only shot blasting can achieve strengthening. Sandblasting is a method that uses compressed air to blow quartz sand at high speed in order to clean the surface of parts. Often used for rust removal from part surfaces ； Surface treatment of parts (small wet sandblasters available on the market are used for this purpose; the sand particles are usually corundum, and the medium is water). Sandblasting is used for parts with complex shapes; it is easy to perform rust removal manually, but the efficiency is low, and the working conditions are poor, resulting in uneven rust removal. Typical sandblasting machines come with sandblasting guns of various sizes, and as long as the chamber is not extremely small, it is possible to fit a gun inside to clean it. The accompanying product for pressure vessels – the end caps – have their surface oxide scale removed by sandblasting; the diameter of the quartz sand used is between 1.5 mm and 3.5 mm. There is a processing method that uses water as a medium to propel emery particles for processing parts, and this is also a form of sandblasting. Both shot blasting and sandblasting can be used to clean and remove contaminants from workpieces, with the aim of preparing them for subsequent processes. This is done to ensure that the roughness requirements of the next processing step are met; in some cases, it is also necessary to achieve surface consistency. Shot blasting has a strengthening effect on the workpiece, while this effect is less noticeable with sandblasting. Generally, shot blasting uses small steel balls, while sandblasting uses quartz sand. Divided into sections according to different requirements.