Difference between sandblasting and shot blasting

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The difference between sandblasting and shot blasting: Shot blasting uses 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 parts 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 objects with regular shapes; several nozzles are used together in various directions, resulting in high efficiency and minimal pollution. In the shipbuilding industry, shot blasting and sandblasting are commonly used. However, both shot blasting and sandblasting 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. In fact, the cleaning of cast parts doesn’t rely solely on shot blasting; for large pieces, drum sanding is usually performed first. This involves removing the risers from the cast part and placing it inside a drum, where the parts collide with each other, allowing most of the sand on the surface to be removed before proceeding with shot blasting or bead blasting. The size of the shot pellets is 1.5 mm. Studies show that, in terms of damage, it is much easier for tensile stress to occur on the surface of metal materials than compressive stress. When the surface is under compressive stress, the fatigue life of the material **increases**. Therefore, for components prone to fatigue fracture such as shafts, shot peening is often used to create compressive stress on the surface in order to extend the product’s lifespan. Additionally, metal materials are very sensitive to tension; this is why the tensile strength of materials is much lower than their compressive strength. It is also for this reason that the mechanical properties of metal materials are generally expressed in terms of tensile strength (yield strength, tensile strength). The working surface of the steel plates in the cars we use on a daily basis is strengthened through shot blasting, which can significantly improve the material’s fatigue resistance. Shot blasting involves using a motor to rotate an impeller; through centrifugal force, shot particles with diameters ranging from 0.2 to 3.0 mm (such as cast shot, cut shot, or stainless steel shot) are thrown at the surface of the workpiece. This process gives the workpiece a certain level of roughness, enhancing its appearance, or it can change the welding tensile stress in the workpiece to compressive stress, thereby increasing its service life. It is used in almost all fields of machinery, such as shipbuilding and repair, automobile parts, aircraft components, the surfaces of guns, tanks, bridges, steel structures, glass, steel plates, pipes, and so on. Sandblasting (using beads) involves using compressed air as a power source to propel sand with a diameter of 40–120 mesh or beads around 0.1–2.0 mm at the surface of the workpiece, thereby achieving the same effect on it. The size of the pellets varies, which affects the treatment outcome. It is emphasized that 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. Enterprises use a combination of shot blasting and air jet blasting for reinforcement. Each has its own advantages. For workpieces such as gears, it is not possible to change the particle ejection angle in shot blasting; only the initial velocity can be adjusted using frequency conversion. However, shot blasting handles large volumes of material at high speeds, while blast cleaning is the opposite in this regard, resulting in less effective cleaning results compared to shot blasting. Sandblasting is a method that uses compressed air to blow quartz sand at high speed in order to clean the surface of parts. In factories, this process is also called sandblasting; it not only removes rust but also eliminates oil, which is very useful for painting. 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) ； In steel structures, using high-strength bolts for connections is a relatively advanced method. Since high-strength connections rely on friction between the mating surfaces to transmit force, high requirements are placed on the quality of these surfaces; therefore, sandblasting is necessary to treat them. 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 accessory 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 machining 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 processing – that is, to meet the roughness requirements of the next step in the manufacturing process. In some cases, the goal is also 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.