How to distinguish Shot Blasting Process and Sand Blasting Process

Details about shot blasting process

Shot blasting process is to use a high-speed rotating impeller to fling small steel or iron shots out and impact on the surface of the part at a high speed, so that the surface of the oxide layer can be removed. At the same time, the impact of steel shot or iron shot on the surface of the part at a high speed will cause the surface lattice distort and make the surface hardness increase, which is a method to clean the surface of the part. Shot blasting technology is commonly used to clean the surface of castings or strengthen the surface of parts.

Generally, shot blasting process is used for regular shapes. Several ramming heads work up, down, left and right together with high efficiency and low pollution.

Shot blasting and sand blasting processes are commonly used in ship repair and shipbuilding industries. However, both shot blasting and sand blasting processes use the form of compressing the air. Of course, it is not necessary to use high-speed rotating impeller in shot blasting process. Generally in ship repair and shipbuilding industries, shot blasting process (small steel shots) is commonly used in steel plate pretreatment (rust removal before painting); sand blasting process (ore used in ship repair and shipbuilding industries) is usually used in formed ships or sections, which can remove old paint and rust from the steel plates and repaint them. In ship repair and shipbuilding industries, the main function of shot blasting and sand blasting is to increase the adhesion of the steel plate coating.

In fact, shot blasting process is not the only method to clean casting parts. For large pieces, it generally uses the roller to clean the sand first, that is, cut out the risers of casting parts, put them in the roller, and the parts will collide with each other in the roller, so that most of the sand on the surface is cleaned first and then shot blasting or sand blasting process can be carried out.

The size of the shot in shot blasting process is 1.5mm.

Researches show that it is easier to damage the mental material when tensile stress rather than pressure stress exists on the surface. The fatigue life of materials is greatly increased when the surface is under pressure stress, therefore, shot blasting is usually used to form surface pressure stress to improve product life for axial parts with easy fatigue break. In addition, metal materials are very sensitive to stretch, which is why the tensile strength of materials is much lower than the compression strength, and this is also the reason why the tensile strength (yield, tensile) of metal materials is generally used to represent material performance.

The working faces of steel plates in our daily cars are strengthened with shot blasting, which can significantly improve the fatigue resistance of the material.

Shot blasting is a process that drives the rotation of impeller body by electrical machinery, and under the effect of centrifugal force, the shots whose diameter is 0.2 ~ 3.0 (casting shots, cut shots and stainless steel shots, etc.) will be flung to the surface of the workpiece to make the workpiece surface reach a certain roughness degree and make the workpiece beautiful, or change the welding tensile stress of workpiece to pressure stress to improve the service life of the workpiece. Shot blasting process is almost used in most machinery fields, such as shipbuilding and ship repairing, auto parts, aircraft parts, surfaces of guns and tanks, bridges, steel structures, glass, steel plates, and pipes. Sand (shot) blasting process uses compressed air as power to spray the sand whose diameter is 40-120 meshes or the shots whose diameter is 0.1~2.0 onto the surface of the workpiece to achieve the same effect. The process effects are different with different sizes of sand and shots. Emphasis: Shot blasting process can also play the role of strengthening. Now the domestic equipment go into an erroneous zone, and the enterprises think only shot blasting process can achieve the goal of strengthening. Enterprises in United States and Japan use shot blasting and shot blasting together for strengthening! Shot blasting and shot blasting have respective advantages, for example, for workpiece such as gears, only frequency conversion can be used to change the initial speed because the angle of shot blasting cannot be changed. Shot blasting can process a large amount of workpieces at a fast speed while shot blasting is the opposite, but the effect of shot blasting process is not as good as that of shot blasting.

Details about sandblasting process

Sand blasting process is a method to clean the surface of parts by using compressed air to blow quartz sand out at a high speed. It is also called sand blowing in factories, which removes both rust and oil and is very useful for painting. Sand blasting process is often used in derusting and  modification of part surface (This is the purpose of small wet-type sand blasting machines sold on the market, and the sand is usually corundum and the medium is water); In steel structure, the application of high-strength bolt connection is an advanced method. The quality requirement of the junction surface is very high because the high-strength connection uses the friction between the junction surfaces to transfer the force, here the junction surface must be treated with sand blasting process.

Sand blasting is used when the shapes are complex, it is difficult to remove rust by hand, the efficiency is low, the site environment is poor and the rust is removed unevenly.

There are all kinds of specifications of sand blasting process guns in general sand blasting process machines, and almost all the guns can be put into the box for process as long as the box is not very small.

The matching product of the pressure vessel, the head, uses sand blasting process to remove the oxide skin on the surface of the workpiece. The diameter of quartz sand is 1.5mm to 3.5mm.

There is a kind of sand blasting processing which uses water as a carrier and drives emery to process parts.

Shot blasting process and sand blasting process can achieve the purpose of cleaning and decontamination of the workpiece, which will prepare for the following process, that is, to ensure the roughness of the next process, or to ensure the consistency of the surface in some cases. Shot blasting process has a more obvious strengthening effect on the workpiece than sand blasting process. Generally it uses small steel balls in shot blasting process and quartz sand in sand blasting process. They are divided into different meshes according to different requirements.

Sand blasting process and shot blasting process are used in precision casting almost every day.

1. Shot blasting process and sand blasting process are surface treatment processes, but it doesn't mean shot blasting process is only used in casting.

2. The main functions of sand blasting process are surface rust removal, oxide scale removal, etc., such as the part surface treatment after heat treatment. Shot blasting process has more effects and functions: in addition to derusting and oxide scale removal, it also improves the surface roughness, removes rags of machined parts, eliminates internal stress of parts, reduces the deformation of parts after heat treatment, improves the surface wear resistance and compression capability of parts, etc.

3. Shot blasting process is used in many operations, such as casting, forging, surface treatment of machined parts, part surface treatment after heat treatment and so on.

4. Sand blasting process mainly depends on manual operation, while shot blasting process is mostly automatic and semi-automatic.

5. In fact, the steel and iron shots used in shot blasting process are not real shots. Accurately speaking, they are small steel wires or steel bars which look like shots after being used for a long time. Actually the so-called sand in sand blasting process is just river sand, and it is not different from that used for architecture but the sand in sand blasting process is screened so it contains  less mud and particle sizes are uniform. Of course, in some industries, such as shipping industry, it uses real steel shots in shot blasting process and metal ore sand in sand blasting process(not river sand - quartz sand).