Shot blasting is also the name of a mechanical surface treatment process, similar to sand blasting.
Its principle is to use the motor to drive the impeller body to rotate. By the action of centrifugal force, the balls (including casting balls, cutting balls, stainless steel balls, etc.) with the diameter of 0.2 ~ 3.0 are thrown to the surface of the workpiece, so that the surface of the workpiece reaches a certain roughness, making the workpiece beautiful, or changing the welding tensile stress of the workpiece to compressive stress, so as to improve the service life of the workpiece.
Almost used in most fields of machinery, ship repair, auto parts, aircraft parts, gun tank surface, bridge, steel structure, glass, steel plate, pipe, etc.
In form, shot blasting is achieved by mechanical means of high-speed and long-distance projection onto the surface of parts, collectively known as shot blasting.
- The shot is blasted to the casting with sand to remove the shot falling sand of molding sand and core;
- Shot the projectile to the casting, forging, welding and heat treatment parts to clean the surface of black skin, nodulation, oxide film, rust, etc;
- The shot is shot onto the surface of steel plate and various shapes for shot blasting pretreatment;
- The spring, leaf spring and gear under variable stress are shot blasted to eliminate stress and improve surface fatigue strength;
- The surface of decorative parts of household appliances or tableware shall be shot blasted for coloring.
But in terms of process classification, shot blasting is only used to remove casting, forging, welding and heat treated parts
This paper refers to the concept of shot blasting cleaning.
For those who are shot to the surface of the workpiece to achieve the relevant process objectives, they are directly named according to the process requirements, such as shot blasting, shot blasting strengthening, shot blasting coloring, etc., so as to be different from shot blasting cleaning in process.
In shot blasting cleaning of parts, the facilities that can make the parts change the cleaned surface continuously in the jet stream to meet the requirements of uniform shot blasting are called shot blasting equipment, or shot blasting machinery.
Due to the ever-changing work pieces, there are many kinds of shot blasting equipment.
A certain specification of shot blasting equipment is only suitable for cleaning parts within a certain range.
And special equipment is suitable for a certain kind of parts.
Sand blasting is a method to clean the surface of parts by using compressed air to blow out quartz sand at high speed.
In the factory, it is also called sand blowing. It can not only remove rust, but also remove oil, which is very useful for painting.
It is often used to remove rust on the surface of parts; to modify the surface of parts (the small wet sand blasting machine sold in the market is for this purpose, the sand is usually corundum, and the medium is water);
In steel structure, high strength bolt is an advanced method
Because the high-strength connection uses the friction between the joint surface to transfer the force, so the quality of the joint surface is very high. At this time, sand blasting must be used to treat the joint surface.
Sand blasting process is divided into dry sand blasting and wet sand blasting.
There are two kinds of dry sand blasting: mechanical sand blasting and air pressure sand blasting
Each is divided into manual, non automatic or continuous automatic type
Manual air pressure sandblasting machine is widely used in China. It also uses various medium and small parts with complex shapes.
The abrasive used in wet sand blasting is the same as that used in dry sand blasting. The abrasive can be mixed with water to form mortar. The abrasive generally accounts for 20% – 35%, and it is stirred continuously to prevent sinking. Compressed air is pressed into the nozzle and sprayed to the parts
The sand and water can also be separately put into the tank, mixed before flowing to the nozzle, and then sprayed to the parts
In order to prevent corrosion of steel parts, sodium nitrite and other corrosion inhibitors must be added into water
In addition, sand should be dried before next use.
The equipment of wet sand blasting machine also has many forms, the most commonly used is sand blasting room.
Shot blasting vs sand blasting – differences and relations
But no matter shot blasting or sand blasting, compressed air can be used.
Of course, it’s not that the high-speed impeller must be used for shot blasting.
In the repair and shipbuilding industry, generally speaking, shot blasting (small steel shot) is mostly used for steel plate pretreatment (rust removal before coating); sand blasting (mineral sand used in repair and shipbuilding industry) is mostly used for forming ships or sections, which is used to remove the old paint and rust on steel plate and re coating.
In repair and shipbuilding industry, the main function of shot blasting and sand blasting is to increase the adhesion of steel plate painting.
In fact, the cleaning of casting parts is not only by shot blasting, but also by removing the riser of the casting parts and rolling them in the roller. The parts collide with each other in the roller to remove most of the sand on the surface before shot blasting or shot peening.
Both shot blasting and sand blasting can clean and decontaminate the workpiece. The purpose is to prepare for the next process, that is, to ensure the roughness requirements of the next process, and some to ensure the consistency of the surface
Shot peening can strengthen the workpiece, so it is not obvious.
Generally, shot peening is small steel ball and sand blasting is quartz sand.
Sand blasting and shot blasting are used in precision casting almost every day.