Shot
Blasting, also known as mechanical surface treatment, is a process similar to sand blasting.
The process works by using a motor to rotate the impeller body. The centrifugal force generated by the rotation causes balls with a diameter of 0.2 to 3.0 mm (which can be made from materials such as casting, cutting or stainless steel) to be projected onto the surface of the part. This results in a rough surface finish and improves the appearance of the part, or changes its welding tensile stress to compressive stress, thus increasing its service life.
Sandblasting is a process commonly used in various industries such as machinery, ship repair, auto parts, aircraft parts, surface treatment of tanks and weapons, bridge construction, steel structures, glass manufacturing and pipe production.
The blasting process involves projecting particles at high speed over long distances onto the surface of parts, using mechanical means. This process is collectively known as sandblasting.
Includes:
- The casting is sand blasted to remove any loose sand and core material.
- Blasting is also used to clean surfaces of castings, forgings, welded parts, and heat-treated parts. Removes black skin, nodules, oxide films, rust and other impurities.
- Blasting is a pre-treatment process used on steel sheets and various shapes.
- Springs, leaf springs and gears under tension are sandblasted to relieve stress and improve surface fatigue resistance.
- The surface of decorative parts of household appliances and cutlery can be sandblasted to enhance the color.
Blasting is primarily used to clean castings, forgings, welds, and heat-treated parts.
This article focuses on the concept of blast cleaning.
For processes that use blasting to achieve specific objectives on the surface of the workpiece, they are named according to the process requirements, such as shot blasting, blast strengthening, or shot coloring, to distinguish them from shot cleaning.
Shot blasting equipment, also known as shot blasting machine, is used to continuously change the surface of parts in a jet to achieve uniform blasting.
There are many types of blasting equipment due to the varied nature of the workpieces.
Each type of blasting equipment is only suitable for cleaning parts within a certain range, and specialized equipment exists for specific types of parts.
Sand blowing up
Sandblasting is a method of cleaning the surface of parts using compressed air to extract quartz sand at high speed. In factory configuration, it is also known as sandblasting. It is effective in removing rust as well as oil, making it a useful process for painting.
Sand blasting is often used to remove rust from the surface of parts and to modify the surface (small wet sand blasting machines sold on the market are used for this purpose, using sand such as corundum with water as the medium).
In steel structures, high-strength bolt connections are an advanced method. The high-strength connection relies on friction between the articular surfaces to transfer force, so the quality of the articular surface is crucial. In this case, sandblasting must be used to treat the joint surface.
The sand blasting process can be divided into dry sand blasting and wet sand blasting.
There are two types of dry sand blasting: mechanical sand blasting and air pressure sand blasting. Both types can be divided into manual, non-automatic, or continuous automatic types.
Manual air pressure sandblasting machine is widely used in China and is suitable for various medium and small parts with complex shapes.
Wet sand blasting uses the same abrasive material as dry sand blasting. The abrasive material can be mixed with water to form a mortar. Abrasive material typically makes up 20% to 35% of the mixture and is continually agitated to prevent sinking. Compressed air is then directed through a nozzle to spray the mixture onto the parts.
Alternatively, sand and water can be mixed before being fed into the nozzle and then sprayed onto the parts. To prevent corrosion of steel parts, sodium nitrite and other corrosion inhibitors should be added to the water.
The sand must also be dried before reusing it.
There are many forms of wet sand blasting equipment, with the most commonly used being sand blast rooms.
Blasting vs sand blasting – differences and relationships
Both blasting and sand blasting use compressed air. However, the use of a high-speed impeller is not necessary for blasting.
In the shipbuilding and repair industry, shot blasting (using small steel shot) is mainly used to pre-treat steel plates (removing rust before coating), while sand blasting (using mineral sand) is mainly used to form ships or sections. It is used to remove old paint and rust from steel plates before coating.
The main purpose of blasting and sandblasting in the shipbuilding and repair industry is to increase the adhesion of paint on steel sheets.
When cleaning castings, blasting is not the only method. The risers of the castings can also be removed and the parts can be rolled onto a roller, where they collide with each other to remove most of the sand from the surface before blasting or shot peening.
Both blasting and sand blasting can clean and decontaminate the workpiece, preparing it for the next process. This is to ensure the roughness requirements of the next process and ensure surface consistency.
Shot peening strengthens the workpiece, which is not the case with sand blasting or shot blasting.
Typically, shot peening uses small steel balls and sand blasting uses quartz sand.
Sand blasting and shot blasting are used daily in precision casting.
