casting
Liquid metal is cast into a mold cavity adapted to the shape and size of the parts. The production method of the blank or part for cooling and solidification is usually called metal forming or casting.
Process flow: liquid metal, filling, solidification, shrinkage and casting.
Process characteristics:
1, it can produce any complex parts, especially those with complicated inner cavity shape.
2, adaptability is strong, alloy type is not restricted, casting size is almost unlimited.
3, materials are widely available, waste products can be remelted and equipment investment is low.
4, high reject rate, low surface quality and poor working conditions.
Casting classification:
(1) sand mold casting (sand casting)
Sand casting: casting method for casting in sand mold. Steel, iron and most non-ferrous alloy castings can be obtained by sand casting.
Technological process：
Sand casting process flow
Technical features:
1. It is suitable for making complex shapes, especially those with complex inner cavity.
2, wide adaptability and low cost;
3, for some poor plastic materials, such as cast iron, sand casting is the only forming process for making parts or blank.
Application: automobile engine cylinder block, cylinder head, crankshaft and other castings.
(2) molten mold casting (Investmentcasting)
Mold casting: usually refers to the mold made of the fable material, coated with several layers of refractory materials on the surface, and then melt out the mold shell to get the casting mould without the type surface, and the casting scheme can be filled after the high temperature roasting. It is often called “lost wax casting”.
Technological process：
Process flow of molten mould casting
Advantage：
1. The dimension precision and the geometric precision are high.
2. The surface roughness is high.
3. It is capable of casting complex castings, and casting alloys are not limited.
Shortcomings: the process is complicated and the cost is high
Application: it is suitable for producing small parts such as complex shape, high accuracy, or difficult to carry out other processing, such as turbine engine blades.
(3) pressure casting (die casting)
Die casting: high pressure is used to press metal liquid into a precision metal mold cavity, and metal liquid is cooled and solidified under pressure to form castings.
Technological process：
Advantage：
1. When casting, the metal liquid bears high pressure and fast flow rate.
2, the product quality is good, the size is stable, the interchangeability is good;
3. The production efficiency is high and the die casting die is used many times.
4. It is suitable for large quantities of large quantities of production, and the economic benefit is good.
Shortcomings:
1, the casting is easy to produce small pores and shrinkage.
2. Die castings are of low plasticity and are not suitable for impact loading and vibration.
3. When high melting point alloy die casting, the die life is low, which affects the expansion of die casting production.
Application: the die casting is first applied in the automobile industry and the instrument industry, and then gradually expanded to various industries, such as agricultural machinery, machine tool industry, electronic industry, national defense industry, computer, medical equipment, clocks, cameras and daily hardware and other industries.
(4) low pressure casting (low pressure casting)
Low pressure casting is a method for filling liquid metal under low pressure (0.02 ~ 0.06MPa) and crystallizing under pressure to form castings.
Technological process：
Technical features:
1, the pressure and speed of pouring can be adjusted, so it can be applied to various types of casting (such as metal type, sand mold, etc.), casting a variety of alloys and all kinds of castings of all sizes.
2. Using the bottom filling type filling, the metal liquid filling is smooth and no splash, it can avoid the involvement of gas and the scour to the wall and core, and improve the qualified rate of the castings.
3. The casting is crystallized under pressure. The structure of the casting is dense, the outline is clear, the surface is clean, and the mechanical properties are high.
4, save the riser and increase the utilization ratio of metal to 90 to 98%.
5, low labor intensity, good working conditions, simple equipment, easy to realize mechanization and automation.
Application: mainly traditional products (cylinder head, hub, cylinder rack, etc.).
(5) centrifugal casting (centrifugal casting)
Centrifugal casting is a casting method for pouring molten metal into rotating mold, filling mold with centrifugal force and solidifying.
Technological process：
Advantage：
1. There is almost no metal consumption in gating system and riser system, and the production yield is increased.
2. When producing hollow castings, the core can not be used, so the metal filling ability can be greatly improved when producing long tubular castings.
3. The casting has high density, low porosity and slag inclusion, and high mechanical properties.
4. It is easy to make the composite metal castings of cylinder and sleeve.
Shortcomings:
1, there are certain limitations in the production of special-shaped castings.
2, the diameter of the inner hole of the casting is not accurate, the surface of the inner hole is rough, the quality is poor, and the machining allowance is large.
3, specific gravity segregation is easily produced in the castings.
Application:
Centrifugal casting was first used to produce pipe casting. Centrifugal casting technology was used in metallurgy, mine, transportation, drainage and irrigation machinery, aviation, defense and automobile industry at home and abroad, and the steel, iron and non iron carbon alloy castings were produced. Especially the production of castings, such as centrifugal cast iron pipes, internal combustion engine cylinder sleeves and bushings, is most common.
(6) metal casting (gravity die casting)
Metal casting: refers to the liquid metal in gravity
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