Liquid metal is poured into the mold cavity corresponding to the shape and size of the part, and then cooled and solidified to obtain the blank or parts, which is usually called liquid metal forming or casting.
Process flow: liquid metal → mold filling → solidification shrinkage → casting
1. It can produce any complex shape parts, especially those with complex inner cavity shape.
2. It has strong adaptability, unlimited alloy types and almost unlimited casting size.
3. The material source is wide, the waste can be remelted, and the equipment investment is low.
4. High reject rate, low surface quality and poor working conditions.
Sand casting: casting method for producing castings in sand mold. Steel, iron and most non-ferrous alloy castings can be obtained by sand casting.
1. It is suitable for making blank with complex shape, especially with complex inner cavity;
2. Wide adaptability and low cost;
3. For some materials with poor plasticity, such as cast iron, sand casting is the only forming process for parts or blanks.
Application: automobile engine cylinder block, cylinder head, crankshaft and other castings
Investment casting: usually refers to the casting scheme in which the pattern is made of fusible materials, coated with several layers of refractory material on the surface of the pattern, and then the pattern is melted out of the shell, so as to obtain the mold without parting surface, and then the sand can be filled and poured after high temperature roasting. It is often called "lost wax casting".
1. High dimensional and geometric accuracy;
2. The surface roughness is high;
3. It can be used to cast castings with complex shape, and the cast alloy is not limited.
Disadvantages: complex process, high cost
Application: it is suitable for the production of small parts with complex shape, high precision requirements, or difficult to process, such as turbine engine blades.
Die casting: high pressure is used to press liquid metal into a precision metal mold cavity at high speed. The liquid metal is cooled and solidified under pressure to form a casting.
1. During die casting, the metal liquid bears high pressure and the flow rate is fast
2. Good quality, stable size and good interchangeability;
3. It has high production efficiency and many times of using die casting die;
4. It is suitable for mass production with good economic benefit.
1. The casting is easy to produce fine porosity and shrinkage porosity.
2. Because of the low plasticity of the die casting, it is not suitable to work under the condition of impact load and vibration;
3. In die casting of high melting point alloy, the mold life is low, which affects the expansion of die casting production.
Application: die castings were first used in automobile industry and 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: it refers to the method that liquid metal fills the mold under the action of low pressure (0.02 ~ 0.06mpa) and crystallizes under pressure to form castings.
1. The pressure and speed of pouring can be adjusted, so it can be used for casting various alloys and castings of various sizes;
2. By using bottom filling mode, the filling of liquid metal is stable without splashing, which can avoid gas entrainment and erosion of mold wall and core, and improve the qualified rate of castings;
3. When the casting crystallizes under pressure, the casting structure is dense, the contour is clear, the surface is smooth, and the mechanical properties are high;
4. Without feeding riser, the utilization rate of metal is increased to 90-98%;
5. Low labor intensity, good working conditions, simple equipment, easy to realize mechanization and automation.
Application: mainly traditional products (cylinder head, hub, cylinder frame, etc.).
Centrifugal casting: it is a casting method in which molten metal is poured into a rotating mold, and the mold is filled and solidified under the action of centrifugal force.
1. There is almost no metal consumption in gating system and riser system, which improves the yield of the process;
2. Therefore, the metal filling capacity can be greatly improved in the production of long tubular castings;
3. The casting has high density, less porosity and slag inclusion, and high mechanical properties;
4. It is convenient to manufacture composite metal castings such as cylinder and sleeve.
1. There are some limitations in the production of special-shaped castings;
2. The diameter of the inner hole is not accurate, the surface of the inner hole is rough, the quality is poor and the machining allowance is large;
3. The casting is easy to produce specific gravity segregation.
Centrifugal casting was first used in the production of cast pipe. The centrifugal casting process is used in metallurgy, mining, transportation, drainage and irrigation machinery, aviation, national defense, automobile and other industries at home and abroad to produce steel, iron and non-ferrous carbon alloy castings. Among them, centrifugal cast iron pipe, cylinder liner and shaft sleeve of internal combustion engine are the most common.
(6)gravity die casting
Metal mold casting: refers to the liquid metal under the action of gravity filling metal mold and cooling solidification in the mold to obtain a casting method.
1. The results show that the thermal conductivity and heat capacity of the metal mold are large, the cooling speed is fast, the casting structure is dense, and the mechanical properties are about 15% higher than that of sand mold casting.
2. The castings with high dimensional accuracy and low surface roughness can be obtained with good quality stability.
3. It can improve the environment, reduce dust and harmful gas, and reduce labor intensity.
1. The metal mold itself has no air permeability, so some measures must be taken to export the air in the mold cavity and the gas produced by the sand core;
2. The metal mold has no yielding property, and the casting is easy to crack during solidification;
3. The manufacturing cycle of metal mold is longer and the cost is higher. Therefore, only in the mass production, can the good economic effect be shown.
Application: metal mold casting is not only suitable for mass production of aluminum alloy, magnesium alloy and other non-ferrous alloy castings with complex shapes, but also suitable for the production of steel castings and ingots.
(7)Lost foam casting
Lost foam casting, also known as real mold casting, is a new type of casting method that combines the wax or foam model bonded to the size and shape of the casting into a model cluster. After coating the refractory coating and drying it, it is embedded in dry quartz sand in the vibration modeling, pouring under negative pressure, making the model gasified, the liquid metal occupies the mold position, and solidified and cooled to form a new casting method.
1. The casting has high precision and no sand core, which reduces the processing time;
2. No parting surface, flexible design and high degree of freedom;
3. Clean production, no pollution;
4. Reduce investment and production costs.
Continuous casting: is an advanced casting method, its principle is to continuously pour molten metal into a special metal mold called mold, solidified (crusted) casting, continuously pull out from the other end of the mold, it can obtain any length or specific length of casting.
1. Due to the rapid cooling of the metal, the crystal is dense, the microstructure is uniform and the mechanical properties are good;
2. Save metal and increase yield;
3. The working procedure is simplified, and modeling and other working procedures are avoided, so the labor intensity is reduced, and the production area required is greatly reduced;
4. Continuous casting production is easy to realize mechanization and automation and improve production efficiency.
Application: the continuous casting method can be used to cast steel, iron, copper alloy, aluminum alloy, magnesium alloy and other long castings with constant cross-section shape, such as ingot, slab, bar blank, pipe, etc.
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