What is casting❓
The liquid metal is poured into the cavity of the mold that corresponds to the shape and size of the part, and then cooled and solidified to obtain a blank or part of the production method, usually called liquid metal forming or casting.
Process flow: liquid metal → filling → solidification and shrinkage → casting
Process characteristics:
1.Can produce arbitrary shape complex parts, especially the cavity shape complex parts.
2.Strong adaptability, the type of alloy is not limited, casting size is almost not limited.
3.Wide sources of materials, waste products can be remelted, low equipment investment.
4. High rejection rate, low surface quality and poor working conditions.
Casting classification
Sand casting
Investmentcasting
Die casting
Low-pressure casting
Centrifugal casting
Gravity die casting
vacuumdie casting
Squeezing die casting
Lost foam casting
Continual casting
1.Sand casting
Sand mold casting: Casting method of producing castings in sand mold. Steel, iron and most nonferrous alloy castings can be obtained by sand casting.
Process flow:
Technical features:
1. Suitable for making rough with complex shape, especially with complex inner cavity.
2, Wide adaptability, low cost.
3. For some very poor plastic materials, such as cast iron, sand casting is the only forming process for manufacturing its parts or blanks.
Application: automobile engine cylinder block, cylinder head, crankshaft casting.
2.Investmentcasting
Investment casting: Usually refers to the casting scheme in which the shape is made from fusible materials, the surface of the shape is coated with several layers of refractory materials to make a mold shell, and then the mold is melted out of the mold shell, so as to obtain the mold without parting surface, and can be filled with sand and poured after high temperature roasting. Often called “lost wax casting”.
Process characteristics
Advantages:
1. High dimensional and geometric accuracy.
2. High surface roughness.
3, can cast the appearance of complex casting, and the casting of alloy is not limited.
Disadvantages: complicated process, high cost
Application: Suitable for the production of complex shape, high precision, or difficult to process other small parts, such as turbine engine blade, etc.
3.Die casting
Die casting: It is the use of high pressure to press the metal liquid into a precision metal mold cavity at high speed, and the metal liquid cools and solidifies under pressure to form a casting.
Process characteristics
1, die casting metal liquid under high pressure, fast flow rate.
2, good product quality, stable size, good interchangeability.
3, high production efficiency, die casting mold use times.
4, suitable for mass production, good economic benefits.
4.Low pressure casting
Low pressure casting: It is the method of filling the casting mold with liquid metal under the action of low pressure (0.02 ~ 0.06MPa), and crystallizing under pressure to form the casting.
Process flow:
Technical features:
1. The pressure and speed of pouring can be adjusted, so it can be used for a variety of different casting types (such as metal, sand, etc.), casting a variety of alloys and various sizes of castings.
2. The bottom filling type, metal liquid filling is stable, no splash phenomenon, can avoid the involvement of gas and erosion of the wall and core, improve the qualified rate of casting.
3.The casting crystallizes under pressure, the casting structure is dense, the outline is clear, the surface is smooth, the mechanical properties are high, which is especially favorable for the casting of large thin-walled parts.
4.Eliminate feeding riser, metal utilization rate increased to 90 ~ 98%.
5.Low labor intensity, good working conditions, simple equipment, easy to realize mechanization and automation.
Application: Mainly with traditional products (cylinder head, hub, cylinder frame, etc.).
5.Centrifugal casting
Centrifugal casting: It is a casting method in which liquid metal is poured into a rotating cast, and the cast is filled and solidified under centrifugal force.
Process flow:
Process characteristics
Advantages:
1.Almost no metal consumption of gating system and riser system, improve the process yield.
2.The production of hollow castings can not use the core, so in the production of long tubular castings can greatly improve the metal filling capacity.
3.Casting high density, porosity, slag and other defects less, high mechanical properties.
4. Easy to manufacture cylinder, sleeve type composite metal castings.
Disadvantages:
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 processing allowance is large.
3.Casting is easy to produce specific gravity segregation.
Application:
Centrifugal casting was first used in the production of cast pipe. 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-iron carbon alloy castings. Among them, centrifugal cast iron pipe, cylinder liner and shaft sleeve are the most common castings.
6.Gravity die casting
Metal mold casting: refers to the liquid metal filling metal mold under the action of gravity and cooling solidification in the mold to obtain casting.
Process flow:
Process characteristics
Advantages:
1. The thermal conductivity and thermal capacity of metal type are large, the cooling speed is fast, the casting structure is dense, and the mechanical property is about 15% higher than that of sand type casting.
2. The castings with higher dimensional accuracy and lower surface roughness can be obtained, and the quality stability is good.
3, because of the use of sand core and rarely, improve the environment, reduce dust and harmful gases, reduce labor intensity.
Disadvantages:
1. The metal type itself is not permeable, and certain measures must be taken to derive the air in the cavity and the gas produced by the sand core.
2, the metal type has no concession, casting solidification is easy to crack.
3, metal type manufacturing cycle is long, high cost. Therefore, only in the mass production, can show good economic effect.
7.Vacuumdie casting
Vacuum casting: Advanced die casting process that eliminates or significantly reduces porosity and dissolved gas in die casting by removing gas from die cavity during die casting, thereby improving mechanical properties and surface quality of die casting.
Process characteristics
Advantages:
1. Eliminate or reduce the porosity inside the die casting, improve the mechanical properties and surface quality of the die casting, improve the coating performance.
2.Reduce the back pressure of the cavity, can use lower specific pressure and casting performance of poor alloy, it is possible to use a small machine die casting larger castings.
3.Improved filling conditions, can die casting thinner castings.
Disadvantages:
1.The mold seal structure is complex, manufacturing and installation is difficult, so the cost is high.
2.Vacuum die casting method, such as improper control, the effect is not very significant.
8.Squeezing die casting
Extrusion casting: is to make liquid or semi-solid metal solidification under high pressure, flow forming, directly obtain the workpiece or blank method. It has the advantages of high utilization rate of liquid metal, simplified process and stable quality. It is a kind of energy-saving metal forming technology with potential application prospect.
Process flow:
Direct extrusion casting: spray coating, casting alloy, closing mold, pressure, pressure preservation, pressure relief, parting mold, blank demoulding, reset.
Indirect extrusion casting: spray coating, mold closing, feeding, filling, pressure, pressure preservation, pressure relief, parting, blank demoulding, reset.
Technical features:
1.Can eliminate the internal porosity, shrinkage and porosity defects.
2.Low surface roughness, high dimensional accuracy.
3.Can prevent the generation of casting cracks.
4.Easy to realize mechanization, automation.
Application: It can be used to produce various types of alloys, such as aluminum alloy, zinc alloy, copper alloy, ductile iron and so on.
Direct extrusion casting: spray coating, casting alloy, closing mold, pressure, pressure preservation, pressure relief, parting mold, blank demoulding, reset.
Indirect extrusion casting: spray coating, mold closing, feeding, filling, pressure, pressure preservation, pressure relief, parting, blank demoulding, reset.
Technical features:
1.Can eliminate the internal porosity, shrinkage and porosity defects.
2.Low surface roughness, high dimensional accuracy.
3.Can prevent the generation of casting cracks.
4.Easy to realize mechanization, automation.
Application: It can be used to produce various types of alloys, such as aluminum alloy, zinc alloy, copper alloy, ductile iron and so on.
9.Lost foam casting
Lost mold casting (also known as solid mold casting) :It is a new casting method which combines paraffin or foam models with similar size and shape to castings into model clusters, brushes with refractory paint and dries them, buries them in dry quartz sand for vibration modeling, casts under negative pressure, vaporizes the models, liquid metal occupies the position of the models, and forms the castings after solidification and cooling.
Process flow: pre-foaming → foaming forming → dipping coating → drying → modeling → pouring → sand falling → cleaning
Technical features:
1.High casting precision, no sand core, reduce the processing time.
2.No parting surface, flexible design, high degree of freedom.
3.Clean production, no pollution.
4.Reduce investment and production costs.
Application: Suitable for the production of complex structure of various sizes of precision castings, alloy type is not limited, production quantity is not limited. Such as gray cast iron engine box, high manganese steel elbow, etc.
10.Continual casting
Continuous casting: Is an advanced casting method, its principle is to melt metal, constantly poured into a special metal type called crystallize, solidified (crusted) casting, continuous continuous from the other end of the mold, it can obtain any length or a specific length of casting.
Process flow:
Technical features:
1. Due to the rapid cooling of the metal, the crystallization is dense, the organization is uniform, and the mechanical property is good.
2.Save metal, improve the yield.
3.Simplify the process, eliminate modeling and other processes, thus reducing the intensity of labor; The area required for production has also been greatly reduced.
4.Continuous casting production is easy to realize mechanization and automation, 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 section shape, such as ingot, slab, bar, pipe, etc.