Casting
The liquid metal is poured into the mold cavity suitable for the shape and size of the part, and then cooled and solidified, to obtain a blank or part, often called liquid metal forming or casting.
Process flow: liquid metal → filling → solidification shrinkage → casting
c
Process features:
1. Can produce arbitrarily complex shape parts, especially the shape of the cavity complex parts.
2. Strong adaptability, the type of alloy is not limited, the size of the casting is almost not limited.
3. The material source is wide, the waste can be remelted, the equipment investment is low.
4. High scrap rate, low surface quality, poor working conditions.
1. Sand casting
Casting method for producing castings in sand. Steel, iron and most non-ferrous alloys can be obtained by sand casting.
Features
1.Suitable for making rough with complex shape, especially with complex inner cavity.
2. Wide adaptability, low cost.
3. For some materials with poor plasticity, 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. Investment casting
It usually refers to a casting scheme that is made of fusible material, coated with several layers of refractory material on the surface of the pattern to make a mold shell, and then melted and discharged the mold shell, so as to obtain the mold without parting surface, and can be filled with sand after high temperature roasting. It is often called "lost wax casting".
Features
Advantages:
1. High dimensional accuracy and geometric accuracy.
2. High surface roughness.
3. Can cast the appearance of complex castings, and the cast alloy is not limited.
Cons:
Complicated process and high cost
Applications: Suitable for the production of small parts with complex shapes, high accuracy requirements or difficult other processing. Such as turbine engine blades.
The metal liquid is pressed into a precision metal mold cavity at high speed by high pressure, and the metal liquid is cooled and solidified under the action of pressure to form a casting.
Features
Advantages:
1. Die Casting metal liquid withstand 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.
Cons:
1. Castings are easy to produce small pores and shrinkage.
2. Die casting plasticity is low, should not work in the impact load and vibration.
3. High melting point alloy die-casting, casting life is low, affecting the expansion of die-casting production.
Application: Die casting parts were first used in the automotive industry and instrument industry, and later gradually expanded to various industries, such as agricultural machinery, machine tool industry, electronics industry, national defense industry, computers, medical equipment, watches, cameras and daily hardware and other industries.
4. Low pressure casting
It is a method of filling the mold with liquid metal under low pressure (0.02 ~ 0.06MPa) and solidification under pressure to form a casting.
Features:
1. The pressure and speed of pouring can be adjusted, so it can be applied to a variety of different molds (such as metal mold, sand mold etc.), casting various alloys and castings of various sizes.
2. Using the bottom injection type filling, metal liquid filling stable, no splash phenomenon, can avoid gas involvement and erosion of the mold wall and core, improve the casting qualified rate.
3. The casting crystallizes under pressure, as well as that is dense, the outline is clear, the surface is smooth, and the mechanical properties are high. It is especially advantageous 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, wheel hub, cylinder frame, etc.).
5.centrifugal casting
It is a casting method in which liquid metal is poured into a rotating cast and filled with the cast under the action of centrifugal force.
Features
Advantages
1. Almost no metal consumption of the pouring 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, but porosity, slag and other defects less, high mechanical properties.
4. Easy to manufacture cylinder, sleeve type composite metal castings.
Cons:
1. There are certain limitations for 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. Castings are prone to specific gravity deviation.
Application: Centrifugal casting was first used in the production of cast pipe. Centrifugal casting process is used at home and abroad in metallurgy, mining, transportation, drainage and irrigation machinery, aviation, national defense, automobile and other industries to produce steel, iron and non-iron carbon alloy castings. Among them, the production of centrifugal cast iron pipe, cylinder liner and shaft sleeve is the most common.
6. Gravity die casting
Refers to the liquid metal filling metal mold under the action of gravity and cooling solidification in the mold to obtain a casting molding method.
Features
Advantages:
1. Metal type thermal conductivity and heat capacity is large, cooling speed is fast, casting structure is dense, mechanical properties are about 15% higher than sand casting.
2. Castings with higher dimensional accuracy and lower surface roughness can be obtained, and the quality stability is good.
3. Less sand cores are used to improve the environment, reduce dust and harmful gases and reduce labor intensity.
Cons:
1. The metal type itself is not permeable, and certain measures must be taken to derive the air in the cavity and the gas generated by the sand core.
2. Metal type no concession, casting solidification is easy to crack.
3. Metal type manufacturing cycle is long and costly. Therefore, only when a large number of mass production, can show good economy effects.
Application: Metal casting is not only suitable for mass production of complex shape of aluminum alloy, magnesium alloy and other non-ferrous alloy castings, but also suitable for production of iron and steel metal castings, ingots and so on.
7. Vacuum die casting
An advanced die casting process that eliminates or significantly reduces pores and dissolved gases in die castings by removing the gas from the die cavity during die casting, thereby improving the mechanical properties and surface quality of die castings.
Features
Advantages:
1. Eliminate or reduce the porosity inside the die casting, improve the mechanical properties and surface quality of the die casting, improve the plating performance.
2. Reduce the back pressure of the cavity, can use a lower specific pressure and casting performance of poor alloy, producing large castings with a small machine.
3. Improve the filling conditions, can die casting thinner castings.
Cons:
1. The mold sealing junction is very complex, manufacturing and installation is more difficult, so the cost is higher.
2. Improper control of vacuum die casting method would not give successful results.
8. Extrusion casting
Making liquid or semi-solid metal solidified 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.
Features
1.Eliminate the internal pores, shrinkage and porosity and other defects;
2. Low surface roughness, high dimensional accuracy.
3. Prevent the generation of casting cracks.
4. Easy to realize mechanization and 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 (also known as solid casting)
It is a new casting method of bonding paraffin or foam models similar to the size and shape of castings into model clusters, brushing refractory coating and drying, buried in dry quartz sand vibration modeling, pouring under negative pressure, so that the model gasification, liquid metal occupies the model position, solidifying and cooling to form castings.
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 very complex various sizes of precision castings, the type of alloy is not limited, the production batch is not limited. Such as gray cast iron engine box, high manganese steel elbow and so on.
10. Continual casting
As an advanced casting method, the principle is to melt the metal, constantly poured into a special metal type called the mold, solidified (crusted) castings, continuously pulled out from the other end of the mold, it can obtain any length or a specific length of castings.
Features
1.Due to the rapid cooling of the metal, the crystal is dense, the organization is uniform, and the mechanical properties are good.
2. Save metal, improve the yield.
3. Simplify the process, eliminate modeling and other processes, thus reducing labor intensity; The area required for production has also been greatly reduced.
4. Continuous casting production is easy to achieve 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 unchanged section shape, such as ingot, slab, bar, pipe, etc.
11. Semi-solid metals molding (SSM)
The use of non-dendrite semi-solid metals (SSM) unique rheological and agglutination properties to control the quality of castings. Semi-solid forming can be divided into Rheoforming and Thixoforming.
(1)Rheoforming
(2)Thixoforming
Features
1. Reduce liquid forming defects, significantly improve quality and reliability.
2. The forming temperature is lower than the full liquid forming temperature, greatly reducing the thermal impact on the mold.
3. Can produce conventional liquid forming method is impossible to produce alloys.
Application: It has been successfully used in the manufacture of master cylinder, steering system parts, rocker arm, engine piston, wheel hub, transmission system parts, fuel system parts and air conditioning parts, etc., aviation, electronics and consumer goods.
c
