(1) Sand casting: Sand casting is a casting method that produces castings in sand molds. Steel, iron and most non-ferrous alloy castings can be obtained by sand casting. Process flow: Sand casting process flow Technical features: 1. Suitable for making complex shapes, especially blanks with complex internal cavities; 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 manufacturing their parts or blanks. Application: Automobile engine cylinder block, cylinder head, crankshaft and other castings
(2) Investment casting Investment casting: usually refers to making a pattern out of fusible material, coating the surface of the pattern with several layers of refractory material to make a shell, then melting the pattern and discharging it from the shell, thereby obtaining a casting without a parting surface, which can be filled with sand and poured after high-temperature roasting. It is often called "lost wax casting". Process flow: Investment casting process characteristics Advantages: 1. High dimensional accuracy and geometric accuracy; 2. High surface roughness; 3. Ability to cast castings with complex shapes, and the alloys cast are not restricted. Disadvantages: Complex procedures and high costs Application: Suitable for the production of small parts with complex shapes, high precision requirements, or difficult to perform other processing, such as turbine engine blades.
(3) Die casting: Die casting is the process of using high pressure to press molten metal into a precision metal mold cavity at high speed. The molten metal cools and solidifies under pressure to form a casting. Process flow: Process characteristics Advantages: 1. During die casting, the metal liquid is under high pressure and has a fast flow rate. 2. Good product quality, stable dimensions, and good interchangeability; 3. High production efficiency, and the die casting mold can be used many times; 4. Suitable for large-scale mass production with good economic benefits. Disadvantages: 1. Castings are prone to produce fine pores and shrinkage. 2. Die castings have low plasticity and are not suitable for working under impact loads and vibrations; 3. When die casting high melting point alloys, the mold life is low, which affects the expansion of die casting production. Application: Die castings were first used in the automotive industry and instrumentation industry, and later gradually expanded to various industries, such as agricultural machinery, machine tool industry, electronics industry, national defense industry, computers, medical equipment, clocks and watches, cameras, and daily hardware.
(4) Low pressure casting Low pressure casting: refers to the method of filling the mold with liquid metal under low pressure (0.02-0.06MPa) and crystallizing under pressure to form castings. Process flow: Technical features: 1. The pressure and speed during pouring can be adjusted, so it can be applied to various different molds (such as metal molds, sand molds, etc.), casting various alloys and castings of various sizes; 2. The bottom injection type is adopted, and the metal liquid fills the mold smoothly without splashing, which can avoid the entrapment of gas and the scouring of the mold wall and core, and improve the qualified rate of castings; 3. The casting crystallizes under pressure, and the casting has a dense structure, clear contours, smooth surface, and high mechanical properties, which is particularly beneficial for the casting of large thin-walled parts; 4. The shrinkage feeder is omitted, and the metal utilization rate is increased to 90-98%; 5. The labor intensity is low, the working conditions are good, the equipment is simple, and it is easy to realize mechanization and automation. Application: Mainly traditional products (cylinder heads, wheel hubs, cylinder frames, etc.).
(5) Centrifugal casting Centrifugal casting: It is a casting method that pours molten metal into a rotating mold, fills the mold and solidifies under the action of centrifugal force. Process flow: Process characteristics Advantages: 1. There is almost no metal consumption in the pouring system and riser system, which improves the process yield; 2. When producing hollow castings, no core is required, so the metal filling capacity can be greatly improved when producing long tubular castings; 3. The casting has high density, few defects such as pores and slag inclusions, and high mechanical properties; 4. It is convenient to manufacture composite metal castings such as tubes and sleeves. Disadvantages: 1. There are certain limitations when it is used to produce special-shaped castings; 2. The inner hole diameter of the casting is inaccurate, the inner hole surface is relatively rough, the quality is poor, and the processing allowance is large; 3. The casting is prone to specific gravity segregation. Application: Centrifugal casting was first used to produce cast pipes. Centrifugal casting technology is used in metallurgy, mining, transportation, drainage machinery, aviation, national defense, automobile and other industries at home and abroad to produce steel, iron and non-ferrous carbon alloy castings. Among them, the production of centrifugal cast iron pipes, internal combustion engine cylinder liners and shaft sleeves is the most common.
(6) Gravity die casting: refers to a molding method in which liquid metal fills a metal mold under gravity and cools and solidifies in the mold to obtain a casting. Process flow: Process characteristics Advantages: 1. 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 those of sand castings. 2. It can obtain castings with higher dimensional accuracy and lower surface roughness values, and the quality stability is good. 3. Because sand cores are not used or rarely used, the environment is improved, dust and harmful gases are reduced, and labor intensity is reduced. Disadvantages: 1. The metal mold itself has no air permeability, and certain measures must be taken to guide the air in the mold cavity and the gas generated by the sand core; 2. The metal mold has no yield, and cracks are easy to occur when the casting solidifies; 3. The metal mold manufacturing cycle is long and the cost is high. Therefore, only when it is mass-produced can it show good economic effects. Application: Metal mold casting is suitable for mass production of non-ferrous alloy castings with complex shapes such as aluminum alloy and magnesium alloy, as well as for the production of steel metal castings and ingots.
(7) Vacuum die casting: Vacuum casting is an advanced die casting process that eliminates or significantly reduces the pores and dissolved gases in the die casting by removing the gas in the die casting mold cavity during the die casting process, thereby improving the mechanical properties and surface quality of the die casting. Process flow: Process characteristics Advantages: 1. Eliminate or reduce the pores inside the die casting, improve the mechanical properties and surface quality of the die casting, and improve the plating performance; 2. Reduce the back pressure of the cavity, use alloys with lower specific pressure and poor casting performance, and it is possible to die cast larger castings with small machines; 3. Improve the filling conditions and die cast thinner castings; Disadvantages: 1. The mold sealing structure is complex, and it is difficult to manufacture and install, so the cost is high; 2. If the vacuum die casting method is not properly controlled, the effect is not very significant.
(8) Squeeze casting (squeezing die casting) Squeeze casting: It is a method of solidifying liquid or semi-solid metal under high pressure, flowing and forming, and directly obtaining parts or blanks. It has the advantages of high liquid metal utilization, simplified process and stable quality. It is an energy-saving metal forming technology with potential application prospects. Process flow: Direct squeeze casting: spraying coating, pouring alloy, closing the mold, pressurizing, maintaining pressure, releasing pressure, parting the mold, demolding the blank, and resetting; indirect squeeze casting: spraying coating, closing the mold, feeding, filling the mold, pressurizing, maintaining pressure, releasing pressure, parting the mold, demolding the blank, and resetting. Technical features: 1. It can eliminate internal defects such as pores, shrinkage cavities and shrinkage; 2. Low surface roughness and high dimensional accuracy; 3. It can prevent the occurrence of casting cracks; 4. It is 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, etc.
(9) Lost foam casting Lost foam casting (also known as full mold casting) is a new casting method that combines wax or foam models with similar size and shape to the casting into a model cluster, brushes refractory coating and dries it, buries it in dry quartz sand for vibration molding, pours it under negative pressure, vaporizes the model, and liquid metal occupies the position of the model. After solidification and cooling, it forms a casting. Process flow: pre-foaming → foaming molding → coating immersion → drying → molding → pouring → sand dropping → cleaning Technical features: 1. High casting precision, no sand core, reducing 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 various sizes of complex precision castings, with no limit on alloy types and production batches. Such as gray cast iron engine cases, high manganese steel elbows, etc.
(10) Continuous casting: Continuous casting is an advanced casting method. Its principle is to pour molten metal into a special metal mold called a crystallizer continuously. The solidified (crusted) casting is continuously pulled out from the other end of the crystallizer. It can obtain castings of any length or specific length. Process flow: Technical features: 1. Because the metal is cooled quickly, the crystals are dense, the structure is uniform, and the mechanical properties are good; 2. It saves metal and improves the yield; 3. It simplifies the process, eliminates molding and other processes, thereby reducing labor intensity; the required production area is also greatly reduced; 4. Continuous casting production is easy to realize mechanization and automation, and improves production efficiency. Application: Continuous casting can be used to cast long castings with unchanged cross-sectional shapes such as steel, iron, copper alloy, aluminum alloy, magnesium alloy, etc., such as ingots, slabs, bars, pipes, etc.
