For previous article, please refer to Overview of the world's top ten casting processes.

Die casting: It is to use high pressure to press molten metal into cavity of a precision metal mold at high speed. Molten metal cools and solidifies under pressure to form a casting.
Process flow:

 

Die casting machine
Die casting process characteristics
Advantages: 1. Metal liquid is under high pressure and has a fast flow rate during die casting. 2. Good product quality, stable size, and good interchangeability; 3. High production efficiency, many times of die casting mold use; 4. Suitable for large-scale mass production with good economic benefits.
Disadvantages: 1. Castings are prone to fine pores and shrinkage. 2. Die castings have low plasticity, are not suitable for working under impact loads and vibrations; 3. When high melting point alloys are die cast, mold life is low, which affects expansion of die casting production.

 

Die Casting Mould
Application: Die castings were first used in 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.

 

Low pressure casting: refers to method of filling mold with liquid metal under low pressure (0.02-0.06MPa) and crystallizing under pressure to form castings.
Process flow:

 

Technical features: 1. 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. Bottom injection type is adopted, and metal liquid fills mold smoothly without splashing, which can avoid entrapment of gas and scouring of mold wall and core, and improve qualified rate of castings; 3. Casting crystallizes under pressure, casting has a dense structure, clear contours, smooth surface, and high mechanical properties, which is particularly beneficial for casting of large thin-walled parts; 4. Shrinkage feeder is omitted, and metal utilization rate is increased to 90-98%; 5. Labor intensity is low, working conditions are good, equipment is simple, it is easy to realize mechanization and automation.
Application: Mainly traditional products (cylinder heads, wheels, cylinder racks, etc.)
Typical products:

 

 

Centrifugal casting: It is a casting method that pours molten metal into a rotating mold and fills mold under action of centrifugal force to solidify and form.
Process flow:

 

Process characteristics and advantages: 1. There is almost no metal consumption in pouring system and riser system, which improves process output rate; 2. When producing hollow castings, cores can be used, so metal filling capacity can be greatly improved when producing long tubular castings; 3. Casting has high density, few defects such as pores and slag inclusions, and high mechanical properties; 4. It is easy to manufacture composite metal castings such as tubes and sleeves.
Disadvantages: 1. There are certain limitations when used to produce special-shaped castings; 2. Inner hole diameter of casting is inaccurate, inner hole surface is relatively rough, quality is poor, and processing allowance is large; 3. 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, production of centrifugal cast iron pipes, internal combustion engine cylinder sleeves and shaft sleeves is the most common.
Typical product display:

 

 

Metal mold casting: refers to a molding method in which liquid metal fills a metal mold under action of gravity and cools, solidifies in mold to obtain a casting.
Process flow:

 

Process characteristics and advantages: 1. Thermal conductivity and heat capacity of metal mold are large, cooling speed is fast, casting structure is dense, and mechanical properties are about 15% higher than those of sand castings. 2. Castings with higher dimensional accuracy and lower surface roughness values can be obtained, and quality stability is good. 3. Because sand cores are not used or rarely used, environment is improved, dust and harmful gases are reduced, and labor intensity is reduced.
Disadvantages: 1. Metal mold itself has no air permeability, certain measures must be taken to guide air in mold cavity and gas generated by sand core; 2. Metal mold has no yield, and cracks are easy to occur when casting solidifies; 3. Metal mold manufacturing cycle is long and cost is high. Therefore, only when it is mass-produced can good economic effects be shown.
Application: Metal mold casting is suitable for mass production of non-ferrous alloy castings such as aluminum alloys and magnesium alloys with complex shapes, and is also suitable for production of steel metal castings, ingots, etc.
After casting process drawing is drawn, metal mold design can be carried out. Design content mainly includes determining structure, size, core, exhaust system and ejector mechanism of metal mold. Designed metal mold should strive to be simple in structure, convenient in processing, reasonable in material selection, safe and reliable. 
Structural form of metal mold: Structure of metal mold depends on shape and size of castings; number of parting surfaces; type of alloy, production batch and other conditions. According to position of parting surface, metal mold structure has following forms: 1. Integral metal mold, casting mold has no parting surface and structure is simple, but it is only suitable for castings with simple shapes and no parting surface; 2. Horizontal parting metal mold, it is suitable for thin-walled wheel castings. 3. Vertical parting metal mold, this type of metal mold is convenient for opening pouring risers and exhaust systems, opening and closing molds are convenient, and mechanized production is easy to achieve; it is mostly used to produce simple small castings; 4. Comprehensive parting metal mold: it is composed of two or more parting surfaces, or even composed of live blocks, and is generally used for production of complex castings. It is easy to operate and widely used in production.
When designing a metal mold, there must be exhaust facilities, and exhaust methods are as follows: 1. Use gap between parting surface or combined surface of cavity parts for exhaust. 2. Open exhaust grooves. That is, exhaust grooves are made on parting surface or combined surface of cavity parts, core seat or ejector pin surface. 3. Set up exhaust holes. Exhaust holes are generally opened at the highest point of metal mold. 4. Exhaust plugs are commonly used exhaust facilities for metal molds.
From analysis of causes of metal mold damage, it can be seen that materials used to make metal molds should meet following requirements: good heat resistance and thermal conductivity, no deformation or damage when repeatedly heated; should have certain strength, toughness and wear resistance, and good machinability. Cast iron is the most commonly used material for metal molds. It has good processing performance and is cheap. Generally, factories can make it themselves. It is also heat-resistant and wear-resistant, making it a more suitable metal mold material. Carbon steel and low-alloy steel are only used when requirements are high. Use of aluminum alloy to make metal molds has attracted attention abroad. Surface of aluminum mold can be anodized to obtain an oxide film composed of Al2O3 and Al2O3·H2O, which has a high melting point and hardness, is heat-resistant and wear-resistant. It is reported that this aluminum metal mold, if water cooling measures are adopted, can not only cast aluminum and copper parts, but also can be used to cast ferrous metal castings.

 

Vacuum casting: An advanced die casting process that eliminates or significantly reduces pores and dissolved gases in die casting by removing gas in die casting mold cavity during die casting process, thereby improving mechanical properties and surface quality of die casting.
Process flow:

 

Advantages: 1. Eliminate or reduce pores inside die casting, improve mechanical properties and surface quality of die casting, and improve plating performance; 2. Reduce back pressure of 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 filling conditions and die cast thinner castings;
Disadvantages: 1. Mold sealing structure is complex, it is difficult to manufacture and install, so cost is high; 2. If vacuum die casting method is not properly controlled, effect is not very significant.

 

 

Squeezing casting is a method of solidifying and flowing liquid or semi-solid metal under high pressure to directly obtain parts or blanks. It has advantages of high utilization rate of liquid metal, simplified process and stable quality. It is an energy-saving metal forming technology with potential application prospects.
Process flow:

 

Direct extrusion casting: spraying coating, pouring alloy, closing mold, pressurizing, holding pressure, releasing pressure, parting mold, demolding blank, resetting; indirect extrusion casting: spraying coating, closing mold, feeding, filling mold, pressurizing, holding pressure, releasing pressure, parting mold, demolding blank, 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 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.

 

Lost foam casting (also known as full mold casting):
It is a new casting method that combines paraffin or foam models with similar size and shape to 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, gasifies model, and liquid metal occupies position of model. After solidification and cooling, it forms a casting.
Process flow: pre-foaming foaming molding dipping coating 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 production of various sizes of complex precision castings, with unlimited alloy types and unlimited production batches. Such as gray cast iron engine housing, high manganese steel elbow, etc.

 

 

Continuous casting: It is an advanced casting method. Its principle is to pour molten metal into a special metal mold called a crystallizer continuously. Solidified (crusted) casting is continuously pulled out from the other end of crystallizer. It can obtain castings of any length or specific length. Process flow:

 

Technical features: 1. Because metal is cooled quickly, crystals are dense, structure is uniform, and mechanical properties are good; 2. It saves metal and improves yield; 3. It simplifies process, eliminates molding and other processes, thereby reducing labor intensity; 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.