10 Common Casting Techniques Types:Definition,Pros and Cons

Casting is a relatively early metal thermal process mastered by humanity, with a history of about 6,000 years. Each of the different processes can produce high-quality parts and offer manufacturing advantages. Understanding each method’s advantages and disadvantages can help select a method designed to meet individual production requirements. Some popular casting processes include sand casting, fusion molding, and die casting. What are the common casting methods? And what are the advantages and disadvantages of each?

1. Die Casting:

The principle of the die-casting process is to use 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.
There are two types of die-casting – cold chamber die-casting and hot chamber die-casting.
The metal liquid is poured into the chamber by hand, or automatic pouring in cold chamber die casting. Then, the pressure injection punch advances and presses the metal into the cavity.
In hot chamber die casting, the chamber is perpendicular to the crucible, and the liquid flows automatically into the chamber through the inlet. The downward movement of the press injection punch pushes the liquid metal into the cavity through the gooseneck tube. After the metal liquid solidifies, the die is opened, and the casting is removed, completing a die casting cycle.

Pros of Die Casting:
① Good product quality. High dimensional accuracy of castings, generally equivalent to grade 6~7, even up to grade 4.
② Good surface finish, generally equivalent to grade 5~8.
Higher strength and hardness, with strength generally 25~30% higher than sand casting.
③ Dimensional stability and good interchangeability; thin-walled and complex castings can be die-cast.
④ High production efficiency, large die-casting machines can die-cast 600 to 700 times in eight hours on average, and small hot chamber die-casting machines can die-cast 3000 to 7000 times in eight hours on average.
⑤ Long life of die-casting type, one pay die-casting type, die-casting bell alloy, life can reach hundreds of thousands of times, even millions of times.
⑥ Easy to perform mechanization and automation; excellent economic effect. Due to the accurate die-casting size, the table is flooded and clean, and other advantages.
⑦ Casting is easy. It can use combination die-casting to other metal or non-metal materials. Both save assembly time and save metal.

Cons of Die Casting:
① Due to the high speed of liquid metal filling the cavity, die casting. The flow state is unstable, so using the general die-casting method, the castings are prone to porosity and cannot be heat-treated.
② Die casting is more difficult for castings with complex internal concavities.
③ Die casting type life is low with high melting point alloys (such as copper and ferrous metals).
④ The main reason for not being suitable for small batch production is the high cost of die-casting type manufacturing, die-casting machine production efficiency, and small batch production is not economical.

A professional die-casting factory can help you solve this problem, V1 Diecast.

2. Sand Casting:

Sand casting uses sand to form and shape the castings. The basic raw materials for sand casting are foundry sand and sand binder.
Sand casting is one of the few processes used for high melting point metals such as certain types of steel, nickel, and titanium. The flexibility and heat resistance of sand casting and the low cost makes it the most widely used casting process.
Castings are made by pouring molten metal into a mold cavity. The sand used to make the casting has a special bonding material that improves its heat resistance and ability to retain its shape. For many years, wet sand, a mixture of sand, coal, bentonite, and water, was mainly used to make castings. Silicon dioxide (SiO2) has become more widely used than wet sand.

Pros of sand casting:
① The clay is abundant and inexpensive.
② Most used clay wet sand can be recycled after proper sand treatment.
③ Short cycle time and high work efficiency in the manufacture of casting patterns.
④ The long service life of the blended sand.
⑤ Wide adaptability. Small, large, simple, complex, single, and large quantities can be used.

Cons of sand casting:
① Low productivity of sand casting because can only pour each sand cast once, and the cast is damaged after obtaining the casting and must be re-molded.
② The rigidity of the castings is not high, and the dimensional accuracy of the castings is poor.
③ Castings easily produce defects such as sand punching, sand trapping, and porosity.

3. Investment Casting:

Investment casting usually refers to the fusible material made in the mold, in the mold surface covered with several layers of refractory materials made of shell. Then the mold melted out of the shell to obtain no parting surface; after high-temperature roasting can be filled with a sand casting program.
Because the mold sample is widely used wax material to manufacture, so often called fusion casting “lost wax casting.” The types of alloys produced by investment casting include carbon steel, alloy steel, heat-resistant alloys, stainless steel, precision alloys, permanent magnet alloys, bearing alloys, copper alloys, aluminum alloys, titanium alloys, and ductile iron.

Pros of Investment casting:

① Improve the utilization rate of metal materials
② Investment casting can significantly reduce the amount of processing of the product’s forming surface and mating surface, saving processing table time and cutting tool material consumption.
③ For alloy materials that are difficult to forge, weld, and cut, especially suitable for casting by the fine casting method.
④ High production flexibility and adaptability Melt casting are suitable for both mass production and small batch or even single piece production.

Cons of Investment casting:
① The casting size cannot be the too large process of complex casting cooling rate is slow.
② Investment casting in all blank forming methods, the most complex process, the casting cost is also very high. 
③  In that case, the part design is reasonable, high casting costs due to reduced cutting, assembly, and savings in metal materials and other aspects of the compensation, the investment casting has good economics.

4. Metal Casting:

Metal casting, also known as hard mold casting, is a casting method in which liquid metal is poured into a metal casting mold to obtain a casting. Casting is made of metal and can be used repeatedly (hundreds to thousands of times). Generally, metal casts are made of cast iron and cast steel. The inner cavity of the casting can be used either as a metal core or a sand core. There are various structures of the metal type, such as horizontal parting, heavy straight parting, and composite parting. The vertical parting is convenient for opening the internal gate and taking out the casting; the horizontal parting is mostly used to produce thin-walled wheel-shaped castings; the upper half of the composite parting is made of two halves of the vertical parting hinged together, and the lower half is a fixed horizontal base plate, which is mainly used in the casting of more complex castings.

Pros of metal casting:

① Good reusability can be “a type of multi-casting,” saving molding materials and hours.
② Castings of high dimensional accuracy, tolerance grade IT12 ~ IT14; surface roughness is low, Ra 6.3m.
③ Metal type casting without sand or with less sand improves labor conditions.

Cons of metal casting:
① Metal type manufacturing costs, long lead time, strict process requirements, not suitable for single small batch production of castings, mainly for the mass production of non-ferrous alloy castings, such as aircraft, automobiles, internal combustion engines, motorcycles, etc.
② With aluminum pistons, cylinder blocks, cylinder heads, oil pump housings, and copper alloy shaft tiles, bushings, etc. For ferrous alloy castings, it is also limited to medium and small castings with simple shapes.

5.Low-pressure Casting:

Low-pressure casting is a method to make liquid metal fill the casting mold under low pressure (0.02~0.06MPa) and crystallize under pressure to form the casting.

The molten metal liquid is poured into the insulated crucible, sealed with a lid, and the liquid is connected to the mold by the liquid-raising tube, and the mold is locked. The mold is opened, and the casting is removed.

low pressure casting

Pros of Low-pressure casting:

① The rising speed of the metal liquid and the crystallization pressure during pouring can be applied to various casting types (such as metal type, sand type, etc.), casting various alloys, and castings of various sizes.
② Castings crystallized under pressure, with dense organization, clear contour, smooth surface, and high mechanical properties are especially beneficial for casting large thin-walled parts.
③ The metal utilization rate is increased to 90%-98%; low labor intensity, good labor conditions, simple equipment, easy-to-realize mechanization, and automation.

Cons of Low-pressure casting:
① Lifting tube life is short; the metal liquid can easily oxidize and produce slag in the insulation process.
② Mainly used for casting some high-quality requirements of aluminum alloy and magnesium alloy castings, such as cylinder block, cylinder head, crankcase, and high-speed internal combustion engine aluminum piston and other thin-walled parts.

6.Centrifugal Casting:

Centrifugal casting is a method in which the metal liquid is poured into the rotating mold, which fills the mold and solidifies under centrifugal force.
According to the position of the rotation axis of the mold in space, the common centrifugal casting can be divided into two kinds: horizontal centrifugal casting: the rotation axis of the mold in the horizontal state or with the horizontal line angle is very small (< 4 °) centrifugal casting. Vertical centrifugal casting: the centrifugal casting when the rotation axis of the mold is in the vertical state is called vertical centrifugal casting. The centrifugal casting where the rotation axis of the mold is at a large angle with both horizontal and vertical lines is called tilted axis centrifugal casting, but it is rarely used.

centrifugal casting process

Pros of Centrifugal casting:

① The core, pouring system, and riser can be eliminated when producing hollow rotating body castings by centrifugal casting.
② Due to the centrifugal force of the liquid metal, the denser metal is pushed to the outer wall, while the less dense gas and slag move to the free surface, forming a directional solidification from the outside to the inside, so the complementary shrinkage conditions are good, the castings are dense and have good mechanical properties.
③ Eliminate and reduce the consumption of the pouring system and riser.

Cons of Centrifugal casting:
① The rough inner free surface of the casting, large dimensional errors, and poor quality.
② Not suitable for alloys with high-density segregation (such as lead bronze) and alloys such as aluminum and magnesium.

7. Lost foam Casting:

It is similar to the size and shape of the casting of paraffin or foam model bonding combination into a model cluster, brush refractory coating and drying, buried in dry quartz sand vibration molding, pouring under negative pressure, so that the model vaporization, liquid metal occupies the model position, solidification and cooling to form a new casting method.
Vanishing mold casting is a new process of nearly no margin, precise molding. The process does not need to take the mold, no parting surface, no sand core, and thus the casting without flying edges, burrs, and pulling mold slope reduce the size error caused by the combination of the core.

Lost foam Casting

Pros of Lost foam casting:

① The life of the metal mold used can be more than 100,000 times, reducing the maintenance cost of the mold.
② No box closing, no mold taking, accurate casting size and shape, good repeatability, features of precision casting, greatly simplifies the molding process, eliminates casting defects and scrap caused by mold taking and box closing, and high surface finish of castings.
③ It is extremely easy to drop the sand, which greatly reduces the workload and labor intensity of sand dropping.

Cons of Lost foam casting:
① Casting material: the order of its good and bad applicability is roughly gray cast iron – non-ferrous alloy – ordinary carbon steel – ductile iron – low carbon steel, and alloy steel.

② The commissioning cycle is too long through the necessary preparation in order not to cause process experiments.

③ Casting size: Consider using the corresponding equipment range (such as a vibrating table or sandbox).High equipment performance requirements, complex technology, large investment.

8. Squeezing Casting:

Extrusion casting, also known as liquid die forging, is to make the molten metal or semi-solid alloy, directly injected into the open die, followed by the closure of the mold to produce filling flow, to reach the external shape of the part, followed by the application of high pressure, so that the solidified metal (shell) plastic deformation, unconsolidated metal is subjected to isostatic pressure. At the same time, high-pressure solidification occurs, and finally obtain, the parts or blanks of the method, the above for direct extrusion casting. Indirect extrusion casting refers to the molten metal or semi-solid alloy through the punch into the closed cavity of the mold, and apply high pressure, so that the crystallization under pressure solidification, and finally obtain the parts or blanks of the method.

Pros of Squeezing casting:

① High dimensional accuracy, low surface roughness, and its level can reach the level of die casting. The liquid metal is formed and solidified under pressure so that the casting fits closely to the cavity wall.
②  In the solidification process, the parts are in a state of compressive stress, which is conducive to the complementary shrinkage of the casting and prevents the generation of casting cracks.
③ No sprue system, less metal loss, high output rate.

④Easy to realize mechanization and automation, which can greatly reduce workers’ labor intensity and improve the casting workshop’s labor conditions.

Cons of Squeezing casting:
① High cost of a hydraulic press.

② Poured into the cast metal fluid inclusions cavity can not be discharged, unsuitable for casting complex parts.

9. Vacuum Casting:

Vacuum casting is a process that uses a vented casting mold. The molten metal flows into the mold by air pressure, and then the air is removed, creating a vacuum. This casting method is mainly used for small parts or jewelry with fine details.
Vacuum mold making is a physical mold-making method that combines vacuum technology with sand casting, relying on plastic film to seal the cavity surface and the back of the sand mold, with the help of vacuum pump pumping to generate negative pressure, causing the pressure difference between the inside and outside of the sand mold to make the molding sand tightly formed, after placing the sand core, closing the mold, casting, waiting for the casting to solidify, lifting the negative pressure or stop pumping, the molding sand will then collapse and get the casting. According to the current field of application, it can be divided into vacuum sealed mold making (V method) and solid vacuum casting (FV method).

vaccum casting

Pros of Vacuum casting:

① It can further reduce the bubbles inside the die-cast product, improve the density of the metal solution, and increase the product’s strength, toughness, and other properties.
② Further increase the flow rate of the metal solution, which facilitates filling parts that are difficult to cast.
③ Very good to improve the solder performance of the die casting, but also can make such as electroplating, oxidation coloring, heat treatment, and other processes easy.

Cons of Vacuum casting:
① Complex mold sealing structure, more difficult to manufacture and install, thus higher cost.

② In Vacuum die-casting methods such as improper control, the effect is insignificant.

10. Continuous Casting:

Continuous casting is a method that continuously pours liquid metal at one end using a through crystallizer and continuously pulls out the molding material from the other end.

Pros of Continuous casting:

① Dense crystallization, uniform organization, and better mechanical properties as the metal is rapidly cooled.
② Simplify the process, eliminating the molding and other processes, thus reducing the labor intensity; the required production area is also greatly reduced.
③ Continuous casting production is easy to achieve mechanization and automation and improve production efficiency.

Cons of Continuous casting:
 The content of oxide inclusions, its average particle size, and maximum particle size are greater than the same level. The content of alumina-like inclusions is high, and the uniformity is poor.

Summary

In this article, we have presented 10 different types of casting techniques. They use different types of casting methods and materials. The type of die casting is also worth mentioning. These 10 different types of casting techniques produce different types of metal castings.

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