Types of Casting Process
There are several types of foundry that are typically categorized as follows:
- Common sand mold casting, which has three types: wet sand casting, dry sand casting and chemical hardening sand casting.
- Special Casting, which can be divided into two categories based on the modeling material: casting that uses natural mineral sand as the main modeling material (such as Investment Casting, Clay Casting, Shell Casting, Negative Pressure Casting, Mold Casting Complete, Ceramic Mold Casting, etc.) and casting that uses metal as the main modeling material (such as metal mold casting, pressure casting, continuous casting, low pressure casting, centrifugal casting, etc.).
We will discuss the definitions, characteristics, advantages and disadvantages of each of these casting processes in more detail.
By reading this information, you will better understand casting technology.
1. Sand casting
What is sand casting ?
Sand casting is a method of producing castings in a sand mold and is capable of producing castings of steel, iron and most non-ferrous alloys.
Technological process:
Sand casting process
Technical characteristics:
This method is suitable for producing complex shaped blanks, particularly those that have complex internal cavities. It has a wide range of adaptability and is economical.
Sand casting is the only viable process for producing parts or blanks with low plasticity materials, such as cast iron.
It finds applications in the production of castings such as automotive engine blocks, cylinder heads, crankshafts and other similar components.
2. Precision casting
What is precision casting ?
Precision casting is a casting process that involves creating a pattern from a fusible material, encasing it in multiple layers of refractory materials, melting the mold pattern to obtain a mold with no parting surface, and then , filling it after cooking at high temperature. temperatures.
Technological process:
Investment Casting Process
Advantage is :
- High dimensional accuracy and geometric accuracy;
- High surface roughness;
- It can cast complex castings, and alloy castings are not restricted.
Disadvantages: complicated and high-cost procedures
Application :
Precision casting is suitable for producing small parts with complex shapes and high precision requirements, or for parts that are difficult to process, such as turbine engine blades.
3. Clay Mold Casting
Clay mold casting: a casting method using clay as the main material
Clay mold casting is a traditional casting process that uses clay as the primary material to create a mold for producing castings.
To create a strong cohesive force, clay is mixed with water and materials such as rice husk, rice straw, horse manure and straw ash. After drying in air or in the sun, the clay forms a mold with air outlet pores and high hardness.
The surface of the clay mold is fine and uniform, while the core texture is coarse. Additional materials such as sand, tank slag and broken bricks can be added. The clay mold can be used multiple times, making it a semi-permanent mold.
Clay mold casting is the oldest known casting technology used in China.
4. Shell Casting
Shell Mold Casting is a process that produces castings using thin shell molds. It was invented by German J. Cronin in 1943 and first used in Germany in 1944. Since then, it has been adopted by other countries as well.
The process involves covering a metal formwork heated to 180-280°C with thermally hardened molding sand, typically sand coated with phenolic resin, to create a thin shell mold with a thickness of 6-12 mm. The mold is then heated to solidify it, providing the necessary strength and rigidity.
Once the upper and lower mold shells are fixed or bonded with resin, the mold can be formed without a sandbox. The metal mold used for casting is normally heated to around 300°C, and the molding sand used is resinous sand, which is made with phenolic resin as a binder.
Furthermore, the core can also be formed into a thin-shell core using the same method used to create a thin-shell casting mold. The blowing method is commonly used to manufacture the thin shell core.
5. Ceramic mold casting
Ceramic mold casting is a casting method that uses a ceramic paste to produce castings. The paste is composed of ethyl silicate hydrolyzate and fine refractory sands such as fused quartz, zircon and corundum, known for their pure texture and high thermal stability.
To accelerate the gelation of ceramic paste, calcium hydroxide or magnesium oxide is often included as a catalyst.
Due to the similarities in composition and appearance between the refractory used and the ceramic, this process is often called “ceramic-type” casting. Ceramic mold casting is a new technology developed from traditional sand mold casting.
There are two types of ceramic mold casting:
- The ceramic mold is produced by applying the ceramic paste to the molding plate, coating the sand box, pouring the adjusted paste into the sand box, and lifting the mold after gluing and hardening. The mold is then baked at high temperature to form the casting mold.
- The casting mold is created by pouring ceramic paste into the space between the bushing and the pattern, using a bushing made of sand or metal. This bushing method of using can save a significant amount of ceramic paste and is widely used in production.
6. Metal mold casting
Metal die casting, also known as rigid die casting, is a process in which liquid metal is poured into a metal mold to create castings. The mold is made of metal and can be reused several times, ranging from hundreds to thousands of cycles.
However, metal mold casting has certain limitations on the weight and shape of the castings that can be produced. For example, ferrous metals can only be used to produce castings with simple shapes, and the weight of the casting should not be too large.
Furthermore, the wall thickness is limited, which makes casting smaller parts difficult.
7. Die Casting
What is pressure casting ?
The high-pressure metal liquid is pressed into a precision metal mold cavity at high speed, and the metal liquid is cooled and solidified under pressure to form a casting.
Technological process:
Advantage :
- The metallic liquid is subjected to high pressure and the flow rate is fast during pressure casting.
- Good product quality, stable size and good interchangeability.
- High production efficiency and die casting molds can be used many times.
- It is suitable for mass production with good economic benefits.
Disadvantages:
- Casting tends to produce fine pores and shrinkage.
- Castings have low plasticity and should not operate under impact and vibration loads.
- When pressure casting a high melting point alloy, the mold life is low, which affects the expansion of pressure casting production.
Forms:
Die casting parts were first applied in the automotive industry and instrument industry, and then gradually expanded to various industries, such as agricultural machinery, machine tool industry, electronics industry, national defense industry, computers, medical equipment , watches, cameras and everyday hardware.
8. Low pressure casting
What is low pressure casting ?
Low pressure casting refers to the method of making liquid metal fill a mold under low pressure (0.02 – 0.06 MPa) and crystallize under pressure to form a casting.
Technological process:
Technical characteristics:
The pressure and speed during casting can be adjusted, making it suitable for various casting molds such as metal and sand molds, and for casting various alloys and castings of different sizes.
By adopting a bottom injection filling method, stable filling of metal liquid without splashing is guaranteed. This helps prevent the presence of gas and reduces erosion of the mold walls and core, thereby improving the pass rate of the casting.
The casting solidifies under pressure, resulting in a dense structure, sharp contour, smooth surface and high mechanical properties. This process is particularly beneficial for casting large, thin-walled parts.
Eliminates the need for risers and increases metal utilization rate to 90-98%. Furthermore, it is characterized by low labor intensity, good working conditions, simple equipment and high potential for mechanization and automation.
Application:
Mainly used in traditional products (head, hub, cylinder frame, etc.).
9. Centrifugal Casting
What is centrifugal casting ?
It is a casting method in which molten metal is poured into a rotating mold and the mold is filled and solidified under the action of centrifugal force.
Technological process:
Advantage :
The pouring system and riser system consume minimal metal, leading to better process performance.
In the production of long tubular castings, the absence of a core significantly increases the metal filling capacity.
The resulting casting has high density, few defects (such as pores and slag inclusions) and excellent mechanical properties.
Manufacturing metal castings made up of barrels and sleeves is relatively easy.
Disadvantages:
- There are certain limitations when used in the production of special shaped castings.
- The inner hole diameter of the casting is not accurate, the inner hole surface is rough, the quality is poor, and the machining margin is large.
- Casting is prone to specific gravity segregation.
Application :
Centrifugal casting was initially used for the production of cast pipes, but has since been widely adopted in various sectors such as metallurgy, mining, transportation, irrigation and drainage machinery, aviation, national defense and the automotive industry. This process is used to produce castings of steel, iron and non-ferrous carbon alloys.
Centrifugal casting finds its most common applications in the production of cast iron centrifugal tubes, cylinder liners for internal combustion engines and shaft liners.
10. Gravity Casting
What is gravity casting ?
Gravity die casting is a casting process where liquid metal is poured into a metal mold under the influence of gravity, cooled and solidified to produce a casting.
Technological process:
Advantage :
The metal mold has high thermal conductivity and heat capacity, resulting in fast cooling speed and dense casting structure. Furthermore, it has mechanical properties approximately 15% higher than those of sand casting.
The use of a metal mold allows the production of castings with greater dimensional precision and lower surface roughness, thus improving quality stability.
Furthermore, the use of sand core is minimal or non-existent, leading to better environmental conditions through the reduction of dust and harmful gases, as well as decreasing labor intensity.
Disadvantages:
- The metal mold itself is not breathable, and certain measures must be taken to evacuate the air and air generated by the sand core in the cavity.
- The metal mold has no compromise, and cracks are easy to occur when the casting is solidified.
- Metal molds have a longer manufacturing cycle and higher costs. Therefore, good economic effects can only be demonstrated when mass produced.
Forms:
Metal casting is a method suitable for large-scale production of non-ferrous alloy castings, such as aluminum alloys and magnesium alloys, with complex shapes. It can also be used for the production of iron and steel castings and ingots.
11. Vacuum Die Casting
What is vacuum casting ?
Vacuum die casting is an advanced form of pressure casting that improves the mechanical properties and surface finish of castings by removing or significantly reducing the pores and dissolved gases within them. This is achieved by extracting gas from the mold cavity during the casting process.
Technological process:
Advantage :
- It can eliminate or reduce air holes inside the die casting, improve the mechanical properties and surface quality of the die casting, as well as the coating performance.
- To reduce cavity back pressure, lower specific pressure and alloy with poor casting performance can be used. It is possible to cast larger parts with small machines.
- Improves filling conditions, can cast thinner castings.
Disadvantages:
- The mold sealing structure is complicated, manufacturing and installation are difficult, so the cost is high.
- If the vacuum casting method is not properly controlled, the effect will not be very significant.
12. Squeezing die casting
What is squeezing the die casting ?
Compression casting is a process that involves solidifying liquid or semi-solid metal under high pressure and forming flow to produce the final product or blank directly. This process offers several benefits, including high liquid metal utilization, simplified process, and consistent quality.
Furthermore, it is an energy-efficient metal forming technology that holds great promise for future applications.
Technological process:
Direct pressure casting:
Spray paint, casting alloy, mold clamping, pressurization, pressure retention, pressure relief, mold separation, demolding and blank resetting.
Indirect pressure casting:
Spray coating, mold clamping, feeding, filling, pressurizing, pressure holding, pressure relieving, separation, blank demolding, resetting.
Technical characteristics:
- It can eliminate internal pores, shrinkage and other defects.
- Low surface roughness and high dimensional accuracy.
- It can prevent the occurrence of cracks in the casting.
- Easy to carry out mechanization and automation.
Application:
It can be used to produce various types of alloys, such as aluminum alloy, zinc alloy, copper alloy, nodular cast iron, etc.
13. Lost Foam Casting
What is lost foam casting (also known as solid casting) ?
Lost foam casting is a modern casting technique that uses a combination of paraffin or foam models, which are created to resemble the desired mold in size and shape. These models are then grouped together to form a single unit.
The model assembly is coated with a refractory material, dried and subsequently buried in dry quartz sand that is subjected to vibration.
The liquid metal is then poured onto the sand under vacuum conditions, causing the model to vaporize and the metal to take its place. After the mold solidifies, it is cooled to form the final product.
Technological process:
Pre-foaming → Foam molding → Dip coating → Drying → Shaping → Pouring → Sand falling → Cleaning
Technical characteristics:
- High-precision casting, no sand core, reducing processing time.
- No separating surface, flexible design and high degree of freedom.
- Clean production without pollution.
- Reduce investment and production costs.
Application :
Lost foam casting is a suitable method for producing a variety of precision castings that feature complex structures in different sizes. It offers great versatility, without limitations on the types of alloys used or the size of production batches.
This method has been used successfully to produce a variety of castings, including gray cast iron engine blocks and high manganese steel elbows.
14. Continuous Casting
What is continuous casting ?
Continuous casting is a sophisticated casting process that involves continuously pouring molten metal into a special metal mold called a crystallizer. The solidified casting is then continuously withdrawn from the opposite end of the mold, allowing the production of castings of any length or specific length.
Technological process:
Technical characteristics:
Rapid cooling of the metal results in denser crystalline structures, uniformity and improved mechanical properties, while saving metal and increasing yield.
This process simplifies procedures by eliminating the need for modeling and other steps, reducing labor intensity and significantly minimizing the production space required.
Furthermore, continuous casting is easily automated, which increases production efficiency due to its ease of mechanization.
Application :
Continuous casting can be used to cast steel, iron, copper alloys, aluminum alloys, magnesium alloys and other long castings with constant cross-sectional shapes, such as ingots, plates, rod billets, tubes, etc.
What is the casting process？
Casting is a processing technique in which solid metal is melted and then poured into a specifically shaped mold to solidify. The result, also known as the mold, is removed from the mold after it has solidified, completing the casting process.
Casting is a process in which metal is melted to meet specific requirements and then poured into a mold. The result is a solid casting with predetermined shape, size and performance after cooling, solidifying and cleaning.
Because the casting is nearly formed, machining is reduced or unnecessary, resulting in lower cost and shorter manufacturing time.
Casting is a fundamental process in the modern manufacturing industry.
The casting process generally includes the following:
- Casting mold preparation: Casting mold is made to contain solid casting and can be divided into different types according to the material used, such as sand molds, metal molds, ceramic molds, clay molds and molds. graphite. The number of uses of the mold can also determine its classification as a single mold, semi-permanent mold, or permanent mold. Casting mold preparation is the most significant factor affecting the quality of castings.
- Melting and pouring of molten metal: Molten metal, also known as cast alloy, mainly includes cast iron, cast steel and cast non-ferrous alloys.
- Casting treatment and inspection: This process involves several steps such as removing foreign bodies from the casting core and surface, eliminating sprues and risers, removing burrs, cracks and other projections, heat treatment, shaping, anti-rust treatment and roughness machining .
Most casting materials are metals, including copper, iron, aluminum, tin, lead, etc., which are heated to a liquid state from their solid form. Casting mold materials can be sand, metal or ceramic, and the method used varies depending on the requirements.
Smelting is one of the earliest hot working metal processes known to man, with a history dating back around 6,000 years.
The metals that can be cast include copper, iron, aluminum, tin and lead, while the materials used for common casting molds can be raw sand, clay, water glass, resin and other auxiliary materials.
Some examples of special casting molds include precision casting, lost foam casting, metal mold casting, ceramic mold casting, among others. (Raw sand may include quartz sand, magnesia sand, zirconium sand, chromite sand, forsterite sand, kyanite sand, graphite sand, iron sand, among others.)
Technological process: liquid metal → filling → solidification contraction → casting
Features of the casting process:
- It can produce parts with any complicated shapes, especially those with complicated internal cavity shapes.
- Strong adaptability, unlimited alloy types and almost unlimited casting size.
- Wide source of materials, waste can be remelted and investment in equipment is low.
- High scrap rate, low surface quality and poor working conditions.
How can I fuse parts at home?
To start smelting, you will need a device capable of melting iron or aluminum. If your daily production is low, it is advisable to invest in a small capacity electric oven. An older oven may even be sufficient.
Kerosene furnaces are also suitable for smelting aluminum.
It is important to note that iron and aluminum cannot be smelted in the same furnace as it can be difficult to regulate the material.
However, if material control is not a requirement, it may not be an issue.
Next, you will need a mold that can be custom-made to fit the pieces you want to cast. You will also need sand and a sand mixer is recommended. If you do not purchase a sand mixer, manual mixing is possible.
With these simple modeling tools, you can shape, melt and pour, creating the casting.
Lastly, you will need cleaning tools to remove the leak pipe and smooth out any burrs. Adding a blast roller can improve the appearance of the casting.
