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Sand casting is one of the oldest and most widely used methods in the metal casting process. Its basic principle is to pour molten metal into a pre-prepared sand mold, and then take it out after the metal cools and solidifies to obtain the desired shape. of castings. The core of this process lies in the preparation of sand molds, and the material selection of sand molds is directly related to the quality, production efficiency and cost of castings. This article will introduce in detail the mainmaterials used in sand casting.

What Materials Are Used in Sand Casting?

Sand casting is compatible with many materials; however, it is more commonly used with metals. Choosing the right material depends on casting performance, production volume, etc. The most commonly used materials in sand casting include:

1.Aluminum

Aluminium is one of the most commonly used sand casting materialsdue to its mechanical properties. It has a high strength to weight ratio, low density, corrosion resistance and castability. Common aluminium sand casting alloys include ADC12, AL6061 and A356. Aluminium sand casting requires base sands such as silicochromite and chromite.

2.Bronze

Bronze, an alloy of copper and tin, is a common material for sand casting.The sand casting of bronze depends on its different alloys, which are based on the ratio of copper to tin or the presence of other elements such as aluminium, zinc, nickel and iron. Bronze alloys suitable for sand casting include aluminium bronze, manganese bronze and silicon bronze. Each bronze alloy has its own properties. For example, aluminium bronze and manganese bronze have high strength, corrosion resistance, wear resistance and good toughness. Manganese bronze has corrosion resistance, wear resistance and exceptional mechanical properties. Silicon bronze, on the other hand, has good machinability and castability.

3.Brass

Brass is an alloy of copper and zinc which, due to its high elemental content, is resistant to rust and corrosion. Brass does not contain iron or iron oxide. Brass has good electrical conductivity and tensile strength. Brass is therefore a very popular sand casting material for parts that require such properties.

4.Zinc

Zinc is a strong material with high hardness, corrosion resistance and castability. In addition, the strength and hardness of zinc makes it easy to produce thinner walled parts after alloying.Zinc is easier to sand cast than aluminium.

5.Lead

Lead was one of the most commonly used materials for sand casting by the Romans. It is heavy and resistant to corrosion. However, it has certain health risks and must be used under strict conditions. Nevertheless, it is suitable for making small and medium-sized parts such as pipe fittings.

6.Copper

Copper is an expensive, strong, heavy material known for its electrical and thermal conductivity. Because copper does not rust and is highly malleable, it is suitable for sand casting, such as plumbing fixtures.

7.Iron

Iron is commonly used in sand casting due to its fluidity and low volumetric/linear shrinkage. However, its poor mechanical properties, high compressive strength and low tensile strength make it unsuitable for parts with complex shapes or asymmetric structures. For example, grey iron castings have excellent castability and machinability; ductile iron castings have good fluidity and high shrinkage; andmalleable iron castings have excellent ductility, machinability, toughness and corrosion resistance.

8.Mild Steel

Mild steel has a lower carbon content (0.15% to 0.30%), which gives it greater ductility and malleability.Mild steel is widely used because of its low cost and ease of casting. However, porosity, shrinkage and cracking make it difficult to machine.

9.Stainless Steel

Stainless steel’s corrosion resistance, durability and strength make it a popular choice for sand casting. It also has a low coefficient of thermal expansion, which improves precision, high tolerances and dimensional stability. However, it is an expensive metal and its high strength and hardness make parts difficult to eject from sand moulds.

What Binders and Additives Are Essential in Sand Casting?

In sand casting,binders and additives play a vital role. They can affect the strength, stability, heat resistance of the sand mold and the quality of the casting. Here is a detailed look at some of the necessary binders and additives:

1.Adhesive

Clay	Clay is a natural mineral binder that binds casting sand together to form a sand mold with a certain degree of strength and stability. Clay binders are low-cost, widely available, and environmentally friendly. They are one of the commonly used binders in sand casting.
Resin	Resin is a synthetic organic adhesive that reacts chemically with a specific curing agent to form a solid sand mold. Resin adhesives have the characteristics of high strength, quick drying, and water resistance, and are suitable for producing high-precision, high-quality castings, especially large and complex-shaped castings.

2. Additives

In sand casting, in addition to the binder, some other additives need to be added to enhance the mold performance, such as permeability, thermal stress resistance, etc. These additives include but are not limited to:

Release agent	Also known as separating agent, it can reduce the adhesion between the sand mold and the casting, making the casting easily fall off from the sand mold, avoiding damage to the casting and loss of the sand mold. Commonly used release agents include asphalt phenol, paraffin wax and silicone oil.
Plasticizer	It can increase the contact area between sand particles, thereby improving the plasticity and extrudability of sand, making the sand mold easier to form and avoiding problems such as poor molding and breakage. Commonly used plasticizers include gel graphite, corn starch and sodium alginate.
Thermal stabilizer	It can enhance the high temperature resistance of sand so that the sand will not lose shape and stability at high temperatures, thus ensuring the quality and surface finish of castings. Commonly used heat stabilizers include ceramic particles, alkali metal compounds and hydroxypropyl methylcellulose.

What Equipment Is Used in Sand Casting?

Theequipment used in sand castingmainly includes the following categories:

1. Sand mixing equipment:Sand mixing machine is used to mix sand (special modeling soil) and appropriate amount of clay evenly to prepare sand mold materials suitable for casting. At the same time, tools such as shovels and sieves are also needed to assist in thesand mixing process, such as screening sand and handling mixed materials.
2. Mold making equipment:engraving machine, used to make molds based on samples or drawings provided by customers. Engraving machines can engrave materials such as wood, plastic sheets, and metal blocks to create precise molds.
3. Core making equipment:oven, used for firing cores. For castings with internal cavities, a core needs to be made to fill the cavity in the mold. In addition,materials such as aluminum core boxes and coated sand are also required.
4. Molding equipment:Molding machine, used to compress the mixed sand material and shape it around the mold. The molding machine can greatly improve the molding efficiency and reduce the workload of workers. At the same time, tools such as a sandbox, bottom plate, scraper, shovel, dip pen, V-shaped iron sheet for opening gates, brushes, and pore needles are also needed to assist the modeling process.
5. Melting Equipment:Electric furnace, used to melt metal. The size and power of the electric furnace are determined by production needs.
6. Pouring equipment:ladle, used to contain and transfer molten metal. There are large and small ladles for molten iron to facilitate the transfer of molten metal from the electric furnace to the mold. For large foundries, lifting equipment such as aerial cranes are also needed to lift large castings or molds and assist in the pouring process.
7. Cleaning equipment:Sandblasting machine,used to clean sand and impurities on the surface of castingsand perform surface roughening.

How Does the Choice of Materials Impact Sand Casting?

Material selection plays a decisive role in sand casting, which directly affects the quality, performance and production efficiency of castings. The following is a specific analysis of the impact of material selection on sand casting:

• Casting surface quality:The surface roughness of modeling materials such as quartz sand is small, and castings with higher surface quality can be obtained by using it. Refractory clay sand is relatively coarse, and the surface quality of its molded castings is relatively poor.
• Dimensional accuracy of castings:The shrinkage rate of the molding material will affect the dimensional accuracy of the castings. Different molding materials have different shrinkage rates, so choosing the right material is critical to ensuring the accuracy of your casting dimensions.
• Internal structure and mechanical properties of castings:Differentmolding materialswill affect the formation of the internal structure of castings during the cooling process. For example, graphite sand has good thermal conductivity and can promote the uniform formation of the internal structure of the casting. The choice of molding material also affects the mechanical properties of the casting. For example, graphite sand will not react chemically with iron during the cooling process, so the cast iron parts have high strength and hardness; while alumina quartz sand will embed into the surface of the casting to form a chemical bond, increasing the toughness of the casting.
• Strength and stability of the sand mold:The mud content, particle composition, particle morphology and other characteristics of the original sand will affect the strength and permeability of thesand mold. Excessive mud content may cause the sand mold to become brittle and have poor mold draftability; unreasonable particle composition may cause the sand mold to expand thermally and easily cause expansion defects. The choice of adhesive is also critical. Binders such as clay and resin can enhance the strength and stability of the sand mold and ensure that the sand mold will not crack or deform during thepouring process.

What Are the Applications of Sand Casting Materials?

Sand casting is a common and widely used casting methodsuitable for the production of a variety of metals and alloys. The following is a detailed summary of sand casting material applications:

Auto industry

In the field of automobile manufacturing,sand casting is an important means of producing automobile parts with complex designs. For example, key components such as engine blocks and gearbox housings are often manufactured using sand casting technology.

Aerospace industry

Sand casting is also popular in the aerospace industry. It is often used to manufacture aircraft engine components and structural components that require extremely high strength and precision. Specifically, turbine blades, casings, brackets and various accessories can be accurately manufactured through sand casting technology.

Build the app

In the construction industry, sand casting technology is often used to produce key products such as pipe fittings and manhole covers. The sand casting process gives these products exceptional durability and sturdiness, ensuring their long life in construction applications.

Piping system components

In the field of piping systems,sand casting technology shows its unique advantages. It is widely used in the manufacture of core components such as valve bodies, pipe connectors and couplings, which play a vital role in pipeline systems.

Extensive manufacturing of metal products

Globally, the sand casting process occupies an important position in the manufacture of metal products. From cold weapons like swords to everyday items like pots and cauldrons, sand casting plays a key role. Although other manufacturing methods have gradually come to prominence as technology develops, sand casting has maintained its irreplaceable status due to its high cost-effectiveness and suitability for mass production.

FAQs

1.What types of sand are mainly used in sand casting?

The most commonlyused sand in sand casting is siliceous sand, which is widely used because of its high temperature resistance, high compressive strength, and ease of processing. When the high-temperature performance of silica sand cannot meet specific requirements, special sands such as zircon sand, chromite sand, and corundum sand will also be used.

2.What types of binders are there for molding sand?

There are various types of binders for molding sand, the most commonly used of which is clay. In addition, there are various drying oils or semi-drying oils, water-soluble silicates, phosphates, and various synthetic resins, which can be used as binders for molding sand to improve the strength of the sand mold and core.

3.What is the main function of coatings used in sand casting? What are its ingredients?

The coatings used insand casting mainly play a role in improving the surface quality of castings. The main components of the coating are powdery materials and binders with high refractory resistance and good high-temperature chemical stability. In addition, there are also carriers (such as water or other solvents) and various add-ons for easy application. These components work together to form a protective layer to prevent defects such as sand sticking and sand inclusion in the casting during the pouring process.

4.What is the difference in the materials used between clay wet sand molding and clay dry sand molding?

The main difference in the materials used between clay wet sand type and clay dry sandtype is the moisture content. The molding sand of the clay wet sand mold has moderate moisture in the wet state, with clay and an appropriate amount of water as the main binder. After the sand mold is made, it is directly molded and poured in the wet state. The wet moisture content of the molding sand of clay dry sand molds is slightly higher than that of wet molds. After the sand mold is made, it needs to be coated with refractory paint and dried. After it cools, it can be molded and poured.

Summary

A wide variety of materials are used in mold casting, including different types of sand, binders, coatings, and add-ons. The selection and use of these materials has an important impact on the quality and production efficiency of castings. Therefore, when performing sand casting, appropriate casting materials should be selected based on comprehensive considerations such as the shape, size, material, and production needs of the casting.

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