Study on the Influence of Different Mold Materials on Cast Products

Introduction

Casting technology is essential in modern manufacturing, especially in automotive, aerospace, and mechanical industries. Mold quality directly affects casting accuracy, surface finish, and efficiency. The choice of mold material impacts mold lifespan, microstructure, performance, and defects. This article examines how different mold materials influence cast products, offering guidance for material selection.

1. Common Types of Mold Materials

Currently, the main types of casting molds include:

1. Metal molds (such as cast iron, cast steel, tool steel, aluminum alloy, etc.)
2. Sand molds (such as silica sand, resin sand, ceramic sand, etc.)
3. Plaster molds (mainly used for precision casting)
4. Graphite molds (mainly used for special alloy casting)

Due to differences in physical, chemical, and mechanical properties, different mold materials exhibit unique characteristics during the casting process.

2. Influence of Different Mold Materials on Cast Products

2.1 Influence of Metal Molds on Cast Products

Metal molds (such as cast iron, cast steel, and tool steel) are mainly used in gravity casting, die casting, and low-pressure casting. Their impact on cast products includes:

• Fast cooling rate: Due to the high thermal conductivity of metal molds, the cooling rate of the casting is accelerated, which helps refine the grain structure and improve mechanical properties. However, excessively fast cooling can increase internal thermal stress, leading to cracks or deformation.
• High surface quality: The smooth surface of metal molds results in high casting surface accuracy, reducing the need for post-processing.
• Thermal fatigue affects mold life: Metal molds are prone to thermal fatigue cracks and deformation under high-temperature casting conditions, affecting dimensional accuracy.

2.2 Influence of Sand Molds on Cast Products

Sand casting is one of the most traditional casting methods, widely used for steel, cast iron, and non-ferrous metal casting. The characteristics of sand molds include:

• More uniform casting structure: Due to the low thermal conductivity of sand molds, the slower cooling rate helps reduce internal stress and improve toughness. However, excessively slow cooling may lead to coarse grain structures, affecting mechanical properties.
• Suitable for complex castings: Sand casting allows flexible design of parting lines and gating systems, making it ideal for large and complex-shaped castings.
• Higher surface roughness: Sand materials affect the surface smoothness of castings, usually requiring additional machining to improve surface quality.

2.3 Influence of Plaster Molds on Cast Products

Plaster molds are mainly used for precision casting, such as aerospace and medical industry applications. Their effects include:

• High precision and good surface quality: The fine texture of plaster molds reduces casting surface defects and improves dimensional accuracy.
• Good cooling uniformity: Plaster molds have moderate thermal conductivity, ensuring uniform casting structure and minimizing defects.
• Limited temperature resistance: Plaster molds are suitable for low-melting-point alloys (such as aluminum and magnesium alloys) but are not suitable for high-temperature casting.

2.4 Influence of Graphite Molds on Cast Products

Graphite molds are mainly used for casting titanium alloys, high-temperature alloys, and other special materials, with the following characteristics:

• Excellent high-temperature resistance: Graphite molds can withstand extremely high temperatures, making them suitable for high-melting-point metal casting.
• Good lubricity and demolding performance: The self-lubricating property of graphite molds reduces friction between the mold and the casting, improving product quality.
• Oxidation susceptibility: Graphite molds are prone to oxidation at high temperatures and are typically used in protective atmospheres or vacuum environments.

3. Influence of Mold Materials on Casting Defects

Different mold materials contribute differently to the formation of casting defects:

• Porosity and shrinkage cavities: Metal molds cool quickly, which may cause shrinkage cavities inside the casting, whereas sand molds cool more slowly and help mitigate this issue.
• Cracks and deformation: Metal molds may cause cracks or deformation due to thermal expansion and contraction, whereas sand molds are less prone to such defects.
• Inclusions and sand entrapment: Sand molds are more likely to produce sand inclusion defects, whereas metal molds are more prone to slag inclusions.

4. Conclusion and Recommendations

Different mold materials significantly impact cast products. Therefore, in actual production, the choice of mold material should be based on the intended application, material properties, and cost considerations:

1. For high-precision and small complex castings, such as aerospace components, plaster molds or metal molds are recommended for better dimensional accuracy and surface quality.
2. For large or complex-shaped castings, sand molds are preferred due to their adaptability and ability to reduce stress and deformation.
3. For high-temperature alloy casting, such as titanium alloy parts, graphite molds are recommended to withstand extreme temperatures.
4. For mass production of castings, such as automotive engine housings, metal molds (e.g., aluminum alloy molds) are the best choice due to their high efficiency and cost-effectiveness.

With the development of new mold materials and coating technologies, the application of different mold materials in casting will become more efficient and widespread. Enterprises should optimize mold material selection and processes to improve casting quality and production efficiency.