The wall thickness of Auto Parts Casting has great influence on its cooling speed. The greater the wall thickness, the slower the cooling rate. If someone uses Sand Casting sample, the average cooling rate of the specimen with 30mm diameter is 20.5'C. while when the diameter is 300mm, its is 1.70CZ. The smaller the cooling rate, the larger the grain size of the castings. The defects of contraction and segregation also increase.
On the same section of the casting parts, the mechanical properties of the surface and center are different. The closer to the center, the lower the mechanical property is. When design casting, except the material, we must also take consider of wall thickness, otherwise, wrong design will lead to unreasonable structure.