铸件开裂的主要原因包括铸造热裂纹和晶间裂纹。铸造热裂纹是由于铸件结构或铸造工艺导致各处凝固速度不同，进而产生应力，在铸件凝固后期将铸件拉裂形成的裂纹。晶间裂纹则是铸件的微观组织中沿晶界产生的裂纹，通常由于低熔点物质在晶界上发生偏析，造成部分液体保持到较低的温度，随着变形的增加而引起开裂。

　　The main causes of cracking in castings include casting hot cracks and intergranular cracks. Casting hot cracks are caused by different solidification rates in various parts due to the structure or casting process of the casting, resulting in stress and the formation of cracks in the casting during the later stage of solidification. Intergranular cracks are cracks that occur along grain boundaries in the microstructure of castings, usually due to the segregation of low melting point substances at grain boundaries, causing some liquids to remain at lower temperatures and leading to cracking with increasing deformation.

　　此外，铸件开裂还可能由以下因素引起：

　　In addition, cracking of castings may also be caused by the following factors:

　　合金杂质含量较高：如硫含量较高或硅含量较低，会导致钢产生热脆性，降低韧性和延展性，增加断裂的风险。

　　High impurity content in alloys, such as high sulfur content or low silicon content, can cause thermal brittleness in steel, reduce toughness and ductility, and increase the risk of fracture.

　　热处理不当：加热温度和保温时间对铸件的组织结构和硬度有重要影响。保温时间过短会导致铸件在开箱后激冷，造成断裂。

　　Improper heat treatment: Heating temperature and holding time have a significant impact on the microstructure and hardness of castings. A short insulation time can cause the casting to cool rapidly after opening the box, resulting in fracture.

　　外力碰撞：在铸造过程中，强大的外力碰撞会破坏铸件组织的连续性，导致断裂，特别是在铸件将要脱模时。

　　External force collision: During the casting process, strong external force collision can damage the continuity of the casting structure, leading to fracture, especially when the casting is about to be demolded.

　　铸件结构问题：不合理的设计或壁厚不均匀会导致铸件在凝固过程中产生应力集中，从而开裂。

　　Structural issues with castings: Unreasonable design or uneven wall thickness can lead to stress concentration during solidification, resulting in cracking.

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