鑄件開裂的主要原因包括鑄造熱裂紋和晶間裂紋。鑄造熱裂紋是由于鑄件結構或鑄造工藝導致各處凝固速度不同，進而產生應力，在鑄件凝固后期將鑄件拉裂形成的裂紋。晶間裂紋則是鑄件的微觀組織中沿晶界產生的裂紋，通常由于低熔點物質在晶界上發生偏析，造成部分液體保持到較低的溫度，隨著變形的增加而引起開裂。

　　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，鑄件開裂還可能由以下因素引起：

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

　　合金雜質含量較高：如硫含量較高或硅含量較低，會導致鋼產生熱脆性，降低韌性和延展性，增加斷裂的風險。

　　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.

　　熱處理不當：加熱溫度和保溫時間對鑄件的組織結構和硬度有重要影響。保溫時間過短會導致鑄件在開箱后激冷，造成斷裂。

　　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：在鑄造過程中，強大的外力碰撞會破壞鑄件組織的連續性，導致斷裂，特別是在鑄件將要脫模時。

　　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.

　　鑄件結構問題：不合理的設計或壁厚不均勻會導致鑄件在凝固過程中產生應力集中，從而開裂。

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

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