铸件凝固后期液膜抗拉能力分析
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摘要
金属凝固后期是热裂纹产生的危险期,晶粒之间的液膜对热裂有一定的抵抗作用,研究液膜的抗拉能力的影响因素,无疑对提高铸件的质量有着积极意义。本文采用微积分方法建立了液膜抗拉能力与曲率半径的解析式,通过质量守恒条件推导了液膜曲率半径与晶粒边界间距的关系,从而间接建立了液膜抗拉能力和晶粒边界距离的关系。对以上解析关系的分析表明:在没有液态金属补充的情况下,液膜抵抗能力与液膜表面曲率半径有关,而液膜的曲率半径随晶粒边界间距的增加而变小,并存在一个极值,但此极值和现有文献的结果不同,此时液膜抗拉能力达到最大,如果凝固时收缩拉力不超过此极值,则晶粒不会产生热裂纹,这为凝固工艺的制定提供了重要参考。
The later stage of metal solidification is a dangerous period for hot crack generation. Investigating the tensile strength of liquid films is important to improve casting quality given that the liquid film between crystal grains has a certain preventative effect on thermal cracking. The analytic formula is obtained through a calculus-based method, and the relationship between the radius of the curvature of the liquid film and grain spacing is first quantified based on mass conservation. Moreover, the indirect relationship between the tensile strength of the liquid film and grain spacing is obtained. Analytical results show that the radius of the curvature of the liquid film gradually decreases as the grain spacing is increased in the absence of liquid metal supplementation, and an extremum of the radius of curvature exists. However, the extreme value obtained in this study is different from that obtained in a previous study. The maximum of the tensile strength of the liquid film corresponds to the extremum of the radius of curvature. Crystal grains will not produce hot cracks if the shrinkage tension does not exceed this maximum value during solidification. This study provides an important reference for the establishment of the solidification process.
The later stage of metal solidification is a dangerous period for hot crack generation. Investigating the tensile strength of liquid films is important to improve casting quality given that the liquid film between crystal grains has a certain preventative effect on thermal cracking. The analytic formula is obtained through a calculus-based method, and the relationship between the radius of the curvature of the liquid film and grain spacing is first quantified based on mass conservation. Moreover, the indirect relationship between the tensile strength of the liquid film and grain spacing is obtained. Analytical results show that the radius of the curvature of the liquid film gradually decreases as the grain spacing is increased in the absence of liquid metal supplementation, and an extremum of the radius of curvature exists. However, the extreme value obtained in this study is different from that obtained in a previous study. The maximum of the tensile strength of the liquid film corresponds to the extremum of the radius of curvature. Crystal grains will not produce hot cracks if the shrinkage tension does not exceed this maximum value during solidification. This study provides an important reference for the establishment of the solidification process.
引文
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