气隙热阻对水平连铸Cu-15Ni-8Sn合金组织和成分分布影响

通过在结晶器底部开设圆弧槽形成气隙热阻来改善水平连铸Cu-15Ni-8Sn合金的组织和成分均匀性。首先基于合金水平连续铸造过程的温度场模拟,分析了不同圆弧槽角度、长度和厚度的结晶器结构对合金结晶区温度分布的影响。然后基于优化了圆弧槽结构的结晶器和未开设圆弧槽的结晶器,进行了直径为65mm铸锭的水平连铸工艺试验。结果表明,随着开设圆弧槽的角度、长度及厚度的增加,上部与下部固液界面的相对水平距离缩小,固液界面与棒坯轴向夹角趋于90°,凝固过程中棒坯的温度场均匀性明显提高。相比于不开设圆弧槽的棒坯,当开槽角度为180°、开槽长度为144mm、开槽厚度为5mm时,上部与下部固液界面的相对水平距离仅为未开槽时的7%。由于温度场分布更合理,棒坯上部和下部的组织和成分均匀性得到显著改善。

Effect of Air Gap Thermal Resistance on Microstructure and Composition Distribution of Horizontal Continuous Casting Cu-15Ni-8Sn Alloy

A method was proposed of opening a circular arc groove at the bottom of the crystallizer to improve the uniformity of microstructure and composition of the horizontal continuous casting Cu-15 Ni-8 Sn alloy.Firstly,based on the temperature field simulation of horizontal continuous casting process of the alloy,influence of crystallizer structure with different arc groove angle,length and thickness was analyzed on temperature distribution in crystallization zone.Then,based on the optimized circular arc groove crystallizer and the crystallizer without the circular arc groove,a horizontal continuous casting process for a 65 mm diameter ingot was carried out.The results reveal that with the increase of the angle,length and thicknessof circular arc groove,the relative horizontal distance of the upper and lower solid-liquid interface is decreased,and the axial angle between the solid-liquid interface and the bar is tended to be 90°.Meanwhile,the temperature field uniformity of the billet is improved obviously during solidification.When the slot angle is 180°,the slot length is 144 mm and the slot thickness is 5 mm for the circular groove,the relative horizontal distance between the upper and lower solid-liquid interfaces is only7%to that without the circular groove.Due to the more reasonable temperature distribution,the uniformity of the microstructure and composition of the horizontal continuous casting Cu-15 Ni-8 Sn ingot is improved greatly.