【作者】 张进；

【导师】 曲彦平； 李明春；

【作者基本信息】 沈阳工业大学 ， 材料学， 2015， 硕士

【摘要】 如今，各领域对高性能铜合金的需求急剧增加。Cu-Cr-M（M为Zr、Mo、Nb、Y、Gd）合金具备高强度、高导电率和抗磨损性质，是结构与功能兼具的材料，其发展前景十分广阔。Cu-Cr-Zr合金是应用最多的Cu-Cr-M系高强高导铜合金，在半连续铸造生产时，Cu-Cr-Zr合金铸锭最典型的铸造缺陷有气孔、夹杂和热裂纹。这些问题严重影响生产和产品质量，制约了Cu-Cr-Zr合金的大规模生产。本文主要通过数值模拟方法研究了Cu-Cr-Zr铸锭上述缺陷的产生原因及控制方法。现以240mm Cu-Cr-Zr合金圆锭的立式半连续铸造过程作为研究的对象。建立了立式半连铸铬锆铜圆锭的三维模型，通过ANSYS软件热-结构顺序耦合的方式求出铬锆铜半连铸圆锭热应力场。基于应力场模拟结果对铸锭的热裂行为进行了分析与预测，并探讨了浇注温度与水冷强度对铸锭中心裂纹与环状裂纹的影响。建立了求解流场的二维模型，利用FLUENT在满足动量方程、连续性方程和能量守恒方程基础之上的k-ε双方程紊流模型求解，得到不同浇注温度和拉坯速度下的结晶器内流场与合金凝固情况。通过对流场的分析，讨论了不同连铸工艺对铸锭气孔与夹杂缺陷的影响，以及浇注温度与拉速对凝固坯壳的影响。结果表明，结晶器出口上方0.025m铸锭中心易形成中心裂纹；结晶器出口上方0.08m处铸锭易形成半径0.05m的环状裂纹；结晶器出口上方0.025m易产生表面裂纹。适当增加浇注温度将会减少环状裂纹；保证合理的冷却强度能够有效控制中心裂纹与表面裂纹的形成。浇注温度降低和水冷强度增加都会使环流区域缩小，不利于气泡与夹杂的上浮；浇注温度和拉坯速度增加都会导致液面波动加剧而卷入夹杂；提高浇注温度与拉坯速度都会使结晶器出口处坯壳变薄。更多还原

【Abstract】 Nowadays, the demand of high performance copper alloy has increased dramatically.Cu-Cr-M (M=Zr、Mo、Nb、Y、Gd) copper alloy is a class of integrated material with structureand function owing to their high strength, high wear-resistance and high conductive. Copperalloy has a very bright prospects. Cu-Cr-Zr alloy is the most widely used Cu-Cr-M alloy whichis a class of integrated material with high mechanical strength and high conducts electivity.Using the vertical semi-continuous casting to product Cu-Cr-Zr ingot, casting defectsincluding hot tearing, voids and impurities can be found. These problems seriously affectproduction and product quality, restricting the large-scale production Cu-Cr-Zr alloys. Thispaper mainly study the Cu-Cr-Zr ingot above defect causes and control methods throughnumerical simulation methods.The vertical semi-continuous casting of240mm Cu-Cr-Zr cylindrical ingot was takenas the research object. A three-dimensional model describing the vertical semi-continuouscasting of Cu-Cr-Zr cylindrical ingot was established. By the way of thermal-structuralanalysis based on ANSYS, the thermal stress field of the Cu-Cr-Zr cylindrical ingot wasdetermined. Based on the stress field results, the hot crazing behavior was forecasted andanalyzed. The effect of casting temperature and refrigeration strength to the middle crack andcircle crack was also discussed. A two-dimensional model used for flow field simulation wasestablished. The k-ε two equation models were used on the basis of momentum conservationequation，continuity equation and energy conservation equation through FLUENT. By this way,the flow field and solidification conditions under different casting temperature and castingspeed in the mold were acquired. By Analyzing the flow field results, the effect of castingprocess to the void defects and impurity defects was discussed. The effect of castingtemperature and casting speed to the shell thickness was also discussed.The results showed that the crystalline ingot0.025m above the outlet center was easy toform the center of the crack;0.08m above the mold exit at the ingot was easy to form a ringcrack radius of0.05m;0.025m above the mold exit was easy to produce surface cracks.Appropriate to reduce the casting temperature would reduce the cyclic crack; to ensure areasonable cooling intensity could effectively control the formation of a central crack andsurface crack. The simulation results showed that the increase of casting temperature andreduce of refrigeration strength would expand the circulation area in the mold, which was not conductive to the inclusion of bubbles and impurities. The increase of casting temperature andcasting speed would intensify the wave of melt liquid level. The increase of casting speed andcasting temperature would cause the alloy shell at exit of the mold thinning.更多还原