单晶铸件凝固过程工艺优化的数值模拟

采用ProCAST软件系统研究了LMC(Liquid Metal Cooling)以及HRS(High Rate Solidification)工艺下,不同工艺参数对单晶铸件凝固过程中纵向温度梯度、温度梯度角、凝固界面位置的影响。结果表明:HRS工艺受型壳厚度影响很小,型壳表面的辐射散热是HRS工艺的主要影响因素,型壳的导热或者型壳和合金之间的换热是LMC工艺的主要影响因素;提高保温炉温度有利于提高纵向温度梯度;拉速是影响定向凝固最重要的参数,随拉速的增加,单晶铸件的纵向温度梯度先增大后减小,因此,制备不同合金铸件时应当采用不同的拉速;不同浇注温度时,经过10min的静置时间后,单晶铸件的初始温度分布趋于一致,对后续凝固过程影响很小。提出了以纵向温度梯度G∥、温度梯度角θ以及凝固界面位置Rp考察定向凝固工艺参数优劣的标准,纵向温度梯度、温度梯度角、凝固界面位置是评价定向凝固参数优劣的有效手段。

Numerical Simulation on Parameters Optimization of Single Crystal Castings Solidification Process

A new method is proposed to evaluate the process parameters by the solid‐liquid interface position ,thermal gradient angle and the axial thermal gradient .The effects of the process parameters on the solid‐liquid interface position ,thermal gradient angle and the axial thermal gradient were simu‐lated by ProCAST using LMC(Liquid Metal Cooling ) and HRS(High Rate Solidification) processes . The results show that HRS process is little affected by the mold thickness ,the dominant heat transfer factor in HRS is radiation from the mold surface ,and the dominant heat transfer factor in LMC either mold thermal conductivity or mold‐metal interface heat transfer ;increasing furnace temperature is beneficial to increase the axial thermal gradient ;the withdrawal rate is the most important process pa‐rameter which significantly affects the thermal field during solidification ,as the withdrawal rate in‐creases ,the axial thermal gradient first increases and then decreases ,therefore ,it is necessary to ap‐ply different withdrawal rates for different alloys .After holding 10min at different pouring tempera‐tures ,a uniform temperature is achieved ,and it has slight influence on the subsequent solidification . It has been put forward that the solid‐liquid interface position ,thermal gradient angle and the axial thermal gradient can be utilized as a serial of efficient analysis standards for optimization of process conditions independent of casting geometry .