纯钛VAR熔池形貌和凝固组织模拟及其工业验证

Simulation and Industrial Validation of Molten Pool Morphology and Solidification Structure of Pure Titanium during VAR Process

运用ANSYS和μMat Ic软件分析了980 mm纯钛锭VAR过程中熔池形貌以及凝固组织的变化规律。模拟计算结果表明:起弧阶段的熔池很小,呈浅U型;随后熔池形貌由U型逐渐变为V型;当坩埚内热量输入与输出达到平衡时,熔炼进入稳定阶段,熔池深度和宽度不再变化;补缩过程中,熔池不断缩小直至消失。凝固组织的变化规律为:与坩埚壁接触的钛液快速冷却形成细晶组织;随着熔炼的进行,以枝晶形状生长的部分细晶粒最终形成具有一定择优取向的柱状晶;铸锭中心区域和液固临界区域,晶粒直接在金属液内形核并长大,形成的等轴晶粒阻碍了柱状晶的生长,发生柱状晶-等轴转变。通过解剖工业铸锭验证,熔池形貌和凝固组织与数值模型的计算结果相吻合。

Change rules of molten pool morphology and solidification structure of 980 mm pure titanium ingot during VAR process were studied by using ANSYS and μMat Ic softwares. The simulation results show that the molten pool is very small with shallow U type at the arc starting stage,then gradually changes from U to V type. The depth and width of molten pool no longer change in the stable stage of smelting when the equilibrium between heat input and output in the crucible is attained. During the filling process,the molten pool gradually shrinks and disappears. The evolution of solidification structure is that fine crystal structure is formed from the liquid contacted with the crucible wall by rapid cooling,and a part of the fine crystals growing as arborization finally form into columnar crystals with a certain preferential orientation. In the center region of the ingot and the critical region of liquid-solid phase,nucleation and growth of crystals directly occur in the metal liquid,and the formed equiaxed crystals block the growth of columnar crystals coupled with transformation between equiaxed and columnar crystals. By anatomizing the industrial ingot,the simulation results of numerical model are with good accordance with the industrial tests.