电渣重熔过程熔滴演化的数值模拟分析

Numerical simulation and analysis for molten droplets evolution during electroslag remelting process

电渣锭良好的力学性能缘于电渣锭的成分偏析小、组织致密、夹杂物细小弥散等特点,能有效满足高端装备制造业对高性能金属材料需求。在影响电渣锭质量的诸多因素中,熔池内流体流动是影响电渣重熔冶金效果的关键因素。为了准确描述电渣重熔过程中多物理场耦合现象,采用开源软件OpenFOAM利用直接数值模拟方法、标准k-ε模型和重组化群(RNG)k-ε模型模拟了电渣重熔过程的传输现象。结果表明,直接数值模拟得出的金属熔滴形成和滴落过程与试验结果相一致。电渣重熔渣层流动不是充分发展的湍流,直接数值模拟比k-ε模型更适合描述电渣重熔中的熔渣运动。在熔滴形成过程中,熔滴的速度较大,当钢/渣界面能为0.6 N/m时,熔滴形成较小的圆球状;当钢/渣界面能为0.7、0.8 N/m时,熔滴呈圆锥形;当钢/渣界面能不小于0.9 N/m时,熔滴呈椭球状。当钢/渣界面能小于0.8 N/m时,主熔滴脱离细颈时会形成卫星液滴;当钢/渣界面能不小于0.9 N/m时,主熔滴脱离细颈时不会出现卫星液滴。卫星液滴的出现为电渣锭质量的改善提供了保障。

Excellent mechanical properties of electroslag ingot come from low segregation, dense microstructure, fine and uniformly distributed inclusions in the electroslag ingot. And electroslag products can meet the demands of the high-end equipment manufacturing industry for high-performance metal materials effectively. Among the factors affecting the quality of electroslag ingot, fluid flow in the slag domain is one of the key factors to affect the metallurgical effect of electroslag remelting(ESR). In order to have a deep insight into the coupling phenomenon of multiple physical fields in ESR process accurately, the open source software OpenFOAM was applied to describe the transfer phenomena in ESR process by direct numerical simulation(DNS) method, standard k-ε model and renormalization Group(RNG) k-ε model. The results show that the formation and movement of metal droplets predicted by DNS are in good agreement with experimental results. The molten slag flow in electroslag remelting is not fully developed turbulence, the DNS is a better method to describe the molten slag flow in ESR than k-ε turbulence model. The interfacial energy between steel and slag has significant effects on the droplet evolution. The velocity of droplet is greater during the formation of the droplet. When the interfacial energy between steel and slag is 0.6 N/m, the droplet is like a small sphere. When the interfacial energy between steel and slag is 0.7 N/m and 0.8 N/m, the droplet is like a cone. When the interfacial energy between steel and slag is not less than 0.9 N/m, the droplet is like a spheroidicity. When the interface energy between steel and slag is less than 0.8 N/m, there is a satellite droplet when the primary melt droplets break away from the thin neck. When the interfacial energy between steel and slag is not less than 0.9 N/m, there is no satellite droplet when the primary melt droplet is separated from the thin neck. The appearance of satellite droplet can improve the quality of ESR ingot.