电极感应熔化气雾化法制备高温合金粉末中非限制式喷嘴的结构优化设计

Optimum structure design of free-fall nozzle in preparation process of superalloy powders by electrode induction gas atomization technology

采用电极感应熔化气雾化制粉法(electrode induction gas atomization,EIGA)制备粉末过程中,非限制式喷嘴的结构设计直接决定气雾化粉末的质量;非限制式喷嘴结构中不合理的喷射角度常常会引起反喷、片状粉、细粉收率低等问题,严重影响粉末的生产效率和质量。采用商业计算流体动力学(computationalfluiddynamics,CFD)软件Fluent,以自主设计的第三代EIGA制备高温合金粉末装置中非限制式喷嘴为研究对象进行数值模拟建模,对带有气体回流区的非限制式喷嘴在熔体初次雾化过程中,喷射角度对反喷现象的影响以及反喷产生的机理进行了研究。结果表明,非限制式喷嘴射流角度过大时,熔体液滴会出现明显反喷现象;当非限制式喷嘴射流角度过小时,熔体液流雾化前过热度不足,生产的粉末球形度较差。因此,在优化设计非限制式喷嘴时,要应尽量控制气体回流区位置低于非限制式喷嘴熔体入口位置,保证合金熔体的过热度,同时防止反喷等现象。

The structure design of free-fall nozzle directly determines the quality of gas-atomized powders in electrode induction melting gas atomization(EIGA)process,the unreasonable jet angle in free-fall nozzle structure often causes the regurgitation phenomenon,the flake powders,and the low yield of fine powders,which seriously affect the production efficiency and quality of powders.The numerical modeling of free-fall nozzle structure in the self-designed third generation of EIGA superalloy powder preparation device was established using Fluent commercial software for computational fluid dynamics(CFD).The effect of jet angle on the regurgitation phenomenon and the regurgitation mechanism of free-fall nozzle with gas flow recirculation were investigated in the initial atomization of melt.In the results,when the jet angle of free-fall nozzle is too large,there is an obvious regurgitation phenomenon;when the jet angle is too small,the superheat of the melt stream before atomization is insufficient,resulting in the poor sphericity of produced powders.Therefore,to ensure the superheat of melt flow and prevent the regurgitation phenomenon,it is necessary to control the recirculation zone position of gas flow to be lower than the melt inlet position of free-fall nozzle.