定向洛伦兹力对激光熔覆熔池排气的影响
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摘要
采用稳态磁场和电场耦合形成定向洛伦兹力,基于多物理场耦合原理及网格变形法建立了定向洛伦兹力作用下的熔池模型,采用离散元法模拟了熔池内的气泡运动过程。与熔覆工艺条件相同但未施加外场时比较,结果显示,定向洛伦兹力具有优异的气孔调控能力。当洛伦兹力向上时,熔池的最高流速被抑制了62.5%,气泡运动方向向下偏转,熔覆层的气孔明显增多;当洛伦兹力向下时,熔池的最高流速被抑制了25%,但气泡因所受浮力增大而逸出加速,熔覆层无气孔。仿真结果与实验结果吻合良好,验证了仿真模型的可靠性。
The stationary magnetic and electric fields are coupled to form the directional Lorentz force.Based on the multi-physics field coupling theory and the mesh deformation method,the molten pool model under the effect of the directional Lorentz force is built,and the bubble movement process in molten pool is simulated by the discrete element method.The comparison of numerical results with and without directional Lorentz force but both under the same laser cladding process conditions indicates that the directional Lorentz force possesses an excellent ability to regulate pores.When the direction of the Lorentz force is upward,the maximum velocity of molten pool is suppressed by 62.5%,the gas bubble movement direction deflects downward,and the pores in cladding layers increase obviously.When the direction of the Lorentz force is downward,the maximum speed of molten pool is suppressed by 25%.Nevertheless,for the reason of the increase of the bubble buoyancy,the bubble is accelerated and escapes from the melting pool,and a dense cladding layer without any pores is obtained.The simulation results agree well with the experimental ones,which confirms the reliability of this simulation model.
The stationary magnetic and electric fields are coupled to form the directional Lorentz force.Based on the multi-physics field coupling theory and the mesh deformation method,the molten pool model under the effect of the directional Lorentz force is built,and the bubble movement process in molten pool is simulated by the discrete element method.The comparison of numerical results with and without directional Lorentz force but both under the same laser cladding process conditions indicates that the directional Lorentz force possesses an excellent ability to regulate pores.When the direction of the Lorentz force is upward,the maximum velocity of molten pool is suppressed by 62.5%,the gas bubble movement direction deflects downward,and the pores in cladding layers increase obviously.When the direction of the Lorentz force is downward,the maximum speed of molten pool is suppressed by 25%.Nevertheless,for the reason of the increase of the bubble buoyancy,the bubble is accelerated and escapes from the melting pool,and a dense cladding layer without any pores is obtained.The simulation results agree well with the experimental ones,which confirms the reliability of this simulation model.
引文
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[25]Zhong C,Gasser A,Schopphoven T,et al.Experimental study of porosity reduction in high deposition-rate laser material deposition[J].Optics&Laser Technology,2015,75(1):87-92.
[26]Zhang K,Liu K Y,Ye Z T,et al.Effect of protective atmosphere on pores in the remelted zone during laser remelting gray cast iron[J].Chinese Journal of Lasers,2018,45(1):0102005.张坤,刘克元,叶正挺,等.气氛保护对灰铸铁激光重熔区域气孔的影响[J].中国激光,2018,45(1):0102005.
[2]Liu F C,Lin X,Yang G L,et al.Microstructures and mechanical properties of laser solid formed nickel base super alloy Inconel 718 prepared in different atmospheres[J].Acta Metallurgica Sinica,2010,46(9):1047-1054.刘奋成,林鑫,杨高林,等.不同气氛激光立体成形镍基高温合金Inconel718的显微组织和力学性能[J].金属学报,2010,46(9):1047-1054.
[3]Bachmann M,Avilov V,Gumenyuk A,et al.About the influence of a steady magnetic field on weld pool dynamics in partial penetration high power laser beam welding of thick aluminium parts[J].International Journal of Heat and Mass Transfer,2013,60:309-321.
[4]Bachmann M,Avilov V,Gumenyuk A,et al.Numerical assessment and experimental verification of the influence of the Hartmann effect in laser beam welding processes by steady magnetic fields[J].International Journal of Thermal Sciences,2016,101:24-34.
[5]Wang L,Yao J,Hu Y,et al.Suppression effect of a steady magnetic field on molten pool during laser remelting[J].Applied Surface Science,2015,35(1):794-802.
[6]Schneider A,Avilov V,Gumenyuk A,et al.Laser beam welding of aluminum alloys under the influence of an electromagnetic field[J].Physics Procedia,2013,41:4-11.
[7]Zhou J,Tsai H L.Effects of electromagnetic force on melt flow and porosity prevention in pulsed laser keyhole welding[J].International Journal of Heat and Mass Transfer,2017,50(22):17-35.
[8]Xie D Q.The process research on pulsed current assisted laser rapid prototyping nickel-based superalloy[D].Nanjing:Nanjing University of Aeronautics and Astronautics,2014.谢德巧.脉冲电流辅助激光快速成形镍基高温合金的工艺研究[D].南京:南京航空航天大学,2014.
[9]Wang C Q,Liu H X,Zhou R,et al.Characteristic behaviors of particle phasesin nicrbsi-tic composite coating by laser cladding assisted by mechanial vibration[J].Acta Metallurgica Sinica,2013,49(2):221-228.王传琦,刘洪喜,周荣,等.机械振动辅助激光熔覆NiCrBSi-TiC复合涂层中颗粒相行为特征[J].金属学报,2013,49(2):221-228.
[10]Qin L Y,Yang G,Bian H Y,et al.Experimental study on electromagnetic stirring assisted laser metal depasition titanium alloy[J].Chinese Journal of Lasers,2014,41(3):0303004.钦兰云,杨光,卞宏友,等.电磁搅拌辅助激光沉积成形钛合金试验研究[J].中国激光,2014,41(3):0303004.
[11]Wang W,Liu Q,Yang G,et al.Numerical simulation of electromagnetic flow,temperature field and flow field in laser molten pool with electromagnetic stirring[J].Chinese Journal of Lasers,2015,42(2):0202007.王维,刘奇,杨光,等.电磁搅拌作用下激光熔池电磁场、温度场和流场的数值模拟[J].中国激光,2015,42(2):0202007.
[12]Hoadley M P.Finite element simulation of laser surface treatments including convection in the melt pool[J].International Journal of Numerical Methods For Heat&Fluid Flow,1994,4(1):61-83.
[13]He X,Mazumder J.Transport phenomena during direct metal deposition[J].Journal of Applied Physics,2007,101(5):053113.
[14]Cho W-I,Na S-J,Thomy C,et al.Numerical simulation of molten pool dynamics in high power disk laser welding[J].Journal of Materials Processing Technology,2012,212(1):262-275.
[15]Che D F,Li H X.Multiphase flow and its application[M].Xi′an:Xi′an Jiaotong University Press,2007.车德福,李会雄.多相流及其应用[M].西安:西安交通大学出版社,2007.
[16]Yang Z,Wang A,Weng Z,et al.Porosity elimination and heat treatment of diode laser-clad homogeneous coating on cast aluminum-copper alloy[J].Surface&Coatings Technology,2017,321:26-35.
[17]Dong G.Numerical simulation of molten pool in coaxial powder-feed laser cladding[D].Changsha:Hunan University,2013.董敢.同轴送粉激光熔覆熔池数值模拟[D].长沙:湖南大学,2013.
[18]Wang L,Hu Y,Song S Y,et al.Suppression effect of a steady magnetic field on surface undulation during laser remelting[J].Chinese Journal of Lasers,2015,42(11):1103005.王梁,胡勇,宋诗英,等.稳态磁场辅助对激光熔凝层表面波纹的抑制作用研究[J].中国激光,2015,42(11):1103005.
[19]Li S,Xiao H,Liu K,et al.Melt-pool motion,temperature variation and dendritic morphology of Inconel 718during pulsed-and continuous-wave laser additive manufacturing:A comparative study[J].Materials&Design,2017,119:351-360.
[20]Iida T,Guthrie R I L.The physical properties of liquid metals[M].New York:Oxford University Press,1988.
[21]Shuja S Z,Yilbas B S.Laser produced melt pool:Influence of laser intensity parameter on flow field in melt pool[J].Optics&Laser Technology,2011,43(4):767-775.
[22]Bachmann M,Avilov V,Gumenyuk A,et al.Experimental and numerical investigation of an electromagnetic weld pool control for laser beam welding[J].Physics Procedia,2014,56:515-524.
[23]Zhang H W,Li Y X.Study on bubble nucleation in liquid metal[J].Acta Physica Sinica,2007,56(8):4865-4871.张华伟,李言祥.金属熔体中气泡形核的理论分析[J].物理学报,2007,56(8):4865-4871.
[24]Ni B,Luo Z G,Zou Z S.Thermodynamics analysis on bubble attachment to soild wall in liquid[J].The Chinese Journal of Process Engineering,2008,8(1):140-143.倪冰,罗志国,邹宗树.固壁上液体内气泡附着的热力学分析[J].过程工程学报,2008,8(1):140-143.
[25]Zhong C,Gasser A,Schopphoven T,et al.Experimental study of porosity reduction in high deposition-rate laser material deposition[J].Optics&Laser Technology,2015,75(1):87-92.
[26]Zhang K,Liu K Y,Ye Z T,et al.Effect of protective atmosphere on pores in the remelted zone during laser remelting gray cast iron[J].Chinese Journal of Lasers,2018,45(1):0102005.张坤,刘克元,叶正挺,等.气氛保护对灰铸铁激光重熔区域气孔的影响[J].中国激光,2018,45(1):0102005.