FeNiCrSiMoMnC合金气雾化熔滴的运动与传热行为模拟分析
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摘要
气雾化过程中合金液流被高压气流破碎后,要飞行一段距离才开始冷却凝固,这称为熔滴的飞行过程。本文以重载耐磨耐腐蚀激光熔覆涂层用FeNiCrSiMoMnC合金为对象,通过建立熔滴飞行过程的模型,并对该过程进行数值模拟,计算讨论了雾化气体初始速率、熔滴直径对熔滴的速度、传热系数等参数的影响。结果表明,熔滴速度呈现先增大至最大值后逐渐减小的趋势,且随熔滴直径的增大,熔滴速度最大值点逐渐降低;传热系数与速度曲线相反,呈先下降后上升的趋势,极小值为2kg/d,熔滴直径越大,与气体速度差越小,传热系数越小;随气体初始速率的增大,熔滴最大速度点上移,同时传热系数也逐渐增大。
In gas atomization, the broken droplets usually experience a short flight before their solidification.The flying process of a wear and corrosion resistant FeNiCrSiMoMnC alloy designed for the laser cladding coatings under heavy-duty condition is studied in this work. By a model established based on this process and numerical simulation, the influence of the initial gas velocity and droplet diameter on droplet velocity and heat transfer coefficient was investigated. The result shows that the fused droplet velocity increases with the flight distance at the first stage and then decreases gradually, and the maximum droplet velocity points decrease with the incremental of droplet diameter. On the contrary, the heat transfer coefficient declines sharply before it rises, the minimum value is 2 kg/d. An increasing droplet diameter leads to a smaller velocity difference between the droplet and gas, thus a smaller heat transfer coefficient. The maximum droplet velocity moves up along with the initial gas velocity, at the same time, the heat transfer coefficient also increases.
In gas atomization, the broken droplets usually experience a short flight before their solidification.The flying process of a wear and corrosion resistant FeNiCrSiMoMnC alloy designed for the laser cladding coatings under heavy-duty condition is studied in this work. By a model established based on this process and numerical simulation, the influence of the initial gas velocity and droplet diameter on droplet velocity and heat transfer coefficient was investigated. The result shows that the fused droplet velocity increases with the flight distance at the first stage and then decreases gradually, and the maximum droplet velocity points decrease with the incremental of droplet diameter. On the contrary, the heat transfer coefficient declines sharply before it rises, the minimum value is 2 kg/d. An increasing droplet diameter leads to a smaller velocity difference between the droplet and gas, thus a smaller heat transfer coefficient. The maximum droplet velocity moves up along with the initial gas velocity, at the same time, the heat transfer coefficient also increases.
引文
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[2]马尧,王旭,胡宇,等.惰气雾化过程中粉末破碎机理研究[J].热喷涂技术,2017,9(1):34-36.
[3]欧阳鸿武,陈欣,余文焘,等.气雾化制粉技术发展历程及展望[J].粉末冶金技术,2007,25(1):53-58.
[4]王建军.中国雾化制粉技术现状简介[J].粉末冶金工业,2016,26(5):1-4.
[5]Guo S,Liu Y.Estimation of critical cooling rates for formation of amorphous alloys from critical sizes[J].Journal of Non-Crystalline Solids,2012,358(20):2753-2758.
[6]Behulova M,Mesarosova J,Grgac P.Analysis of the influence of the gas velocity,particle size and nucleation temperature on the thermal history and microstructure development in the tool steel during atomization[J].Journal of Alloys&Compounds,2014,615(6):S217-S223.
[7]Xia Z C,Wang W L,Luo S B,et al.Liquid phase separation and rapid dendritic growth of highly undercooled ternary Fe62.5 Cu27.5 Sn10 alloy[J].Journal of Applied Physics,2015,117(5):044911.
[8]Li B,Liang X,Earthman J C,et al.Two dimensional modeling of momentum and thermal behavior during spray atomization ofγ-TiAl[J].Acta Materialia,1996,44(6):2409-2420.
[9]Bergmann D,Fritsching U,Bauckhage K.A mathematical model for cooling and rapid solidification of molten metal droplets[J].International Journal of Thermal Sciences,2000,39(1):53-62.
[10]Vedovato G,Zambon A,Ramous E.A simplified model for gas atomization[J].Materials Science&Engineering A,2001,304:235-239.
[11]Heringer R,Gandin C A,Lesoult G,et al.Atomized droplet solidification as an equiaxed growth model[J].Acta Materialia,2006,54(17):4427-4440.
[12]李克峰.Fe-6.5Si单相合金雾化液滴凝固行为与组织形成机制[D].上海:上海大学,2014.
[13]Li S,Wu P,Fukuda H,et al.Simulation of the solidification of gas-atomized Sn-5mass%Pb droplets[J].Materials Science&Engineering A,2009,499(1):396-403.
[14]Gutierrez-Miravete E,Lavernia E J,Trapaga G M,et al.A mathematical model of the spray deposition process[J].Metallurgical Transactions A,1989,20(1):71-85.
[15]方鹏均.气雾化Ni-Al合金粉末快速凝固特征及相场模拟[D].四川:西南交通大学,2017.
[16]Lee E S,Ahn S.Solidification progress and heat transfer analysis of gas-atomized alloy droplets during spray forming[J].Acta Metallurgica Materialia,1994,42(9):3231-3243.
[17]Levi C G,Mehrabian R.Heat flow during rapid solidification of undercooled metal droplets[J].Metallurgical Transactions A,1982,13(2):221-234.
[18]Mathur P,Apelian D,Lawley A.Analysis of the spray deposition process[J].Acta Metallurgica,1989,37(2):429-443.
[19]欧阳鸿武,陈欣,余文焘,等.一种表征紧耦合气雾化中熔滴冷却速率的新方法[J].中南大学学报(自然科学版),2007,38(3):375-380.
[20]Perepezko J H,Sebright J L,Hockel P G,et al.Undercooling and solidification of atomized liquid droplets[J].Materials Science&Engineering A,2002,326(1):144-153.
[21]Aissa A,Abdelouahab M,Noureddine A,et al.Ranz and Marshall Correlations limits on heat flow between a sphere and its surrounding gas at high temperature[J].Thermal Science,2015,19(5):1521-1528.