The Research Of Molten Pool Temperature Field And Fluid Field Of CMT Welding Between Aluminum Alloy And Steel

Aluminum and steel with composite structure have comprehensive advantages in the high strength, light weight, corrosion resistence and so on, which can be applied in the field of aerospace, shipbuilding, automobile industry, energy-saving, emission reduction.According to the difference of large physical performance between steel and aluminium, and the formation of brittle intemetallic compounds, the study of aluminum/steel dissimilar metal welding has important practical value. CMT welding is a new technology of low heat input welding, which can realize the aluminum/steel metal brazing welding. CMT welding uses the numerical simulation to study the molten pool temperature field and fluid field of aluminum/steel dissimilar metal welding and have quantitative analysis about the process of droplet transition, the fluid action in the welding and heat transferation to obtain the measured results hardly to get experimental methods.5083 aluminum alloy and EH36 galvanized steel with the thick of 4mm are as the researching object and ER4043 silicon aluminum is used for welding wire with CMT welding in this paper. Combining the craft characteristics of CMT welding, we establish appropriate mathematical model by GAMBIT software, which is imported into FLUENT software to calculate with editing relational procedure by UDF.(1)According to the established model, the evolutive process of molten pool temperature field and fluid field about aluminum/steel dissimilar metal in the CMT welding are calculated in the CMT welding when current is 75 A and welding speed is 400mm/min.The results reflect that the temperature begain to rise with the growth of molten pool, the gradually expansile range of the temperature field and fluid field enlargement of the fluid speed in the procedure of welding. Moreover, the distribution of the front isotherm in heat source is intensive along with relatively large temperature gradient. The distribution of the behind isotherm in heat source is sparse along with relatively diminutive temperature gradient. However, the isotherm distribution of aluminum side has the inconformity with the steel side, which isotherm distribution of aluminum side is intensive and isotherm distribution of steel side is sparse. Fluid spreads into the periphery of molten pool from the the center of heat source. The highest temperature of molten pool can reach to 1229 K and the maximum velocity of molten pool fluid can reach to 0.057m/s in the entire process CMT welding.(2)The paper studied that changing the welding specification paramerers have theinfluence of temperature and fluid field for the CMT welding of dissimilar aluminum/steels.The results reflect that, the distribution shape of temperature and fluid field is similar in the different specification paramerers.The distribution range of the temperature and fluid field increase with increasing current, beside with the maximum temperature and the maximum fluid speed. The maximum temperature when current is 60 A,75A and 90 A is 1164 K, 1229 K and 1316 K respectively, the maximum fluid speed is 0.049m/s,0.057m/s and 0.065m/s respectively. However, the distribution range of the temperature and fluid field decrease with increasing welding speed, beside with the maximum temperature and the maximum fluid speed. The maximum temperature when welding speed is 300mm/min,400mm/min and500mm/min is 1312 K, 1229 K and 1190 K respectively, The maximum fluid speed is 0.07m/s,0.057m/s, and 0.043m/s respectively.(3)The temperature and fluid field of CMT welding are analysised in a pluse cycle Temperature and fluid field are compared in the effects of peak current and basic current.The calculation show that the distribution of temperature and fluid field with the influence of basic current and peak current is same roughly. Moreover, the distance of temperature value is even little, and the fluid speed in the influence of the basic current is lower than which in the influence of peak current.In order to verify the accuracy of the established model, this paper used two temperature measurement methods-thermocouple and infrared temperature, we measured the temperature changing with time in heat-affected zone and weld center respectively. The actual measured value and the results by simulation is similar.