Study On Narrow Gap Double-cable-wire GMAW Welding Pool Fluid Behaviors

In recent years,the welding work has been greatly increased in the fields of ocean engineering,oil and gas pipelines,pressure vessels,ship manufacturing and so on.The traditional welding methods are difficult to meet the increasing demand for welding production.In the premise of ensuring welding quality,improving the welding production efficiency has become the main research direction of welding workers,this paper studies the narrow gap double cable type GMAW welding technology is developed in this environment.In the study,the narrow gap DW-GMAW of Q235 steel plate was used as the research object.The cable welding wire is used to fill the DW-GMAW welding seam.The GAMBIT software was used to establish the appropriate mathematical model.Based on FLUENT and its secondary development of UDF.Considering the latent heat of phase change,the thermophysical properties of materials with temperature changes and other issues.The temperature field and flow field of the double cable wires GMAW welding pool and narrow gap DW-GMAW were simulated.In order to verify the accuracy of the model,infrared thermography and weld macro metallography were used to validate the simulation results.The simulation results were verified by experiments.The main conclusions are as follows:Based on the established model,the evolution of welding process of the temperature field and flow field of the DW-GMAW welding pool is calculated.The results reflect that the welding pool gradually grows and heats up,range of the temperature field and flow field grows,the fluid speed becomes larger during the welding process.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.Compared with normal GMAW,double cable wires GMAW welding has the advantages of large heating area,long holding time and fast welding speed,which can effectively solve the problem: concentrated heating,overheating,low welding efficiency and so on.The paper studied that changing the welding specification paramerers have the influence on temperature field and flow field of double cable wires GMAW.The results reflect that the distribution range of the temperature field and flow field increase with increasing current,beside with the maximum temperature and the maximum fluid speed.The maximum temperature when current is 400 A,500A and 600 A is 2377 K,2514K and 2726 K respectively,the maximum fluid speed is 9.1cm/s,10.3cm/s and 12.6cm/s respectively.However,the distribution range of the temperature and flow field decrease with increasing welding speed,beside with the maximum temperature and the maximum fluid speed.The maximum temperature when welding speed is 600mm/min,900mm/min and 1200mm/min is 2810 K,2726K and 2569 K respectively,The maximum fluid speed is 13.9cm/s,12.6cm/s and 11.5cm/s respectively.The paper also studied the temperature field and flow field of the weld pool under different front and rear wire current.After comparison,the larger front wire current is conducive to the welding pool.The paper studied that changing the welding specification paramerers have the influence on temperature field and flow field of narrow gap DW-GMAW.The results are similar to the results of DW-GMAW.The distribution range of the temperature and flow field decrease with increasing pitch distance,beside with the maximum temperature and the maximum fluid speed.The maximum temperature when pitch distance is 14 mm,16mm and 18 mm is 3219 K,3134K and 3022 K respectively,and the maximum fluid speed is 14.1cm/s,13.4cm/s and 12.6cm/s respectively.The distribution range of the temperature and flow field decrease with increasing wire spacing,beside with the maximum fluid speed.The maximum temperature increase with wire spacing.The maximum temperature when wire spacing is 10 mm,15mm and 20 mm is 3134 K,3209K and 3279 K respectively,the maximum fluid speed is 13.4cm/s,12.6cm/s and 11.7cm/s respectively.The distribution range of the temperature increase with wire offset,beside with the maximum temperature.The maximum temperature when wire offset is 0mm,2mm and 4mm is 3134 K,2997K and 2904 K.The paper studied that pulsed current has the influence of temperature and flow field for narrow gap DW-GMAW welding pool.Eventually we think a pulse plus an ordinary current is the best combination.The accuracy of the simulation results is verified.The reliability of the model is proved.