| Hot-wire TIG welding process is a high-quality, high-efficient, energy efficiency one developed from the traditional TIG welding process. Its principle is that before the wire is feed into the welding pool the wire is heated to a certain pre-heated temperature in order to achieve a high-speed and high-efficient welding process. In this paper, the experimental platform used for the hot-wire TIG welding process experiment has been established. In order to verify the results from numerical simulation and mathematical models, some process experiments have been made based on this platform.Firstly based on the law of the conservation of energy, the mathematical model considering the impact of resistance heat on the pre-heated temperature of the tip of wire was developed. The impact of several factors such as hot-wire current, wire-feeding speed and wire extension on the pre-heated temperature of the tip of wire has been analyzed. The conclusion has been made: the pre-heated temperature of the tip of wire is gradually increasing with the increasing of hot-wire current, the decreasing of wire-feeding speed and the increasing of wire extension. After the length of wire extension is ascertained, the maximum permissible hot-wire current and the minimum permissible wire-feeding speed have been made sure. For the ultra-high speed hot-wire TIG welding process, the pre-heated temperature of the tip of wire must get the melting point of materials of wire.At this time, the mathematical expression related to wire feeding speed was been deducted. The conclusion is made: the wire feeding speed is increasing with the increasing of hot-wire current and the increasing of wire extension. Secondly, based on the law of energy conservation, the mathematical model of the hot-wire temperature distribution considering the effect of heat loss was developed. The accuracy of the mathematical model was validated by comparing the result of calculating from the mathematical model with the experimental results from others' paper, the impact of wire diameter, hot-wire current, wire feeding speed, wire extension on temperature distribution of hot-wire was elaborately discussed. The results show that the mathematical model has the high accuracy in order that it can be used to effectively analysis the heating process of wire and satisfy the need of controlling the welding quality. The temperature of every point on the wire extension decreases with the increasing of the diameter of wire and wire feeding speed. However, the bigger hot-wire current is, the higher the temperature is. The bigger the wire extension is, the higher the temperature of the position on the wire having the same distance away from the wire-feeding point is.Eventually, according to the superposition principle of heat resource, a calculating formula of density distribution of welding heat source for hot-wire TIG welding process was derived. At the same time, the proper finite element model was established. The motion of welding heat resource is realized by the means of programming with APDL of ANSYS FEA software. Then the transient change of temperature field of bead-on-plate welding for hot-wire TIG welding process has been simulated in hot-wire TIG welding fully considering the boundary conditions of convection,radiation,fluid flow and latent heat of phase change. Finally, comparing the simulated results to experimental ones to validate the dependability of the above-mentioned mode1.The temperature transient change of different nodes on the centerline and longitudinal cross section of welding bead with the welding time was achieved. Numerical simulation of the temperature field distribution for hot-wire TIG welding process not only provides the premise of analyzing welding metallurgy, welding stress and strain and others, but also offer some key data and important theoretical evidence to the process optimization and intelligent control of welding process. |
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