Research On Welding Technical Of Titanium Unequal Thick-walled Rectangular Pipe By FEM

Titanium rectangular tubes not only have excellent energy absorbing capability, but also are light in weight and corrosion-resistant. Based on the Theory-Experiment-Numerical Simulation–Production"model, this paper conducts some researches on the welding process of TC4 unequal thick-walled rectangular tubes.Firstly, the weldability of rectangular tube structure is analyzed. The single-side TIG welding process of TC4 thick plank is designed based on welding standards. The process is applied to experiments on two kinds of thickness plates which are the samilar thickness of rectangular tubes. The corresponding welded joints have both ideal appearance and mechanical properties. At the same time, a real-time data acquisition system for welding thermal cycle is presented and thermal cycling of welding heat-affected zone is obtained in experimental process.The titanium alloy thick plate single-side simulating model is built based on experiment. Corresponding Simulation has been carried out for welding temperature field of two kinds of titanium thick plates. The method of killing or activating elements is used to depict wire filling welding. Parallel computation is used to improve computation efficiency. The features of titanium alloy weld pool with large length-width ratio agrees with low thermal conductivity of titanium. Comparing the border of wielding pool and thermal cycling it shows that calculated values have a good agreement with experimental values. The validity of Finite Element Modeling is verified. The digging action of the double-ellipsoid thermal source in the direction of thickness copies well with the feature of welding thick plate by TIG welding. Key points for multiplayer welding simulation are propounded. Based on practical situation of the production in the enterprise, the simulating model for typical welding sequence and process scheme is simplified and refined for the TC4 unequal thick-walled rectangular tube. The temperature field and stress-strain field for welding procedure are simulated and analyzed by FEM. As all-around weld, The tube shrinkage and hogging at the corner, as well as local stress concentration areas emerge. It is believed that the rectangular tube should must be tacked together before welding. Without regard to the welding difficulty, the scheme of even distance among tack welding spot is believed to be superior. The best welding sequence is start-up at the either side of neutro-axis. It's a method for decreasing the welding deformations with positioning core, but residual stresses will increase because of the restrain.Finally, taking the conclusion derived from the experiment and FEM simulation, some key points for quality control are proposed, and also provide theoretical way for formulating the welding technology of rectangular tube and technological parameter optimization. Consequently, the simulation for welding process can be applied to practical technical practice.