Research On Plasma Arc Welding Forming And Its Control Technique For Marine Ti Alloys With Heavy Sections

A systematic investigation of plasma arc welding technology and its control for Ti75 alloy plate with a thickness of 15.5 mm is performed. For this purpose, some facilities for plasma arc welding process are provided firstly, and secondly the effectsplasma arc welding conditions for keyhole formation are investigated with therelevant control model analyzed and established. Based on ANSYS platform, theinvestigation of the reliability of plasma arc welled joint of thick Ti alloy plates isconducted, which will bring forth new ideas in the welding technology and it's controlsystem for a huge structure of marine Ti alloy plates with a heavy section.1.Through the investigation of the physical properties, heat input and plasma arc welding characteristics for Ti alloys the relation of the welding conditions to Ti alloy plate thickness is found and the control model for heat input is established.2. A systematic investigation of the molten pool behavior of Ti alloy or its shaping of plasma arc weld is performed to establish the relation of the weld shaping to welding conditions by regression analyses.3.By using the above model to investigate the combination characteristics of plasma arc welding conditions, with the physical properties of the Ti alloy, new technical ideas are brought forth in the stability in plasma arc welding power(including plasma torch, protection unit and auto-control program for the three-dimensional welding position and long welled seams), and the configurations and range of plasma arc welding conditions for keyhole in 12.6mm and 15.5mm thick Ti75 alloy plate , respectively are found to make the double side shaping one side plasma arc welding for marine Ti alloy plate with heavy sections cone true, firstly at home, with the NDT inspections(penetrate inspection and X-ray inspection)being up to class I, as per GB4730, and mechanical properties meeting the requirements for technical index, i.e., the coefficient of welding efficiency ≥0.9.4.The welding residual stress will be increased with the increase in the plate thickness, which is the main factor effecting the reliability of marine Ti alloy structures with heavy sections. From the residual stress measurements by a blind hole method, coefficients A and B is determined, which will play an important role in the improvement of the measurement accuracy.The use of ultrasonic impact treatment can make the plasma arc welded joints in...