Application of titanium alloy welding technology in shipbuilding and requirements for properties of titanium materials

Titanium material has the characteristics of high specific strength, resistance to seawater and Marine atmosphere corrosion, no magnetic, sound transmission, shock resistance and good machinability (plasticity), is a kind of high-quality ship material. For ship materials, welding technology is an important processing means of structural manufacturing. The adaptability of various Marine titanium and titanium alloys to welding processing, welding performance is directly related to their application in ship structure.

There are many varieties and grades of titanium materials, and their related performance requirements are different for different fields of application. The main application functions of Marine titanium alloy are excellent corrosion resistance to seawater and Marine atmosphere, high specific strength, high toughness and excellent processing performance. Due to the wide range of applications of titanium in the field of ships, such as ship structures, propulsion systems, power systems, electronic information systems, auxiliary systems to special devices, etc., titanium alloy materials with various properties and specifications are needed.

Marine titanium and titanium alloy welding, usually follow the principle of equal strength, and obtain the best strength and plasticity, toughness. Therefore, when selecting welding materials:
① Generally use homogeneous welding materials;
② In order to improve the plasticity of the joint, the welding material with a slightly lower alloying degree than the base material can be used;
③ In order to improve the weld metal plasticity, the content of gap elements in the welding wire should be lower than that in the base metal. According to the results of many years of research on Marine titanium alloy welding application and the regression analysis of test data, it can be seen that in order to obtain the equal strength of weld metal and base metal, the welding wire alloy composition is generally required to be 1 Al equivalent lower than the base metal.
In order to control the content of impurity elements in the weld metal at a low level, the content of original impurity elements in the welding wire should be strictly controlled. The reliability of Marine titanium alloy welded joint is largely related to the structural shape of the joint. For the stress relief heat treatment of Marine titanium alloy welded structure, the heat treatment process should be determined according to the characteristics of different alloys, in order to obtain the best heat treatment effect.

Most Marine titanium alloys have excellent weldability. In the process of alloy application, according to the characteristics of various alloys and the working conditions of the structure, the correct design of the joint form, reasonable selection of welding materials, the development of reasonable welding process, the provision of good welding high temperature zone, reliable gas protection and the correct use of stress relief measures are the key to ensure the acquisition of Marine titanium alloy welded joints with excellent comprehensive performance.