The application of titanium alloy welding technology in shipbuilding and the requirements for the performance of titanium materials

Titanium material has the characteristics of high specific strength, corrosion resistance of sea water and ocean atmosphere, non-magnetic, sound permeability, shock resistance and good workability (plasticity), etc. It is a high-quality ship material. For marine materials, welding technology is an important processing method for structural manufacturing. The adaptability of various marine titanium and titanium alloys to welding and the welding performance are directly related to their application in ship structures.

There are many varieties and grades of titanium materials, and their related performance requirements are also different for different fields of application. The main application functions of marine titanium alloys are excellent corrosion resistance to sea water and ocean atmosphere, high specific strength, high toughness and excellent processing performance. Because titanium has a wide range of applications in the marine field, such as ship structures, propulsion systems, power systems, electronic information systems, auxiliary systems, and special devices, titanium alloy materials with various properties and specifications are required.

When welding marine titanium and titanium alloys, the principle of equal strength is usually followed, and the best combination of strength, plasticity and toughness is obtained. Therefore, when selecting welding materials:

• ① Generally use homogeneous welding materials;
• ②In order to improve the plasticity of the joint, welding consumables with a slightly lower degree of alloying than the base metal can be used;
• ③In order to improve the plasticity of the weld metal, the content of interstitial elements in the welding wire should be lower than that in the base metal. According to the regression analysis of the welding application research results and test data of titanium alloys for ships for many years, it can be known that in order to obtain the equal strength of the weld metal and the base metal, the composition of the welding wire alloy 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 after welding, the content of the original impurity elements in the welding wire should be strictly controlled. The reliability of marine titanium alloy welded joints is largely related to the structural shape of the joints. For the stress relief heat treatment of marine titanium alloy welded structures, the heat treatment process system should be determined according to the characteristics of different alloys to obtain the best heat treatment effect.

Most marine titanium alloys have excellent welding performance. In the alloy application process, according to the characteristics of various alloys and the working conditions of the structure, the joint form should be correctly designed, the welding materials should be selected reasonably, and the reasonable welding process should be formulated to provide good and reliable gas protection in the welding high temperature zone. The use of stress relief measures is the key to ensuring that marine titanium alloy welded joints with excellent comprehensive performance are obtained.