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

Titanium materials possess characteristics such as high specific strength, resistance to seawater and marine atmospheric corrosion, non-magnetism, sound transmission, resistance to impact and vibration, and good machinability (plasticity). They are a high-quality material for ships. For ship materials, welding technology is an important processing method for their structural manufacturing. The adaptability of various marine titanium and titanium alloys to welding processing, as well as the quality of their welding performance, directly affect their application in ship structures.

There are numerous varieties and grades of titanium materials. Depending on the different application fields, the performance requirements for them also vary. The main application functions of marine titanium alloys are excellent resistance to seawater and marine atmospheric corrosion, high specific strength, high toughness, and excellent processing performance. Due to the wide application range of titanium materials in the ship field, such as ship structures, propulsion systems, power systems, electronic information systems, auxiliary systems, and special devices, various performance and grade specifications of titanium alloy materials 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 achieved. Therefore, when selecting welding materials:
① Generally, homogeneous welding materials are selected;
② To improve the plasticity of the joint, welding materials with a slightly lower alloying degree than the base material can be used;
③ 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 material. Based on the regression analysis of research results and test data on the application of marine titanium alloy welding, it can be known that to achieve equal strength between the weld metal and the base material, generally, the alloy composition of the welding wire should be 1 Al equivalent lower than that of the base material.

To control the impurity element content in the weld metal after welding at a low level, the original impurity element content in the welding wire should be strictly controlled. The reliability of the welding joint of marine titanium alloys is largely related to the structural shape of the joint. For the stress-relieving heat treatment of marine titanium alloy welded structures, the heat treatment process system should be determined according to the characteristics of different alloys to achieve the best heat treatment effect.

Most marine titanium alloys have excellent welding processing performance. During the application of alloys, according to the characteristics of various alloys and the operating conditions of the structure, correctly design the joint form, reasonably select welding materials, formulate reasonable welding processes, provide good and reliable gas protection in the welding hot zone, and correctly adopt stress-relieving measures are the key to ensuring the acquisition of excellent marine titanium alloy welded joints with comprehensive performance.