Titanium is widely used in the marine industry due to its good corrosion resistance. 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 material 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. There is a seawater cooler manufactured by our company for China National Offshore Oil Corporation. The equipment parameters are as follows: heat exchange area 30m2, diameter φ400mm. Pipeline medium: seawater; design pressure: 1.3Mpa; design temperature 35℃; main body material: Gr1. Shell side medium: natural gas; design pressure 1.0Mpa; design temperature 175℃; main body material: Q345R. The tube section is made of Gr1 with a thickness of 10mm; tube sheet material: Gr1, with a thickness of 45mm; heat exchange tube specifications: φ19×2, material: Gr1. The heat exchange tube and the tube sheet are connected by strength welding.
Titanium and titanium alloys are widely used in aerospace, petrochemical, shipbuilding, and other parts because of their low density, high strength, and excellent heat and corrosion resistance. Titanium is a very active metal. It has a strong affinity with carbon, hydrogen, oxygen, nitrogen, etc. at high temperatures. It generates brittle compounds such as titanium hydride, titanium carbide, titanium oxide, and titanium nitride in the weld, making the welded plastic Decrease resilience. Titanium has a low thermal conductivity and a high melting point. It is prone to heat concentration during welding. If the high-temperature residence time is too long, it will cause the weld grain to be coarse and reduce the overall performance of the welded joint. At present, high-performance aircraft and tanks are using titanium alloy parts, and the scope of use of titanium alloy parts in the petrochemical industry is gradually expanding. The application of titanium alloys in aircraft and their engines and petrochemical parts inevitably requires the use of welding means to connect, which is of great significance to the expansion of the application range of titanium alloys. With the rapid development of science, technology, and the economy, more and more extremely strict requirements are put forward on steel materials. Light energy-saving automobiles, high-speed railways, heavy-duty bridges, oil and gas pipelines, construction machinery, large ships, and other fields require a lot of Steel with good performance, long service life, and low price. This problem has attracted the attention of governments and experts in the field of steel materials. By refining the structure of steel, it can improve the cleanliness of the steel, improve the uniformity of the steel, and increase its strength and service life. Because of its excellent performance and relatively low cost, micro-alloyed steel has developed rapidly in many fields. With the expansion of the use of steel in various fields, there are more and more occasions for welding forming technology. Research shows that the use of Ti, Nb, V, and other elements in low-alloy high-strength steel for microalloying, TiN, NbN, VN, etc. in steel The particles inhibit the growth of austenite grains, which can effectively increase the strength of steel welded with large heat input, and improve the toughness of the coarse-grained heat-affected zone of welding. Through proper post-weld heat treatment, Ti can mainly appear in the weld in the form of TiC/N. The TiC/N face-centered cubic structure has coherence with the face-centered cubic and body-centered cubic matrix of steel, which can be used under certain conditions. It can be precipitated after being dissolved, and the strength and toughness of the weld metal can be greatly improved through the dispersed precipitation of carbon and nitride particles (with a size of less than 5nm) and the solid solution refined grain precipitation strengthening of Ti. Therefore, under the conditions of post-weld heat treatment, the existence of titanium in the weld metal and its influence on weld metal structure and properties have great application prospects.
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