Titanium is widely used in the marine industry because of its good corrosion resistance. Most marine titanium alloys have excellent welding processability. In the application process of alloys, according to the characteristics of various alloys, the working conditions of the structure, the correct design of the joint form, the reasonable selection of welding materials, and the formulation of reasonable welding processes, provide good, reliable gas protection in welding high temperature areas and correct The use of stress relief measures is the key to ensuring a marine titanium alloy welded joint with excellent overall performance. There is a seawater cooler manufactured by China National Offshore Oil Corporation. The equipment parameters are as follows: heat exchange area 30m2, diameter φ400mm. Pipe media: sea water; design pressure: 1. 3Mpa; design temperature 35 ℃; main material: TA2. Shell side medium: natural gas; design pressure 1.0 Mpa; design temperature 175 ℃; main material: Q345R. Among them, the material of the tube side barrel section is TA2, the thickness is 10mm; the material of the tube sheet: TA2, the thickness: 45mm; the specification of the heat exchange tube is: φ19 × 2, the material: TA2. The heat exchange tube and the tube plate are connected by strength welding.
Titanium and titanium alloys are widely used in aerospace, petrochemical, shipbuilding, etc. due to 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, and generates brittle compounds such as titanium hydride, titanium carbide, titanium oxide, and titanium nitride in the weld, which makes the weld plastic Toughness decreases. Titanium has a small thermal conductivity, a high melting point, and heat concentration is prone to occur during welding. If the residence time at high temperature is too long, the grain of the weld will be thick, which will reduce the overall performance of the welded joint. At present, high-performance aircraft and tanks are using titanium alloy parts, and the use of titanium alloy parts in the petrochemical sector is also gradually expanding. The application of titanium alloys in aircrafts, engines and petrochemicals parts inevitably requires the use of welding methods for connection, which is of great significance for expanding the application range of titanium alloys. With the rapid development of science, technology and economy, more and more strict requirements are put forward on steel materials. Light energy-saving automobiles, high-speed railways, heavy-load bridges, oil and gas pipelines, engineering 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 iron and steel materials industry. By refining the organization of steel, the cleanliness of the steel, the uniformity of the steel, the strength and the service life of the steel are improved. Micro-alloyed steel has developed rapidly in many fields because of its excellent performance and relatively low cost. With the expanded use of steel in various fields, the number of occasions where welding and forming processes are required has increased. Studies have shown that low alloy high strength steels use Ti, Nb, V and other elements for microalloying, and TiN, NbN, VN, etc. The particles inhibit the growth of austenite grains, which can effectively improve the strength of the steel using the large heat input welding method and improve the toughness of the weld heat affected zone of coarse grains. Through proper post-weld heat treatment, Ti can appear mainly in the form of TiC / N in the weld, TiC / N face-centered cubic structure and steel face-centered cubic, body-centered cubic matrix have coherence, under certain conditions can be It can be precipitated by dissolution, and can be dispersed and precipitated by carbon and nitride particles (size less than 5nm) and Ti solid solution refinement grain precipitation strengthening, greatly improving the strength and toughness of the weld metal. Therefore, under the condition of post-weld heat treatment, the existence form of titanium in the weld metal and its influence on the weld metal structure and performance have great application prospects.
