Titanium and titanium alloy straight seam welded pipe (abbreviated as "titanium welded pipe") is made by welding titanium and titanium alloy coils or wide plates after curling and rolling into a tube shape. The main titanium alloy grades in the United States are Gr.1, Gr.2 and Gr.12, etc., and the main titanium alloy grades in China are TA1, TA2 and TA10, etc. The production process of titanium welded pipe is as follows: titanium strip uncoiling → shearing and welding → loop storage → titanium strip cleaning → tube forming → welding → weld eddy current flaw detection → pre-sizing → online annealing → precision sizing/straightening → eddy current flaw detection → laser diameter measurement → online coding → fixed length cutting → ultrasonic flaw detection → precision sizing/flat head → air tightness test → finished product inspection → packaging and storage.

1. In recent years, the development of the domestic titanium welded pipe industry has been restricted by raw materials and processing technology. The production technology of titanium welded pipes has been in the hands of professional manufacturers in Japan, the United States, France, Russia and other countries for many years. The development of titanium welded pipes in China started late compared with other titanium processed products, and the early development was relatively slow. Although titanium seamless pipes started early in China, their application is limited due to the many processing steps, long production cycle, low efficiency and high cost of titanium seamless pipes. Titanium welded pipes have high production efficiency and yield rate, and the expansion and bending properties of titanium welded pipes are similar to those of seamless pipes. Therefore, the use of titanium welded pipes at home and abroad is increasing year by year, and their application in power station condensers is increasing. In the early development of titanium welded pipes, although China introduced a complete automatic production line for small-diameter titanium welded pipes from abroad, ending the history of China's inability to produce titanium welded pipes, the raw material titanium strip coils for domestic production of titanium welded pipes at that time were completely dependent on imports, and it was impossible to provide strip blanks for thin-walled titanium welded pipes. At the same time, the sales price of foreign titanium strip coils was high, which inhibited the production of domestic titanium welded pipes; in addition, due to the multiple influences of technology introduction and digestion and difficulties in purchasing raw materials, domestic titanium welded pipes have not really had the capacity for mass production, and the domestic titanium welded pipe market was not really formed at that time. In the past decade, China's titanium welded pipe industry has developed rapidly, mainly due to major breakthroughs in the production technology of titanium strip coils, the raw material of titanium welded pipes. The technical performance indicators and quality stability of domestic cold-rolled and hot-rolled titanium strip coils can meet the requirements of titanium welded pipes. In 2007, Hunan Xiangtou Jintian Titanium Metal Co., Ltd., a subsidiary of Hunan Xiangtou Jintian Technology Group, developed China's first wide-width hot-rolled titanium strip coil through the "titanium-steel joint model"; in 2008, it developed cold-rolled titanium strip coils, breaking the monopoly of Japan and the United States in this field, providing raw material support for China's titanium welded pipe industry, and then domestic titanium welded pipes came into being. Xi'an Baoti Metfalinuo Welded Pipe Co., Ltd., a joint venture between Baoti Group Co., Ltd. and many domestic and foreign companies, was officially put into production in 2007. The commissioning of this production line promoted the progress of domestic titanium welded pipe production technology. With the breakthrough of Baoti Group Co., Ltd. in titanium cold-rolled strip technology in 2011, Xi'an Baoti Metfalinuo Welded Pipe Co., Ltd. also achieved mass production of domestic titanium cold-rolled strips. In recent years, with the overall progress of the titanium industry, the expansion of titanium sponge production capacity, and the expansion of titanium processing capacity such as titanium strip coils, the downstream titanium welded pipe industry has also made great progress. Since 2008, many titanium welded pipe production lines have been built in China. The expansion of titanium welded pipe production capacity and the slowdown in the development of the titanium industry have intensified the competition among titanium welded pipe companies. At present, in addition to companies with a complete titanium industry chain such as Xiangtou Jintian Technology Group, other titanium welded pipe companies, as well as many companies with stainless steel pipes and rare metal pipes as their main business are also promoting the progress of the titanium welded pipe industry. Titanium welded pipe companies are paying more and more attention to the development of new technologies and differentiated development. The application areas of titanium welded pipes are constantly expanding. Titanium welded pipes have become the preferred pipe material for many industries to replace stainless steel pipes, copper-nickel alloy pipes, and titanium seamless pipes. After several years of development, domestic titanium welded pipes have broken through a series of key process and technical bottlenecks and have been widely used in power, air conditioning, seawater desalination, water treatment equipment and other fields. In addition, domestic titanium welded pipes have also achieved batch exports. It can be seen that the production process and quality level of domestic titanium welded pipes have been greatly improved.

2. Comprehensive advantages of titanium welded pipes In China, the production technology of low-strength and low-alloyed titanium seamless pipes is relatively mature. In some pipes that need to withstand high pressure and structural forces, thick-walled titanium seamless pipes are generally used. However, due to the influence of factors such as low yield rate and long delivery cycle of titanium seamless pipes, vigorously developing titanium welded pipes has become a trend in the titanium pipe industry. Compared with titanium seamless pipes, the comprehensive advantages of titanium welded pipes are becoming more and more obvious. In countries and regions such as Japan, the United States, and Europe, titanium welded pipes are gradually replacing titanium rolled pipes. 2.1 The mechanical properties of titanium welded pipes and titanium seamless pipes are basically the same. Taking titanium and titanium alloy pipes for heat exchangers and condensers as an example, the national standard is GB/T 3625-2007, and the American standard is ASTMB338. The differences in chemical composition, mechanical properties, and process performance between titanium welded pipes and titanium seamless pipes are not large, or even the same. With the advancement of titanium welded pipe welding and heat treatment technology, domestic thin-walled titanium welded pipes generally adopt single-gun or multi-gun TIG/PAW self-melting welding, and adopt online heat treatment process after welding. By optimizing the welding and annealing process, the microstructures of the parent material, weld and heat-affected zone are basically close, and the welding stress is eliminated at the same time, making the weld structure uniform. By comparison, it is found that the weld composition of titanium welded pipe is basically the same as that of the parent material, and the mechanical properties and corrosion resistance of the weld are the same as those of the parent material. 2.2 The appearance and quality of titanium welded pipe are better than those of titanium seamless pipe. Titanium welded pipe is welded by cold-rolled strip coil, with uniform wall thickness, good concentricity, good finish, and not easy to scale inside the pipe. Especially thin-walled titanium pipe, the production of seamless rolling process cannot meet its technical requirements at all. It is difficult to achieve a wall thickness of less than 1 mm after rolling or drawing process of titanium seamless pipe; while titanium welded pipe can achieve a wall thickness of 0.5 mm and below, saving a lot of materials and costs. At the same time, due to the thin wall thickness of titanium welded pipe, a higher heat transfer coefficient can be obtained, and better heat transfer effect can be achieved. 2.3 The cost and environmental advantages of titanium welded pipes are prominent. The production process of titanium seamless pipes is complicated. Conventionally, three-roll or multi-roll rolling mills and drawing machines are used to roll or draw a certain specification of pipe blanks through multiple passes, and finally reduce the diameter and wall to produce seamless pipes. The production efficiency and yield rate of this process are low. From titanium sponge to pipes, titanium seamless pipes are rolled or drawn, and the material waste is large, the yield rate is only about 50%, and large-scale batch production cannot be achieved, and the production cycle is relatively long. Titanium welded pipes are produced through an automated continuous production line, using titanium strip coils with uniform wall thickness through cold bending, welding, online heat treatment, sizing and straightening, non-destructive testing and air tightness testing. From titanium sponge to welded pipes, the material utilization rate is usually around 80%. If titanium strip coils are used as raw materials, the material utilization rate is above 95%. With the rapid development of the domestic titanium industry and the increasing maturity of welding technology, the production efficiency of titanium welded pipes will also be greatly improved, and the quality stability, consistency and production efficiency will be higher. It can be cut into the required length according to customer requirements, with short delivery time, high material utilization rate, and lower unit cost than seamless pipes. Titanium seamless pipes are usually produced by rolling or drawing. A large amount of rolling oil, drawing oil, etc. will be used in the production process, and the production site is seriously polluted. After the titanium pipe is rolled and drawn, it is necessary to degrease and pickle the grease, dirt, etc. on the inner and outer surfaces of the pipe. The pickling process pollutes the environment greatly. In order to ensure the health of operators and protect the environment, it is necessary to increase protective equipment and protective measures, which will increase capital investment and increase product production costs accordingly. Titanium welded pipes are continuously mass-produced through automated production lines, with stable quality and high production efficiency. In the production process, except for a certain amount of water, electricity and other energy consumption, there is almost no pollution to the environment.

3. Conclusion With the deepening of understanding of titanium welded pipes, the use of titanium welded pipes in the petrochemical industry will be recognized by the market, the scope of use will become wider and wider, and the market share will become larger and larger. Although the investment cost of titanium welded pipes is higher than that of common fluid conveying pipelines, its cost is lower than that of titanium seamless pipes. In terms of the service life and maintenance cycle of titanium welded pipes, the investment cost of titanium welded pipes can be compensated during use. The use of titanium welded pipes in pipeline systems can reduce production costs by reducing the number of regular maintenance, reducing downtime, improving product quality, and increasing pipeline life. In particular, the global titanium industry has not been very prosperous in recent years, and competition has been very fierce. The price of titanium welded pipes has been at a relatively low level. Enterprises in the petrochemical industry use titanium welded pipes with lower initial equipment investment costs.