Titanium and titanium alloy welded pipe (referred to as "titanium welded pipe") is made of titanium and titanium alloy rolled strip or wide sheet rolled into tube shape after welding. American titanium alloy brands mainly include Gr.1, Gr.2 and Gr.2, etc., while domestic titanium alloy brands mainly include TA1, TA2 and TA10.
The production process of titanium welded pipe is as follows: titanium strip unwinding → shear welding → lofted material storage → titanium strip cleaning → pipe forming → welding → eddy current testing of weld → predetermined diameter → online annealing → fine sizing/straightening → eddy current testing → laser sizing → online coding → fixed size cutting → ultrasonic testing → fine sizing/flat head → air tightness test → finished product inspection → packing and storage.
1. Development of domestic titanium welded pipe industry in recent years
Titanium Tubing production technology has been in the hands of specialists in Japan, the U.S., France, and Russia for many years due to the constraints of raw materials and processing technology. Compared with other titanium products, the development of titanium welded pipe in China started relatively late, and the early development is relatively slow. Although the titanium seamless tube started earlier in China, its application is limited due to the many processing procedures, long production cycle, low efficiency and high cost of the titanium seamless tube. The production efficiency and yield of the titanium welded pipe are high, and the performance of the titanium welded pipe such as tube expansion and bending is similar to that of the seamless pipe. Therefore, the amount of titanium welded pipe at home and abroad is increasing year by year, and its application in the power station condenser is increasing day by day.
In the early stage of the development of titanium welded pipes, although China introduced a complete small-diameter automatic production line for titanium welded pipes from abroad, which ended the history of China's inability to produce titanium welded pipes, at that time, the raw materials for titanium welded pipes in China were completely dependent on imports, and the blanks for thin-wall titanium welded pipes could not be provided, and the selling price of titanium welded pipes in foreign countries was relatively high. Therefore, the domestic production of titanium welded pipe is inhibited. In addition, due to the multiple impacts of technology introduction and digestion and raw material procurement difficulties, domestic titanium welded pipe has not been really capable of mass production, at that time the domestic titanium welded pipe market has not really formed.
In the past ten years, the rapid development of China's titanium welded pipe industry is mainly due to the major breakthrough made in the production technology of titanium strip coil, the raw material of titanium welded pipe. The technical performance index and quality stability of domestic cold and hot rolled titanium strip coil can meet the requirements of titanium welded pipe. In 2007, Xiangtou Jintian Titanium Metal Co., LTD., a subsidiary of Hunan Xiangtou Jintian Technology Group, developed China's first wide-width hot rolled titanium coil through the "titanium steel joint mode". In 2008, he developed cold-rolled titanium coil, which broke the monopoly of Japan and the United States in this field and provided raw material support for China's titanium welded pipe industry. Subsequently, domestic titanium welded pipe also came into being.
Xi 'an Baoti MeteFalino Welded Pipe Co., LTD., a joint venture between Baoti Group Co., Ltd. and many domestic and foreign enterprises, was put into operation in 2007. The production line has promoted the progress of domestic titanium welded pipe production technology. With the breakthrough of Baoti Group Co., Ltd. in the technology of titanium cold rolled strip in 2011, Xi 'an Baoti Mete Farino Welded Pipe Co., Ltd. also realized the mass production of domestic titanium cold rolled strip.
In recent years, with the overall progress of the titanium industry, the expansion of titanium sponge titanium production capacity, the expansion of titanium strip coil and other titanium processing capacity, the downstream titanium welded pipe industry has also achieved considerable development. Since 2008, a number of titanium welded pipe production lines have been built in China. The expansion of titanium welded pipe production capacity and the slowdown of the development of titanium industry have intensified the competition among titanium welded pipe enterprises. At present, in addition to Xiangtou Jintian Technology Group and other enterprises with a complete titanium industry chain, other titanium welded pipe enterprises, as well as many enterprises with stainless steel pipe and rare metal pipe as the main business are also promoting the progress of titanium welded pipe industry. Titanium welded pipe enterprises pay more and more attention to the development of new technology and differentiated development.
The application field of titanium welded pipe is expanding continuously. Titanium welded pipe has become the preferred pipe to replace stainless steel pipe, copper-nickel alloy pipe and titanium seamless pipe in many industries. After several years of development, domestic titanium welded pipe has broken through a series of key processes and technical bottlenecks, and has been widely used in electric power, air conditioning, seawater desalination, water treatment equipment and other fields. In addition, domestic titanium welded pipe has also achieved batch export. It can be seen that the production process and quality level of domestic titanium welded pipe have been greatly improved.
2. Comprehensive advantages of titanium welded pipe
In China, the production technology of low-strength and low-alloying titanium seamless pipe is relatively mature. In some pipes that need to withstand high pressure and structural stress, thick-wall titanium seamless pipe is generally used. However, due to the influence of factors such as low yield and long delivery cycle of titanium seamless pipe, it has become a trend to develop titanium welded pipe vigorously. Compared with titanium seamless pipe, the comprehensive advantage of titanium welded pipe is more and more obvious, in Japan, the United States, Europe and other countries and regions, titanium welded pipe is gradually replacing titanium rolled pipe.
2.1 Mechanical properties of titanium welded pipe and titanium seamless pipe are basically the same
Taking titanium and titanium alloy tubes used in heat exchanger and condenser as an example, the national standard is GB/T 3625-2007, and the American standard is ASTMB338. There is little or even the same difference between titanium welded tubes and titanium seamless tubes in terms of chemical composition, mechanical properties and technological properties. With the progress of welding and heat treatment technology of titanium welded pipe, domestic thin-wall titanium welded pipe generally adopts single gun or multi-gun TIG/PAW self-fusion welding, and adopts online heat treatment process after welding. By optimizing welding and annealing process, the microstructure of base metal, weld and heat affected zone is basically close, and the welding stress is eliminated, so that the weld microstructure is homogenized. By comparison, it is found that the weld composition of the titanium welded pipe is basically the same as that of the base material, and the mechanical properties and corrosion resistance of the weld are the same as that of the base material.
2.2 The appearance and quality of titanium welded pipe is better than that of titanium seamless pipe
Titanium welded pipe is cold rolled with coil welding, uniform wall thickness, good concentricity, good finish, not easy to scale inside. In particular, thin-walled titanium tube cannot meet its technical requirements by seamless rolling process. After rolling or drawing process, it is difficult to achieve a wall thickness of less than 1 mm; The wall thickness of titanium welded pipe can be 0.5mm or less, saving a lot of materials and costs. At the same time, because of the thin wall thickness of titanium welded pipe, higher heat transfer coefficient and better heat transfer effect can be obtained.
2.3 The cost and environmental protection advantages of titanium welded pipe are prominent
The production process of titanium seamless tube is complex, the conventional use of three-roll or multi-roll rolling mill, drawing machine to a certain specification of tube blank through multiple rolling or drawing, and finally through reducing the diameter and wall to produce seamless tube. The production efficiency and yield rate of the process are low. Titanium seamless pipe from sponge titanium to pipe, through rolling or drawing, material waste is large, the yield is only about 50%, and can not achieve mass production, production cycle is relatively long.
Titanium welded pipe is produced by automatic continuous production line, using titanium tape coil with uniform wall thickness through cold forming, welding, online heat treatment, sizing straightening, non-destructive testing and air tightness testing and other processes. From sponge titanium to welded pipe, the material utilization rate is usually about 80%. If the titanium tape coil is used as the raw material, the material utilization rate is above 95%. With the rapid development of domestic titanium industry and increasingly mature welding technology, the production efficiency of titanium welded pipe will be greatly improved, quality stability, consistency and production efficiency will be higher, can be cut into the required length according to customer requirements, delivery time is short, high material utilization rate, unit cost will be lower than seamless pipe.
Titanium seamless tube is usually produced by rolling or drawing process. The production process will use a lot of rolling oil, drawing oil and so on, the production site pollution is serious. After titanium pipe rolling and drawing processing, it is necessary to degrease and pickling the oil and dirt on the inside and outside surface of the pipe. The pickling process will pollute the environment greatly. In order to ensure the health of the operators and protect the environment, it is necessary to increase the protective equipment and protective measures, thus increasing the capital investment, product production costs are also increased. Titanium welded pipe is continuous mass production through automatic production line, stable quality, high production efficiency, in the production process except for a certain amount of water, electricity and other energy consumption, almost no pollution to the environment.
With the deepening understanding of titanium welded pipe, the use of titanium welded pipe in the petrochemical industry will be recognized by the market, the scope of use will be more and more wide, and the market share will be more and more large. Although the investment cost of titanium welded pipe is higher than that of common fluid conveying pipe, it is lower than that of titanium seamless pipe. Moreover, from the analysis of the service life and maintenance cycle of titanium welded pipe, the investment cost of titanium welded pipe can be compensated in use. The use of titanium welded pipe in pipeline system can reduce the number of regular maintenance, reduce production time and improve product quality. Improve pipe life to reduce production costs. Especially in recent years, the global titanium industry is not very booming and the competition is very fierce. The price of titanium welded pipe has been at a low level, and the enterprises in the petrochemical industry choose titanium welded pipe with lower early equipment input cost.