1 Development of domestic titanium welded pipe industry in recent years
Due to the constraints of 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. Compared with other titanium processing products, the development of titanium welded pipes in China started relatively late, and the early development was relatively slow. Although titanium seamless pipe started earlier in China, its application is limited due to many processing procedures, long production cycle, low efficiency and high cost, while titanium welded pipe has high production efficiency and yield, and titanium welded pipe The performance of expanding and bending pipes is similar to that of seamless pipes, so the amount of titanium welded pipes at home and abroad is increasing year by year, and the application in power station condensers is increasing.
In the early stage of the development of titanium welded pipes, although China introduced a complete automatic production line of small-diameter titanium welded pipes from abroad, which ended the history of China's inability to produce titanium welded pipes, due to the fact that at that time, the raw material for domestic production of titanium welded pipes, titanium coils, were completely dependent on imports and could not be provided. The strip billets for thin-walled titanium welded pipes and the high sales price of foreign titanium coils have inhibited the production of domestic titanium welded pipes; in addition, due to the multiple influences of technology introduction and digestion and difficulty in purchasing raw materials, domestic titanium welded pipes have not really been available. Mass production capacity, the domestic titanium welded pipe market was not really formed at that time.
In the past ten years, the rapid development of China's titanium welded pipe industry is mainly due to the major breakthroughs in the production technology of titanium coils, the raw material of titanium welded pipes, and the technical performance indicators and quality stability of domestic cold and hot rolled titanium coils. It can meet the requirements of titanium welded pipes. 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 in 2007 through the "Titanium-steel joint model"; in 2008, it developed a cold-rolled titanium strip. It broke the monopoly of Japan and the United States in this field and provided raw material support for China's titanium welded pipe industry, and then domestic titanium welded pipes came into being.
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 coils, the downstream titanium welded pipe industry has also made great progress. Since 2008, a number of titanium welded pipes have been built in China. production line. The expansion of titanium welded pipe production capacity and the slowdown in the development of the titanium industry have intensified competition among titanium welded pipe enterprises. At present, titanium welded pipe enterprises and many enterprises mainly engaged in stainless steel pipes and rare metal pipes are also promoting the progress of the titanium welded pipe industry. Titanium welded pipe enterprises pay more and more attention to the development of new technologies and the development of differentiation.
The application fields of titanium welded pipes are constantly expanding. Titanium welded pipe has become the first choice for many industries to replace stainless steel pipe, copper-nickel alloy pipe and titanium seamless pipe. 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 electric power, air conditioning, seawater desalination, water treatment equipment and other fields. In addition, domestic titanium welded pipes have also been exported in batches. 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, low-alloyed titanium seamless pipes is relatively mature. In some pipes that need to withstand high pressure and structural stress, thick-walled titanium seamless pipes are generally used. However, due to the influence of factors such as low yield of titanium seamless pipes and long delivery cycle, 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 Japan, the United States, Europe and other countries and regions, titanium welded pipes are gradually replacing titanium rolled pipes.
2.1 The mechanical properties of titanium welded pipe and titanium seamless pipe are basically the same
Taking titanium and titanium alloy tubes for heat exchangers and condensers as an example, the national standard is GB/T 3625-2007, and the American standard is ASTMB338. Titanium welded tubes and titanium seamless tubes are different in terms of chemical composition, mechanical properties and process properties. Not much, even the same. With the progress of welding and heat treatment technology of titanium welded pipes, domestic thin-walled titanium welded pipes generally adopt single-gun or multi-gun TIG/PAW self-fusion welding, and online heat treatment process is adopted after welding. , The microstructure of the heat-affected zone is basically close, and the welding stress is eliminated at the same time, so that the weld structure is uniform. By comparison, it is found that the composition of the weld seam of the titanium welded pipe is basically the same as that of the base metal, and the mechanical properties and corrosion resistance of the weld seam are the same as those of the base metal.
2.2 The appearance and quality of titanium welded pipes are better than those of titanium seamless pipes
Titanium welded pipe is welded by cold-rolled coil, with uniform wall thickness, good concentricity, good finish, and it is not easy to scale in the pipe. In particular, thin-walled titanium tubes cannot meet their technical requirements at all by seamless rolling. It is difficult to achieve a wall thickness of less than 1 mm for titanium seamless pipes after rolling or drawing processes; while titanium welded pipes can achieve wall thicknesses of 0.5 mm or less, saving a lot of materials and costs. At the same time, due to the thin wall thickness of the titanium welded pipe, a higher heat transfer coefficient can be obtained and a better heat transfer effect can be achieved.
2.3 The cost and environmental advantages of titanium welded pipes are outstanding
The production process of titanium seamless pipe is complicated. Conventionally, three-roll or multi-roll mills and drawing machines are used to roll or draw a certain specification of tube blanks for multiple passes, and finally produce seamless pipes after reducing diameter and wall. The production efficiency and yield of this 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 large-scale mass production cannot be achieved, and the production cycle is relatively long.
The titanium welded pipe is produced by an automated continuous production line, using titanium coils with uniform wall thickness through cold bending, welding, online heat treatment, sizing and straightening, non-destructive testing and air tightness testing. From sponge titanium to welded pipes, the material utilization rate is usually about 80%. If the titanium coil is used as the raw material, the material utilization rate is above 95%. With the rapid development of the domestic titanium industry and the maturation 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, and can be cut to the required length according to customer requirements. , The delivery time is short, the material utilization rate is high, and the unit cost will be lower than that of seamless pipes.
Titanium seamless pipes are usually produced by processes such as rolling or drawing. A large amount of rolling oil, drawing oil, etc. will be used in the production process, and the production site will be seriously polluted. After the titanium tube is rolled and drawn, it is necessary to degrease and pickle the grease and dirt on the inner and outer surfaces of the tube, and the pickling process causes great environmental pollution. In order to ensure the health of operators and protect the environment, it is necessary to increase protective equipment and protective measures, thus increasing capital investment and correspondingly increasing product production costs. Titanium welded pipes are continuously produced in large quantities through automated production lines, with stable quality and high production efficiency. Except for a certain amount of energy consumption such as water and electricity, there is almost no pollution to the environment during the production process.
3 Conclusion
With the deepening of the 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 also increase. Although the investment cost of titanium welded pipe is higher than that of common fluid conveying pipes, its cost is lower than that of titanium seamless pipe, and 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 pipes in piping systems can reduce production costs by reducing the number of scheduled maintenance, reducing downtime, improving product quality, and increasing pipe life. Especially in recent years, the global titanium industry is not very prosperous, and the competition is very fierce. The price of titanium welded pipes has been at a low level, and enterprises in the petrochemical industry choose titanium welded pipes with lower investment costs in the early stage of equipment.
Although China's titanium welded pipe industry has achieved rapid development, the production process and quality level have been greatly improved, and titanium welded pipes have been widely used in electric power, seawater desalination, water treatment equipment, air conditioning equipment and other industries, but in the petrochemical industry, the use of titanium welded pipes It is still being promoted.
