Titanium and titanium alloy longitudinally welded pipes (referred to as "titanium welded pipes") are made by crimping and rolling titanium and titanium alloy coils or wide plates into a tube shape and then welding. American titanium alloy grades mainly include Gr.1, Gr.2 and Gr.12, and domestic titanium alloy grades mainly include TA1, TA2 and TA10.
The production process of titanium welded pipe is as follows: titanium strip uncoiling → shearing butt welding → looper storage → titanium strip cleaning → tube forming → welding → welding seam eddy current inspection → predetermined diameter → online annealing → fine sizing/straightening → Eddy current inspection→laser diameter measurement→online coding→fixed-length cutting→ultrasonic inspection→precisely fixed length/flat head→air tightness test→finished product inspection→package and storage.
1. The development of China's 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 processed products, the development of titanium welded pipes in China started late, and the early development is relatively slow. Although titanium seamless pipe started early in China, its application is limited due to the many processing procedures, long production cycle, low efficiency and high cost of titanium seamless pipe. The production efficiency and yield rate of titanium welded pipe are high, and titanium welded pipe The performance of expanding tube and bending is similar to seamless tube, so the amount of titanium welded tube at home and abroad is increasing year by year, and the application in condenser of power station is increasing.
In the early stage of the development of titanium welded pipe, although China introduced a complete automatic production line for small diameter titanium welded pipes from abroad, which ended China’s history of not being able to produce titanium welded pipes, at that time, the raw material for titanium welded pipe production in China was completely dependent on imports and could not be provided. The strip blanks 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 effects of technology introduction and digestion and difficulty in raw material procurement, 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 made in the production technology of titanium welded pipe raw materials—titanium coils. The technical performance indicators and quality stability of domestic cold and hot rolled titanium coils Meet the requirements of titanium welded pipe. HNXT Titanium Metal Co., Ltd., a subsidiary of HNXT Technology Group, developed China’s first wide-width hot-rolled titanium coil in 2007 through the “titanium-steel joint model”; in 2008, it developed cold-rolled titanium coil, breaking the Japanese and American standards. The monopoly in this field provided raw material support for China's titanium welded pipe industry, and then domestic titanium welded pipes also emerged.
XABT Titanium Welded Pipe Co., Ltd., a joint venture between BJBT Group Co., Ltd. and many domestic and foreign companies, was officially put into operation in 2007. The commissioning of this production line promoted the progress of domestic titanium welded pipe production technology. With the breakthrough of BJBT Group Co., Ltd. in titanium cold-rolled strip technology in 2011, XABT Titanium 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 sponge titanium production capacity, and the expansion of titanium processing capacity such as titanium strip coils, the downstream titanium welded pipe industry has also made considerable development. Since 2008, many titanium welded pipes have been built in China. production line. The expansion of titanium welded pipe production capacity and the slowing down of the development of the titanium industry have intensified competition among titanium welded pipe companies. At present, in addition to enterprises with a complete titanium industry chain such as HNXT Technology Group, other titanium welded pipe enterprises, as well as many enterprises with stainless steel pipes and rare metal pipes as their main industries, 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 the development of differentiation.
The application areas of titanium welded pipes are constantly expanding. Titanium welded pipes have become the first choice for replacing stainless steel pipes, copper-nickel alloy pipes and titanium seamless pipes in many industries. After several years of development, titanium welded pipes produced in China have broken through a series of key processes 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 technology and quality level of domestic titanium welded pipes have been greatly improved.
2. Comprehensive advantages of titanium welded pipe
In China, the production technology of low-strength, low-alloy titanium seamless pipes is relatively mature, and thick-walled titanium seamless pipes are generally used in some pipes that require high pressure resistance and structural stress. However, due to the low yield of titanium seamless pipes and the long delivery period, the development of 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
Take 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 ASTM B338. Titanium welded pipes and titanium seamless pipes are different in terms of chemical composition, mechanical properties and process performance. Not much, or even the same. With the advancement of titanium welded pipe welding and heat treatment technology, single-gun or multi-gun TIG/PAW self-fusion welding is generally used for thin-walled titanium welded pipes in China. After welding, online heat treatment process is adopted. By optimizing welding and annealing processes, the base material and welding The microstructures of the seam and the heat-affected zone are basically close, and at the same time, the welding stress is eliminated and the weld structure is uniform. Through comparison, it is found that the weld composition of the titanium welded pipe is basically the same as the base metal, and the mechanical properties and corrosion resistance of the weld are the same as the base metal.
2.2 The appearance and quality of titanium welded pipe are better than titanium seamless pipe
The titanium welded pipe is welded by cold-rolled coils, with uniform wall thickness, good concentricity, good finish, and no fouling in the pipe. Especially for thin-walled titanium tubes, the seamless rolling process cannot meet its technical requirements. After the rolling or drawing process, it is difficult for titanium seamless pipes to achieve a wall thickness of less than 1 mm; while titanium welded pipes can achieve a wall thickness of 0.5 mm or less, saving a lot of materials and costs. At the same time, due to the thinner 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 protection advantages of titanium welded pipes are outstanding
The production process of titanium seamless tube is complicated. Three-roll or multi-roll mills and drawing machines are conventionally used to roll or draw a tube blank of a certain specification through multiple passes, and finally produce seamless tubes after diameter reduction and wall reduction. The production efficiency and yield rate of this process are low. From sponge titanium to pipe, the material waste is large by rolling or drawing, the yield rate is only about 50%, and mass production cannot be realized, and the production cycle is relatively long.
The titanium welded pipe is produced through an automated continuous production line, using titanium strips with uniform wall thickness through cold bending forming, 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 around 80%. If the titanium coil is used as the raw material, the material utilization rate is above 95%. With the rapid development of China's domestic titanium industry and the 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 to length according to customer requirements. Length, short delivery time, high material utilization rate, unit cost will be lower than seamless pipe.
Titanium seamless pipes are usually produced by rolling or drawing processes. A large amount of rolling oil and drawing oil will be used in the production process, and the production site will be polluted seriously. After rolling and drawing titanium pipes, the grease and dirt on the inner and outer surfaces of the pipes need to be degreased and pickled. The pickling process pollutes the environment. 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 mass-produced through automated production lines, with stable quality and high production efficiency. Except for certain energy consumption such as water and electricity, the production process has almost no pollution to the environment.
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 also increase. Although the investment cost of titanium welded pipe is higher than that of common fluid transportation pipelines, its cost is lower than that of titanium seamless pipes. Based on the analysis of the service life and maintenance cycle of titanium welded pipes, the investment cost of titanium welded pipes can be compensated in use. , The use of titanium welded pipes in piping systems can reduce production costs by reducing the number of regular maintenance, reducing downtime, improving product quality, and increasing pipeline life. Especially in recent years, the global titanium industry has not been very prosperous, and the competition has been very fierce. The price of titanium welded pipes has been at a relatively low level. Enterprises in the petrochemical industry have adopted titanium welded pipes for lower initial equipment investment costs.