With the rapid development of China's economic construction, the consumption of stainless steel continues to increase. The demand for stainless steel pipes is also expanding day by day and the market prospects are promising. However, at present, there is a certain gap between the domestic stainless steel pipes and the market demand in terms of varieties, specifications, quantity, and quality. In terms of varieties, domestic stainless steel seamless steel tubes are still dominated by 1Gr18Ni9Ti that has been eliminated from abroad, and the quality of domestically produced urea-grade, high-precision stainless steel is still difficult to guarantee; the heat exchanger tubes for power station boilers and urea tubes for fertilizer plants mainly rely on imports; Duplex stainless steel pipes with good corrosion resistance are rarely produced domestically. In terms of product specifications, large-diameter, high-demand stainless steel tubes and super-long tubes have large gaps; the production capacity of medium- and small-diameter stainless steel tubes for general use is greater than market demand. In terms of product quantity, higher standards of industrial welded pipes, especially high-demand industrial pipes, are basically blank. The output of common stainless steel pipes is in balance with the overall market demand, the production capacity of ordinary seamless pipes is surplus, and the standard of medium and low grades is Stainless steel decorative welded pipe market exceeds demand.
In the past ten years, with the rapid expansion of application fields, domestic demand for stainless steel pipes of different materials, different specifications, different varieties, and different uses has skyrocketed; coupled with the attraction of stainless steel pipes with high added value, companies manufacturing stainless steel pipes from the 1980s At that time, more than a dozen companies had developed to more than 400 at present, and the comprehensive production and processing capacity exceeded 1 million tons. The actual output increased from 50,000 tons in 1989 to 390,000 tons in 1999; there are very few enterprises with output of 5,000 tons. Most are small plants with an annual output of 1,000 tons or less. Steel grades developed from single austenite to martensite and ferritic dual-phase steels and high alloy steels; product varieties include seamless steel tubes including cold drawn tubes, cold rolled tubes, hot extruded tubes, centrifugal casting tubes, and spirals Pressure pipe; Welded pipe includes: plasma welding, argon arc welding, submerged arc welding, light speed welding and high frequency welding etc. The stainless steel pipe that can be produced basically covers the standard specifications of all countries in the world, the specification of stainless steel profiled pipe, There are more than one hundred varieties, and the products are used in many fields such as industrial and civil use. The stainless steel welded pipe production of some developed countries in the world accounts for 65% to 75% of the total output of stainless steel pipes. The production capacity of stainless steel welded pipes in China is inconsistent with the domestic market demand. It is forecasted that in the 21st century, the annual demand for stainless steel pipes in the domestic market will be at least 60,000 tons, and it will be necessary to make up for the imported products.
The domestic stainless steel welded pipe production is mainly produced by the continuous forming unit and the UOE method. The welding methods are inert gas shielded welding and continuous forming units. In the process of producing thin-walled steel pipes, single-arm welding is generally configured. The industrial pipe with a wall thickness of 2-3.2 mm also has 3-4 gun welding. A plasma and three-gun argon arc welding and other welding methods. Due to the high energy plasma deep melting ability. In steel pipes with a wall thickness of less than 6 mm, plasma welding and single-side welding are used. The UOE method is mainly to produce large-diameter, thick-walled stainless steel tubes and generally uses plasma arc welding. Nowadays, it is possible to produce high-quality stainless steel welded pipes for industrial use and the bead on the inner and outer surfaces of steel pipes for smooth processing. Make the weld and the base material have the same performance. In order to ensure the quality of industrial pipes, advanced weld seam tracking, post-weld finish rolling and other advanced technologies have been adopted. At present, domestically produced stainless steel pipes are generally still processed offline. The heat treatment furnaces for the heat treatment of stainless steel tubes are mostly gas-fired, continuous roller hearth furnaces, in addition to an electric heating continuous roller hearth furnace, three fuel continuous roller hearth furnaces, and two box furnaces. At present, advanced on-line heat treatment has also been applied. There are five continuous production lines in use in China. Muffle tube light treatment furnace and roller bottom protection atmosphere bright heat treatment furnace have also been adopted. At present, the tubes of domestic seamless steel tubes are mainly produced in factories such as Shanghai No. 5 Steel Works, TISCO, Daye, Fushun, Xining, Nantong, Fengye, etc. There are also some regions where the production of tube blanks uses recycled materials through intermediate-frequency furnace melting of scrap steel production. .
The major steel plate production sites for domestic industrial welded pipes are Taigang, Zhangjiagang Pohang, Ningbo Baoxin and Shanghai No. 3 Steel Works. Some imported raw materials are also used. The landscape material of architectural decoration includes imported thin strip steel as production raw material, hot rolled narrow strip raw material produced through cold rolling, and intermediate frequency furnace production billet, narrow hot strip produced by forging and rolling, and narrow strip produced by cold rolling. . At present, the quality of stainless steel seamless pipes produced in China is uneven.
Through statistical analysis and probabilistic analysis, 25% of the 70,000 tons produced last year can be reliably used in petroleum, chemical, fertilizer, boiler, aerospace and nuclear power industries. About 60% can be applied in food, brewing, medicine, papermaking, printing and dyeing, urban environmental protection and other industries. About 20% are unqualified products or products that can be used. The main problem is that the chemical composition of the steel pipe exceeds the allowable deviation; the cleanliness of the steel is not enough, and impurities are excessive, resulting in unqualified grain size; and production cannot be performed according to the heat treatment system. Intergranular corrosion is unqualified; internal and external surface defects are serious, heavy skin, slag inclusions, internal folds are not removed, and severely deviated. The industrial welded pipe has fewer defects; round and straight industrial pipes with large and medium diameters are not satisfactory; the welded pipe for decoration has serious problems such as poor composition, excessive pipe diameter and poor wall thickness.
At present, China's fertilizer industry has a gap of 30 million tons per year. It is reported that the relevant state departments plan to invest 5 billion yuan to build 10 large-scale fertilizer plants. It is understood that only a set of 550,000 tons of urea and 300,000 tons of synthetic ammonia large-scale urea plant process piping, heat exchanger tubes, "urea-grade" special pipe, duplex stainless steel pipe and various other steel pipes total 2018.5 tons .
The development of the petrochemical industry also has a large demand for stainless steel tubes. The number of stainless steel tubes required for overhauling and replacing a polyene phenol plant is 99.1 tons, of which Φ108-630mm large-diameter stainless steel seamless tubes account for 53.79%. It is estimated that by 2005, the ethylene equivalent demand will be approximately 15 million tons, the demand for five major synthetic resins will be 25 to 27 million tons, and 14 main organic acids such as acetic acid, vinyl acetate, maleic anhydride, ethylene oxide, phenol, acetone and phthalic anhydride. The demand for raw materials will reach about 5.6 million tons.
At the beginning of this century, China’s installed capacity for power generation will reach 260-300 million kilowatts, 5 million kilowatts of nuclear power will be built, 5 million kilowatts under construction, and 10 600,000 kilowatts of nuclear power plants will be built one after another. A 600,000 kilowatt boiler uses 455 tons of steel pipes of various specifications. Each 600,000 kilowatt nuclear power plant requires 100 tons of evaporator "U" heat transfer tubes. In addition, there are a large number of stainless steel precision tubes and control rods, nuclear fuel tubes, and so on. In this century, a total of about 6,000 tons of various nuclear-use pipes were needed. In the boiler tube, the stainless steel super long tube completely depends on the import, for example, Φ16mm×2.11-2.05mm, length is 22-24m and Φ16mm×1.2-3.0mm, length is 12.5-18.0m The annual demand is 7,000 tons.
The automotive industry also has a lot of demand for stainless steel pipes. According to calculations, only the Sino-US joint venture BUICK sedans and Shanghai Volkswagen's Santana B5 limousines consume 560 tons of stainless steel pipes. The aerospace industry requires 200 tons of precision stainless steel pipes and high-temperature full-gold pipes.
Electronic, instrumentation, metallurgical and other industries require about 5,000 tons of stainless steel pipes each year. The light industry and medical and pharmaceutical industries such as beverages, alcohol, food, textiles, printing and dyeing are used for equipment manufacturing and maintenance, etc. The annual consumption of stainless steel pipes is more than 20,000 tons.
Stainless steel pipelines and their water delivery equipment are the most advanced basic water purification materials in the world today, and some cities have also started to use stainless steel pipes for the transportation of fluids such as water and gas. Wuhan invested heavily in the use of stainless steel pipelines and equipment, renovated the main water purification pipelines and water collecting tanks of 13 water plants, and will also build new high-rise residential buildings and office buildings in the shortest time possible. Stainless steel pipe water supply. Water supply pipelines for some residents in Ningbo and Daqing have also begun to use stainless steel pipelines. The future civilian sector will be a huge market for stainless steel pipes.
People in the industry believe that the disordered development and competition in the stainless steel tube industry must be valued and regulated, and that all companies from production to sales should be self-disciplined so that the stainless steel tube manufacturing industry in China can develop in a healthy and vigorous manner.