2021-06-07
Thanks to innovations in production technology, equipment upgrading, increasing production volumes and improving product quality, China's stainless steel pipe industry is developing at a rapid pace, demonstrating a favorable situation on both the demand and supply sides.
On the demand side, the demand for stainless steel pipes is constantly growing in areas such as infrastructure construction, mechanical engineering and equipment manufacturing, energy and chemical industry, marine engineering, environmental projects, defense industry and gas transportation. The market for stainless steel pipes is rapidly expanding. The growth is especially noticeable in the field of civil water supply, where many local authorities, guided by the interests of the population, are taking incentive measures to develop the use of stainless steel pipes. This places higher demands on production volume, assortment, quality, standards, technology, environmental friendliness, installation and service of products.
On the supply side, China has made significant progress in manufacturing technologies for large-diameter thick-walled and thin-walled seamless stainless steel pipes. Significant progress has been made in the construction of environmentally oriented enterprises, the production of environmentally friendly products, the improvement of management systems, increasing the yield of suitable products and reducing energy consumption. Historical breakthroughs have been achieved, and the quality of many new types of stainless steel pipes has reached world-class levels.
Currently, many manufacturers of plastic pipes, metal-plastic pipes and cast iron pipes are switching to the production of stainless steel products, which leads to increased competition in the market. In the face of increasing competition, China's stainless steel pipe industry must accelerate transformation and upgrading.
Enterprises in the industry follow market trends, eliminate bottlenecks that hinder further development, explore new product developments and technology improvements, implement intelligent manufacturing and environmentally friendly production methods, ensure precise positioning of enterprises, and strive to make China's stainless steel pipe industry a world leader, consistently realizing the dream of China's renaissance.
1.Production status of stainless steel pipes
The production of stainless steel pipes in China began to develop in the 1950s, but the industry began to actively grow in the late 1980s. Especially after 2000, there was a deep rethinking of the requirements for production technologies, output volume and product quality. The level of development of production equipment was significantly increased, which made it possible to ensure product quality already at the production stage.
According to incomplete statistics, the total production volume of seamless stainless steel pipes in 2020 was about 1.261 million tons.
The volume of industrial consumption of welded stainless steel pipes in 2020 amounted to about 465 thousand tons.
The sales volume of stainless steel pipes for water supply in 2020 reached 6.5 billion yuan, which corresponds to approximately 250 thousand tons of products. The main production and consumption regions are Guangdong and Zhejiang provinces.
Other welded pipes with a volume of approximately 1.9 million tons are mainly used for urban improvement and building structures.
Currently, a number of new projects of pipe enterprises have already received land plots and the necessary permits and are at the construction stage:
(1).Delong project in Xiangshui County with a capacity of 400 thousand tons of stainless pipes per year;
(2).Baofeng Steel project in Songyang County with a capacity of 140 thousand tons of stainless pipes per year;
(3).The Shangshang Desheng project in Jiaxing city with a capacity of 100 thousand tons of stainless pipes per year;
(4).Project to produce 100 thousand tons of seamless stainless steel pipes in Jiangsu Province.
With the development of the water supply pipe market, major plastic pipe manufacturers such as Hubei Jinniu, Foshan Liansu and Zhejiang Zhongcai have also begun to invest in stainless steel pipe production.
2. Products and technology for the production of stainless steel pipes
The production process of seamless stainless steel pipes includes the following steps:piercing of pipe blanks, cold working, heat treatment, pickling and quality control.
The production of a hollow billet is the first plastic deformation operation in the production of seamless pipes.
There are several ways to produce hollow blanks:
(1). Helical piercing on two- or three-roll mills;
(2).Hydraulic flashing;
(3).Push stitching;
(4).Extrusion on presses.
At present, China mainly uses twin-roll cross-roller piercing and extrusion method.
Cold processing includes:
(1).Cold rolling;
(2).Cold drawing;
(3).Cold extrusion;
(4).Rotary rolling.
In general, cold working mainly uses rolling in combination with drawing.
Roller hearth furnaces and chamber furnaces are mainly used for heat treatment in China. TISCO uses solution annealing furnaces with a hydrogen protective atmosphere manufactured by LOI.
Welded stainless steel pipes are produced on both continuous lines (ERW) and discrete production lines (UOE, JCOE).
On the ERW line, coiled steel is cut into strips of the required width, after which a W-shaped profile is formed and welding is performed (argon-arc, plasma or combined plasma-argon-arc). Single-torch, two-torch or three-torch welding systems are used. Laser or submerged arc welding is generally not recommended. The use of high-frequency welding for industrial stainless steel pipes is considered a bad solution.
After welding the following are performed:
1.Cleaning the weld;
2.Calibration;
3. Rolling the weld;
4. Induction heat treatment in a hydrogen atmosphere;
5.Cutting;
6. Flaw detection;
7.Hydraulic tests (or pneumatic tests under water);
8. Off-line etching.
The UOE or JCOE technology involves cutting a steel sheet to the dimensions of the future pipe. Then the edges of the sheet are formed on the press in accordance with the radius of the pipe, then U-shaped forming is performed, after which the product is closed into an O-shape and welded. After O-forming, pipe expansion, heat treatment, calibration, straightening, quality control and finished product storage are carried out.
Source:China Special Steel Association, Stainless Steel Branch.
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