Stainless steel pipes can be divided into equal cross-section pipes and variable cross-section pipes according to the longitudinal cross-section shape. Variable cross-section tubes include tapered tubes, stepped tubes and periodic cross-section tubes. According to the purpose, it can be divided into oil well pipes (casing, tubing and drill pipe, etc. ), pipeline pipes, boiler tubes, mechanical structure pipes, hydraulic prop pipes, gas cylinder pipes, geological pipes, chemical pipes (high-pressure fertilizer pipes, petroleum cracking pipes) and ship pipes.
Stainless steel industry in Wenzhou
Wenzhou stainless steel industry is a new industry, which originated in the early 1980s. After 20 years of development and exploration, it has gained considerable popularity and certain influence in the domestic market.
At present, there are more than 130 production enterprises, and the development momentum is good. 38 sets of piercing equipment in the whole industry. There are more than 500 cold-rolling and cold-drawing equipment and 6 smelting equipment, all of which are refined outside the furnace, and other equipment is relatively complete. The production capacity and scale of enterprises are constantly expanding and growing. 200 1 5 enterprises with annual output exceeding 100 million yuan, and 10 enterprises were rated as star-rated enterprises in cities and districts. In order to ensure the product quality, the analysis and testing equipment such as water pressure, eddy current, ultrasonic flaw detection and direct reading spectrometer are constantly increasing and improving. 200 1 has been sampled and tested by the superior technical supervision department, and the qualified rate is over 80%. There are more than 300 technicians and managers with various senior and intermediate titles, which makes the enterprise gradually embark on the track of standardized production and management. Wenzhou stainless steel industry mainly produces stainless steel pipes and rods, with more than 400 varieties, specifications and models. 200 1 year, the sales of stainless steel reached17150,000 yuan, and the output reached106,000 tons. The stainless steel bar is 222 million yuan, the output is 2 1 10000 tons, and the national tax is more than 654,380+00 million yuan. The export volume of steel pipes has also increased year by year, reaching 5000T from 200 1 year. It is estimated that the export volume this year will be 8000~ 10000T, and 10 enterprises have obtained the right to import and export by themselves. Stainless steel pipes are exported to dozens of countries and regions in Southeast Asia and the European Union, and are highly appreciated by foreign merchants and users.
Wenzhou stainless steel pipe industry used to be blank, with rapid development and expanding scale, but there is still a certain gap in production capacity, which still cannot meet the domestic market demand. The future development ideas and specific practices of Wenzhou stainless steel industry are as follows:
1. Focusing on increasing product output, strengthening enterprise internal management, improving enterprise scale and grade, further improving Wenzhou stainless steel pipe and enterprise popularity, encouraging enterprises to develop into groups, strengthening the introduction and training of technicians and management talents, and strengthening the construction of production equipment to ensure and improve product quality.
3. Take the road of brand development, take stock of the credit of Wenzhou stainless steel industry and entrepreneurs, and shape the brand awareness of China.
3. Establish Wenzhou Stainless Steel Pipe Production Park, gather stainless steel production enterprises, make them large-scale, up-to-grade, leading and branded, and form group production; Through merger, joint venture, equity participation and joint venture. To achieve the planning goal of "key development" of Zhejiang Economic and Trade Department.
4. Run Wenzhou stainless steel professional market well. The stainless steel industry is developing rapidly, but because there is no professional market of a certain scale, it can't attract customers from all corners of the country. Production enterprises can only set up operations all over the country, which not only increases the cost of enterprises, but also hinders their development. If a professional market is built, integrating production, sales and service, the production enterprises will really stand behind, go to the whole country and rush out of the country.
This kind of steel pipe can be divided into two categories: stainless steel seamless steel pipe and stainless steel welded steel pipe (slotted pipe), which can be divided into hot rolling, extrusion, cold drawing and cold rolling according to different manufacturing processes, and can be divided into round pipe and special-shaped pipe according to cross-sectional shape. Round steel pipes are widely used, but there are also some special-shaped stainless steel pipes, such as square, rectangle, semicircle, hexagon, equilateral triangle and octagon.
For steel pipes subjected to fluid pressure, water pressure test should be carried out to test their pressure resistance and quality. If they do not leak, soak or swell under the specified pressure, they will be qualified. According to the standard or the buyer's requirements, some steel pipes shall be subjected to curling test, flaring test and flattening test.
Seamless stainless steel tube, also known as stainless steel seamless tube, is made of steel ingot or solid tube blank after perforation and then hot rolling, cold rolling or cold drawing. The specification of seamless steel pipe is expressed by outside diameter * wall thickness mm.
20 1 stainless steel pipe -S20 100 (AISI. ASTM)
The full name of 304 stainless steel pipe is SUS304 stainless steel pipe.
SUS304 stainless steel pipe belongs to American brand, and the domestic brand is equivalent to 0Cr 19Ni9 stainless steel pipe, which is usually replaced by 0Cr 18Ni9.
The anti-rust mechanism of stainless steel is that the alloying elements form a positive potential and no longer have the ability to transport electrons to the oxidant.
304 material rust reasons are as follows:
1. Chloride ion exists in the use environment.
Chloride ion exists widely, such as salt, sweat, seawater, sea breeze, soil and so on. In the presence of chloride ion, stainless steel corrodes quickly, even exceeding ordinary low carbon steel. Chloride ion forms a complex with Fe in alloy elements, which reduces the positive potential of Fe and is then taken away by oxidant for oxidation.
Therefore, there is a requirement for the use environment of stainless steel, which needs to be wiped frequently to remove dust and keep it clean and dry.
3 16 and 3 17 stainless steels are molybdenum-containing stainless steels. The molybdenum content in 3 17 stainless steel is slightly higher than that in 3 16 stainless steel. Because 3 16 stainless steel contains molybdenum, its overall performance is better than that of 3 10 and 304 stainless steel. At high temperature, when the concentration of sulfuric acid is lower than 15% and higher than 85%, 3 16 stainless steel. 3 16 stainless steel also has good chloride corrosion resistance, so it is usually used in marine environment.
With the development of social economy, the application of stainless steel pipe is more and more extensive. It will definitely bring new changes to various fields.
Theoretical weight formula of stainless steel pipe: W= (outside diameter-wall thickness) x wall thickness x0.0249 1x length, where w is kg, outside diameter and wall thickness are mm, and length is m. Production technology of stainless steel welded pipe:
Raw materials-cutting-welding pipe making-trimming-polishing-inspection (spray printing)-packaging-delivery (warehousing) (decorative welded pipe)
Raw materials-slitting-welding and pipe making-heat treatment-correction-straightening-trimming-pickling-hydrostatic test-inspection (spray printing)-packaging-delivery (warehousing) (pipe for pipe fitting in welded pipe industry) The inner diameter of annealed stainless steel is greater than 6.0mm, and the wall thickness is less than 13mm. The HRB hardness and HRC hardness of stainless steel pipes with inner diameter greater than 30mm and wall thickness greater than 65438±0.2mm were measured by Rockwell hardness tester. For stainless steel pipes with inner diameter greater than 30mm and wall thickness less than 65438±0.2mm, the hardness of HRT or HRN is measured by surface Rockwell hardness tester. For stainless steel pipes with inner diameter less than 0mm and greater than 4.8mm, the hardness of HR 15T was tested by Rockwell hardness tester. When the inner diameter of stainless steel pipe is greater than 26 mm, the hardness of the inner wall of the pipe can also be detected by Rockwell or Surface Rockwell Hardness Tester.