All ends of the opening and has a hollow section, and its length and the ratio of the circumference of the larger section of steel, can be called steel. When the length and the circumference of the section is relatively small, can be called pipe or pipe fittings, they belong to the scope of pipe products.
For over sixty years, architects have been using stainless steel to build cost-effective permanent buildings. Many of the existing buildings fully illustrate the correctness of this option. Some are very entertaining, such as the New York City Chrysler building. However, in many other applications, the role of stainless steel is not so compelling, but in the building’s aesthetic and performance plays an important role. For example, stainless steel is the preferred material for designers in the construction of sidewalks where population flow is large, because the metal has more abrasion and crease resistance than other metal materials of the same thickness.
Stainless steel has been used for more than 70 years in the construction of new buildings and structural materials for the restoration of historical monuments. The early design was calculated in accordance with the basic principles. Today’s design codes, such as the ANSI / ASCE-8-90 Cold Formed Stainless Steel Structural Design Code and the Structural Stainless Steel Design Handbook jointly published by NiDI and Euro Inox, have simplified the use of a long service life, Design of Structural Members with Good Integrity.
The export of stainless steel is an important part of China’s export economy. It plays an important role in boosting China’s economic growth. However, from the present situation of China’s stainless steel trade, China’s stainless steel exports have encountered great resistance.
Since last year, foreign frequently came to China’s stainless steel casting products, “double reverse” news, which is China’s stainless steel casting industry has a great impact, the export is China’s stainless steel industry in the development of a large part of its industry The development of a huge market share in the face of economic downturn, the pace of development slowdown in the case of China’s stainless steel industry should continue to enhance the quality of products, better development of overseas trade and deal with trade protectionism to suppress, Products and environmental protection, energy resources, human environment together to enhance the competitiveness of stainless steel products, the only way to achieve undefeated position in foreign trade.
- Surface resistance less than 1000 megabytes
- Wear protection
- Excellent chemical resistance
- Good resistance to alkali metals and acids
The production process of stainless steel seamless tube
a. Round steel preparation;
c. Hot rolling piercing;
d. Cutting head;
h. Cold-rolled processing;
j. Solution heat treatment;
l. Cutting tube;
n. Product testing.
Strength refers to the metal in the external force, resistance to plastic deformation and fracture ability
When the metal specimen is stretched, the ratio of the maximum load to the original cross-sectional area of the specimen before breaking is called the tensile strength
Then Pb——The maximum load before breaking the specimen（N）
Fo——The original cross – sectional area of the specimen（mm ）
The specimen is located in the middle of the two bearings under the action of the concentrated load, so that when broken, breaking the section to withstand the maximum positive pressure
On a round specimen：σbb=——
For rectangular specimens：σbb=——
Then P——The maximum concentrated load the specimen is subjected to（N）
L——Span between two bearing points(mm)
d——The outer diameter of the circular specimen cross – section(mm)
b——The width of the rectangular cross section specimen(mm)
h——The height of the rectangular cross section specimen(mm)
Stainless steel pipe is divided into ordinary carbon steel pipe, high-quality carbon structural steel pipe, alloy structural pipe, alloy steel pipe, bearing steel pipe, stainless steel pipe and to save precious metals and meet the special requirements of double metal composite pipe, coating and coating pipe . Stainless steel tube of a wide range of different uses, its technical requirements vary, production methods are also different. The current production of steel pipe diameter range of 0.1-4500mm, wall thickness of 0.01 ~ 250mm. In order to distinguish the characteristics, steel pipes are usually classified according to the following method.
Stainless steel pipe production methods are divided into two types of seamless pipe and pipe, seamless steel pipe can be divided into hot-rolled tubes, cold-rolled tubes, cold drawn and extruded tubes, cold drawn, cold rolled steel pipe is the second Processing; welded pipe is divided into straight seam welded pipe and spiral welded pipe.
Stainless steel tube according to the cross-sectional shape can be divided into round tube and special-shaped tube. The special-shaped pipe has rectangular pipe, rhombus pipe, oval pipe, hexagonal pipe, octagonal pipe and various sections of asymmetric pipe. Shaped tube is widely used in a variety of structural parts, tools and mechanical parts. Compared with the tube, shaped pipe generally have a larger moment of inertia and section modulus, a greater bending, torsion resistance, can greatly reduce the weight of the structure, saving steel.
Stainless steel tube according to the longitudinal section shape can be divided into equal cross-section tube and variable cross-section tube. Variable cross-section of possession of a tapered pipe, step-shaped pipe and periodic section of the pipe.
Shape of the tube end
Stainless steel tube according to the state can be divided into tube-end light pipe and car thread pipe (with threaded steel pipe). The wire tube can be divided into ordinary wire tube (conveying water, gas and other low-pressure pipe, the use of ordinary cylindrical or tapered pipe thread connection) and special threaded pipe (oil, geological drilling tube for important car wire, Special thread connection), for some special tube, in order to compensate for the impact of the thread on the tube end strength, usually in the wire before the end of the pipe thickening (thickening, thickening or thickening inside and outside).
It can be divided into oil well pipe (casing, tubing and drill pipe etc.), pipeline pipe, boiler pipe, mechanical structure pipe, hydraulic prop pipe, gas pipe, geological pipe, chemical pipe (high pressure chemical fertilizer pipe, petroleum cracking pipe ) And ships.
Wenzhou stainless steel industry
Wenzhou stainless steel industry is an emerging industry, originated in the early 1980s, after 20 years of exploration and exploration in the domestic market has been quite well-known and a certain influence.
The current production enterprises of more than 130, has a good development and expansion of the momentum. The whole industry perforation equipment 38. Cold-rolled, cold-drawn equipment more than 500 Taiwan, smelting equipment 6, all with furnace refining, other equipment more complete. The enterprise’s production capacity and scale are constantly expanding and strengthening. 2001, the output value exceeding 100 million yuan enterprises have five, more than 10 enterprises were rated as cities, district star enterprises. In order to ensure product quality, water pressure, eddy current and ultrasonic testing, direct reading spectrometer and other analytical testing equipment are constantly increasing and improving. 2001 by the higher technical supervision departments sampling test, the pass rate of 80% or more. Have all kinds of high and mid-level titles of the technology, management staff of more than 300 people, is gradually onto the standardization of production and management track. Wenzhou stainless steel industry is the production of stainless steel tube and stainless steel rod, variety, size, model has reached more than 400 kinds. 2001 stainless steel sales of 1.715 billion yuan, production reached 106,000 tons. Stainless steel rods 222 million yuan, the output of 2,11 million tons, turned over to state taxes amounted to more than 100 million yuan. Steel pipe exports also increased year by year, in 2001 for the 5000T, is expected to export this year, 8000 ~ 10000T, 10 enterprises have been made import and export right. Stainless steel pipe exported to Southeast Asia, the European Union dozens of countries and regions, by foreign businessmen and users of appreciation.
Stainless steel pipe industry in Wenzhou was originally blank, rapid development, expanding the scale, but there is still a gap in production capacity, still can not meet the needs of the domestic market. Wenzhou stainless steel industry in the future development of ideas and specific practices are:
⒈ to improve product production as the center, to strengthen internal management, improve the scale and grade of enterprises as the goal, to further improve the visibility of Wenzhou stainless steel pipe and enterprises to encourage enterprises to the Group of development, strengthen the technical personnel, management personnel introduction and training, Strengthen the construction of production equipment to ensure and improve product quality.
⒉ to brand development, the number of stainless steel industry and entrepreneurs in Wenzhou credit, shaping the Chinese brand awareness.
3, the establishment of the Wenzhou stainless steel pipe production park, gathering stainless steel production enterprises, so that the scale, the grade, a leading, a brand name, the formation of group production; through mergers, affiliated, equity, joint, etc., Focus on the development of “planning objectives.
⒋ Wenzhou good professional stainless steel market. The rapid development of the stainless steel industry, but because there is no certain size of the professional market, can not provoke Wuhu Sihai passengers, so manufacturers can only set up throughout the country business, not only increases the cost of the enterprise, but also hindered the development of enterprises. If the completion of a professional market, production, sales service in one, will enable manufacturers to truly stand back, to the country, out of the country.
Such steel pipe can be divided into stainless steel seamless steel pipe and stainless steel welded pipe (with pipe) two categories, according to the different manufacturing processes can
stainless steel pipe
stainless steel pipe
As follows: hot rolling, extrusion, cold drawing and cold rolling these basic types, according to the cross-sectional shape can be divided into circular and special-shaped tube, is widely used in circular steel pipe, but there are some square, rectangular, , Hexagonal, equilateral triangle, octagonal, and other special-shaped stainless steel pipe.
For the hydraulic pressure to withstand the pressure of the steel pipe hydraulic pressure test to test its ability and quality, at the required pressure does not occur under the leakage, soaked or swollen for qualified, some steel pipe but also in accordance with standard or demand side curling test , Flaring test, flattening test.
Seamless stainless steel pipe, also known as stainless steel seamless pipe is made of steel ingots or solid tube through the perforation of capillary, and then by hot-rolled, cold-rolled or cold dial made. The specifications of the seamless steel pipe are expressed in millimeters in outer diameter * wall thickness.
201 stainless steel tube – S20100 (AISI.ASTM)
304 stainless steel tube full name SUS304 stainless steel tube
SUS304 stainless steel tube material belonging to the US brand of stainless steel tube, the domestic brand is equivalent to 0Cr19Ni9 stainless steel tube, usually 0Cr18Ni9 alternative.
Stainless steel anti-rust mechanism is the formation of alloying elements positive potential, no longer have the ability to transport electrons to the oxidant.
304 material rust phenomenon, there may be the following reasons:
⒈ the use of chloride ions in the environment.
Chloride is widely present, such as salt, sweat, sea water, sea breeze, soil and so on. Stainless steel in the presence of chloride ions in the environment, corrosion quickly, even more than ordinary low-carbon steel, chloride and alloying elements in the formation of Fe complexes, the Fe potential is reduced, then the oxidant to take away the electrons are oxidized.
So the use of stainless steel environment requirements, but also need to always wipe, remove the dust, keep clean and dry.
316 and 317 stainless steels are molybdenum-containing stainless steels. 317 stainless steel in the molybdenum content is slightly higher than the 316 stainless steel due to 316 stainless steel containing molybdenum, the total performance of the steel is better than 310 and 304 stainless steel, high temperature conditions, when the sulfuric acid concentration below 15% and 85% , 316 stainless steel has a wide range of uses. 316 stainless steel also has a good resistance to chloride erosion performance, it is usually used in marine environments.
With the socio-economic development of stainless steel, its application has also been more and more widely. Will bring in all areas of a new change.
The theoretical weight of the stainless steel tube formula: W = (diameter – wall thickness) x wall thickness x0.02491x length, where W unit is kg, diameter, wall thickness units are mm, length unit meters (m).
Stainless steel welded pipe production process:
Raw materials – Slitting – Welding pipe – Repair side – Polishing – Inspection (printing) – Packaging – Shipping (warehousing) (decorative pipe)
Raw Materials – Slitting – Welding Pipe – Heat Treatment – Straightening – Straightening – Repairing – Pickling – Hydrostatic Testing – Inspection (Printing) – Packaging – Shipping (Pipe for industrial piping)
Stainless steel tube commonly used Brinell, Rockwell, Vickers hardness of three indicators to measure its hardness.
In the stainless steel pipe standard, Brinell hardness is the most widely used, often to indentation diameter to represent the hardness of the material, intuitive and convenient. But is not suitable for steel pipes of relatively hard or thin steel.
Stainless steel tube Rockwell hardness test with Brinell hardness test, are indentation test method. The difference is that it is measured indentation depth. Rockwell hardness test is a widely used method, which HRC in the steel pipe standard used in second only to Brinell hardness HB. Rockwell hardness can be applied to determine from very soft to very hard metal material, which makes up for the Brinell method is not, than the Brinell method is simple, can be read directly from the hardness of the dial hardness. However, because of its small indentation, so the hardness value as Brinell method is accurate.
Stainless Steel Pipe Vickers hardness test is also an indentation test method can be used to determine the thin metal materials and surface layer hardness. It has the main advantages of the Brinell and Rockwell method, and overcomes their basic shortcomings, but not as simple as the Rockwell method, the Vickers method is rarely used in the pipe standard.
Stainless steel pipe diameter 6.0mm or more, wall thickness of 13mm or less annealed stainless steel pipe, can be used W-B75 Wechsler hardness tester, which tests very fast, simple, suitable for stainless steel pipe fast and non-destructive testing. Stainless steel tube diameter greater than 30mm, wall thickness greater than 1.2mm stainless steel tube, using Rockwell hardness tester to test HRB, HRC hardness. Stainless steel tube diameter greater than 30mm, wall thickness of less than 1.2mm stainless steel tube, the use of surface Rockwell hardness tester, HRT or HRN hardness test. Diameter less than 0mm, greater than 4.8mm stainless steel tube, the use of special Rockwell hardness of the pipe, testing HR15T hardness. When the stainless steel pipe diameter greater than 26mm, can also be used Rockwell or Rockwell hardness tester to test the hardness of the pipe wall.
Stainless steel tube is an economical section steel, is an important product in the steel industry, can be widely used in life decoration and industry, many people in the market for the production of staircase handrails, windows, railings, furniture and so on. There are two common materials 201 and 304.
Accounting for 8% of the total steel around 16%, its application in the national economy is extremely broad. As the steel pipe has a hollow section, and therefore the most suitable for liquid, gas and solid pipelines; same time with the same weight of round steel, steel pipe section coefficient, bending bending strength, it has become a variety of mechanical and building structures On the important material. Structures and components made of stainless steel tubes have a greater cross-sectional modulus than solid parts when the weight is equal. Therefore, the stainless steel tube itself is a economical section of the steel, it is an important part of high-performance steel, especially in the oil drilling, smelting and transportation industries demand, followed by geological drilling, chemical industry, construction industry, machinery Industrial, aircraft and automobile manufacturing as well as boilers, medical equipment, furniture and bicycle manufacturing, also need a large number of various steel pipe. With the atomic energy, rockets, missiles and aerospace industry and other new technologies, stainless steel pipe in the defense industry, science and technology and economic construction in the increasingly important position.
The safety and reliability of the stainless steel pipe, health and environmental protection, economical application, thin wall of pipeline and new reliable, simple and convenient connection method have been developed successfully, which make it have more irreplaceable advantages of other pipes. , The use will be more and more popular, promising.
Since stainless steel already possesses many of the desirable properties required for building materials, it can be said to be unique in metals, and its development continues. In order to make stainless steel in the traditional application of better performance, has been to improve the existing types, and, in order to meet the stringent requirements of advanced building applications, is developing new stainless steel. Stainless steel has become one of the most cost-effective materials chosen by architects because of the ever-increasing productivity and quality improvements.
Stainless steel sets performance, appearance and use characteristics in one, so the stainless steel will remain one of the world’s best building materials.
With the implementation of China’s reform and opening-up policy, the national economy has achieved rapid growth, urban housing, public buildings and a large number of tourist facilities, the hot water supply and domestic water supply put forward new demands. In particular, water quality issues, people pay more and more attention to, requirements are also rising. Galvanized steel pipe because of its common pipe corrosion, under the influence of relevant national policies, will gradually withdraw from the stage of history, plastic pipe, composite pipe and copper pipe has become the common pipe system. But in many cases, stainless steel pipe is more advantages, especially the wall thickness of only 0.6 ~ 1.2mm thin-walled stainless steel pipe in the high-quality drinking water systems, hot water systems and safety and health in the first water supply system, with Safe and reliable, health and environmental protection, affordable and so on. Has been domestic and international engineering practice proved to be the best overall performance of the water supply system, new, energy-saving and environmentally friendly one of the pipe is also a very competitive water supply pipe, will improve the water quality, improve people’s living standards Comparable to the role.
In the construction of water supply system, as a result of galvanized steel has ended a hundred years of glorious history, a variety of new plastic pipe and the rapid development of composite pipe, but the various pipes also exist to some extent inadequate, far from fully adapted to the water supply pipe The needs of the Department and the state of drinking water and related water quality requirements. Therefore, the experts predict: building water supply pipe will eventually return to the era of metal pipe. According to the application experience abroad, in the metal tube in the thin-walled stainless steel pipe is one of the best overall performance.
Thin-walled stainless steel pipe, domestic in the 20th century, the late 90s began production, use, is now emerging in the field of pipe newborn family, has been widely used in building water supply and drinking water pipes.
Thin-walled stainless steel tube durable, has been recognized by the engineering community, and the parties concerned are from the wall thickness reduction, lower prices in order to facilitate further promotion. Especially small diameter stainless steel pipe, the price is not high, so supporting the connection method, the reliability of pipe fittings and the price is to determine its development of the main factors. Domestic in Sichuan, Guangdong, Zhejiang, Jiangsu and other places have been developed independently of the connecting technology and pipe fittings, is a very promising pipe. Ministry of Construction and relevant departments also attach great importance to this new pipe, according to the China Technology Market Management Promotion Center, the National Bureau of the word  Document 71, on the promotion and application of high-diameter ratio of high-precision stainless steel, high pressure water supply and supporting Pipe and special technology, “the notice was informed that the thin-walled stainless steel tube technology and product application to promote the application of modern Chinese building grade, improve and protect the water quality is of great significance.
At the same time, the Ministry of Construction attaches great importance to the promotion of thin-walled stainless steel pipe applications. “Thin-walled stainless steel water pipes,” the industry standard was released in 2001 implementation. The relevant technical specifications of pipeline engineering and installation Atlas, the Ministry of Construction has issued a document, is responsible for the preparation by the Tongji University. At present, Sichuan, Guangdong, Zhejiang, Jiangsu and other places have professional manufacturers of thin-walled stainless steel pipe, the product has become mature, and therefore, the time has come to promote the application.
① building water supply pipe demand
According to the “Ninth Five-Year Plan” and “Outline of 2010”, the annual demand of pipe is between 500,000 and 600,000 km, and the demand for hot and cold water pipes is 400,000 km in residential buildings. Some people think that the development of stainless steel pipes, to improve the grade of modern urban construction, is of great significance.
② pipeline direct drinking water has developed rapidly
With the development of the national economy, direct drinking water pipeline in the domestic Beijing, Shenzhen, Shanghai, Chongqing and other cities have developed rapidly, economically developed medium-sized cities are actively planning to catch up. In the direct drinking water, stainless steel piping is undoubtedly second to none. The current domestic on the grade of the hotel, public places have been configured or in the allocation of direct drinking water pipes.
③ domestic import substitution promising
In order to promote stainless steel tube, China from the 20th century since the 90s from the reduction of wall thickness and reduce costs to address the “high-diameter ratio of high-precision than the” thin-walled stainless steel tube technology, stainless steel tube to promote the application of rapid development . A pipeline to be able to fully promote the application, and ultimately localization. When the domestic part of the manufacturers have been part of the production and further development of thin-walled stainless steel pipe and tube capacity.
Stainless steel pipe connections are diverse, common types of pipe fittings are compression type, compression type, live type, push type, push type, socket type welding, union type flange connection, welding and welding and traditional connection phase Combined with the derived series connection. These connections, according to its different principles, its scope of application is also different, but most are easy to install, solid and reliable. The use of the connection seal or gasket material, mostly selected in line with national standards for silicone rubber, nitrile rubber and EPDM rubber, etc., eliminating the user’s worries.
Press-fitting connection step
1, broken pipe: according to the required length cut off the pipe, broken pipe, not too much force to prevent loss of pipe round.
2, remove the burr: pipe cut off, the burr should be removed clean, so as not to cut the seal ring.
3, marking the mark: In order to make the pipe completely into the pipe socket, must be inserted in the pipe end of the length of the line marked.
4, the assembly: the ring should be installed correctly in the tube U-groove, the tube into the pipe socket, waiting for crimp.
5, crimp: crimp, the tube parts of the convex concave groove on the mold, jaw and tube axis to maintain vertical.
6, check: crimping is complete, the use of special gauge to check the size of crimping.
① with the international chemical symbols and symbols to represent the chemical composition of the country, with the Arabic alphabet to indicate the content of ingredients:
Such as: China, Russia 12CrNi3A
② with a fixed number of digits to indicate steel series or figures; such as: the United States, Japan, 300 Series, 400 Series, 200 Series;
③ with the Latin alphabet and order composition number, only that use.
① the use of element symbols
② use, Pinyin, open hearth steel: P, boiling steel: F, killed steel: B, A class steel: A, T8: special 8,
◆ alloy steel, spring steel, such as: 20CrMnTi 60SiMn, (with a very few that C content)
◆ stainless steel, alloy tool steel (with a few thousandths that C content), such as: 1Cr18Ni9 thousandths
0.1% C), stainless steel C ≤ 0.08% such as 0Cr18Ni9, ultra-low carbon C ≤ 0.03% such as 0Cr17Ni13Mo
American Iron and Steel Institute is a three-digit to mark a variety of standard-grade malleable stainless steel. among them:
① austenitic stainless steel with 200 and 300 series of digital marked, for example, some of the more common austenitic stainless steel
Is labeled 201, 304, 316, and 310,
② ferrite and martensitic stainless steel with 400 series of digital representation. Ferritic stainless steel is marked with 430 and 446, martensitic stainless steel is 410,420 and 440C for the mark, biphasic (austenite – ferrite),
③ stainless steel, precipitation hardening stainless steel and iron content of less than 50% of the high alloy is usually the name of the patent or trade name.
① national standard GB ② industry standard YB ③ local standards ④ enterprise standard Q / CB
① Product standard ② Packaging standard ③ Method standard ④ Basic standard
4-3 standard level (in three):
Y – class: the international advanced level I – level: the international general level H – level: the domestic advanced level
GB1220-84 stainless steel bar (I grade) GB4241-84 stainless steel welding plate Park (H level)
GB4356-84 stainless steel welded plate garden (Class I) GB1270-80 stainless steel pipe (Class I)
GB12771-91 stainless steel pipe (Y level) GB3280-84 stainless steel cold plate (Class I)
GB4237-84 stainless steel hot plate (Class I) GB4239-91 stainless steel cold zone (Class I)
200 series D7S
Product Description: D7S nickel content of about 2.5%, slightly lower than the nickel content of D11, the price is relatively low. 1% nickel content of stainless steel to a certain extent, will be the key to the supply of D7S market, so the competitiveness of the integrated high quality stainless steel with high utilization rate will also be an important part of the sales plan.
Application areas: new products target markets such as stainless steel kitchen equipment and other areas of stainless steel pipe market sales plan.
Product Description: The tensile strength of the material 980 ~ 1180MPa, the maximum working temperature up to 90 ℃.
Fields of application: Pipes for harsh subsea environments
Product Description: Super (super) critical unit is the basis of modern power generation equipment and energy saving. In super (super) critical boiler important pressure components, the highest temperature, the most difficult parts of the work environment is the superheater and reheater. Previously, China’s domestic use of all such materials imported from abroad, while only 10 international steel manufacturers capacity is limited, such material gap is large, import prices are expensive, and procurement difficulties, in short supply, seriously affected China’s ultra- Production of Supercritical Boiler and Development of Electric Energy. China’s current demand for power plant boiler tubes is about 30,000 tons per year, and with the ultra (super) critical power generation technology continues to increase, the demand has expanded each year. Several large domestic enterprises have invested a lot of manpower, financial resources, is committed to the development of such products, production, and has made considerable achievements. On the one hand for the country’s power industry has made its own contribution to the development, at the same time, but also to the enterprise has brought considerable economic benefits.
Application areas: power plant boiler industry, mainly superheater and reheater and other key parts of the high temperature section.
Air conditioning use
Product Description: The product has high processing performance, weight can be reduced by 60% than copper, copper prices lower than the copper can be used as a substitute.
Application: Air conditioning industry
Duplex stainless steel
Product Description: This stainless steel in urea – carbamate solution has good corrosion resistance, in the chloride environment has a high resistance to stress corrosion cracking. At the same time, the dual-phase stainless steel mechanical properties, can be applied to higher safety requirements of the plant construction.
Application areas: chemical industry, construction industry.
Steel pipe dimensions and tolerances
±1.5%，smallest tolerance±0.75 mm
±1.0%。smallest tolerance±0.50 mm
±0.75%．smallest tolerance±0.30 mm
±0.50%。smallest tolerance±0.10 mm
Stainless steel features
Resistant to air, steam, water and other weak corrosive media and acid, alkali, salt and other corrosive chemical etching medium of steel. Also known as stainless steel acid. Practical application, often corrosion-resistant medium corrosion of steel is called stainless steel, and corrosion-resistant chemical medium steel called acid-resistant steel. Due to the difference in chemical composition between the two, the former is not necessarily resistant to chemical corrosion, while the latter generally have a stainless steel. The corrosion resistance of stainless steel depends on the alloying elements contained in the steel. Chromium is the basic element to obtain corrosion resistance of stainless steel, when the chromium content of steel to 1.2%, chromium and corrosive media in the role of oxygen in the steel surface to form a thin layer of oxide film (from the passive film) , Can prevent further corrosion of steel matrix. In addition to chromium, the commonly used alloying elements are nickel, molybdenum, titanium, niobium, copper, nitrogen, etc., to meet the various uses of stainless steel on the organization and performance requirements.
Classification of stainless steel
Stainless steel is usually divided according to the matrix structure:
⒈ ferritic stainless steel. Chromium 12% to 30%. The corrosion resistance, toughness and weldability with the increase of chromium content increased, resistance to chloride stress corrosion resistance is better than other types of stainless steel.
⒉ austenitic stainless steel. Containing more than 18% chromium, also contains about 8% nickel and a small amount of molybdenum, titanium, nitrogen and other elements. Comprehensive performance, can be resistant to a variety of media corrosion.
⒊ austenitic – ferritic duplex stainless steel. Both the advantages of austenitic and ferritic stainless steel, and has a superplastic.
⒋ martensitic stainless steel. High strength, but poor plasticity and weldability.
⒌ precipitation hardening stainless steel. Has good formability and good weldability, can be used as ultra-high strength materials in the nuclear industry, aviation and aerospace industry applications.
(SUS400), Cr-Ni system (SUS300), Cr-Mn-Ni (SUS200) and precipitation hardening system (SUS600).
Stainless steel corrosion reasons
All the metal reacts with oxygen in the atmosphere, forming an oxide film on the surface. Unfortunately, the formation of iron oxide on ordinary carbon steel continues to oxidize, so that corrosion continues to expand, and ultimately the formation of holes. The surface of the carbon steel can be secured by painting with a paint or an oxidation-resistant metal (e.g., zinc, nickel and chromium), but, as is well known, this protection is only a thin film. If the protective layer is destroyed, the following steel will begin to rust.
Corrosion resistance of stainless steel depends on chromium, but because chromium is one of the components of steel, so the protection methods are different.
When the addition of chromium reaches 10.5%, the atmospheric corrosion resistance of the steel is remarkably increased, but when the chromium content is higher, the corrosion resistance can be improved, but it is not obvious. The reason is that when chromium is used to alloy the steel, the type of surface oxide is changed to a surface oxide similar to that formed on pure chromium metal. This tightly adhered chromium-rich oxide protects the surface and prevents further oxidation. This oxide layer is very thin, through which you can see the natural luster of the steel surface, so that stainless steel has a unique surface. Moreover, if the damage to the surface, the exposed surface of the steel and the atmosphere will be self-repair, re-formation of this “passive film” to continue to play a protective role.
Therefore, all the stainless steel has a common characteristic, that is, chromium content of 10.5% or more.
There are usually only six types of steel associated with building construction applications. They all contain 17 to 22% chromium, and the preferred steels also contain nickel. The addition of molybdenum can further improve atmospheric corrosion, particularly in chloride-containing atmosphere.
Stainless steel resistant to atmospheric corrosion
Experience has shown that the extent of atmospheric corrosion varies from region to region. For ease of description, it is recommended that the regions be divided into four categories: rural, urban, industrial and coastal.
The villages are basically pollution-free areas. The area has a low population density and is only a non-polluting industry.
The city is a typical residential, commercial and light industrial area with mild pollution, such as traffic pollution.
Industrial areas for heavy industry caused by air pollution in the region. Contamination may be due to the formation of fuel gas, such as sulfur and nitrogen oxides, or chemical plants or other gases released by processing plants. Particles suspended in the air, such as dust or iron oxide produced during the production of iron and steel, also increase corrosion.
Coastal areas usually refer to areas within a mile of the seashore. However, the oceanic atmosphere can spread inland depth, especially in the island, the prevailing wind from the ocean, and the climate is bad. For example, the British climate conditions is the case, so the whole country belongs to the coastal area. If the wind mixed with marine fog, especially due to evaporation caused by salt deposition and accumulation, coupled with less rain, not often washed away by the rain, the coastal areas of the conditions even more unfavorable. If there is industrial pollution, then corrosive even greater.
Research in the United States, the United Kingdom, France, Italy, Sweden, and Australia has identified the effects of these regions on atmospheric corrosion resistance of various stainless steels. The content is briefly described in the Architectural Fact Sheet published by NiIDI. The tables in this book help designers choose the best cost-effective stainless steel for each area.
When making selections, it is important to determine whether there are local factors that affect the use of the on-site environment. For example, stainless steel is used below the factory chimney, near the air conditioning exhaust baffle or near the scrap steel field, there will be non-general conditions.
Stainless steel maintenance and cleaning
As with other materials exposed to the atmosphere, stainless steel is also dirty. Future lectures will analyze design factors that impact maintenance and clean-up costs. However, there is a correlation between rain erosion, manual flushing, and dirty surfaces.
The effect of rain erosion was determined by placing the same slab directly in the atmosphere and in a shed. The effect of manual flushing was determined by manually scrubbing the right side of each panel with soapy water sponge every six months. As a result, it was found that dust and silt removal by rain washing and manual scrubbing had a favorable effect on the surface condition as compared with a slat placed in a shed and a place not washed. But also found that the status of surface processing has an impact on the smooth surface of the slab than the rough surface of the slab effect is better.
So the scrubbing interval by a variety of factors, the main influencing factor is the required aesthetic standards. Although many stainless steel curtain walls only in the Cabo rinse, but, in general, for external stainless steel scrub twice a year.
Typical Uses of Stainless Steel
Most of the requirements are to maintain the original appearance of the building for a long time. In determining the type of stainless steel to be selected, the main consideration is the aesthetic standards required, the location of the corrosive atmosphere and the cleaning system to be used.
However, other applications are increasingly looking for structural integrity or impermeability. Such as roofs and side walls of industrial buildings. In these applications, the owner of the construction cost may be more important than the aesthetic, the surface is not very clean can be.
The use of 430 stainless steel in a dry indoor environment is quite good. However, in the countryside and the city in order to maintain its appearance in the outdoors, you need regular cleaning. In polluted industrial areas and coastal areas, the surface will be very dirty, or even rust. But to get the aesthetic effect of outdoor environment, you need to use nickel-containing stainless steel. Therefore, 304 stainless steel is widely used in curtain wall, side wall, roof and other construction purposes, but in the corrosive serious industrial or marine atmosphere, the best use of 316 stainless steel.
The advantages of using stainless steel in structural applications have been well recognized. Several design guidelines include 304 and 316 stainless steel. Because “duplex” stainless steel 2205 has good atmospheric corrosion resistance and high tensile strength and elastic limit strength of integration, so the European guidelines also include the steel.
Stainless steel product shape
In fact, the stainless steel is the standard metal shape and size of the production of manufacturing, but there are many special shapes. The most commonly used products are made of sheet and strip, and special products are also produced with plate, for example, hot rolled structural steel and extruded structural steel. But also round, oval, square, rectangular and hexagonal pipe or seamless steel pipe and other forms of products, including profiles, bar, wire and castings.
As will be discussed later, in order to meet the aesthetic requirements of the architects, a variety of different commercial surface processes have been developed. For example, the surface may be highly reflective or matte; it may be smooth, polished or embossed; it may be colored, colored, electroplated, or etched on a stainless steel surface to satisfy a designer & apos; Of the various requirements.
It is easy to keep the surface state. Only occasional flushing can remove dust. As a result of the good corrosion resistance, it is also possible to easily remove the contamination of the surface by painting or the like.
Hydraulic fluid pressure test with stainless steel pipe pressure formula (GB / T1277-2008)
P = 2RS / D
Where: P-test pressure, MPa;
R-stress, take yield point 50%, MPa;
S-pipe nominal wall thickness, mm;
D Nominal outer diameter of steel pipe, mm.
W = (outside diameter – wall thickness) × wall thickness × 0.02491 = KG / M (weight per meter)
Stainless steel pipe application and maintenance:
Stainless steel pipe should be used in the time of attention, to avoid contact with the corrosive high water and gas.
Stainless steel pipe implementation standards
stainless steel pipe
Stainless steel tube (2 photos)
GB2270-80 Stainless steel seamless steel tubes GB / T14976-94 Stainless steel tubes for fluid delivery
Stainless steel tubes for structural purposes GB / T14975-2002
Stainless steel tubes for the conveyance of fluid GB / T14976-2002
GB13296-91 boiler tubes, heat exchangers with stainless steel tube
(GJB2608-96) (YB676-73) Aerospace structural pipe, thick-walled seamless steel pipe
(GJB2296-95) (YB678-71) Aerospace stainless steel tubes
(YB / T679-97) (YB679-71) Aviation 18A hollow rivet thin-walled seamless steel pipe
(GJB2609-96) (YB680-71) Aerospace structural tubes, thin-walled seamless steel tubes
(YB / T681-97) (YB681-71) Aerospace Pipe 20A Thin-walled seamless steel pipe
GB3090-82 small diameter stainless steel pipe
Seamless steel tubes for high – pressure boiler GB / T
Low and medium pressure boiler tubes
GB3089-92 stainless steel acid-resistant thin-walled seamless steel tubes
Petroleum cracking tubes
Standard Specification for Ferritic and Austenitic Alloy Tubes for Boilers, Heat Exchangers
Standard Specification for General Purpose Austenitic Stainless Steel Pipe and Welded
Standard Specification for Austenitic Stainless Steel Seamless Steel Pipe Welded
Standard Specification for General Requirements for Carbon Steel, Ferritic and Austenitic Alloy Steel Tubes
Standard Specification for General Requirements for Ferritic and Alloy Steels for Special Purposes
ASTM A789 General Requirements Carbon austenitic stainless steel seamless tubes and welded steel tubes
Stainless steel tubes for mechanical construction. JIS G3456
Standard Specification for Stainless Steel Pipes for Use in General Pipes JIS G3448 –
Stainless steel tubes for piping JIS G3459
Stainless steel tubes for boilers and heat exchangers JIS G3463-88
Q / HYAD chemical seamless steel pipe
(0Cr18NI11T) Q / HYAD Cr18Ni5MO3Si2 Duplex Stainless Steel Seamless Steel Tube
Mainly used in stainless steel exhaust system, accounting for the total consumption of stainless steel over 1/2, 80% of ferritic stainless steel. Exhaust gas generated by the car engine through the exhaust pipe into the air, the front tube, hose, converter, the central tube out of the final from the muffler. Exhaust system commonly used steel 409L, 436L and so on. Automobile muffler mainly use stainless steel pipe. It is estimated that the use of automotive stainless steel pipe accounted for the entire downstream of the stainless steel pipe consumption of about 1.5%, while the use of stainless steel seamless pipe and pipe ratio of about 2: 1
The petrochemical industry includes the fertilizer industry
The demand for stainless steel pipe is very great. The industry mainly uses stainless steel seamless pipe. The specification includes: 304,321,316,316L, 347,317L, etc. The outside diameter is about ¢ 18- ¢ 610, the wall thickness is between 6mm-50mm (Generally selected specifications in the Φ159mm above the low-pressure pipeline), the specific application areas: furnace tubes, material pipes, heat exchangers and so on.
Water and gas and other fluid delivery
Stainless steel pipe and its water supply equipment, is the world’s most advanced basic water purification materials, its anti-corrosion performance, cast iron pipe, carbon steel pipe, plastic pipe, can not be compared.
Water preparation, storage, transportation, purification, regeneration, water desalination and other water industry the best selection. The annual demand of about 25,000 tons.
Equipment manufacturing and maintenance
Annual consumption of more than 20,000 tons of stainless steel tube. This kind of profession mainly uses the hygiene or the antibacterial grade stainless steel tube. Imported SUS304, 316L production of health seamless tube, to meet the food, bio-pharmaceutical fields of various media special requirements. Antibacterial stainless steel has the advantages of stainless steel and good antibacterial properties, in the kitchen equipment, food industry table and utensils, medical equipment, daily utensils and hanging towel racks, refrigerators, bays and other areas of increasing demand.
Suction tube, especially for
For solids such as powders, detritus and granular objects
For gaseous media
For industrial dust and suction equipment, air conditioning and ventilation systems
As a durable protection tube to use
Used in the manufacture of mechanical parts and engineering structures
Used for a variety of conventional weapons, barrel, shells
If the human living space than the human body, the living space laying the various channels is like blood vessels and nerves. Transport high-quality drinking water, pipe fittings of choice is essential. In this regard, I recently visited the China Association of Stainless Steel Branch of the relevant experts.
Experts believe that most of today’s construction water pipes are concealed works and pipeline wells works, if the pipe selection is not appropriate, according to experts estimated that the value of the water pipe material itself will cause investors 10 to 20 times the economic losses. Another pipe selection is also a barometer of water industry development and progress. Water supply pipe five selection principles: safety and reliability, economy, health, energy saving, sustainable development, which is the green tube of several major characteristics, only to be able to meet these principles is the real pipe is really good pipe.
The most commonly used stainless steel in the water industry is 304 and 316 stainless steel, which meet most of the water treatment and transport conditions.
Product development history
Mass production of stainless steel with electric arc furnace in China in 1949, after the early production of Cr13 martensitic stainless steel, master the production technology, mass production of 18-8 Cr-Ni austenitic steel, such as 1Cr18Ni9Ti, then began in 1952 . Subsequently, in order to meet the needs of the domestic chemical industry development, and began to produce with Mo2% -3% 1Cr18Ni12Mo2Ti and 1Cr18Ni12Mo3Ti and so on. In order to conserve valuable elements of nickel, since 1959 to imitate Mn, N on behalf of the Ni 1Cr17Mn6Ni5N and 1Cr18Mn8Ni5N, AISI 204 steel in the year to add Mo2% -3%, developed 1Cr18Mn10Ni5Mo3N (204 + Mo), for the full cycle Urea production plant to replace 1Cr18Ni12Mo2Ti. From the late 1950s to the early 1960s, industrial trial production of 1Cr17Ti, 1Cr17Mo2Ti and 1Cr25Mo3Ti and other non-nickel ferrite stainless steel and began to study the fuming nitric acid corrosion of high silicon stainless steel 1Cr17Ni14Si4ALTi (equivalent to the Soviet Union grade ЭИ654), this steel actually Is an α + γ duplex stainless steel. 60 years, due to the domestic chemical industry, aerospace, aviation, atomic energy and other industrial development needs and the use of electric furnace oxygen steelmaking technology, a large number of new steel, such as 17-4PH, 17-7PH, PH15-7Mo precipitation hardening stainless steel, C ≤ 0.03% of ultra-low carbon stainless steel 00Cr18Ni10, 00Cr18Ni14Mo2, 00Cr18Ni14Mo3 and Ni-free Cr-Mn-N stainless steel 1Cr18Mn14Mo2N (A4) have been successfully developed and put into production. Since the 1970s, in order to solve the chloride and stress corrosion problems of 18-8 Cr-Ni steel in the chemical and atomic energy industries, some α + γCr-Ni duplex stainless steel have been developed and put into production and application. The main steel grades There are 1Cr21Ni5Ti, 00Cr26Ni6Ti, 00Cr26Ni7Mo2Ti, 00Cr18Ni5Mo3Si2 (3RE60) and 00Cr18Ni6Mo3Si2Nb and so on.
00Cr18Ni6Mo3Si2Nb is to solve the Swedish brand 3RE60 prone to single-phase ferrite welding after welding, resulting in decreased corrosion resistance and toughness and the development of N, Nb α + γ duplex stainless steel. In the 1980s, the second generation α + γ duplex stainless steels containing N, such as 00Cr22Ni5Mo2N, 00Cr25Ni6Mo3N and 00Cr25Ni7Mo3WCuN, were developed and imitated in order to solve the localized corrosion damage such as pitting corrosion and crevice corrosion of chloride. Not only the double phase Stainless steel to form a series, but also an in-depth study of their organization and performance and N in duplex stainless steel in the mechanism of action. Since the 1970s, China’s stainless steel materials research work in other important progress: the development of high strength and ultra-high strength martensitic aging stainless steel and put into industrial trial and application; the use of vacuum induction furnace, vacuum electron beam furnace and vacuum consumption furnace Smelting and mass production of C + N ≤ 150-250ppm of high-purity ferritic stainless steel 00Cr18Mo2, 00Cr26Mo1 and 00Cr30Mo2; Mo content of ≥ 4.5% of high Mo and high MoN-containing Cr-Ni austenitic stainless steel, such as the successful development 00Cr20Ni25Mo4 In the solution of concentrated nitric acid corrosion and solid solution intergranular corrosion, developed 00Cr25Ni20Nb and several kinds of ultra-low carbon high silicon stainless steel, which has been widely used in the field of chemical engineering, petrochemical industry and marine development. In recent years, it has been widely applied in the field of chemical, petrochemical and marine development, such as .5Cu, 00Cr18Ni18Mo5 (N), 00Cr25Ni25Mo5N, Since the 1980s, ultra-low carbon steel and phosphorus content and α-phase amount of strict control of urea-grade stainless steel 00Cr18Ni14Mo2 and 00Cr25Ni22Mo2N two grades developed, their plates, tubes, bars, forgings and welding materials are large and medium Urea and so on. Some special steel mills have built furnace refining facilities such as AOD (Argon Oxygen Refining Furnace), VOD (Vacuum Oxygen Refining Furnace) and so on, and have been put into production. Stainless steel smelting technology to a new level. It not only makes the production of low-carbon, ultra-low carbon stainless steel easy, but also to improve the inherent quality of stainless steel, cost reduction. As a result of Ti 18-8 Cr-Ni austenitic steel there are a series of shortcomings, the United States, Japan and other advanced industrial countries as early as 60 years has been achieved by the Ti-containing stainless steel to the widespread use of low-carbon, ultra-low carbon stainless steel Production and application of low-carbon, ultra-low carbon stainless steel, and made some encouraging progress, such as the end of 1988 China’s low carbon, ultra-low carbon 18-8 stainless steel production Accounting for about 10% of China’s stainless steel production. However, compared with the advanced countries of stainless steel production and application (such as Japan, the United States and other countries with 18-8 Cr-Ni steel production accounts for only about 1.5% of stainless steel), there is still a big gap. In the 1980s, China also developed a nitrogen-controlled (N 0.05% -0.10%) and nitrogen alloyed (N> 0.10%) Cr-Ni austenitic stainless steel development work. Experiments show that nitrogen in Cr-Ni austenitic stainless steel and duplex stainless steel is an invaluable and very beneficial alloying elements. Strengthening the role of nitrogen, reducing intergranular corrosion susceptibility of steel to improve the corrosion resistance of steel, in particular, to improve the resistance of steel pitting corrosion and other aspects of the mechanism, ongoing in-depth research. Several kinds of nitrogen and nitrogen alloyed Cr-Ni austenitic stainless steel has been combined with the project need to put into mass production and application.
Usually stainless steel pipe has three characteristics: weldability, corrosion resistance, polishing performance (BQ)
The use of different products on the welding performance requirements are also different. A class of tableware on the welding performance is generally not required, even including some pot enterprises. But the vast majority of products require raw materials, welding performance, such as two types of tableware, insulation Cup, pipe, water heaters, drinking fountains and so on.
The majority of stainless steel products require good corrosion resistance, stainless steel tube like a tableware, kitchenware, water heaters, water dispensers, some foreign businessmen also do corrosion resistance test: NACL water solution to boiling, a period of time (Note: when the product is polished, because the emery cloth or the sand paper contains the Fe ingredient, will cause the test the surface to appear the rust spot), will not be able to have the corrosive effect,
Polishing performance (BQ)
Stainless steel products are generally polished in the production process, only a few products such as water heaters, drinking fountains, etc. do not need polishing. Therefore, the polishing performance of the raw material is required to be good. Polishing performance of the factors that affect the following points:
① raw surface defects. Such as scratches, pitting, acid pickling.
② stainless steel pipe material quality problems. Hardness is too low, polishing is not easy to throw bright (BQ is not good), and hardness is too low, in the deep drawing surface prone to orange peel phenomenon, thus affecting the BQ. BQ hardness is relatively high.
③ After deep drawing products, the deformation of the surface area will be a great little black spots and RIDGING, thus affecting the BQ.
The stainless steel pipe can be divided into Cr series (400 series), Cr-Ni series (300 series), Cr-Mn-Ni series (200 series) and precipitation hardening series (600 series). 200 Series – Chromium – Nickel – Manganese Austenitic Stainless Steel 300 Series – Chromium – Nickel Austenitic Stainless Steel.
301 —– ductility is good, for molding products. It can also be rapidly hardened by machining. Weldability is good. Wear resistance and fatigue strength is better than 304 stainless steel.
302 —– corrosion resistance with 304, due to relatively high carbon intensity and better.
303 —– by adding a small amount of sulfur, phosphorus makes it more than 304 cutting.
304 —– that is 18/8 stainless steel. GB grade 0Cr18Ni9. 309 – better than the 304 temperature resistance.
316 —– Following 304, the second most widely used steel, mainly for the food industry, the pharmaceutical industry and surgical equipment, add molybdenum elements to obtain a special structure of anti-corrosion. As compared with the 304 stainless steel tube which has a better resistance to chloride corrosion and thus also as “marine steel” to use. SS316 is usually used for nuclear fuel recovery devices. 18/10-grade stainless steel pipe is usually also meet this application level.
Model 321 – except for the addition of titanium to reduce the risk of corrosion of the material welds other than 304.
400 series – ferritic and martensitic stainless steel.
408 – good heat resistance, weak corrosion resistance, 11% Cr, 8% Ni.
409 – The most inexpensive model (Anglo-American), usually used for automobile exhaust pipe, is a ferritic stainless steel (chrome steel).
410-martensite (high-strength chrome steel), good wear resistance, corrosion resistance is poor.
416 – Added sulfur improves the processability of the material.
420 – “cutting-grade” martensitic steel, similar to Brinell high-chromium steel the earliest stainless steel. Also used in surgical tools, can do very bright.
430 – ferritic stainless steel, decorative, for example, for automotive accessories. Good formability, but the temperature and corrosion resistance to be worse.
440 – high-strength cutting tool steel, carbon is slightly higher, after appropriate heat treatment can be obtained after a higher yield strength, hardness can reach 58HRC, belonging to the hardest of the list of stainless steel. The most common application is the “razor blade”. There are three commonly used models: 440A, 440B, 440C, in addition to 440F (easy processing type).
500 series – heat-resistant chromium alloy steel.
600 series – martensitic precipitation hardening stainless steel tube.
The development of stainless steel tube industry to go through the introduction period, growth, maturity and recession. Market development of the same law, the stainless steel tube industry should be spotted the opportunity, waiting in the wings. Stainless steel market has entered the stage of brand competition, market competition is increasing. Stainless steel tube in order to multiply market share, must be based on market conditions to develop new strategies to open up market segments. China’s stainless steel market has been from the product, channel competition, into the brand, marketing, competitive stage of development. Brand, marketing, competitive stage, do a good job market segments become the key to winning the stainless steel tube competition. Many well-done stainless steel pipe enterprises are focused on doing a good job market segments. Stainless steel tube focus on the introduction of ecological, environmentally friendly products, open up new market segments. With the stainless steel tube market continues to mature and market competition continues to intensify, the future industry is “the market segment who have the world.” Segment market will become a new wrestling field of stainless steel tube. The following is a brief overview of the fluid under the stainless steel tube and manufacturing methods.
Overview of stainless steel tubes for fluids
A stainless steel tube for fluid is a hollow section with no welds from beginning to end. Stainless steel pipe products with round steel and other solid steel, bending strength in the same bending, the lighter weight, is an economic section of steel, is widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipe, car drive shaft , Bicycle frames and steel scaffolds used in construction. The use of stainless steel pipe manufacturing ring parts, can improve material utilization, simplify manufacturing processes, save materials and processing time, such as rolling bearing rings, Jacket sets, widely used to manufacture stainless steel tube.
Stainless steel tube or a variety of conventional weapons indispensable materials, barrel, barrel and so on to the stainless steel tube to manufacture. Stainless steel tube products according to the different cross-sectional shape can be divided into round tube and shaped tube. In addition, the circular cross-section to withstand internal or external radial stainless steel tube pressure, the force is more uniform, therefore, the vast majority of stainless steel tube is a round tube.
Method for manufacturing stainless steel tube for fluid
① general boiler tube temperature at 450 ℃ below, the main domestic pipe with 10, 20, carbon steel hot-rolled pipe or cold drawn tube manufacturing.
② high-pressure boiler tubes are often used in high temperature and high pressure conditions, the pipe in the high-temperature flue gas and water vapor under the action of oxidation and corrosion will occur. Requirements of stainless steel tube products with high strength, high resistance to oxidation and corrosion resistance, and good tissue stability.
In this case,
① general boiler tubes are mainly used to manufacture water wall tube, boiling water pipes, superheated steam pipe, locomotive boiler with superheated steam pipe, large and small smoke pipe and arch brick tube.
② high pressure boiler tube is mainly used to manufacture high pressure and super high pressure boiler superheater tube, reheater tube, airway, the main steam pipe.
However, the tube also has some limitations, such as bending in the plane by the conditions, the tube is not as square, rectangular tube bending strength, a number of farm machinery with skeleton, Gangmu furniture on the common side, rectangular tube. According to different uses need to have other cross-section shape of the shaped stainless steel tube.
Commonly used: Material 201/304 / 304L / (diameter – wall thickness) x Wall thickness x0.02491x Length = Weight (kg)
Material 316 / 316L (Diameter – Wall Thickness) x Wall Thickness x0.02513x Length = Weight (kg)
Unit: kg / m
Sulfuric acid equipment applications
Sulfuric acid is an important basic chemical raw materials, its output is often a measure of a country’s industrial development level of the symbol. Acid-resistant stainless steel pipes are usually selected for equipment for producing acid and for tanks and containers containing acid. Sulfuric acid is an oxo acid, but sulfuric acid and sulfuric acid in the medium concentration of oxidation is weak, so they are reductive acid. The concentrated sulfuric acid, especially the hot concentrated sulfuric acid is highly oxidizing, and therefore belong to the oxidizing acid. Because of this characteristic of sulfuric acid, in the selection of sulfuric acid-resistant stainless steel tube, with sulfuric acid concentration, temperature, different grades selected.
Dilute sulfuric acid, medium sulfuric acid is the reduction of count, you can choose 316 stainless steel tube, 316L stainless steel tube, 316Ti stainless steel tube containing molybdenum in 2% to 3% of the stainless steel tube. Molybdenum-free stainless steel tube 18-8 Cr-N austenitic stainless steel, due to intolerance of dilute sulfuric acid, medium sulfuric acid corrosion, it can not be used for sulfuric acid corrosion. When the high molybdenum content (Mo ≥ 4%), the stainless steel pipe corrosion resistance will be further improved. Chromium-nickel austenitic stainless steel containing molybdenum, copper and silicon (3% ~ 4%) and duplex stainless steel are more resistant to sulfuric acid.
Concentration of 90% to 98% concentrated sulfuric acid in high temperature, according to the use of temperature and concentration, the choice of silicon about 6% of stainless steel can achieve satisfactory results, such as 022Cr17Ni17Si6, 022Cr18Ni20Si6MoCu.
In the manufacture of pickling, synthetic rubber, artificial silk dipping tank contact with sulfuric acid equipment, optional 06Cr18Ni18Mo2Cu2Ti stainless steel tube. In the manufacture of sulfuric acid-resistant pipes, pumps, valves, towers and containers and other equipment and components, the choice of 06Cr12Ni25Mo3Cu3Si2N stainless steel tube.