About stainless steel, stainless steel introduction and common sense

Stainless steel (stainless steelcompany) is the abbreviation of acid-resistant steel, resistance to air, steam, water and other weak corrosive medium or stainless steel is known as the rust resistance of the chemical medium corrosion (acid, alkali, salt and other chemical etching) of the steel is called acid-resistant steels. Due to the differences in chemical composition of their corrosion resistance is different, ordinary stainless steel is generally not resistant to chemical medium corrosion, and acid-resistant steel is generally stainless.

Historical origins

Harry Brearley, a renowned metallurgical scientist at the University of Shffield, Henry Brelly, invented stainless steel in the early 20th century. The invention and use of stainless steel goes back to the First World War. British scientist Henry Lie Brelly is commissioned by the British government military arsenal to study the improvement of weapons. At that time, the soldier's rifle barrel was very easy to wear, and Brelly wanted to invent an alloy steel that was not easily worn. Brelly invented the stainless steel in 1916 to obtain British patent and began to mass production, thus, from the garbage heap accidentally found in the stainless steel will be swept around the world, Henry Brelly also known as "the father of stainless steel."

Main categories

Stainless steel is often divided into the organization: Martensitic Steel, ferritic Steel, austenitic steel, austenitic-ferrite (duplex) stainless steel and precipitation hardening stainless steel. In addition, can be divided into: chromium stainless steel, chromium-nickel stainless steel and chromium manganese nitrogen stainless steel.

1. ferritic stainless steel: chromium-containing 12%~30%. Its corrosion resistance, toughness and weldability increase with the increase of chromium content, and the corrosion resistance of chloride is superior to other kinds of stainless steel. Belong to this kind of have Crl7, Cr17mo2ti, Cr25,cr25mo3ti, Cr28 etc. Ferritic stainless steel Because of high chromium content, corrosion resistance and antioxidant properties are better, but the mechanical properties and process performance is poor, many for the resistance of the acid-resistant structure and the use of iron oxide. This kind of steel can resist the corrosion of atmosphere, nitric acid and brine solution, and has the characteristics of high temperature oxidation resistance, small thermal expansion coefficient and so on, it is used in nitric acid and food factory equipment, also can make the parts that work at high temperature, such as gas turbine parts.

2. austenitic stainless steel: containing more than 18% chromium, but also contains about 8% nickel and a small amount of molybdenum, titanium, nitrogen and other elements. Good comprehensive performance, can withstand a variety of media corrosion. Austenitic stainless Steel's common grades are 1cr18ni9, 0cr19ni9 and so on. The wc<0.08% of 0cr19ni9 steel is labeled "0" in steel. This type of steel contains a large number of NI and CR, so that the steel at room temperature in the austenite state. This type of steel has good plasticity, toughness, weldability and corrosion resistance, in both oxidizing and reducing medium corrosion resistance is good, used to make acid-proof equipment, such as corrosion-resistant containers and equipment lining, conveying pipelines, nitric acid equipment parts. Austenitic stainless steel is generally treated with solid solution, the steel heated to 1050~1150℃, and then water-cooled to obtain single-phase body tissue.

3. austenitic-ferrite Duplex stainless steel: Both austenitic and ferritic stainless steel advantages, and has superplasticity. Austenitic and ferritic tissues each account for about half of the stainless steel. In the case of low C, CR content in 18%~28%,ni content in 3%~10%. Some steel also contains Mo, Cu, Si, Nb, ti,n and other alloying elements. This kind of steel is characterized by austenitic and ferritic stainless steels, compared with ferrite, plasticity, toughness is higher, no room temperature brittleness, intergranular corrosion resistance and welding performance are significantly improved, while also maintaining ferrite stainless steel 475 ℃ brittleness and high thermal conductivity, with superplasticity and so on. Compared with austenitic stainless steel, high strength and resistance to intergranular corrosion and chloride corrosion resistance are significantly improved. Duplex stainless steel has excellent pitting resistance and is also a kind of nickel stainless steel.

4. Martensite stainless steel: High strength, but poor plasticity and weldability. The common grades of martensitic stainless steels are 1cr13, 3cr13, due to high carbon content, it has a higher strength, hardness and wear resistance, but slightly less corrosion resistance, for mechanical performance requirements of higher, corrosion resistance requirements of general some parts, such as springs, steam turbine blades, hydraulic valves and so on. This kind of steel is used after quenching and tempering treatment.

5. precipitation hardening stainless steel: The matrix is austenitic or martensite, precipitation hardening of stainless steel commonly used grades have 04cr13ni8mo2al and so on. It can be treated by precipitation hardening (also known as aging hardening) to make its hard (strong) Stainless steel

Chemical composition

The corrosion resistance of stainless steel decreases with the increase of carbon content, so the carbon content of most stainless steels is lower, the maximum is not more than 1.2%, some steel WC (carbon content) is even less than 0.03% (such as 00cr12). The main alloying element in stainless steel is CR (CR), only when the CR content reaches a certain value, the steel has corrosion resistance. Therefore, the general CR (CR) content of stainless steel is at least 10.5%. Stainless steel also contains NI, Ti, Mn, N, Nb, Mo, Si and other elements.

Development process

China's stainless steel industry development and progress later, the founding of China before the reform and opening-up, the demand for our stainless steel mainly industrial and national defense cutting-edge use. After the reform and opening-up, the rapid development of national economy, the remarkable improvement of people's living standard, pull the demand of stainless steel. Entering the 90 's, China's stainless steel industry entered a rapid development period, stainless steel demand growth rate is much higher than the global level. Since 1990, the global stainless steel apparent consumption is increasing at an average annual rate of 6%, while the 90 's 10 years, China's stainless steel apparent consumption is 2.9 times times the average annual growth rate of the world. Into the 21st century, China's stainless steel industry has grown rapidly.

According to "2013-2017 China stainless steel industry market forward-looking and investment strategic Planning Analysis Report" Data statistics, 2000-2006, China's stainless steel consumption average annual growth rate of more than 21.17%. Among them, the 2001, China's stainless steel apparent consumption reached 2.05 million tons, more than the United States to become the world's first stainless steel consumer power. 2008, China's stainless steel apparent consumption reached 6.24 million tons, down 5.17% year-on-year.

November 2011, China's stainless steel production increased by 11.1% to 12.5 million tons. Production of stainless steel products 2.3368 million tons, an increase of 65.25%. Guangdong Province is China's main production base of stainless steel products, its output reached 1.837 million tons, an increase of 41.76%, accounting for the national total production of 78.61%.

Stainless steel is the most widely used in the world, the best performance price ratio of steel surface treatment methods.

With the implementation of the Western Development Strategy, the west-east gas transmission, the South-to-north water diversion, the Three Gorges Project, the rural network and the second network reconstruction of the urban power grid, China's hot dip galvanizing industry has entered a new round of high-speed development stage.

China's stainless steel industry in the raw materials of chromium nickel in foreign countries is oversupply, and in China is in short supply situation; stainless steel is overcapacity, oversupply, profit space fluctuations frequently. With the increasing competition of stainless steel industry, the integration and capital operation of large stainless steel production enterprises are becoming more and more frequent, the domestic excellent stainless steel production enterprises pay more and more attention to the research of the industry market, especially to the development environment of the enterprise and the change of customer's demand trend. Because of this, a large number of domestic excellent stainless steel brand rapid rise, and gradually become the leader in the stainless steel industry!

Market Prospects

China is now a large stainless steel, but is not a powerful country, in the process of moving towards the world stainless steel power, will also gradually set up overseas (mergers and acquisitions) stainless steel production base, which can avoid the export risk of trade protectionism, on the other hand, more conducive to timely understanding of local market demand, enhance the competitiveness of the local market.

From the contents of the 18th Session of plenary and 2014 Central Economic Working Conference, it is the three main points of China's macro-control in the 2014 to stabilize growth, adjust structure and promote reform. "China stainless steel industry development Forecast and transformation and upgrade Analysis Report", published by prospective Industry Research Institute, expects China's economy to rebound steadily in 2014, with GDP growth expected to be close to 7% in the year. The steady growth of macroeconomy has laid a solid foundation for the demand of stainless steel. Specifically, the 2014, the promotion of new urbanization, housing and slum upgrading projects, as well as environmental protection industry will be a bright spot to pull stainless steel demand.

On the export side, the sustained growth of international market demand will continue to promote the increase of China's stainless steel export demand. According to Macquarie, China's net exports of stainless steel will increase to 2 million tonnes in 2014, and by 2014 more than half of the rkef Nickel pig iron plant will form an integrated plant with stainless steel. The growth of stainless steel exports will boost domestic supply, and 2014 stainless steel production is expected to grow by 12.5% to 21.6 million tonnes.

2014, macro-control overcapacity industry will be further intensified. The Central Economic Work Conference proposed that to resolve domestic overcapacity and adjust industrial structure is an important task in the 2014. At the beginning of October 2013, the State Council issued the "guiding opinions on resolving the contradiction of the serious excess capacity", respectively, put forward the opinions of the industries of steel, cement, electrolytic aluminum, flat glass, shipbuilding and so on, and determined the main task of resolving the contradiction of serious overcapacity. Thus, the 2014 stainless steel industry will pay more attention to capacity adjustment, the new project will be more stringent control.

Main Ingredient

Common Grade

Stainless steel Seamless pipe

Composition of major chemical elements uns grade EN grade AISI brand ACI grade C Cr Mo Ni microstructure S17400 1.4542 17-4PH cb-7cu-1 0.07max 15.0~17.5-3.0~5.0 PH S41000 1.4406 410 C A-15 0.15max 11.5~13.5--Mart S43000 1.4016 430-0.12max 16.0~18.0--Mart S30400 1.4301 304 CF-8 0.08max 18.0~20.0-8.0~10.5 A US S30403 1.4306 304L CF-3 0.03max 18.0~20.0-8.0~12.0 Aus S31600 1.4401 316 cf-8m 0.08max 16.0~18.0 2.0~3.0 10.0~14.0 Aus S31603 1.4404 316L cf-3m 0.03max 16.0~18.0 2.0~3.0 10.0~14.0 Aus S31703 1.4438 317L cg-3m 0.03max 18.0~20.0 3.0~4.0 11.0~15.0 Aus N08904 1.4539 904L cn-3m 0.02max 19.0~23.0 4.0~5.0 23.0~28.0 Aus S31803 1.4462 2205 cd3mn 0.03max 21.0~23.0 2.5~3.5 4.5~6.5 Dup S32205 1.4462 2205N cd3mn 0.03max 22.0~23.0 3.0~3.5 4.5~6.5 Dup

Remark: The chemical composition of the common stainless steel seamless pipe is the main element element, not all chemical elements.

Main role

Stainless steel is not easy to produce corrosion, pitting, rust or wear. Stainless steel is also one of the highest strength materials in building materials. Because of the good corrosion resistance of stainless steel, it enables structural parts to permanently maintain the integrity of the engineering design. Chromium-containing stainless steel also set mechanical strength and high extensibility in a, easy parts processing and manufacturing, to meet the needs of architects and structural designers.

Grade Group

Precipitation-hardened stainless steel. With good formability and good weldability, it can be used as ultra-high strength material in nuclear industry, aviation and aerospace industry.

According to the composition can be divided into Cr series (400), CR (300 series), Cr-mn-ni (200 series), heat-resistant chromium alloy steel (500 series) and precipitation hardening System (600 series).

200 Series: Chromium-manganese-nickel austenitic stainless steel

300 Series: chromium-nickel austenitic stainless steel

301: Good ductility, used for molding products. It can also be hardened quickly by machining. Good weldability. Abrasion resistance and fatigue strength is better than 304 stainless steel.

302: Corrosion resistance with 304, because the carbon content is relatively high and thus better strength.

303: By adding a small amount of sulfur, phosphorus to make it easier to cut the processing of 304.

304: The current commonly used models, that is, 18/8 stainless steel. GB brand for 06cr19ni10.

309: Better temperature resistance compared to 304.

316: After 304, the second most widely used steel grades, mainly for the food industry, pharmaceutical industry and surgical equipment, add molybdenum elements to obtain a special anti-corrosion structure. It is also used as "marine steel" because it has better resistance to chloride corrosion than 304. SS316 are usually used in nuclear fuel recovery devices. Grade 18/10 stainless steels are usually also suitable for this application level.

321: Other than because of the addition of titanium elements to reduce the risk of material weld rust, other performance similar to 304.

347: Add the Diazepam element niobium, suitable for welding aviation equipment parts and chemical equipment.

400Series: Ferritic and martensitic stainless steel.

408: Good heat resistance, weak corrosion resistance, 11% of cr,8% ni.

409: The cheapest model (Anglo-American), usually used as automotive exhaust pipe, is ferritic stainless steel (chrome).

410: Martensite (high strength chromium steel), good wear resistance, corrosion resistance is poor.

416: Added sulfur improves the material processing performance.

420: "Cutting tool grade" martensitic steel, similar to the first stainless steel cloth high Chromium Also used in surgical tools, can be made very bright.

430: ferritic stainless steel, decorative, for example, for automotive accessories. Good formability, but poor temperature resistance and corrosion resistance.

440: High strength cutting tool steel, carbon slightly high, after the appropriate heat treatment can obtain high yield strength, hardness can reach 58HRC, belong to the most hard stainless steel column. The most common application example is razor blades. There are three kinds of commonly used models: 440A, 440B, 440C, and 440F (easy processing type).

500 series: Heat-resisting chromium alloy steel.

600 Series: Martensite precipitation hardening stainless steel.

630: The most commonly used precipitation hardening of stainless steel models, usually also called 17-4;17%cr,4%ni.

Rust Reason

Stainless steel material appears rust phenomenon, may have the following several reasons:

Chloride ion in folding environment

Chlorine ions exist widely, such as salt/sweat/seawater/sea breezes/soil etc. Stainless steel in the presence of chlorine ions in the environment, corrosion quickly, or even more than ordinary mild steel. So the use of stainless steel environment is required, but also need to wipe regularly, remove dust, keep clean and dry. (This will give him "improper use".) The United States has an example: an enterprise with an oak container containing a chlorine ion solution, the container has been used for nearly hundred years, the last century 90 's plan to replace, due to the lack of modern oak materials, the use of stainless steel 16 days after the replacement of containers due to corrosion leakage.

Folding without solution treatment

The alloying elements were not dissolved into the matrix, resulting in low matrix alloy content and poor corrosion resistance.

Folding Inherent intergranular corrosion

This material without titanium and niobium has the tendency to intergranular corrosion. The intergranular corrosion can be reduced by adding ti and NB, and then with stabilizing treatment. A high alloy steel capable of resisting corrosion in the air or chemically corrosive medium, having a beautiful surface and good corrosion resistance, without having to undergo surface treatment such as plating color, and exerting the inherent surface properties of stainless steel, used in a variety of steel, usually called stainless steel. Represents the performance of 13 chrome steel, 18-8 nickel and other high alloy steels. From the metallographic point of view, because the stainless steel contains chromium and make the surface of a very thin chromium film, this membrane separated from the steel inside the intrusion of oxygen corrosion-resistant role. In order to maintain the inherent corrosion resistance of stainless steel, steel must contain more than 12% chromium. Used for occasions where welding is required. Low carbon content minimizes the amount of carbide precipitated in the heat-affected zone near the weld, and the precipitation of carbides may lead to intergranular corrosion (weld erosion) in some environments.

Typical use

Most use requirements are to maintain the original appearance of the building for a long time. In determining the type of [1] to be selected, the main consideration is the required aesthetic standards, the corrosive nature of the local atmosphere and the cleaning system to be adopted. However, other applications are more and more simply seeking structural integrity or water permeability. For example, the roofs and side walls of industrial buildings. In these applications, the cost of construction of the owner may be more important than the aesthetic, and the surface is not very clean. The use of 304 stainless steel in a dry indoor environment is quite good. However, in rural and urban areas to maintain their appearance outdoors, it is necessary to wash regularly. In the heavily polluted industrial areas and coastal areas, the surface will be very dirty, or even rust. But to obtain the aesthetic effect of outdoor environment, it is necessary to use nickel-containing stainless steel. Therefore, 304 stainless steel is widely used in curtain wall, side wall, roof and other building uses, but in the corrosive industrial or marine atmosphere, it is best to use 316 stainless steel.

Now, people are fully aware of the advantages of using stainless steel in structural applications. Several design guidelines include 304 and 316 stainless steels. Because the "Duplex" stainless steel 2205 has been a good atmospheric corrosion resistance and high tensile strength and elastic limit intensity of integration, so the European guidelines also include this steel. Product shape, in fact, the stainless steel is manufactured in full standard metal shapes and sizes, and there are many special shapes. The most commonly used products are made of thin plates and strips, and special products are produced with medium and heavy plates, for example, the production of hot-rolled steel and extruded structural steel. And there are round, oval, square, rectangular and hexagonal welded pipe or seamless steel pipe and other forms of products, including profiles, rods, wire and castings. Ten, the surface state as will be mentioned later, in order to meet the architects ' aesthetic requirements, has developed a variety of commercial surface processing. For example, the surface can be highly reflective or matte, it can be glossy, polished or embossed, can be coloured, coloured, plated, or etched on the stainless steel surface, can also be brushed, etc. to meet the design of the appearance of various requirements. It is easy to keep the surface state. Dust can be removed only by occasional flushing. Due to good corrosion resistance, it is easy to remove the surface of graffiti pollution or similar other surface pollution. Second façade decoration function, stainless steel can be widely used in the façade shop decoration, large-face stainless steel can even screen the personalized pattern, and screen printing of the new process, in the decoration industry called UV, this is a popular technology in recent years, the precision is much higher than the effect of silk screen, without Seihan, Print the desired pattern directly on the stainless steel.