不锈钢等级说明.docx

1、不锈钢等级说明不锈钢等级说明In metallurgy, stainless steel is defined as a steel alloy with a minimum of 10% chromium content by mass.1 Stainless steel does not stain, corrode, or rust as easily as ordinary steel (it stains less), but it is not stain-proof.2 It is also called corrosion-resistant steel or CRES whe

2、n the alloy type and grade are not detailed, particularly in the aviation industry. There are different grades and surface finishes of stainless steel to suit the environment to which the material will be subjected in its lifetime. Common uses of stainless steel are cutlery and watch straps.Stainles

3、s steel differs from carbon steel by amount of chromium present. Carbon steel rusts when exposed to air and moisture. This iron oxide film is active and accelerates corrosion by forming more iron oxide. Stainless steels have sufficient amount of chromium present so that a passive film of chromium ox

4、ide forms which prevents further corrosion.Contents hide1 History 2 Properties 3 Applications 3.1 Uses in sculpture, building facades and building structures 4 Recycling & reuse 5 Types of stainless steel 5.1 Comparison of standardized steels 5.2 Stainless steel grades 6 Stainless steel finishes 7 S

5、ee also 8 References 8.1 Notes 8.2 Bibliography 9 External links noted their resistance against attack by some acids and suggested their use in cutlery. Metallurgists of the 19th century, however, were unable to produce the combination of low carbon and high chromium found in most modern stainless s

6、teels, and the high-chromium alloys they could produce were too brittle to be practical.In the late 1890s, Hans Goldschmidt of Germany developed an aluminothermic (thermite) process for producing carbon-free chromium. In the years 19041911 several researchers, particularly Leon Guillet of France, pr

7、epared alloys that would today be considered stainless steel.Friedrich Krupp Germaniawerft built the 366-ton sailing yacht Germania featuring a chrome-nickel steel hull in Germany in 1908.4 In 1911, Philip Monnartz reported on the relationship between the chromium content and corrosion resistance. O

8、n October 17, 1912, Krupp engineers Benno Strauss and Eduard Maurer patented austenitic stainless steel.5Similar developments were taking place contemporaneously in the United States, where Christian Dantsizen and Frederick Becket were industrializing ferritic stainless.Harry Brearley of the Brown-F

9、irth research laboratory in Sheffield, England is commonly credited as the inventor of stainless steel. In 1913, while seeking an erosion-resistant alloy for gun barrels, he discovered and subsequently industrialized a martensitic stainless steel alloy. The discovery was announced two years later in

10、 a January 1915 newspaper article in The New York Times.3 This was later marketed under the Staybrite brand by Firth Vickers in England and was used for the new entrance canopy for the Savoy Hotel in 1929 in London.6edit PropertiesHigh oxidation-resistance in air at ambient temperature are normally

11、achieved with additions of a minimum of 13% (by weight) chromium, and up to 26% is used for harsh environments.7 The chromium forms a passivation layer of chromium(III) oxide (Cr2O3) when exposed to oxygen. The layer is too thin to be visible, and the metal remains lustrous. It is impervious to wate

12、r and air, protecting the metal beneath. Also, this layer quickly reforms when the surface is scratched. This phenomenon is called passivation and is seen in other metals, such as aluminium and titanium. When stainless steel parts such as nuts and bolts are forced together, the oxide layer can be sc

13、raped off causing the parts to weld together. When disassembled, the welded material may be torn and pitted, an effect that is known as galling. This destructive galling can be best avoided by the use of dissimilar materials, e.g. bronze to stainless steel, or even different types of stainless steel

14、s (martensitic against austenitic, etc.), when metal-to-metal wear is a concern. In addition, Nitronic alloys (trademark of Armco, Inc.) reduce the tendency to gall through selective alloying with manganese and nitrogen.Nickel also contributes to passivation, as do other less commonly used ingredien

15、ts such as molybdenum and vanadium.edit ApplicationsThe pinnacle of New Yorks Chrysler Building is clad with type 302 stainless steel.8 An art deco sculpture on the Niagara-Mohawk Power building in Syracuse, New York Pipes and fittings made of stainless steel Stainless steels resistance to corrosion

16、 and staining, low maintenance, relatively low cost, and familiar luster make it an ideal base material for a host of commercial applications. There are over 150 grades of stainless steel, of which fifteen are most common. The alloy is milled into coils, sheets, plates, bars, wire, and tubing to be

17、used in cookware, cutlery, hardware, surgical instruments, major appliances, industrial equipment, and as an automotive and aerospace structural alloy and construction material in large buildings. Orange juice and other food transport and storage tankers are often made of stainless steel, due to its

18、 corrosion resistance and antibacterial properties. This also influences its use in commercial catering kitchens and food processing plants, as it can be steam cleaned, sterilized, and does not need painting or application of other surface finishes.Stainless steel is also used for jewellery and watc

19、hes. The most common stainless steel alloy used for this is 316L. It can be re-finished by any jeweller and will not oxidize or turn black. Not all manufacturers use this type; Rolex for instance use type 904L for their stainless steel watches.9edit Uses in sculpture, building facades and building s

20、tructuresStainless steel was in vogue during the art deco period. The most famous example of this is the upper portion of the Chrysler Building (illustrated to the right). Diners and fast food restaurants feature large ornamental panels, stainless fixtures and furniture. Owing to the durability of t

21、he material, many of these buildings retain their original appearance. The forging of stainless steel has given rise to a fresh approach to architectural blacksmithing in recent years. The Gateway Arch (picture above) is clad entirely in stainless steel: 886 tons (804 metric tonnes) of 0.25 in (6.4

22、mm) plate, #3 finish, type 304 stainless steel.1 Type 316 stainless is used on the exterior of both the Petronas Twin Towers and the Jin Mao Building, two of the worlds tallest skyscrapers. 2 The Parliament House of Australia in Canberra has a stainless steel flagpole weighing over 220 tons. The aer

23、ation building in the Edmonton Composting Facility, the size of 14 hockey rinks, is the largest stainless steel building in North America. 3 The United States Air Force Memorial has an austenitic stainless steel structural skin. edit Recycling & reuseStainless steel is 100% recyclable. In fact, an a

24、verage stainless steel object is composed of about 60% recycled material, 25% originating from end-of-life products and 35% coming from manufacturing processes.10edit Types of stainless steelThere are different types of stainless steels: when nickel is added, for instance, the austenite structure of

25、 iron is stabilized. This crystal structure makes such steels non-magnetic and less brittle at low temperatures. For greater hardness and strength, carbon is added. When subjected to adequate heat treatment, these steels are used as razor blades, cutlery, tools, etc.Significant quantities of mangane

26、se have been used in many stainless steel compositions. Manganese preserves an austenitic structure in the steel as does nickel, but at a lower cost.Stainless steels are also classified by their crystalline structure:Austenitic, or 300 series, stainless steels comprise over 70% of total stainless st

27、eel production. They contain a maximum of 0.15% carbon, a minimum of 16% chromium and sufficient nickel and/or manganese to retain an austenitic structure at all temperatures from the cryogenic region to the melting point of the alloy. A typical composition of 18% chromium and 10% nickel, commonly k

28、nown as 18/10 stainless, is often used in flatware. Similarly, 18/0 and 18/8 are also available. Superaustenitic stainless steels, such as alloy AL-6XN and 254SMO, exhibit great resistance to chloride pitting and crevice corrosion due to high molybdenum content (6%) and nitrogen additions, and the h

29、igher nickel content ensures better resistance to stress-corrosion cracking versus the 300 series. The higher alloy content of superaustenitic steels makes them more expensive. Other steels can offer similar performance at lower cost and are preferred in certain applications.citation needed The low

30、carbon version of the Austenitic Stainless Steel, for example 316L or 304L, are used to avoid corrosion problem caused by welding. The L means that the carbon content of the Stainless Steel is below 0.03%, this will reduce the sensitization effect, precipitation of Chromium Carbides, due to the high

31、 temperature produced by welding operation.Ferritic stainless steels are highly corrosion-resistant, but less durable than austenitic grades. They contain between 10.5% and 27% chromium and very little nickel, if any, but some types can contain lead. Most compositions include molybdenum; some, alumi

32、nium or titanium. Common ferritic grades include 18Cr-2Mo, 26Cr-1Mo, 29Cr-4Mo, and 29Cr-4Mo-2Ni. Martensitic stainless steels are not as corrosion-resistant as the other two classes but are extremely strong and tough, as well as highly machineable, and can be hardened by heat treatment. Martensitic stainless steel contains chromium (12-14%), molybdenum (0.2-1%), nickel (0-2%), and carbon (about 0.1-1%) (giving it more hardness but making the material a bit more brittle). It is quenched a