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Based Knowledge (5)

What is stainless steel?
Stainless steel acid-resistant steel short, the resistance of air, steam, water and other weak corrosive medium or stainless steel having a resistance as stainless steel; and the resistance to chemical corrosion medium (acid, alkali, salt and other chemical etching) corrosion steel known as acid-resistant steel. Because of the difference in the chemical composition of different leaving their corrosion resistance, stainless steel ordinary general intolerance to chemical corrosion, and acid-resistant steel are generally of a stainless steel.
Stainless how found?
Invention and use of stainless steel, dates back to the First World War. British scientist Henry Bray Hurley improvements by the UK Government commissioned the military arsenal, weapons research. Bray Hurley thought to myself: "The? This does not wear it corrosion-resistant steels, guns can not be produced, whether it can do dishes," he went ahead, hands-on production of stainless steel fruit knife, fork, spoon, fruit plate and folding knives. Bray Hurley invention made of stainless steel in 1916, the British patent and began mass production, so far, stainless swept the world, Henry Bray Hurley is also known as the "Father of stainless steel."
What aspects of stainless steel can be applied?
Stainless steels of various kinds are used in thousands of applications. The following gives a flavour of the full range: Domestic – cutlery, sinks, saucepans, washing machine drums, microwave oven liners, razor blades.Architectural/Civil Engineering – cladding, handrails, door and window fittings, street furniture, structural sections, reinforcement bar, lighting columns, lintels, masonry supports.Transport – exhaust systems, car trim/grilles, road tankers, ship containers, ships chemical tankers, refuse vehicles.Chemical/Pharmaceutical – pressure vessels, process piping.Oil and Gas – platform accommodation, cable trays, subsea pipelines.Medical – Surgical instruments, surgical implants, MRI scanners.Food and Drink – Catering equipment, brewing, distilling, food processing.Water – Water and sewage treatment, water tubing, hot water tanks.General – springs, fasteners (bolts, nuts and washers), wire.
What are the structural components of stainless steel?
It increases the corrosion resistance of stainless steel with the carbon content decreases, and therefore, most of the low carbon stainless steel volume, the maximum does not exceed 1.2%, and some steel # C (carbon), and even less than 0.03% (e.g. 00Cr12 ). Stainless steel is the main alloying elements Cr (chromium), only when the Cr content reaches a certain value, the steel has corrosion resistance. Therefore, stainless steel is generally Cr (chromium) content of at least 10.5%. Stainless steel further contains Ni, Ti, Mn, N, Nb, Mo, Si, Cu and other elements.
What types of stainless steel?
Stainless steel is often organized by the state is divided into: martensitic steels, ferritic steels, austenitic steels, austenitic - ferritic (duplex) stainless steel and precipitation hardening stainless steel. In addition, the composition can be divided into: chromium stainless steel, stainless steel and chrome-nickel-chromium manganese nitrogen stainless steel.

Main Types (5)

Ferritic Stainless Steel
Ferrite - These steels are based on a small amount of chromium and carbon are usually less than 0.10%. These steels have similar microstructures, carbon steel and low alloy steels. They often use relatively thin partial restrictions, lack of weld toughness. However, they are not required to provide a wide range of welding applications. They can not be hardened by the heat treatment. High-chromium steel and molybdenum may be added as the water use in very positive terms. Ferritic steels also chose their stress corrosion cracking. They are not as austenitic stainless steel as formable. They have magnetic properties.
Austenitic Stainless Steel
Austenitic - these steels are the most common. Their microstructure is from adding nickel, manganese and nitrogen sources. It is the same structure at much higher temperatures occur in the ordinary steel. This combination of structure makes these steels weldability and formability characteristics. Corrosion resistance can be enhanced by the addition of chromium, molybdenum and nitrogen. They can not be hardened by the heat treatment, but can be cured with a high intensity level in order to work, while maintaining a useful level of the useful properties of ductility and toughness. Standard austenitic steels are susceptible to stress corrosion cracking. High nickel austenitic steels increased resistance to stress corrosion cracking. They are nominally non-magnetic, but usually exhibit work hardening is dependent on the number of magnetically responsive composition and steel.
Martensitic Stainless Steel
Martensite - these steels are based on similar chromium ferritic steels, but with a higher proportion of the carbon content of up to 1%. This allows them to be hardened and tempered like steel and low alloy steel. They are used where high strength and moderate corrosion resistance. They compared the long-term product, in the form of sheets and plates are more common. They generally low weldability and formability. They have magnetic properties.
Austenitic - Ferritic Duplex Stainless Steel
Duplex - microstructure of these steels have about 50% ferrite and 50% austenite. This gives them more than any ferritic or austenitic steel higher strength. They are resistant to stress corrosion cracking. The so-called "dual-phase" steels are formulated to have a standard and austenitic steels with enhanced strength and resistance to stress corrosion cracking than the corrosion resistance. "Super duplex" steel has increased strength and resistance compared to standard austenitic steels all forms of corrosion. They are soldered, but requires heat input welding consumables and choice to take care of. They have moderate formability. They are magnetic, but not too much, since 50% of the austenite phase ferritic, martensitic and precipitation hardening stainless steel.
Precipitation Hardening Stainless Steel
Precipitation hardening (PH) - These steels by adding elements such as copper, niobium and aluminum to the development of very high strength steel. With a suitable "aging" heat treatment, the formation of very fine particles impart strength steel matrix. Before these steels can be processed into complex shapes, requiring good tolerance exists as a final aging treatment from the final disposal minimal distortion. This is in contrast to the conventional quenched and tempered martensitic steel, which distortion is more problematic. Corrosion resistance comparable to standard austenitic steels as 1.4301 (304).

The Ain Characteristic (5)

Usage of different welding performance requirements also vary. A Class of cutlery on the welding performance is generally not required, even including some pot enterprises. But most products require materials welding performance is good, like second-class tableware, mug, steel pipes, water heaters, drinking fountains and the like.
Corrosion Resistance
The vast majority of stainless steel products require good corrosion resistance, like a second class tableware, kitchen utensils, water heaters, drinking fountains, and some products also make foreign businessmen corrosion test: NACL aqueous solution heated to boiling, pour a period of time out solution, wash drying, weigh loss, to determine the degree of corrosion (Note: polishing, because sandpaper or emery cloth containing Fe component will lead to the surface of the test rust).
Polished Performance
Today's society in the production of stainless steel products generally are polished in this process, only a few products such as water heaters, drinking fountains and other interior does not require polishing. Therefore, this requires a good polishing performance materials. Factors affecting polishing performance of the following main points:
① material surface defects. Such as scratches, pitting, over-pickling.
② raw material problem. Hardness is too low, it is difficult to throw light (BQ bad) when polished, and the hardness is too low, in the deep drawing surface prone to orange peel, thus affecting BQ property. BQ relatively high hardness like.
③ After deep drawing products, areas of extreme deformation of the surface will be a small black dot and RIDGING, thus affecting BQ property.
Heat Resistance
Heat resistance at high temperatures means that stainless steel can maintain its excellent mechanical properties. Influence of carbon: carbon in austenitic stainless steels are the formation of a strong and stable. Given the expansion of austenite and austenite element region. Carbon austenite forming ability of about 30 times that of the nickel, carbon is an interstitial element, solid solution strengthening can significantly improve the strength of austenitic stainless steel. Carbon austenitic stainless steel can also improve performance in a high concentration of chloride (eg boiling 42% MgCl2 solution) in resistance to stress corrosion.
Corrosion Resistance
When the number of atoms of chromium content in the steel of not less than 12.5%, the electrode potential of steel can be mutated by the negative potential to rise to the positive electrode potential. Prevent electrochemical corrosion.

Frequently Asked Questions (5)

Can I use stainless steel at low temperatures?
Toughness is measured by impacting a small sample with a swinging hammer. The distance which the hammer swings after impact is a measure of the toughness. The shorter the distance, the tougher the steel as the energy of the hammer is absorbed by the sample. Toughness is measured in Joules (J). Minimum values of toughness are specified for different applications. A value of 40 J is regarded as reasonable for most service conditions.In contrast austenitic steels only show a gradual fall in the impact toughness value and are still well above 100 J at -196 deg C.
Is stainless steel non-magnetic?
It is commonly stated that "stainless steel is non-magnetic". This is not strictly true and the real situation is rather more complicated. The degree of magnetic response or magnetic permeability is derived from the microstructure of the steel. A totally non-magnetic material has a relative magnetic permeability of 1. Austenitic structures are totally non-magnetic and so a 100% austenitic stainless steel would have a permeability of 1. In practice this is not achieved. There is always a small amount of ferrite and/or martensite in the steel and so permeability values are always above 1. Typical values for standard austenitic stainless steels can be in the order of 1.05
What surface finishes are available on stainless steels?
There are many different types of surface finish on stainless steel. Some of these originate from the mill but many are applied later during processing, for example polished, brushed, blasted, etched and coloured finishes.The importance of surface finish in determining the corrosion resistance of the stainless steel surface cannot be overemphasised. A rough surface finish can effectively lower the corrosion resistance to that of a lower grade of stainless steel.
How do I choose which stainless steel to use?
Most decisions about which steel to use are based on a combination of the following factors: 1. What product form is required? – Not all grades are available in all product forms and sizes, for example sheet, bar, tube. In general, the austenitic steels are available in all product forms over a wide range of dimensions. Ferritics are more likely to be in sheet form than bar. For martensitic steels, the reverse is true. 2. It must also be borne in mind that steel type alone is not the only factor in material selection. Surface finish is at least as important in many applications, particularly where there is a strong aesthetic component ect...
What is 'multiple certification'?
This is where a batch of steel meets more than one specification or grade. It is a way of allowing melting shops to produce stainless steel more efficiently by restricting the number of different types of steel. The chemical composition and mechanical properties of the steel can meet more than one grade within the same standard or across a number of standards. This also allows stockholders to minimise stock levels.


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