Types of stainless steel
Stainless steel is 100% recyclable. An average stainless steel object is composed of about 60% recycled material of which approximately 40% originates from end-of-life products a-nd about 60% comes from manufacturing processes. A-nd because of its resistance to corrosion a-nd staining, low maintenance a-nd familiar lustre, stainless steel became an ideal material for many applications. Stainless steel is used in mould, industrial machine(for example, in an ice cream plant), household hardware, etc.
There are different types of stainless steels: when nickel is added, for instance, the austenite structure of iron is stabilized. This crystal structure makes such steels virtually non-magnetic a-nd less brittle at low temperatures. For greater hardness a-nd strength, more carbon is added. With proper heat treatment, these steels are used for such products as razor blades, cutlery, a-nd tools.
Stainless steel is usually divided into 5 types by their crystalline structure:
1. Austenitic, or 200 a-nd 300 series, stainless steels have an austenitic crystalline structure, which is a face-centered cubic crystal structure. This structure gives these steels their ch-aracteristic combination of weldability a-nd formability. Corrosion resistance can be enhanced by adding C-hromium, Molybdenum a-nd Nitrogen. These steels are the most common. Austenite steels make up over 70% of total stainless steel production. Sta-ndard austenitic steels are vulnerable to stress corrosion cracking. Higher nickel austenitic steels(Superaustenitic stainless steels) have increased resistance to stress corrosion cracking.
2. Ferritic stainless steels generally have better engineering properties than austenitic grades, but have reduced corrosion resistance, because of the lower c-hromium a-nd nickel content. They are also usually less expensive. Ferritic stainless steels lack of toughness in welds, so, they are usually limited in use to relatively thin sections.
3. Martensitic stainless steels are similar to ferritic steels in being based on C-hromium but have higher Carbon levels up as high as 1%. Martensitic stainless steels are not as corrosion-resistant as the other two classes but are extremely strong a-nd tough, as well as highly machinable, a-nd can be hardened by heat treatment.
4. Precipitation-hardening martensitic stainless steels have corrosion resistance comparable to austenitic varieties, but can be precipitation hardened to even higher strengths than the other martensitic grades. These steels can be machined to quite intricate shapes.
5. Duplex stainless steels have a mixed microstructure of austenite a-nd ferrite, the aim usually being to produce a 50/50 mix, although in commercial alloys the ratio may be 40/60. Duplex stainless steels have roughly twice the strength compared to austenitic stainless steels a-nd also improved resistance to localized corrosion, particularly pitting, crevice corrosion a-nd stress corrosion cracking. They are c-haracterized by high c-hromium (19-32%) a-nd molybdenum (up to 5%) a-nd lower nickel contents than austenitic stainless steels. Duplex stainless steels are weldable but need care in se-lection of welding consumables a-nd heat input. They have moderate formability.
There are different types of stainless steels: when nickel is added, for instance, the austenite structure of iron is stabilized. This crystal structure makes such steels virtually non-magnetic a-nd less brittle at low temperatures. For greater hardness a-nd strength, more carbon is added. With proper heat treatment, these steels are used for such products as razor blades, cutlery, a-nd tools.
Stainless steel is usually divided into 5 types by their crystalline structure:
1. Austenitic, or 200 a-nd 300 series, stainless steels have an austenitic crystalline structure, which is a face-centered cubic crystal structure. This structure gives these steels their ch-aracteristic combination of weldability a-nd formability. Corrosion resistance can be enhanced by adding C-hromium, Molybdenum a-nd Nitrogen. These steels are the most common. Austenite steels make up over 70% of total stainless steel production. Sta-ndard austenitic steels are vulnerable to stress corrosion cracking. Higher nickel austenitic steels(Superaustenitic stainless steels) have increased resistance to stress corrosion cracking.
2. Ferritic stainless steels generally have better engineering properties than austenitic grades, but have reduced corrosion resistance, because of the lower c-hromium a-nd nickel content. They are also usually less expensive. Ferritic stainless steels lack of toughness in welds, so, they are usually limited in use to relatively thin sections.
3. Martensitic stainless steels are similar to ferritic steels in being based on C-hromium but have higher Carbon levels up as high as 1%. Martensitic stainless steels are not as corrosion-resistant as the other two classes but are extremely strong a-nd tough, as well as highly machinable, a-nd can be hardened by heat treatment.
4. Precipitation-hardening martensitic stainless steels have corrosion resistance comparable to austenitic varieties, but can be precipitation hardened to even higher strengths than the other martensitic grades. These steels can be machined to quite intricate shapes.
5. Duplex stainless steels have a mixed microstructure of austenite a-nd ferrite, the aim usually being to produce a 50/50 mix, although in commercial alloys the ratio may be 40/60. Duplex stainless steels have roughly twice the strength compared to austenitic stainless steels a-nd also improved resistance to localized corrosion, particularly pitting, crevice corrosion a-nd stress corrosion cracking. They are c-haracterized by high c-hromium (19-32%) a-nd molybdenum (up to 5%) a-nd lower nickel contents than austenitic stainless steels. Duplex stainless steels are weldable but need care in se-lection of welding consumables a-nd heat input. They have moderate formability.
