What is stainless steel?
Stainless steel is a large group of materials, which all have in common that the main element is iron (from this “steel”) and the contents of chromium (Cr) is at least 10,5%. Besides chromium and iron, the steel can contain a wide range of other alloy elements. That could, for instance, be nickel (Ni), carbon, (C), and molybdenum (Mo). The different alloys serve the purpose of either enhancing the mechanical and/or the attributes regarding corrosion of the steel. Besides enhancing the steel, the alloy elements have significance for which type of quality the stainless steel is. The same goes for the amount of chromium. It is namely the contents of chromium and the alloys, which is of significance to determine which type of group or stainless steel the product belongs to. In total, there exist 5 types – or qualities – of stainless steel: Austenitic, Ferritic, Martensitic, Duplex, and Super Duplex.
Duplex steel differentiates itself from other types of stainless steel in this way
Similar to all the other main groups of stainless steel, an entire family of Duplex steel exists. When you just say “duplex steel” it often refers to the alloy EN 1.4462. This alloy, amongst other things, is characterised by its high contents of chromium (21-23% Cr) and its contents of molybdenum (2,5-3,5%), which is a bit over the contents of the acidproof austenitic group (minimum 2% Mo). Both these contents are present to ensure outstanding resistance to corrosion. On the other hand, the contents of nickel are low, which helps ensure a relatively low price. The combination of impressive resistance to corrosion and a fair price turns 4462 into the “workhorse” within the group of duplex steels – around half of the duplex steel on the market is exactly 4462.
Different types of stainless steel
The lowest alloyed types of stainless steel qualities (e.g. EN 1.4003) only contain 10,5% chromium while the remaining content is iron and was invented back in 1912. Already in 1913, in Germany, the tillegering of nickel was discovered for the sake of mechanical qualities and in 1920, it was discovered that the tillegering of even small amounts of molybdenum (Mo) benefits the resistance to corrosion tremendously. Thereby, the “acidproof” types of steel were born. Stainless steel can by crystalline structure be divided into different types of stainless steel spread out across five main groups:
- Austenitic stainless steel
- Martensitic stainless steel
- Ferritic stainless steel
- Duplex stainless steel
- Precipitation hardening stainless steel
Books about stainless steel
Unique to Danish steel wholesalers, Damstahl has enthroned knowledge and learning. We see the passing of our words of wisdom to our many interested customers as a natural duty. This partly takes place through seminars and consultancy tasks, and partly through our books. Actually, throughout the years, this has resulted in no less than four educational books about stainless steel.
See and order our books here