THEORY - Intro
Stainless Steels:
Steels are ferrous alloys with a level of Carbon lower than 2%.
There are non-alloyed and alloyed steels (high-alloyed steel refers to elements in alloy higher or equal to 5%; low-alloyed have instead elements in alloy lower than 5%)
What are they:
Basically they are high-alloyed steels and more precisely alloys in Iron - Carbon – Chrome: Fe + Cr(>10.5%) + C
Main characteristics:
The key characteristic of Stainless Steel is that of having good resistance against corrosion, mainly thanks to the fact that these alloys form a slight chrome oxide layer on the surface which makes the steel resistant in sufficiently oxidising environments - this phenomenon is the so called passivation. This layer is mainly made of chrome oxides and metallic oxides, all of the Me (OH) type.
Kind of alloys:
Stainless steels are divided into 3 groups based on the structural characteristics of the alloy.
These groups are:
Austenitic Steels : Fe + Cr (16÷28%) + Ni (6÷32%) + C (0.02÷0.1%)
Ferritic Steels : Fe + Cr (10.5÷30%) + C (0.02÷0.1%)
Martensitic Steels : Fe + Cr (12÷19%) + C (0.08÷1.2%)
The difference between these groups consists in the Chemical composition as well as in the characteristics of the alloys (mechanical characteristics and resistance to oxidation). In this brief introduction, we will consider only austenitic and ferritic steels, which are produced by Arinox S.r.l.
We would like to remind you that arguments treated below are not complete. They only relate to those aspects which are of major interest for what concerns the stainless steel, above all for what considers description of Heat Treatments.
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