Which are the 5 types of stainless steel
Stainless steel is a form of iron that contains amounts of chromium, nickel, most of the times manganese, lead and nitrogen as a supplement to the iron base.
The amount of nickel content is the key that determines the type of ferritic chromium-iron alloy. The change in this microstructure can bring about a noticeable increase in hardness.
There are 5 basic types of stainless steel:
1. Austenitic Stainless Steel
2. Ferritic Stainless Steel
3. Martensitic Stainless Steel
4. Duplex (Ferritic – Austenitic) (Duplex Stainless Steel)
5. Precipitation Hardening Stainless Steel
1. Austenitic Stainless Steel.
Austenitic stainless steels are the most widely used of the stainless alloys in industrial applications.
The reason for this is the increased strength they have which is better than all types of steel.
Common Uses: Piping - Fittings - Sink Rolls - Bearings - Pump and Valve Parts e.t.c.
2. Ferritic Stainless Steel.
Ferritic stainless steel is an alloy containing more than 12% chromium and this property makes it different for 2 main reasons, its composition and molecular structure.
Ferritic stainless steel is defined as an alloy containing 10.5% - 30% chromium and less than 20% carbon.
Types of ferritic steel are: 430, 430 LI, 434, 439 etc.
Its chromium content defines its hardness, its resistance to oxidation and its gloss.
The difference between ferritic and austenitic stainless steel is that the former contains less nickel.
3. Martensitic Stainless Steel.
Martensitic stainless steel is the type of steel that is in the form of martensite. Through aging and heat treatment it can be achieved or hardening.
Martensitic stainless steel is a high or low carbon steel and is built around the composition of iron with 12-17% chromium and carbon from 0.10 – 1.2%.
Common applications: Pumps, valves and boat shafts, also due to their increased wear resistance in cutlery, medical instruments, bearings, etc.
4. Duplex Stainless Steel.
Duplex stainless steel is so named because its construction includes 2 phases: austenitic and ferritic in equal amounts.
It is designed to provide greater oxidation resistance and greater strength than a standard 304 or 316 stainless steel.
The biggest difference of Duplex from other types is that it contains more chromium, 20 – 28% more lead, up to 5% more nickel and 0.05 – 0.50% nitrogen.
Common uses: Architecture - Oil and gas (Pumps - Valves), Chemical, Engineering.
5. Precipitation Hardening Stainless Steel.
Precipitation hardening steel or as we call it aging hardening or particle hardening is the result of a heat treatment technique that is widely used to increase the yield strength of materials such as aluminum, steel, etc.
Common applications: NAK55 low carbon steel, 6000 aluminum alloys for bicycle frames and aeronautical structures.