Stainless Steel Pipe Fittings

How the Austenite Ferrite Balance Achieved By

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How the Austenite Ferrite Balance Achieved By

To understand how duplex stainless steel works, first compare the composition of two familiar steel austenitic 304 (1.4301) and ferritic 430 (1.4016).

Structure Grade  EN Number C Si Mn P S N Cr   Ni Mo
Ferritic 430 1.4016 0.08 1.00 1.00 0.040 0.015 16.0/18.0
Austenitic 304 1.4301 0.07 1.00 2.00 0.045 0.015 0.11 17.5/19.5 8.0/10.5

The important elements in stainless steel can be classified into ferritisers and austenitisers. Each element favours one structure or the other: 
Ferritisers – Cr (chromium), Si (silicon), Mo (molybdenum), W (tungsten), Ti (titanium), Nb (niobium) 
Austenitisers – C (carbon), Ni (nickel), Mn (manganese), N (nitrogen), Cu (copper) 
Grade stainless steel 430 has a predominance of ferritisers and so is ferritic in structure. Grade stainless steel 304 becomes austenitic mainly through the use of about 8% nickel. To arrive at a duplex structure with about 50% of each phase, there has to be a balance between the austenitisers and the ferritisers. This explains why the nickel content of duplex stainless steels is generally lower than for austenitics.

Here are some typical compositions of duplex stainless steel:

Grade  EN No/UNS Type Approx Composition 
Cr Ni Mo N Mn W Cu
LDX2101 1.4162
 Lean 21.5  1.5 0.3 0.22 5
DX2202 1.4062/ S32202 Lean 23 2.5 0.3 0.2
RDN 903 1.4482/ 
Lean 20 1.8 0.2  0.11 4.2
2304 1.4362/ 
 Lean 23 4.8  0.3  0.10
2205 1.4462/ 
Standard  22 5.7 3.1 0.17
2507 1.4410/ 
Super 25 7 4 0.27
Zeron 100 1.4501/ 
Super 25  7 3.2 0.25 0.7 0.7
Uranus 2507Cu
Super 25 6.5 3.5 0.25 1.5

In some of the recently developed stainless steel grades, nitrogen and manganese are used together to bring the nickel content to very low levels. This has a beneficial effect on price stability. 
At present, we are still very much in the development phase of duplex stainless steel. Therefore, each mill is promoting its own particular brand. It is generally agreed that there are too many grades. However, this is likely to continue until the “winners” emerge.

Established in 2008, Zhejiang Yaang Pipe Industry Co., Limited is a professional organizer and one-stop-shop supplier for steel piping system products, including duplex stainless steel pipes and duplex stainless steel tubes, duplex stainless steel flangesand duplex stainless steel fittings, duplex stainless steel butt-welding pipe fittings, duplex stainless steel elbows, duplex stainless steel tees, duplex stainless steel reducers, duplex stainless steel stub end, duplex stainless steel gaskets, duplex stainless steel fasteners, duplex stainless steel valves, duplex stainless steel Sanitary Services etc. in China. We have devoted to providing the best solutions of steel materials and industrial equipment for our respected customers.

Source: Zhejiang Yaang Pipe Industry Co., Limited (

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Duplex Stainless Steel

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