What Is Stainless Steel?

Benoît Van Hecke

What is stainless steel ?
oxygen
passive layer
bulk stainless steel
1D
2B
2R
2H
The most popular grade is EN 1.4016 (AISI 430). Low chromium alloys can be chosen in nonsevere environments and where appearance is not a priority. Chromium and molybdenum increase corrosion resistance. Titanium and niobium improve weldability.
What are the ferritic options?
Relative corrosion resistance
1.4016
430
Fe
17% Cr
1.4000
410S
1.4003
1.4521
444
Improved corrosion resistance and weldability
+Cr
+Cr, Mo
1.4510
439
1.4520
430Ti*
Improved weldability
1.4509
441*
Improved weldability and oxidation resistance
1.4113
434
Improved corrosion resistance
+Mo, Ti, Nb
+Ti
+Mo
1.4512
409
Improved weldability
+Cr, Nb
* common designations
+Ti
1.4526
436

+Nb
1.4513

+Ti
Designations according to EN 10088 and AISI. For details about chemical composition and equivalence, please consult www.euro-inox.org/technical_tables.

Duplex stainless steels typically show higher mechanical properties and corrosion resistance than the most common ferritic and austenitic grades. The relative differences between duplex stainless steel grades – of which EN 1.4462 is the most popular one – should be viewed in this context.

And what about duplex?
1.4462
2205*
Fe
22% Cr 5% Ni 3% Mo
1.4362
2304*
1.4162
2101*
1.4410
2507*
1.4507
255*
1.4501
Add N to increase strength
Add Cr, Mo, W, N , Cu to increase corrosion resistance
Add N to increase strength
Add Mo, N to increase corrosion resistance
Add N to increase strength
Add Cr to increase corrosion resistance
Relative corrosion resistance
Designations according to EN 10088 and AISI
For details about chemical composition and equivalence, please consult www.euro-inox.org/technical_tables.


Weldability
Corrosion Resistance Mechanical Properties
+Ti 1.4541
321
Low C 1.4307
304L*
1.4306
304L*
+Ti 1.4571
316Ti
2% Mo: 1.4404
316L*
2.5% Mo: 1.4432
316L*
3% Mo: 1.4438
317L
Ni alloys
2% Mo: 1.4401
316*
2.5% Mo: 1.4436
316*
3% Mo: 317
Add Cr - Ni to increase resistance at high temperatures
Substitute C by N to increase weldability, ductility and corrosion resistance
Increase Ni (12%) to enhance expansion forming
1.4315
304N
1.4311
304LN
1.4310
301
1.4318
301LN
1.4303
305
1.4828
1.4833
309(S)
1.4841
310/314
1.4845
310(S)
Designations according to EN 10088 and AISI. Please note that there is no 1:1 relationship between AISI and EN grades (*). For details about chemical composition and equivalence, please consult www.euro-inox.org/technical_tables.
Increase C to increase mechanical properties (incl. cold working)
Reduce C or add Ti to avoid intergranular corrosion after welding
Add N to raise strength, also at low temperatures
Weldability
Mechanical Properties
Oxidation Resistance
Corrosion Resistance
304
1.4301
Fe
18% Cr
8% N i
Add Mo to increase corrosion resistance
How are austenitic grades interrelated?
Starting from the universal commodity grade 1.4301, the alloying content can be adapted to
modify the steel’s characteristics:
+
Add Cr, Mo, N to achieve superior corrosion resistance
6% Mo: 1.4547
1.4529
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