Stainless Steel Classification, Welding, Chemical Table

Classification of Stainless Steel

Metallurgically, stainless steels are classified into 3 groups:

Martensitic
Ferritic
Austenitic

Martensitic Class:  - This is the straight chromium type of stainless, containing Chromium as it's main alloying element.
It is normally Hard and Brittle, includes 4% - 10% Chromium types and is Air Hardening,
and Magnetic. Preheat and Postheat is necessary when welding.

Ferritic Class:  - Is also straight Chromium type.
Normally is Soft and Ductile., includes the 12% - 28% Chromium types.
It is Magnetic. Preheat and Postheat is necessary when welding

Austenitic Class:  - This steel is of the Chromium-Nickel type.
The Nickel content usually ranges from 7% - 35% with 8% - 10% being the most predominantly used.
It is Strong, Ductile and Impact Resistant
Non-magnetic in the annealed condition, but slightly magnetic when cold worked.
No preheat or Postheat is necessary when welding.

How Heat affects Stainless Steel

Heat and Hardness

if you heat the mild carbon steel to 1600 -1900 F and quickly quench, for example immersion in water,
you will get a Maximum Hardness.
If you give the same treatment to Austenitic or Chrome-Nickel steel, you will achieve
Maximum Softness.

Heat and Corrosion Resistance

Carbide precipitation causes the stainless steel to loose its corrosion resisting properties in the areas affected. Best seen at areas of welding, rusty discoloration indicates that the alloy was robbed of its Chromium.
Martensitic Stainless Steels are not subject to Carbide Precipitation or loss of corrosion resistance.
They are considered stable over the entire temperature range.

Heat and Grain growth

Martensitic SS are affected by Grain growth of the individual crystals when subjected to elevated welding or forging temperatures
This grain growth causes the metal to become Brittle.
Small crystals can be restored by heat treatments to improve Ductility
Pre-heats and post-heats are used to slow down the cooling to avoid excessive hardening and to prevent cracking.
Will harden intensely when allowed to Air cool - result in Cracking

Welding Stainless Steels

Class

Series

Pre/Post heat

Magnetic

Cooling

Martensitic
Ferritic
Austenitic

400
400
300

YES
YES
NEVER

YES
YES
NONMAGNETIC

SLOW
SLOW
N/A

A small amount of ferrite in 300 series welds inhibits cracking
Only a fully austenitic welds are nonmagnetic
Small diameter welding rods help keep the heat to a minimum
The suffix "-16" indicated titania-type electrode coating which can be run AC or DC reverse polarity.
Titania type has a very smooth arc and the metal flows more freely with practically no spatter.
The bead is thinner and more concave - lack of material frequently causing cracks
The suffix "-15" indicated lime-type electrode coating which should be run DC reverse polarity only.
Less slag than titania type, deposits are sound, high strength. More convex and thicker, no cracking problem.

Stainless & Heat Resisting Steels - Chemical table

Type	Carbon	Mangan	Phosp	Sulphur	Si	Cr	Nickel	Moly	Sellenium	Uncommon

201	0.15 Max	5.50 7.50	0.060	0.030	1.00	16.00 18.00	3.50 5.50	-	-	N 0.25

202	0.15 Max	7.50 10	0.060	0.030	1.00	17.00 19.00	4.00 6.00	-	-	N 0.25
Type	Carbon	Mangan	Phosp	Sulphur	Si	Cr	Nickel	Moly	Sellenium	Uncommon

301	0.15 Max	2.00	0.045	0.030	1.00	16.00 18.00	6.00 8.00	-	-	-

302	0.15 Max	2.00	0.045	0.030	1.00	17.00 19.00	8.00 10.00	-	-	-

302 B	0.15 Max	2.00	0.045	0.030	2.00 3.00	17.00 19.00	8.00 10.00	-	-	-

303	0.15 Max	2.00	0.20	Min 0.15	1.00	17.00 19.00	8.00 10.00	0.60	-	Zr 0.60

303 Se	0.15 Max	2.00	0.20	0.06	1.00	17.00 19.00	8.00 10.00	-	Min 0.15	-

304	0.08 Max	2.00	0.045	0.030	1.00	17.00 19.00	8.00 10.00	-	-	-

304 L	0.03 Max	2.00	0.045	0.030	1.00	18.00 20.00	8.00 12.00	-	-	-

305	0.12 Max	2.00	0.045	0.030	1.00	17.00 19.00	8.00 10.00	-	-	-

308	0.08 Max	2.00	0.045	0.030	1.00	17.00 19.00	8.00 10.00	-	-	-

309	0.20 Max	2.00	0.045	0.030	1.00	22.00 24.00	12.00 15.00	-	-	-

309 S	0.08 Max	2.00	0.045	0.030	1.00	22.00 24.00	12.00 15.00	-	-	-
310	0.25 Max	2.00	0.045	0.030	1.50	24.00 26.00	19.00 22.00	-	-	-

310 S	0.08 Max	2.00	0.045	0.030	1.50	24.00 26.00	19.00 22.00	-	-	-

314	0.25 Max	2.00	0.045	0.030	1.50	17.00 19.00	8.00 10.00	-	-	-

316	0.08 Max	2.00	0.045	0.030	1.00	16.00 18.00	10.00 14.00	2.00 3.00	-	-

316 L	0.03 Max	2.00	0.045	0.030	1.00	16.00 18.00	10.00 14.00	2.00 3.00	-	-

317	0.08 Max	2.00	0.045	0.030	1.00	18.00 20.00	11.00 15.00	3.00 4.00	-	-

321	0.08 Max	2.00	0.045	0.030	1.00	17.00 18.00	8.00 12.00	-	-	Ti 5xC

347	0.08 Max	2.00	0.045	0.030	2.00 3.00	17.00 18.00	9.00 13.00	-	-	Ta 10xC

348	0.08 Max	2.00	0.045	0.030	2.00 3.00	17.00 19.00	9.00 13.00	-	-	Cb-Ta \| Ta 10xC \| 0.10
Type	Carbon	Mangan	Phosp	Sulphur	Si	Cr	Nickel	Moly	Sellenium	Uncommon

403	0.08 Max	2.00	0.045	0.030	0.50	11.50 13.00	-	-	-	-

405	0.08 Max	2.00	0.045	0.030	1.00	11.50 14.50	-	-	-	-

410	0.15 Max	1.00	0.040	0.030	1.00	11.50 13.50	-	-	-	-

414	0.15 Max	1.00	0.040	0.030	1.00	11.50 13.50	1.25 2.50	-	-	-

416	0.15 Max	1.25	0.06	0.15 Min	1.00	12.00 14.00	-	0.60	0.60	-

416 Se	0.15 Max	1.25	0.06	0.15 Min	1.00	12.00 14.00	-	-	-	Se 0.15 Min

420	Over 0.15	1.00	0.040	0.030	1.00	12.00 14.00	-	-	-	-

430	0.12 Max	1.00	0.045	0.030	1.00	14.00 18.00	-	-	-	-

430F	0.12 Max	1.25	0.06	0.15 Min	1.00	14.00 18.00	-	0.60	0.60	-

430F Se	0.12 Max	1.25	0.06	0.06	1.00	14.00 18.00	-	-	-	Se 0.15 Min

431	0.20 Max	1.00	0.045	0.030	1.00	15.00 17.00	1.25 2.50	-	-	-

440A	0.60 0.75	1.00	0.040	0.030	1.00	16.00 18.00	-	0.75 Max	-	-

440B	0.75 0.95	1.00	0.040	0.030	1.00	16.00 18.00	-	0.75 Max	-	-

440-C	0.95 1.20	1.00	0.040	0.030	1.00	16.00 18.00	-	0.75 Max	-	-

440-XH	1.60	0.50	-	-	0.40	16.00	0.35	0.80	-	-

446	0.20 Max	1.50	0.040	0.030	1.00	23.00 27.00	-	-	-	N 0.25 Max
Type	Carbon	Mangan	Phosp	Sulphur	Si	Cr	Nickel	Moly	Sellenium	Uncommon

501	0.10 Max	1.00	0.040	0.030	1.00	4.00 6.00	-	0.40 0.65	-	-

502	Over 0.10	1.00	0.040	0.030	1.00	4.00 6.00	-	0.40 0.65	-	-

Created and maintained by Tony Hnilica