Home | Materials | NITRIC ACID GRADES | 1.4335 – UNS S 31002 – X1 Cr Ni 25.21 – 310L NAG

1.4335

UNS S 31002
X1 Cr Ni 25.21
310L NAG

Austenitic stainless steel with sharp control of the residual elements in order to provide high corrosion resistance properties in boiling 50-65% Nitric acid solutions. The silicon content is kept under 0.3% while the carbon content is lower than 0.015%.
Molybdenum additions are also well known to reduce the behaviour of the steel in nitric acid solutions. This explains why the molybdenum content is guaranteed lower than 0.3% . The sharp control of Carbon, Silicon and phosphorus contents makes it possible to produce a more stable austenite microstructure, free of intermetallic or carbide precipitations. The alloy is designed for nitric acid applications.

Production of nitric acid,
Ammonium nitrate production,
Nuclear fuel reprocessing
Hydrofluoric pickling.

The grade is not recommended for concentrated nitric acid purposes or highly oxydizing nitric acid solutions (with Cr VI species…)

Mechanical Properties

Tensile strength:	470-670	N/mm²
Yield strength 0,2% :	283	≥ N/mm²
Elongation:	40	≥ %
Hardness Brinell:	220	≤ HB

Chemical Composition

Carbon

C

0,02% max

Silicon

Si

0,15% max

Magnese

Mn

2,00% max

Phosphorus

P

0,025% max

Sulphur

S

0,005% max

Chromium

Cr

24-26% max

Nickel

Ni

20-22% max

Nitrogen

N

0,10% max

Heat Treatment

1100/1150°C (2010/2100°F) followed by rapid cooling.

Corrosion Testing
Welding

Corrosion Testing

Because of its high chromium content, 1.4335 has an excellent resistance in boiling nitric acid solutions of less than about 70% concentration.

Huey tests A262 Practice C – 5 x 48 hours
Corrosion rate (mm/year)
Without sensitization : < 0.15 (6 mpy)
After 1hour at 675°C : < 0.20 (8 mpy)
After 0.5 hour at 700°C + Slow cooling (50°C/h) : < 0.25 (10 mpy)

Welding

Welding The welding of fully austenitic material requires precautions against hot cracking.

manganese addition in the filler wire,
low heat input (< 15 KJ/cm)
controlled welding conditions
prevention of deformations during welding.

From the corrosion resistance point of view, GTAW/TIG welding is the prefered method and welds in contact with the corrosive solution should preferably be welded using this method.