1.4435; X2CrNiMo18-14-3; 316L G.Urea; S31603
The UREA 316L grade has been specially developed for
urea plant applications. It is a 316L modified stainless steel with
extra – low silicon content and substantial higher molybdenum contents. The low
carbon content, combined with a well balanced chemistry (low silicon and nickel
content close to 14%) makes the alloy fully austenitic, free of intermetallic
phase precipitations. The ferrite level is kept under 0.5% in the solution
annealing and water quenched conditions. The UREA 316L grade is designed for the
fabrication of lining interiors in urea units for improved corrosion resistance
properties in urea – carbonate environments or complementary products (pipes,
fittings…). The alloy is not designed for nitric acid application.
316L UG pipes
|
Tensile strength: |
500-700 |
N/mm² |
|
Yield strength 0,2% : |
200 |
≥ N/mm² |
|
Elongation: |
40/30 |
≥ % |
|
Hardness HB30: |
215 |
≤ HB |
Carbon C 0,020% max
Silicon Si 0,40% max
Magnese Mn 2% max
Phosphorus P 0,045% max
Sulphur S 0.015% max
Chromium Cr 17,0-19,0 min
Molybdenum Mo 2,2-3%
Nickel Ni 12,5-15,0%
Heat Treatment
at 1120 – 1180°C (2048 – 2156°F) followed by water
quenching.
Corrosion Testing
Typical maximum
corrosion results required following different specifications after Huey tests
(ASTM A262 C – five periods of 48 h.) are:
- maximum
weight loss lower than 3,3 μm/48 h (130 mg/dm² per 24 h.)
- maximum
depth for microcracks of 200 μm in the long direction and 70 μm in the
transverse direction.
Nondestructive
testing
- Ferrite check
100% (less than 0,5%)
- Measurement
location chosen by Inspector.
Welding
Welding The UREA 316L grade can be
welded with most of the welding processes: TIG, Plasma, MIG welding, as well as
SMAW, SAW or FCAW processes. The alloy is sensitive to hot cracking phenomenon
due to its fully austenitic microstructure. Weld should be performed in order
to obtain extra – low ferrite contents, no carbide or nitrides precipitations,
low silicon contents as well as no intermetallic phases precipitations. Higher
manganese content products should be considered.
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