316L Grade UREA for urea plant applications: Properties, Chemical Composition

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

Mechanical Properties

Tensile strength:	500-700	N/mm²
Yield strength 0,2% :	200	≥ N/mm²
Elongation:	40/30	≥ %
Hardness HB30:	215	≤ HB

Chemical Composition

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.

Source: https://www.gemaco-piping.com/materials/urea-grades/1-4435-x2crnimo18-14-3-316l-s31603/

UREA 25.22.2 -310MoLN – UNS S31050

UREA 25.22.2 chemical composition has been optimized for specific uses in Urea plants. 

It is a 310L modified austenitic stainless steel with low carbon, low silicon and high nitrogen additions in order to stabilize and strengthen the austenitic phase. The alloy is particularly designed for improved corrosion resistance properties in 

Ammonium carbamate environments including strippers. The grade is also well designed for resistance in wet corrosive conditions due to its high contents of chromium, molybdenum and nitrogen (PREN > 33). 

UREA 25.22.2 is designed for the fabrication of lining interiors in Urea units or complementary products (pipes, fittings…). The grade can be used for urea strippers.

Liner strip UREA 25.22.2 -310MoLN – UNS S31050 for relining Urea reactor in Fertilizer Plants

Mechanical Properties

Tensile strength:	540-740	N/mm²
Yield strength 0,2% :	250	≥ N/mm²
Elongation:	35/30	≥ %
Hardness Brinell:	240	≤ HB

Chemical Composition

Carbon C 0,020% max

Silicon Si 0,40% max

Manganese Mn 2% max

Phosphorus P 0,020%max

Sulphur S 0,010% max

Chromium Cr 24-26%

Molybdenum Mo 2,0-2,6%

Nickel Ni 21-23,5%

Nitrogen N 0,10-0,15%

Heat Treatment

heat treatment (1140°-1180°C –2084-2156°F) and water quenching

Corrosion testing

The corrosion resistance properties are enhanced thanks to the low carbon level, low silicon level and complementary additions of nitrogen.

Typical maximum corrosion results required following different specifications for the 25.22.2 grade after 5 periods of 48 h following ASTM A 262-C practice are:

maximum general corrosion: 1,6 μm/48 h or 65 mg/dm² per hour with a maximum depth of microcracks of 100 μm in the long direction of rolling.

Non destructive testing

• Ferrite check 100% (less than 0,5%)
• Measurement location chosen by Inspector

Welding

UREA 25.22.2 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 nitride precipitations, low silicon contents as well as no intermetallic phase precipitations. Higher manganese content products should be considered.

Source: https://www.gemaco-piping.com/materials/urea-grades/1-4466-urea-25-22-2-310moln-uns-s31050/