DMV 29.7 / UNS S32906

1.4477

S32906

DMV 29.7 is high-alloy duplex (austenitic-ferritic) stainless steel developed for process environments associated with urea and carbamate production. Manufactured in straight or U bent forms for urea plant condensers/scrubbers or stripper tubes and associated process piping and environments where high resistance to pitting and crevice corrosion is required. Other environments include caustic soda and nitric acid applications. DMV 29.7 complements our existing grade DMV 25.22.2.

Mechanical Properties

Tensile strength:	750-800	N/mm²
Yield strength 0,2% :	550-650	≥ N/mm²
Elongation:	25	≥ %
Hardness HB30:	300	≤ HB

Chemical Composition

CARBON

C

0,030% max

SILICON

Si

0,30% max

MAGNESE

Mn

1% max

PHOSPHORUS

P

0,030% max

SULPHUR

S

0,030% max

CHROMIUM

Cr

29%

MOLYBDENUM

Mo

2,3%

Nickel

Ni

7%

at 1080 – 1140°C (1976 – 2085°F) followed by rapid cooling in air or water.

DMV 29.7 demonstrates excellent corrosion resistance properties. This originates from the high content of alloying elements, low impurity content and control of heat treatment during the production process to ensure absence of detrimental precipitates and intermetallic phases.

DMV 29.7 has a duplex (austenitic-ferritic) structure with a ferrite content in the range 40-60%. The microstructure is free of detrimental intermetallic phases. Chemical composition nominal wt-% Carbon C≤ 0.030 Chromium Cr 29 Nickel Ni 7 Molybdenum Mo 2.3 Nitrogen N0.35 Manganese Mn 1.0 Silicon Si 0.3 Phosphorus P≤ 0.030 Sulphur S≤ 0.030 Copper Cu <0.80

DMV 29.7 has a good weldability. Welding is possible with all processes usual for stainless steels. Preheating and heat treatment after welding is normally not necessary.

Butt welding or welding to tube plate is carried out using the gas tungsten arc welding process (TIG / GTAW) with a filler metal having a similar composition (PREN > 41) enriched with elements to favour austenite formation. Use moderate heat input in the range of 10 to 25 kJ / cm.

In all cases it is imperative to remove all traces of superficial oxidation which might initiate localised attack.

OTHER UREA grades

Tensile strength:	490-690	N/mm²
Yield strength 0,2% :	205	≥ N/mm²
Elongation:	35	≥ %
Hardness HB30:	–	≤ HB

DMV 29.7 / UNS S32906