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