Duplex UNS S31803 Technical Information
Overview
Duplex is an austenitic ferritic Iron Chromium-Nickel alloy with Molybdenim addition. It has good resistance to pitting, a high tensile strength and higher resistance to stress corrosion cracking at moderate temperatures to that of conventional austenitic stainless steels.
Duplex is a material having an approximate equal amount of austenite and ferrite. These combine excellent corrosion resistance with high strength. Mechanical properties are approximately double those of singular austenitic steel and resistance to stress corrosion cracking is superior to type 316 stainless steel in chloride solutions. Duplex material has a ductile / brittle transition at approximately -50°C. High temperature use is usually restricted to a maximum temperature of 300°C for indefinite use due to embrittlement.
Benefits
There are several benefits of Duplex including:
- High Strength
- High resistance to pitting, crevice corrosion resistance
- High resistance to stress corrosion cracking, fatigue and erosion
- Excellent resistance to Chloride stress corrosion cracking
- Low thermal expansion and higher heat conductivity than Austenitic steels
- High energy absorption
- Good workability and weldability
Applications
Pipe – ASTM A790
The method of manufacture can be either seamless or automatic welding, with no addition of filler metal. Pipe may be hot or cold finished but must always be furnished in the heat treated condition.
BUTT WELD – ASTM A815
This class covers the class of WP, made up of 4 categories and meet the requirements of ANSI B16.9. Pressure ratings are the same compatability of matching pipe.
Categories :-
- WP-S : Seamless Construction
- WP-W : Welded Construction where construction welds are radiographed
- WP-WX : Welded Construction where all welds are radiographed
- WP-WU : Welded Construction where al welds are Ultrasonically Tested.
Flanges ASTM A182
ASTM specifications regulate approved raw materials from which flanges can be made. Forged or rolled alloy steel pipe flanges, forged fittings and valves for high temperature applications.
Technical Details
| %C | %Cr | %Ni | %Mo | %Mn | %S | %P | %Si | %N |
| 0.03 | 21.0-23.0 | 4.5-6.5 | 2.5-3.5 | 2.00 | 0.020 | 0.030 | 1.00 | 0.08-0.20 |
| Yield Strength | Tensile Strength | Elongation (Minimum) | Reduction of Area (Minimum) | Hardness (Maximum)* | ||
| (Ksi) | (Mpa) | (Ksi) | (Mpa) | (Bhn) | ||
| 65 | 450 | 90 | 620 | 20 | – | 290 |
* (N.A.C.E. MR-01-75 latest revision may limit hardness in certain applications)
PREn (PITTING RESISTANCE EQUIVALENT) – (%Cr) + (3.3 x %Mo) + (16 x %N)
HEAT TREATMENT: SOLUTION ANNEALED AT 1020 DEG C – 1100 DEG C WATER QUENCH
| UNS | BS EN | SWEDEN SS | GERMANY DIN | FRANCE AFNOR | SANDVIK + |
| 31803 | 1.4462 | 2377 | X2 CrNiMoN 22.5.3 | Z2 CND 22.05.03 | SAF 2205 |