What Is The Difference Between Duplex And Super Duplex?
The ferritic and austenitic phases that are present in the metallurgical microstructure of both regular duplex and super duplex steels are a distinctive feature of these steels. This indicates that they combine ferritic and austenitic characteristics. Chromium, nickel, and molybdenum are included in the composition, along with additional elements in lesser amounts.
Chromium concentration in duplex stainless steels can reach up to 22% of the composition, however it can reach up to 25% in super duplex steels. The super duplex material has higher corrosion resistance because to the increased and variable nickel and molybdenum content.
The super duplex material is more expensive than the ordinary duplex grades because it contains more chromium, nickel, and molybdenum. Standard duplex and super duplex materials come in several grades. There are variations in the material composition of each variety. The prices vary depending on the material composition. Super duplex typically costs more than lower-grade ordinary duplex.
Chromium carbide precipitation, which can eventually lead to localised corrosion and intergranular corrosion, is one of the main problems when welding metallic components. Both duplex and super duplex materials run the danger of chromium carbide precipitation due to their high chromium content in the composition.
However, the carbide precipitation is also influenced by the carbon content of these materials. Prior to welding, both materials must be heated, and heat treatment must be applied after welding. Given that the right methods are followed and the right parameters are maintained, both of these materials are ideal for welding since they are less likely to corrode.
One of the most crucial characteristics of duplex and super duplex stainless steels is their corrosion resistance. These are used to replace older, more conventional steel varieties. Both grades have more corrosion resistance than the majority of austenitic stainless steels, but the super duplex has even greater corrosion resistance.
The super duplex can be used in chemical, marine, sea water and food grade applications as it is resistant to most general corrosive components, mild acids and oxidizing agents. Depending on the different grades of super duplex, the corrosion resistance properties vary.
Machine tools can be used to cut and shape duplex materials. The duplex grades can be cut and machined quicker than the super duplex. Due to its higher concentration of chromium, nickel, and molybdenum compared to other duplex grades, super duplex is more difficult to machine.
Precise and strong tools have to be deployed with sluggish machining and cutting rates. The best cutting speeds on duplex and super duplex materials must pass specific tests. To ascertain the cutting and machining characteristics of different grades of duplex and super duplex stainless steels, tests including the turning test, chip formation test, and drilling test can be carried out.
Grade |
C |
Mn |
Si |
P |
S |
Cr |
Mo |
Ni |
N |
Fe |
S31803 |
0.030 max |
2.00 max |
1.00 max |
0.030 max |
0.020 max |
22.0 – 23.0 |
3.0 – 3.5 |
4.50 – 6.50 |
0.14 – 0.20 |
63.72 min |
S32205 |
0.030 max |
2.00 max |
1.00 max |
0.030 max |
0.020 max |
21.0 – 23.0 |
2.50 – 3.50 |
4.50 – 6.50 |
0.8 – 0.20 |
63.54 min |
| S31803 / S32205 | Density | Melting Point | Yield Strength (0.2%Offset) | Tensile Strength | Elongation |
| 7.8 g/cm3 | 1350 °C (2460 °F) | Psi – 80000 , MPa – 550 | Psi – 116000 , MPa – 800 | 15 % |
| STANDARD | WERKSTOFF NR. | UNS |
| Duplex 2205 | 1.4462 | S31803 / S32205 |
Grade |
UNS |
EN |
W-Nr |
DIN |
AFNOR |
SS |
|---|---|---|---|---|---|---|
Duplex 2707 HD Bars |
S32707 |
- |
- |
- |
- |
- |
Duplex 2507 Bars |
S32750 |
1.4410 |
- |
X 2 CrNiMoN 25 7 4 |
- |
2328 |
C |
Si |
Mn |
P |
S |
Cr |
Ni |
Mo |
N |
Cu |
|---|---|---|---|---|---|---|---|---|---|
≤0.030 |
≤0.8 |
≤1.2 |
≤0.035 |
≤0.015 |
25 |
7 |
4 |
0.3 |
≤0.5 |
Proof strength |
Tensile strength |
Elong. |
Hardness |
|---|---|---|---|
Rp0.2a) |
Rm |
Ab) |
Rockwell C |
ksi |
ksi |
% |
|
≥80 |
110-135 |
≥25 |
≤28 |
