The 1.4501 is an austenitic-ferritic, high-alloy, low-carbon chromium-nickel-molybdenum-tungsten (super duplex) steel that is resistant to chloride-containing media and can be used in areas where traditional duplex steels are no longer adequate. Due to higher contents of chromium and molybdenum in combination with tungsten, the PREN-values of the material are from 40 to> 46 J with good impact values and wear resistance properties at -40 ° C. The steel 1.4501 - ASTM A182 F55 - Superduplex: UNS S32760 is resistant to seawater, has a high resistance to surface, as well as hole and crevice corrosion and is suitable to use in sulfuric acid.
1.4501 is listed under the classification AISI F55 according to ASTM A182 Grade F55 standardization.
1.Areas of application
The main applications of this stainless steel are among others, the chemical and petrochemical industry. Further applications are in desalination of seawater or brackish water (H₂S) areas, in food technology and shipbuilding (chemical tanker construction).
Characteristics
Welding: The steel 1.4501 is weldable with all processes (TIG welding, MAG solid wire, arc welding, submerged arc welding). The exception is gas-melt welding! There is a risk of intermetallic compounds. Welding consumables, predominantly similar electrodes, should be used in welding, as they increase elongation properties at high temperatures. However, a change in the corrosion properties is to be expected in the area where the weld took place (heat-affected zone).
Forging: Before forging, the steel should be heated to 1150°C to 1180°C. The forging process takes place at 1200°C and 1000°C with subsequent air cooling. The surface treatment measures required for all rust- and acid-resistant steels are also valid for the 1.4501.
Machining: Machining should be carried out in the solution-annealed condition, with low cutting speeds (20-40 [m / min] and low feed.) Due to the low thermal conductivity (due to high alloy contents), care must be taken to ensure sufficient cooling and the resulting tool life.
Corrosion resistance: This stainless steel has a very good corrosion resistance. Use in media causing pitting or stress corrosion cracking is possible because tungsten increases pitting resistance. The PREN values (chromium sum) can be> 40 according to the chemical analysis.
Polishing: Due to the two-phase ferrite-austenite structure, the resulting polishing pattern characteristic of this material changes.
2.Heat treatment
The heat treatment of the 1.4501 is carried out by solution annealing in the range 1040-1120°C with rapid cooling in sufficient water and this is also recommended after welding larger cross sections.
| Temperature | Cooling | |
| Hot forming | 1.200°C - 1100°C | Air |
| Heat treatment | ||
| Solution annealing (+ AT) | 1.040°C-1140°C | Water (quick cooling) |
3.Physical Properties
| Density (kg/dm3 ) | 7,8 |
| Electr. Resistance at 20°C (Ω mm2 /m) | 0,8 |
| Thermal conductivity at 20°C (W/m K) | 15 |
| Specific heat capacity at 20°C (J/kg K) | 480-500 |
4.Chemical composition
| 1.4501 | C | Si | Mn | P | S | Cr | Mo | Ni |
| min. | 24,0 | 3,00 | 6,00 | |||||
| max. | 0,030 | 1,00 | 1,00 | 0,035 | 0,01 | 26,0 | 4,00 | 8,00 |
| 1.4501 | V | Al | Cu | N | Nb | Ti | W |
| min. | 0,50 | 0,20 | 0,50 | ||||
| max. | 1,00 | 0,30 | 1,00 |
