ISO/TR 15608 Material Group 6.3: Cr-Mo-V Steels such as material no. 1.7779 with
3,5 % ≤ Cr < 7,0 %, Mo ≤ 0,7 % and 0,45 < V ≤ 0,55 % such as material no. 1.7779
Features of low alloyed Cr-Mo-V steel (2.25Cr–1Mo–V)
Hydrosteel CrMo (V) steels with 0.5 % V offer better performance for petrochemical reactors compared to 10CrMo9-10 steels that means the specified yield strength and creep properties for this material is a lot of better compared to 10CrMo9-10 steel.
Depending on the heat treatment, the yield strength of 20CrMoV13-5-5 steel is in the range of Rp0,2 = 520 – 640 MPa.
Applications for low alloyed Cr-Mo-V (20CrMoV13-5-5) steel
This material may be used in all applications requiring service conditions under high temperature and high pressure of hydrogen. Steel for hydrogen service an elevated temperature and pressure is stell that not readily susceptible to decarbusation by hydrogen at elevated pressures and temperatures and thus to hydrogen and grain boundary embitterment. This characteristic is achieved ba adding alloying elements that from carbides at the operating temperature.
Is particularly suitable for pressure equipment in high temperature hydrogen service (e.g. hydro treating reactors, exchangers, hydro treating reactors, hydro desulfurizers, hydro crackers)
Welding conditions for 20CrMoV13-5-5 steel
Welding needs precautions, in particular: tight control of preheat, interpass temperature intermediate stress relieving and post weld heating to avoid cold cracking;
Weld metal and HAZ in the as welded condition are susceptible to hydrogen induced cold cracking.
However, the risk of cold cracking is known to occur in the weld metal more frequently than in the HAZ. Therefore, a preheat and minimum interpass temperature of 200°C is recommended for thickness higher than 30 mm. After welding a Dehydrogenation Heat Treatment ≥ 300 °C is recommended. After welding, these steels generally have to be PWHT e.g. 700 -730 °C.
| Name | Number | Standard | Product | Remark |
|---|---|---|---|---|
| 20CrMoV13-5-5 D, Cl. 4a | 1.7779 K31835 | EN 10216-2 ASTM A-542 | Smls. tube Forging | EN 13445-2 & EN 13480-2 ASME BPVC |