ISO/TR 15608 Material Group 9.3:
Nickel alloy steels with 8,0 < Ni ≤ 10,0 %
9Ni-steels for Cryogenic and Low-Temperature Service
Low-temperature steels generally refer to steels applied below 0℃. The addition of Ni and other alloying elements can reduce interstitial impurities, refine grain, control the size, shape and distribution of the second phase, etc., so as to reduce the Ductile – Brittle transition temperature of ferrite steel. Alloying elements in low temperature steel mainly affect the low temperature toughness of steel. The low-temperature toughness of steel increased by Nickel is 5 times as much as that of manganese, and the brittle transition temperature decreased by about 10℃ for every 1% increase in nickel content, which is mainly due to the fact that nickel was not reacted with carbon and all dissolved into the solid solution to strengthen it.
Applications for 9Ni-steels
This material group retain adequate Charpy V-notch toughness, and thus high resistance to brittle fracture, even in the temperature range down to -196° C. This makes them the perfect choice for gas-liquefaction plants, for example, and for the transportation and storage of liquefied gases, such as LNG and LPG.
Welding of 9Ni-steels
The characteristic properties of welding consumables for welding Low-Temperature steels is their deformation capacity at low temperatures, which is usually tested using the notched bar impact bending test. The value of the impact energy is used to draw conclusions about the tendency to brittle fracture and the suitability for use up to a certain temperature. When welding at low temperature steels, attention must be paid to controlled heat input in order to keep the heat-affected zone as narrow as possible and still avoid hardening peaks.
The 9% Ni steel is mainly joined with nickel-based filler metals. These nickel-based types have advantages over conventional austenites. Due to a higher yield strength and the possibility of heat treatment of welded joints. They can also be used for steels with a low nickel content. With limited mixing with the base material, crack resistance and sufficient cold toughness down to -200°C are ensured.
EN 13445: Cryogenic and low-temperature steels
| Name/Grade | Number | Standards | Product | Remarks/Trade Marks |
|---|---|---|---|---|
| X8Ni9+NT640 X8Ni9+QT640 X8Ni9+QT680 X8Ni9 | 1.5662 1.5662 1.5662 1.5662 | EN 10028-4 EN 10028-4 EN 10028-4 EN 10222-3 | Plate Plate Plate Forging | EN 13445-2 & EN 13480-2 EN 13445-2 & EN 13480-2 EN 13445-2 & EN 13480-2 EN 13445-2 & EN 13480-2 |
| X10Ni9 X10Ni9+QT X10Ni9+QT | 1.5682 1.5682 1.5682 | EN 10216-4 EN 10216-4 EN 10253-2 | Seamless tube Seamless tube Fittings | EN 13445-2 & EN 13480-2 EN 13445-2 & EN 13480-2 EN 13445-2 & EN 13480-2 |
| II II | K71340 K71340 | ASTM A- 522 ASTM A-533 | Forging Plate | ASME BPVC ASME BPVC |
| X7Ni9 8 WPL8 I I | 1.5663 K81340 K81340 K81340 K81340 | EN 10028-4 ASTM A-333 ASTM A-420 ASTM A-522 ASTM A-553 | Plate Welded tube Fitting Forging Plate | EN 13445-2 & EN 13480-2 ASME BPVC ASME BPVC ASME BPVC ASME BPVC / CryElso® 9Q |
| LC3 | J31550 | ASTM A-352 | Casting | ASME BPVC |
| LC4 | J41500 | ASTM A-352 | Casting | ASME BPVC |