Brittle fracture resistant steels at low and very low-temperatures (cryogenic temperatures) applications are increasingly becoming the focus of energy supply due to the increasing transportation of liquid gases.
What is cryogenic technology?
The term cryogenics-refrigeration is used to describe methods at very low temperatures (typically below 125/150 K = -148/-123 °C, and distinguish them from ordinary refrigeration cycles. Many of these methods relate to the liquefaction of gases known as permanent, like air, natural gas, nitrogen and hydrogen and helium below 23 K = -250°C)
Cryogenics is therefore the study of processes, techniques and apparatus happening or employed at temperatures below 125 K. Cryogenics apparatus are tanks and piping including valves and are used to store and transport cryogenic fluids, such as liquid nitrogen, oxygen, argon, helium, hydrogen, and natural gas and vaporizers to convert cryogenic liquids into gases by using heat from various sources, such as ambient air, water, steam, or electricity.
Note 1: Refrigeration typically refers to the process of cooling a space, substance, or system to lower temperatures (but not as extreme as cryogenics) for e.g. food industry.
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Material for low temperature application
Material properties change with changes in temperature, this also applies to material temperatures below room temperature and even further below, as used for cryogenic technology.
The yield and tensile strength of metals with a body-centered cubic solid solution structure, such as steels, is highly temperature-dependent. These metals lose their ductility in a narrow temperature range below room temperature.
The tensile strength of metals with face-centered cubic structures – aluminum, copper, nickel and austenitic stainless steel – is more temperature dependent than their yield strength, and the metals often increase in ductility as temperature decrease.
Ferritic, martensitic and duplex stainless steels tend to become brittle as the temperature is reduced, in a similar way to other ferritic / martensitic steels. The austenitics do not exhibit an impact ductile / brittle transition, but rather a progressive reduction in charpy impact values as the temperature is lowered.
EN 13445-2 requirements for pressure equipment to prevent brittle fractures at low temperatures
EN 13445 contains criteria for pressure equipment for the prevention of brittle fracture of steels in the form of plates, strips, pipes, fittings, forgings, castings, flanges, fasteners and weldments used in pressure parts at low temperatures. The criteria are based on the impact energy requirements at specific temperatures for the base material, the heat-affected zone (HAZ including the fusion line) and the weld metals.
For pressure equipments with design temperatures TS ≤ 50°C, EN 13445-2 specified three alternative Methods for establishing criteria for the prevention of low temperature brittle fracture:
- Methode 1: Code of Practice
- Technical requirements based on the choice of TR = T27J as specified in harmonised European material standards and on the assumption that it is possible to achieve this minimum properties after fabrication and
- based on operating experience for Ni-alloyed steels with Ni ≥ 3% up to 9%, for austenitic steels and for bolt and nuts
- Method 2: Methode developed from the principles of fracture mechanics and from operating experience
- Methode 3: The application of a fracture mechanics analysis
The following explanations are for the practicable method 1.
Low-temperature steels
EN 13445-2 Annex B generally contains specific requirements for the prevention of brittle fracture and requirements for prevention of brittle fracture at low temperature.
- Ferritic steels > see Table 1 below
- Non-alloy low-temperature steels
- Low-alloyed low-temperature steels
- Nickel alloy steels containing 1,5 to 3,5 % Ni (down to -105° C).
- Nickel alloy steels containing 5 to 9 % Ni (down to -100° C / -196° C).
- Austenitic stainless steels (Cryogenic steels) (down to – 273°C ) > see Table 2 below
Remarks: EN ISO 21028-1: Cryogenic vessels – Toughness requirements for materials at cryogenic temperature – Part 1: Temperatures below -80 °C .
This standard contains additional requirements for charpy impact values or alternate for lateral expansion on impact standard specimens according to ISO 148-1.
Table 1: Ferritic steels
Listed ferritic steels taken from harmonised European material standards with specified impact properties below –10 °C.
| Design Reference Temperature 1 TR = TM (Method 1) | Standard | Product | Reference thickness (as welded / PWHT) [mm] | Delivery Condition Treatment 5 | Mat’l name | Mat’l no. |
|---|---|---|---|---|---|---|
| –20 °C | EN 10028-2 | Plate (N) | 35 / 200 35 / 200 35 / 110 35 / 70 | N N N N | P235GH P265GH P295GH P355GH | 1.0345 1.0425 1.0481 1.0473 |
| EN 10028-3 | Plate (N) | 35 / 200 35 / 70 | N N | P275NH P355NH | 1.0487 1.0565 | |
| EN 10028-5 | Plate (TM) | 35 / – 3 35 / – 3 | M M | P355M P420M | 1.8821 1.8824 | |
| EN 10028-6 | Plate (QT) | 35 / 70 35 / 70 | QT QT | P355Q P355QH | 1.8866 1.8867 | |
| EN 10216-3 | Seamless tube (N) | 35 / 70 35 / 70 | N N | P355N P355NH | 1.0562 1.0565 | |
| EN 10217-3 | Welded tube | 35 / 40 35 / 40 | N N | P355N P355NH | 1.0562 1.0565 | |
| EN 10273 | Rolled bar | 35 / 75 35 / 75 35 / 75 | N N QT | P275NH P355NH P355QH | 1.0487 1.0565 1.8867 | |
| EN 10222-4 | Forging incl. forged bar (N) | 35 / 85 35 / 60 35 / 50 | QT QT QT | P285QH P355QH P420QH | 1.0478 1.0571 1.8936 | |
| –40 °C | EN 10028-3 | Plate (N) | 35 / 70 35 / 70 | N N | P275NL1 P355NL1 | 1.0488 1.0566 |
| EN 10028-5 | Plate (TM) | 35 / – 3 35 / – 3 | M M | P355ML1 P420ML1 | 1.8832 1.8835 | |
| EN 10028-6 | Plate (QT) | 35 / 70 | QT | P355QL1 | 1.8868 | |
| EN 10216-3 | Seamless tube (N) | 35 / 70 35 / 70 | N N | P275NL1 P355NL1 | 1.0488 1.0566 | |
| EN 10216-4 | Seamless tube | 10 / 10 35 / 45 25 / 25 | N QT N | P215NL P255QL P265NL | 1.0451 1.0452 1.0453 | |
| EN 10217-3 | Welded tube | 35 / 40 35 / 40 | N N | P275NL1 P355NL1 | 1.0488 1.0566 | |
| EN 10217-4 | Welded tube | 10 / 10 16 / 16 | N N | P215NL P265NL | 1.0451 1.0453 | |
| EN 10217-6 | Submerged arc welded tube | 10 / 10 25 / 25 | N N | P215NL P265NL | 1.0451 1.0453 | |
| –50 °C | EN 10028-3 | Plate (N) | 35 / 200 35 / 70 | N N | P275NL2 P355NL2 | 1.1104 1.1106 |
| EN 10028-5 | Plate (TM) | 35 / – 3 35 / – 3 | M M | P355ML2 P420ML2 | 1.8833 1.8828 | |
| EN 10216-3 | Seamless tube (N) | 35 / 100 35 / 70 | N N | P275NL2 P355NL2 | 1.1104 1.1106 | |
| EN 10217-3 | Electric welded tube (N) | 35 / 40 35 / 40 | N N | P275NL2 P355NL2 | 1.1104 1.1106 | |
| –60 °C | EN 10028-4 | Plate (N) | 35 / 80 35 / 70 | N, NT N, NT | 11MnNi5-3 13MnNi6-3 | 1.6212 1.6217 |
| EN 10028-6 | Plate (QT) | 35 / 70 | QT | P355QL2 | 1.8869 | |
| EN 10216-4 | Seamless tube | 15 / 40 35 / 40 35 / 40 | QT N, NT N, NT | 26CrMo4-2 11MnNi5-3 13MnNi6-3 | 1.7219 1.5212 1.6217 | |
| EN 10222-3 | Forging incl. forged bars | 35 / 70 | NT | 13MnNi6-3 | 1.6217 | |
| –80 °C | EN 10028-4 | Plate (N) | 35 / 70 | N, NT, QT | 15NiMn6 | 1.6228 |
| EN 10222-3 | Forging incl. forged bars | 35 / 50 | NT, QT | 15NiMn6 | 1.6228 | |
| –90 °C | EN 10216-4 | Seamless tube | 35 / 40 | QT | 12Ni14 2 | 1.5637 |
| –100 °C | EN 10028-4 | Plate (N) | 35 / 80 | N, NT, QT | 12Ni14 2 | 1.5637 |
| EN 10216-4 | Seamless tube | 25 / – 3 | NT | 12Ni14 2 | 1.5637 | |
| EN 10222-3 | Forging incl. forged bars | 35 / – 3 | N | 12Ni14 2 | 1.5637 | |
| EN 10222-3 | Forging incl. forged bars | 35 / 50 | NT | 12Ni14 | 1.5637 | |
| EN 10222-3 | Forging incl. forged bars | 35 / 70 | QT | 12Ni14 | 1.5637 | |
| –110 °C | EN 10216-4 | Seamless tube | 35 / 40 | QT | X12Ni5 | 1.5680 |
| –120 °C | EN 10028-4 | Plate | 35 / 80 | N, NT, QT | X12Ni5 | 1.5680 |
| EN 10216-4 | Seamless tube | 25 / – 3 | N | X12Ni5 | 1.5680 | |
| EN 10222-3 | Forging incl. forged bars | 35 / – 3 | N | X12Ni5 | 1.5680 | |
| –196 °C | EN 10028-4 | Plate | – / – 4 | N+NT, QT N+NT | X7Ni9 X8Ni9 | 1.5663 1.5662 |
| EN 10216-4 | Seamless tube | – / – 4 | N, NT | X10Ni9 | 1.5682 | |
| EN 10222-3 | Forging incl. forged bars | – / – 4 | N, NT | X8Ni9 | 1.5662 |
2 If used at –105 °C (e. g. ethylene application), then 27 J shall be guaranteed at this temperature
3 Steels shall not be Post Weld Heat Treatment (PWHT)
4 Materials can be used to maximum thickness permitted in harmonised European material standards
5 N = normalised, NT = normalised and tempered, QT = Quenched and tempered,
Austenitic stainless steels
The austenitics stainless steels such as, 1.4301 (304), and 1.4401 (316), are however ‘tough’ at cryogenic temperatures and can be classed a ‘cryogenic steels’. The best choices of grades for very low temperatures are those with austenite stabilising additions such as nitrogen, e.g. as in grade , 1.4311 (304LN). Higher alloy grade such as 1.4539 (904L), which derive their austenite stability from higher nickel levels could also be considered.
These and almost all other austenitic corrosion-resistant steels according to European standards such as EN 10028-7, EN 10216-5, EN 10217-7, EN 10222-5 are specified with an impact energy ≥ 60 Joule at a test temperature of -196 °C and are therefore suitable for cryogenic applications. Austenitic steels are resistant to brittle fracture in the solution-annealed condition.
Table 2: Austenitic steels
Where the design temperature is below −105°C weld metal and heat affected zones for austenitic stainless steels shall meet additional requirements of EN 13445-4:2021, Clause 9.
Solution annealed (TM) austenitic stainless steels according to Table below can be applied down to temperature TM without impact testing, except when impact testing is required by the material standard.
| Lowest minimum metal temperature TM | Mat’l name | Mat’l no. | Standard | Product |
|---|---|---|---|---|
| -196 °C | X5CrNi18–10 | 1.4301 | EN 10028-7 EN 10216-5 EN 10217-7 EN 10222-5 EN 10253-4 EN 10269 EN 10272 | Plate Seamless tube Welded tube Forging Fittings Fastener Bar |
| X5CrNiMo17–12–2 | 1.4401 | EN 10028-7 EN 10216-5 EN 10217-7 EN 10222-5 EN 10253-4 EN 10269 EN 10272 | Plate Seamless tube Welded tube Forging Fittings Fasteners Bar | |
| X2CrNiMo17–12–3 | 1.4432 | EN 10028-7 EN 10217-7 EN 10222-5 EN 10272 | Plate Welded tube Forging Bar | |
| X3CrNiMo17–13–3 | 1.4436 | EN 10028-7 EN 10216-5 EN 10217-7 EN 10222-5 EN 10272 | Plate Seamless tube Welded tube Forging Bar | |
| X2CrNiMoN17–13–5 | 1.4439 | EN 10216-5 EN 10217-7 EN 10272 | Seamless tube Welded tube Bar | |
| X1NiCrMoCuN25–20–7 | 1.4529 | EN 10028-7 EN 10272 EN 10216-5 EN 10217-7 EN 10253-4 | Plate Bar Seamless tube Welded tube Fittings | |
| X1CrNiMoCuN25–25–5 | 1.4537 | EN 10028-7 | Plate | |
| X1NiCrMoCu25–20–5 | 1.4539 | EN 10028-7 EN 10272 EN 10216-5 EN 10217-7 EN 10253-4 | Plate Bar Seamless tube Welded tube Fitting | |
| X1CrNiMoCuN20–18–7 | 1.4547 | EN 10028-7 EN 10272 EN 10216-5 EN 10217-7 EN 10253-4 | Plate Bar Seamless tube Welded tube Fittings | |
| X6CrNiNb18–10 | 1.4550 | EN 10028-7 EN 10216-5 EN 10217-7 EN 10222-5 EN 10272 EN 10253-4 | Plate Seamless tube Welded tube Forging Bar Fittings | |
| X6CrNiMoNb17–12–2 | 1.4580 | EN 10028-7 EN 10216-5 EN 10272 | Plate Seamless tube Bar | |
| GX5CrNi9–10 | 1.4308 | EN 10213 | Casting | |
| GX5CrNiMo19–11–2 | 1.4408 | EN 10213 | Casting | |
| GX2NiCrMo28–20–2 | 1.4458 | EN 10213 | Casting | |
| GX2CrNi19–11 | 1.4309 | EN 10213 | Casting | |
| GX2CrNiMo19–11–2 | 1.4409 | EN 10213 | Casting | |
| -273 °C | X2CrNi19–11 | 1.4306 | EN 10028-7 EN 10216-5 EN 10217-7 EN 10253-4 EN 10272 | Plate Seamless tube Welded tube Fittings Bar |
| X2CrNi18–9 | 1.4307 | EN 10028-7 EN 10216-5 EN 10217-7 EN 10222-5 EN 10269 EN 10272 EN 10253-4 | Plate Seamless tube Welded tube Forging Fasteners Bar Fittings | |
| X2CrNiN18–10 | 1.4311 | EN 10028-7 EN 10216-5 EN 10217-7 EN 10222-5 EN 10253-4 EN 10272 | Plate Seamless tube Welded tube Forging Fittings Bar | |
| X1CrNi25–21 | 1.4335 | EN 10028-7 EN 10216-5 | Plate Seamless tube | |
| X2CrNiMo17–12–2 | 1.4404 | EN 10028-7 EN 10216-5 EN 10217-7 EN 10222-5 EN 10253-4 EN 10269 EN 10272 | Plate Seamless tube Welded tube Forging Fittings Fasteners Bar | |
| X2CrNiMoN17–11–2 | 1.4406 | EN 10028-7 EN 10222-5 EN 10272 | Plate Forging Bar | |
| X2CrNiMoN17–13–3 | 1.4429 | EN 10028-7 EN 10216-5 EN 10217-7 EN 10222-5 EN 10253-4 EN 10269 EN 10272 | Plate Seamless tube Welded tube Forging Fittings Fasteners Bar | |
| X2CrNiMoN18–12–4 | 1.4434 | EN 10028-7 | Plate | |
| X2CrNiMo18–14–3 | 1.4435 | EN 10028-7 EN 10216-5 EN 10217-7 EN 10222-5 EN 10272 | Plate Seamless tube Welded tube Forging Bar | |
| X1CrNiMoN25–22–2 | 1.4466 | EN 10028-7 EN 10216-5 | Plate Seamless tube | |
| X6CrNiTi18–10 | 1.4541 | EN 10028-7 EN 10216-5 EN 10217-7 EN 10222-5 EN 10272 EN 10253-4 | Plate Seamless tube Welded tube Forging Bar Fittings | |
| X1NiCrMoCu31–27–4 | 1.4563 | EN 10028-7 EN 10216-5 EN 10217-7 EN 10272 | Plate Seamless tube Welded tube Bar | |
| X6CrNiMoTi17–12–2 | 1.4571 | EN 10028-7 EN 10216-5 EN 10217-7 EN 10222-5 EN 10253-4 EN 10269 EN 10272 | Plate Seamless tube Welded tube Forging Fittings Fasteners Bar |
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Bolting materials for use at lower temperatures
Cryogenic pressure vessel manufacturer and supplier
EN ISO 21028-1: Cryogenic vessels – Toughness requirements for materials at cryogenic temperature – Part 1: Temperatures below -80 °C
