1.5680, X12Ni5 - low-temperature pressure equipment nickel steel

1.5680, X12Ni5, 12Ni19, A645, 1.5637 - low-temperature pressure equipment steel according to EN 10028-4, ISO 9328-4 and ASTM A645/A645M-10

1.5680, A645 Grade A, X12Ni5, 12Ni19 – description

1.5680 is a nickel steel with vanadium and manganese alloying additions for welded pressure equipment working in cryogenic temperatures.

1.5637 is a related steel with less nickel, used down to -100°C.

The related ASTM steel A645 contains more alloying additions, has slightly better low-temperature strength properties and is used, according to API 620, for pressure containers for ethylene, LPG or LNG storage. A645 Grade A steel is designed for ethylene, while A645 Grade B is better for LPG/LNG containers.

Steel is susceptible to magnetisation. If residual magnetism would be detrimental to the final product, the use of magnets should be avoided once heat treatment has been completed.

1.5680 steel is delivered in following conditions:

• Normalised (+N)
• Normalised and relieved (+NT)
• Hardened and tempered (+QT)

Applications

Steel used for welded pressure equipment operating at sub-zero temperatures down to -120°C, especially containing LEG, LPG and LNG.

12Ni19, 1.5680, A645, X12Ni5 - physical and mechanical properties

Room temperature physical properties for annealed and aged bars:

• Density: 7.9 g/cm³
• Thermal conductivity: 29.3 W/m⋅K
• Linear expansion coefficient: 10.3 *10^-6m/(m*K)

Mechanical properties of 1.5680 steel:

• Yield strength: >390 MPa
• Yield strength (when D: 30-50mm): >380 MPa
• Tensile strength: 530-710 MPa
• Elongation: >20%

Mechanical properties of 1.5637 steel:

• Yield strength: >345 MPa
• Yield strength (when D: 30-50mm): >355 MPa
• Tensile strength: 490-640 MPa
• Elongation: >22%

Mechanical properties of A 645 Grade A:

• Yield strength: >450 MPa
• Tensile strength: 655-795 MPa
• Elongation: >20%

Mechanical properties of A 645 Grade B:

• Yield strength: >590 MPa
• Tensile strength: 690-830 MPa
• Elongation: >20%

Coefficient of thermal expansion of 1.5680 steel and temperature (linear):

• -195°C: 8.7 *10^-6m/(m*K)
• -170°C: 8.9 *10^-6m/(m*K)
• -120°C: 9.5 *10^-6m/(m*K)
• -50°C: 9.9 *10^-6m/(m*K)
• -20°C: 10.1 *10^-6m/(m*K)

Impact energy KV for longitudial 1.5680 test pieces, applicable to sheets, plates and forgings:

• 0°C: >70 J
• -20°C: >70 J
• -60°C: >65 J
• -80°C: >60 J
• -100°C: >50 J
• -120°C: >40 J

Impact energy KV for transverse 1.5680 test pieces, applicable to sheets, plates and forgings:

• 0°C: >50 J
• -20°C: >50 J
• -60°C: >45 J
• -80°C: >40 J
• -100°C: >30 J
• -120°C: >27 J

Impact energy KV for longitudial 1.5680 test pieces, applicable to seamless pipes:

• Wall thickness: <25 mm
  • 0°C: >70 J
  • -20°C: >70 J
  • -60°C: >65 J
  • -90°C: >55 J
  • -100°C: >50 J
  • -110°C: >45 J
  • -120°C: >40 J
• Wall thickness: 25-40 mm
  • 0°C: >70 J
  • -50°C: >65 J
  • -60°C: >60 J
  • -90°C: >50 J
  • -100°C: >45 J
  • -110°C: >40 J

Impact energy KV for transverse 1.5680 test pieces, applicable to seamless pipes:

• 0°C: >50 J
• -40°C: >45 J
• -60°C: >45 J
• -90°C: >35 J
• -100°C: >30 J
• -110°C: >30 J
• -120°C: >27 J

Impact energy KV for longitudial 1.5637 test pieces, applicable to sheets, plates and forgings:

• 0°C: >65 J
• -40°C: >55 J
• -60°C: >50 J
• -80°C: >45 J
• -100°C: >40 J

Impact energy KV for transverse 1.5637 test pieces, applicable to sheets, plates and forgings:

• 0°C: >50 J
• -40°C: >35 J
• -60°C: >35 J
• -80°C: >30 J
• -100°C: >27 J

Heat treatment, working and machining

Typical 1.5680 heat treatment according to EN 10222-3:

• Hardening: 800-850 °C; water or oil cooling
• Tempering: 580-660 °C; air or water cooling
• Normalizing annealing: 800-850 °C; air cooling
• Stress relieving: 580-660 °C; air or water cooling

Typical 1.5637 heat treatment according to EN 10028-4:

• Hardening: 820-870 °C; water or oil cooling
• Tempering: 580-640 °C; air or water cooling
• Normalizing annealing: 830-880 °C; air cooling
• Stress relieving: 580-640 °C; air or water cooling

Typical A645 heat treatment:

• Hardening: 855-915 °C; water quenching
• Intermediate heat treatment: 690-760 °C; water cooling
• Tempering: 620-665 °C; water or air cooling

Weldability

1.5680 stell belongs to weldability group 9.2 according to ISO/TR 20172 and can be welded using a variety of methods. Below are the mechanical properties of the welds depending on the welding method chosen, according to the manufacturer The Lincoln Electric Company:

SMAW shielded electrode ENiCrMo-3 (Lincoln® NiCro 60/20):

• Elongation: >44% %
• Tensile strength: >770 MPa
• Yield strength: >510 MPa
• Impact energy KV. -196°С: >92 J

SMAW shielded electrode ENiCrMo-4 (Lincoln® NiCroMo 60/16):

• Elongation: >40 %
• Tensile strength: >800 MPa
• Yield strength: >500 MPa
• Impact energy KV. -196°С: >50 J

SMAW shielded electrode E316LMn-15 (Lincoln® Jungo 4455)

• Elongation: >35 %
• Tensile strength: >650 MPa
• Yield strength: >460 MPa
• Impact energy KV. -196°С: >50 J

MMA shielded electrode ENiCrMo-6 (Lincoln® Selectarc B96)

• Elongation: >35 %
• Tensile strength: >690 MPa
• Yield strength: >420 MPa
• Impact energy KV. -196°С: >70 J

GTAW with the ER316LMn welding wire (Lincoln® LNT/LNM 4455) in argon shielding:

• Elongation: >35 %
• Tensile strength: >650 MPa
• Yield strength: >430 MPa
• Impact energy KV. -196°С: >75 J

GTAW with the ER316LMn welding wire (Lincoln® LNT/LNM 4455) in mixed Ar + CO₂ shielding:

• Elongation: >30 %
• Tensile strength: >600 MPa
• Yield strength: >400 MPa
• Impact energy KV. -196°С: >50 J

We deliver this steel alloy as:

• Bars according to ASTM A645/A645M-10(2022),  EN 10028-4:2017-09, ISO 9328-4:2018 and other standards.