Gr. 8,06 Ni9DG, STPL 690,1.5682 Iron Type Low Temperature Steel Tube- SCALE STEEL.

​Gr.8 is 9Ni type low carbon quenching and tempering steel, listed in the American standard of low temperature pipe A333 and low temperature heat exchanger pipe A334 two standards.Nickel is the most effective element to improve the low temperature toughness of steel -- GR.8 contains 9% Ni, which ensures its good toughness and[SCALE STEEL] high strength at very low temperature, and its service temperature can be as low as -195℃.

National Standard
CHINA GB/T 18984-2016 06Ni9DG
AMERICA ASTM A333/A333M-11
ASTM A334/A334M-04a[SCALE STEEL] Grade 8
JAPAN JIS G 3460:2013
JIS G 3464:2013 STPL 690
GERMANY DIN EN 10216-4:2004 X10Ni9
1.5682

Component Specification
GRADE Grade  8 06Ni9DG STPL 690 1.5682
C ≤0.13 ≤0.10 ≤0.13 ≤0.13
Si 0.13~0.32 0.10~0.35 0.10~0.35 0.15~0.35
Mn ≤0.90 ≤0.90[SCALE STEEL] ≤0.90 0.30~0.80
P ≤0.025 ≤0.015 ≤0.030 ≤0.020
S ≤0.025 ≤0.008 ≤0.030 ≤0.010
Ni 8.4~9.6 8.5~9.5 8.5~9.5 8.5~9.5
Mo -- -- -- ≤0.10
Cu -- -- -- ≤0.30
V -- -- -- ≤0.05

Heat Treatment
Gr.8 Heat treated to control the microstructure as follows before delivery.

① quenching + tempering
Heat evenly to 800℃±15℃;Heat preservation, the heat preservation time is proportional to the thickness of 2min/mm, and not less than 15min;Immerse in circulating water and quench.
The steel tubes were reheated evenly[SCALE STEEL] to 565-605 ℃;Heat preservation, the heat preservation time is proportional to the thickness of 2min/mm, and not less than 15min;Air cooling, or water quenching with a cooling rate of not less than 165℃/h.
(2) secondary normalizing + tempering
Heat evenly to 900℃±15℃;Heat preservation, the heat preservation time is proportional to the thickness of 2min/mm, and not less than [SCALE STEEL]15min;Air cooling.
Reheated to 790℃±15℃;Heat preservation, the heat preservation time is proportional to the thickness of 2min/mm, and not less than 15min;Then air cooling.
Heat evenly to 565-605 ℃;Heat preservation, the heat preservation time is proportional to the thickness of 2min/mm, and not less than 15min;Air cooling, or water quenching with a cooling rate of not less than 165℃/h.

Tensile Property
strength of extension MPa ≥690
yield strength MPa ≥515

Elongation (longitudinal) % ≥22a
≥16b
A. Longitudinal strip test with a standard distance of 50mm and a wall thickness of ≥8mm, or all small-size samples tested with full section.
B. Standard round sample with a standard distance of 50mm or a smaller size sample with a standard distance of 4 times the diameter.

Impact toughness：
The minimum impact test temperature of the steel tube GR.8 is -195℃.The test results are determined by the average lateral expansion value of the impact sample relative to the notch.
Applications：
GR.8 is primarily used for the storage of structural materials for liquefied natural gas (LNG) terminals.LNG is stored at around -162 ° C and must be made from ultra-low temperature materials.Compared with other ultra-low temperature materials, GR.8 has lower cost than stainless steel and nickel-based alloy, higher strength than aluminum alloy and better low temperature toughness, and is currently the main material for large LNG storage tanks.