The main difference between S690QL and S690QL1 is their impact toughness at lower temperatures: S690QL is tested at -40°C, while S690QL1 offers superior toughness for colder applications, tested at -60°C, making it better for extreme cold environments like polar construction or deep-sea platforms, despite both being high-strength (690 MPa yield) quenched & tempered steels.
S690QL
Toughness: Good, suitable for temperatures down to -40°C.
Applications: General heavy machinery, bridges, cranes, offshore structures in temperate to colder zones.
S690QL1
Toughness: Excellent, tested at -60°C, offering significantly improved impact resistance in extreme cold.
Applications: Critical projects in polar regions, low-temperature gas storage, deep-sea installations, military equipment, and harsh arctic machinery.
In essence: Think of it as a progressive toughness scale: S690Q (basic -20°C) -> S690QL (better -40°C) -> S690QL1 (best -60°C), with the 'L' indicating lower-temperature impact testing for better performance in the cold. Both are excellent, high-strength, weldable structural steels, but the 'L1' grade provides enhanced cold-weather durability.
S690QL, S690QL1 steel plate chemical composition (analysis of finished products):
| C | Si | Mn | P | S | Ni | Cr | Mo | Cu | Nb | V | Ti | N | Zr | B |
| ≤0.2 | ≤0.8 | ≤1.7 | ≤0.025 | ≤0.015 | ≤2 | ≤1.5 | ≤0.7 | ≤0.5 | ≤0.06 | ≤0.12 | ≤0.05 | ≤0.015 | ≤0.15 | ≤0.005 |
Mechanical properties, yield tensile strength of S690QL, S690QL1 steel:
S690QL, S690QL1 steel plate thickness 3-50mm
ReH(MPa)≥690
Rm(MPa)770-940
A(%)≥14
Akv(J)≥30 longitudinal;
Horizontal: Akv≥27J
S690QL, S690QL1 steel plate thickness>50-100mm
ReH(MPa)≥650
Rm(MPa)760-930
A(%)≥14
Akv(J)≥30 longitudinal;
Horizontal: Akv≥27J
S690QL, S690QL1 steel plate thickness>100-150mm
ReH(MPa)≥630
Rm(MPa)710-900
A(%)≥14
Akv(J)≥30 longitudinal;
Horizontal: Akv≥27J
S690QL1 impact temperature -60℃; S690QL impact temperature -40℃.
S690QL, S690QL1 steel plate production process:
1. Raw materials (scrap steel, pig iron and molten iron)
2. Electric furnace (100-ton electric arc furnace smelting), converter
3. LF furnace molten steel refining treatment
4. Vacuum treatment of molten steel in VD or VOD furnace
5. Die casting (a variety of key-type die casting lines) or continuous casting (large slab continuous casting machine); (one ingot remelting 50 tons slab type electroslag furnace)
6. Heating (continuous furnace and soaking furnace)
7. Steel plate rolling (4100 and 4200mm mills)
8. Heat treatment of steel plate (normalizing and tempering)
9. Steel plate cutting inspection
10. Storage
