S620Q and S690Q are high-yield strength structural steel grades, defined by the European standard EN 10025-6, used in quenched and tempered (Q) conditions for heavy-duty applications, offering superior strength-to-weight ratios for cranes, bridges, construction, and heavy machinery, with S690Q having a higher minimum yield strength (around 690 MPa) than S620Q (around 620 MPa) for comparable thicknesses, making them energy-efficient for leaner designs.
Chemical Composition
|
S620QChemical Composition |
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|
Grade |
The Element Max (%) |
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|
C |
Si |
Mn |
P |
S |
N |
B |
Cr |
|
|
S620 Q |
0.20 |
0.80 |
1.70 |
0.020-0.025 |
0.010-0.015 |
0.015 |
0.005 |
1.50 |
|
Cu |
Mo |
Nb |
Ni |
Ti |
V |
Zr |
|
|
|
0.50 |
0.70 |
0.06 |
2.0 |
0.05 |
0.12 |
0.15 |
|
|
| Grade | C % | Si % | Mn % | P % | S % | N % | B % | Cr % |
| S690Q | 0.200 | 0.800 | 1.700 | 0.025 | 0.015 | 0.015 | 0.005 | 1.500 |
| Cu % | Mo % | Nb % | Ni % | Ti % | V % | Zr % | ||
| 0.500 | 0.700 | 0.060 | 2.000 | 0.050 | 0.120 | 0.150 |
Mechanical Property
|
Grade |
S620QMechanical Property |
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|
Thickness |
Yield |
Tensile |
Elongation |
Min Impact Energy
|
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|
S620 Q |
mm |
Min Mpa |
Mpa |
Min % |
-20 |
30J |
|
3<t≦50 |
620 |
700-890 |
15 |
-20 |
30J |
|
|
50<t≦100 |
580 |
700-890 |
15 |
-20 |
30J |
|
|
100<t≦150 |
560 |
650-830 |
15 |
-20 |
30J |
|
| Grade | Thickness | Min Yield | Tensile | Elongation | Min Impact Energy | |
| S690Q | 8mm-50mm | Min 690Mpa | 770-940Mpa | 14% | -20 | Min 30J |
| 51mm-100mm | Min 650Mpa | 760-930Mpa | 14% | -20 | Min 30J | |
| 101mm-150mm | Min 630Mpa | 710-900Mpa | 14% | -20 | Min 30J |
Key Characteristics
High Strength: Both grades offer very high yield strength, crucial for load-bearing structures.
Quenched & Tempered (Q): They undergo heat treatment (quenching and tempering) to achieve their properties, improving toughness and strength.
Standard: Covered under EN 10025-6 (and ISO 630-4), specifying technical delivery conditions.
Applications: Ideal for heavy construction, cranes, mining equipment, bridges, and energy-efficient structures.
Key Difference: Strength Level
S620Q: Minimum yield strength around 620 MPa (megapascals).
S690Q: Minimum yield strength around 690 MPa, making it stronger.
Typical Mechanical Properties (S690Q Example)
Yield Strength: Varies with thickness (e.g., 690 MPa for 8-50mm).
Tensile Strength: Higher than yield (e.g., 770-940 MPa for 8-50mm).
Impact Energy: Often tested at -20°C (e.g., 30 Joules minimum).
In essence, if you need high-strength steel for demanding applications, S620Q and S690Q provide excellent strength, with S690Q offering an even higher strength class for more efficient designs.
