S550Q and S620Q are designations for high-yield strength structural steel plates, part of the EN 10025-6 standard, specified for quenched and tempered (Q) delivery, offering excellent strength, toughness, and weldability for demanding applications like heavy machinery, cranes, and bridges, with 'S' for structural, the number indicating minimum yield strength (550 MPa for S550Q, 620 MPa for S620Q), and 'Q' for the heat treatment.
Chemical Composition
|
S550QChemical Composition |
||||||||
|
Grade |
The Element Max (%) |
|||||||
|
C |
Si |
Mn |
P |
S |
N |
B |
Cr |
|
|
S550 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 |
|
|
|
S620QChemical Composition |
||||||||
|
Grade |
The Element Max (%) |
|||||||
|
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 |
|
|
Mechanical Property
|
Grade |
S620QMechanical Property |
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|
Thickness |
Yield |
Tensile |
Elongation |
Min Impact Energy
|
||
|
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 |
S550QMechanical Property |
|||||
|
Thickness |
Yield |
Tensile |
Elongation |
Min Impact Energy
|
||
|
S550 Q |
mm |
Min Mpa |
Mpa |
Min % |
-20 |
30J |
|
3<t≦50 |
550 |
640-820 |
16 |
-20 |
30J |
|
|
50<t≦100 |
530 |
640-820 |
16 |
-20 |
30J |
|
|
100<t≦150 |
490 |
590-770 |
16 |
-20 |
30J |
|
Key Characteristics:
High Strength: Both offer superior yield and tensile strength, essential for load-bearing structures.
Quenched & Tempered (Q): This heat treatment process gives them their high strength and fine-grained microstructure.
Good Weldability & Toughness: Despite high strength, they maintain good ductility and impact toughness, even at low temperatures.
Applications: Used in heavy industry, construction, cranes, bridges, and offshore structures.
Naming Convention (EN 10025-6):
S: Structural steel.
550/620: Minimum yield strength in megapascals (MPa).
Q: Quenched and tempered delivery condition.
In Simple Terms:
Think of them as tough, strong steel plates used when regular steel isn't strong enough, suitable for heavy-duty jobs where high stress and impact are expected. S620Q is stronger than S550Q.
