Grade Definition and Equivalent Grades
S460Q is a quenched and tempered high-strength structural steel plate supplied to the European standard EN 10025-6. The designation is built from three parts. The letter S shows that the steel is intended for structural, load-bearing components. The number 460 states that the minimum yield strength reaches 460 MPa for plate thicknesses up to 50 mm. The letter Q identifies the delivery condition as quenched and tempered, the heat treatment that gives the grade its balance of strength and toughness.
In the Chinese national grade system the closest equivalent is Q460D, which has comparable tensile properties and a similar chemical composition. Q460C is sometimes considered as well, but its impact performance differs slightly, so the intended service temperature should be reviewed before the two grades are treated as interchangeable in a welded structure.
Chemical Composition
The composition of S460Q is controlled to balance strength with weldability. The maximum contents of the main elements are:
Carbon (C) ≤ 0.22%
Silicon (Si) ≤ 0.86%
Manganese (Mn) ≤ 1.8%
Impurity elements are tightly limited to protect toughness and weldability:
Phosphorus (P) ≤ 0.03%
Sulfur (S) ≤ 0.017%
Alloying elements such as chromium (≤ 1.6%), molybdenum (≤ 0.74%) and nickel (≤ 2.1%) may also be present according to the production route. The grade is additionally required to contain at least 0.010% of grain-refining elements, with aluminium the element most often used; a total aluminium content of at least 0.013% is normally needed to satisfy the soluble aluminium requirement. Grain refinement is important because it raises both strength and low-temperature toughness at the same time.
Mechanical Properties
Because the quenched and tempered condition is achieved through the full plate thickness, properties fall gradually as the section becomes thicker rather than dropping abruptly. Minimum values by thickness are summarised below.
| Thickness range | Minimum yield strength ReH | Tensile strength Rm | Minimum elongation A |
|---|---|---|---|
| 3–50 mm | 460 MPa | 550–720 MPa | 17% |
| 50–100 mm | 440 MPa | 550–720 MPa | 17% |
| 100–150 mm | 400 MPa | 500–670 MPa | 17% |
Impact toughness is verified by the Charpy V-notch test at −20 °C, where the minimum absorbed energy is 30 J. That level of toughness is sufficient for general low-temperature service and reduces the risk of brittle fracture in stiff, highly restrained details.
Delivery Range and Through-Thickness Performance
Standard delivery sizes for S460Q plate are 3–350 mm in thickness, 1500–4200 mm in width and 3000–18000 mm in length. Where thick plate is welded into restrained joints, through-thickness properties can be specified as Z15, Z25 or Z35 to control the risk of lamellar tearing. Internal quality can be checked by ultrasonic testing in accordance with EN 10160, and the surface can be shot blasted or painted where corrosion protection is required.
Processing Performance and Application Areas
S460Q has good weldability and formability. For plate thicker than 30 mm, preheating before welding is recommended so that welding stress is reduced and cold cracking is avoided. The quenched and tempered condition also gives reliable cutting and machining behaviour, so the plate can be cut, bent and formed into structural components without an obvious loss of properties.
Engineering machinery: crane booms, excavator arms, hydraulic supports and mining shovels.
Construction and infrastructure: beams, columns and frames of large buildings, and main girders of bridges.
Other heavy-duty work: transmission towers, oil derricks, heavy vehicle chassis, and shafts or connecting rods carrying large loads.
Frequently Asked Questions
Q: Which domestic steel grade is roughly equivalent to S460Q?
It is approximately equivalent to the national standard grade Q460D, which has similar tensile properties and chemical composition; Q460C can also be considered in some cases, with slight differences in impact performance.
Q: What do the letters and the number in S460Q mean?
S stands for structural steel, 460 indicates a minimum yield strength of 460 MPa for plate up to 50 mm thick, and Q denotes the quenched and tempered delivery condition.
Q: What are the low-temperature impact requirements?
The grade is tested with a Charpy V-notch specimen at −20 °C and must absorb at least 30 J, which suits general low-temperature service and limits brittle fracture risk.
Q: How does thickness affect the mechanical properties?
Minimum yield strength falls with thickness, from 460 MPa for 3–50 mm plate to 440 MPa for 50–100 mm and 400 MPa for 100–150 mm, while tensile strength and elongation requirements remain comparable.
Q: What are the Z15, Z25 and Z35 designations?
They specify through-thickness properties of the plate, graded by the minimum reduction of area in the thickness direction, and are used in thick welded joints where lamellar tearing is a concern.
Q: Is preheating required before welding?
For plate thicker than 30 mm, preheating is recommended to lower welding stress and avoid cold cracking in the weld joint.