Q460D
High-strength low-alloy structural steel · GB/T 1591-2008 (withdrawn; directly defines Q460D) · GB/T 1591-2018 (current; replaces the legacy designation with delivery-condition-specific Q460ND or Q460MD)
Q460D is a legacy GB/T 1591-2008 HSLA structural-steel designation combining nominal 460 MPa yield strength with D-quality Charpy toughness at −20 °C. It is not a complete designation under current GB/T 1591-2018: existing Q460D documentation must be resolved to Q460ND for normalized/normalizing-rolled material or Q460MD for TMCP material before procurement, qualification, or substitution.
- Legacy designationStandard status · GB/T 1591-2008 has been withdrawn and replaced by GB/T 1591-2018.
- 460 MPaNominal strength class · Minimum yield strength applies only in the lowest thickness range and decreases as section thickness increases.
- Charpy V-notch at −20 °CD quality · Legacy Q460D requires a minimum average longitudinal absorbed energy of 34 J for full-size specimens.
- Q460ND or Q460MDCurrent designations · The correct successor depends on whether the material is normalized/normalizing rolled or thermomechanically rolled.
- 550–720 MPa up to 100 mmLegacy tensile range · GB/T 1591-2008 specifies 530–700 MPa above 100 mm through 150 mm.
- State standard edition and delivery conditionCritical purchasing issue · An order stating only “Q460D to GB/T 1591” is technically ambiguous.
Overview
- Designation system
- Chinese GB/T yield-strength designation
- Product forms
- Steel plate, Steel strip, Structural sections, Steel bars
- Condition
- Legacy: as-rolled or controlled rolled, Legacy: normalized, normalizing rolled, or normalized and tempered, Legacy: thermomechanically rolled, optionally tempered, Current successor: Q460ND in normalized or normalizing-rolled condition, Current successor: Q460MD in TMCP condition, optionally tempered
- Density
- 7.85 g/cm³ (Representative density for structural steel; not a grade requirement in GB/T 1591.)
Designation and standard transition
Under GB/T 1591-2008, Q460D identifies a structural steel with a specified minimum yield-strength class of 460 MPa and quality grade D. The letter Q represents yield strength, 460 is the strength-class value in MPa, and D defines the impact-toughness quality level. The designation did not encode the delivery condition, even though chemistry, carbon equivalent, processing response and weldability could depend strongly on that condition.
| Legacy designation and condition | GB/T 1591-2018 designation | Meaning |
|---|---|---|
| Q460D, normalized or normalizing rolled | Q460ND | N identifies normalized or normalizing-rolled delivery; D remains the −20 °C toughness quality. |
| Q460D, TMCP | Q460MD | M identifies thermomechanical processing; D remains the −20 °C toughness quality. |
| Q460D without a recorded condition | Not uniquely resolvable | The material certificate, purchase specification or producer records must establish the actual delivery condition. |
Q460ND and Q460MD are not merely alternate spellings. They have different chemistry, carbon-equivalent limits, dimensional ranges and sensitivity to subsequent thermal processing.
Requirements for legacy Q460D to GB/T 1591-2008
| Element | Requirement, mass % |
|---|---|
| C | ≤0.20 |
| Si | ≤0.60 |
| Mn | ≤1.80 |
| P | ≤0.030 |
| S | ≤0.025 |
| Nb | ≤0.11 |
| V | ≤0.20 |
| Ti | ≤0.20 |
| Cr | ≤0.30 |
| Ni | ≤0.80 |
| Cu | ≤0.55 |
| N | ≤0.015 |
| Mo | ≤0.20 |
| B | ≤0.004 |
| Acid-soluble Al, Als | ≥0.015 |
At least one grain-refining element such as Al, Nb, V or Ti was to be used where grain refinement was required. The tabulated maxima do not mean that every alloying element is intentionally present. Product-analysis tolerances are governed separately by GB/T 222.
| Range, mm | Minimum yield strength, MPa | Tensile strength, MPa | Minimum elongation, % |
|---|---|---|---|
| ≤16 | 460 | 550–720 | 17 |
| >16–40 | 440 | 550–720 | 17 |
| >40–63 | 420 | 550–720 | 16 |
| >63–80 | 400 | 550–720 | 16 |
| >80–100 | 400 | 550–720 | 16 |
| >100–150 | 380 | 530–700 | 16 |
The legacy standard used lower yield strength ReL, with Rp0.2 permitted where no definite yield phenomenon occurred. For flat products at least 600 mm wide, tensile specimens were transverse; other products used longitudinal specimens, with the elongation minimum increased by one percentage point.
| Quality level | Test temperature | Specimen direction | Minimum average absorbed energy |
|---|---|---|---|
| D | −20 °C | Longitudinal | 34 J |
Applicable to nominal thickness of at least 6 mm or diameter of at least 12 mm. The standard specimen is 10 × 10 × 55 mm. For 7.5 mm and 5 mm subsize specimens, the required energy is respectively 75% and 50% of the full-size value.
| Delivery route | ≤63 mm | >63–120 mm | >120 mm |
|---|---|---|---|
| As-rolled or controlled rolled | 0.46 | 0.49 for >63–250 mm | Not specified above 250 mm |
| Normalized, normalizing rolled, or normalized and tempered | 0.53 | 0.54 | 0.55 through 250 mm |
| TMCP or TMCP plus tempering | 0.47 | 0.48 | 0.48 through 150 mm |
These markedly different limits illustrate why the legacy designation must not be interpreted without its delivery condition. For legacy TMCP Q460 with C ≤0.12%, Pcm could be specified instead of CEV; the maximum Pcm was 0.20%.
Current successor grades under GB/T 1591-2018
| Requirement | Q460ND | Q460MD |
|---|---|---|
| Delivery condition | Normalized or normalizing rolled | Thermomechanically processed; may include tempering |
| C | ≤0.20% | ≤0.16% for plate/strip; up to 0.18% permitted for sections and bars |
| Si | ≤0.60% | ≤0.60% |
| Mn | 1.00–1.70% | ≤1.70% |
| P / S | ≤0.030% / ≤0.025% | ≤0.030% / ≤0.025% |
| Nb | 0.01–0.05% | 0.01–0.05% |
| V | 0.01–0.20% | 0.01–0.12% |
| Ti | 0.006–0.05% | 0.006–0.05% |
| Cr / Ni / Cu | ≤0.30% / ≤0.80% / ≤0.40% | ≤0.30% / ≤0.80% / ≤0.40% |
| Mo | ≤0.10% | ≤0.20% |
| Acid-soluble Al, Als | ≥0.015% | ≥0.015% |
One or more grain-refining elements are used; their individual lower limits do not require all three of Nb, V and Ti to be present simultaneously. Consult the complete standard for nitrogen, boron and combination footnotes.
| Nominal thickness or diameter, mm | Minimum ReH, MPa | Rm, MPa | Minimum A, % |
|---|---|---|---|
| ≤16 | 460 | 540–720 for ≤100 mm | 17 |
| >16–40 | 440 | 540–720 for ≤100 mm | 17 |
| >40–63 | 430 | 540–720 for ≤100 mm | 17 |
| >63–80 | 410 | 540–720 for ≤100 mm | 17 |
| >80–100 | 400 | 540–720 for ≤100 mm | 17 |
| >100–150 | 380 | 530–710 for >100–200 mm | 17 |
| >150–200 | 370 | 530–710 for >100–200 mm | 17 |
| >200–250 | 370 | 510–690 | 17 |
GB/T 1591-2018 specifies upper yield strength ReH; Rp0.2 may be used when yielding is not distinct.
| Nominal thickness or diameter, mm | Minimum ReH, MPa | Rm, MPa | Minimum A, % |
|---|---|---|---|
| ≤16 | 460 | 540–720 for ≤40 mm | 17 |
| >16–40 | 440 | 540–720 for ≤40 mm | 17 |
| >40–63 | 430 | 530–710 | 17 |
| >63–80 | 410 | 510–690 | 17 |
| >80–100 | 400 | 500–680 | 17 |
| >100–120 | 385 | 490–660 | 17 |
The final thickness column extends to 150 mm for applicable sections and bars. Product availability and dimensional capability must be confirmed with the producer.
| Grades | Temperature | Longitudinal minimum | Transverse minimum |
|---|---|---|---|
| Q460ND and Q460MD | −20 °C | 40 J | 20 J |
Longitudinal testing is the default. Transverse testing may be agreed. These 2018 requirements must not be back-applied to steel certified only to the 2008 edition.
Weldability and thermal processing
Q460 strength makes hydrogen control, heat input, restraint and the actual ladle analysis more consequential than for ordinary structural steel. A compliant maximum CEV or Pcm is a specification limit, not a complete welding procedure. Preheat, interpass temperature, consumable strength and toughness, heat input and hydrogen level should be established by the applicable fabrication code and a qualified welding procedure, using the product certificate chemistry and actual joint thickness.
For Q460MD, hot forming or post-weld heat treatment above 580 °C may reduce the strength created by thermomechanical processing. Such treatment should not be applied without producer data, applicable-code acceptance and procedure qualification. Flame straightening may be permissible when performed under an appropriate technical procedure.
Cold forming capability cannot be inferred from the designation alone. The standard's optional 180° bend test uses a former diameter of 2a for nominal thickness up to 16 mm and 3a above 16 mm through 100 mm, where a is specimen thickness or diameter. This is a test requirement when ordered, not a universal fabrication bend radius.
Ordering, certification and acceptance
| Item | Why it matters |
|---|---|
| Standard edition | Q460D is valid under the withdrawn 2008 edition; the 2018 edition requires Q460ND or Q460MD. |
| Delivery condition | Controls designation, chemistry, CEV/Pcm limits, dimensional range and response to heating. |
| Product form and dimensions | Mechanical requirements, specimen direction and dimensional tolerances depend on product form and thickness. |
| Impact test details | State temperature, longitudinal or transverse orientation, specimen size and any project-specific energy requirement. |
| CEV or Pcm | Particularly important for welded fabrication and for distinguishing normalized from TMCP material. |
| Dimensional tolerance standard | GB/T 709 applies to plate and strip, GB/T 706 to hot-rolled sections, GB/T 702 to bars, and GB/T 11263 to H-sections and split T-sections. |
| Optional requirements | Specify bend testing, through-thickness properties, nondestructive examination, surface class and product analysis where required. |
| Inspection certificate | Require the applicable certificate type and verify heat number, grade, delivery condition, dimensions, chemistry, tensile results and impact results. |
Under GB/T 1591-2018, a normal inspection lot generally consists of the same designation, heat, specification and delivery condition, with a maximum mass of 60 t. Standard sampling includes one tensile specimen per lot and three Charpy specimens per lot. Chemical analysis is performed once per heat. Nondestructive examination is not automatic and must be agreed, including the method and acceptance level.
For existing stock marked Q460D, do not relabel it as Q460ND or Q460MD solely from mechanical-property similarity. Confirm the original standard edition and delivery condition from the mill certificate or traceable producer records.
Counterparts and substitution limits
The informative comparison annex in GB/T 1591-2018 associates Q460ND with ISO 630-3 S460ND and EN 10025-3 S460N, and Q460MD with ISO 630-3 S460MD and EN 10025-4 S460M. These are useful orientation points, not declarations of interchangeability. A substitution review must compare the governing product-standard editions, delivery condition, thickness range, chemistry and carbon equivalent, tensile and impact requirements, test orientation, tolerances, inspection documentation and project design rules.
Sources
- GB/T 1591-2018 — High strength low alloy structural steels: official standard recordState Administration for Market Regulation / Standardization Administration of China
- GB/T 1591-2018 — Low-alloy high-strength structural steelChina Baowu / Baosteel
- GB/T 1591-2008 — High strength low alloy structural steels: official withdrawn-standard recordState Administration for Market Regulation / Standardization Administration of China
- GB/T 1591-2008 — High strength low alloy structural steelsSteel Building Technology
- Professional Guide on Selection of Equivalent Steel Materials to European Steel Materials SpecificationsChinese National Engineering Research Centre for Steel Construction, Hong Kong Branch
Ask MetalMate about Q460D
Discussing: Q460D
AI assistant · Responses are generated and can contain errors; verify specifications before acting.