Q690E
690 MPa-class high-strength low-alloy structural steel; the exact material definition depends on the cited GB/T product標 · GB/T 16270-2009 — high-strength structural steel plate supplied quenched and tempered; current standard containing Q690E · GB/T 1591-2008 — withdrawn general HSLA structural-steel standard that also contained Q690E · GB/T 1591-2018 — current replacement for GB/T 1591-2008; the corresponding TMCP designation is Q690ME · GB/T 34560.4-2017 — current ISO-aligned specification for quenched-and-tempered high-yield-strength plate; related designation Q690QE
Q690E is an ambiguous GB/T designation rather than a single universal property set. It most commonly identifies quenched-and-tempered structural plate to GB/T 16270-2009, with 690 MPa minimum yield strength through 50 mm and longitudinal Charpy V-notch energy of at least 34 J at −40 °C. The same designation also existed in the withdrawn GB/T 1591-2008 general structural-steel standard, where chemistry, delivery route, thickness range and impact requirement differed. A purchase order, drawing or material certificate must therefore state the complete standard number and edition; “Q690E” alone is insufficient for technical acceptance or substitution.
- At least two GB/T specifications have used Q690EDesignation ambiguity · GB/T 16270-2009 and withdrawn GB/T 1591-2008 must not be treated as one material definition.
- GB/T 16270-2009Primary current plate specification · Covers quenched-and-tempered high-strength structural steel plate through 150 mm.
- 690 MPa minimum at t ≤ 50 mmSpecified yield strength · Under GB/T 16270-2009; the minimum decreases to 650 MPa above 50 through 100 mm and 630 MPa above 100 through 150 mm.
- KV2 ≥ 34 J longitudinal at −40 °CLow-temperature toughness · GB/T 16270-2009 Q690E requirement using a full-size specimen; reduced specimens use proportionally reduced criteria.
- Quenched and temperedDelivery condition · Required by GB/T 16270-2009 and fundamental to the specified strength–toughness combination.
- Q690MECurrent GB/T 1591 lineage · GB/T 1591-2018 replaced the former GB/T 1591-2008 Q690E designation with an explicit M suffix for thermomechanical processing.
Overview
- Designation system
- Chinese GB/T yield-strength designation system
- Product forms
- Quenched-and-tempered steel plate up to 150 mm under GB/T 16270-2009, Historically, plate, strip, sections and bars under GB/T 1591-2008
- Condition
- Quenched and tempered under GB/T 16270-2009, Legacy delivery conditions under GB/T 1591-2008, including thermomechanically processed material
- Density
- 7850 kg/m³ (Nominal engineering value for carbon and low-alloy steel; not a grade acceptance requirement.)
The standard number is part of the material designation
Q690E cannot be specified safely without a product standard. In GB/T 16270-2009 it is a quenched-and-tempered plate grade. In GB/T 1591-2008 it was a general high-strength low-alloy structural grade available in several product forms and delivery routes. Although both use Q for yield strength, 690 for the nominal strength level and E for the −40 °C quality class, their chemical limits, thickness ranges, impact energies and manufacturing conditions are different.
| Reference on document | Technical interpretation | Action |
|---|---|---|
| Q690E / GB/T 16270-2009 | Quenched-and-tempered structural steel plate | Apply the chemistry, thickness-dependent tensile properties and 34 J at −40 °C requirements of GB/T 16270. |
| Q690E / GB/T 1591-2008 | Legacy general HSLA structural steel | Confirm the original delivery condition, product form and certificate; this standard is withdrawn. |
| Q690E / GB/T 1591 with no year | Ambiguous and potentially outdated | Clarify the edition. The current GB/T 1591-2018 designation at this strength and quality level is Q690ME. |
| Q690E with no standard | Incomplete material callout | Do not accept or substitute solely from the short designation. |
As of October 1, 2026, GB/T 16270-2009, GB/T 1591-2018 and GB/T 34560.4-2017 are listed as current. A national-standard revision project is in progress to consolidate several quenched-and-tempered structural-plate standards, but it has not yet replaced them.
Q690E quenched-and-tempered plate to GB/T 16270-2009
This is the most important current definition of the short designation. The specification applies only to steel plate, not sections, bars or tubular products, and requires delivery after quenching followed by tempering. Its nominal scope extends through 150 mm thickness. Dimensions, shape, mass and tolerances are controlled through GB/T 709 unless otherwise agreed.
| Element | Requirement, mass % maximum | Comment |
|---|---|---|
| C | 0.20 | Maximum, not a target composition. |
| Si | 0.80 | |
| Mn | 1.80 | |
| P | 0.020 | E-quality limit. |
| S | 0.010 | E-quality limit. |
| Cu | 0.50 | May be added as required and reported. |
| Cr | 1.50 | May be added as required and reported. |
| Ni | 2.00 | May be added as required and reported. |
| Mo | 0.70 | May be added as required and reported. |
| B | 0.0050 | |
| V | 0.12 | |
| Nb | 0.06 | |
| Ti | 0.05 |
At least one grain-refining element among Nb, Ti, V and Al is required, with at least one present at 0.015% minimum; for aluminium this refers to acid-soluble Al. Total Al may be used instead at 0.018% minimum. The listed alloy values are specification maxima and do not describe a typical commercial heat.
| Nominal thickness t | Minimum yield strength ReH | Tensile strength Rm | Minimum elongation A |
|---|---|---|---|
| t ≤ 50 mm | 690 MPa | 770–940 MPa | 14% |
| 50 < t ≤ 100 mm | 650 MPa | 760–930 MPa | 14% |
| 100 < t ≤ 150 mm | 630 MPa | 710–900 MPa | 14% |
Transverse tensile specimens are specified. Rp0.2 may be used where a distinct yield phenomenon is absent.
| Test temperature | Specimen orientation | Minimum mean absorbed energy | Applicability |
|---|---|---|---|
| −40 °C | Longitudinal | 34 J | Full-size 10 × 10 × 55 mm specimens. |
| −40 °C | Longitudinal | 25.5 J | 10 × 7.5 × 55 mm reduced specimen; 75% of the full-size value. |
| −40 °C | Longitudinal | 17 J | 10 × 5 × 55 mm reduced specimen; 50% of the full-size value. |
The reported value is the arithmetic mean of three specimens. One individual result may be below the specified mean but not below 70% of it. Impact testing is not required by this standard for plate below 6 mm.
The E suffix is a test-quality designation, not a direct permissible-service-temperature rating. Structural design temperature still depends on section thickness, stress state, weld details, fatigue, restraint, applicable design code and required fracture-toughness assessment.
Legacy Q690E to GB/T 1591-2008 and its current successor
GB/T 1591-2008 also used Q690E, but for a broader HSLA structural-steel family covering plate, strip, sections and bars. That edition was superseded by GB/T 1591-2018. The current thermomechanically processed designation is Q690ME: Q690M is the steel grade and E is the quality class. Legacy stock, drawings and research publications frequently retain the shorter Q690E notation.
| Nominal thickness, diameter or side length | Minimum yield strength ReL | Tensile strength Rm | Minimum elongation A |
|---|---|---|---|
| ≤ 16 mm | 690 MPa | 770–940 MPa | 14% |
| >16–40 mm | 670 MPa | 770–940 MPa | 14% |
| >40–63 mm | 660 MPa | 750–920 MPa | 14% |
| >63–80 mm | 640 MPa | 730–900 MPa | 14% |
These values belong to the withdrawn GB/T 1591-2008 definition and must not be combined with the GB/T 16270 plate requirements.
| Characteristic | GB/T 1591-2008 Q690E | GB/T 16270-2009 Q690E |
|---|---|---|
| Standard status | Withdrawn | Current as of October 1, 2026 |
| Product scope | Plate, strip, sections and bars | Plate only |
| Defining delivery route | Condition-dependent; included TMCP routes but excluded Q&T requirements from the preceding edition | Quenched and tempered |
| Maximum C | 0.18% | 0.20% |
| Maximum P / S | 0.025% / 0.020% | 0.020% / 0.010% |
| Maximum thickness carrying Q690 tensile requirements | 80 mm | 150 mm |
| Full-size longitudinal impact requirement at −40 °C | 31 J | 34 J |
| Yield minimum at approximately 50 mm | 660 MPa for >40–63 mm | 690 MPa through 50 mm |
| Nominal thickness | Minimum yield strength ReH | Tensile strength Rm | Minimum elongation A |
|---|---|---|---|
| ≤ 16 mm | 690 MPa | 770–940 MPa | 14% |
| >16–40 mm | 680 MPa | 770–940 MPa | 14% |
| >40–63 mm | 670 MPa | 750–920 MPa | 14% |
| >63–80 mm | 650 MPa | 730–900 MPa | 14% |
Q690ME is explicitly a thermomechanically processed grade. Its E-quality Charpy requirement is 31 J longitudinal or 20 J transverse at −40 °C. GB/T 1591-2018 limits CEV to 0.49% for Q690M through its specified size range and gives a maximum Pcm of 0.25% where that weldability index is used.
Metallurgical and fabrication implications
The high strength is process-dependent. Quenched-and-tempered Q690E normally obtains its properties from a hardened microstructure subsequently tempered to recover toughness, while Q690ME obtains its balance through thermomechanical processing, potentially with accelerated cooling and tempering. These routes are not interchangeable merely because the room-temperature yield strengths are similar.
Welding procedure development must use the actual mill certificate composition, plate thickness, restraint, consumable hydrogen level, heat input and required joint toughness. The broad CEV ceilings in GB/T 16270-2009 are acceptance limits, not suitable default values for calculating preheat. Preheat, interpass temperature, heat input and any postweld heat treatment should be established through the applicable fabrication code and procedure qualification rather than copied from a generic grade datasheet.
| Operation | Principal concern | Practical control |
|---|---|---|
| Thermal cutting | A hard heat-affected edge and delayed hydrogen cracking may develop, particularly in thick or high-CEV plate. | Use qualified cutting parameters; inspect and condition edges where required by the fabrication specification. |
| Welding | Cold cracking, HAZ softening or embrittlement, weld-metal strength mismatch and loss of −40 °C toughness. | Qualify the complete WPS/PQR with the actual product route and required impact-test location. |
| Cold forming | High strength increases forming force, springback and local strain; GB/T 16270-2009 does not supply a universal bend radius. | Obtain producer recommendations and qualify severe forming operations on the ordered thickness. |
| Hot forming or stress relief | Heating can alter the Q&T or TMCP microstructure and invalidate guaranteed properties. | Do not apply an unqualified thermal cycle; obtain producer approval and perform appropriate re-testing. |
| Grinding and straightening | Local heating or surface damage can become fatigue or fracture initiation sites. | Use controlled procedures and comply with dimensional and surface acceptance requirements. |
Strength matching alone is not sufficient for welding consumable selection. Required weld-metal toughness, hydrogen classification, joint restraint, fatigue performance and whether undermatching is permitted by the design code must also be established.
Ordering, certification and inspection
| Item | What should be stated |
|---|---|
| Standard and edition | For example, GB/T 16270-2009. Do not order only “Q690E.” |
| Product and dimensions | Plate thickness, width, length, edge condition and applicable GB/T 709 tolerance class. |
| Designation and condition | Q690E, quenched and tempered, where GB/T 16270 applies. |
| Impact testing | Required temperature, specimen orientation, specimen size and any project-specific higher energy requirement. |
| Chemical reporting | Full heat analysis, CEV and CET if contractually requested. |
| Ultrasonic testing | Whether required, the inspection standard and acceptance class. |
| Through-thickness properties | Specify separately where Z-direction ductility is needed; it is not inherent in Q690E. |
| Surface condition | Applicable surface standard and limits on grinding or repair. |
| Weld repair | Whether permitted and the required approval, documentation and subsequent heat treatment. |
| Certification | Heat number, heat-treatment traceability, tensile and impact results, and required inspection-certificate format. |
Under GB/T 16270-2009, acceptance is by batch. A batch consists of plate from the same heat, designation and specification, made to the same heat-treatment system, with a thickness spread not exceeding 5 mm; batch mass is limited to 60 t. One transverse tensile specimen and three longitudinal Charpy specimens are used per batch. Ultrasonic examination is optional unless specified in the contract, in which case the method and acceptance grade must be stated.
Surface repair welding under GB/T 16270-2009 requires agreement between purchaser and supplier. If repair welding is performed after quenching and tempering, the plate is required to be quenched and tempered again.
Substitution and cross-standard comparison
S690QL, Q690QE and Q690ME are useful comparison grades but should not be declared equivalent to Q690E without reviewing the governing product standards. Differences can include delivery route, chemical maxima, CEV or Pcm limits, thickness-dependent strength, tensile specimen orientation, Charpy energy and orientation, permissible dimensions, heat-treatment rules and inspection documentation.
| Check | Reason |
|---|---|
| Exact standard and edition | Determines the legal and technical material definition. |
| Product form and thickness | Requirements are not transferable from plate to section, bar or tubular product. |
| Delivery condition | Q&T and TMCP steels may respond differently to welding, forming and heat treatment. |
| Yield and tensile ranges at ordered thickness | The nominal 690 designation does not guarantee 690 MPa at every thickness. |
| Impact test temperature, energy, orientation and specimen size | An E suffix does not establish identical toughness requirements across standards. |
| Heat analysis, CEV/Pcm and grain-refining practice | Controls weldability and may differ substantially between specifications. |
| Inspection, UT and through-thickness requirements | These are often optional or separately specified. |
| Design-code approval | Material acceptance may depend on code recognition rather than property similarity alone. |
Sources
- GB/T 16270-2009 — High strength structural steel plates in the quenched and tempered condition: official standard recordState Administration for Market Regulation / Standardization Administration of China
- GB/T 16270-2009 — High strength structural steel plates in the quenched and tempered conditionGB/T standard reproduction/English translation
- 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 — High strength low alloy structural steelsBaosteel-hosted standard reproduction
- GB/T 1591-2008 — High strength low alloy structural steelsStandard reproduction/English translation
- GB/T 34560.4-2017 — Structural steels, Part 4: technical delivery conditions for high-yield-strength quenched-and-tempered structural steel platesState Administration for Market Regulation / Standardization Administration of China
- Chinese Steel Materials — Supplementary technical guideChinese National Engineering Research Centre for Steel Construction, Hong Kong Branch
- 2025 national-standard revision project notice, project 20251175-T-605Standardization Administration of China
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