Q345R
Manganese-alloyed pressure-equipment steel plate and strip · GB/T 713.2-2023 — Steel plate, sheet and strip for pressure equipment, Part 2: Non-alloy and alloy steel with specified temperature properties · GB/T 713.1-2023 — General requirements for pressure-equipment plate, sheet and strip
Q345R is a weldable manganese pressure-equipment steel whose current material requirements are defined by GB/T 713.1 and GB/T 713.2. The nominal 345 MPa yield level applies only through 16 mm; strength, impact requirements and design-use conditions vary with thickness. The purchase specification must identify the delivery condition and any required ultrasonic examination, lower-temperature impact test, through-thickness properties, HIC testing or elevated-temperature tensile testing.
- GB/T 713.2-2023 with GB/T 713.1-2023Current material specification · Both took effect on March 1, 2024, replacing the relevant provisions of GB 713-2014.
- 345 MPa minimum at 3–16 mmNominal yield level · The specified minimum decreases progressively to 265 MPa for thicknesses over 150 through 250 mm.
- 3–250 mm single-rolled plate; strip/cut plate ≤25.4 mmStandard product range · The standard's stated application range is pressure equipment operating at temperatures not lower than −20 °C, but design-code limits can be more restrictive.
- Charpy V-notch at 0 °CStandard impact condition · A −20 °C test with the same specified energy may be ordered; thin-product specimen rules still apply.
- Hot rolled, normalized rolled, normalized, or normalized and temperedDelivery conditions · The governing pressure-vessel design code may require normalization even though several conditions are permitted by the material standard.
- HIC resistance is an additional requirementNot inherently HIC-qualified · For wet-H₂S or other hydrogen-damage service, the required HIC qualification level and test conditions must be stated in the contract.
Overview
- Designation system
- Chinese GB designation based on minimum yield strength and pressure-vessel application
- Product forms
- Single-rolled plate, 3–250 mm, Hot-rolled strip and cut-to-length plate from coil, up to 25.4 mm
- Condition
- Hot rolled, Normalized rolled, Normalized, Normalized and tempered
- Density
- 7.85 g/cm³ (Conventional density used for calculating steel-plate mass; not a grade-specific acceptance property.)
Designation and governing standard
In Q345R, “Q” identifies yield strength, “345” is the specified minimum yield strength in MPa for the thinnest plate range, and “R” identifies steel for pressure vessels or pressure equipment. It is a standardized grade, not a trade name. It should be ordered to the current two-part system: GB/T 713.1 supplies the general manufacturing, dimensional, inspection and certification provisions, while GB/T 713.2 contains the grade-specific chemistry, delivery conditions and mechanical requirements.
A drawing or purchase order that states only “GB/T 713” should be clarified. For new procurement, identify GB/T 713.2-2023 and Q345R, together with the applicable general requirements of GB/T 713.1-2023.
Chemical composition
| Element | Requirement, mass % | Technical significance |
|---|---|---|
| C | ≤0.20 | May be increased to ≤0.22 for plate over 60 mm. |
| Si | ≤0.55 | Deoxidizing and strengthening element. |
| Mn | 1.20–1.70 | Principal alloying and strength contribution. |
| P | ≤0.025 | Controlled because of adverse effects on toughness and segregation. |
| S | ≤0.010 | Controlled for cleanliness, toughness and through-thickness performance. |
| Cu | ≤0.30 | Residual-element limit. |
| Ni | ≤0.30 | Residual-element limit. |
| Cr | ≤0.30 | Residual-element limit. |
| Mo | ≤0.08 | Residual-element limit. |
| Nb | ≤0.050 | May be intentionally added as a microalloying element. |
| V | ≤0.050 | May be intentionally added as a microalloying element. |
| Ti | ≤0.030 | May be intentionally added as a microalloying element. |
| Nb + V + Ti | ≤0.120 | Total microalloy content limit for Q345R. |
| Cu + Ni + Cr + Mo | ≤0.70 | Combined residual-element limit. |
| Total aluminium | No specified Q345R limit | Unlike the previous GB 713-2014 composition table, the 2023 Q345R row does not specify a minimum aluminium content. |
Nb, V and Ti contents are to be reported on the quality certificate when added. Product-analysis tolerances are governed by GB/T 713.1.
GB/T 713.2 permits a carbon-equivalent requirement to be added for Q345R at the purchaser's request, but it does not impose one universal carbon-equivalent limit. Weldability assessments should therefore use the actual heat analysis and the carbon-equivalent definition specified by the project, rather than assuming a generic value from the grade name.
Room-temperature mechanical and impact requirements
| Nominal thickness t, mm | Tensile strength Rm, MPa | Minimum yield strength, MPa | Minimum elongation, % | Charpy V-notch at 0 °C, minimum J |
|---|---|---|---|---|
| 3 ≤ t ≤ 16 | 510–640 | 345 | 21 | 34 |
| 16 < t ≤ 36 | 500–630 | 325 | 21 | 41 |
| 36 < t ≤ 60 | 490–620 | 315 | 21 | 41 |
| 60 < t ≤ 100 | 490–620 | 305 | 20 | 41 |
| 100 < t ≤ 150 | 480–610 | 285 | 20 | 41 |
| 150 < t ≤ 250 | 470–600 | 265 | 20 | 40 |
Yield is reported as lower yield strength ReL or, where a distinct yield phenomenon is absent, 0.2% proof strength Rp0.2. Impact values are average requirements subject to the standard's individual-value and reduced-size specimen provisions.
The designation must not be interpreted as guaranteeing 345 MPa yield strength at every thickness. The fall in specified yield and tensile strength through the thickness ranges is important for design calculations, material comparison and substitution. Plate thickness also affects impact specimen availability: very thin plate cannot automatically be represented by a full-size 10 mm Charpy specimen, and the applicable thin-product provisions must be checked.
| Thickness | Test | Mandrel diameter D |
|---|---|---|
| t ≤ 16 mm | 180° bend | 2a |
| t > 16 mm | 180° bend | 3a |
a is specimen thickness. For plate over 60 mm, omission of the bend test is permitted only by supplier-purchaser agreement and when stated in the contract.
Delivery condition and pressure-vessel use
GB/T 713.2 permits Q345R in the hot-rolled, normalized-rolled, normalized, or normalized-and-tempered condition. These alternatives are not interchangeable in every pressure-vessel application. The material purchase condition must be coordinated with the design code, component thickness, forming route and any subsequent heat treatment.
| Application | Required use condition |
|---|---|
| Inner shell of a multilayer vessel | Q345R is to be used normalized. |
| Vessel shell with thickness over 36 mm | Q345R is to be used normalized. |
| Other pressure parts such as flanges, tubesheets and flat heads over 60 mm | Q345R is to be used normalized. |
| Q345R plate over 50 mm | Normalized and tempered condition may be used instead of normalized where permitted by the code. |
These are pressure-vessel design-code requirements, not changes to the delivery-condition options listed in GB/T 713.2. Other construction codes or project specifications may impose different rules.
The −20 °C stated in the scope of GB/T 713.2 is not a blanket minimum design-metal temperature for every Q345R component. Applicable temperature limits depend on thickness, impact-test condition, stress state, heat treatment and the governing equipment code.
Specified elevated-temperature strength
For plate over 20 mm, elevated-temperature tensile testing may be ordered. The test temperature must be stated in the contract. These material-test values are not allowable stresses; allowable stress is established separately by the governing pressure-equipment design code.
| Thickness, mm | 200 °C | 250 °C | 300 °C | 350 °C | 400 °C | 450 °C |
|---|---|---|---|---|---|---|
| >20–36 | 255 | 235 | 215 | 200 | 190 | 180 |
| >36–60 | 240 | 220 | 200 | 185 | 175 | 165 |
| >60–100 | 225 | 205 | 185 | 175 | 165 | 155 |
| >100–150 | 220 | 200 | 180 | 170 | 160 | 150 |
| >150–250 | 215 | 195 | 175 | 165 | 155 | 145 |
These are specified elevated-temperature yield/proof-strength minima associated with optional testing under the material standard. They should not be substituted for code allowable-stress tables.
Fabrication and welding implications
Q345R is commonly fusion welded, but the grade designation alone does not define a welding procedure. Procedure qualification should account for the actual heat chemistry, plate thickness, joint restraint, hydrogen level, heat input, ambient temperature, required impact toughness and any postweld heat treatment. Consumables must be selected to satisfy the applicable construction code and the required weld-metal and heat-affected-zone properties, rather than merely to overmatch the room-temperature tensile strength.
Cold or hot forming can alter the as-supplied microstructure and toughness. Where substantial forming or a fabrication heat treatment is planned, the purchaser and fabricator should verify whether the final condition remains compatible with the material certificate, qualified procedure and governing pressure-equipment code. This is especially important for normalized or normalized-and-tempered plate and for fabrication cycles approaching the original tempering temperature.
Q345R is not intrinsically corrosion resistant. Corrosion allowance, lining, cladding, environmental cracking resistance and hydrogen-service qualification are separate engineering decisions.
Inspection and additional requirements
| Item | Base-standard position | What to specify when required |
|---|---|---|
| Impact at −20 °C | Purchaser option for Q345R | State −20 °C Charpy testing; the specified energy remains that of the applicable thickness range. |
| Ultrasonic examination | Available as a purchaser requirement | State examination of each plate, NB/T 47013.3 edition, scanning requirements and acceptance grade. |
| Through-thickness properties | Optional | State GB/T 5313 and the required Z-quality class where lamellar-tearing resistance is needed. |
| HIC resistance | Additional requirement | State HIC testing, solution and exposure conditions, specimen orientation and acceptance level under the applicable appendix or project specification. |
| Drop-weight test | Optional | State test temperature and acceptance requirement. |
| Elevated-temperature tensile test | Optional for plate over 20 mm | State test temperature and required ReL or Rp0.2. |
| Carbon equivalent | By purchaser request and agreement | State formula, maximum value and whether based on ladle or product analysis. |
| Additional heat-treatment simulation | Not automatic | Define simulated PWHT cycles and post-simulation testing when required by fabrication or project rules. |
An instruction such as “Q345R with UT” is incomplete unless the method, examination extent and acceptance grade are stated.
Standard batch acceptance groups plate by designation, heat, thickness, rolling condition and heat-treatment system. For plate over 40 mm, the impact-specimen axis is located at one-quarter thickness. The quality certificate should be checked for the standard edition, grade, heat number, dimensions, delivery condition, ladle analysis, microalloy additions, tensile and impact results, bend result where applicable, and all ordered supplementary examinations.
Procurement checklist
| Order field | Recommended content |
|---|---|
| Standard and grade | GB/T 713.2-2023 Q345R, applying GB/T 713.1-2023 general requirements |
| Product form and dimensions | Single-rolled plate or coil-derived product; thickness, width and length |
| Dimensional tolerances | Required thickness-tolerance class, flatness and edge condition |
| Delivery condition | Hot rolled, normalized rolled, normalized, or normalized and tempered, coordinated with the design code |
| Impact testing | Temperature, specimen requirements and any project-specific acceptance rules |
| Nondestructive examination | UT method, extent and acceptance grade |
| Special service requirements | HIC, through-thickness, drop-weight, elevated-temperature tensile or other agreed tests |
| Chemistry control | Any agreed carbon-equivalent, residual-element or tighter composition limit |
| Fabrication simulation | Required PWHT simulation or additional tests after simulated heat treatment |
| Certification | Quality certificate containing traceable heat, condition and test results |
The applicable pressure-vessel or boiler construction code should be identified separately; compliance with the plate material standard alone does not establish suitability for a particular vessel.
Edition history and substitution cautions
Q345R was retained when GB 713-2014 was reorganized into the GB/T 713 series, but the standard number and some technical details changed. Existing drawings and certificates referencing GB 713-2014 should not automatically be treated as certification to GB/T 713.2-2023. The predecessor 16MnR belongs to withdrawn earlier standards and should be resolved through an engineering review rather than simple renaming.
Appendix comparisons associate Q345R with grades such as ASME SA-516 Grade 70 and EN P355GH/P355NH, but these are approximate counterparts. Their chemistry, thickness ranges, delivery conditions, impact rules, testing frequency, certification and design-code status differ. Substitution requires a clause-by-clause comparison and approval under the governing construction code.
ASME SA/GB 713 appearing in earlier ASME BPVC editions was based on GB 713-2014 with ASME additions. It should not be assumed to be identical to the current GB/T 713.1/713.2 system without checking the specific ASME edition and project requirements.
Sources
- GB/T 713.2-2023 — Steel plate, sheet and strip for pressure equipments, Part 2State Administration for Market Regulation and Standardization Administration of China
- GB/T 713.1-2023 — General requirementsState Administration for Market Regulation and Standardization Administration of China
- GB/T 713.2-2023 English translation previewCode of China
- GB/T 150.2-2024 — Pressure vessels, Part 2: MaterialsState Administration for Market Regulation and Standardization Administration of China
- Heavy Plate Product ManualBeijing Shougang Co., Ltd.
- ASME BPVC Section II, Part A, 2023 — SA/GB 713ASME
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