🏗️ Q620qD/E/F Structural Steel for Bridge
Grades Q620q D / E / F · Thermomechanical rolling (TMCP) / Quenched and Tempered | Steel plate ≤150mm / Steel strip ≤25.4mm
This document specifies the designation method, ordering content, manufacturing process, technical requirements, test methods, inspection rules, packaging, marking and quality certificate of structural steel for bridge. This document applies to single-rolled steel plates for bridge of thickness not greater than 150 mm, hot-rolled steel strips and cut-to-length plates (hereinafter referred to as "steel plates and strips") of thickness not greater than 25.4 mm.
| No. | Standard No. | Title |
|---|---|---|
| 1 | GB/T 222 | Permissible tolerance of chemical composition for steel |
| 2 | GB/T 223 (all parts) | Methods for chemical analysis of iron and steel |
| 3 | GB/T 228.1 | Tensile testing – Part 1: Method of test at room temperature |
| 4 | GB/T 229 | Charpy pendulum impact test method |
| 5 | GB/T 232 | Bend test method for metallic materials |
| 6 | GB/T 247 | General rules of packaging, marking and quality certificate |
| 7 | GB/T 709 | Dimensions, shape, weight and tolerances for hot-rolled plates |
| 8 | GB/T 2970 | Ultrasonic testing method for thick steel plates |
| 9 | GB/T 2975 | Location and preparation of samples for mechanical testing |
| 10 | GB/T 4336 | Determination of multi-element content – Spark discharge atomic emission |
| 11 | GB/T 5313 | Steel plates with through-thickness characteristics |
| 12 | GB/T 8170 | Rounding rules for numerical values |
| 13 | GB/T 17505 | General technical delivery requirements for steel |
| 14 | GB/T 20066 | Sampling and preparation of samples for chemical composition |
| 15 | GB/T 20123 | Determination of total carbon and sulfur |
| 16 | GB/T 20124 | Determination of nitrogen |
| 17 | GB/T 20125 | Determination of multi-element content – ICP-AES |
3.1 Normalizing
Heat treatment process in which steel is heated to a suitable temperature above the transformation point and then cooled in air to below a transformation point.
3.2 Thermomechanical rolling (TMCP)
Rolling process in which the final deformation of steel is carried out within a certain temperature range, so as to ensure that the steel obtains properties that cannot be achieved by heat treatment alone. Note: also known as TMCP.
3.3 Quenched and tempered
Heat treatment method in which steel is quenched and then tempered at a high temperature.
3.4 Atmospheric corrosion resisting steel
Steel to which a certain amount of alloying elements (Cr, Ni, Cu, Mo, etc.) are added to form a dense rust layer on the metal matrix surface to improve atmospheric corrosion resistance, designated NH.
The designation consists of: "Q" (yield strength), the specified minimum yield strength value, "q" (bridge), and quality grade symbol.
Example: Q620qD. When through-thickness properties are required, add Z25/Z35, e.g., Q620qDZ35.
Orders shall include: a) document number; b) product name; c) designation; d) dimensions; e) shape/accuracy; f) weight; g) delivery condition; h) special requirements.
6.1 Steelmaking process Steel shall be made by converter or electric arc furnace and treated by secondary refining including vacuum degassing.
6.2 Delivery condition Steel shall be delivered in thermomechanical rolling (TMCP), TMCP + tempering or quenched + tempered condition.
Table 1 — P, S, B, H requirements for each quality grade
| Quality grade | P (max %) | S (max %) | B (max %) | H (max %) |
|---|---|---|---|---|
| C | 0.030 | 0.025 | 0.0005 | 0.0002 |
| D | 0.025 | 0.015 | ||
| E | 0.020 | 0.010 | ||
| F | 0.015 | 0.006 |
a) When through-thickness properties are required, sulfur content shall comply with GB/T 5313.
b) Residual elements B and H may be omitted if guaranteed by the supplier.
c) For quenched and tempered steel, B content is not restricted, and shall be analyzed and reported in the quality certificate.
d) For thermomechanical rolled steel with C ≤0.10%, B content shall not exceed 0.0014%.
e) For atmospheric corrosion resisting steel with C ≤0.06%, B content shall not exceed 0.0014%.
Table 3 — Chemical composition of thermomechanical rolled steel (TMCP) – Q620q
| Grade | C | Si | Mn | Nb | V | Ti | Als | Cr | Ni | Cu | Mo | N |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Q620qD/E/F | ≤0.11 | ≤0.50 | 0.80~1.70 | 0.005~0.090 | 0.010~0.080 | 0.006~0.030 | 0.010~0.045 | ≤1.0 | ≤1.20 | ≤0.55 | ≤0.60 | ≤0.008 |
a) Al, Nb, V, Ti may be added alone or in combination; when combined, Nb+V+Ti ≤0.22%.
b) When total aluminum (Alt) is used, Alt shall be 0.015%~0.050%.
c) By agreement, maximum Mn may be increased to 2.00%.
Table 4 — Chemical composition of quenched and tempered steel (QT) – Q620q
| Grade | C | Si | Mn | Nb | V | Ti | Als | Cr | Ni | Cu | Mo | N |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Q620qD/E/F | ≤0.14 | ≤0.55 | 0.80~1.70 | 0.005~0.090 | 0.010~0.080 | 0.006~0.030 | 0.010~0.045 | 0.40~0.80 | 0.25~1.00 | 0.15~0.55 | 0.20~0.50 | ≤0.008 |
a) Al, Nb, V, Ti may be added alone or in combination; when combined, Nb+V+Ti ≤0.22%.
b) When total aluminum (Alt) is used, Alt shall be 0.015%~0.050%.
7.1.2.1 Carbon equivalent (CEV) for normalized steel, Q&T steel and TMCP steel with carbon >0.12%
7.1.2.2 Crack susceptibility index (Pcm) for atmospheric corrosion resisting steel and TMCP steel with carbon ≤0.12%
| Category | Grade | ≤50mm | >50~100mm | >100~130mm | >130~150mm |
|---|---|---|---|---|---|
| TMCP | Q620q | ≤0.24 | ≤0.25 | ≤0.25 | — |
7.1.3 Permissible tolerances for finished chemical composition shall comply with GB/T 222.
7.2.1 Mechanical properties shall comply with Table 9 and Table 10.
Table 9 — Tensile properties
| Grade | Quality | Lower yield strength ReL (MPa) | Tensile strength Rm (MPa) | A% ≥ | |||||
|---|---|---|---|---|---|---|---|---|---|
| ≤50 | >50~100 | >100~130 | >130~150 | ≤100 | >100~130 | >130~150 | |||
| Q620q | D | 620 | 580 | — | — | 720 | — | — | 15 |
| E | |||||||||
| F | |||||||||
a) When yield point is not obvious, Rp0.2 may be used.
b) Tensile test specimens taken transversely.
c) For plate thickness >40mm, round tensile specimens shall be used. When thickness >25mm and ≤40mm and testing capacity is insufficient, round tensile specimens may also be used.
Table 10 — Impact properties (Charpy V-notch)
| Grade | Quality | Test temp (°C) | Absorbed energy KV₂ (J) | ||
|---|---|---|---|---|---|
| ≤12mm | >12~100mm | >100~150mm | |||
| Q620q | D | -20 | 80 | 120 | 一 |
| E | -40 | ||||
| F | -60 | by agreement | 69 | ||
a) Impact test specimens taken longitudinally.
7.2.2 Impact absorbed energy is calculated as the arithmetic mean of a set of three specimens; one single value may be below the specified value but not less than 70% of the specified value.
7.2.3 For thickness <12mm, subsize impact specimens are permitted: for 8mm< thickness <12mm, 7.5×10×55mm specimen, result ≥75% of Table 10 value; for 6mm~8mm, 5×10×55mm specimen, result ≥50% of Table 10 value; no impact test for thickness <6mm.
7.2.4 If impact test results do not conform, three additional specimens from the same batch shall be tested. The arithmetic mean of the six specimens shall not be less than the specified value; two specimens may be below the specified value, but only one specimen may be below 70% of the specified value.
7.2.5 When through-thickness properties are required, reduction of area shall comply with GB/T 5313.
| Nominal thickness ≤16mm | >16mm | Bend result |
|---|---|---|
| D=2a | D=3a | No visible cracks on outer surface |
7.4.1 No blisters, scabs, cracks, folds, inclusions or rolled-in scale. No visible delamination.
7.4.2 Thin scale, rust, slight roughness, scratches are permitted provided depth ≤ half thickness tolerance and minimum thickness is maintained.
7.4.3 Defects may be removed by grinding; ground area shall be smooth, depth not greater than minus tolerance and minimum thickness shall be maintained.
7.4.4 For steel strip, defective portion shall not exceed 6% of total strip length.
7.4.5 By agreement, surface quality may also comply with GB/T 14977.
For single-rolled plates with thickness >20mm, ultrasonic testing shall be carried out according to GB/T 2970, acceptance level not lower than Class II. For other thicknesses, NDT may be performed by agreement.
7.6.1 Dimensions, shape, weight and tolerances shall comply with GB/T 709.
7.6.2 Other dimensions, shape and tolerances may be supplied by agreement.
Yield ratio may be specified by agreement; recommended values see Annex C.
8.1 Chemical composition analysis shall be carried out according to GB/T 223 (all parts), GB/T 4336, GB/T 20123, GB/T 20124, GB/T 20125 or general methods; arbitration method shall be agreed upon.
8.2 Steel plates and strips inspection items, sample quantity, sampling method and test method shall comply with Table 12.
Table 12 — Inspection items, sample quantity, sampling method and test method
| No. | Inspection item | Sample quantity | Sampling method | Test method |
|---|---|---|---|---|
| 1 | Chemical composition (ladle analysis) | 1 per heat | GB/T 20066 | see 8.1 |
| 2 | Tensile test | 1 per batch | GB/T 2975 | GB/T 228.1 |
| 3 | Bend test | 1 per batch | GB/T 2975 | GB/T 232 |
| 4 | Impact test | 3 per batch | GB/T 2975 | GB/T 229 |
| 5 | Through-thickness property | 3 per batch | GB/T 5313 | GB/T 5313 |
| 6 | Non-destructive testing | each plate | — | GB/T 2970 |
| 7 | Surface quality | each plate/coil | — | visual inspection |
| 8 | Dimensions & shape | each plate/coil | — | measuring tools |
9.1 Inspection and acceptance by supplier's quality inspection department.
9.2.1 Steel plates and strips shall be accepted in batches. Each batch shall consist of the same designation, heat, dimensions, rolling system and heat treatment system. Batch weight ≤60t. For coils >30t, two coils may form one batch.
9.2.2 For through-thickness properties, batch size shall comply with GB/T 5313.
9.3 Sample quantity and sampling method according to Table 12.
9.4.1 Re-inspection and judgment for tensile, impact and bend tests shall comply with GB/T 17505.
9.4.2 Re-inspection and judgment for through-thickness reduction of area shall comply with GB/T 5313.
9.5 Numerical rounding using comparison method according to GB/T 8170.
Shall comply with GB/T 247.
Reference T/CISA 073 and T/CISA 217.
A.1 Rural/urban: Cl⁻ deposition ≤3 mg/(m²·d); SO₂ ≤24 mg/(m²·d); wet time ≤5256h/year.
A.2 Coastal: may be used coating-free if corrosive factors meet A.1.
| This document | ASTM A709-21 | EN 10025-3:2019 | EN 10025-4:2019 | EN 10025-6:2019 |
|---|---|---|---|---|
| Q620q | — | — | — | S620Q,S620QL,S620QL1 |
| Grade | Yield ratio (thickness ≤12mm) | Yield ratio (thickness >12mm) |
|---|---|---|
| Q620q, Q620qNH | 0.88 | 0.86 |
T/CISA 073 (Marine atmospheric corrosion resisting steel plate for bridge) and T/CISA 217 (Hot-rolled longitudinal variable thickness steel plate for bridge).
[1] GB/T 14977 Hot-rolled steel plate surface quality general requirements
[2] T/CISA 073 Bridge steel plate with marine atmospheric corrosion resistance
[3] T/CISA 217 Hot-rolled longitudinal variable thickness steel plate for bridge
[4] ASTM A709-21 Standard specification for structural steel for bridges
[5] EN 10025-3:2019 Hot rolled products of structural steels – Part 3
[6] EN 10025-4:2019 Hot rolled products of structural steels – Part 4
[7] EN 10025-6:2019 Hot rolled products of structural steels – Part 6