SBHS500
High-yield-strength, weldable structural steel plate for bridges · JIS G 3140:2023 — Higher yield strength steel plates for bridges
SBHS500 is a Japanese 500 MPa minimum-yield bridge plate combining higher design strength with stringent toughness and weldability requirements. Its defining features are a thickness-independent minimum yield strength through 100 mm, 570–720 MPa tensile strength, transverse Charpy performance at −5 °C, and Pcm limited to 0.20%. It is normally produced by TMCP. SBHS500 is the non-weathering grade; SBHS500W is a separate weather-resistant designation.
- 6–100 mmApplicable plate thickness · The specified 500 MPa minimum yield strength applies throughout this range.
- 500 MPaMinimum yield strength · Yield point or 0.2% proof stress, as applicable.
- 570–720 MPaTensile strength · JIS G 3140 requirement for SBHS500.
- Average ≥100 J at −5 °CNotch toughness · Charpy V-notch specimens are transverse to the rolling direction; the standard impact requirement applies to plate over 12 mm thick.
- Pcm ≤0.20%Weld-cracking parameter · A principal distinction from conventional 570 MPa-class bridge steels and the basis for reduced-preheat fabrication practices.
- Non-weatheringCorrosion category · SBHS500 normally requires an appropriate corrosion-protection system. Specify SBHS500W when the weathering grade is required.
Overview
- Designation system
- JIS grade designation under JIS G 3140
- Product forms
- Hot-rolled steel plate, 6 mm to 100 mm thick
- Condition
- Thermomechanically controlled processed (TMCP), the normal delivery route, Quenched and tempered or another agreed heat-treated condition where permitted and identified by the applicable suffix
- Density
- 7850 kg/m³ (Nominal value conventionally used for structural-steel mass calculations; not a grade-specific requirement of JIS G 3140.)
What the designation defines
JIS G 3140 covers hot-rolled steel plates with high yield point or proof stress, principally for bridge construction, and with specifically enhanced weldability. In SBHS500, “500” denotes the specified minimum yield strength in N/mm². The designation controls plate chemistry, weld-cracking sensitivity, tensile properties, toughness, dimensions, inspection and marking; it does not by itself define a complete bridge design or fabrication specification.
SBHS500 must not be confused with SBHS500W. The suffix W identifies the weather-resistant version with additional alloy-composition requirements. The plain SBHS500 grade should be treated as conventional, non-weathering structural steel for corrosion-protection purposes.
Standard chemical and weldability controls
| Element | Requirement, mass % | Purpose or practical significance |
|---|---|---|
| C | ≤0.11 | Low carbon content supports weldability and heat-affected-zone toughness. |
| Si | ≤0.55 | Deoxidation and strength contribution; included in Pcm. |
| Mn | ≤2.00 | Principal strength and toughness alloying element; included in Pcm. |
| P | ≤0.020 | Restricted for cleanliness, toughness and fabrication performance. |
| S | ≤0.006 | Low sulfur supports toughness and through-thickness quality. |
| N | ≤0.006 | Restricted partly to control strain-ageing behavior after cold work. |
These are limiting requirements, not a target recipe. Producers may use Cu, Ni, Cr, Mo, Nb, V, B or other alloying and microalloying additions to obtain the required strength and toughness. The resulting heat must still satisfy the specified Pcm limit, and the elements entering the Pcm calculation are to be reported in the inspection documentation.
Mechanical properties and test conditions
| Property | Requirement | Applicability and test condition |
|---|---|---|
| Yield point or proof stress | ≥500 MPa | Plate thickness 6–100 mm; unlike many conventional structural grades, the minimum does not decrease at larger thickness. |
| Tensile strength | 570–720 MPa | Plate thickness 6–100 mm. |
| Charpy V-notch absorbed energy | Average of three specimens ≥100 J | Tested at −5 °C, transverse to the rolling direction; mandatory standard requirement for plate over 12 mm thick. |
| Elongation | Specimen- and thickness-dependent | Do not quote elongation without identifying the JIS tensile specimen and applicable thickness range. |
| Plate thickness | JIS tensile specimen | Minimum elongation |
|---|---|---|
| 6–16 mm | No. 5 | 19% |
| >16 mm | No. 5 | 26% |
| >20 mm | No. 4 | 20% |
Elongation percentages from different specimen geometries are not directly interchangeable. The applicable specimen arrangement should be confirmed against the ordered edition of JIS G 3140.
The transverse Charpy orientation is important in bridge fabrication because it provides toughness qualification across the rolling direction and gives greater freedom in plate nesting. The 100 J requirement is an average group value, not necessarily the acceptance threshold for every individual specimen; group evaluation and retesting are governed by the referenced JIS general delivery rules.
Production route and metallurgical character
SBHS500 is normally produced by thermomechanical controlled processing. Controlled rolling and accelerated cooling refine the microstructure and obtain high yield strength and toughness without relying on the heavier alloy content that would normally impair weldability. No heat-treatment suffix is added for the normal TMCP condition. Where JIS G 3140 permits quenched-and-tempered production by agreement, the grade marking includes Q; other agreed heat-treatment routes require appropriate identification.
The strength and toughness are process-dependent. Uncontrolled hot forming, flame straightening, stress relief or other thermal cycles can alter a TMCP plate's microstructure and properties. Heating limits and corrective procedures should come from the project fabrication specification, steel producer and qualified procedure—not from the grade designation alone.
Welding and fabrication implications
The Pcm ceiling of 0.20% is one of SBHS500's most practically valuable requirements. Japanese bridge guidance commonly permits welding without preheat for SBHS500 under the stated combinations of plate thickness, consumable, ambient conditions and welding procedure. This does not mean that preheat can be omitted unconditionally. Hydrogen level, restraint, joint thickness, heat input, interpass temperature, ambient temperature and moisture exposure remain relevant, and the approved welding procedure governs the work.
| Characteristic | Industry bridge-fabrication guidance | Qualification point |
|---|---|---|
| Joint tensile strength | ≥570 MPa | The fracture position need not be prescribed in the cited SBHS guidance. |
| Weld-metal Charpy energy | Average ≥47 J at −5 °C | This is a weld-joint performance target, not the base-plate requirement of ≥100 J. |
| Consumables | 570 MPa-class low-hydrogen welding consumables appropriate to the process | Consumable classification, diffusible hydrogen, position, heat input and shielding must match the qualified procedure. |
These joint values come from SBHS fabrication guidance and are not additional chemical or mechanical requirements imposed on the plate by JIS G 3140.
Cold bending requires attention because plastic strain can reduce toughness through strain ageing. JIS G 3140 includes an optional supplementary impact-quality scheme for SBHS500 plates intended for cold bending at inside radii of at least 7t or 5t, with symbols identifying the radius class and bend direction. This supplementary quality must be agreed and ordered; ordinary SBHS500 marking does not establish compliance with it.
Engineering use and limitations
SBHS500 can reduce plate thickness or member weight where resistance is governed by yielding or gross-section strength. The benefit is not proportional in every bridge component. Fatigue resistance is primarily controlled by welded-detail category and stress range, while buckling, deflection, vibration, minimum-thickness rules, corrosion allowance and connection geometry may prevent full use of the higher yield strength.
Its principal technical advantage over conventional 570 MPa tensile-class bridge plate is the combination of a 500 MPa minimum yield strength at all specified thicknesses, high transverse toughness and tightly controlled weldability. It should nevertheless be introduced through the applicable bridge design standard. JIS G 3140 establishes material conformity; it does not establish permissible stresses, fatigue categories, fracture-control temperatures, welding acceptance criteria or execution rules for a particular project.
Ordering, certification and substitution
| Item | What should be stated or checked |
|---|---|
| Standard and grade | JIS G 3140:2023, SBHS500; do not omit the edition where contractually important. |
| Dimensions | Thickness, width, length, edge condition and the applicable JIS G 3193 tolerances. |
| Delivery condition | Normal TMCP condition or an expressly agreed alternative heat-treatment condition with correct marking. |
| Toughness | Standard −5 °C requirement, or a lower agreed test temperature where required by the project. |
| Cold-bending quality | Specify the JIS G 3140 supplementary impact-quality symbol when the plate will undergo qualifying 7t or 5t cold bending. |
| Additional testing | Ultrasonic examination, through-thickness properties, tighter flatness, special surface quality or project-specific testing must be separately specified. |
| Inspection document | Require a certificate identifying the heat, actual chemistry, Pcm, mechanical results, dimensions and delivery condition. |
| Corrosion requirement | Use SBHS500 for protected construction; separately assess and specify SBHS500W if weathering performance is intended. |
A plate marketed as “500 MPa bridge steel” or “570 MPa-class high-strength steel” is not automatically SBHS500. Substitution requires comparison of the governing product specification, thickness range, yield and tensile limits, transverse impact test, Pcm, chemistry, delivery condition, dimensional tolerances, inspection documentation and approval under the project design and fabrication rules.
Sources
- JIS G 3140:2023 — Higher yield strength steel plates for bridges, official previewJapanese Standards Association
- SBHS — Steels for Bridge High Performance StructuresThe Japan Iron and Steel Federation
- SBHS — High-performance Steel for Bridges Originated in JapanThe Japan Iron and Steel Federation
- JIS G 3140:2011 — Higher yield strength steel plates for bridgesKikakurui
- Common Specifications for Civil Engineering Construction, factory fabrication and welding provisionsMinistry of Land, Infrastructure, Transport and Tourism, Japan
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