Steel A588 · grade
Steel A588-GrB
Properties of the GrB condition, compared with the other A588 tempers.
Default mill chemistry for plate and shapes; best balance of weldability and weathering index.
What is A588-GrB?
A588-GrB is A588 in the GrB grade — default mill chemistry for plate and shapes; best balance of weldability and weathering index. A588-GrB has a yield strength of 390 MPa (56.6 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 64% of steel grades. Elongation at break is 23% and the elastic modulus is 200 GPa (29 Msi). A588-GrB has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,430°C (2,606 °F). HR is the default condition FabDigit quotes; GrB is available on request or by drawing note.
Advantages
- Good corrosion resistance — 28/100, better than 93% of steel grades
- Readily welded — 76/100, better than 77% of steel grades
Limitations
- Hard to polish — 45/100, worse than 84% of steel grades
A588-GrB properties
Typical room-temperature values for A588-GrB — 32 properties are specific to this condition; the rest are grade-level values shared by every A588 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
A588-GrB has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,430°C (2,606 °F).
Mechanical16
A588-GrB has a yield strength of 390 MPa (56.6 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 64% of steel grades. Elongation at break is 23% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
A588-GrB is rated for continuous service to 400°C (752 °F). It conducts heat at 47 W/m·K (27.2 BTU/hr·ft·°F), better than 75% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
A588-GrB conducts electricity at 8.6 % IACS, better than 66% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (28/100), better than 93% of steel grades.
Sustainability4
Producing a kilogram of A588-GrB takes about 26 MJ of energy and emits 2 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 35%.
Manufacturability7
A588-GrB's machinability is fair (53/100, better than 53% of steel grades); weldability very good (76/100); formability good (60/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other A588 tempers and conditions
A588 is also supplied in 9 other conditions. The full side-by-side table is on the A588 overview.
- HRDefaultStandard stocked condition for structural plate, beams and bar; bare-exposure weathering use.380 MPa yield · 155 HB
- GrBDefault mill chemistry for plate and shapes; best balance of weldability and weathering index.390 MPa yield · 160 HB
- CRThin gauge sheet for cladding/panels where tight thickness tolerance and a smoother start surface are wanted.380 MPa yield · 160 HB
- GrAUse where the classic higher-silicon weathering chemistry is specified; mechanicals identical to Grade B.380 MPa yield · 155 HB
- GrKLower-carbon option for improved weld and bend behaviour at equal 345 MPa yield.375 MPa yield · 150 HB
Working with A588-GrB
Is A588 easy to machine?
Machines like a 345 MPa-class HSLA steel — roughly 55–60 % of AISI 1212; carbide tooling, moderate speeds, slightly gummy chips from the Cu addition.
Can A588 be welded?
Prequalified in AWS D1.1; use weathering-matched consumables (E80xx-W, ER80S-G, or three-pass rule with mild-steel filler) so the weld patinates with the base metal, and preheat thick sections per CE.
Can A588 be formed, bent or molded?
Cold bends and press-brake work readily at generous radii (≈2–3 t for plate); hot forming is fine but avoid slow cooling that coarsens grain, and re-normalize thick sections if toughness is critical.
What surface finishes work on A588?
Grit-blast to bare metal and leave exposed to develop the patina (allow drainage, avoid crevices and rust run-off onto adjacent surfaces); alternatively paint, metallize or hot-dip galvanize — anodizing is not applicable.
A588 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| CGrade B; Grade A 0.19 max, Grade K 0.17 max | ≤ 0.2 | 0.15 |
| MnGrade B | 0.75 – 1.35 | 1.05 |
| SiGrade A 0.30–0.65 | 0.15 – 0.5 | 0.3 |
| P | ≤ 0.04 | 0.02 |
| S0.030 max typical mill practice | ≤ 0.05 | 0.01 |
| Cr | 0.4 – 0.7 | 0.55 |
| Cukey weathering element | 0.2 – 0.4 | 0.3 |
| Ni | ≤ 0.5 | 0.25 |
| V | 0.01 – 0.1 | 0.05 |
| Fe | balance | — |
A588-GrB — frequently asked
What is A588-GrB used for?
A588-GrB is typically used for weathering steel bridge girders, architectural facade and cladding panels, outdoor sculptures and monuments, shipping container structures, retaining walls and sound barriers and sign structures and light poles. In short: rust-resistant weathering steel.
What is the yield strength of A588-GrB?
A588-GrB has a typical yield strength of 390 MPa (56.6 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 64% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is A588-GrB easy to machine?
Reasonably — machinability is rated fair (53/100, better than 53% of steel grades). Machines like a 345 MPa-class HSLA steel — roughly 55–60 % of AISI 1212; carbide tooling, moderate speeds, slightly gummy chips from the Cu addition.
Can A588-GrB be welded?
Yes — weldability is rated very good (76/100). Prequalified in AWS D1.1; use weathering-matched consumables (E80xx-W, ER80S-G, or three-pass rule with mild-steel filler) so the weld patinates with the base metal, and preheat thick sections per CE.
What surface finishes work on A588-GrB?
Grit-blast to bare metal and leave exposed to develop the patina (allow drainage, avoid crevices and rust run-off onto adjacent surfaces); alternatively paint, metallize or hot-dip galvanize — anodizing is not applicable.
Can A588-GrB be formed, bent or molded?
Cold bends and press-brake work readily at generous radii (≈2–3 t for plate); hot forming is fine but avoid slow cooling that coarsens grain, and re-normalize thick sections if toughness is critical.
What is the maximum service temperature of A588-GrB?
A588-GrB is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A588-HR and A588-N?
HR is the default condition — standard stocked condition for structural plate, beams and bar; bare-exposure weathering use. N: specified for thick plate or fracture-critical/low-temperature service needing guaranteed CVN energy. Yield strength is 380 MPa in HR versus 390 MPa in N.
Can FabDigit make parts in A588-GrB?
Yes — A588-GrB is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A588/A588M — High-Strength Low-Alloy Structural Steel with Atmospheric Corrosion Resistance — ASTM International (2019)
- ASTM A606/A606M — Steel Sheet and Strip, Hot-Rolled and Cold-Rolled, with Improved Atmospheric Corrosion Resistance (Type 4) — ASTM International (2018)
- ASTM G101 — Estimating the Atmospheric Corrosion Resistance of Low-Alloy Steels — ASTM International (2020)
- GB/T 4171 — (Q355NH / Q235NH) — SAC / (2008)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.13C — Corrosion: Environments and Industries — ASM International (2006)
- COR-TEN A / COR-TEN B weathering steel data sheet — SSAB / ArcelorMittal (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.