Steel SM490B
Grade
JIS SM490
SM490B = charpy ≥27 J at 0 °C
Standard choice for bridges and outdoor frames with moderate notch-toughness demand.
Values for the SM490B condition
Other SM490 tempers and conditions
SM490 is listed in 8 conditions; see the grade overview at SM490.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
No specified Charpy requirement | Lowest-cost sub-grade for ordinary indoor or ambient-temperature welded structures. | 360 | 530 | 22 | 158 HB | 8.6 % IACS |
HRDefault Hot rolled | Default stock condition for structural plate, strip and sections; use for welded frames, bridges and machine bases. | 365 | 530 | 23 | 160 HB | 8.6 % IACS |
SM490BThis page Charpy ≥27 J at 0 °C | Standard choice for bridges and outdoor frames with moderate notch-toughness demand. | 365 | 530 | 23 | 160 HB | 8.6 % IACS |
Normalized | Pick for thick plate or low-temperature/high-toughness duty where uniform fine grain and reliable Charpy values are required. | 370 | 540 | 25 | 155 HB | 8.6 % IACS |
Charpy ≥47 J at 0 °C, lower carbon | Use for thick, highly restrained or fatigue-loaded welded joints demanding high toughness. | 370 | 535 | 24 | 162 HB | 8.6 % IACS |
Higher yield class (≥365 MPa), no Charpy requirement | Pick when design is yield-governed and weight saving matters, in non-critical toughness service. | 400 | 540 | 20 | 170 HB | 8.5 % IACS |
Higher yield class (≥365 MPa) with Charpy ≥27 J at 0 °C | High-yield sub-grade with guaranteed toughness for bridge girders and heavy welded sections. | 405 | 545 | 21 | 172 HB | 8.5 % IACS |
Cold rolled | Choose when tight thickness tolerance, clean surface and higher yield are wanted; ductility and bend radius suffer. | 480 | 600 | 14 | 185 HB | 8.6 % IACS |
What is SM490B?
SM490B is SM490 in the SM490B grade — standard choice for bridges and outdoor frames with moderate notch-toughness demand. SM490B has a yield strength of 365 MPa (52.9 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 71% of steel grades. Elongation at break is 23% and the elastic modulus is 206 GPa (29.9 Msi). SM490B has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). HR is the default condition FabDigit quotes; SM490B is available on request or by drawing note.
Advantages
- Readily welded — 86/100, better than 85% of steel grades
- Tough — resists crack growth — 120 MPa·√m (109.2 ksi·√in), better than 81% of steel grades
- Conducts heat well — 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades
Limitations
- Hard to polish — 45/100, worse than 84% of steel grades
SM490B properties
Typical room-temperature values for SM490B; 23 are specific to this condition. Other listed values are SM490 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SM490B has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
SM490B has a yield strength of 365 MPa (52.9 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 71% of steel grades. Elongation at break is 23% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
SM490B is rated for continuous service to 350°C (662 °F). It conducts heat at 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
SM490B conducts electricity at 8.6 % IACS, better than 66% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of SM490B takes about 25 MJ of energy and emits 2.1 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
SM490B's machinability is good (55/100, better than 62% of steel grades); weldability excellent (86/100); formability good (60/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SM490B
Is SM490 easy to machine?
Machines like ordinary C-Mn structural steel (~55–60 % of 1212); use coated carbide, moderate speeds and generous coolant, expect gummy chips and mill-scale abrasion on the first pass.
Can SM490 be welded?
Designed for welding — SMAW/GMAW/SAW with E70xx-class consumables; preheat 50–150 °C for thick or restrained joints and keep hydrogen low to avoid HAZ cracking.
Can SM490 be formed, bent or molded?
Good hot forming and press braking; keep cold bend radius ≥2t (≥3t for thick plate) and bend transverse to the rolling direction.
What surface finishes work on SM490?
Blast off mill scale then zinc-rich primer, paint or hot-dip galvanize; not anodizable and bare surfaces rust quickly outdoors.
SM490 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 |
|---|---|---|
| C≤0.20 for t≤50 mm, ≤0.22 for t>50 mm (SM490A/YA/YB); ≤0.18 for SM490C | ≤ 0.2 | 0.16 |
| Si | ≤ 0.55 | 0.3 |
| MnSM490C: 1.60 max, deoxidized/killed practice | ≤ 1.6 | 1.3 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.04 | 0.01 |
| Febalance, plus residual Cu/Ni/Cr and micro-alloy additions at mill option | balance | — |
SM490B — frequently asked
What is SM490B used for?
SM490B is typically used for welded bridge girders, industrial building frames, crane and gantry structures, pressure-bearing structural frames, heavy machine bases and weldments and galvanized structural sections. In short: japanese structural plate.
What is the yield strength of SM490B?
SM490B has a typical yield strength of 365 MPa (52.9 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 71% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is SM490B easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like ordinary C-Mn structural steel (~55–60 % of 1212); use coated carbide, moderate speeds and generous coolant, expect gummy chips and mill-scale abrasion on the first pass.
Can SM490B be welded?
Yes — weldability is rated excellent (86/100). Designed for welding — SMAW/GMAW/SAW with E70xx-class consumables; preheat 50–150 °C for thick or restrained joints and keep hydrogen low to avoid HAZ cracking.
What surface finishes work on SM490B?
Blast off mill scale then zinc-rich primer, paint or hot-dip galvanize; not anodizable and bare surfaces rust quickly outdoors.
Can SM490B be formed, bent or molded?
Good hot forming and press braking; keep cold bend radius ≥2t (≥3t for thick plate) and bend transverse to the rolling direction.
What is the maximum service temperature of SM490B?
SM490B is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SM490-HR and SM490-CR?
HR is the default condition — default stock condition for structural plate, strip and sections; use for welded frames, bridges and machine bases. CR: choose when tight thickness tolerance, clean surface and higher yield are wanted; ductility and bend radius suffer. Yield strength is 365 MPa in HR versus 480 MPa in CR.
Can FabDigit make parts in SM490B?
Yes — SM490B is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- JIS G 3106 Rolled steels for welded structure — JISC (2020)
- GB/T 1591 Q345B (equivalent low-alloy structural steel) — SAC (2018)
- ASM Handbook Vol.1 — Properties of Carbon and Low-Alloy Steels — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- Structural plate product guide (SM490A/B/C) — Nippon Steel / JFE Steel (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.