Steel SM490A
JIS SM490A · ASTM A572 Gr 50
SM490A is the higher-strength weldable grade of the JIS SM structural series, a C-Mn steel comparable to ASTM A572 Grade 50.
Reference datasheet — SM490A is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the AR condition
SM490A tempers and conditions
SM490A is supplied in 4 conditions, soft to hard. AR is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Stress relieved | Use for heavy welded fabrications needing dimensional stability and reduced residual stress before machining. | 350 | 520 | 25 | 148 HB | 10 % IACS |
Normalized | Pick for thick plate or after hot forming when uniform fine grain and better notch toughness are required. | 360 | 530 | 25 | 150 HB | 10 % IACS |
ARDefault As hot rolled | Standard stocked plate/section condition for general welded structures at ambient service temperature. | 365 | 540 | 22 | 155 HB | 10 % IACS |
Thermomechanically controlled processed | Choose for thick bridge/offshore plate where low carbon equivalent, better weldability and higher toughness are needed at the same strength. | 385 | 545 | 24 | 160 HB | 10 % IACS |
What is SM490A?
SM490A is the higher-strength weldable grade of the JIS SM structural series, a C-Mn steel comparable to ASTM A572 Grade 50. It gives 365 MPa yield, 540 MPa tensile, 22 % elongation and about 155 HB, supplied as-rolled, normalized, TMCP or stress-relieved plate and sections for heavy welded structures. Weldability remains good but thick or highly restrained joints need preheat, and cold-bend radii are larger than for SM400A. No corrosion resistance without coating; drop to SM400A for maximum formability or move to SM520 for more strength. SM490A 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). SM490A has a yield strength of 365 MPa (52.9 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 71% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
What is SM490A used for?
- bridges
- heavy structures
- cranes
- shipbuilding
Advantages
- Readily welded — 88/100, better than 87% of steel grades
- Conducts heat well — 49 W/m·K (28.3 BTU/hr·ft·°F), better than 83% of steel grades
- High electrical conductivity — 10 % IACS, better than 83% of steel grades
- Forms and bends easily — 65/100, better than 81% of steel grades
Limitations
- Hard to polish — 40/100, worse than 96% of steel grades
SM490A properties
Typical room-temperature values for SM490A-AR; bars are the position among steel grades.
Physical3
SM490A 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
SM490A has a yield strength of 365 MPa (52.9 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 71% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SM490A is rated for continuous service to 350°C (662 °F). It conducts heat at 49 W/m·K (28.3 BTU/hr·ft·°F), better than 83% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
SM490A conducts electricity at 10 % IACS, better than 83% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SM490A takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability6
SM490A's machinability is good (58/100, better than 75% of steel grades); weldability excellent (88/100); formability good (65/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. SM490A is highlighted; hover a dot for its name, or open the interactive family chart.
Working with SM490A
Is SM490A easy to machine?
Machines like ordinary C-Mn structural steel at ~60 % of AISI 1212; use rigid setups and coolant, expect stringy chips in as-rolled plate.
Can SM490A be welded?
Excellent weldability by SMAW/GMAW/SAW with ~E49xx / ER70S-class consumables; preheat 50–100 °C for thick sections or high restraint.
Can SM490A be formed, bent or molded?
Cold bend at r ≥ 2t (≥3t across the rolling direction for thick plate); hot forming 900–1050 °C followed by normalizing is preferred for tight radii.
SM490A 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 (JIS G3106) | ≤ 0.2 | 0.16 |
| Si | ≤ 0.55 | 0.3 |
| Mn≤1.65 (older editions 1.60); ≥0.60 for shapes | ≤ 1.65 | 1.35 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.04 | 0.02 |
| Fe | balance |
What surface finishes work on SM490A?
Must be protected — blast to Sa 2½ then epoxy/zinc-rich primer, hot-dip galvanize, or metallize; no anodizing, polishing is only for cosmetic ground plate.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel SM490A in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- A572 Gr 50
How much does SM490A cost?
SM490A is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
SM490A — frequently asked
What is SM490A used for?
SM490A is typically used for bridges, heavy structures, cranes and shipbuilding. In short: A572 Gr 50 equivalent; weldable at 365 MPa yield; needs preheat when thick.
What is the yield strength of SM490A?
SM490A has a typical yield strength of 365 MPa (52.9 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 71% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is SM490A easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machines like ordinary C-Mn structural steel at ~60 % of AISI 1212; use rigid setups and coolant, expect stringy chips in as-rolled plate.
Can SM490A be welded?
Yes — weldability is rated excellent (88/100). Excellent weldability by SMAW/GMAW/SAW with ~E49xx / ER70S-class consumables; preheat 50–100 °C for thick sections or high restraint.
What surface finishes work on SM490A?
Must be protected — blast to Sa 2½ then epoxy/zinc-rich primer, hot-dip galvanize, or metallize; no anodizing, polishing is only for cosmetic ground plate.
Can SM490A be formed, bent or molded?
Cold bend at r ≥ 2t (≥3t across the rolling direction for thick plate); hot forming 900–1050 °C followed by normalizing is preferred for tight radii.
What is the maximum service temperature of SM490A?
SM490A 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 SM490A-AR and SM490A TMCP?
AR is the default condition — standard stocked plate/section condition for general welded structures at ambient service temperature. TMCP: choose for thick bridge/offshore plate where low carbon equivalent, better weldability and higher toughness are needed at the same strength. Yield strength is 365 MPa in AR versus 385 MPa in TMCP.
How much does SM490A cost?
SM490A is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- JIS G3106 Rolled steels for welded structure — JSA (2020)
- ASTM A572/A572M Grade 50 — ASTM (2021)
- GB/T 1591 Q345B / Q355B — SAC (2018)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- Heavy plate for welded structures (SM490 series) — Nippon Steel / JFE Steel (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.