Steel SM400A-N (Normalized)
Heat-treated state
JIS SM400A · ASTM A36
Choose for thick plate or when uniform fine-grain structure and better notch toughness / dimensional stability after cutting are needed.
Values for the N condition
Other SM400A tempers and conditions
SM400A is listed in 5 conditions; see the grade overview at SM400A.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Stress relieved | Post-weld or post-machining stress relief (550–650 °C) for dimensionally critical or heavily welded weldments. | 260 | 425 | 30 | 115 HB | 11 % IACS |
HRDefault Hot rolled | Standard mill supply condition for plate, sections and flats — pick for general welded structures, buildings and bridge secondary members. | 275 | 440 | 26 | 125 HB | — |
NThis page Normalized | Choose for thick plate or when uniform fine-grain structure and better notch toughness / dimensional stability after cutting are needed. | 285 | 445 | 29 | 125 HB | 10.8 % IACS |
Cold rolled | Mill-controlled finishing temperature for finer grain without a separate heat treatment — used for medium-thickness bridge and ship plate. | 295 | 450 | 28 | 130 HB | 10.8 % IACS |
Thermomechanically controlled processed | Pick for heavy plate where low carbon equivalent (easier field welding, less preheat) plus good toughness is required. | 305 | 460 | 28 | 135 HB | 10.8 % IACS |
What is SM400A-N?
SM400A-N is SM400A heat treated to N — choose for thick plate or when uniform fine-grain structure and better notch toughness / dimensional stability after cutting are needed. SM400A-N has a yield strength of 285 MPa (41.3 ksi) and a tensile strength of 445 MPa (64.5 ksi) — weaker than 89% of steel grades. Elongation at break is 29% and the elastic modulus is 205 GPa (29.7 Msi). SM400A-N 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; N is available on request or by drawing note.
Advantages
- Readily welded — 95/100, better than 97% of steel grades
- Easy to machine — 66/100, better than 95% of steel grades
- High electrical conductivity — 10.8 % IACS, better than 94% of steel grades
- Forms and bends easily — 84/100, better than 94% of steel grades
- Conducts heat well — 51 W/m·K (29.5 BTU/hr·ft·°F), better than 92% of steel grades
Limitations
- Low strength — 285 MPa (41.3 ksi), worse than 89% of steel grades
- Hard to polish — 45/100, worse than 84% of steel grades
SM400A-N properties
Typical room-temperature values for SM400A-N; 23 are specific to this condition. Other listed values are SM400A reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SM400A-N 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
SM400A-N has a yield strength of 285 MPa (41.3 ksi) and a tensile strength of 445 MPa (64.5 ksi) — weaker than 89% of steel grades. Elongation at break is 29% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SM400A-N is rated for continuous service to 350°C (662 °F). It conducts heat at 51 W/m·K (29.5 BTU/hr·ft·°F), better than 92% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
SM400A-N conducts electricity at 10.8 % IACS, better than 94% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of SM400A-N takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
SM400A-N's machinability is good (66/100, better than 95% of steel grades); weldability excellent (95/100); formability very good (84/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SM400A-N
Is SM400A easy to machine?
Machines easily but gummy — use positive-rake tools, moderate speeds and good coolant; expect built-up edge and stringy chips typical of low-carbon steel.
Can SM400A be welded?
Excellent weldability by SMAW/GMAW/SAW with E70-class consumables; low carbon equivalent means no preheat below ~25 mm thickness in normal conditions.
Can SM400A be formed, bent or molded?
Good cold bending and press-brake behaviour (r ≈ 1.5–2 t); hot forming 900–1150 °C, normalize afterwards for thick sections.
What surface finishes work on SM400A?
No anodizing; blast to Sa 2½ then epoxy/zinc-rich primer, hot-dip galvanize or metallize — bare surfaces rust within days outdoors.
SM400A 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≤0.23 % for t ≤ 50 mm; ≤0.25 % for t > 50 mm (JIS G 3106) | ≤ 0.23 | 0.17 |
| MnMin 2.5 × C (no upper limit specified for SM400A) | ≈ 0.6 | 0.6 |
| SiNot specified for SM400A; typical mill practice | ≈ 0.2 | 0.2 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.04 | 0.01 |
| Fe | balance | — |
SM400A-N — frequently asked
What is SM400A-N used for?
SM400A-N is typically used for bridges, buildings, shipbuilding and welded structures. In short: weld-qualified A36 equivalent; highest weldability in family; low strength, high ductility.
What is the yield strength of SM400A-N?
SM400A-N has a typical yield strength of 285 MPa (41.3 ksi) and a tensile strength of 445 MPa (64.5 ksi) — weaker than 89% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is SM400A-N easy to machine?
Reasonably — machinability is rated good (66/100, better than 95% of steel grades). Machines easily but gummy — use positive-rake tools, moderate speeds and good coolant; expect built-up edge and stringy chips typical of low-carbon steel.
Can SM400A-N be welded?
Yes — weldability is rated excellent (95/100). Excellent weldability by SMAW/GMAW/SAW with E70-class consumables; low carbon equivalent means no preheat below ~25 mm thickness in normal conditions.
What surface finishes work on SM400A-N?
No anodizing; blast to Sa 2½ then epoxy/zinc-rich primer, hot-dip galvanize or metallize — bare surfaces rust within days outdoors.
Can SM400A-N be formed, bent or molded?
Good cold bending and press-brake behaviour (r ≈ 1.5–2 t); hot forming 900–1150 °C, normalize afterwards for thick sections.
What is the maximum service temperature of SM400A-N?
SM400A-N 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 SM400A-HR and SM400A TMCP?
HR is the default condition — standard mill supply condition for plate, sections and flats — pick for general welded structures, buildings and bridge secondary members. TMCP: pick for heavy plate where low carbon equivalent (easier field welding, less preheat) plus good toughness is required. Yield strength is 275 MPa in HR versus 305 MPa in TMCP.
Sources
- JIS G 3106 — Rolled steels for welded structure — Japanese Standards Association (2020)
- ASTM A36/A36M — Carbon Structural Steel — ASTM International (2019)
- GB/T 700 — Carbon structural steels (Q235) — SAC (2006)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- worldsteel LCI data for steel products — World Steel Association (2023)
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.