A36 steel (K02600): properties, composition, equivalents

ASTM A36 steel (UNS K02600): the standard US structural carbon steel — 250 MPa (36 ksi) minimum yield, 400–550 MPa (58–80 ksi) tensile. Composition by product, thickness effects, A36 vs A572 / 1018 / S235JR, and SS400/Q235 equivalents.

What is A36?

ASTM A36 is the default structural carbon steel of North America: 250 MPa (36 ksi) minimum yield and 400–550 MPa (58–80 ksi) tensile for plate, shapes and bar, UNS K02600. Introduced in 1960 to replace A7, it defines what American engineers mean by 'mild steel' — cheap, ductile (20 % elongation in 200 mm), easily welded, bent and machined, and available from every service center as plate, angle, channel, flat and round. Chemistry is deliberately loose (carbon up to 0.25–0.29 % depending on thickness, no carbon-equivalent limit) because the specification guarantees mechanical properties rather than composition.

Since the late 1990s W-shapes (wide-flange beams) are almost exclusively rolled to A992 (345 MPa), and A572 Grade 50 has taken over much of the plate market where weight matters, so A36 today lives in plate up to 25 mm, angles, channels, bars, base plates, stiffeners and general fabrication. Bridge work uses A709 Grade 36, which adds Charpy zones; pressure vessels use A516, not A36.

The European counterpart is S235JR (weaker) or S275JR (stronger); JIS SS400, GB Q235B, GOST St3sp and IS 2062 E250 are the near or identical matches listed below. Note that A36 is not a bar grade like 1018: it specifies strength, 1018 specifies chemistry.

A36 chemical composition

ASTM A36/A36M-19 Table 2; limits vary with product and thickness (values shown are the most common). A36 is a 'loose' specification: no CE limit, no grain-size or impact requirement unless supplementary requirements are ordered.

A36 mechanical properties

ASTM A36/A36M-19 Table 3; yield is a minimum (no maximum), tensile a range; elongation in 200 mm (8 in) or 50 mm (2 in). Yield-to-tensile ratio typically 0.65–0.75. Charpy not required — order supplementary S5 (Charpy) or use A709 for impact-critical work.

Impact toughness

A36 requires a minimum Charpy V-notch energy of 27 J at 20 °C (typical only; not a standard requirement). Typical A36 gives 27 J at around −10 to +10 °C for plate ≤ 25 mm, but nothing is guaranteed. Bridges use A709 (which includes Charpy zones) rather than A36.

A36 equivalent grades

Identical = same composition and mechanical limits within rounding. Near = one limit differs (e.g. carbon max or impact temperature). Functional = interchangeable for most uses after an engineering check. Full cross-reference for A36 →

Old and superseded designations

Product forms and tolerance standards

Product forms: plate (all thicknesses; yield drops to 220 MPa above 200 mm), shapes: W, S, M, C, L, HP sections (A36 largely replaced by A992 for W-shapes since ~2000), bar: flats, rounds, squares (hot-rolled merchant bar), sheet piling is A328; hollow sections are A500, not A36.

Dimensional tolerances: plate: ASTM A6/A6M (thickness, flatness, camber); shapes and bar: ASTM A6/A6M; surface: A6 (mill scale as-rolled unless pickled/blasted).

Key property values

A36 yield strength

Minimum 250 MPa (36 ksi) for plate ≤ 200 mm, shapes and bar; 220 MPa (32 ksi) for plate over 200 mm. Typical mill values 280–340 MPa (40–49 ksi); no maximum is specified.

A36 tensile strength

400–550 MPa (58–80 ksi); typical 450–500 MPa. Heavy shapes (> 634 kg/m) have no upper limit.

A36 elongation

≥ 20 % in 200 mm (8 in) or ≥ 23 % in 50 mm (2 in); typical 28–34 % in 50 mm.

A36 hardness

Not specified; typical 119–159 HB (≈ 67–85 HRB) as rolled. Cannot be usefully hardened (C ≤ 0.25 %); flame-cut edges may reach 250–300 HV locally.

A36 density and modulus

Density 7.85 g/cm³ (0.284 lb/in³), E = 200 GPa (29 × 10⁶ psi), G = 77 GPa, Poisson 0.26–0.30, thermal expansion 11.7 × 10⁻⁶/K (6.5 × 10⁻⁶/°F), conductivity ≈ 50 W/m·K. AISC design values: Fy = 36 ksi, Fu = 58 ksi.

A36 weldability

Excellent — CE typically 0.30–0.40; prewelded with E70XX/ER70S-6 without preheat up to about 40 mm (AWS D1.1 Table 3.3: no preheat ≤ 19 mm, 10 °C to 38 mm, 65 °C to 64 mm, 110 °C above).

Weldability

One of the most weldable structural steels: SMAW E7018/E6010, GMAW ER70S-6, FCAW E71T-1, SAW F7A2-EM12K, all matching AWS D1.1 prequalified procedures. Preheat per AWS D1.1 Table 3.3 by thickness (none ≤ 19 mm). No PWHT for structural work; ASME SA-36 vessels may require stress relief per code thickness. Heavy plate (> 50 mm) with carbon near 0.27–0.29 % benefits from 65–110 °C preheat and low-hydrogen electrodes.

Machining, forming and heat treatment

Machinability ≈ 72 % of B1112 (hot-rolled) — gummy like other low-carbon steels; use positive rake and chip breakers. Flame, plasma, laser and waterjet cutting are routine; shearing to 25 mm; punching to ~19 mm. Cold bending: inside radius ≥ 1.5 t transverse per AISC guidance (1 t for thin plate); hot forming 900–1100 °C. Galvanizes well (check Si + 2.5 P for Sandelin effect on bright coatings); paints readily after blast cleaning (SSPC-SP6/SP10).

Typical applications

• Building and industrial steelwork: angles, channels, base plates, stiffeners, gussets, connection plates
• General fabrication: frames, skids, tanks (non-pressure), hoppers, chutes, guards
• Machinery bases, weldments, jigs and fixtures
• Bridge components as A709 Grade 36 (with Charpy)
• Bar stock for brackets, anchor bolts (A307 uses A36-type steel), tie rods
• Cold-formed light-gauge components (as A1011 SS36 in sheet)
• Ship structure secondary members (ABS Grade A is the marine equivalent)

A36 compared with related grades

Frequently asked questions

Related grades

Verified against ASTM A36/A36M-19; ASTM A36/A36M-19 Tables 2 and 3; ASTM A6/A6M-23; AWS D1.1:2020 Table 3.3; AISC Manual (design values). Last checked: September 2026.