Quick Reference Comparison Matrix

PRELIMINARY — NOT FOR CONSTRUCTION. Values are minimum specified properties. Actual certified mill values may differ. Must be independently verified by a licensed Professional Engineer before use in design.

Property A36 A572 Gr 50 A992 A588 A514
Fy (ksi) 36 50 50 50 100
Fy (MPa) 250 345 345 345 690
Fu min (ksi) 58 65 65 70 110
Fu min (MPa) 400 450 450 483 760
Fu/Fy min Not specified Not specified 1.18 Not specified Not specified
Fy/Fu typical ≤ 0.62 ~0.77 ≤ 0.85 ~0.71 ~0.83
CE typical 0.38–0.42 0.40–0.45 ≤ 0.45 0.40–0.50 0.45–0.65
Elongation (8 in) 20% 18% 18% 18% 14%
E (ksi) 29,000 29,000 29,000 29,000 29,000
Density (lb/ft³) 490 490 490 490 490
Seismic Ry 1.50 1.10 1.10 — —
CVN required No (std) No (Type 1) Groups 4–5 only Per order Per order
Relative cost 1.00 1.05 1.05 1.10 1.50
Product forms Plates, bars, shapes Plates, shapes, bars, sheet W-shapes only Plates, shapes Plates only

Detailed Grade Profiles

A36 — Carbon Structural Steel

Fy = 36 ksi (250 MPa) | Fu = 58 ksi (400 MPa)

The original workhorse of North American structural steel. A36 is a plain carbon steel with no intentional microalloying additions. Its primary advantage is the lowest cost and easiest weldability. Carbon equivalent is typically 0.38–0.42, well below preheat thresholds for most thicknesses.

Best for: Plates, angles, channels, bars, anchor rods, secondary framing where 36 ksi yield is adequate. Connection plates where bearing on concrete (not steel strength) governs.

Limitations: 39% lower strength than Grade 50 alternatives means heavier sections for the same capacity. Wide actual yield range (36–55+ ksi) creates uncertainty for capacity design. Not recommended for W-shapes in seismic applications.

A572 Grade 50 — HSLA Structural Steel

Fy = 50 ksi (345 MPa) | Fu = 65 ksi (450 MPa)

The high-strength low-alloy (HSLA) specification using columbium (niobium) and/or vanadium microalloying. Grade 50 is the standard upgrade from A36 for plates, gusset plates, and base plates where higher strength reduces section weight. Provides 39% more yield strength for approximately 5% cost premium.

Best for: Structural plates, gusset plates, base plates, stiffeners, tension members where plate thickness is controlled by steel strength. Sheet piling, bridge components, crane girders.

Limitations: No maximum Fy cap means yield strength can significantly exceed 50 ksi. For W-shapes, A992 is preferred because it adds Fy cap and CE limits. Type 2 (with CVN testing) adds cost and lead time.

A992 — W-Shape Standard

Fy = 50 ksi (345 MPa) | Fu = 65 ksi (450 MPa) | Fy max = 65 ksi

Adopted in 1998 as the dedicated specification for W-shapes. A992 combines the strength of A572 Gr 50 with additional controls: maximum Fy of 65 ksi, minimum Fu/Fy of 1.18, and maximum CE of 0.45 (for Groups 4–5). These controls make A992 the preferred grade for all W-shapes in building construction, especially seismic applications.

Best for: All W-shapes (beams, columns, bracing members) in building construction. Required by AISC 341 for W-shapes in special and intermediate moment frames.

Limitations: Specified only for W-shapes. Not available in plate, bar, or angle form. For connection plates, use A572 Gr 50.

A588 — Weathering Steel (Corten)

Fy = 50 ksi (345 MPa) | Fu = 70 ksi (483 MPa)

A588 is a high-strength low-alloy weathering steel that develops a protective oxide patina (rust layer) when exposed to atmosphere. The patina eliminates the need for painting in many environments, reducing lifecycle maintenance costs. Higher copper and chromium content provides the corrosion resistance but slightly increases the carbon equivalent, making preheat requirements somewhat higher than A572 Gr 50.

Best for: Unpainted bridges, exposed architectural steel, transmission towers, exterior structural steel where appearance and low maintenance are priorities. Sculptures and architectural features.

Limitations: Not suitable for buried or submerged conditions. The patina requires wet/dry cycling to form properly — not suitable for continuously wet environments. Higher cost (10–15% premium) and higher CE make welding slightly more demanding. Runoff staining on adjacent concrete and stone may be aesthetically unacceptable.

A514 — Quenched and Tempered Alloy Steel

Fy = 100 ksi (690 MPa) | Fu = 110–130 ksi (760–895 MPa)

A514 is a quenched and tempered (Q&T) alloy steel plate that achieves 100 ksi yield strength through heat treatment. The high strength allows dramatic reductions in plate thickness for heavy girders, crane components, and pressure vessels. However, A514 has significant fabrication constraints: high carbon equivalent (0.45–0.65), strict preheat requirements, limited maximum thickness (varies by grade), and reduced ductility (elongation = 14% vs. 18–20% for lower-strength grades).

Best for: Heavy plate girders, crane girders, mobile equipment, pressure vessels, wear plates. Applications where plate weight or thickness is the controlling constraint and the fabrication premium is justified.

Limitations: Highest cost (50%+ premium over A36). Demanding welding procedures with strict heat input control and post-weld requirements. Not available in standard structural shapes. Design must account for reduced ductility and potential for brittle fracture in thick sections. Not permitted in AISC 341 seismic applications without project-specific qualification.

Strength Comparison — All Grades in MPa and ksi

Grade Fy (ksi) Fy (MPa) Fu (ksi) Fu (MPa) Strength Gain vs A36
A36 36 250 58 400 Baseline
A572 Gr 42 42 290 60 415 +17%
A572 Gr 50 / A992 / A588 50 345 65–70 450–483 +39%
A572 Gr 55 55 380 70 483 +53%
A572 Gr 60 60 415 75 515 +67%
A572 Gr 65 65 450 80 550 +81%
A514 100 690 110 760 +178%

Weldability Comparison

Grade CE Range Preheat Threshold Electrode Notes
A36 0.38–0.42 t ≥ 3/4 in at 50°F E70XX Easily weldable for most structural applications
A572 Gr 50 0.40–0.45 t ≥ 3/4 in; 150°F for t > 1-1/2 in E70XX Standard procedures adequate
A992 0.40–0.45 Similar to A572 Gr 50 E70XX Formulated for weldability with CE cap
A588 0.40–0.50 Slightly higher than A572 E70XX or E80XX Use weathering-grade electrodes for matching patina
A514 0.45–0.65 150–400°F depending on thickness E110XX or E120XX Q&T steel — strict heat input limits; avoid exceeding temper temperature

Application Decision Matrix

If You Need... Use... Because...
W-shapes for building construction A992 Required by AISC; Fy cap + CE limits
Structural plates (3/16–6 in) A572 Gr 50 Best strength-to-cost ratio for plates
Gusset plate or base plate A572 Gr 50 (or A36 if bearing-governed) Higher Fy reduces plate thickness
Connection angles and channels A36 or A572 A36 adequate for many connection elements
Unpainted exterior steel A588 Weathering patina eliminates paint
Heavy plate girder (depth-limited) A514 100 ksi Fy minimizes flange thickness
Seismic special moment frame beam A992 Fy cap + controlled Ry required by AISC 341
Anchor rods (standard) A36 or F1554 Gr 36 Adequate strength; widely available
Anchor rods (high-strength) F1554 Gr 105 105 ksi yield; not covered by A572/A992
HSS sections A500 Gr B or C Separate ASTM spec for hollow sections

MPa to ksi Conversion Table

MPa ksi Common Grade
235 34.1 S235 (EN 10025)
250 36.3 A36, Grade 250 (AS/NZS)
275 39.9 S275 (EN 10025)
345 50.0 A572 Gr 50, A992, A588
355 51.5 S355 (EN 10025)
400 58.0 A36 Fu min
415 60.2 A572 Gr 42 Fu
450 65.3 A572 Gr 50 / A992 Fu
483 70.0 A588 Fu / E70XX electrode
690 100.1 A514 Fy
760 110.2 A514 Fu min

Conversion: MPa = ksi × 6.895 | ksi = MPa / 6.895

Worked Example — Grade Selection for a Multi-Story Building

Given: 6-story office building, SDC C, composite steel frame.

Beams (W-shapes): Use A992. All W-shapes default to A992 per current AISC practice. For typical composite floor beams (W18×35 through W24×55), A992 provides 50 ksi yield with controlled properties.

Columns (W-shapes): Use A992. For W14×90 through W14×233 columns, Groups 1–3. CVN not required per AISC A3.1c (tf ≤ 1.5 in).

Gusset plates (braced frame): Use A572 Gr 50. The 50 ksi yield reduces plate thickness vs. A36. For a typical X-brace gusset: A36 requires 3/4 in plate; A572 Gr 50 requires 5/8 in plate (17% thinner, 20% lighter).

Base plates: Use A572 Gr 50 if punching shear and plate bending govern thickness (typical). Use A36 if bearing on concrete controls and plate thickness is already at minimum for anchor rod clearance.

Exterior canopy beams: Use A588 if exposed and unpainted architectural finish is desired.

References