Material Guide

Best Steel for Construction: A36 vs A572 vs A500 Structural Steel Guide

By YKWiki Engineering Team · Published 2026-07-22

Quick Comparison: Structural Steel Grades

PropertyA36A572 Gr.50A500 Gr.B
Product FormPlate, W-shapesPlate, W-shapes, HPHSS (Round & Rect.)
Yield Strength (MPa)250345290 (round) / 317 (rect.)
Tensile Strength (MPa)400-550450+ (min)400+ (min)
Carbon Eqv. (max)0.50 (per spec)0.43 (Gr.50)0.45
WeldabilityExcellentGoodGood
Cost (per lb, relative)1.0×1.05-1.10×1.15-1.30×

A36: The Universal Structural Carbon Steel

ASTM A36 is the default structural steel in North American construction, accounting for the majority of steel tonnage in commercial buildings, bridges, and industrial structures. Its 250 MPa minimum yield strength is the baseline against which all other structural grades are measured. A36 is produced as wide-flange sections (W-shapes), channels, angles, plates, and bars — available from every domestic steel service center in every common size, with the shortest lead times and lowest prices.

The primary advantage of A36 is its weldability. With a carbon equivalent typically below 0.40, A36 can be welded without preheat in thicknesses up to 25 mm using standard E70XX electrodes. No post-weld heat treatment is required. This makes A36 the simplest and most economical steel for field welding, shop fabrication, and repair work. The forgivable nature of A36 welding — wide acceptable parameter ranges, minimal defect susceptibility — reduces fabrication labor costs significantly.

A36's limitation is its modest strength. At 250 MPa yield, A36 requires heavier sections than higher-strength alternatives, increasing both material weight and foundation loads. For multi-story buildings, long-span beams, and weight-critical structures, the 38% higher yield strength of A572 Gr.50 can reduce beam weight by 25-35%, often offsetting the modest material cost premium. See S275JR vs S355J2 for the European equivalent discussion.

A572 Grade 50: The High-Strength Low-Alloy Option

ASTM A572 Grade 50 is a high-strength low-alloy (HSLA) structural steel delivering 345 MPa minimum yield — 38% stronger than A36. The increased strength is achieved through microalloying with vanadium, niobium, or nitrogen rather than increased carbon content, preserving good weldability and toughness while reducing the weight of structural members. A572 Gr.50 is the standard specification for W-shapes produced by domestic mills (Nucor, SSAB, Gerdau) and is increasingly the default for new construction projects.

The economic case for A572 Gr.50 is compelling. Although the per-pound cost is 5-10% higher than A36, the 38% yield strength advantage allows lighter sections for the same design capacity. A W18×50 in A572 Gr.50 can replace a W21×57 in A36 — saving 12% in weight and reducing column loads, foundation size, and erection crane capacity requirements. For buildings over 5 stories and bridges with spans exceeding 20 m, the total project cost savings from A572 Gr.50 typically exceed 3-5% of structural steel cost.

Welding A572 Gr.50 requires slightly more attention than A36. The carbon equivalent is controlled to 0.43 maximum for Grade 50, which may require preheat for thicknesses above 25 mm or in cold-weather fabrication. Low-hydrogen welding practices (E7018 electrodes, properly stored consumables) are recommended. However, for the vast majority of building construction applications, A572 Gr.50 welds with the same procedures as A36.

A500 Grade B: Hollow Structural Sections

ASTM A500 Grade B is the specification for Hollow Structural Sections (HSS) — round, square, and rectangular tubes used as columns, braces, truss members, and architectural features in modern steel construction. The manufacturing process (cold-forming and electric-resistance welding) produces sections with superior compression efficiency: the closed cross-section provides equal radius of gyration in both axes, eliminating the weak-axis buckling that plagues wide-flange columns and drastically reducing the required member size for a given axial load.

For column design, an HSS6×6×3/8 in A500 Gr.B can replace a W8×31 wide-flange section in many applications — at roughly half the weight and with a smaller architectural footprint. The closed section also eliminates the dust-collecting, painting-difficult surfaces inside a wide-flange, reducing maintenance costs over the building life. The aesthetic appeal of exposed HSS trusses and braces has made A500 the default for architecturally expressive structures.

The cost premium for A500 Gr.B HSS over A36 wide-flange shapes is 15-30% per pound, reflecting the additional manufacturing steps (forming, welding, sizing). However, the weight savings from superior compression efficiency often result in equal or lower total member cost. The connection design for HSS is more complex — requiring through-plate, knife-plate, or collar connections that add fabrication labor — and must be considered in the total cost analysis.

Application-Specific Recommendations

Multi-Story Building Frames

Use A572 Gr.50 for beams and girders (W-shapes) and A500 Gr.B for columns and braces (HSS). This combination maximizes strength-to-weight and provides the compression efficiency that reduces column sizes and floor-to-floor heights.

Industrial and Warehouse Structures

Use A36 for simple-span roof beams, purlins, and girts where the modest strength is adequate and the lowest material cost drives the economics. Use A572 Gr.50 for crane runway beams and heavy column bases.

Bridge Construction

Use A572 Gr.50 for primary girders and floor beams. The 38% higher yield strength reduces dead load, which directly translates to longer spans or lighter foundations. For fracture-critical members, specify A572 with Charpy V-Notch toughness requirements per AASHTO.

Architectural and Exposed Structures

Use A500 Gr.B HSS for exposed trusses, canopies, and architectural features. The clean lines and bi-directional section properties produce visually elegant structures with minimal maintenance surfaces.

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Frequently Asked Questions

Is A572 Gr.50 replacing A36 in construction?

Yes. Most domestic steel mills now produce W-shapes as dual-certified A36/A572 Gr.50, and the trend is toward A572 Gr.50 as the default specification. The 38% higher yield strength allows 25-35% weight reduction in beams, reducing foundation loads and total project cost. A36 remains specified for simple structures, repair work, and projects where fabricators prefer its more forgiving weldability.

Why are HSS sections more efficient as columns?

HSS (Hollow Structural Sections) have equal radius of gyration about both axes, meaning they resist buckling equally in all directions. A W-shape column has a weak axis (r_y ≈ 40-60% of r_x), requiring bracing or larger sections to prevent weak-axis buckling. For the same axial capacity, an HSS column can be 30-50% lighter than an equivalent W-shape column.

Can you weld A572 Gr.50 to A36?

Yes, it is common practice. Use E70XX filler metal matching the lower-strength base metal (A36). The weld metal strength will exceed the A36 base metal, providing a conservative joint. For thick sections (>25 mm), preheat per AWS D1.1 Table 3.2 based on the higher carbon equivalent material.

What is the cost difference between A36 and A572 Gr.50?

A572 Gr.50 costs approximately 5-10% more per pound than A36. However, because A572 Gr.50 provides 38% higher yield strength, the required section weight for a given design capacity is typically 25-35% less. The net result is that A572 Gr.50 structures are often 3-5% cheaper in total structural steel cost than equivalent A36 designs.

Why isn't A500 HSS available in all sizes?

A500 HSS is produced by cold-forming and ERW welding flat strip into tube, which limits the available size range compared to hot-rolled W-shapes. Very large HSS sections (over 20 inches) are produced in limited quantities by fewer manufacturers, with longer lead times and higher costs. For large column loads requiring heavy sections, W-shapes in A572 Gr.50 remain more practical and economical.

References & Standards