What is A572 Grade 50 Properties used for in structural engineering?

A572 Grade 50 Properties provides values required for steel design calculations including capacity checks, connection design, and detailing. It is referenced in structural design codes and used by practicing engineers during the design of buildings, bridges, and industrial structures.

Can I use these reference values directly in my design?

Yes, provided the values match your governing code edition and project specifications. Always cross-reference against the primary source (code document, manufacturer data, or published standard). The information on this page is for educational use — final verification by a licensed engineer is required.

How often are these reference values updated?

Reference content is maintained to align with current code editions. When a new edition of AISC 360, AS 4100, EN 1993, or CSA S16 is published, values are reviewed and updated. Check the last-modified date at the bottom of the page and verify against the current edition for your jurisdiction.

A572 Grade 50 Steel Properties — Yield Strength, Tensile Strength & Applications

ASTM A572 Grade 50 is a high-strength low-alloy (HSLA) structural steel with a yield strength of 50 ksi (345 MPa) and tensile strength of 65 ksi (450 MPa). It is the most commonly specified grade of the A572 family for plates, bars, and structural shapes. This page covers A572 Grade 50 mechanical properties, chemical composition, comparison with A992, and AISC 360 design guidance.

Quick access: A992 Steel → | A588 Weathering → | Column Calculator → | Section Properties →

A572 Grade 50 Mechanical Properties

Yield and Tensile Strength

Property	Imperial	Metric	AISC 360 Symbol
Yield strength (Fy)	50 ksi	345 MPa	Fy
Tensile strength (Fu)	65 ksi	450 MPa	Fu
Modulus of elasticity (E)	29,000 ksi	200,000 MPa	E
Shear modulus (G)	11,200 ksi	77,200 MPa	G
Poisson's ratio	0.30	0.30	—
Density	490 lb/ft³	7,850 kg/m³	—

Elongation Requirements

Specimen	Minimum Elongation
8-inch gauge length	18%
2-inch gauge length	21%

Complete A572 Grade Family

A572 covers five grades with increasing strength:

Grade	Fy (ksi)	Fu (ksi)	Fy (MPa)	Fu (MPa)	Common Use
Grade 42	42	60	290	415	Light structures
Grade 50	50	65	345	450	Most common HSLA
Grade 55	55	70	380	485	Higher strength plates
Grade 60	60	75	415	520	Heavy construction
Grade 65	65	80	450	550	Maximum strength

Grade 50 accounts for over 80% of all A572 production. When engineers say "A572" without specifying a grade, they almost always mean Grade 50.

A572 Grade 50 Chemical Composition

Element	Grade 50 Max (%)	Grade 50 Typical (%)
Carbon (C)	0.23	0.18
Manganese (Mn)	1.35	1.00
Phosphorus (P)	0.035	0.02
Sulfur (S)	0.04	0.025
Silicon (Si)	0.40	0.25
Copper (Cu)	0.20 min	0.30
Vanadium (V)	0.15	0.04
Columbium (Nb)	0.05	0.02

HSLA Alloying Strategy

A572 Grade 50 achieves its higher strength through micro-alloying with vanadium and columbium (niobium), not through higher carbon content. Benefits include:

Low carbon (max 0.23%) — Excellent weldability
Vanadium/Columbium — Grain refinement and precipitation strengthening
Higher manganese — Improved toughness and strength

Weldability

A572 Grade 50 has good weldability due to its low carbon content.

Preheat Requirements

Thickness	Preheat (AWS D1.1)
Up to 3/4 in. (19 mm)	Not required (above 32°F)
3/4 to 1-1/2 in. (19-38 mm)	50°F (10°C) minimum
1-1/2 to 2-1/2 in. (38-64 mm)	150°F (65°C) minimum
Over 2-1/2 in. (64 mm)	200°F (93°C) minimum

Electrode Selection

Use matching-strength electrodes (70 ksi tensile):

SMAW: E7018, E7016
FCAW: E71T-1, E70T-1
GMAW: ER70S-6
SAW: F7A2-EM12K

A572 Grade 50 vs A992

These grades have identical Fy (50 ksi) and Fu (65 ksi):

Attribute	A572 Grade 50	A992
Product forms	Plates, bars, shapes	W-shapes, M-shapes, S-shapes
Fy/Fu ratio	No requirement	0.85 max
Charpy testing	Supplementary available	Supplementary available
Mill certification	Standard	Tighter controls
Cost	Same	Same
Availability	Plate mills	Section mills

Rule of thumb:

W-shapes: Always use A992 (standard mill product)
Plates: Use A572 Grade 50 (available from plate mills)
Bars and shapes: Use A572 Grade 50 (available in angles, channels)

When to Use A572 Grade 50

Recommended Applications

Application	Why A572-50
Welded plate girders	Higher strength reduces plate thickness
Crane runway beams	Better fatigue resistance than A36
Heavy columns	Higher strength for compression members
Connection plates	Reduced thickness for high-load connections
Bridge components	Standard bridge steel (A709-50 is similar)
Base plates	When A36 is too thick for the load

When A36 is Sufficient

Standard base plates (economy)
Connection plates with low demand
Secondary framing
Non-critical applications

When to Upgrade Beyond A572-50

A572 Grade 60 or 65: When Grade 50 plate thickness exceeds available stock
A588: When weathering (unpainted) steel is required
A514 (quenched and tempered): When extreme strength is needed

AISC 360 Design with A572 Grade 50

Worked Example — Plate Girder Flange

Problem: Design the compression flange of a welded plate girder using A572 Grade 50 steel. Required moment: 1,500 kip-ft.

Given:

Girder depth: 60 inches
Concrete slab provides continuous lateral support
Compact section (no local buckling)

Solution:

Required Sx = M/phiFy = (1,500 × 12)/(0.90 × 50) = 400 in³
Flange: 1.25" x 18" plate (Ag = 22.5 in²)
Flange contribution to Sx: approximately 2 × 22.5 × 29.4 = 1,323 in³
Web contribution: 0.5" x 57.5" plate, Sx_web = 0.5 × 57.5²/6 = 276 in³
Total Sx ≈ 1,599 in³ > 400 in³ — OK

Worked Example — Column Design

Problem: Check an HSS 8x8x1/2 column, A572 Grade 50, KL=15 ft.

Given:

HSS 8x8x1/2: Ag = 13.5 in², rx = ry = 3.06 in
KL = 15 ft = 180 in

Solution:

KL/r = 180/3.06 = 58.8
Fe = π²E/(KL/r)² = π²(29,000)/58.8² = 82.7 ksi
Fy/Fe = 50/82.7 = 0.604 < 2.25
Fcr = 0.658^0.604 × 50 = 0.744 × 50 = 37.2 ksi
Pn = Fcr × Ag = 37.2 × 13.5 = 502 kips
LRFD: phiPn = 0.90 × 502 = 452 kips
ASD: Pn/Omega = 502/1.67 = 300 kips

Calculator

Design steel members with A572 Grade 50 using our free calculators:

Beam Capacity Calculator → — Check flexural strength for plate girders
Column Buckling Calculator → — AISC compression with KL/r
Bolted Connection Calculator → — High-strength connection design
Section Properties → — Full AISC section database

FAQ

Q: What is the yield strength of A572 Grade 50? A: ASTM A572 Grade 50 has a minimum yield strength of 50 ksi (345 MPa) and a minimum tensile strength of 65 ksi (450 MPa). These values are the same as A992.

Q: What is the difference between A572 Grade 50 and A992? A: Both have identical Fy (50 ksi) and Fu (65 ksi). A992 has an additional Fy/Fu ratio requirement (0.85 max) that A572 does not. A992 is for W-shapes only; A572 Grade 50 is for plates, bars, and shapes.

Q: Can I weld A572 Grade 50 without preheat? A: For thicknesses up to 3/4 inch (19 mm), preheat is generally not required above 32°F (0°C). For thicker sections, follow AWS D1.1 preheat tables. Always use low-hydrogen electrodes (E7018 or equivalent).

Q: Is A572 Grade 50 a weathering steel? A: No, A572 Grade 50 is not a weathering steel. It will corrode like ordinary carbon steel and requires painting or other corrosion protection. For weathering applications, use A588 or A709-50W.

Q: What is the difference between A572 Grade 50 and Grade 65? A: Grade 50 has Fy=50 ksi and Fu=65 ksi. Grade 65 has Fy=65 ksi and Fu=80 ksi. Grade 65 is 30% stronger but more expensive and less available. Use Grade 65 only when Grade 50 plate thickness is excessive.

Q: Can I substitute A572 Grade 50 for A36? A: A572 Grade 50 is stronger (50 ksi vs 36 ksi yield) and can replace A36 in most applications. However, verify that the higher strength does not change the governing limit state (e.g., deflection may control over strength). The cost difference is typically 5-10%.