Carbon steels

A572 Grade 50 Steel

Also: ASTM A572 Gr 50, A572-50, Grade 50 plate, 50 ksi steel, HSLA steel, high-strength low-alloy steel, ASME SA-572, A992 (W shapes, equivalent), S355 / 1.0577 (near), A572 Grade 50 plate

A572 Grade 50 is the high-strength structural steel: 345 MPa (50 ksi) minimum yield from a columbium-vanadium microalloy, fabricated like A36 at a small premium.

ASTM A572/A572M (HSLA columbium-vanadium structural steel)ASME SA-572ASTM A992 (rolled W shapes, same strength class)AWS D1.1 (welding)AISC Steel Construction Manual

Sourcing A572-50 parts or stock?

Attach a drawing (PDF or STEP) or describe the part; a U.S. shop that fits quotes it.

At a glance

A572 Grade 50 Steel typical properties
Density	7.85 g/cm³ (0.284 lb/in³)
Tensile strength	450 MPa (65 ksi) minimum; typically 480-550 MPa (70-80 ksi) as rolled
Yield strength	345 MPa (50 ksi) minimum; typically 360-415 MPa (52-60 ksi) as rolled
Hardness	About 140-170 HB as rolled
Elongation	18% minimum in 200 mm (8"); 21% minimum in 50 mm (2")
Modulus of elasticity	200 GPa (29 Msi)
Thermal	Melts at about 1,480-1,520 °C (2,700-2,770 °F); do not hot form above about 650 °C (1,200 °F) without re-verifying properties
Composition	Fe, up to 0.23% C, up to 1.35% Mn, 0.005-0.05% Cb (Nb) and/or 0.01-0.15% V, up to 0.40% Si, up to 0.04% P, up to 0.05% S

Typical values, Hot rolled, as delivered, Grade 50 (spec minimums and typical as-rolled values). Confirm against the mill certificate and the purchase spec.

MachinabilityFair: Similar to A36, a bit harder: about 65% of the 1212 benchmark on clean metal. Drilling, tapping and facing on weldments are routine; it is not bought for precision machining.
WeldabilityExcellent: Low carbon equivalent (typically under 0.45): E70 consumables, no preheat below about 20 mm (3/4"), modest preheat on heavier sections. Match the filler strength (E70 or E80) to the design.
FormabilityGood: Bends on a press brake at about 1.5-2x thickness inside radius, a step larger than A36, with more springback. Cold forming below 5x thickness radius benefits from bending across the grain.
Corrosion resistancePoor: Rusts like A36. Blast, prime and paint, powder coat or galvanize; specify copper-bearing or weathering (A588) steel if a rust patina is the intent.

A572 is a high-strength low-alloy (HSLA) structural steel. Small additions of columbium (niobium) and vanadium, with controlled rolling at the mill, refine the grain and lift the minimum yield to 345 MPa (50 ksi) in Grade 50, the grade almost everyone buys. Carbon stays low, so it welds, cuts and forms like A36 with only slightly more effort.

It is the plate of choice when weight or section size matters: cranes, booms, truck and trailer frames, heavy equipment weldments, bridges and buildings. A Grade 50 part designed for strength can be about 30% thinner than the A36 version, which saves steel, welding and shipping. Wide-flange beams are now rolled to A992, the same strength class, so "Grade 50" and "A992" get used interchangeably on structural drawings.

The strength comes from the mill process, not from carbon, so it cannot be heat treated to anything higher and it must not be reheated far above about 650 °C (1,200 °F) during forming or it loses what the mill put in. Formability is a step below A36: bend radii are larger and springback is higher. Machinability is similar to A36, meaning fine for holes and pads and poor for precision parts.

Heat treatment

None. The strength is built in by microalloying and controlled rolling and cannot be improved by quench and temper; heating above roughly 650 °C (1,200 °F), as in hot forming or a full anneal, coarsens the grain and drops the yield toward A36 values. Stress relieve weldments at 590-620 °C (1,100-1,150 °F) when they will be machined afterward, and keep the temperature below the mill's limit, which some producers set at 600 °C.

Tempers and conditions

Hot rolled, as rolled (as stocked)
Normalized (thick plate, by agreement)
Stress relieved (weldments)

Stock forms

Plate 5 mm to 100 mm (3/16" to 4") and heavier
Wide flange, angle and channel (A992 or A572)
Flat and round bar
Cut-to-length and laser-grade plate

Relative cost

Tier 1 of 5. Roughly 5-10% over A36 by weight, and often cheaper per part because the section is thinner. Availability in plate and shapes is as good as A36.

Typical applications

Crane booms, outriggers and lifting structures
Truck, trailer and rail car frames
Heavy equipment weldments and buckets
Bridges, buildings and transmission towers
Pressure-retaining structural attachments (not pressure vessels)
Machine bases where thinner plate saves weight

Process compatibility

How A572-50 takes each process, and what to specify. Each process links to its own guide and to the shops that do it.

A572 Grade 50 Steel process compatibility
Process	Rating	Notes
Welding	ExcellentExcellent	E70/E80 consumables, little or no preheat; the standard high-strength fab steel under AWS D1.1.
Robotic Welding	ExcellentExcellent	Runs like A36 in a cell; use E70 or E80 wire depending on joint design.
Plasma Cutting	ExcellentExcellent	Cuts as fast as A36; the cut edge hardens slightly more.
Laser Cutting	GoodGood	Clean oxygen-assist cuts to about 25 mm (1"); good laser-grade plate is available.
Waterjet Cutting	GoodGood	No heat-affected zone, useful for edges that will be bent tight or tapped.
Press Brake Forming	GoodGood	Inside radius 1.5-2x thickness; plan for more springback than A36.
Hot-Dip Galvanizing	ExcellentExcellent	Hot-dip per ASTM A123; the same silicon caution as A36 for cosmetic coatings.
Powder Coating	GoodGood	Blast to remove scale, zinc-rich primer for outdoor service.
Stress Relieving	GoodGood	590-620 °C for weldments machined after welding; stay below the mill's stated limit.
CNC Machining	FairFair	Drill, tap and face on weldments; not a precision stock.
Heat Treating	Not recommendedNot recommended	Quench and temper does not raise it and a full anneal lowers it; the strength is from the rolling process.
Induction Hardening	Not recommendedNot recommended	Too little carbon for a useful case; add a hardened wear plate instead.

Design and sourcing tips

Design to 345 MPa (50 ksi) yield and take the thinner section; that is the whole point of paying for Grade 50.
Specify "ASTM A572 Grade 50" on plate and accept A992 for rolled W shapes; the strengths match and mills roll to A992.
Call for larger bend radii than A36 (1.5-2x thickness) and expect springback; tight flanges are cheaper welded than bent.
Do not let a shop hot form or flame straighten above about 650 °C (1,200 °F) without a procedure; the yield drops toward A36.
Match filler to design: E70 is fine for most joints, E80 when the weld must develop the full base-metal strength.
For weathering service specify A588 instead; A572 rusts like A36.

Frequently asked questions

What is the difference between A36 and A572 Grade 50?: Both are hot-rolled structural steels fabricated the same way. A572 Grade 50 is microalloyed with columbium and vanadium for a 345 MPa (50 ksi) minimum yield versus 250 MPa (36 ksi) for A36, at a few percent more per pound. Grade 50 lets you use a thinner, lighter section; A36 bends a little tighter and is the safer default for parts that are stiffness-driven anyway.
Can A572 Grade 50 be welded?: Yes, very easily. Its carbon equivalent is low, so it welds with E70 or E80 consumables and needs little or no preheat except on thick sections. AWS D1.1 lists it as a prequalified base metal. Use E80 filler when the weld must match the base-metal strength.
Can A572 be heat treated or hardened?: No. The strength comes from grain refinement during controlled rolling, not from carbon, so quench and temper adds nothing and a full anneal or hot forming above about 650 °C (1,200 °F) makes it weaker. Buy it for its as-rolled strength and use 4140 or 1045 when a part needs hardening.
Is A572 Grade 50 the same as A992?: Functionally yes for rolled shapes. A992 is the spec written for wide-flange beams with the same 50 ksi minimum yield and a capped yield-to-tensile ratio; A572 covers plate, bar and shapes. Structural drawings that say "Grade 50" are usually satisfied by A992 beams and A572 plate.

Processes that commonly use it

Laser Cutting Waterjet Cutting Plasma Cutting Sheet Metal Fabrication Press Brake Forming Metal Stamping Progressive Die Stamping Roll Forming Welding MIG Welding Robotic Welding Powder Coating E-Coating (Electrocoating)Hot-Dip Galvanizing Stress Relieving

Related materials

A36 Steel 4130 Steel 1045 Steel 1018 Steel 2205 Duplex Stainless Steel

Where to verify these values

ASTM A572/A572M (grades, chemistry and minimums)
ASTM A992/A992M and ASTM A6/A6M
AISC Steel Construction Manual
AWS D1.1 Structural Welding Code, Steel

A572 Grade 50 Steel

Also: ASTM A572 Gr 50, A572-50, Grade 50 plate, 50 ksi steel, HSLA steel, high-strength low-alloy steel, ASME SA-572, A992 (W shapes, equivalent), S355 / 1.0577 (near), A572 Grade 50 plate

A572 Grade 50 is the high-strength structural steel: 345 MPa (50 ksi) minimum yield from a columbium-vanadium microalloy, fabricated like A36 at a small premium.

ASTM A572/A572M (HSLA columbium-vanadium structural steel)ASME SA-572ASTM A992 (rolled W shapes, same strength class)AWS D1.1 (welding)AISC Steel Construction Manual

At a glance

A572 Grade 50 Steel typical properties
Density	7.85 g/cm³ (0.284 lb/in³)
Tensile strength	450 MPa (65 ksi) minimum; typically 480-550 MPa (70-80 ksi) as rolled
Yield strength	345 MPa (50 ksi) minimum; typically 360-415 MPa (52-60 ksi) as rolled
Hardness	About 140-170 HB as rolled
Elongation	18% minimum in 200 mm (8"); 21% minimum in 50 mm (2")
Modulus of elasticity	200 GPa (29 Msi)
Thermal	Melts at about 1,480-1,520 °C (2,700-2,770 °F); do not hot form above about 650 °C (1,200 °F) without re-verifying properties
Composition	Fe, up to 0.23% C, up to 1.35% Mn, 0.005-0.05% Cb (Nb) and/or 0.01-0.15% V, up to 0.40% Si, up to 0.04% P, up to 0.05% S

Typical values, Hot rolled, as delivered, Grade 50 (spec minimums and typical as-rolled values). Confirm against the mill certificate and the purchase spec.

MachinabilityFair

Similar to A36, a bit harder: about 65% of the 1212 benchmark on clean metal. Drilling, tapping and facing on weldments are routine; it is not bought for precision machining.

WeldabilityExcellent

Low carbon equivalent (typically under 0.45): E70 consumables, no preheat below about 20 mm (3/4"), modest preheat on heavier sections. Match the filler strength (E70 or E80) to the design.

FormabilityGood

Bends on a press brake at about 1.5-2x thickness inside radius, a step larger than A36, with more springback. Cold forming below 5x thickness radius benefits from bending across the grain.

Corrosion resistancePoor

Rusts like A36. Blast, prime and paint, powder coat or galvanize; specify copper-bearing or weathering (A588) steel if a rust patina is the intent.

Heat treatment

Process compatibility

How A572-50 takes each process, and what to specify. Each process links to its own guide and to the shops that do it.

A572 Grade 50 Steel process compatibility
Process	Rating	Notes
Welding	ExcellentExcellent	E70/E80 consumables, little or no preheat; the standard high-strength fab steel under AWS D1.1.
Robotic Welding	ExcellentExcellent	Runs like A36 in a cell; use E70 or E80 wire depending on joint design.
Plasma Cutting	ExcellentExcellent	Cuts as fast as A36; the cut edge hardens slightly more.
Laser Cutting	GoodGood	Clean oxygen-assist cuts to about 25 mm (1"); good laser-grade plate is available.
Waterjet Cutting	GoodGood	No heat-affected zone, useful for edges that will be bent tight or tapped.
Press Brake Forming	GoodGood	Inside radius 1.5-2x thickness; plan for more springback than A36.
Hot-Dip Galvanizing	ExcellentExcellent	Hot-dip per ASTM A123; the same silicon caution as A36 for cosmetic coatings.
Powder Coating	GoodGood	Blast to remove scale, zinc-rich primer for outdoor service.
Stress Relieving	GoodGood	590-620 °C for weldments machined after welding; stay below the mill's stated limit.
CNC Machining	FairFair	Drill, tap and face on weldments; not a precision stock.
Heat Treating	Not recommendedNot recommended	Quench and temper does not raise it and a full anneal lowers it; the strength is from the rolling process.
Induction Hardening	Not recommendedNot recommended	Too little carbon for a useful case; add a hardened wear plate instead.

Design and sourcing tips

Design to 345 MPa (50 ksi) yield and take the thinner section; that is the whole point of paying for Grade 50.

Specify "ASTM A572 Grade 50" on plate and accept A992 for rolled W shapes; the strengths match and mills roll to A992.

Call for larger bend radii than A36 (1.5-2x thickness) and expect springback; tight flanges are cheaper welded than bent.

Do not let a shop hot form or flame straighten above about 650 °C (1,200 °F) without a procedure; the yield drops toward A36.

Match filler to design: E70 is fine for most joints, E80 when the weld must develop the full base-metal strength.

For weathering service specify A588 instead; A572 rusts like A36.

Frequently asked questions

What is the difference between A36 and A572 Grade 50?

Both are hot-rolled structural steels fabricated the same way. A572 Grade 50 is microalloyed with columbium and vanadium for a 345 MPa (50 ksi) minimum yield versus 250 MPa (36 ksi) for A36, at a few percent more per pound. Grade 50 lets you use a thinner, lighter section; A36 bends a little tighter and is the safer default for parts that are stiffness-driven anyway.

Can A572 Grade 50 be welded?

Yes, very easily. Its carbon equivalent is low, so it welds with E70 or E80 consumables and needs little or no preheat except on thick sections. AWS D1.1 lists it as a prequalified base metal. Use E80 filler when the weld must match the base-metal strength.

Can A572 be heat treated or hardened?

No. The strength comes from grain refinement during controlled rolling, not from carbon, so quench and temper adds nothing and a full anneal or hot forming above about 650 °C (1,200 °F) makes it weaker. Buy it for its as-rolled strength and use 4140 or 1045 when a part needs hardening.

Is A572 Grade 50 the same as A992?

Functionally yes for rolled shapes. A992 is the spec written for wide-flange beams with the same 50 ksi minimum yield and a capped yield-to-tensile ratio; A572 covers plate, bar and shapes. Structural drawings that say "Grade 50" are usually satisfied by A992 beams and A572 plate.