A572 Carbon Steel Grades 42, 50, 55, 60 & 65 Compared
ASTM A572/A572M covers five high-strength low-alloy structural-steel grades identified by their minimum yield strength: 42, 50, 55, 60 and 65 ksi. Grade 50 is the most practical starting point for many ordinary structural applications, but the correct specification still depends on product form, thickness, connection method, toughness, availability and whether strength—or stiffness—actually controls the design.
It combines a 50 ksi minimum yield strength with broad familiarity in structural fabrication. Confirm the required product form and actual mill availability.
Grades 42 through 65 share essentially the same elastic modulus. Upgrading yield strength does not directly reduce service-load deflection.
AISC recommends ASTM A992/A992M for modern W-shapes because it adds tighter controls on yield, tensile behavior and carbon equivalent.
The base A572 specification does not automatically provide a project-specific notch-toughness value. State temperature, energy, orientation and test location.
What is A572 carbon steel?
“A572 carbon steel” is common shop language, but ASTM A572/A572M is technically a high-strength low-alloy (HSLA) structural-steel specification. The active 2025 edition covers shapes, plates, sheet piling and bars in Grades 42 [290], 50 [345], 55 [380], 60 [415] and 65 [450]. The bracketed numbers are the corresponding minimum yield strengths in megapascals.
The grade number describes a strength level, not a completely separate alloy family. Producers obtain that strength with controlled chemistry and microalloying additions such as niobium—historically called columbium—vanadium, titanium and nitrogen. These additions support grain refinement and precipitation strengthening without turning the material into a high-alloy steel.
The standard states that Grades 42, 50 and 55 are intended for riveted, bolted or welded structures. Grades 60 and 65 are intended for riveted or bolted bridge construction, or for riveted, bolted or welded construction in other applications. That scope statement is one reason a bridge material should be selected through the applicable bridge specification and owner requirements rather than from yield strength alone.
The designation must be complete
Writing only “A572” leaves the strength level undefined. A usable purchase description begins with the current specification and grade, then adds product form, dimensions, delivery condition, required testing and any supplementary requirements.
Example planning format: ASTM A572/A572M Grade 50 plate, dimensions and tolerances per the applicable general requirements, with the required mill test report and project-specific toughness or inspection provisions.
Final wording must follow the governing design code, contract documents, owner specification and the edition adopted by the project.
How do A572 Grades 42, 50, 55, 60 and 65 compare?
The cleanest comparison is mechanical: the grade number tracks minimum yield strength, while minimum tensile strength rises and required elongation generally falls as grade strength increases. The table below is a selection aid; the current ASTM standard controls all orders.
| Grade | Minimum yield | Minimum tensile | Minimum elongation in 2 in | Minimum elongation in 8 in | Practical interpretation |
|---|---|---|---|---|---|
| Grade 42 [290] | 42 ksi / 290 MPa | 60 ksi / 415 MPa | 24% | 20% | Lower-strength legacy or matching requirement; confirm availability before designing around it. |
| Grade 50 [345] | 50 ksi / 345 MPa | 65 ksi / 450 MPa | 21% | 18% | Strong general-purpose baseline for plates, bars and several structural-shape families. |
| Grade 55 [380] | 55 ksi / 380 MPa | 70 ksi / 485 MPa | 20% | 17% | Intermediate strength level; useful only when the form, quantity and fabricator support it. |
| Grade 60 [415] | 60 ksi / 415 MPa | 75 ksi / 520 MPa | 18% | 16% | Potential weight reduction, with closer attention to product limits, forming and welding. |
| Grade 65 [450] | 65 ksi / 450 MPa | 80 ksi / 550 MPa | 17% | 15% | Highest A572 grade; use when the design benefits from strength and procurement is confirmed. |
Elongation values can be adjusted by product width, specimen type or provisions in ASTM A6/A6M. Do not use this summary in place of the purchased edition of ASTM A572/A572M-25.
A572 grade and specification route selector
Choose the closest project conditions. This tool identifies a sensible starting route and highlights when a different ASTM specification may be more appropriate. It is not a structural design calculation or a substitute for the governing code.
Start with A572 Grade 50 plate
For ordinary plate or bar work where structural strength governs, Grade 50 is a practical first specification to price and validate.
- Confirm: thickness, width, quantity and producer capability.
- Fabrication: qualify the welding or forming route for the actual heat and joint.
- Order: request an MTR and state special testing explicitly.
Where does each A572 grade make sense?
A higher grade is not automatically a better material. The useful grade is the one that meets the governing limit state, fits the intended product form, can be sourced at the required thickness and quantity, and can be fabricated under a qualified procedure.
Grade 42 provides a 42 ksi minimum yield level and may appear in older designs or repair situations. Before selecting it for new work, compare current supply and cost with Grade 50 rather than assuming the lower grade is easier to buy.
Grade 50 is the usual first comparison for structural plate, bars, HP piles, angles and several other products. For W-shapes, however, A992 is normally the cleaner modern specification.
Grade 55 can bridge the gap between 50 and 60 ksi yield strength, but a small theoretical section reduction may be lost if material must be specially rolled or separately qualified.
Grade 60 can reduce required area when yielding controls. Check the standard’s product limits, producer rolling schedule, connection design and forming demands before relying on the weight saving.
Grade 65 is a specialized route for strength-critical components. It deserves early supplier and fabricator involvement because thickness, shape size, weld procedure and bend demands can dominate the decision.
Why is A572 stronger than plain carbon steel?
A572 is an HSLA steel because relatively small additions of microalloying elements work with controlled rolling and cooling to refine the microstructure. Niobium, vanadium and titanium can limit grain growth and form fine precipitates that resist dislocation movement. The result is higher yield strength without relying only on a large carbon increase.
That does not mean every Grade 50 heat has one fixed chemistry. ASTM provides several allowed alloy types, and carbon and manganese limits can vary with grade, product and thickness. The producer may choose the permitted alloy route unless the purchase order invokes a particular requirement.
- Do not estimate weldability from the grade number alone. Review the actual heat analysis and the carbon-equivalent method required by the welding code or WPS.
- Do not treat nominal composition tables as an MTR. The mill test report gives the chemistry of the delivered heat.
- Do not substitute a weathering grade casually. ASTM A588/A588M is not interchangeable with A572 without purchaser and supplier agreement.
A572 vs A36, A992, A588 and A709
Many ordering errors happen because a designer compares yield strengths but overlooks what each specification controls. These materials can overlap in strength, yet they are not interchangeable descriptions.
Strength versus simplicity
A36 is a common carbon structural steel with a 36 ksi minimum yield level for many products. A572 Grade 50 offers a higher minimum yield strength, but the benefit appears only when the governing design check allows a smaller or lighter member.
Use A992 for W-shapes
AISC identifies A992 as the preferred W-shape specification. It resembles A572 Grade 50 but adds a maximum yield strength, a maximum yield-to-tensile ratio and carbon-equivalent controls that improve predictability.
Weathering is a separate requirement
A572 is not automatically atmospheric-corrosion-resistant steel. A588 controls chemistry and properties for weathering performance. Surface detailing and the service environment still determine whether bare weathering steel is appropriate.
Bridge work needs the bridge route
A709/A709M and AASHTO M 270 organize structural-steel requirements for bridges, including grade designations and optional toughness provisions. Use the owner’s bridge specification rather than assuming base A572 is sufficient.
When does a higher A572 grade actually reduce weight?
If a tension member, compact beam section or other component is controlled by yielding, increasing the specified minimum yield strength can reduce the required cross-sectional area. Moving from 50 to 65 ksi is a 30% increase in nominal yield strength, but it does not guarantee a 30% weight reduction. Local buckling, lateral-torsional buckling, connection geometry, fatigue, minimum thickness and serviceability may prevent the section from shrinking in proportion.
Elastic modulus is approximately the same across ordinary structural-steel grades. Consequently, replacing Grade 50 with Grade 65 while keeping the same geometry does not materially change elastic deflection. A slender compression member can also remain governed by elastic buckling rather than yield strength.
A credible economic comparison therefore includes the redesigned member size, connection changes, procurement premium, minimum order quantity, lead time, welding procedure, forming effort, inspection and erection—not merely dollars per ton.
Use this decision sequence
1. Identify the governing limit state. Is it yielding, buckling, deflection, fatigue, fracture, vibration or a detailing minimum?
2. Redesign the member. Compare realistic available sections or plate thicknesses rather than dividing the old weight by the strength ratio.
3. Price the full fabrication route. Request actual quotes and lead times for each grade and form.
4. Verify the code route. Confirm that the selected grade and product are permitted for the structural system and service.
How should A572 welding, forming and machining be planned?
A572 is routinely fabricated, but no universal electrode, preheat temperature or minimum bend radius is correct for every grade, thickness and joint. The safe route begins with the actual material certificate, applicable welding code and a qualified or prequalified WPS.
Confirm material identity
Verify grade, heat number, dimensions and test report before cutting. Keep traceability through fabrication when the contract documents require it.
Calculate the welding route
Use the applicable code and WPS to evaluate base-metal group, thickness, joint restraint, diffusible hydrogen, heat input and preheat/interpass limits.
Qualify forming operations
Base the bend radius and direction on grade, thickness, surface condition and producer guidance. Higher strength usually reduces forming margin.
Control cut edges
Inspect flame-, plasma- or laser-cut edges when fatigue, bending or critical stress concentration makes edge condition important.
Verify the finished joint
Apply the specified visual and nondestructive examination. Confirm that repair welding follows an approved procedure and preserves traceability.
Which A572 grades and products are actually available?
The ASTM scope defines what may be furnished, but a standard does not guarantee that every grade, thickness and shape is stocked. Availability is a producer-and-market question that should be checked before a design depends on a specialized combination.
Current producer offerings show broad Grade 50 plate capability. Higher grades and unusual widths or thicknesses can require mill confirmation, minimum quantities or a different specification.
AISC recommends A992 for W-shapes. A heat may be multi-certified, but the purchase order should use the specification that expresses the required controls most clearly.
AISC’s Code of Standard Practice identifies A572 Grade 50 as a shop-standard grade for HP, M, S, MT, ST and angle products, subject to producer availability.
Nucor and Gerdau list A572 Grades 60 and 65 for selected beam products, often with size limitations. “Available in the specification” and “available for this section now” are different statements.
ASTM A572/A572M-25 adds requirements for structural products produced from coil and furnished without heat treatment or with stress relieving only. Verify testing and reporting for the finished product.
Where is A572 structural steel used?
A572 grades serve buildings, bridges, piling, transmission structures, industrial frames, equipment supports, material-handling systems and fabricated machinery. Grade 50 is a natural comparison point for many applications, while Grades 60 and 65 become relevant where strength-led weight reduction has enough value to offset tighter sourcing and fabrication constraints.
- Buildings: plates, bars, columns, braces, connection components and non-W structural shapes—while modern W-shapes are typically specified to A992.
- Bridges: use the owner’s A709/AASHTO M 270 material route, toughness zone, fatigue category and welding requirements.
- Transmission structures: higher-strength grades may reduce weight, but forming, galvanizing, fatigue and connection details must remain workable.
- Heavy equipment: verify whether A572 or a dedicated high-strength plate specification better matches forming, thickness and performance requirements.
- Exposed structures: A572 requires a corrosion-protection system unless a qualified weathering-steel specification and suitable environment are selected.
Five common A572 specification mistakes
Ordering “A572” without a grade
The grade establishes the minimum yield level. An incomplete designation invites RFIs, substitutions and inconsistent pricing.
Upgrading strength when stiffness controls
Higher yield strength does not increase elastic modulus. Recheck deflection, vibration and buckling before paying for a stronger grade.
Using A572-50 instead of A992 for W-shapes
A992 communicates the tighter modern W-shape controls that AISC recommends. Multi-certification does not make the wording irrelevant.
Assuming notch toughness is automatic
State the CVN energy, test temperature, specimen orientation, sampling location and frequency required by the project.
Waiting until award to check availability
Special grades, thicknesses and sections can change minimum order quantities and lead time. Confirm supply during design development.
Treating A588 as a drop-in substitute
A588 provides a different chemistry route for atmospheric corrosion resistance. ASTM explicitly requires purchaser and supplier agreement before substitution.
What should an A572 RFQ include?
A good RFQ gives the mill, service center and fabricator enough information to judge compliance, availability and fabrication risk before the material is ordered.
- Specification editionASTM A572/A572M-25 or the edition adopted by the contract.
- Grade42, 50, 55, 60 or 65—never “A572” alone.
- Product formPlate, bar, shape or sheet piling with exact dimensions and quantity.
- Delivery requirementsApplicable ASTM A6/A6M provisions, tolerances and processing condition.
- ToughnessCVN energy, temperature, orientation, location and testing frequency if required.
- InspectionUltrasonic, surface or other supplementary examination where the design demands it.
- Fabrication informationWelding code, forming direction, bend severity, galvanizing or coating route.
- DocumentationMTR, heat traceability, certification and any domestic-origin requirements.
Preparing A572 steel for welding, coating or marking
Material selection and surface preparation solve different problems. The correct A572 grade provides the specified structural properties; cleaning, welding and marking processes then need to preserve traceability and deliver the required joint or surface condition.
Need to clean, weld or mark A572 components?
Share the grade, thickness, joint or contamination, production volume and required result. Oceanplayer can recommend a laser process direction and identify what must be validated on your actual material.
Include these details
- A572 grade and mill certificate, if available
- Product form, thickness and part dimensions
- Joint type or surface contamination
- Required penetration, cleanliness or mark
- Target cycle time and annual volume
- Photos or representative sample parts
A572 steel FAQ
Short answers to the questions that most often change material orders and fabrication plans.
Is A572 the same as Grade 50?
No. ASTM A572/A572M contains five strength grades: 42, 50, 55, 60 and 65. “Grade 50” is one option inside the specification, so an order that says only “A572” is incomplete.
What is the difference between A572 Grade 50 and A36?
The most visible difference is minimum yield strength: 50 ksi for A572 Grade 50 versus 36 ksi for many A36 products. A572 is an HSLA specification that requires microalloying. The higher strength can reduce member size when yielding controls, but it does not increase elastic modulus or automatically reduce deflection.
Is A572 Grade 50 the same as A992?
No. They can be multi-certified and share 50 ksi minimum yield and 65 ksi minimum tensile levels, but A992 adds controls including a maximum yield strength, maximum yield-to-tensile ratio and carbon-equivalent limit. AISC recommends A992 for modern W-shapes.
Which A572 grade is most common?
Grade 50 is the most practical starting inquiry for many structural products, but actual availability depends on product form, section, thickness, quantity, producer and region. For W-shapes, A992 is normally the preferred specification instead.
Does A572 steel resist rust?
A572 is not inherently a weathering-steel specification. In exposed service it normally needs a suitable coating or corrosion allowance. If atmospheric corrosion resistance is required, evaluate a weathering specification such as A588 or a bridge grade such as A709 Grade 50W, together with environmental and detailing requirements.
Can all A572 grades be welded?
The ASTM scope permits welding for the applications stated in the standard, but welding must use a procedure suitable for the grade, thickness, joint, service and applicable code. Review the actual heat chemistry and use a qualified or prequalified WPS rather than a universal preheat or filler recommendation.
Does A572 include Charpy V-notch toughness?
Not as one universal base value. When notch toughness matters, the purchaser must state the required testing. The order should define energy, temperature, specimen orientation, location and frequency through the governing specification or supplementary requirement.
Can Grade 65 replace Grade 50 without redesign?
Not automatically. A stronger grade changes expected material behavior, connection demands, availability and fabrication requirements. If the original design is governed by deflection, buckling, fatigue or minimum thickness, Grade 65 may provide little or no benefit.
What should I verify on an A572 mill test report?
Check the specification and grade, heat number, product dimensions, yield strength, tensile strength, elongation and heat analysis. Also confirm any ordered CVN, ultrasonic, traceability or domestic-origin requirements.
Sources used for this guide
- ASTM A572/A572M-25 — current scope, grades, intended construction methods and toughness ordering principle.
- AISC Engineering FAQ 1.3: Ordering Steel — preferred material specifications, A992 comparison and availability guidance.
- ANSI/AISC 303-22 Code of Standard Practice — shop-standard material grades and material-identification provisions.
- ANSI/AISC 341-22 Seismic Provisions — permitted A572 grades for seismic force-resisting systems.
- SSAB ASTM A572 Grade 50 — current Grade 50 plate dimensions, mechanical properties and toughness-ordering note.
- Nucor Plate Products and Gerdau Standard I-Beam — examples of producer-specific grade and product availability.
This page is an educational selection guide, not a structural design, welding procedure, material certification or substitute for purchased standards and project specifications. Requirements can differ by code edition, jurisdiction, owner, product, thickness and service.