ASTM A572 Grade 42
High-strength low-alloy (HSLA), microalloyed structural steel · ASTM A572/A572M-25 — High-Strength Low-Alloy Columbium-Vanadium Structural Steel · ASTM A6/A6M — General requirements for rolled structural steel bars, plates, shapes, and sheet piling
ASTM A572 Grade 42 is a weldable, killed HSLA structural steel with a minimum yield point of 42 ksi [290 MPa] and minimum tensile strength of 60 ksi [415 MPa]. Its strength is developed using specified niobium, vanadium, or titanium-nitrogen microalloying routes. The specification covers plates, shapes, bars and sheet piling, but does not by itself guarantee Charpy toughness, weathering resistance, a maximum yield strength, or a maximum carbon equivalent. Product form, dimensions, supplementary requirements and certification therefore remain important parts of a complete purchase specification.
- 42 ksi [290 MPa]Minimum yield point · The number 42 is the specified minimum yield point in inch-pound units.
- 60 ksi [415 MPa]Minimum tensile strength · ASTM A572/A572M specifies no general maximum tensile strength for Grade 42.
- 6 in. [150 mm]Maximum plate or bar thickness · The Grade 42 size limit; structural shapes, sheet piling, zees and rolled tees are listed for all sizes covered by ASTM A6/A6M.
- Killed, microalloyed steelMetallurgical basis · The producer selects an allowed Nb, V, Nb-V, or Ti-N-V alloy route unless a permitted type is specifically ordered.
- Not included as a base Grade 42 requirementNotch toughness · Required CVN energy, test temperature, orientation and frequency must be specified where fracture resistance matters.
- Not a defining propertyAtmospheric corrosion resistance · A572 Grade 42 is not a weathering-steel designation; coating or another corrosion-control system may be necessary.
Overview
- Designation system
- ASTM product specification with strength-based grade designation
- Product forms
- Structural shapes, Plate, Structural bars, Sheet piling, Zees, Rolled tees
- Condition
- Hot-rolled structural product, Killed steel, No single mandatory heat-treatment condition is defined by the grade designation
- Density
- 7850 kg/m³ (Representative density used for structural-steel calculations; not a grade-specific acceptance requirement.)
What the designation covers
ASTM A572/A572M is a structural-product specification, not merely a chemistry designation. Grade 42 applies to rolled structural shapes, plates, sheet piling and bars intended for riveted, bolted or welded construction. The SI form is Grade 290, reflecting the 290 MPa minimum yield point. The inch-pound and SI requirement systems are independently standardized and should not be mixed when determining conformity.
ASTM A6/A6M supplies the accompanying general rules for ordering, dimensions and tolerances, sampling, tension testing, product analysis, workmanship, marking and certification. Where A572/A572M conflicts with A6/A6M, the A572/A572M product specification governs.
| Product form | Maximum size under Grade 42 | Practical interpretation |
|---|---|---|
| Plate and structural bar | 6 in. [150 mm] thickness, diameter or distance between parallel faces | Products beyond this limit cannot be certified as A572 Grade 42 under the normal scope. |
| Structural shapes | All flange or leg thicknesses covered by ASTM A6/A6M | Availability in a particular shape and size is a separate commercial issue. |
| Sheet piling | All sizes covered by ASTM A6/A6M | Do not confuse rolled sheet piling with HSS or generic cold-formed tubing. |
| Zees and rolled tees | All sizes covered by ASTM A6/A6M | The specification applies to rolled structural products, not automatically to fabricated sections. |
Coil is not itself qualified to A572/A572M. A structural product made from coil becomes eligible only after processing into finished lengths, with the additional testing and reporting required by ASTM A6/A6M.
Specified mechanical properties
| Property | Requirement | Test or applicability note |
|---|---|---|
| Yield point, minimum | 42 ksi [290 MPa] | Specified minimum; the base specification does not impose a general maximum yield strength. |
| Tensile strength, minimum | 60 ksi [415 MPa] | Specified as a minimum, not a 60 ksi nominal value or a bounded range. |
| Elongation in 8 in. [200 mm], minimum | 20% | Subject to specimen and product provisions in ASTM A6/A6M. |
| Elongation in 2 in. [50 mm], minimum | 24% | For wide-flange shapes over 426 lb/ft [634 kg/m], a 19% minimum applies. |
| Wide plate adjustment | Reduce the stated elongation minimum by 2 percentage points | Applies to plates wider than 24 in. [600 mm]. |
| Floor plate | Elongation determination not required | Applies where furnished as floor plate under the relevant provisions. |
Test-piece orientation, location, dimensions and permitted adjustments are controlled by ASTM A6/A6M. Reported mill values should not be compared with the table without confirming those conditions.
Grade 42 does not establish impact toughness, fracture toughness, fatigue performance, through-thickness ductility, hardness, maximum yield-to-tensile ratio or elevated-temperature properties. These characteristics require the appropriate project specification, supplementary testing or a different material specification.
Chemistry and microalloying
The steel must be killed and must use one of the allowed microalloy systems. These additions support grain refinement and precipitation strengthening, allowing a higher yield level than ordinary carbon structural steel without defining one fixed alloy recipe. The applicable alloy elements and their heat-analysis results must be reported on the material test report.
| Element or relationship | Requirement | Important qualification |
|---|---|---|
| Carbon | 0.21% maximum | Applies throughout the Grade 42 size range. |
| Manganese | 1.35% maximum | For each 0.01 percentage-point reduction below the carbon maximum, Mn may increase by 0.06 percentage point, to 1.60% maximum. |
| Manganese minimum | 0.80% for plate over 3/8 in. [10 mm]; 0.50% for thinner plate and other products | Corresponding product-analysis minima are 0.75% and 0.45%. |
| Manganese-to-carbon ratio | 2:1 minimum | A separate chemistry relationship in addition to the individual limits. |
| Phosphorus | 0.030% maximum generally | Up to 0.040% is permitted for structural shapes, sheet piling, bars and plates no wider than 15 in. [380 mm]. |
| Sulfur | 0.030% maximum generally | Up to 0.050% is permitted for structural shapes, sheet piling, bars and plates no wider than 15 in. [380 mm]. |
| Silicon | 0.40% maximum for plate through 1-1/2 in. [40 mm], shapes through 3 in. [75 mm], sheet piling, bars, zees and rolled tees | For thicker plate and shapes with flange thickness over 3 in. [75 mm], the required range is 0.15–0.40%. |
| Copper, when specified | 0.20% minimum by heat analysis | The corresponding product-analysis minimum is 0.18%; copper is not automatically required. |
The relaxed phosphorus and sulfur limits for specified product forms are part of the ASTM rules and should be considered when a purchaser applies tighter project chemistry limits.
| Type | Required alloy system | Specified content |
|---|---|---|
| 1 | Niobium/columbium | Nb 0.005–0.050% |
| 2 | Vanadium | V 0.01–0.15% |
| 3 | Niobium/columbium plus vanadium | Nb 0.005–0.050%; V 0.01–0.15%; Nb + V 0.02–0.15% |
| 5 | Titanium, nitrogen and vanadium | Ti 0.006–0.040%; N 0.003–0.015%; V 0.06% maximum |
The producer may select the permitted type unless otherwise specified by the purchaser. Specifying an alloy type without a demonstrated engineering need can unnecessarily restrict supply.
Toughness, corrosion and other limits of the grade
Notch toughness is not inherent in the basic Grade 42 designation. For welded bridges, dynamically loaded structures, low-temperature service, fracture-critical details or thick restrained joints, the purchaser must establish the necessary Charpy V-notch requirements. A complete toughness requirement normally identifies absorbed energy, test temperature, specimen orientation, test frequency, product thickness and the applicable acceptance rules. A mill's typical CVN data is not a substitute for an ordered requirement.
A572 Grade 42 also carries no enhanced atmospheric-corrosion requirement. ASTM A588/A588M weathering steel cannot be substituted for A572/A572M without purchaser-supplier agreement, even where its strength appears suitable. Corrosion protection should be selected from the actual environment, detailing, coating system and maintenance plan rather than inferred from the HSLA description.
The specification does not set a maximum carbon equivalent. Weldability decisions that depend on carbon equivalent must use the actual reported heat chemistry and the applicable welding code or project requirement.
Fabrication implications
Grade 42 is intended for welded as well as bolted or riveted structures, but this is not a blanket approval of every welding procedure. Filler-metal selection, hydrogen control, preheat and interpass temperature, heat input, joint restraint and inspection should follow the governing welding code and qualified procedure. Material thickness, actual MTR chemistry, ambient conditions and detail severity can matter more than the grade's 42 ksi label.
Cold bending and forming should account for thickness, bend direction relative to rolling, edge quality and the applicable recommendations in ASTM A6/A6M. The Grade 42 designation does not specify a universal minimum bend radius. Severe cold work, hot forming, flame straightening or post-fabrication heat treatment should be controlled by an approved procedure because temperature and deformation can alter the microalloy-strengthened structure and local mechanical properties.
Conventional cutting, drilling and machining practices for structural steel are generally applicable. Fabricators should nevertheless manage thermally cut edges, notches, weld access holes and repaired discontinuities in accordance with the governing fabrication standard, particularly where fatigue or brittle-fracture risk is significant.
Ordering and inspection priorities
| Item | Why it matters |
|---|---|
| Specification and edition | State ASTM A572/A572M, Grade 42, and the contractually applicable revision. Do not rely on an undated shorthand where project documents control editions. |
| Unit system | Choose A572 or A572M requirements consistently; ASTM treats the two systems independently. |
| Product form and dimensions | The form controls dimensional tolerances, sampling, chemistry qualifications and availability. |
| Quantity, length and edge requirements | Needed to apply ASTM A6/A6M delivery and tolerance provisions. |
| Required toughness | Specify CVN energy, temperature, orientation, location and frequency when needed. |
| Copper or microalloy type | Order only where intentionally required; neither a copper minimum nor a purchaser-selected microalloy route is automatic. |
| Coil-derived product status | Require the additional A6/A6M testing and reporting when finished structural products originate from coil. |
| Certification and traceability | Require an MTR identifying heat, grade, chemistry, alloy type and tensile results, together with marking or traceability needed by the project. |
| Additional project restrictions | Examples may include tighter chemistry, weldability controls, ultrasonic examination, special surface quality or through-thickness properties; these require explicit agreement. |
| Check | Acceptance question |
|---|---|
| Identification | Does the report clearly state A572/A572M Grade 42 or Grade 290, product form, heat and applicable edition? |
| Dimensions | Is the ordered thickness or section within the Grade 42 product-size scope? |
| Chemistry | Do C, Mn, P, S and Si comply with the rules applicable to that product form and dimension? |
| Microalloy system | Is an allowed Type 1, 2, 3 or 5 chemistry reported? |
| Tensile results | Are yield, tensile and elongation results compliant under the correct specimen basis and adjustments? |
| Supplementary tests | Are ordered toughness, examination or special chemistry results present and traceable? |
| Multiple certification | If other grades are listed, does the material independently satisfy every requirement of A572 Grade 42 rather than merely exceeding its yield strength? |
A higher measured yield strength alone does not establish conformity to Grade 42; the applicable chemistry, product, test, certification and dimensional requirements must also be met.
Availability and substitution
Grade 42 remains a valid ASTM grade, but it should not be assumed to be routinely stocked in every plate thickness or rolled shape. Modern U.S. wide-flange production commonly favors ASTM A992, while A572 Grade 50 is more prevalent in several structural product markets. Availability and rolling schedules should be confirmed before Grade 42 is locked into procurement documents.
| Designation | Important distinction from A572 Grade 42 |
|---|---|
| ASTM A36/A36M | Lower 36 ksi [250 MPa] minimum yield grade with different chemistry and tensile requirements; not interchangeable merely because a particular heat tests above 42 ksi. |
| ASTM A572/A572M Grade 50 | Same specification family but a 50 ksi [345 MPa] minimum yield and 65 ksi [450 MPa] minimum tensile grade, with different chemistry limits and availability. |
| ASTM A992/A992M | Primarily used for building-framing shapes and includes controls such as maximum yield strength, yield-to-tensile ratio and carbon equivalent that are not part of A572 Grade 42. |
| ASTM A588/A588M | HSLA structural steel with atmospheric-corrosion requirements; substitution for A572 requires agreement. |
| ASTM A709/A709M or AASHTO M 270 | Bridge-material specifications that can impose bridge-specific grade, toughness and quality requirements; an A572 certificate alone does not demonstrate compliance. |
| EN 10025 structural grades | Strength similarities do not establish equivalence because chemistry, thickness dependence, impact classes, delivery conditions and certification differ. |
Substitution should be evaluated against the complete governing material and product specifications, not only nominal yield strength.
Sources
- ASTM A572/A572M-25 — Standard Specification for High-Strength Low-Alloy Columbium-Vanadium Structural SteelASTM International
- ASTM A6/A6M — Standard Specification for General Requirements for Rolled Structural Steel Bars, Plates, Shapes, and Sheet PilingASTM International
- Mill Production and Tolerances — Structural Steel Material Specifications FAQAmerican Institute of Steel Construction
- Steel AvailabilityAmerican Institute of Steel Construction
- Bridge Welding Reference ManualFederal Highway Administration
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