ASTM A514 Grade M|A514 Gr.M STEEL PLATE

ASTM A514 Grade M is a historical quenched-and-tempered alloy steel plate designation for high-strength structural fabrication. It appears in Table 1 of ASTM A514/A514M-00a but is not listed in Table 1 of the 2005 edition or the current ASTM A514/A514M-22. For a project inquiry to Gangsteel, state the drawing or contract edition, thickness, delivery condition and inspection requirements together. Under its legacy edition, Grade M provides a minimum specified yield strength of 100 ksi [690 MPa] within its permitted thickness range; it is not a general-purpose boiler or pressure-vessel plate.

Material selection and typical applications

Typical A514 applications include crane booms, transport trailers, construction equipment, heavy vehicle frames and welded bridge members. Grade M uses a nickel-molybdenum-boron alloy concept. Its strength can support weight-efficient designs, but section size still depends on buckling, stiffness, fatigue and connection design—not yield strength alone.

Within the ASTM A514 steel plate range, Grade M had a maximum specified thickness of 2 in. [50 mm] in the 00a edition. Because the grade is no longer listed in the current standard, confirm early whether a mill can melt and certify it to the edition named on the drawing. Where the design allows, the engineer may re-specify a current grade; that is a design decision, not an automatic substitution.

Chemical composition

The following heat-analysis limits are for Grade M in ASTM A514/A514M-00a, in weight percent. They are specification limits, not the measured composition of a particular heat.

Elements not listed had no Table 1 requirement for Grade M. Note that the 00a edition used 0.035% maximum phosphorus and sulfur limits for most grades, whereas current A514 grades are limited to 0.030%. A mill offer for this legacy grade should state which edition and limits it certifies; product analysis, where ordered, is subject to ASTM A6/A6M tolerances.

Mechanical properties and test conditions

The strength values below apply to heat-treated Grade M plate up to its grade-specific maximum thickness of 2 in. [50 mm]. ASTM A514/A514M-00a Table 2 and its specimen notes govern acceptance.

Yield is determined by 0.2% offset or 0.5% extension under load as permitted by ASTM A370. The rectangular specimen is 1½ in. [40 mm] wide; its elongation gauge length must include the fracture as specified. Elongation and reduction of area need not be determined for floor plates, and other applicable adjustments remain subject to the ordered standard.

The inch-pound and SI systems are separate standard systems; do not mix rounded limits between them. Charpy V-notch impact performance is not established by tensile strength alone. Specify the required temperature, energy, orientation and acceptance criteria when impact testing is needed.

Delivery condition and heat treatment

Specify quenched-and-tempered delivery for plate intended to meet the finished material requirements. Normalizing alone is not the standard Grade M heat-treatment route.

These are the minimum temperatures in the 00a edition, not a shop heat-treatment recipe. Holding time, cooling practice and furnace control require an appropriate mill procedure. That edition also required plates wider than 24 in. [600 mm] to be tension tested in the transverse direction, with the adjusted elongation and reduction-of-area minimums. Any later thermal cycle requires engineering review.

Welding and fabrication precautions

Use a qualified welding procedure appropriate to the grade, joint and governing fabrication code. Control hydrogen through suitable consumables, correct storage and dry, clean joint surfaces. Determine preheat, interpass limits and heat input from actual thickness, restraint, chemistry and mill recommendations.

For background, review the factors discussed in A514 preheat considerations, but do not apply a family-wide temperature table as a Grade M welding procedure. Grade-specific recommendations and the qualified procedure take priority.

Excessive thermal exposure can alter the Q&T microstructure. Stress relief or post-weld heat treatment needs particular care because reheat cracking can occur in the weld heat-affected zone.

Before cold forming, remove burrs and sharp edge defects; assess thermal-cut edges near the bend axis. Select bend radius and tooling for thickness and rolling direction, rather than assuming ordinary mild-steel practice.

Related grades and specifications

The current grades listed above are navigation for engineering review, not certified replacements for Grade M. Grade letters identify different chemical requirements, not a simple ranking from lower to higher quality. Likewise, A514 is not interchangeable with A517 or an ASME pressure-vessel designation. Any re-specification requires a complete review of chemistry, thickness, heat treatment, toughness, testing and design-code acceptance.

Equivalent and comparable materials

The following are verified EN high-strength structural plate comparators, not certified equivalents to ASTM A514 Grade M. Similar strength class and Q&T delivery do not establish interchangeability.

Impact-test temperature alone is not a toughness specification: compare energy, specimen size, orientation and sampling requirements. Producer guarantees may exceed the relevant EN minimums and vary with thickness. Do not transfer a comparator's permitted thickness range to A514 Grade M.

Any substitution requires the designer's approval and acceptance under the governing design and fabrication codes. Review chemistry, thickness-dependent strength, elongation test basis, impact requirements, welding procedures, inspection and certification together.

If the order requires A514 Grade M, an EN-only certificate is insufficient; compliance must be explicitly demonstrated and certified to the ordered ASTM requirements.

Information to include in a purchase inquiry

Stock, processing capability and certification arrangements must be confirmed for the actual order rather than assumed from a product description.

Frequently asked questions

1. Is A514 Grade M still in the current ASTM A514 standard?

No. Grade M is listed in A514/A514M-00a with a maximum thickness of 2 in. [50 mm], but it is not in Table 1 of the 2005 or 2022 editions. Orders must name the legacy edition and confirm that the mill can certify to it.

2. Is A514 Grade M normalized or quenched and tempered?

The normal finished-material route is quenching and tempering. Normalized-only plate must not be accepted as equivalent finished Grade M merely because it has similar chemistry.

3. Why do data sheets show either 18% or 16% elongation?

The standard's base minimum is 18%, with a two-percentage-point reduction for transverse tests. Specimen geometry and other ASTM A6/A6M adjustments also matter. Compare the test direction and gauge length before judging a certificate.

4. Which current grade can replace A514 Grade M?

None automatically. Current grades with a similar thickness limit, such as Grade H, can be reviewed by the designer, but chemistry, toughness, welding procedures and code acceptance must be re-checked before any re-specification.

5. Can A514 Grade M be welded and then stress relieved?

Welding is possible with an appropriate qualified procedure. Stress relief is not an automatic follow-on step: its thermal cycle can affect properties and create reheat-cracking risks, requiring welding-engineering and mill review.

6. Are impact testing and ultrasonic inspection included automatically?

Do not assume so. State the required tests, methods, acceptance criteria and reporting requirements in the inquiry and purchase order, and check that the agreed inspection documents demonstrate compliance.