ASTM A514 Grade Q

Overview

Designation system

ASTM grade within ASTM A514/A514M

Product forms

Structural-quality steel plate, Floor plate, subject to the applicable ASTM A6/A6M provisions and mechanical-test exceptions

Condition

Quenched and tempered, By special order, supplied stress relieved without final quenching and tempering for subsequent purchaser heat treatment

Density

7850 kg/m³ (Representative engineering value for alloy steel; density is not a grade requirement in ASTM A514/A514M.)

What the designation means

A514/A514M is a plate specification based on high strength obtained by quenching and tempering. The letter Q does not denote a separate strength class or quality level; it identifies one of the permitted alloy chemistries. The tensile requirements are common to the A514 specification, while the chemistry and maximum available thickness differ among letter grades. Grade Q uses substantial nickel, chromium and molybdenum additions, together with vanadium, to provide the hardenability needed for plate through 6 in. [150 mm].

The specification applies to structural-quality plate intended primarily for welded and non-welded structures. It does not define bar, structural shape, tube, pipe, forging or casting products, and it is not a pressure-vessel plate specification. General requirements for dimensions, tolerances, testing, marking, certification and supplementary options are supplied by ASTM A6/A6M unless A514/A514M states otherwise.

ASTM treats inch-pound and SI values as separate standard systems. An order should use one system consistently rather than converting and combining limits from both systems.

Grade Q chemistry and metallurgical basis

The steel must be killed and meet the fine-austenitic-grain-size provisions of ASTM A6/A6M. Nickel supports toughness and through-thickness response; chromium and molybdenum increase hardenability and tempering resistance; vanadium contributes precipitation strengthening and grain-control effects. The resulting strength is therefore inseparable from the specified quench-and-temper cycle.

A514/A514M does not impose a maximum carbon-equivalent value for Grade Q. Weld-procedure decisions should therefore use the actual certified heat analysis, not only the broad specification limits. Combining every maximum alloy limit into a theoretical carbon equivalent is excessively conservative and does not represent a normal production heat.

Heat treatment and preservation of properties

The delivered microstructure is normally tempered martensitic or martensitic-bainitic, with the exact balance depending on section size and mill processing. Thick plate has a less severe effective quench at its center than thin plate, which is why the minimum yield and tensile strengths decrease above 2.5 in. [65 mm].

Any fabrication operation involving substantial reheating can change the qualified condition. Hot forming, high-temperature flame straightening, prolonged stress relief or postweld heat treatment should not be assumed acceptable merely because the steel was originally tempered at 1150 °F [620 °C] or above. The actual temperature-time cycle and required final properties must be evaluated. A514/A514M permits purchase-order testing of specimens subjected to additional thermal cycles intended to simulate later fabrication treatment.

Mechanical requirements and test interpretation

Except for the thin-plate alternative described below, one tension test is taken from a corner of each plate as heat treated. Specimens should be removed from the plate in its heat-treated condition where possible. Separately heat-treated test pieces must be full thickness, sufficiently large to avoid edge effects, and treated similarly and simultaneously with the plate.

For plate 3/8 in. [10 mm] and under, the producer may use Brinell hardness testing on each plate instead of tension testing every plate. Two plates per lot are then tension tested; the lot is limited to material from the same heat, thickness, prior condition and scheduled heat treatment and to 15 tons [15 Mg]. The 235–293 HBW range should not be interpreted as an abrasion-resistant-steel hardness class or as a general hardness guarantee for every thicker plate.

The stated properties are specification acceptance requirements at the prescribed test conditions. They do not establish fatigue strength, fracture toughness, through-thickness properties, elevated-temperature strength, corrosion allowance or design stress.

Toughness and service qualification

Although Grade Q is generally selected where strength and useful toughness are required in heavy plate, the base A514/A514M order does not include a mandatory Charpy V-notch energy or test temperature. Descriptions such as “tough” or “suitable for cold service” are therefore not procurement requirements. For low-temperature service, dynamically loaded structures, fracture-critical components or thick welded details, the purchaser must define the required Charpy testing through the applicable ASTM A6/A6M supplementary requirement or the governing construction specification.

Grade Q is not inherently a weathering steel, stainless steel or abrasion-resistant plate. Corrosion protection and wear life must be addressed separately for the intended environment.

Welding, cutting and forming

A514 Grade Q is intended to be weldable, but this means that a suitable procedure must be selected and qualified for the joint and service—not that ordinary mild-steel practice is adequate. The relatively high hardenability raises the risk of hydrogen-assisted cracking in the heat-affected zone, while excessive heat input or interpass temperature can overtemper and soften material adjacent to the weld. Procedure control should address actual heat chemistry, plate thickness, restraint, joint configuration, consumable strength and hydrogen classification, preheat, interpass temperature, heat input, ambient conditions and applicable construction code.

Do not qualify a welding procedure using only the designation “A514.” The A514 letter grades have different chemistries and maximum thicknesses. The WPS supporting data and material certificates should adequately represent Grade Q and the production thickness range.

Specifying and accepting Grade Q plate

Maximum specification thickness is not the same as commercial availability. Before completing a design around very heavy Grade Q plate, confirm available thickness, width, length, flatness capability, testing options, minimum order quantity and delivery schedule with a qualified producer.

Substitution boundaries

A substitution based only on nominal 690 MPa or 100 ksi yield strength is inadequate. Approval should compare the governing product standard, maximum thickness, actual chemistry and carbon equivalent, quench-and-temper requirements, tensile range, toughness, test orientation and location, dimensional tolerances, ultrasonic quality, welding qualification and project-code acceptance. These issues are especially important when replacing Grade Q with another A514 letter grade or with an EN, CSA or proprietary 690 MPa plate.

“T-1” is widely used informally for high-strength quenched-and-tempered plate, but it originated as a proprietary trade designation and is not a reliable synonym for certified ASTM A514 Grade Q. Require the complete specification and grade on purchase documents and material certificates.

Related designations

A related designation or cross-standard counterpart is not a declaration of equivalence; confirm the standard, product form and condition before substituting.