ASTM A514 Grade Q is a quenched and tempered alloy steel plate of very high yield strength, produced to ASTM A514/A514M and used where structural members must carry heavy loads with limited section size. Its combination of high strength, good toughness and weldability in thick sections makes it a common choice for mining and earth-moving equipment, offshore structures and heavy machinery.
This guide explains how Grade Q is defined, how its mechanical properties change with thickness, which international grades are quoted as equivalents, and what has to be checked before an equivalent plate is substituted.
Where ASTM A514 Grade Q Fits
ASTM A514/A514M covers high-yield-strength, quenched and tempered alloy steel plates for welded structures. Grade Q is one of the highest strength grades in that family, with a specified minimum yield strength of 100 ksi (690 MPa) in thinner sections. The plate is delivered in the quenched and tempered condition, which combines a fine tempered martensitic or bainitic structure with adequate toughness and makes the material suitable for welded fabrication when the correct procedure is used.
Specification: ASTM A514/A514M, quenched and tempered alloy steel plate
Grade: A514 Grade Q
Maximum plate thickness: 150 mm [6 in.] under A514M
Typical hardness range: 235-293 HBW
Typical applications: mining and earth-moving equipment, offshore platforms, heavy machinery, structural members in bridges and cranes
Mechanical Properties by Thickness
Yield strength falls as plate thickness increases, because the quench rate at the centre of a thick section is slower. Two thickness bands are therefore quoted for Grade Q.
| Property | Up to 65 mm [2-1/2 in.] | |
|---|---|---|
| Minimum yield strength, MPa [ksi] | 690 [100] | 620 [90] |
| Tensile strength, MPa [ksi] | 760-895 [110-130] | 690-895 [100-130] |
| Minimum elongation, % | 18 | 16 |
| Brinell hardness, HBW | 235-293 | 235-293 |
Because the strength level is achieved by heat treatment rather than by mechanical working, mechanical test results are taken from the heat treated plate. Impact testing is part of the normal qualification route for these grades, and test temperature and minimum energy must be stated on the order.
Chemical Composition of A514 Grade Q
| Element | Content, % |
|---|---|
| C | 0.14-0.21 |
| Mn | 0.95-1.30 |
| P (max) | 0.035 |
| S (max) | 0.035 |
| Si | 0.15-0.35 |
| Ni | 1.20-1.50 |
| Cr | 1.00-1.50 |
| Mo | 0.40-0.60 |
| V | 0.03-0.08 |
| B | 0.001-0.005 |
The low carbon content, combined with nickel, chromium, molybdenum, vanadium and a small boron addition, is what allows the plate to reach 690 MPa yield strength while remaining weldable. Carbon is deliberately kept low to limit hardening in the heat affected zone, and the micro-alloying elements restore strength through hardenability and tempering resistance.
International Equivalent Grades
| Standard | Equivalent grade | Notes |
|---|---|---|
| EN 10025-6 | S690Q | European quenched and tempered structural plate with a minimum yield strength of 690 MPa and comparable toughness. |
| GB/T 16270 | Q690E | Chinese quenched and tempered high strength structural plate with impact testing at low temperature. |
| JIS G3128 | SHY685N | Japanese high yield strength plate for welded structures, with comparable strength and weldability. |
| DIN 17102 | StE690V | Historical German designation for a 690 MPa class weldable fine grain structural steel. |
| ASTM A517 | Grade Q | Related ASTM quenched and tempered plate grade at a similar strength level, written for pressure vessel rather than structural use. |
Equivalents are selected on the basis of comparable chemical composition and mechanical properties, but small differences always remain. Limits for carbon equivalent, sulphur and phosphorus, impact test temperature, maximum thickness and permitted delivery condition can differ between S690Q, Q690E and SHY685N, so a substitution should only be made after the property tables of both standards have been compared against the design requirement.
Welding and Fabrication Notes
Welding must follow a qualified procedure written for high strength quenched and tempered plate, with controlled heat input and interpass temperature.
Low hydrogen consumables are normally required; strength matching of the weld metal should be confirmed against the design rule being applied.
Preheat and interpass temperatures are set by thickness and carbon equivalent, and excessive heat input must be avoided to protect the toughness of the heat affected zone.
Cutting and forming are best done with the plate at ambient temperature; flame cutting edges may need light grinding before welding.
Any repair welding or local heating above the specified tempering range requires approval, because it can reduce the strength achieved by quenching and tempering.
Frequently Asked Questions
Q: What is ASTM A514 Grade Q?
A514 Grade Q is a quenched and tempered alloy steel plate grade under ASTM A514/A514M with a minimum yield strength of 690 MPa in sections up to 65 mm and excellent toughness for welded structural use.
Q: What is the equivalent of ASTM A514 Grade Q?
The commonly quoted equivalents are EN 10025-6 S690Q, GB/T 16270 Q690E, JIS G3128 SHY685N, the historical DIN 17102 StE690V, and ASTM A517 Grade Q at a similar strength level.
Q: What is the yield strength of A514 Grade Q?
The specified minimum yield strength is 690 MPa [100 ksi] for plate up to 65 mm thick and 620 MPa [90 ksi] for plate over 65 mm and up to 150 mm thick.
Q: What is the hardness of A514 Grade Q plate?
A514 Grade Q is quoted with a Brinell hardness range of 235-293 HBW in the quenched and tempered condition.
Q: Can A514 Grade Q be welded?
Yes, it is intended for welded structures, but a qualified procedure with low hydrogen consumables and controlled heat input is required to preserve toughness.
Q: Where is A514 Grade Q used?
Typical uses are offshore platform structures, mining and earth-moving equipment, heavy machinery, crane booms and other heavily loaded welded members.
