A514 Grade C vs Grade E: Composition, Strength & Thickness

ASTM A514 Grade C vs Grade E: Composition, Mechanical Properties, and Selection Guide

ASTM A514/A514M is the specification for high-yield-strength, quenched and tempered (Q&T) alloy steel plate suitable for welding. It covers plates up to 6 in. [150 mm] thick, produced in fourteen grades - A, B, C, E, F, H, J, K, M, P, Q, R, S and T. Every grade is delivered in the same Q&T condition and must satisfy the same thickness-graded tensile table, which is why the grades look interchangeable at first glance. They are not. The grades differ in alloy design, certified thickness ceiling, and therefore cost and application fit.

Grade C and Grade E are the two A514 grades that buyers most often confuse, partly because both are comparatively lean, low-carbon grades and partly because many online tables publish their chemistry incompletely. This guide compares the two grades using the chemical and mechanical requirements published in ASTM A514/A514M, so the numbers can be checked against the material test report (MTR) you receive with each plate.

Key Takeaways

What the chemistry means?

Grade C reaches the Q&T strength targets with a deliberately lean recipe: high manganese (1.10–1.50%) works with molybdenum (0.15–0.30%) and a small boron addition (0.001–0.005%). Boron is one of the most efficient hardenability elements in steel - a few thousandths of a percent in solid solution can do the work of several percent of more expensive alloy - which is why Grade C can meet 100 ksi minimum yield at up to 1¼ in. thick without chromium or nickel.

Grade E takes a different route. It replaces the heavy manganese addition with a full chromium–molybdenum package (1.40–2.00% Cr, 0.40–0.60% Mo), keeps the boron addition, and adds titanium (0.01–0.10%) to protect the boron from nitrogen so it stays available for hardening. Vanadium may be substituted for part or all of the titanium on a one-for-one basis. This design gives much deeper, more uniform hardenability - the property that lets Grade E hold certified strength all the way to 6 in. [150 mm].

All A514 grades share the same tensile requirement table (ASTM A514/A514M, Table 2), but the values step down with thickness. The table below gives the full ladder:

Certified Thickness: 32 mm vs 150 mm

ASTM A514/A514M, Table 1, publishes a maximum certified thickness for every grade. For Grade C it is 1¼ in. [32 mm]; for Grade E it is 6 in. [150 mm]. A plate thicker than 32 mm cannot be certified to Grade C chemistry and properties under the standard - any supplier offering "A514 Grade C" at 40 or 50 mm is quoting outside the specification. If the design calls for a 60 mm plate at 90 ksi minimum yield, the options are Grade E or another deep-hardening grade (P, Q, R and T also certify to 150, 150, 65 and 50 mm respectively).

Thickness also interacts with the property ladder: the 90 ksi yield row only exists for plates over 2½ in. [65 mm]. So for thick sections, both the grade and the thickness band must be checked together - a 120 mm plate is always on the 90 ksi row, whatever the grade.

A514 Grade C vs Grade E Selection Guidance

Choose Grade C when

• The finished part is 32 mm or thinner and the design is satisfied with 100 ksi (690 MPa) minimum yield.
• Cost per tonne matters: Grade C's leaner chemistry (no chromium, low molybdenum) carries lower alloy cost than Grade E.
• The component is high-volume or replaceable - machine frames, bucket and body liners, agricultural and construction equipment parts, general high-strength structural members in thin gauges.

Choose Grade E when

• The section exceeds 32 mm, up to 150 mm, and certified yield and tensile properties are required through the thickness.
• Heavy welded structures carry high static or fatigue loads - crane booms, large excavator and mining machine structures, transport trailer frames and beams, mobile aerial work platforms, heavy vehicle frames and chassis.
• Consistent through-thickness response in the Q&T process matters for machining or forming large plates.

For thin plates both grades certify to identical tensile values, so Grade E buys nothing extra in that range - specify it only when thickness or hardenability demand it. Related guidance for A514 and other high-strength plate series is available in the knowledge section of this site.

A514 Grade C vs Grade E steel plate Welding Considerations

A514 plates are Q&T alloy steels with carbon contents around 0.10–0.20%, and the specification's title states they are suitable for welding. Sound welds are achieved by controlling three things, normally through a qualified welding procedure specification (WPS) written to a structural code such as AWS D1.1:

• Hydrogen control: use low-hydrogen consumables (for example H5/H10 diffusible-hydrogen classes), stored and handled per the manufacturer's instructions, so the weld deposit and heat-affected zone are not charged with hydrogen.
• Preheat and interpass temperature: apply adequate preheat - commonly in the range of 50–150 °F (10–66 °C) depending on plate thickness and restraint - and keep interpass temperature within the qualified limits. The aim is to slow cooling in the heat-affected zone and prevent hydrogen-induced cracking.
• Heat input control: keep heat input moderate and follow the qualified envelope; excessive heat input can soften the quenched-and-tempered base plate adjacent to the weld.

Post-weld heat treatment is generally not required for A514 welds and may be undesirable for some grades, which can be sensitive to reheat cracking in the heat-affected zone. Confirm the procedure with the consumable supplier and the applicable code before production welding.

A514 Grade C vs Grade E plate Typical Applications

• Grade C: mining and earthmoving equipment components, dump truck bodies, agricultural machinery, machine frames, crane components in thin gauges, general high-strength structural parts where 32 mm or less is sufficient.
• Grade E: heavy crane booms, large excavator and mining machinery structures, transport trailer frames and beams, mobile aerial work platforms, heavy vehicle frames and chassis, thick-section structural members for bridges and buildings.

A514 is a structural plate specification, not a pressure-vessel material specification. For pressure-containing applications, confirm acceptance with the governing code (for example the ASME Boiler and Pressure Vessel Code) before specifying.