For carbon-steel pressure-vessel plate, the two ASTM specifications that show up on every inquiry are A516 Grade 70 and A285 Grade C, and they are not interchangeable: A516 Gr.70 is normalized-when-thick, killed, impact-tested, and code-stamped under ASME Section VIII for moderate- and lower-temperature welded pressure vessels, while A285 Gr.C is normally as-rolled and used for low-to-intermediate service where impact testing is not mandatory [S1][S3].
A516 Grade 70 covers an estimated 80%+ of A516 specification use cases and is what most engineers mean when they say "A516 plate" without naming a grade, while A285 Gr.C is the highest-strength of the three A285 grades (A/B/C) and is reserved for non-code or low-pressure shells, storage tanks, and boiler components [S3][S1].
Mechanical Properties: Yield, Tensile, Elongation
A516 Grade 70 specifies a minimum yield strength of 260 MPa (38 ksi) and a tensile range of 485–620 MPa (70–90 ksi), with minimum 21% elongation in 200 mm [S2][S3]. A285 Grade C specifies a minimum yield of 205 MPa (30 ksi) and a tensile range of 380–515 MPa (55–75 ksi), with 23% minimum elongation in 200 mm [S1][S2]. That gives A516 Gr.70 roughly 27% higher minimum yield and 27.6% higher minimum tensile strength than A285 Gr.C at near-identical gauge lengths, which is the whole reason an engineer pays the A516 premium when design pressure or wall-thickness optimization drives the spec [S3].
For comparison, A516 Grade 60 sits between them at 220 MPa yield / 415–550 MPa tensile and is the grade to drop down to when weldability in thick sections matters more than strength; A516 Grade 65 at 240 MPa / 450–585 MPa is the less-ordered middle step [S3]. The A285 family steps up in 3 roughly equal jumps: A285 Gr.A at 165 MPa / 310–450 MPa, A285 Gr.B at 185 MPa / 345–485 MPa, and A285 Gr.C at 205 MPa / 380–515 MPa [S1].
Chemical Composition and Deoxidation Practice
A516 mandates fully killed steel (deoxidized with silicon or aluminum) to eliminate gas porosity and deliver the homogeneous, sound plate required for welded pressure containment, with silicon held to 0.15–0.40% and phosphorus and sulfur each capped at 0.035% across all grades [S3]. Carbon rises with strength: A516 Gr.70 allows up to 0.27% C for ≤12.5 mm, 0.28% for 12.5–50 mm, and 0.30% for 50–100 mm thickness, paired with a manganese range of 0.85–1.20% [S3].
A285 Gr.C uses a different, more permissive deoxidation regime: the specification lets the manufacturer choose killed, semi-killed, capped, or rimmed steel practice, which is acceptable because the service is less demanding [S1]. Maximum carbon on A285 Gr.C is 0.28% (heat analysis) with manganese capped at 0.90%, and phosphorus and sulfur each limited to 0.025% [S1]. The lower manganese ceiling on A285 is one reason A516 outperforms A285 on through-thickness toughness after normalizing, and it is also why A516 commands a price premium per tonne [S3].
Heat Treatment, Thickness Limits, and Impact Requirements
A516 Gr.70 may be supplied as-rolled up to about 40 mm thickness, but normalizing is required above that threshold to refine grain and meet code toughness; post-weld heat treatment (PWHT) is also frequently invoked by ASME Section VIII after welding heavy sections [S3]. A285 Gr.C is normally delivered in the as-rolled condition; the standard explicitly excludes coils until they are cut to plate, and the plate must comply with A20/A20M for general requirements, testing, and retesting [S1].
Impact testing is the second hard differentiator: A516 Gr.70 is typically specified with 27 J Charpy V-notch at -46°C (or -20°C depending on the project) per the comparison data, and the value is a deliverable line item, not optional, on most code-stamped vessels [S2][S3]. A285 has no mandatory Charpy requirement and is described in the comparison table as "Low" impact, with a temperature ceiling of ≤400°C versus ≤455°C for A516 Gr.70 [S2]. This is the single biggest reason a low-temperature (-29°C or below) LPG or ammonia tank is never built from A285 [S1][S2].
Code Acceptance, Certification, and Cross-Standard Equivalents
A516 carries an ASME twin designation, SA516 Grade 70, which means it is pre-qualified for Section VIII Div. 1 and Div. 2 pressure vessel construction without case-by-case approval, with mill certification typically issued to EN 10204 3.1 or 3.2 [S3][S4]. A285 likewise has an SA285 twin used under the ASME code, but the scope is narrow: low- and intermediate-pressure firebox and other non-corrosive service, and it is not the default choice for new code-stamped vessels [S5].
Cross-standard equivalents differ by source and by what is being matched (yield vs. tensile vs. chemistry). A516 Gr.70 maps to EN 10028-2 P355GH and to GB 713 Q345R, while A516 Gr.60 maps to EN P265GH and GB Q245R [S2][S4]. For A285 Gr.C, EN 10028-2 P235GH or P265GH, DIN 17155 HI or HII, JIS G3115 SPV235, and GB 713 Q245R are cited as equivalents in the cross-walk tables, though the sources note explicitly that equivalents are not identical and that impact requirements, heat-treatment condition, and certification (ASME / PED / EN 10204 3.1) must always be re-verified [S2][S5].
Decision Matrix: When to Pick A516 Gr.70 vs A285 Gr.C
Pick A516 Gr.70 when the vessel is code-stamped under ASME Section VIII, when design temperature drops below -20°C or impact testing is required, when wall-thickness optimization matters, or when the thickness will exceed ~40 mm and normalizing is on the table [S2][S3]. Pick A285 Gr.C when the service is non-code, low-pressure (typical MAWP well under ~10 bar), above -20°C, and budget pressure outweighs the need for normalized delivery and Charpy documentation; it is also the right call for storage-tank shells, simple boiler components, and general welded pressure-containing equipment where moderate strength is sufficient and the higher-strength PVQ grade is not required [S1][S6].
For a procurement-side shortlist: if the inquiry says "ASME," "PED," or names a calculated design temperature below 0°C, default to A516 Gr.70 and confirm whether normalizing is required at the ordered thickness; if the inquiry says "API 650 atmospheric tank," "non-code," or quotes thicknesses under 25 mm at ambient service, A285 Gr.C is usually adequate and noticeably cheaper per tonne [S1][S3][S6].
Limitations, Supply Considerations, and Traceable Signals
Two real-world constraints drive most of the spec-confusion incidents. First, ordering A285 outside the thickness range normally stocked for the grade can force a re-specification, usually to A516 or A515, regardless of strength needs [S1]. Second, A516 Gr.70 sourced from mills without proper normalizing furnaces may fail Charpy at the MTR stage; the safest procurement signal is a mill test certificate to EN 10204 3.1 (or 3.2 for higher risk) showing the actual impact values at the specified test temperature, not just a "normalized" stamp on the certificate [S3][S4].
Track the next three signals on any live project: (1) confirm the ordered thickness is inside the normalizing threshold for A516 or inside the range readily available for A285; (2) confirm the Charpy test temperature on the MTR matches the design MDMT, with 27 J at -46°C the common A516 call-out; (3) for EN 10028-2 substitution on PED projects, lock the certificate to P265GH (≈A516 Gr.60) or P355GH (≈A516 Gr.70) and do not accept A285 equivalents for code-stamped vessels [S2][S3][S4].