ASTM A515 Gr 65 and A516 Gr 65 are both carbon steels for pressure vessels, but A515 is for intermediate-to-higher temperatures, while A516 is for moderate-to-lower temperatures with better toughness, with A515 Gr 65 having slightly higher tensile strength (450-585 MPa) but similar yield strength (240 MPa) to A516 Gr 65, differing mainly in their intended service conditions and optimized properties for those environments. Both A515 gr 65 steel and A516 gr 65 steel are carbon steel plates for pressure vessels. What are the differences between them? Below are the details that introduce these differences in chemical composition, tensile requirement and application.
The chemical composition comparison
A515 gr 65 steel composition(%)
C |
Mn |
P |
S |
Si |
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|
t≤25 |
25<t≤50 |
50<t≤100 |
100<t≤200 |
200<t |
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|
0.28 |
0.31 |
0.33 |
0.33 |
0.33 |
0.90 max |
0.035 max |
0.035 max |
0.15~0.40 |
A516 gr 65 steel composition(%)
Maximum C for thickness t (mm) |
Mn % for thickness t (mm) |
Si |
P max |
S max |
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|
6-12.5mm |
12.5-25mm |
25-50mm |
>50mm |
≤12.5mm |
>12.5mm |
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|
0.24 |
0.26 |
0.26 |
0.28 |
0.85-1.20 |
0.85-1.20 |
0.13-0.45 |
0.035 |
0.035 |
Tensile requirement comparison
A515 gr 65 steel mechanical properties
Grade |
Yield strength |
Tensile strength |
Elongation |
|
|
ksi(N/mm²) |
ksi(N/mm²) |
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|
A515 grade 65 |
35 (240) min |
65~85 (450~585) |
8 in. [200 mm], min, % |
19 min |
|
2 in. [50 mm], min, % |
23 min |
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A516 gr 65 steel mechanical properties
Grade |
Tensile strength |
Minimum yield strength |
Minimum elongation (%) gauge length |
|
|
(MPa) |
(MPa) |
50mm |
200mm |
|
|
A516 grade 65 |
450 - 585 |
240 |
23 |
19 |
The application comparison
A515 gr 65 carbon-silicon steel plates are primarily for intermediate- and higher-temperature service in welded boilers and other pressure vessels.
A516 gr 65 carbon steel plates are intended primarily for service in welded pressure vessels in moderate- and lower-temperature service.
Key Differences
Service Temperature:
A515 Gr 65: Designed for intermediate and higher temperatures in boilers and pressure vessels.
A516 Gr 65: Designed for moderate to low temperatures, emphasizing toughness (notch resistance).
Properties (Grade 65):
Yield Strength: Both have a minimum yield strength of 240 MPa (35 ksi).
Tensile Strength: A515 Gr 65 is typically 450-585 MPa (65-85 ksi), while A516 Gr 65 is also 450-585 MPa (65-85 ksi), though A515's higher carbon content gives it harder characteristics for heat.
Elongation: A515 Gr 65 has a slightly lower minimum elongation (19%) compared to A516 Gr 65 (23%) in 200mm, reflecting A516's toughness focus.
Chemistry & Processing:
A515 often has a slightly higher carbon content (around 0.28-0.33%) for strength at higher heat, while A516 (around 0.24-0.29% C) is more balanced for toughness, often requiring normalization for thickness.
In Simple Terms
Choose A515 Gr 65 when your pressure vessel operates in hotter conditions and needs strength at elevated temperatures.
Choose A516 Gr 65 when low-temperature performance and resistance to brittle fracture (toughness) are critical, as in many general pressure vessel applications.
