ASTM A516 is one of the most widely specified carbon steel plate standards for welded pressure vessels, boilers, heat exchangers, separators, storage tanks, and process equipment used in moderate and lower temperature service. When engineers, buyers, and fabricators search for a516 grade 70 vs grade 60 difference, they usually need more than a simple tensile strength comparison. They need to know how the two grades differ in mechanical properties, chemical limits, weldability, forming behavior, impact performance considerations, and practical ASME design implications.
ASTM A516 Grade 60 and ASTM A516 Grade 70 belong to the same specification family and are both intended for pressure vessel service where good notch toughness and reliable fabrication are important. Grade 70 is more commonly specified in modern refinery, petrochemical, and process plant fabrication because it offers higher minimum strength. Grade 60 remains relevant where lower design stress is acceptable, where legacy drawings already call for it, or where forming and cost considerations favor a lower strength plate.
What is the difference between A516 Grade 70 and Grade 60?
The primary difference between A516 Grade 70 and A516 Grade 60 is minimum mechanical strength. Grade 70 has higher minimum tensile strength and higher minimum yield strength than Grade 60. In practical pressure vessel design, this can permit higher allowable stress or, in some cases, reduced required plate thickness, subject to ASME Section VIII calculations, corrosion allowance, joint efficiency, service temperature, and any impact test requirements.
However, strength is not the only selection factor. Buyers should also review plate thickness range, chemistry limits, weld procedure qualification, post-weld heat treatment requirements, forming severity, and whether the equipment will operate in conditions where notch toughness or low-temperature performance becomes critical.
A516 Grade 70 vs Grade 60 mechanical properties
The table below summarizes the standard differences commonly referenced in procurement and fabrication. Actual mill test certificate values may vary within ASTM limits.
| Property | ASTM A516 Grade 60 | ASTM A516 Grade 70 | Practical meaning |
|---|---|---|---|
| Minimum tensile strength | 60 ksi (415 MPa) | 70 ksi (485 MPa) | Grade 70 withstands higher applied stress |
| Minimum yield strength | 32 ksi (220 MPa) | 38 ksi (260 MPa) | Grade 70 generally supports higher design stress |
| Elongation | Specified by thickness | Specified by thickness | Both grades are suitable for forming when processed correctly |
| Typical pressure vessel use | Moderate strength applications | Higher strength vessel applications | Grade 70 is more common for new builds |
| Potential thickness optimization | Lower | Higher | Grade 70 may reduce required thickness in some designs |
| Weldability | Good | Good | Both are routinely welded in vessel shops |
From a design perspective, the higher yield and tensile values of Grade 70 are the reason it is frequently chosen for reactors, columns, drums, and pressure-retaining shells where wall thickness has a direct effect on fabrication cost, weld volume, and handling weight.
Chemical composition and specification context
ASTM A516 covers carbon steel plates intended primarily for service in welded pressure vessels where improved notch toughness is important. The specification includes multiple grades, including Grade 55, Grade 60, Grade 65, and Grade 70. Grade 60 and Grade 70 are often compared because they are both common in industrial procurement and are close enough in fabrication behavior to be considered alternatives during design review.
While exact chemistry limits depend on thickness and the applicable edition of the standard, both grades are carbon-manganese steels with controlled levels of phosphorus and sulfur. Mill producers may use fine grain practice or supplementary requirements depending on the order. In practical terms, chemistry is managed to balance strength, weldability, toughness, and plate quality.
Grade 70 may achieve its higher strength through chemistry control and rolling practice, but it remains a pressure vessel quality plate rather than a high-alloy material. That means both grades are still considered readily fabricable carbon steel plates when proper welding procedures, preheat practices, and heat input controls are followed.
How the grades affect ASME pressure vessel design
For ASME Section VIII applications, material selection is not based on ASTM minimum tensile strength alone. Designers must use the allowable stress values listed in the applicable ASME code section. Even so, the higher strength of SA/ASTM A516 Grade 70 often translates into a design advantage over Grade 60.
That advantage can matter in several ways:
- Reduced shell or head thickness in some pressure calculations
- Lower vessel weight, which can reduce support steel and transportation load
- Less weld metal volume due to thinner sections
- Potentially shorter fabrication time for large vessels
- Better suitability for higher pressure service within carbon steel design limits
At the same time, thinner is not always better. Minimum practical thickness may still be governed by corrosion allowance, external loads, nozzle reinforcement, vacuum conditions, transport handling, or client specification minimums. In many real projects, these factors reduce the theoretical thickness savings that Grade 70 can provide.
Weldability, forming, and fabrication differences
Both A516 Grade 60 and Grade 70 are widely used in fabrication shops because they offer good weldability and forming performance. They are commonly processed by cutting, rolling, pressing, welding, and post-weld heat treatment as required by code or service conditions.
In general, Grade 60 may be preferred where severe cold forming is involved because lower strength material can be somewhat easier to form. Grade 70, while still very formable, may require closer attention to bend radius, forming sequence, and residual stress management on heavier sections.
For welding, both grades are commonly joined using standard pressure vessel procedures such as SMAW, SAW, GMAW, and FCAW, depending on thickness and shop practice. Fabricators should still consider:
- Plate thickness and restraint level
- Required preheat based on carbon equivalent and procedure qualification
- Hydrogen control for crack prevention
- Post-weld heat treatment requirements from code or purchaser specification
- Impact test requirements if the service temperature is low
In other words, the difference between Grade 60 and Grade 70 is not that one is weldable and the other is not. Both are weldable. The more important issue is that higher strength and heavier section thickness demand tighter procedure control.
Typical applications for Grade 60 and Grade 70
Both grades are used across oil and gas, refining, fertilizer, chemical processing, power generation, and general industrial fabrication. The final choice depends on design pressure, wall thickness economics, fabrication route, and project specification.
A516 Grade 60 is commonly considered for:
- Moderate pressure vessels
- Legacy replacement equipment
- Applications where thickness reduction is not a major driver
- Projects prioritizing easier forming or specification continuity
A516 Grade 70 is commonly considered for:
- Refinery and petrochemical vessels
- Boilers and process pressure parts
- Columns, drums, and separators
- Applications where higher allowable stress can improve design efficiency
- New fabrication where Grade 70 has become the default purchasing grade
Which grade should buyers choose?
If the question is simply which grade is stronger, the answer is A516 Grade 70. If the question is which grade is better, the answer depends on the design basis.
Choose Grade 70 when higher strength, possible thickness optimization, and broad market acceptance are important. Choose Grade 60 when the design does not require the extra strength, when a legacy code sheet or drawing already specifies it, or when fabrication preferences make a lower strength plate more practical.
Before ordering, buyers should verify the following on the purchase specification:
- ASTM A516 or ASME SA516 designation
- Required grade: 60 or 70
- Plate thickness and dimensions
- Normalizing or as-rolled condition if applicable
- Impact test or supplementary requirements
- NACE or sour service requirements if applicable
- Mill test certificate and traceability expectations
This is important because a material described casually as “boiler quality plate” may still require project-specific conditions beyond the base ASTM grade designation.
Summary of A516 Grade 70 vs Grade 60 difference
The most important difference is that A516 Grade 70 has higher minimum tensile and yield strength than A516 Grade 60. That higher strength often makes Grade 70 the preferred option for pressure vessel fabrication because it can improve design efficiency and may reduce required thickness in some applications. Grade 60 remains a valid and useful pressure vessel plate where moderate strength is sufficient and where fabrication or specification factors support its use.
For pressure vessel procurement, the correct comparison is not only material strength but also ASME allowable stress, fabrication method, service conditions, notch toughness requirements, and total installed cost. A proper grade decision should always be based on the vessel design calculation and the governing code requirements.
FAQ
Is A516 Grade 70 stronger than A516 Grade 60?
Yes. A516 Grade 70 has higher minimum tensile strength and higher minimum yield strength than A516 Grade 60. This is the main reason Grade 70 is more commonly selected for pressure vessel applications where design efficiency matters.
Can A516 Grade 70 replace Grade 60?
Sometimes, but not automatically. Although Grade 70 is stronger, substitution must be reviewed against the design code, approved drawings, welding procedures, impact requirements, and purchaser specification. Material replacement in pressure equipment should always be engineering-approved.
Which is better for pressure vessels, A516 Grade 60 or Grade 70?
Neither grade is universally better in every case. Grade 70 is often preferred for new pressure vessel construction because of its higher strength and possible thickness savings. Grade 60 is still suitable for many moderate pressure applications and for projects where existing design documents already specify that grade.