ASTM A516 is one of the most widely used carbon steel plate specifications for welded pressure vessels, boilers, heat exchangers, separators, columns and storage tanks intended for moderate and lower temperature service. When engineers search for the a516 grade 70 vs grade 60 difference, the comparison usually starts with strength values, but practical selection goes further than tensile and yield numbers alone. Design allowable stress, required plate thickness, forming severity, weld procedure qualification, notch toughness, post-weld heat treatment and project code requirements all influence whether Grade 60 or Grade 70 is the more suitable material.
Both grades belong to the same ASTM A516 specification family and are commonly supplied as pressure vessel quality plate in the as-rolled, normalized or stress-relieved condition depending on thickness and purchase requirements. Grade 70 is more frequently specified in new refinery, petrochemical and process plant fabrication because it offers higher minimum mechanical strength. Grade 60 remains relevant for legacy equipment replacement, moderate design stress applications and projects where lower strength plate is acceptable from a forming or cost standpoint.
What is the difference between A516 Grade 70 and Grade 60?
The primary difference between ASTM A516 Grade 70 and ASTM A516 Grade 60 is their minimum mechanical strength. Grade 70 has higher minimum tensile strength and higher minimum yield strength than Grade 60. In pressure vessel design, that higher strength can support higher allowable stress values under the applicable design code, or in some cases allow a reduction in required nominal thickness after considering corrosion allowance, joint efficiency, forming losses and minimum code thickness rules.
However, higher strength does not automatically make Grade 70 the best choice in every application. Fabricators also evaluate bend radius, cold forming strain, preheat requirements, weld heat input, repair welding, impact test obligations and whether the purchase specification requires supplementary testing such as ultrasonic examination, HIC resistance or NACE-related compliance. For that reason, the correct answer to the A516 Grade 70 vs Grade 60 comparison is both a material property question and a fabrication engineering question.
A516 Grade 70 vs Grade 60 mechanical properties
The table below summarizes the standard differences most often referenced during procurement and fabrication review. Actual certified values on the mill test certificate can vary within ASTM limits and should always be checked against project specifications and code calculations.
| Property | ASTM A516 Grade 60 | ASTM A516 Grade 70 | Practical implication |
|---|---|---|---|
| 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 can be formed with controlled procedures |
| Typical service | Moderate strength vessel applications | Higher strength vessel applications | Grade 70 is more common in new pressure vessel builds |
| Thickness optimization potential | Lower | Higher | Grade 70 may reduce required thickness in some designs |
| Weldability | Good | Good | Both are routinely welded in pressure vessel fabrication shops |
From a design standpoint, the higher yield and tensile values of Grade 70 are the main reason it is often preferred for pressure-containing equipment. Even so, the final material call should be based on the governing code calculation rather than on strength values in isolation.
Design and thickness implications in pressure vessel fabrication
In many vessel and boiler applications, material grade selection is linked directly to required shell, head or nozzle reinforcement thickness. Because Grade 70 has higher minimum strength, it may permit a thinner plate than Grade 60 for the same internal pressure and design conditions, subject to ASME Section VIII or other applicable code rules. This can influence total vessel weight, forming load, welding volume and transportation constraints.
That said, thickness reduction is not always achieved in practice. Several factors can offset the theoretical benefit:
- Minimum code thickness or purchaser minimum thickness requirements
- Corrosion allowance dominating the total required thickness
- External loads, wind, seismic or support loads controlling the design
- Impact test exemptions changing with thickness and service temperature
- Availability of standard mill plate sizes and stock thicknesses
For this reason, procurement teams should avoid assuming that Grade 70 automatically lowers project cost. A proper comparison should include design calculations, plate nesting, fabrication hours and weld volume.
Weldability, forming and heat treatment considerations
Both ASTM A516 Grade 60 and Grade 70 are considered readily weldable carbon steel plates when standard pressure vessel fabrication practices are followed. They are commonly joined by SMAW, SAW, GTAW, GMAW and FCAW processes using qualified welding procedures. In routine shop fabrication, both grades can be cut, rolled, pressed and welded without unusual difficulty.
Even so, Grade 70 may require closer control where plate thickness is high, restraint is severe or low ambient temperature fabrication is involved. Fabricators typically review the following before finalizing the grade:
- Plate thickness and whether normalization is required by specification or code
- Preheat and interpass temperature based on thickness and carbon equivalent
- Cold forming severity and any subsequent heat treatment requirement
- Post-weld heat treatment requirements for the vessel category and thickness
- Supplementary impact testing or low-temperature service qualification
In severe forming applications, some shops may prefer the lower strength grade if the design permits it, especially where tight radii or repeated forming operations are involved. The decision depends on the fabrication route, not only on the material specification line item.
Typical applications of A516 Grade 60 and Grade 70
Both grades are used in pressure-retaining equipment, but Grade 70 has become the more common specification in current industrial projects. Typical applications include:
- Pressure vessels and storage tanks
- Boilers and boiler components
- Heat exchangers and condensers
- Separators, scrubbers and process columns
- Refinery and petrochemical equipment
- Power plant and utility process systems
Grade 60 is still encountered in replacement work, existing plant maintenance and applications where moderate design stress is sufficient. Grade 70 is generally selected when designers want higher strength margins or improved efficiency in pressure-containing sections.
How to choose between A516 Grade 70 and Grade 60
A practical grade selection review should include more than a mechanical property comparison. Engineers, buyers and QA teams should check the following points before issuing a purchase order:
- Required design pressure and temperature under the governing code
- Allowable stress values used in the design calculation
- Plate thickness range and whether normalized material is required
- Impact test, MDMT or notch toughness obligations
- Welding procedure qualification and PWHT requirements
- Supplementary requirements such as UT, HIC, SSC or NACE-related testing
- Availability of plate dimensions, lead time and replacement compatibility
If the application is a new pressure vessel with optimization of thickness and weight as a priority, Grade 70 is often the logical choice. If the project is a like-for-like replacement, a moderate stress design or a fabrication-sensitive component, Grade 60 may still be fully appropriate.
A516 Grade 70 vs Grade 60: summary
To summarize the a516 grade 70 vs grade 60 difference, Grade 70 provides higher minimum tensile and yield strength than Grade 60 and is therefore more commonly used in modern pressure vessel construction. This higher strength can support higher allowable stress or reduced thickness in some designs, but actual selection must also consider code rules, service temperature, impact testing, fabrication method and availability.
Neither grade should be treated as universally better. The correct specification is the one that satisfies the design basis, fabrication route and inspection requirements with documented compliance. For procurement and engineering teams, the most reliable approach is to compare certified mechanical properties, code design calculations and project-specific supplementary requirements before final material approval.
FAQ
Is A516 Grade 70 stronger than Grade 60?
Yes. ASTM A516 Grade 70 has higher minimum tensile strength and higher minimum yield strength than ASTM A516 Grade 60. That is the main technical difference between the two grades and the reason Grade 70 is often preferred for higher stress pressure vessel applications.
Can A516 Grade 70 replace A516 Grade 60?
Not automatically. Although Grade 70 is stronger, substitution still requires review of the design code, welding procedure qualification, impact test requirements, forming conditions and purchaser specification. Material substitution should be approved by the responsible design or quality authority.
Which grade is more commonly used in pressure vessels?
A516 Grade 70 is generally more common in new pressure vessel and process equipment fabrication because of its higher strength and broader use in refinery, petrochemical and power projects. Grade 60 is still used where design stress is lower or where replacement compatibility with existing equipment is important.