Choosing the right carbon steel pressure vessel plate can make the difference between years of safe operation and premature failure. Many engineers and procurement teams consider ASTM A516 Gr 60 & Gr 70 plates interchangeable. They are not. This choice has a direct impact on structural integrity, fabrication behaviour and the overall cost of the project. Both grades are widely available on boiler quality plates, storage tanks and high-pressure equipment. It is important to understand the properties of ASTM A516 plate and the pressure vessel steel grades before ordering any material.
What is ASTM A516 Plate?
ASTM A516 is a specification for carbon steel plates for moderate and lower-temperature service in welded pressure vessels and industrial boilers developed by ASTM International. The standard defines four grades with minimum tensile strength in ksi of 55, 60, 65 and 70. These are carbon manganese steels, simple in chemistry, but carefully engineered for demanding service.
ASTM A516 material is very popular due to its good weldability and excellent notch toughness. Notch toughness is the property of a material to resist brittle fracture at stress concentrations, such as weld notches or structural discontinuities. Important property for low-temperature service. Plates to this specification are employed in refineries, chemical plants, and power generation facilities, which are subjected to continuous stress due to temperature cycling and internal pressure on the material.
Overview of Gr 60 vs Gr 70
ASTM A516 Gr 60 plates and ASTM A516 Gr 70 plates are both part of the same family of carbon manganese steel in the same standard. Their chemical composition is similar with controlled levels of carbon, manganese, phosphorus, sulphur and silicon. It’s the mechanical performance that makes it different, not chemistry.
Gr 60 has medium strength with some additional ductility. It is suitable for applications where formability is more important than load-carrying ability. Gr 70 has higher yield and tensile strength and is used in more demanding pressure and structural applications. Same good standard. Two performance levels.
Mechanical Properties Comparison
This section presents the comparison of mechanical properties of ASTM A516 Gr 60 and Gr 70 for pressure vessel material selection with the emphasis on strength, ductility and toughness.
Yield strength
Gr 60 has a minimum yield strength of about 220 MPa (32 ksi) compared to Gr 70, which has a minimum yield strength of approximately 260 MPa (38 ksi). The 40 MPa difference is not negligible when it comes to determining the wall thickness of a pressure vessel, which has an immediate impact on the amount of material used and the weight of the structure.
Tensile Strength
The tensile strength of Gr 60 runs from 415 to 550 MPa (60 to 80 ksi). Gr 70 operates in a higher band, from 485 to 620 MPa (70 to 90 ksi). Designers working to ASME Section VIII will find that Gr 70’s higher allowable stress values can permit thinner shell sections in high-pressure applications.
Ductility
Gr 60 shows better ductility than Gr 70. Its higher percentage elongation also allows for cold forming and bending into vessel heads or complex geometries without the risk of cracking during fabrication.
Impact Toughness
Gr 70 absorbs higher stress loads before failure. In applications with fluctuating pressure cycles or elevated operational stress, its toughness at higher strength levels gives it a clear functional advantage over the lower grade.
Fabrication and Performance Differences
Fabrication behaviour is where the grade choice becomes practical. Both respond differently to cutting, forming, and joining despite sharing similar chemistry.
Weldability
Gr 60 is easier to weld because of its lower carbon content, which causes less hardening of the heat-affected zone and a lower risk of hydrogen-induced cracking, so there is less preheat required for many applications. Gr 70 is weldable but requires more careful attention to welding procedure specifications, especially for thicker sections.
Formability
Gr 60 bends and shapes with less resistance. Fabricators forming vessel heads, dished ends, or curved shell sections find it more forgiving on press brakes and rolls, reducing spring-back and tool wear.
Machining
Both grades machine without significant difficulty using conventional tooling. Gr 70 is slightly harder, so cutting speeds may need minor adjustment for extended precision operations.
Heat Treatment
Both grades are typically supplied in the as-rolled or normalised condition. Normalising refines grain structure and improves toughness uniformity across the plate thickness, and is specified for thicker plates or critical service.
Thickness Availability
Gr 70 is more commonly stocked in heavier plate thicknesses by mills and service centres, reflecting its wider use in large-scale pressure vessels where substantial section thicknesses are required.
Applications of Gr 60 vs Gr 70 Plates
Both ASTM A516 Gr 60 plates and ASTM A516 Gr 70 plates have well-defined roles across many industries. The appropriate grade is decided by the environment of operation.
Pressure Vessels
Gr 60 is appropriate for moderate pressure vessel manufacture where internal loads are manageable, and weight savings are unimportant. Gr 70 is designed for high-pressure systems such as reactors and separators subject to high loads. Because of the higher allowable stress values under ASME codes, it can be used with less wall thickness and still be within safety margins. It is the grade of choice for compact, high-performance vessel designs.
Boiler and heat exchanger
In boiler and heat exchanger fabrication, Gr 70 is preferred. Its strength and notch toughness can withstand thermal cycling and pressure fluctuations that would fatigue lower-grade materials faster. Gr 70 is widely specified for the construction of shell and tubesheet of water tube boilers, shell, tube exchangers and superheater vessels.
Storage Tanks
Gr 60 is widely used in storage tank construction where pressures are low and cost sensitivity is high. Atmospheric tanks, low-pressure LPG vessels, and water storage structures benefit from its adequate strength at a lower cost. When wall thickness is driven by hydrostatic head rather than internal pressure, Gr 60 performs without overspending on unused strength.
Petrochemical Industry
Gr 70 is utilised in the petrochemical industry. Carbon steel pressure vessel plates are used for processing columns, pressure reactors and refinery separators that will be subject to long-term mechanical and thermal demands where material underperformance can have serious safety consequences.
Cost Comparison
Gr 60 is the more economical option. Its lower strength requirements mean simpler mill processing and lower raw material costs per tonne. It delivers dependable performance at a lower cost for budget-aware projects where the conditions do not require increased strength.
Gr 70 commands a small premium on the basis of its higher specs and solid industrial demand. The cost gap is not large, but it compounds on heavy orders. The real question is not which grade costs less, but whether Gr 60 savings hold up against the risk of underspecifying the material for the application.
How to Choose Between Gr 60 and Gr 70
The decision rests on operating pressure, fabrication method, and budget. Neither grade is universally better.
Gr 60 is appropriate for moderate-pressure applications where internal loads sit within the lower range of design code requirements. It is also the right call when fabrication involves cold forming, bending, or rolling, since its ductility reduces forming risk. Projects with tighter budgets and no performance justification for an upgrade will find Gr 60 a sound, code-compliant choice.
Gr 70 is justified when the service environment demands higher strength, when thinner plate sections are needed without sacrificing pressure rating, or when long-term durability is a design priority. Any project in petrochemical processing, refining, or high-pressure power generation should default to Gr 70 unless the conditions clearly point otherwise.
Conclusion
The key differences between ASTM A516 Gr 60 plates and ASTM A516 Gr 70 plates come down to strength, fabrication behaviour, and cost. Gr 60 is for moderate pressure, cost-conscious applications where ease of forming is a priority. Gr 70 is built for the tough environments where strength and durability matter. Selecting the wrong grade, even within the same standard, carries real engineering and financial risk. Consulting a qualified materials engineer or a trusted carbon steel pressure vessel plates supplier before finalising a grade specification is a step that consistently pays for itself.
