A vessel built one grade too light will pass inspection on day one and still cost a plant millions the day it doesn’t. That’s the stakes behind choosing between SA 516 Grade 60 and Grade 70 plates. Both sit under the same ASME specification, yet a 70 MPa gap in tensile strength separates them, and that gap decides whether a fabricator can use thinner steel or has to add weight to stay safe. Rexton Steel and Alloys stocks both grades as part of its SA 516 GR.60/70 plate range, supplying fabricators who need the correct grade on site without delay.
Understanding SA 516 Grade 60 Plate
Chemical Composition
Carbon stays between 0.21% and 0.31% depending on plate thickness. Manganese runs from 0.85% to 1.20%. Phosphorus and sulfur stay capped at 0.035% each, which keeps the steel free of the impurities that make the pressure-retaining plate brittle under load.
Mechanical Properties
Tensile strength sits between 415 and 550 MPa (60 to 80 ksi), with a minimum yield of 220 MPa (32 ksi). Elongation has to be at least 21%. That ductility margin lets the plate bend and roll during fabrication without cracking at the forming radius.
Advantages of Grade 60
Welding shops favor this grade for one reason: lower carbon means less preheat, fewer cracked welds, and less post-weld heat treatment. Material cost runs lower too, often the deciding factor on jobs where design pressure never gets close to the plate’s limits.
Common Applications
Storage tanks lean on Grade 60 constantly, as do low-pressure boilers and standard heat exchangers. Separators built for mild chemical service fit here too. Anywhere the design pressure stays inside ordinary limits, this grade does the job without paying for strength nobody needs.
Understanding SA 516 Grade 70 Plate
Chemical Composition
Carbon stays in the range of 0.27% to 0.31%, and manganese can reach 1.30%. Phosphorus and sulfur hold at the same 0.035% ceiling as Grade 60. That slightly richer chemistry is what pushes the strength numbers up without turning the plate brittle.
Mechanical Properties
Tensile strength runs from 485 to 620 MPa (70 to 90 ksi), and minimum yield jumps to 260 MPa (38 ksi). Elongation drops slightly, landing between 17% and 21% depending on thickness, a small ductility trade for a meaningful strength gain.
Advantages of Grade 70
Designers get to shave plate thickness while holding the same pressure rating, cutting vessel weight and freight cost. Less steel also means less welding per joint. For high-pressure service, the strength headroom buys a margin Grade 60 doesn’t offer at equal thickness.
Common Applications
Refineries reach for Grade 70 by default. Petrochemical reactors, high-pressure boilers, and gas-service separators all draw on this grade, along with storage spheres holding volatile products under constant pressure. Continuous-duty plants running 24-hour cycles specify it because fatigue resistance matters more than upfront cost.
SA 516 Gr. 70 vs SA 516 Gr. 60 Plate: Key Differences
Tensile Strength
A 70 MPa difference separates the two grades at their upper limits, 550 MPa for Grade 60 against 620 MPa for Grade 70. Engineers use that spread to size wall thickness. Thinner walls become possible the moment a vessel calls for Grade 70 instead of Grade 60.
Yield Strength
40 MPa is the gap here, 220 versus 260 MPa minimum. Under repeated pressure cycling, that extra margin matters because it pushes back the point where the steel deforms permanently instead of springing back.
Pressure Handling Capability
At identical thickness, Grade 70 simply tolerates more pressure. Vessels rated above 150 PSI usually get specified in Grade 70 for this reason alone, since holding the rating in Grade 60 would mean adding wall thickness and weight.
Weldability
Grade 60 has a greater ease of welding due to its lower carbon. Grade 70 isn’t difficult, but thicker sections require controlled preheat to keep hydrogen cracking out of the weld.
Toughness and Durability
Normalized, both grades clear standard Charpy impact requirements. Grade 70 separates itself on crack resistance under sustained high stress; Grade 60 holds up fine in moderate service but wasn’t built to chase that extra margin.
Cost Considerations
Per tonne, Grade 60 costs less to produce since the alloying stays simple. Grade 70 carries a premium, though a vessel built thinner in Grade 70 can land at a similar total material cost once tonnage drops.
Comparison Table: SA 516 Grade 70 vs Grade 60
| Property | SA 516 Grade 60 | SA 516 Grade 70 |
| Tensile Strength | 415–550 MPa (60–80 ksi) | 485–620 MPa (70–90 ksi) |
| Yield Strength (min) | 220 MPa (32 ksi) | 260 MPa (38 ksi) |
| Carbon Content (max) | 0.21–0.31% | 0.27–0.31% |
| Manganese Content | 0.85–1.20% | up to 1.30% |
| Elongation (min) | 21% | 17–21% |
| Weldability | Easier, lower preheat | Good, may need controlled preheat |
| Typical Pressure Range | Low to moderate | Moderate to high |
| Relative Cost | Lower | Higher |
| Common Use | Storage tanks, low-pressure boilers | Refinery vessels, high-pressure reactors |
Why SA 516 Grade 70 Is the Preferred Choice for High-Pressure Applications?
Three numbers explain why refineries default to Grade 70. A tensile ceiling of 620 MPa lets engineers hold thinner plate while keeping the same safety factor a thicker Grade 60 build would need. A 260 MPa yield point raises the threshold before permanent deformation sets in. And over a 20 to 30 year service life, that margin shows up as fewer fatigue failures and fewer unplanned shutdowns, the real payoff for plants running continuous operations.
When Should You Choose SA 516 Grade 60?
If the design pressure sits in moderate territory and the budget is doing the deciding, Grade 60 is the right call. Storage tanks and low-pressure boilers almost never use the extra 70 MPa of tensile margin Grade 70 carries, so paying for it adds cost without adding value. Standard process equipment built to run within ordinary code limits is where this grade earns its keep.
Factors to Consider When Selecting Between Grade 60 and Grade 70
Design Pressure Requirements
Check the maximum allowable working pressure calculation first. Once that figure pushes plate thickness past what’s practical in Grade 60, switching to Grade 70 brings the thickness back down while keeping the same rating.
Operating Temperature
Standard ASME temperature ranges suit both grades, but extreme service conditions can trigger additional impact testing or normalization on either one. Check the derating curve against the wall thickness before locking in a grade.
Fabrication and Welding Needs
A shop without preheat control will move faster on Grade 60, especially on thick plate. Grade 70 still welds without trouble, just with documented procedure above 25mm.
Industry Standards and Compliance
Sometimes the client specification, the insurer, or the local code decides the grade regardless of what the pressure calculation says. Confirm those requirements before ordering the plate.
Project Budget
Tight budgets and moderate pressure point toward Grade 60. Larger vessels often flip that calculation, since a thinner Grade 70 plate can mean less total tonnage and a lower freight bill despite the higher per-tonne price.
Conclusion
Both grades meet the same ASME specification, but they’re built for different applications. Grade 60 keeps cost down on moderate-pressure, standard-duty vessels. Grade 70 earns its premium on high-pressure refinery and petrochemical work where the extra tensile and yield margin translates directly into service life. The right answer comes from matching design pressure, budget, and fabrication capability to the grade, not the other way around.
