ASTM A516 Gr 70 Steel: Pressure Vessel Specification Guide

ASTM A516 Gr 70 is the workhorse grade for pressure vessel and boiler steel plate. It offers a well-balanced combination of strength, weldability, and toughness at moderate cost, and it is accepted by ASME Section VIII for the construction of pressure vessels. If you buy or sell steel plate for tanks, boilers, reactors, separators, or columns, you will encounter A516 Gr 70 on almost every material list. This guide explains what A516 Gr 70 steel is, how it differs from A285 and A537, what the specification requires, and how to write a purchase order that gets the right plate with the right certificates.

1. What Is ASTM A516 Gr 70?

ASTM A516 covers carbon steel plates intended primarily for service in welded pressure vessels where improved notch toughness is important. The standard has four grades: 55, 60, 65, and 70. The number is the minimum tensile strength in ksi. Grade 70 therefore has a minimum tensile strength of 70 ksi (485 MPa) and a minimum yield strength of 38 ksi (260 MPa). It is a killed steel, normally supplied in the as-rolled condition, and can be ordered normalized or stress relieved when required by design temperature or code.

Grade 70 is the most popular grade because it provides the highest strength in the A516 family while remaining weldable and economical.

It is ASME-approved as SA-516 Gr 70. The ASME and ASTM compositions and properties are identical; the difference is the certification and marking required by the ASME Boiler and Pressure Vessel Code.

Thickness range: commonly supplied from 6 mm to 150 mm, with heavier gauges available to order.

Typical applications: pressure vessels, storage tanks, boilers, heat exchangers, process columns, and LNG equipment.

2. Chemical Composition

Element	A516 Gr 70 max (%)
Carbon	0.27 (thickness dependent, often 0.20 max by agreement)
Manganese	0.85–1.20
Phosphorus	0.025
Sulfur	0.025
Silicon	0.15–0.40

The low sulfur and phosphorus limits are what distinguish A516 from ordinary structural grades. They keep the steel clean, reduce lamellar tearing in restrained welds, and improve toughness. Carbon is controlled to improve weldability; many buyers add a supplementary requirement to limit carbon to 0.20% maximum when impact testing is required or when welding thick plates. Manganese is intentionally set in the 0.85–1.20% range to provide strength without excessive carbon.

3. Mechanical Properties and Temperature Limits

Property	A516 Gr 70
Tensile strength	70–90 ksi (485–620 MPa)
Yield strength, min	38 ksi (260 MPa)
Elongation in 8 in., min	17%
Elongation in 2 in., min	21%
Maximum design temperature	See ASME Section II Part D; commonly 425–450°C depending on thickness
Minimum design temperature	Depends on impact test exemption curves or specified Charpy testing

The maximum allowable design stress decreases with temperature. At room temperature, A516 Gr 70 is a strong, ductile plate; above about 400°C, its strength drops quickly and designers usually switch to chrome-moly grades such as A387. At low temperatures, toughness becomes the governing factor. ASME provides impact-test exemption curves based on thickness and minimum design metal temperature; if the combination falls outside the exemption, you must specify Charpy V-notch impact testing, usually at the design temperature or colder.

4. As-Rolled vs Normalized Condition

A516 Gr 70 can be supplied as-rolled or normalized. As-rolled plate is cheaper and faster to produce. Normalized plate is reheated to the austenitizing temperature and air-cooled, which refines the grain size and improves toughness — especially important for low-temperature service or thick sections. Many ASME designs require normalized material because the exemption curves are more favorable and the Charpy values are higher.

As-rolled A516 Gr 70: suitable for ambient-temperature vessels, thinner sections, and applications where toughness requirements are modest.

Normalized A516 Gr 70: required for low-temperature service, thick sections, or when the design code specifies normalized plate. Add “normalized” explicitly on the PO.

Stress relief: some fabricators specify post-weld heat treatment (PWHT) or stress relieving to reduce residual stress in thick, restrained welds.

5. Weldability and Fabrication

A516 Gr 70 is widely regarded as one of the most weldable pressure-vessel grades. Carbon equivalent is typically 0.40–0.50, so preheat is not always required for thin plate but becomes advisable above about 25 mm or in high-restraint joints. Common welding processes include SMAW with E7018 electrodes, SAW with EM12K/OK Flux, and GMAW/FCAW with appropriate filler metals. PWHT is often performed on thick sections to restore toughness in the heat-affected zone.

Forming and bending are straightforward in the as-rolled and normalized conditions. Cold bending should use generous bend radii, typically 2–3 times plate thickness, to avoid surface cracking. Hot forming can be performed in the 900–1100°C range, but the plate must be re-normalized afterward if the mechanical properties are to be guaranteed. Always record hot-forming temperatures and any subsequent heat treatment on the material traceability record.

6. Comparison With A285 and A537

Grade	Yield, min	Tensile	Toughness	Best for
A285 Gr C	30 ksi (205 MPa)	55–75 ksi	Basic	Low-pressure tanks, boilers
A516 Gr 70	38 ksi (260 MPa)	70–90 ksi	Good to excellent with impact test	Pressure vessels, separators, columns
A537 Class 1	50 ksi (345 MPa)	70–90 ksi	Good	Higher-strength pressure vessels
A537 Class 2	60 ksi (415 MPa)	80–100 ksi	Excellent	High-strength, low-temperature vessels

A516 Gr 70 sits in the sweet spot for most pressure-vessel work. It is stronger than A285, cheaper and easier to weld than A537, and has excellent code acceptance. A537 is used when higher strength is needed at low weight, but its weldability and toughness requirements are more demanding.

7. Testing and Certification Requirements

Every A516 Gr 70 plate must be tested for tensile properties and must pass a standardized impact test if ordered to supplementary requirements. The most common additional tests are Charpy V-notch impact testing, ultrasonic examination, and through-thickness tension testing. Certificates should be EN 10204 3.1 for normal commercial work or 3.2 when an independent inspector witnesses testing. ASME code projects require the plate to be certified to SA-516 with the proper data report.

Tensile test: one per heat, per thickness range, per 50 t lot.

Charpy impact: supplementary requirement S5; specify test temperature and minimum energy.

Ultrasonic test: supplementary requirement S1, usually to ASTM A578 Level B or C.

Through-thickness test: supplementary requirement S3 for plates subject to through-thickness tension.

Chemical analysis: heat analysis and product analysis reports.

Is A516 Gr 70 the same as SA-516 Gr 70?

Yes, the material is the same. SA-516 is the ASME designation, and the properties are identical to ASTM A516. The difference is the certification: SA-516 material must be produced under an ASME quality system, marked with the ASME specification, and supplied with the appropriate data report for code stamping.

When should I specify normalized A516 Gr 70?

Specify normalized plate when the design temperature is low, the section is thick, or the code requires it. Normalization improves toughness and refines grain structure, which makes it easier to meet Charpy impact requirements. It adds roughly 5–10% to the base price and a few days to delivery.

Can A516 Gr 70 be used above 450°C?

Not for code-stamped pressure vessels above the temperature limits in ASME Section II Part D. For sustained service above 425–450°C, designers typically select chrome-moly grades such as A387 Gr 11 or Gr 22, which retain strength and resist creep at elevated temperature.

What is the typical lead time from China?

Common gauges of A516 Gr 70 are often stocked in Chinese service centers and can ship within 2–3 weeks. Non-standard thicknesses, normalized plate, or plates with supplementary testing usually require 4–8 weeks rolling and testing time. Always confirm mill order minimums, which are typically 20–50 t per size.

8. Purchase Order Checklist for A516 Gr 70 Plate

Grade and condition: “ASTM A516 Gr 70, as-rolled” or “SA-516 Gr 70, normalized”.

Dimensions and tolerance: thickness, width, length, edge condition, flatness per ASTM A6.

Supplementary requirements: impact testing, ultrasonic examination, through-thickness testing, restricted chemistry.

Certification: EN 10204 3.1 or 3.2; ASME data report for code work.

Marking and traceability: heat number, plate number, specification, and condition stamp.

Surface and protection: shot-blasted, oiled, or primed; edge preservation.

Inspection witness: agree on third-party inspection scope and hold points.