ASTM A516 Grade 70 is a robust, pressure vessel quality (PVQ) carbon steel plate designed for moderate to lower-temperature service, known for its strength, weldability, and notch toughness, making it ideal for boilers, storage tanks, and chemical processing equipment. It offers higher strength than other A516 grades (like 55, 60, 65) with a tensile strength of 70-90 ksi (485-620 MPa).
Mechanical Properties of ASTM A516 Grade 70
| Description | Grade 70 |
|---|---|
| Tensile strength (ksi) | 70-90 |
| Tensile strength (MPa) | 485-620 |
| Yield strength (ksi) | 38 |
| Yield strength (MPa) | 260 |
| Elongation in 200mm (min)(%) | 17 |
| Elongation in 50mm (min) (%) | 21 |
| Thickness (max)(mm) | 205 |
Material Chemistry
|
C |
MN |
P |
SI |
S |
|
0.27 – 0.31% |
1 – 1.7% |
0.025% |
0.15 – 0.40% |
0.025% |
Key Characteristics
Toughness: Excellent notch toughness, especially important for low-to-moderate temperature service.
Weldability: Readily weldable, requiring certified operators for some applications.
Grades: Available in several grades (55, 60, 65, 70), with Grade 70 being the strongest and most common PVQ choice.
Form: Typically supplied as steel plate.
Material: Carbon steel alloy.
Application: Welded pressure vessels, boilers, storage tanks (oil, gas, petrochemical).
Strength:
High tensile strength (70-90 ksi or 485-620 MPa) and good yield strength (38 ksi minimum)
Common Uses
Oil & Gas: Storage tanks, pressure vessels, reactors.
Power Generation: Boilers, heat exchangers, condenser shells.
Construction: Structural components, bridges, large pipes, and tanks.
key processing methods
1. Cutting
Methods: Oxygen-fuel gas cutting (most common for thick plates), Plasma cutting, Laser cutting, and Mechanical shearing.
Tip: Preheat may be required for very thick plates to prevent edge cracking.
2. Forming (Cold & Hot)
Cold Forming: Suitable for thinner plates. Recommended minimum bend radius is 3x to 5x the thickness to avoid surface cracking.
Hot Forming: Used for thick sections or complex shapes. Typically performed at temperatures between 900°C and 1100°C.
3. Welding
Weldability: Excellent. Compatible with SMAW, GMAW (MIG), GTAW (TIG), and SAW.
Consumables: Use low-hydrogen electrodes such as E7018 or filler wires like ER70S-6.
Preheat: Often required based on thickness (typically if thickness exceeds 38mm/1.5in).
4. Heat Treatment
Normalizing: Required for plates thicker than 40mm (1.5in) to refine grain structure and improve low-temperature notch toughness.
Post-Weld Heat Treatment (PWHT): Generally performed at ~600°C - 650°C to relieve residual stresses after welding.
5. Machining
Machinability: Rated at approx. 60% of B1112.
Characteristics: Fairly easy to machine, but prone to "gumminess." Use high-speed steel or carbide tools with proper lubrication.
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What is the difference between normalized and as-rolled ASTM A516 GR 70?
Normalized plates are heated above critical temp and air-cooled, boosting toughness and structure uniformity. As-rolled ones undergo no post-rolling heat treatment, suitable for less demanding low-pressure applications.
Can ASTM A516 GR 70 be painted or coated?
Yes, it accepts most industrial paints and coatings. Proper surface preparation (grinding, sandblasting) removes rust and contaminants, ensuring coating adhesion and enhancing corrosion resistance in mild environments.
What is the coefficient of thermal expansion of ASTM A516 GR 70?
Its average thermal expansion coefficient is 11.7 × 10⁻⁶/°C (6.5 × 10⁻⁶/°F) between 20-100°C, a key parameter for designing equipment exposed to temperature fluctuations to avoid thermal stress.
Does ASTM A516 GR 70 comply with ASME standards?
Yes, it fully complies with ASME BPVC Section II Part A, making it approved for pressure vessels, boilers, and related equipment designed per ASME codes worldwide.
What is the fatigue strength of ASTM A516 GR 70?
Its fatigue strength is around 25-30 ksi (172-207 MPa) for 10⁷ cycles. It varies with surface finish, welding quality, and service conditions, requiring fatigue analysis for cyclic load applications.
How to store ASTM A516 GR 70 plates properly?
Store in a dry, well-ventilated area, elevated from the ground to prevent moisture. Cover with waterproof sheets to avoid rusting; separate by thickness/grade to prevent damage and mix-ups.
Can ASTM A516 GR 70 be used in cryogenic applications?
At 20°C (68°F), its thermal conductivity is about 48 W/(m·K) (27.7 Btu/(ft·h·°F)), enabling efficient heat transfer, which is crucial for boiler and heat exchanger applications.
Are there any restrictions on the width and length of ASTM A516 GR 70 plates?
No fixed standard restrictions, but common widths are 1500-4000 mm and lengths 6000-12000 mm. Custom sizes are available via mills, subject to production feasibility and thickness.
How does welding consumable selection affect ASTM A516 GR 70 welds?
Choose low-hydrogen consumables (E7018, ER70S-6) to avoid weld cracking. Consumables must match the steel's strength and toughness, ensuring welds meet the same performance as the base metal.