What ASTM A516 Covers
ASTM A516 is the specification for carbon steel plates intended for use in welded boilers and pressure vessels in low and moderate temperature service. It contains four grades, 55, 60, 65 and 70, whose tensile designations are 380, 415, 450 and 485 in the metric companion, and the grade number corresponds to the specified minimum tensile strength in ksi. All grades are produced to a fine-grain practice and are normally supplied in the normalized condition, with improved notch toughness being the characteristic that distinguishes the specification from general structural plate. Grade 70 is the most widely traded of the four because it offers the highest strength of the group while retaining adequate toughness for most pressure equipment.
Composition Requirements for Grade 70
| Element | Limit | Note |
|---|---|---|
| Carbon | 0.27 % max up to 12.5 mm; 0.28 % max 12.5 to 50 mm; 0.30 % max 50 to 100 mm; 0.31 % max over 100 mm | Heat analysis |
| Manganese | 0.85 to 1.20 % | Heat analysis, all thicknesses |
| Phosphorus | 0.035 % max | Heat analysis |
| Sulphur | 0.035 % max | Heat analysis |
| Silicon | 0.15 to 0.40 % | Heat analysis |
The carbon limit rises with thickness because heavier plate requires more carbon to reach the specified strength after normalizing, while the manganese range is held almost constant so that toughness does not fall away in thick sections. Product analysis tolerances are slightly wider than the heat analysis limits shown here.
Mechanical Properties and Allowable Stress
Grade 70 is specified with a minimum yield strength of 260 MPa, equivalent to 38 ksi, and a tensile range of 485 MPa to 620 MPa, equivalent to 70 ksi to 90 ksi. Minimum elongation is 21 % for thicknesses up to 50 mm and 19 % for heavier plate. Where impact testing is required it is ordered as a supplementary requirement at a stated test temperature, and normalizing is the usual route to meeting low-temperature toughness. For design, the ASME Boiler and Pressure Vessel Code lists an allowable stress of about 138 MPa at room temperature for SA-516 Grade 70, falling to roughly 130 MPa at 650 degrees Fahrenheit and about 102 MPa at 750 degrees Fahrenheit, so the usable design stress at elevated temperature is substantially lower than the room-temperature value.
Cross-Reference to Other Standards
| System | Grade | Minimum yield | Tensile range |
|---|---|---|---|
| ASME | SA-516 Grade 70 | 260 MPa | 485 to 620 MPa |
| EN 10028-2 | P355GH | 355 MPa | 510 to 650 MPa |
| GB/T 713 | Q345R | 345 MPa | 510 to 640 MPa |
| JIS G3115 | SPV355 | 355 MPa | 520 to 640 MPa |
| Former DIN 17155 | 19Mn6 | 355 MPa | 490 to 630 MPa |
The ASME designation SA-516 Grade 70 is the same material made to the same requirements as the ASTM specification, and dual certification is routine. The European, Chinese and Japanese grades listed are the nearest matches by strength class, but each has a higher minimum yield and a different tensile band, so they are not drop-in replacements. The correct approach is to compare the design stress, the impact test temperature and the thickness range permitted by the governing code before accepting a substitute.
Selection, Fabrication and Heat Treatment
Grade selection follows the design pressure and temperature: Grade 70 allows the thinnest wall of the four grades for a given pressure, while the lower grades are used where toughness or weldability is the governing requirement or where plate is readily available at a lower cost. A516 plate is welded by all conventional processes, and the low carbon and controlled manganese give a carbon equivalent that permits welding without preheat in moderate thickness under normal shop conditions. Post-weld heat treatment is applied where the design code requires it, and the holding temperature and time must be selected so that the strength achieved by normalizing is not degraded. Cold forming is straightforward for ordinary shell and head geometry, and hot forming is carried out at temperatures that will not coarsen the grain structure.
Inspection and Documentation for Project Supply
Incoming inspection for A516 Grade 70 covers verification of the heat number against the certificate, tensile results, chemical analysis and, where ordered, Charpy impact values at the specified temperature. Ultrasonic examination to ASTM A435 for straight-beam testing, or to ASTM A578 where tested plate for special applications is required, is a common project stipulation, and dimensional checks confirm thickness, flatness and edge condition against the general requirements specification. The plate is normally delivered with a mill test certificate at EN 10204 3.1 or with the equivalent ASTM certificate of analysis, and third-party witness is arranged where the purchaser or the design code requires it. Plates are marked with the grade, heat number and the manufacturer's identification so that the delivered item can be traced back to the certified results.
Frequently Asked Questions
Q: What is ASTM A516 Grade 70 equivalent to?
A: The nearest grades in other systems are EN 10028-2 P355GH, GB/T 713 Q345R, JIS G3115 SPV355 and, historically, DIN 17155 19Mn6. Each of these has a higher minimum yield strength than Grade 70, so substitution requires a design check.
Q: Is SA-516 the same as A516?
A: Yes. SA-516 is the designation used in the ASME Boiler and Pressure Vessel Code for plate made to the ASTM A516 specification, and dual certification to both designations is standard practice.
Q: What is the difference between A516 Grade 60 and Grade 70?
A: The grades differ in specified tensile strength, 415 MPa for Grade 60 against 485 MPa for Grade 70, with correspondingly tighter carbon and manganese control at the higher grade. Grade 70 permits a thinner wall for the same design pressure.
Q: At what temperature is A516 Grade 70 impact tested?
A: Impact testing is a supplementary requirement ordered at a stated temperature. Normalizing is the usual route to meeting low-temperature toughness, and the test temperature is quoted on the purchase order and on the mill certificate.
Q: Can A516 Grade 70 be welded without preheat?
A: For moderate thickness and normal shop conditions, yes. Preheating is applied where thickness, joint restraint or low ambient temperature increases the risk of cracking, in accordance with the welding procedure specification.
Q: What ultrasonic test applies to A516 plate?
A: ASTM A435 covers straight-beam ultrasonic examination of steel plates, and ASTM A578 applies where plate for special applications must be examined. The acceptance level required by the project is stated on the order.
