What ASTM A299 Grade B Plate Is
ASTM A299 Grade B is a carbon manganese steel plate intended for welded boilers and other pressure vessels, and it appears in the ASME code system as SA299 Grade B. The grade is specified by ASTM A299/A299M, which covers two strength levels: Grade A and Grade B. Grade B is the higher strength of the two, with a minimum yield strength of about 325 MPa and a tensile strength range of 550 MPa to 690 MPa, while Grade A is defined by a minimum yield strength of about 290 MPa and a tensile strength range of 515 MPa to 655 MPa.
Because these plates operate in boiler drums, headers and pressure containing shells, the specification does not stop at tensile properties. Additional requirements are frequently invoked on top of the base grade, including simulated post weld heat treatment, low temperature impact testing, drop weight testing and elevated temperature tensile testing. Ultrasonic examination of the plate is also carried out during rolling, so that internal discontinuities can be detected before the material is formed into a pressure retaining component.
Supply Range and Delivery Condition
| Item | Range |
|---|---|
| Steel standard | ASTM A299 / A299M, ASME SA299 |
| Product type | Boiler steel plate, pressure vessel steel plate |
| Thickness | 6 mm to 300 mm |
| Width | 1500 mm to 4200 mm |
| Length | 3000 mm to 18000 mm |
| Delivery condition | As rolled, stress relieved or normalized |
Normalizing is specified when the design requires a uniform ferrite and pearlite structure with predictable toughness, while stress relieving is used to reduce residual stresses after forming or welding. The delivery condition is agreed at the order stage because it determines the heat treatment cycle and the test results reported on the mill certificate.
Chemical Composition
| Element | A299 Grade B, % |
|---|---|
| Carbon, C | 0.28 - 0.30 |
| Silicon, Si | 0.13 - 0.45 |
| Manganese, Mn | 0.84 - 1.62 |
| Phosphorus, P | 0.035 max |
| Sulphur, S | 0.035 max |
| Molybdenum, Mo | Not specified for this grade |
The carbon content is held in a narrow band and the manganese range is deliberately wide, so the steelmaker can balance strength and toughness for a specific thickness. Phosphorus and sulphur are capped at 0.035 % each to limit embrittlement and to support good weldability in thick sections.
Mechanical Properties
| Thickness | Yield strength, min (MPa) | Tensile strength (MPa) | Elongation, min (%) |
|---|---|---|---|
| Up to and including 50 mm | 310 - 325 | 550 - 690 | 19 |
| Over 50 mm up to 200 mm | 310 - 325 | 550 - 690 | 19 |
Grade B holds the same strength and ductility requirements across both thickness bands, which makes the grade convenient for fabrication where plate thickness changes between components. The minimum elongation of 19 % provides enough ductility for cold forming of shells and for the strain that occurs around welded nozzles.
Grade A Compared With Grade B
| Property | A299 Grade A | A299 Grade B |
|---|---|---|
| Minimum yield strength | 290 MPa | 325 MPa |
| Tensile strength | 515 - 655 MPa | 550 - 690 MPa |
| Elongation, min | 19 % | 19 % |
Both grades share the same chemistry family and the same fabrication behaviour, so the choice between them is normally driven by the wall thickness calculation of the pressure vessel. Where a higher allowable stress is needed, Grade B allows a thinner wall for the same design pressure.
Testing and Quality Control
Ultrasonic examination of the plate is carried out during rolling and can be supplied to the acceptance level agreed with the purchaser.
Simulated post weld heat treatment testing confirms that properties survive the heat cycle the finished vessel will see.
Low temperature impact testing and drop weight testing are used where brittle fracture resistance has to be demonstrated.
Elevated temperature tensile testing supports designs where the equipment operates above ambient temperature.
Tensile and elongation results are reported from test specimens taken in the direction and position required by the product specification.
Fabrication Notes
A299 Grade B is a fully weldable carbon manganese plate, and the usual shop rules apply: clean joint faces, matched consumables, controlled preheat for thick sections and a documented welding procedure qualified to the applicable code. Cold forming of shells is normally done with bend radii that keep surface strain within the limits agreed with the plate supplier, and any flame cut edge is dressed before welding to remove a hardened layer. Where components are stress relieved after welding, the heat treatment cycle should be recorded and, for critical equipment, supported by simulated heat treatment test data on the plate itself.
Typical Applications
Boiler drums and shells for power generation and industrial steam systems
Pressure vessel shells, heads and transition sections
Headers, collectors and large diameter pressure piping
Storage and process vessels in the petroleum and chemical industries
Heavy duty welded structures requiring a combination of strength and toughness
Frequently Asked Questions
Q: What is the difference between ASTM A299 Grade A and Grade B?
Grade B has the higher strength level, with a minimum yield strength of about 325 MPa and a tensile range of 550 MPa to 690 MPa, compared with about 290 MPa and 515 MPa to 655 MPa for Grade A. Both keep a minimum elongation of 19 %.
Q: Is A299 Grade B the same as SA299 Grade B?
SA299 Grade B is the ASME designation for the same plate used in code stamped pressure equipment. The chemistry, mechanical properties and test requirements follow the same specification family, with any additional code rules applied on top.
Q: What thickness range is normally supplied?
Plates are commonly produced from 6 mm up to 300 mm, with widths from about 1500 mm to 4200 mm and lengths from 3000 mm to 18000 mm, cut to the sizes required by the vessel drawing.
Q: Why is ultrasonic testing requested for this grade?
Boiler and pressure vessel plates carry the full design pressure, so internal laminations or inclusions that could act as initiation sites in service are unacceptable. Ultrasonic examination during rolling screens the plate for such discontinuities.
Q: Which delivery condition should be ordered?
Normalized plate is chosen when uniform structure and predictable toughness are needed, stress relieved plate when residual stresses must be reduced, and as rolled plate for less demanding duties. The choice should match the design code and the fabrication sequence.
Q: Can extra tests be added to the order?
Yes. Simulated post weld heat treatment, low temperature impact, drop weight and elevated temperature tension tests are all routinely added as supplemental requirements when the service condition or the design code calls for them.
