What Is ASTM A202 Grade B
ASTM A202 Grade B is a chromium-manganese-silicon alloy steel plate specified for welded pressure vessels. The designation follows the ASTM system: "A" identifies a ferrous material, "202" identifies the standard for chromium-manganese-silicon alloy plates for pressure vessels, and "Grade B" is the higher-strength classification within that standard. The grade was once a primary choice for high-strength pressure vessel requirements before the widespread adoption of molybdenum-based alloys and advanced quenching techniques. Today it is mainly encountered during inspection, maintenance, and fitness-for-service evaluation of aging industrial assets.
Price Considerations for A202 Grade B Plates
The price of ASTM A202 Grade B pressure vessel steel plates generally ranges between $700 and $1,200 per ton, depending on order volume and supplier. Bulk purchases of 100 tons or more can lower the cost to around $800 per ton, while smaller orders of about 10 tons may be closer to $1,000 per ton. Actual prices vary with market conditions, plate thickness, delivery terms, and testing requirements, so buyers should obtain current pricing from suppliers and treat published ranges as indicative only.
Chemical Composition and Mechanical Properties
The primary chemical composition of ASTM A202 Grade B is: carbon 0.25% maximum, silicon 0.54–0.96%, manganese 0.97–1.52%, chromium 0.31–0.64%, and phosphorus and sulfur each 0.035% maximum. These elements provide the strength and thermal resistance required for moderate-temperature pressure service while keeping the plate weldable with appropriate precautions.
According to the specification table, ASTM A202 Grade B provides a tensile strength of 85–110 ksi (585–760 MPa) and a minimum yield strength of 47 ksi (325 MPa). Minimum elongation is 15% over a 200 mm gauge length and 18% over a 50 mm gauge length. This combination of strength and ductility allows the material to endure the mechanical stresses encountered in high-pressure environments.
Typical Applications
A202 Grade B is found in legacy refinery vessels such as older distilling columns and separators, steam boiler casings that form the high-pressure boundary of older utility boilers, historical chemical reactors in older manufacturing plants, marine steam drums on vintage steam-powered ships, and deaerator tanks in long-service thermal power stations. Its typical service limit is regarded as approximately 800°F (427°C), so design temperatures should be checked against the governing pressure vessel code before use.
Welding and Fabrication
A202 Grade B has good weldability and can be welded using shielded metal arc welding (SMAW), gas tungsten arc welding (GTAW), and submerged arc welding (SAW). Because of its higher alloy and carbon content, preheating and post-weld heat treatment (PWHT) are recommended to avoid cracking and to ensure the integrity of welded joints, especially for thicker sections in pressure vessel fabrication.
Frequently Asked Questions
What is the tensile strength of ASTM A202 Grade B? The tensile strength is 85–110 ksi (585–760 MPa) per the specification table, allowing the material to withstand the mechanical stresses of high-pressure service.
What is the yield strength of ASTM A202 Grade B? The minimum yield strength is 47 ksi (325 MPa), which means the material can withstand stresses up to this level without permanent deformation.
What is the chemical composition of ASTM A202 Grade B? Carbon is limited to 0.25% maximum, silicon is 0.54–0.96%, manganese is 0.97–1.52%, chromium is 0.31–0.64%, and phosphorus and sulfur are each limited to 0.035%.
Is ASTM A202 Grade B weldable? Yes. It can be welded with SMAW, GTAW, and SAW, but preheating and post-weld heat treatment are recommended due to its higher carbon and alloy content, particularly for thick sections.
What is the hardness of ASTM A202 Grade B? Hardness typically falls between 190 and 250 HB depending on heat treatment and processing, though this range should be verified against the mill certificate for the specific plate.
What is the maximum temperature limit for ASTM A202 Grade B? The alloy is commonly regarded as suitable up to approximately 800°F (427°C). For design purposes the allowable stress values from the applicable pressure vessel code must be used.
Which industries use ASTM A202 Grade B? Power generation, chemical processing, and petrochemical industries use the grade in pressure vessels, heat exchangers, and boilers where strength and thermal resistance are required at moderate temperatures.
