Difference between SA662 Grade A and Grade B steel plate

SA662 Grade A and Grade B are ASME standard carbon-manganese-silicon steel plates for moderate to low-temperature pressure vessels, differing mainly in their chemical composition (especially carbon/manganese content) and mechanical properties, with Grade B generally having higher strength and toughness for more demanding low-temperature service, though both offer good weldability and toughness for applications like reactors, heat exchangers, and tanks in the oil, chemical, and energy industries.

Supplementary Technology: HIC Test | NACE MR0175 | Z15 | Z25 | Z35 | S1 | S2 | S3 | S4.1
S5 | S6 | S8 | S9| S11 | S12 | S17

Thickness: 6MM to 300MM,

Width: 1500mm to 4050mm,

Length: 3000mm to 15000mm

Chemical Composition

Carbon Equivalent: Ceq = 【C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15】%

Carbon Equivalent: Ceq = 【C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15】%

Mechanical Property

Key Differences & Similarities

Standard: Both fall under ASME SA662/SA662M, for pressure vessel plates.

Material Type: Both are C-Mn (Carbon-Manganese) steels.

Application: Used for boilers, pressure vessels, reactors, tanks, and heat exchangers, especially at moderate to low temperatures.

Grades: SA662 has Grades A, B, C, and D; A and B are common grades.

SA662 Grade A

A carbon-manganese-silicon steel for moderate/low-temp pressure vessels.

Often requires normalization heat treatment for thickness.

Good low-temperature toughness and weldability.

SA662 Grade B

Also C-Mn steel for middle to low-temperature pressure vessels.

Generally offers higher strength and impact resistance compared to Grade A.

Used in reactors, tanks, etc., in chemical, petroleum, and power industries.

In Simple Terms: Think of them as different strengths/toughness levels within the same family of steels, with Grade B being the stronger option for colder or higher-pressure applications than Grade A, though both excel in low-temperature service.