1.1 This specification covers heat-treated carbon-manganese-silicon steel plates intended for fusion welded pressure vessels and structures.

1.2 Material under this specification is available in the following three classes:

			Yield	Tensile
			Strength,	Strength,
	Heat	Thickness,	min, ksi	min, ksi
Class	Treatment		[MPa]	[MPa]
1	Normalized	21/2 in. and under[65 mm and under]	50 [345]	70 [485]
		Over 21/2 to 4 in.[Over 65 to 100 mm]	45[310]	65[450]
2	Quenched and tempered	21/2 in. and under[65 mm and under]	60 [415]	80 [550]
		Over 21/2 to 4 in.[Over 65 to 100 mm]	55[380]	75[515]
		Over 4 to 6 in.[Over 100 to 150 mm]	46[315]	70[485]
3	Quenched and tempered	21/2 in. and under[65 mm and under]	55 [380]	80 [550]
		Over 21/2 to 4 in.[Over 65 to 100 mm]	50[345]	75[515]
		Over 4 to 6 in.[Over 100 to 150 mm]	40[275]	70[485]

1.3 The maximum thickness of plates furnished under this specification is 4 in. [100 mm] for Class 1 and 6 in. [150 mm] for Class 2 and Class 3.

1.4 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.