ASTM A645 / A645M

This specification covers specially heat treated 5 % and 5 1⁄2 % nickel alloy steel plates intended primarily for welded pressure vessels for service at low or cryogenic temperatures. The maximum thickness of plates which can be supplied under this specification is limited only by the capacity of the material to meet the specified requirements. This material is susceptible to magnetization. Use of magnets in handling after heat treatment should be avoided if residual magnetism would be detrimental to subsequent fabrication or service.

Chemical Properties

Grades	Carbon, max	Manganese	Phosphorus, max	Sulfur, max	Silicon	Nickel	Chromium	Molybdenum	Aluminum, total	Nitrogen, max
Grade A	0.15	0.25-0.66	0.025	0.025	0.18–0.45	4.7–5.3	-	0.17–0.38	0.01–0.16	0.025
Grade B	0.13	0.84–1.59	0.025	0.015	0.13–0.33A	4.9–6.1	0.06–1.05	0.09–0.33	0.015–0.06	0.010

Note A: The specified minimum limit does not apply if the total aluminum is 0.030 % or more, ore if the acid soluble aluminum content is 0.025 % or more.

Mechanical Properties

Grades	Yield strength, min, ksi [MPa]A	Tensile strength, ksi [MPa]	Elongation in 2 in. [50 mm], min, %B
Grade A	65 [450]	95-115 [655-795]	20.0
Grade B	85 [590]	100-120[690-830]	20

Note A: At 0.2 % offset, or, if agreed between the purchaser and the manufacturer, at 0.5 Note B: % extension under load.

Products