ASTM A193 Grade B7 Specification for high tensile bolts, screws, stud bolts, threaded rods, anchor bolts and other externally threaded fasteners, made from chromium-molybdenum alloy steel.

ASTM A193 Grade B7 is a standard material specification for chromium-molybdenum alloy steel fasteners for use in high tensile, high temperature and special purpose applications. Grade B7 is a heat-treated chromium-molybdenum alloy steel with minimum tensile requirement of 100 ksi, yield of 75 ksi and maximum hardness of 35 HRC. ASTM A193 specification covers requirements for chemical composition, mechanical properties, hardness, heat-treatment, recommended nuts-washers for Grade B7 fasteners. ASTM A193 Grade B7 is the most widely fastener specifications, commonly found in bolting or piping, pressure vessels, valves, flanges and fittings.

Chemical Composition

Element	Alloy Steel
	Chromium Molybdenum SteelA
	CompositionB, %
Carbon	0.37 - 0.49C
Manganese	0.65 - 1.10
Phosphorus	0.035 max
Sulfur	0.040 max
Silicon	0.15 - 0.35
Chromium	0.75 - 1.20
Molybdenum	0.15 - 0.25

A: Typical steel compositions used for this grade include 4140, 4142, 4145, 4140H, 4142H, and 4145H.
B: The intentional addition of Bi, Se, Te, and Pb is not permitted.
C: For bar sizes over 31⁄2 in. [90 mm], inclusive, the carbon content may be 0.50 %, max.

Mechanical Properties

Diameter, inch.	Tensile Strength, min, ksi	Yield Strength, min, 0.2% offset, ksi	Elongation in 4D, min, %	Reduction of Area, min, %	Hardness, max
						2-1⁄2 and under	125	105	16	50	321 HBW or 35 HRC
					over 2-1⁄2 to 4, inclusive	115	95	16	50	321 HBW or 35 HRC
over 4 to 7, inclusive	100	75	18	50	321 HBW or 35 HRC

Heat Treatment: Quenched & Tempered at 1100º F minimum.