ASTM A193 Grade B7M 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 B7M is a standard material specification for chromium-molybdenum alloy steel fasteners for use in high tensile, high temperature and special purpose applications. Grade B7M is a heat-treated chromium-molybdenum alloy steel with minimum tensile requirement of 100 ksi, yield of 75 ksi and maximum hardness of 99 HRB. ASTM A193 specification covers requirements for chemical composition, mechanical properties, hardness, heat-treatment, recommended nuts-washrs for Grade B7M fasteners. The difference between B7 & B7M is the hardness testing requirement for each bolt from a given lot in the latter.

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. For the B7M grade, a minimum carbon content of 0.28 % is permitted, provided that the required tensile properties are met in the section sizes involved; the use of AISI 4130 or 4130H is allowed.

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
						4 and under	100	80	18	50	235 HBW or 99 HRB
					over 4 to 7, inclusive	100	75	18	50	235 HBW or 99 HRB

Note: To meet the tensile requirements, the Brinell hardness shall be over 200 HBW (93 HRB).
Heat Treatment: Quenched & Tempered at 1100º F minimum.