ASTM A193 Grade B7 Specification

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ASTM A193 Grade B7 Specification for high tensile bolts, screws, stud bolts, anchor bolts, threaded rods and other externally threaded fasteners, made from 5% chromium-ferritic steel.

ASTM A193 Grade B7 is a standard material specification for low alloy chromium-ferritic steel fasteners, for use in high tensile, high temperature and special purpose applications such as pressure piping & pressure vessels bolting. Grade B7 is a heat-treated 5% chromium-ferritic magnetic stainless steel with minimum tensile strength requirement of 100 ksi and yield 80 ksi. ASTM A193 specification covers requirements for chemical composition, mechanical properties, hardness, heat-treatment and recommended nuts-washers for Grade B7 Fasteners.

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.

Recommended Nuts & Washers

Nut Specification Washer Specification
ASTM A194 Grade 2H OR ASTM A194 Grade 2HM ASTM F436

Fasteners

Commonly Produced B7 Fasteners
Hex Bolts Heavy Hex Bolts Stud Bolts Hex Screws Anchor Bolts
Eye Bolts Socket Head Cap Screws Countersunk Screws U Bolts Square Head Bolts