ASTM A194 Grade 7M Specification

ASTM A194 Grade 7M Specification for high tensile nuts and other internally threaded fasteners, made from heat treated chromium molybdenum alloy steel.

ASTM A194 Grade 7M is a standard material specification for high tensile nuts and other internally threaded fasteners, made from chromium molybdenum alloy steel. Grade 7M nuts can be produced by means of hot forging, cold forging or machining from bar stock (Grade Type AISI 4140/4142/4145/4140H/4142H/4145H) followed by heat treatment. ASTM A194 specification covers requirements for chemical composition, heat treatment, hardness, proof load, etc., for Grade 7M nuts.

Chemical Composition


Element
Alloy Steel
Chromium Molybdenum Steel
CompositionA, %
Carbon 0.37 - 0.49
Manganese 0.65 - 1.10
Phosphorus 0.035 max
Sulfur 0.04 max
Silicon 0.15 - 0.35
Chromium 0.75 - 1.20
Molybdenum 0.15 - 0.25

AThe intentional addition of Bi, Se, Te, and Pb is not permitted.

Hardness

Grade Completed Nuts Sample Nut After Heat Treatment
Brinell Hardness,
BHN
Rockwell Hardness Brinell Hardness,
BHN, min
Rockwell Hardness,
HRB, min
HRC HRB
7M 159 - 235 ... 84 - 99 159 84

Heat Treatment: Grade 7M shall be quenched and tempered at a temperature of at least 1150 °F [620 °C].

Proof Load

Nominal Size, Inch. Threads Per Inch Proof Load, lbf
Heavy HexA HexB
1/4 20 4 770 4 300
5/16 18 7 860 7 070
3/8 16 11 620 10 460
7/16 14 15 940 14 350
1/2 13 21 280 19 160
9/16 12 27 300 24 570
5/8 11 33 900 30 510
3/4 10 50 100 45 090
7/8 09 69 300 62 370
01 08 90 900 81 810
1-1/8 08 118 500 106 700
1-1/4 08 150 000 135 000
1-3/8 08 185 000 166 500
1-1/2 08 223 800 201 400

A: Based on proof stress of 150 000 psi.
B: Based on proof stress of 135 000 psi.

Nuts

Commonly Produced Grade 7M Nuts
Hex Nuts Heavy Hex Nuts Jam Nuts Heavy Hex Jam Nuts Castle Nuts
Coupling Nuts Square Nuts Thin Square Nuts All Metal Lock Nuts Dome Nuts