ASTM A194 Grade 4 Specification

ASTM A194 Grade 4 Specification for high tensile nuts and other internally threaded fasteners, made from heat treated carbon molybdenum steel.

ASTM A194 Grade 4 is a standard material specification for high tensile nuts and other internally threaded fasteners, made from carbon molybdenum steel. Grade 4 nuts can be produced by means of hot forging, cold forging or machining from bar stock followed by heat treatment. ASTM A194 specification covers requirements for chemical composition, heat treatment, hardness, proof load, etc., for Grade 4 nuts.

Chemical Composition


Element
Carbon Molybdenum Steel
CompositionA, %
Carbon 0.40 - 0.50
Manganese 0.70 - 0.90
Phosphorus 0.035 max
Sulfur 0.040 max
Silicon 0.15 - 0.35
Molybdenum 0.20 - 0.30

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
4 248 - 327 24 - 35 ... 201 94

Heat Treatment: Grade 4 shall be quenched and tempered at a temperature of at least 1050 °F [565 °C].

Proof Load

Nominal Size, Inch. Threads Per Inch Proof Load, lbf
Heavy HexA HexB
1/4 20 5 570 4 770
5/16 18 9 170 7 860
3/8 16 13 560 11 620
7/16 14 18 600 15 940
1/2 13 24 830 21 280
9/16 12 31 850 27 300
5/8 11 39 550 33 900
3/4 10 58 450 50 100
7/8 09 80 850 69 300
01 08 106 000 90 900
1-1/8 08 138 200 118 500
1-1/4 08 175 000 150 000
1-3/8 08 215 800 185 000
1-1/2 08 261 100 223 800

A: Based on proof stress of 175 000 psi.
B: Based on proof stress of 150 000 psi.

Nuts

Commonly Produced Grade 4 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