Grade 3

ASTM A194 Grade 3 Specification for high tensile nuts and other internally threaded fasteners, made from heat treated ferritic stainless steel grade AISI 501. ASTM A194 Grade 3 is a standard material specification for high tensile nuts and other internally threaded fasteners, made from ferritic stainless steel grade AISI 501. Grade 3 nuts can be produced by means of hot forging, cold forging or machining from bar stock (Grade Type AISI 501) followed by heat treatment. ASTM A194 specification covers requirements for chemical composition, heat treatment, hardness, proof load, etc., for Grade 3 nuts.

Chemical Composition

Element	Ferritic Steel
	AISI 501 Stainless Steel
	CompositionA, %
Carbon	0.10 min
Manganese	1.00 max
Phosphorus	0.04 max
Sulfur	0.03 max
Silicon	1.00 max
Chromium	4.00 - 6.00
Molybdenum	0.40 - 0.65

^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
3	248 - 327	24 - 35	...	201	94

Heat Treatment: Grade 3 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 3 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