ASTM F594

ASTM F594 covers the chemical and mechanical requirements for stainless steel nuts in sizes from 1/4" to 1-1/2", designed for use with ASTM F593 fasteners.

These nuts are intended for general-purpose applications and are available in seven alloy groups.

The most commonly used grades are highlighted for easy reference, while several less common grades also exist under this standard.

The mechanical properties table is usually limited to Alloy Groups 1 and 2, as they are the most widely used.

The chemical composition table generally shows the most common alloy grades for their respective groups.

ASTM F594 — Stainless Steel Alloy Groups (summary)

Group	Typical Grades Included	Stainless Steel Type	Key Characteristics
1	303, 304, 304L, 305, 384, XM1, 18-9LW, 302HQ, 303Se	Austenitic (300-series)	Good corrosion resistance, generally non-magnetic, widely used for general-purpose fasteners.
2	316, 316L	Austenitic (marine-grade)	Better resistance to chlorides and corrosive environments — ideal for marine and chemical service.
3	321, 347	Stabilized Austenitic	Stabilized against carbide precipitation — good for elevated-temperature applications.
4	430, 430F	Ferritic	Magnetic stainless with fair corrosion resistance; often used in decorative or structural parts.
5	410, 416, 416Se	Martensitic	Hardenable grades offering higher strength; suitable for applications requiring wear resistance.
6	431	Martensitic (high-strength)	Higher toughness and strength than basic martensitic grades; used where extra strength is needed.
7	630 (17-4PH)	Precipitation Hardening	Combines high strength with good corrosion resistance — used in high-performance fasteners.

F594 Mechanical Properties / Condition:

Alloy Group	Condition	Marking	Diameter Range	Proof Stress, Hex Nuts (ksi)	Proof Stress, Heavy Hex Nuts (ksi)	Rockwell Hardness
1	AF	F594A	1/4 to 1-1/2	70	76	B85 max
	A	F594B	1/4 to 1-1/2	75	81	B65 to 95
	CW1	F594C	1/4 to 5/8	100	108	B95 to C32
	CW2	F594D	3/4 to 1-1/2	85	92	B80 to C32
2	AF	F594E	1/4 to 1-1/2	70	76	B85 max
	A	F594F	1/4 to 1-1/2	75	81	B65 to 95
	CW1	F594G	1/4 to 5/8	100	108	B95 to C32
	CW2	F594H	3/4 to 1-1/2	85	92	B80 to C32

F594 Chemical Requirements:

Element (Max unless shown)	Alloy Group 1 Type 304	Alloy Group 2 Type 316
Carbon	0.08%	0.08%
Manganese	2.00%	2.00%
Phosphorus	0.045%	0.045%
Sulfur	0.030%	0.030%
Silicon	1.00%	1.00%
Chromium	18.0 – 20.0%	16.0 – 18.0%
Nickel	8.0 – 10.5%	10.0 – 14.0%
Copper	1.00%	–
Molybdenum	–	2.00 – 3.00%