ASTM A194

ASTM A194 nuts are manufactured from carbon, alloy, and stainless steel for use in high-pressure and high-temperature applications. These nuts follow ANSI B18.2.2 Heavy Hex dimensions with Class 2B thread fit. Grade 2H nuts are the most common type, widely used for their strength and often substituted for ASTM A563 DH nuts. Available in multiple sizes and finishes, ASTM A194 nuts are ideal for critical industrial applications.

ASTM A194 Nut Grades descriptions:

2	Carbon steel heavy hex nuts
2H	Quenched & tempered carbon steel heavy hex nuts
2HM	Quenched & tempered carbon steel heavy hex nuts, 100% hardness tested
4	Quenched & tempered carbon-molybdenum heavy hex nuts (withdrawn in 2017)
7	Quenched & tempered alloy steel heavy hex nuts
7M	Quenched & tempered alloy steel heavy hex nuts, 100% hardness tested
7L	Quenched & tempered alloy steel heavy hex nuts, Charpy impact tested
8	Stainless AISI 304 heavy hex nuts
8M	Stainless AISI 316 heavy hex nuts

A194 Mechanical Properties

Grade Identification Marking⁵ Specification Material Nominal Size, In. Tempering Temp. °F Proof Load Stress, ksi Hardness Rockwell See Note
Min Max
ASTM A194 Grade 2 Medium Carbon Steel 1/4 - 4 0 150 159 352 1,2,3

ASTM A194 Grade 2H Medium Carbon Steel, Quenched and Tempered 1/4 - 4 850 175 C24 C38 1,2
ASTM A194 Grade 2HM Medium Carbon Steel, Quenched and Tempered 1/4 - 4 1150 150 159 237 1,2,3
ASTM A194 Grade 4 Medium Carbon Alloy Steel, Quenched and Tempered 1/4 - 4 1100 175 C24 C38 1,2
ASTM A194 Grade 7 Medium Carbon Alloy Steel, Quenched and Tempered 1/4 - 4 1100 175 C24 C38 1,2
ASTM A194 Grade 7M Medium Carbon Alloy Steel, Quenched and Tempered 1/4 - 4 1150 150 159 237 1,2,3
ASTM A194 Grade 8 Stainless AISI 304 1/4 - 4 - 80 126 300 4
ASTM A194 Grade 8M Stainless AISI 316 1/4 - 4 - 80 126 300 4
NOTES:
Markings are shown for both cold-formed and hot-forged nuts. Nuts machined from bar stock must also carry the letter “B”. The listed properties apply to coarse and 8-pitch thread heavy hex nuts. Hardness values are given in Brinell Hardness. Nuts that undergo carbide-solution treatment are additionally marked with the letter “A” (e.g., 8A or 8MA). All nuts must have the manufacturer’s identification mark clearly stamped on one face. While other grades exist, only the most common ones are shown here.

A194 Chemical Properties

Element	2, 2H, and 2HM	4	7 and 7M (AISI 4140)	8 (AISI 304)	8M (AISI 316)
Carbon	0.40% min	0.40 - 0.50%	0.37 - 0.49%	0.08% max	0.08% max
Manganese	1.00% max	0.70 - 0.90%	0.65 - 1.10%	2.00% max	2.00% max
Phosphorus, max	0.040%	0.035%	0.035%	0.045%	0.045%
Sulfur, max	0.050%	0.040%	0.040%	0.030%	0.030%
Silicon	0.40% max	0.15 - 0.35%	0.15 - 0.35%	1.00% max	1.00% max
Chromium	-	-	0.75 - 1.20%	18.0 - 20.0%	16.0 - 18.0%
Nickel	-	-	-	8.0 - 11.0%	10.0 - 14.0%
Molybdenum	-	0.20 - 0.30%	0.15 - 0.25%	-	2.00 - 3.00%

Grade Identification Marking⁵	Specification	Material	Nominal Size, In.	Tempering Temp. °F	Proof Load Stress, ksi	Hardness Rockwell		See Note
Grade Identification Marking⁵	Specification	Material	Nominal Size, In.	Tempering Temp. °F	Proof Load Stress, ksi	Min	Max	See Note
	ASTM A194 Grade 2	Medium Carbon Steel	1/4 - 4	0	150	159	352	1,2,3
	ASTM A194 Grade 2H	Medium Carbon Steel, Quenched and Tempered	1/4 - 4	850	175	C24	C38	1,2
	ASTM A194 Grade 2HM	Medium Carbon Steel, Quenched and Tempered	1/4 - 4	1150	150	159	237	1,2,3
	ASTM A194 Grade 4	Medium Carbon Alloy Steel, Quenched and Tempered	1/4 - 4	1100	175	C24	C38	1,2
	ASTM A194 Grade 7	Medium Carbon Alloy Steel, Quenched and Tempered	1/4 - 4	1100	175	C24	C38	1,2
	ASTM A194 Grade 7M	Medium Carbon Alloy Steel, Quenched and Tempered	1/4 - 4	1150	150	159	237	1,2,3
	ASTM A194 Grade 8	Stainless AISI 304	1/4 - 4	-	80	126	300	4
	ASTM A194 Grade 8M	Stainless AISI 316	1/4 - 4	-	80	126	300	4
NOTES: Markings are shown for both cold-formed and hot-forged nuts. Nuts machined from bar stock must also carry the letter “B”. The listed properties apply to coarse and 8-pitch thread heavy hex nuts. Hardness values are given in Brinell Hardness. Nuts that undergo carbide-solution treatment are additionally marked with the letter “A” (e.g., 8A or 8MA). All nuts must have the manufacturer’s identification mark clearly stamped on one face. While other grades exist, only the most common ones are shown here.

ASTM A194

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