ATSM A194 Grades

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4 - Quenched & tempered carbon-molybdenum heavy hex nuts (withdrawn in 2017)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 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 0.04% 0.04% 0.04% 0.05% 0.05%
Sulfur, max 0.05% 0.04% 0.04% 0.03% 0.03%
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%

A194 Mechanical Properties
Grade Identification Marking Specification Material and Treatment Nominal Size, In. Tempering Temp. °F Proof Load Stress, ksi Hardness Rockwell See Note
Min Max
ASTM A194 Grade 2 ASTM A194
Grade 2		 Medium Carbon Steel 1/4" to 4" 0 150 159 352 1,2,3
ASTM A194 Grade 2H ASTM A194
Grade 2H		 Medium Carbon Steel, Quenched and Tempered 1/4" to 4" 850 175 C24 C38 1,2
ASTM A194 Grade 2HM ASTM A194
Grade 2HM		 Medium Carbon Steel, Quenched and Tempered 1/4" to 4" 1150 150 159 237 1,2,3
ASTM A194 Grade 4 ASTM A194
Grade 4		 Medium Carbon Alloy Steel, Quenched and Tempered 1/4" to 4" 1100 175 C24 C38 1,2
ASTM A194 Grade 7 ASTM A194
Grade 7		 Medium Carbon Alloy Steel, Quenched and Tempered 1/4" to 4" 1100 175 C24 C38 1,2
ASTM A194 Grade 7M ASTM A194
Grade 7M		 Medium Carbon Alloy Steel, Quenched and Tempered 1/4" to 4" 1150 150 159 237 1,2,3
ASTM A194 Grade 8 ASTM A194
Grade 8		 Stainless AISI 304 1/4" to 4" - 80 126 300 4
ASTM A194 Grade 8M ASTM A194
Grade 8M		 Stainless AISI 316 1/4" to 4" - 80 126 300 4

NOTES:

  1. The markings shown for all grades of A194 nuts are for cold formed and hot forged nuts. When nuts are machined from bar stock, the nut must additionally be marked with the letter 'B'. The letters H and M indicate heat treated nuts.
  2. Properties shown are those of coarse and 8-pitch thread heavy hex nuts.
  3. Hardness numbers are Brinell Hardness.
  4. Nuts that are carbide-solution treated require additional letter A - 8A or 8MA.
  5. All nuts shall bear the manufacturer’s identification mark. Nuts shall be legibly marked on one face to indicate the grade and process of the manufacturer. Marking of wrench flats or bearing surfaces is not permitted unless agreed upon between manufacturer and purchaser.
  6. Other less common grades exist, but are not listed here.

All information derived from globally recognized specifications, subject to change, user discretion is advised.