ASTM A194 Specification
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The ASTM A194 specification covers carbon, alloy and stainless steel nuts intended for use in high-pressure and/or high-temperature service. Unless otherwise specified, the American National Standard Heavy Hex Series (ANSI B 18.2.2) shall be used. Nuts up to and including 1 inch nominal size shall be UNC Series Class 2B fit. Nuts over 1 inch nominal size shall be either UNC Series Class 2B fit or 8 UN Series Class 2B fit. High strength ASTM A194 grade 2H nuts are common in the marketplace and are often substituted for ASTM A563 grade DH nuts due to the limited availability of DH nuts in certain diameters and finishes.
Each alloy shall conform to the chemical composition requirements prescribed. Hardness tests, proof of load tests, and cone proof load tests shall be made to all nuts to meet the requirements specified.
Grades Covered Under Astm A194
2 | Carbon steel heavy hex nuts |
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2H | Quenched & tempered carbon steel heavy hex nuts |
2HM | Quenched & tempered carbon steel heavy hex nuts |
4 | Quenched & tempered carbon-molybdenum heavy hex nuts |
7 | Quenched & tempered alloy steel heavy hex nuts |
7M | Quenched & tempered alloy steel heavy hex nuts |
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:
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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% |
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Molybdenum |
0.20 - 0.30% |
0.15 - 0.25% |
2.00 - 3.00% |
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