ASTM A194M Specification

Standard Specification for Carbon and Alloy Steel Nuts for Bolts for High Pressure or High Temperature Service, or both.

ASTM A194M specification covers a variety of carbon, alloy, and martensitic stainless steel nuts in the size range 1/4 through 4 in. and metric M6 through M100 nominal. It also covers austenitic stainless steel nuts in the size range 1/4 in. and M6 nominal and above. These nuts are intended for high-pressure or high-temperature service, or both.

ASTM A194M Nut Grades

Grade Material UNS
Number
2H Carbon Steel -
2HM Carbon Steel -
3 Type 501 -
4 Carbon, Molybdenum Steel
-
6 Type 410 S41000
7 Type 4140, 4142, 4145, 4140H, 4142H, 4145H -
7M Type 4140, 4142, 4145, 4140H, 4142H, 4145H -
8 Type 304 S30400
8M Type 316 S31600
8T Type 321 S32100
16 Chromium Molybdenum Vanadium -

ASTM A194M Chemical Composition

Element Grade 2H, 2HM Grade 3 Grade 4 Grade 6 Grade 7, 7M Grade 8 Grade 8M Grade 8T Grade 16
Carbon 0.40 min 0.10 min 0.4-0.5 0.15 0.37-0.49 0.08 0.08 0.080 0.36 -0.47
Manganese 1.00 1.00 0.7-0.9 1.000 0.65-1.10 2.00 2.00 2.000 0.45-0.70
Phosphorus 0.04 0.04 0.035 0.04 0.035 0.045 0.045 0.045 0.035
Sulphur 0.05 0.03 0.04 0.03 0.04 0.03 0.030 0.030 0.040
Silicon 0.40 1.00 0.15-0.35 1.00 0.15-0.35 1.00 1.00 1.000 0.15-0.35
Chromium   4.0-6.0   11.5-13.5 0.75-1.2 18-20 16-18 17.0-19.0 0.80-1.15
Nickel           8-11 10-14 9.0-12.0  
Molybdenum   0.40-0.65 0.20-0.30   0.15-0.25   2.0-3.0   0.50-0.65
Titanium               5 x (C+N),
Min – 0.70 max
 
Nitrogen               0.100  
Other Elements                 Vanadium 0.25-0.35
AluminumB 0.015

ASTM A194M Hardness Requirement

Grade & Type Brinell Hardness Rockwell Hardness
C Scale B Scale
2H to 1-1⁄2 in. or M36, incl. 248-327 24-35 -
2H over 1-1⁄2 in. or M36 212-327 35 max 95 min
2HM and 7M 159-235 - 84 - 99
3, 4, 7, 16 248-327 24 - 35 -
6 225-271 20-28 -
8, 8C, 8M, 8T, 8F, 8MLCuN 126-300 32 max 60 min

ASTM A194M Proof Load

Nominal Size, mm Threads per inch Stress Area, mm2 Proof Load, lbf
All Grades of 8 Grade 2, 2HM, 6, 7M Grade 2H, 3, 4, 7, 16
Heavy hex Hex Heavy hex Hex Heavy hex Hex
M6 1.0 20.1 11.1 10.4 20.8 18.7 29.2 20.8
M8 1.25 36.6 20.1 18.8 37.9 34.0 44.1 37.9
M10 1.50 58.0 31.9 29.9 60.0 53.9 69.9 60.0
M12 1.75 84.3 46.4 43.4 87.3 78.4 101.6 87.3
M14 2.0 115.0 63.3 59.2 119.0 107.0 138.6 119.0
M16 2.0 157.0 86.4 80.9 162.5 146.0 189.2 162.5
M20 2.5 245.0 134.8 126.2 253.6 227.8 295.2 253.6
M22 2.5 303.0 166.7 156.0 313.6 281.8 365.1 313.6
M24 3.0 353.0 194.2 181.8 365.4 328.3 425.4 365.4
M27 3.0 459.0 252.5 236.4 475.1 426.9 553.4 475.1
M30 3.5 561.0 308.6 288.9 580.6 521.7 676.0 580.6
M36 4.0 817.0 449.4 420.8 845.6 759.8 984.5 845.6

ASTM A194M Marking

Grade & Type Hot Forged or Cold Punched Nuts Nuts Machined from Bar Stock
2H 2H 2HB
2HM 2HM 2HMB
4 4 4B
6 6 6B
7 7 7B
7M 7M 7MB
8 8 8B
8M 8M 8MB
8T 8T 8TB
16 16 16B