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ASTM A194 Specification

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

ASTM A194 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 A194 Nut Grades

Grade Material UNS
Number
2H, 2HM Carbon Steel -
3 Type 501 -
4 Carbon, Molybdenum Steel
-
6 Type 410 S41000
7, 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 A194 Chemical Components

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 A194 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 A194 Proof Load

Nominal Size, inch Threads per inch Stress Area inch Proof Load, lbf
All Grades of 8 Grade 2, 2HM, 6, 6f, 7M Grade 2H, 4, 7, 16
Heavy Hex Hex Heavy Hex Hex Heavy Hex Hex
1/4" 20 0.0316 2 540 2 380 4 770 4 300 5 570 4 770
5/16" 18 0.0524 4 190 3 930 7 860 7 070 9 170 7 860
3/8" 16 0.0774 6 200 5 810 11 620 10 460 13 560 11 620
7/16" 14 0.1063 8 500 7 970 15 940 14 350 18 600 15 940
1/2" 13 0.1419 11 350 10 640 21 280 19 160 24 830 21 280
9/16" 12 0.1820 14 560 13 650 27 300 24 570 31 850 27 300
5/8" 11 0.2260 18 080 16 950 33 900 30 510 39 550 33 900
3/4" 10 0.3340 26 720 25 050 50 100 45 090 58 450 50 100
7/8" 9 0.4620 36 960 34 650 69 300 62 370 80 850 69 300
1" 8 0.606 48 480 45 450 90 900 81 810 106 000 90 900
1 1/8" 8 0.7900 63 200 59 250 118 500 106 700 138 200 118 500
1 1/4" 8 1.0000 80 000 75 000 150 000 135 000 175 000 150 000
1 3/8" 8 1.2330 98 640 92 450 185 000 166 500 215 800 185 000
1 1/2" 8 1.492 119 360 111 900 223 800 201 400 261 100 223 800

ASTM A194 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