ASTM A194 / A194M

ASTM A194 Specification covers Carbon and Alloy Steel Nuts most popular grade 2H, 2HM, 3, 4, 6, 7, 7M, 8, 8M, 8T, 16, etc., to be used with ASTM A193 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.

Nut Grades

Grades Material UNS Number
2H Carbon Steel -
2HM Carbon Steel -
3 Ferritic Stainless Steel Type 501 S50100
4 Carbon, Molybdenum Steel
-
6 Ferritic Stainless Steel Type 410 S41000
7 Chromium Molybdenum Steel Type 4140, 4142, 4145, 4140H, 4142H, 4145H -
7M Chromium Molybdenum Steel Type 4140, 4142, 4145, 4140H, 4142H, 4145H -
8 Austenitic Stainless Steel Type 304 S30400
8M Austenitic Stainless Steel Type 316 S31600
8T Austenitic Stainless Steel Type 321 S32100
16 Chromium Molybdenum Vanadium Alloy Steel -

(For all grades, please visit ASTM A194 Grades)

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 -
Others - - - - - - - - Vanadium 0.25-0.35
Aluminum 0.015 max

Nut Hardness Requirement

Nut Grade Brinell Hardness Rockwell Hardness
HRC HRB
2H To 1-1⁄2 in. or M36, incl. 248 - 327 24 - 35 -
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

Nut Proof Load

Nominal Size, inch Threads per 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 2 540 2 380 4 770 4 300 5 570 4 770
5/16" 18 4 190 3 930 7 860 7 070 9 170 7 860
3/8" 16 6 200 5 810 11 620 10 460 13 560 11 620
7/16" 14 8 500 7 970 15 940 14 350 18 600 15 940
1/2" 13 11 350 10 640 21 280 19 160 24 830 21 280
9/16" 12 14 560 13 650 27 300 24 570 31 850 27 300
5/8" 11 18 080 16 950 33 900 30 510 39 550 33 900
3/4" 10 26 720 25 050 50 100 45 090 58 450 50 100
7/8" 9 36 960 34 650 69 300 62 370 80 850 69 300
1" 8 48 480 45 450 90 900 81 810 106 000 90 900
1 1/8" 8 63 200 59 250 118 500 106 700 138 200 118 500
1 1/4" 8 80 000 75 000 150 000 135 000 175 000 150 000
1 3/8" 8 98 640 92 450 185 000 166 500 215 800 185 000
1 1/2" 8 119 360 111 900 223 800 201 400 261 100 223 800

Nut Marking

Nut Grade 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