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    ASTM A194 Nuts Specification

    Carbon Steel,Alloy Steel & Stainless Steel Nuts for High Temperature or High Pressure Service Applications

    Scope

    ASTM A194/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. Grade substitutions without the purchaser’s permission are not allowed.
    Bars from which the nuts are made shall be hot-wrought. The material may be further processed by centerless grinding or by cold drawing. Austenitic stainless steel may be solution annealed or annealed and strain-hardened. When annealed and strain hardened austenitic stainless steel is ordered in accor- dance with Supplementary Requirement S1, the purchaser should take special care to ensure that Supplementary Requirement S1 are thoroughly understood.
    Supplementary requirements of an optional nature are provided. These shall apply only when specified in the inquiry, contract, and order.
    ASTM A194/A194M specification is expressed in both inch-pound units and in SI units. However, unless the order specifies the applicable “M” specification designation (SI units), the mate- rial shall be furnished to inch-pound units.
    The values stated in either inch-pound units or SI units are to be regarded separately as standard. The values stated in each system may not be exact equivalents therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. Within the text, the SI units are shown in brackets.

    ASTM A194/A194M Chemical Requirements

    Grade Description
    and
    UNS Designation    		 C Mn P SE Si Cr Ni Mo Ti CbH N Cu Se V Al
    ASTM A194/A194M Grade 1 C 0.15 min 1.00 0.040 0.050 0.40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
    ASTM A194/A194M Grade 2, 2HM, and 2H C 0.40 min 1.00 0.040 0.050 0.40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
    ASTM A194/A194M Grade 3 (501) S50100 0.10 min 1.00 0.040 0.030 1.00 4.0-6.0 . . . 0.40-0.65 . . . . . . . . . . . . . . . . . . . . .
    ASTM A194/A194M Grade 6 (410) S41000 0.08-0.15 1.00 0.040 0.030 1.00 11.5-13.5 . . . . . . . . . . . . . . . . . . . . . . . . . . .
    ASTM A194/A194M Grade 6F (416) S41600 0.15 1.25 0.060 0.15 min 1.00 12.0-14.0 . . . . . . . . . . . . . . . . . . . . . . . . . . .
    ASTM A194/A194M Grade 6F (416Se) S41623 0.15 1.25 0.060 0.060 1.00 12.0-14.0 . . . . . . . . . . . . . . . . . . 0.15 min . . . . . .
    ASTM A194/A194M Grade 7G, 7MG Cr - MoG 0.38-0.48 0.75-1.0 0.035 0.04 0.15-0.35 0.80-1.10 . . . 0.15-0.25 . . . . . . . . . . . . . . . . . . . . .
    ASTM A194/A194M Grade 43 Ni-Cr-Mo 0.38–0.43 0.60–0.85 0.035 0.04 0.15–0.35 0.70–0.90 1.65–2.0 0.20–0.30 . . . . . . . . . . . . . . . . . . . . .
    ASTM A194/A194M Grade 8, 8A (304) S30400 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-11.0 . . . . . . . . . . . . . . . . . . . . . . . .
    ASTM A194/A194M Grade 8C, 8CA (347) S34700 0.08 2.00 0.045 0.030 1.00 17.0-19.0 9.0-12.0 . . . . . . 10 x C content, min 1.10 . . . . . . . . . . . . . . .
    ASTM A194/A194M Grade 8CLN, 8CLNA (347LN) S34751 0.005- 0.020 2.00 0.045 0.030 1.00 17.0-19.0 9.0-13.0 . . . . . . 0.20-0.50, 15 x C content, min 0.06-0.10 . . . . . . . . . . . .
    ASTM A194/A194M Grade 8CLNCuB, 8CLNCuBA S34752J 0.005-0.020 2.00 0.035 0.010 0.60 17.0-19.0 10.0-13.0 0.20-1.20 . . . 0.20-0.50, 15 x C content, min 0.06-0.12 2.50-3.50 . . . . . . . . .
    ASTM A194/A194M Grade 8M, 8MA (316) S31600 0.08 2.00 0.045 0.030 1.00 16.0-18.0 10.0-14.0 2.00-3.00 . . . . . . . . . . . . . . . . . . . . .
    ASTM A194/A194M Grade 8T, 8TA (321) S32100 0.08 2.00 0.045 0.030 1.00 17.0-19.0 9.0-12.0 . . . 5 x (C+N) min - 0.70 max . . . 0.10 . . . . . . . . . . . .
    ASTM A194/A194M Grade 8F, 8FA (303) S30300 0.15 2.00 0.20 0.15 min 1.00 17.0-19.0 8.0-10.0 . . . . . . . . . . . . . . . . . . . . . . . .
    ASTM A194/A194M Grade 8F, 8FA (303Se) S30323 0.15 2.00 0.20 0.06 1.00 17.0-19.0 8.0-10.0 . . . . . . . . . . . . . . . 0.15 min . . . . . .
    ASTM A194/A194M Grade 8P, 8PA (305) S30500 0.12 2.00 0.045 0.030 1.00 17.0-19.0 11.0-13.0 . . . . . . . . . . . . . . . . . . . . . . . .
    ASTM A194/A194M Grade 8N, 8NA (304N) S30451 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-11.0 . . . . . . . . . 0.10-0.16 . . . . . . . . . . . .
    ASTM A194/A194M Grade 8LN, 8LNA (304LN) S30453 0.030 2.00 0.045 0.030 1.00 18.0-20.0 8.0-11.0 . . . . . . . . . 0.10-0.16 . . . . . . . . . . . .
    ASTM A194/A194M Grade 8MN, 8MNA (316N) S31651 0.08 2.00 0.045 0.030 1.00 16.0-18.0 10.0-13.0 2.00-3.00 . . . . . . 0.10-0.16 . . . . . . . . . . . .
    ASTM A194/A194M ASTM A194/A194M 8MLN, 8MLNA (316LN) S31653 0.030 2.00 0.045 0.030 1.00 16.0-18.0 10.0-13.0 2.00-3.00 . . . . . . 0.10-0.16 . . . . . . . . . . . .
    ASTM A194/A194M Grade 8R, 8RAF (XM19) S20910 0.06 4.0-6.0 0.045 0.030 1.00 20.5-23.5 11.5-13.5 1.50-3.00 . . . 0.10-0.30 0.20-0.40 . . . . . . 0.10-0.30 . . .
    ASTM A194/A194M Grade 8S, 8SA (Nitronic 60) S21800 0.10 7.0-9.0 0.060 0.030 3.5-4.5 16.0-18.0 8.0-9.0 . . . . . . . . . 0.08-0.18 . . . . . . . . . . . .
    ASTM A194/A194M Grade 8MLCuN, 8MLCuNA (254) S31254 0.020 1.00 0.030 0.010 0.80 19.5-20.5 17.5-18.5 6.0-6.5 . . . . . . 0.18-0.22 0.50-1.00 . . . . . . . . .
    ASTM A194/A194M Grade B8ML4CuN (317) S31730 0.030 2.00 0.040 0.010 1.00 17.0-19.0 15.0-16.5 3.0-4.0 . . . . . . 0.045 4.0-5.0 . . . . . . . . .
    ASTM A194/A194M Grade 9C, 9CA (AL-6XN) N08367 0.030 2.00 0.040 0.030 1.00 20.0-22.0 23.5- 25.5 6.0-7.0 . . . . . . 0.18-0.25 0.75 . . . . . . . . .
    ASTM A194/A194M Grade 16 Cr Mo V 0.36-0.47 0.45-0.70 0.035 0.040 0.15-0.35 0.80-1.15 . . . 0.50-0.65 . . . . . . . . . . . . . . . 0.25-0.35 0.15B
    • (A) The intentional addition of Bi, Se, Te, and Pb is not permitted except for Grades 6F, 8F, and 8FA, in which Se is specified and required.
    • (B) Total aluminum, soluble and insoluble.
    • (C) Maximum, unless minimum or range is indicated.
    • (D) Where ellipses (…) appear in this table there is no requirement and the element need not be determined or reported.
    • (E) Because of the degree to which sulfur segregates, product analysis for sulfur over 0.060 % max is not technologically appropriate.
    • (F) As described in Specification A276/A276M.
    • (G) Typical steel compositions used for this grade include 4140, 4142, 4145, 4140H, 4142H, and 4145H.
    • (H) Niobium (Nb) and Columbium (Cb) are alternate names for element 41 in the Periodic Table of the Elements.
    • (I) Product Analysis-Individual determinations sometimes vary from the specified limits as shown in the tables. The several determinations of any individual element in a heat may not vary both above and below the specified range. Product variation limits are over for maximums, over or under for ranges, and under for minimums, unless otherwise indicated.

    ASTM A194/A194M Mechanical Requirements

    ASTM A194/A194M Hardness RequirementsA

    Grade and Type Completed Nuts Sample Nut after Treatment
    Brinell Hardness Rockwell Hardness Brinell Hardness, min Rockwell Hardness B Scale, min
    C Scale B Scale
    ASTM A194/A194M Grade 1 121 min ... 70 min 121 70
    ASTM A194/A194M Grade 2 159 to 352 ... 84 min 159 84
    ASTM A194/A194M Grade 2H to 11/2 in. or M36, incl 248 to 327 24 to 35 ... 179 89
    ASTM A194/A194M Grade 2H over 11/2 in. or M36 212 to 327 35 max 95 min 147 79
    ASTM A194/A194M Grade 2HM and 7M 159 to 235 ... 84 to 99 159 84
    ASTM A194/A194M Grade 3, 7, 16 and 43 248 to 327 24 to 35 ... 201 94
    ASTM A194/A194M Grade 6 and 6F 228 to 271 20 to 28 ... ... ...
    ASTM A194/A194M Grade 8, 8C, 8CLN, 8CLNCuB, 8M, 8T, 8F, 8P, 8N, 8MN, 8LN, 8MLN, 8MLCuN, 8ML4CuN, and 9C 126 to 300 32 max 60 min ... ...
    ASTM A194/A194M Grade 8A, 8CA, 8CLNA, 8CLNCuBA, 8MA, 8TA, 8FA, 8PA, 8NA, 8MNA, 8LNA, 8MLNA, 8MLCuNA, 8ML4CuNA,  and 9CA 126 to 192 ... 60 to 90 ... ...
    ASTM A194/A194M Grade 8R, 8RA, 8S, and 8SA 183 to 271 25 max 88 min ... ...
    • (A) Where ellipses (…) appear in this table there is no requirement.

    Frequently Asked Questions

    What is ASTM A194 used for?

    ASTM A194/A194M is the standard specification for carbon, alloy, and stainless steel nuts used in bolts for high-pressure or high-temperature service. It covers Grades 1, 2, 2H, 3, 4, 6, 7, 7M, 8, 8M, 8MA, 8C, 8T, 8R, and more, used in refinery, petrochemical, pressure-vessel, and valve flange bolting.

    What is the difference between ASTM A194 Grade 2H and Grade 7?

    Grade 2H is a quenched-and-tempered medium-carbon steel nut, the most widely used grade for general industrial bolting up to 800°F. Grade 7 is a quenched-and-tempered Cr-Mo alloy steel (AISI 4140) with higher strength and temperature capability, typically paired with ASTM A193 Grade B7 stud bolts.

    Which ASTM A194 grades are sour-service rated?

    Grade 2HM (carbon steel) and Grade 7M (Cr-Mo alloy) are hardness-controlled per NACE MR0175 / ISO 15156 for sour-service applications. Both must meet 22 HRC maximum hardness to resist sulfide stress cracking in H2S environments.

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