ASTM F836M Specification

This specification covers the chemical and mechanical requirements for stainless steel metric nuts with nominal thread diameters M1.6 through M36 and intended for use in engineering applications requiring general corrosion resistance.

Eight groups of stainless steel alloys are covered, including three austenitic (Grades A1, A2, and A4), one ferritic (Grade F1), three martensitic (Grades C1, C3, and C4), and one precipitation hardening (Grade P1).

Seventeen property classes are covered, including nine austenitic, one ferritic, six martensitic, and one precipitation hardening. The property classes with the permissible alloys for each are listed in Table below.

This specification is based in concept and content on ISO 3506. The chemical and mechanical requirements specified for all property classes, except as given in 1.4.1, are essentially identical with classes of the same designation in ISO 3506.

This specification includes 13 of the 16 property classes covered in ISO 3506.. Additionally, it includes property classes A1-70, A2-70, A4-70, A1-80, A2-80, and A4-80 for products with nominal thread diameters larger than M20; and four non-ISO property classes, C1-110, C4-110, C3-120, and P1-90.

Supplementary requirements of an optional nature are provided, applicable only when agreed upon between the manufacturer and the purchaser at the time of the inquiry and order.

Suitable bolts, hex cap screws, and studs for use with nuts included in this specification are covered by Specification F738M. Unless otherwise specified, all bolts, hex cap screws, and studs used with these nuts shall conform to the requirements of Specification F738M and shall be of the same alloy group.

The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

Property Classes of Stainless Steel Nuts

Property Class Permissible Alloys
A1-50 304, 304L, 305A
A1-70 384, 18-9LW, 302HQ
A1-80
A2-50
A2-70 321, 347
A2-80
A4-50
A4-70 316, 316L
A4-80
F1-45 430B
C1-70 410
C1-110
C3-80 431
C3-120
C4-70 416, 416Se
C4-110
P1-90 630
Note:

A. When approved by the purchaser, Alloys 303, 303Se, or XM1 may be furnished.

B. When approved by the purchaser, Alloy 430F may be furnished.

Materials and Manufacture

Forming— Unless otherwise specified, nuts shall be cold-formed, hot-formed, or machined, at the option of the manufacturer.

Condition— Nuts shall be furnished in the condition specified for the property class in Table mechanical-properties-requriements. If other conditions are required, the condition and resultant mechanical properties shall be as agreed upon between the manufacturer and the purchaser.

Surface Finish— Unless otherwise specified, nuts shall be cleaned and descaled in accordance with Practice A380.

Heat Treatment

Austenitic Alloys, Grades A1, A2, and A4:
1. When Condition A is specified, the nuts shall be machined from annealed or solution annealed stock, thus retaining the properties of the original material, or hot formed and solution annealed.
2. When Condition AF is specified, the nuts, following manufacture, shall be annealed by heating to 1040 6 30°C, at which time the chromium carbide will go into solution. The nuts shall be held for a sufficient time and then cooled at a rate sufficient to prevent precipitation of the carbide and to provide the properties specified in Table mechanical-properties-requriements.
3. When Condition CW is specified, the austenitic alloy shall be annealed as specified in 1, and then cold-worked to develop the properties specified in Table mechanical-properties-requriements.
4. When Condition SH is specified, nuts shall be machined from strain hardened stock.

Ferritic Alloys, Grade F1:
1. When Condition A is specified, the ferritic alloy shall be heated to a temperature of 790 6 30°C, held for an appropriate time, and then air-cooled to provide the properties specified in Table mechanical-properties-requriements.
2. When Condition AF is specified, nuts shall be treated as specified in 2.

Martensitic Alloys, Grades C1, C3, and C4:
1. When Condition H is specified, the nuts shall be hardened and tempered by heating to 1010 6 30°C sufficient for austenitization, holding for at least 1 h and then air-cooling to provide the properties specified in Table mechanical-properties-requriements.
2. When Condition HT is specified, the nuts shall be hardened and tempered by heating to 1010 6 30°C sufficient for austenitization, holding for at least 1⁄2 h, rapid air- or oil-quenching, reheating to 275°C minimum, and holding for at least 1 h and then air-cooling to provide the properties specified in Table mechanical-properties-requriements.

Precipitation-Hardening Alloy, Grade P1—When Condition AH is specified, the nuts shall be solution-annealed and aged by heating to 1040 6 15°C, holding for at least 1⁄2 h, rapid air- or oil-quenching to 27°C maximum, reheating to 620 6 10°C minimum, holding for 4 h, and then air-cooling to provide the properties specified in Table mechanical-properties-requriements.

Chemical Composition

It is the intent of this specification that nuts shall be ordered by property class.
Unless otherwise specified in the inquiry and purchase order (see Supplementary Requirement S2), when two or more alloys are permitted for nuts of a specified property class, the choice of alloy to be used shall be that of the fastener manufacturer as determined by his nut fabrication methods and material availability. The specific alloy used by the manufacturer shall be identified clearly on any certification required in the purchase order and shall have a chemical composition conforming to the limits specified in Table below.
When the purchaser specifies that a specific alloy be used, the alloy shall have a chemical composition conforming to the limits specified in Table below.
Product analysis may be made by the purchaser from nuts representing each lot. The chemical composition thus determined shall conform to the limits specified in Table below for the specific alloy within the product analysis tolerances specified in Specification A555/A555M.
In the event of discrepancy, a referee analysis of samples for each lot shall be made in accordance with 12.1.

Chemical Requirement

Alloy
Groups		 Alloy UNS
Designation		 Composition, % maximum except as shown
Carbon Manganese Phosphorus Sulfur Silicon Chromium Nickel Copper Molybdenum Other
Austhenitic Alloys
A1 303 S30300 0.15 2.00 0.20 0.15 min 1.00 17.0 to 19.0 8.0 to 10.0 0.60 max4
A1 303Se S30323 0.15 2.00 0.20 0.060 1.00 17.0 to 19.0 8.0 to 10.0 Se 0.15 min
A1 304 S30400 0.08 2.00 0.045 0.030 1.00 18.0 to 20.0 8.0 to 10.0 1.00
A1 304L S30403 0.03 2.00 0.045 0.030 1.00 18.0 to 20.0 8.0 to 10.0 1.00
A1 305 S30500 0.12 2.00 0.045 0.030 1.00 17.0 to 19.0 10.5 to 13.0 1.00
A1 384 S38400 0.08 2.00 0.045 0.030 1.00 15.0 to 17.0 17.0 to 19.0
A1 XM1 S20300 0.08 5.0 to 6.5 0.040 0.18 to 0.35 1.00 16.0 to 18.0 5.0 to 6.0 1.75 to 2.25 0.50 maxA
A1 18-9LW S30430 0.10 2.00 0.045 0.030 1.00 17.0 to 19.0 8.0 to 10.0 3.0 to 4.0
A1 302HQ S30433 0.03 2.00 0.045 0.030 1.00 17.0 to 19.0 8.0 to 10.0 3.0 to 4.0
A4 316 S31600 0.08 2.00 0.045 0.030 1.00 16.0 to 18.0 10.0 to 14.0 2.00-3.00
A4 316L S31603 0.03 2.00 0.045 0.030 1.00 16.0 to 18.0 10.0 to 14.0 2.00-3.00
A4 321 S32100 0.08 2.00 0.045 0.030 1.00 17.0 to 19.0 9.0 to 12.0 Ti 5 x c min
A2 347 S34700 0.08 2.00 0.045 0.030 1.00 17.0 to 19.0 9.0 to 13.0 Cb + Ta 10 x C min
Ferritic Alloys
F1 430 S43000 0.12 1.00 0.040 0.030 1.00 16.0 to 18.0
F1 430F S43020 0.12 1.25 0.060 0.15 min 1.00 16.0 to 18.0 0.60 maxA
Martensitic Alloys
C1 410 S41000 0.15 1.00 0.040 0.030 1.00 11.5 to 13.5
C4 416
416Se		 S41000 0.15 1.25 0.060 0.15 min 1.00 12.0 to 14.0 0.60 maxA Se 0.15 min
C4 S41623 0.15 1.25 0.060 0.060 1.00 12.0 to 14.0
C3 431 S43100 0.20 1.00 0.040 0.030 1.00 15.0 to 17.0 1.25 to 2.50
Precipitation Hardening Alloys
P1 630 S17400 0.07 1.00 0.040 0.030 1.00 15.0 to 17.5 3.0 to 5.0 3.0 to 5.0 Cb + Ta 0.15-0.45
Note:

A : At manufacturer's option, determined only when intentionally added.

Mechanical Properties

1. The hardness of nuts of each class shall not exceed the maximum hardness specified for the class in Table below. This shall be the only hardness requirement for nuts that are proof load tested.

2. Unless proof load testing is specified in the inquiry and purchase order, nuts of all classes in nominal thread diameters M4 and smaller, and nuts of all classes with proof loads greater than 530 kN, as specified in Table below, shall be furnished on the basis of having a hardness not less than the minimum hardness specified in Table below.

3. All classes of nuts, except those covered in table below. shall withstand the proof load as specifed in Table below.

Mechanical Property Requirement

Property Class ConditionA Alloy/Mehcanical
Property Marking		 Nominal Thread
Diameter		 Proof Load
Strees, MPa		 Hardness
Vickers Rockwell
Min Max Min Max
A1-50
A or AF		 F836A
M1.6 to M36
500
155
220
B81
B95
A2-50 F836B
A4-50 F836C
A1-70
CW		 F836D M1.6 to M36
over M20 to M36		 700
550		 220
160		 330
310		 B96
B83		 C33
C31
A2-70 F836E
A4-70 F836F
A1-80
SH		 F836G M1.6 to M36 800 240 350 C23 C36
A2-80 F836H over M20 to M24 700 220 330 B96 C33
A4-80 F836J over M24 to M30 650 200 310 B93 C30
over M30 to M36 600 180 285 B89 C28
F1-45 A or AF F836K M1.6 to M36 450 135 220 B74 B96
C1-70
H		 F836L
M1.6 to M36
700
220
330
B96
C34
C4-70 F836M
C1-110
HT		 F836N
M1.6 to M36
1100
350
440
C36
C45
C4-110 F836P
C3-80 H F836R M16 to M36 800 240 340 C23 C35
C3-120 HT F836S M1.6 to M36 1200 380 480 C39 C48
P1-90 AH F836T M1.6 to M36 900 285 480 C39 C48
A Legend of Conditions:

AF-- formed and annealed.

CW-- formed form annealed stock, thus acquiring a degree of cold work.

SH-- machined from strain hardened stock.

A-- machined from annealed or solution annealed stock, thus retaining the properties of the original material, or hot formed and solution annealed.

H-- hardened and tempered at 565°C medium.

HT-- hardened and tempered at 275°C medium.

AH-- solution annealed and age hardened after forming.

Nut Proof Load Values, kN

Nominal Size and
Thread Pitch		 Stress Area,
mm2		 Proof Load Stress, MPaA
450 500 550 600 650 700 800 900 1100 1200
M1.6 x 0.35 1.17 0.57 0.64 ... 0.76 ... 0.89 1.02 1.14 1.40 1.52
M2 x 0.4 2.07 0.93 1.04 ... 1.24 ... 1.45 1.66 1.86 2.28 2.48
M2.5 x 0.45 3.39 1.52 1.70 ... 2.03 ... 2.37 2.71 3.05 3.73 4.07
M3 x 0.5 5.03 2.26 2.52 ... 3.02 ... 3.52 4.02 4.53 5.53 6.04
M3.5 x 0.6 6.78 3.05 3.39 ... 4.07 ... 4.75 5.42 6.10 7.46 8.14
M4 x 0.7 8.78 3.95 4.39 ... 5.27 ... 6.15 7.02 7.90 9.66 10.5
M5 x 0.8 14.2 6.39 7.10 ... 8.52 ... 9.94 11.4 12.8 15.6 17.0
M6 x 1 20.1 9.05 10.1 ... 12.1 ... 14.1 16.1 18.1 22.1 24.1
M8 x 1.25 36.6 16.5 18.3 ... 22.0 ... 25.6 29.3 32.9 40.3 43.9
M10 x 1.5 58.0 26.1 29.0 ... 34.8 ... 40.6 46.4 52.2 63.8 69.6
M12 x 1.75 84.3 37.9 42.2 ... 50.6 ... 59.0 67.4 75.9 92.7 101
M14 x 2 115 51.7 57.5 ... 69.0 ... 80.5 92.0 104 127 138
M16 x 2 157 70.7 78.5 ... 94.2 ... 110 126 141 173 188
M20 x 2.5 245 110 123 135 147 ... 172 196 221 270 294
M24 x 3 353 159 177 194 212 ... 247 282 318 388 424
M30 x 3.5 561 252 281 309 337 365 393 449 505 617 673
M36 x 4 817 368 409 449 490 ... 572 654 735 899 980

AProof Load = As x Proof Load Stress
As = 0.7854(D - 0.9382 P)2
Where: D = nominal, mm,
             P = thread pitch, mm, and
             Proof Load Stress is found in Table mechanical-properties-requriements.

Dimensions

Unless otherwise specified, nuts shall conform to dimensions for hex nuts, Style 1, as given in ISO 4032.
Unless otherwise specified, threads shall be metric coarse threads with class 6H tolerances as specified in ASME B1.13M

Number of Tests and Retests

The mechanical and chemical composition requirements of this specification shall be met in continuous mass production for stock, and the manufacturer shall make sample inspections to ensure that the product conforms to the specified requirements. Additional tests of individual shipments of material are not ordinarily necessary.

Individual heats of steel are not identified in the finished product. When specified in the purchase order that the heat number shall be identified for the products in an individual shipment, the manufacturer shall control the product by heat analysis and additionally shall conduct the testing program specified in above table.

Unless otherwise specified, tests for corrosion resistance shall be in accordance with the manufacturer's standard quality control practices. A specific number of tests is not required but the nuts shall be produced by manufacturing practices and subjected to tests and inspection to assure compliance with the specified requirements.
When specified on the purchase order, not less than one corrosion test to determine freedom from precipitated carbides shall be made to represent each lot.

When the purchaser requires that additional tests be performed by the manufacturer to determine that the properties of nuts in an individual shipment are within specified limits, the purchaser shall specify Supplementary Requirement S1 in the inquiry and purchase order.
When the purchaser does not specify the sampling plan and basis of acceptance the following shall apply:
1. The lot, for purposes of selecting samples, shall consist of all nuts offered for inspection and testing, at one time, that are the same type, style, nominal diameter, thread pitch, material (alloy), property class, and surface finish.
2. From each lot, samples shall be selected at random and tested for each requirement in accordance with the following plan:

Number of Pieces in LOt Number of Tests Acceptance Criteria Acceptance Number Rejection Number
800 and less 1 0 1
801 to 8000 2 0 1
8001 to 22,000 3 0 1
Over 22,000 5 0 1

3. If the failure of a test specimen is due to improper preparation of the specimen or to incorrect testing technique, the specimen shall be discarded and another test specimen substituted.

Test Methods

Chemical Analysis—Chemical analysis shall be performed in accordance with Test Methods, Practices and Terminology A751.
Mechanical Tests:
1. Hardness and proof load tests of nuts shall be performed in accordance with requirements of Test Methods F606M.
2. For nut proof load testing, the speed of testing as determined with a free-running crosshead shall be a maximum of 25 mm/min.
3. Corrosion Resistance—Corrosion tests to determine freedom from precipitated carbide shall be performed in accordance with Practice A262, Practices A or E, as applicable.
4. For the purposes of determining compliance with the specified limits for properties listed in this specification, an observed value or calculated value shall be rounded in accordance with Practice E29.

Product Marking

1. Nuts in nominal thread diameters M4 and smaller need not be marked.
2. All products with a nominal size of M5 and larger shall be marked with a symbol identifying the manufacturer. In addition, they shall be marked with the alloy/mechanical property marking specified in Table mechanical-properties-requriements. The marking shall be raised or depressed at the option of the manufacturer.
3. The manufacturer's symbol shall be of his design.
4. The markings shall be on the top of nut, top of flange, or on one of the wrenching flats.
5. Markings located on one of the wrenching flats shall be depressed. Markings on all other locations shall be raised or depressed at the option of the manufacturer.

SUPPLEMENTARY REQUIREMENTS

One or more of the following supplementary requirements shall apply only when specified by the purchaser in the inquiry and order. Supplementary requirements shall in no way negate any requirement of the specification itself.

S1. Additional Tests

When tests for additional mechanical properties, corrosion resistance, etc., are desired by the purchaser, the test(s) shall be made as agreed upon between the manufacturer and the purchaser at the time of the inquiry or order.

S2. Alloy Control

When Supplementary Requirement S2 is specified on the inquiry and order, the manufacturer shall supply that alloy specified by the customer on his order with no group substitutions permitted without the written permission of the purchaser

S3. Permeability

When Supplementary Requirement S3 is specified on the inquiry and order, the permeability of nuts of Grades A1, A2, and A4 in Conditions A or AF shall not exceed 1.5 at 100 oersteds when determined by Methods A342/342M

S4. Shipment Lot Testing

1. When Supplementary Requirement S4 is specified on the order, the manufacturer shall make sample tests on the individual lots for shipment to ensure that the product conforms to the specified requirements.
2. The manufacturer shall make an analysis of a randomly selected finished nut from each lot of product to be shipped. Heat or lot control shall be maintained. The analysis of the starting material from which the nuts have been manufactured may be reported in place of the product analysis.
3. The manufacturer shall perform mechanical property tests in accordance with this specification and Guide F1470 on the individual lots for shipment.
4. The manufacturer shall furnish a test report for each lot in the shipment showing the actual results of the chemical analysis and mechanical property tests performed in accordance with Supplementary Requirement S4.

S5. Heat Control

1. When Supplementary Requirement S5 is specified on the inquiry or order, the manufacturer shall control the product by heat analysis and identify the finished product in each shipment by the actual heat number or lot number that is heat lot traceable.
2. When Supplementary Requirement S5 is specified on the inquiry or order, Supplementary Requirements S2 and S4 shall be considered automatically invoked with the addition that the heat analysis shall be reported to the purchaser on the test report.

Referenced Documents

ASTM Standard:

A262 Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels.
A342/A342M Test Methods for Permeability of Weakly Magnetic Materials.
A380 Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems.
A493 Specification for Stainless Steel Wire and Wire Rods for Cold Heading and Cold Forging.
A555/A555M Specification for General Requirements for Stainless Steel Wire and Wire Rods.
A564/A564M Specification for Hot-Rolled and Cold-Finished Age-Hardening Stainless Steel Bars and Shapes.
A582/A582M Specification for Free-Machining Stainless Steel Bars.
A751,Test Methods, Practices, and Terminology for Chemical Analysis of Steel Products.
D3951 Practice for Commercial Packaging.
E29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications.
F606M Test Methods for Determining the Mechanical Properties of Externally and Internally Threaded Fasteners, Washers, and Rivets (Metric).
F738M Specification for Stainless Steel Metric Bolts, Screws, and Studs (Withdrawn 2014).
F1470 Practice for Fastener Sampling for Specified Mechanical Properties and Performance Inspection..

ISO Standard:

ISO 3506 Corrosion-Resistant Stainless Steel Fasteners.
ISO 4032 Hexagon regular nuts (style 1)—Product grades A and B.

ASME Standards:

B1.13M Metric Screw Threads—M Profile.
ASME B18.2.4.4M Metric Hex Flange Nuts.