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This specification covers the chemical and mechanical requirements for stainless steel metric hexagon socket button (SBHCS) and flat countersunk (SFHCS) head cap screws with nominal thread M 3 through M 20 intended for use in applications requiring general corrosion resistance. These steels are designated into three classes: Austenitic Class A 1-50 in an annealed condition, Austenitic Class A1-55 in a cold worked condition, and Austenitic Class A 1-70 in a cold worked condition. The austenitic stainless steel socket screw shall be designated F879M A1-50, F879M A1�55, or F 879M A1-70. Screws shall be formed by upsetting or extruding, or both. Also, these screws shall be roll threaded. Austenitic alloys ClassA 1-50 screws, following manufacture, shall be annealed by heating to a certain temperature to obtain maximum corrosion resistance and minimum permeability. The screws shall be held for a sufficient time at temperature, then cooled at a rate sufficient to prevent precipitation of the carbide and provide the properties specified. Different tests shall be conducted in order to determine the following mechanical properties of screws: tensile strength, minimum extension, yield strength, elongation, Vickers hardness, and Rockwell hardness.

Область применения

1.1 This specification covers the chemical and mechanical requirements for stainless steel inch hexagon socket button (SBHCS) and flat countersunk (SFHCS) head cap screws with nominal thread 0.060 through 0.625 in. intended for use in applications requiring general corrosion resistance.

1.2 Two groups of austenitic stainless steel alloys and three conditions are covered. See Table 1 and Table 2.

TABLE 1 Mechanical Property Requirements

Alloy Group

Alloy
Condition

Full Size Product Tests^A

Machined Specimen Tests

Core Hardness^B

Tensile
Strength ksi

Extension^C
min

Tensile
Strength ksi

Yield
Strength ksi

Elongation
% min

Vickers

Rockwell

All

   AF

   85 max

0.6D

   85 max

55 max

40

210 max

95 HRB max

All

   CW

   80 min

0.4D

   80 min

40 min

25

150 min

50 HRA min

All

   CW1

  102 min

0.4D

   87 min

65 min

20

220 min

59 HRA min

^A Actual full-size testing of condition CW and CW1 may result in decreased tensile strength because of the head configuration (see Table 3). For fasteners with nominal thread diameters larger than 0.625 in., the mechanical properties shall be agreed upon between the user and manufacturer.^B Core hardness is only required when full-size product testing cannot be accomplished.^C D denotes nominal thread size.TABLE 2 Chemical Requirements

Alloy Group

UNS Designation

Alloy

Composition, % maximum except as shown

Carbon

Manganese

Phosphorus

Sulfur

Silicon

Chromium

Nickel

Copper

Molybdeneunm

Austenitic Alloys

1

S30400

304 

0.08

2.00

0.045

0.030

1.00

18.0 to 20.0

 8.0 to 10.5

1.00

. . .

1

S30403

304L

0.030

2.00

0.045

0.030

1.00

18.0 to 20.0

 8.0 to 12.0

1.00

. . .

1

S30500

305 

0.12

2.00

0.045

0.030

1.00

17.0 to 19.0

10.5 to 13.0

1.00

. . .

1

S38400

384 

0.08

2.00

0.045

0.030

1.00

15.0 to 17.0

17.0 to 19.0

. . .

. . .

1

S30430

18–9LW 

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

. . .

1

S30433

302HQ

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

. . .

2

S31600

316 

0.08

2.00

0.045

0.030

1.00

16.0 to 18.0

10.0 to 14.0

. . .

2.00 to 3.0

2

S31603

316L

0.03

2.00

0.045

0.030

1.00

16.0 to 18.0

10.0 to 14.0

. . .

2.00 to 3.0

1.3 Units—The values stated in inch-pound units are to be regarded as standard. No other units of measurement are included in this standard.

1.4 The following precautionary caveat pertains only to the test method portion, Section 12, of this specification: This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.