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.
1.1 Thisspecification covers the chemical and mechanical requirements forstainless steel metric hexagon socket button (SBHCS) and flatcountersunk (SFHCS) head cap screws with nominal thread M 3 throughM 20 intended for use in applications requiring general corrosionresistance.
1.2 Thefollowing three property classes are covered:
1.2.1Austenitic Class A1-50 in anannealed condition at 585 MPa maximum,
1.2.2Austenitic Class A1–55 in a cold worked condition at 550 MPaminimum, and
1.2.3Austenitic Class A1-70 in acold-worked condition at 700 MPa minimum.
1.3Units—The values stated in SIunits are to be regarded as standard. No other units of measurementare included in this standard.
1.4The following hazard caveat pertains only toSection 12, TestMethods: This standard does not purport to addressall of the safety problems, if any, associated with its use. It isthe responsibility of the user of this standard to establishappropriate safety and health practices and determine theapplicability of regulatory limitations prior touse.