SAE AMS 27594D:2018 pdf free

SAE AMS 27594D:2018 pdf free.Heat Treatment Austenitic Corrosion- Resistant Steel Parts
Shall be controlled so as not to contaminate the parts being heat treated. Furnaces used to heat treat other classes of steel using atmospheres that could contaminate austenitic corrosion-resistant steel parts, such as endothermic, exothermic,carbon-containing nitrogen-base, etc., shall have purge cycles (see 8.2) run and then shall be tested as required in3.4.1 to ensure that the surfaces of parts are free from nitriding and intergranular oxidation. Parts being heat treated shall be suitably isolated from products of combustion. Materials that could attack or contaminate metal shall not contact parts during heat treatment. Composition and maintenance of salt baths shall be such as to prevent contamination of the parts. Salt baths shall be tested in accordance with AMS2759.
Parts shall be heat treated in either air or protective atmosphere. Acceptable protective atmospheres include argon, helium,hydrogen, neutral salt, and vacuum. Nitrogen and nitrogen-hydrogen blends are permited as a backfill quench for vacuum furnaces and as a protective atmosphere if a minimum of 0.020 inch (0.51 mm) is to be removed from all surfaces after heat treatment. Use of nitrogen from dissociated ammonia is prohibited. For scale-free or discoloration-free parts, an air atmosphere and air cooling should be avoided.
A protective coating is permitted to minimize oxidation on finished machined surfaces when approved by the cognizant engineering organization. Approval is not required when it can be demonstrated that the coating can effectively prevent intergranular oxidation in excess of 0.0007 inch (0.018 mm) (see 3.5.1). AlI protective coatings shall be removed after heat treatment.
Surface contamination (3.4.1) is a preproduction test and shall be performed prior to any production heat treating for each piece of equipment and type of atmosphere to be used in each furnace. Carbide precipitation if applicable (3.4.2) is a preproduction test and shall be performed prior to any production heat treatment for each piece of equipment and each alternate quenching and cooling method used.SAE AMS 27594D pdf free download.