In our article today, we want to present a summary of the characteristics and properties for stainless steel 304 comparing the ASTM A-240-19 and A-666-15 standards that are current and applicable to this type of stainless steel.
Standard Specification ASTM A-240-19 for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications.
Standard Specification ASTM A-666-15 for Annealed or Cold-Worked Austenitic Stainless Steel Sheet, Strip, Plate, and Flat Bar
The chemical composition between one standard and another only has a slight variation in the % of Nickel (Ni) due to an update that ASTM made in the A-240 version 2019, however, Ni as one of the main alloy elements, and the most expensive of all those that make up this steel, manufacturers of stainless steel keep it at the minimum of the standard range, so there is no practical effect on the steels that are commercially supplied.
On the other hand, the mechanical properties are the same in the Annealed condition, which is the case at hand.
The stainless steel 304 is manufactured according to the ASTM A-240 standard because this is the predominant one for materials in the Annealed condition (softest condition).
When the 304 steel must be hardened by deformation (Cold Worked) from the Annealed condition to a higher grade, the mechanical properties are based on the ASTM A-666 standard where the different Tempers (hardening grades) are defined.
Because of the above, it is relevant to review the reference standard with which a material is purchased, a specification is reviewed or information is generated for a new project.
The commercial practice of stainless steel manufacturers and the marketing chain is to certify materials in the Annealed condition with the A-240 standard, while materials that have been hardened by deformation to a higher Temper are certified with the A-666 standard.
