MIL-S-6721 - Chemically Stabilized Stainless Steel Plate, Sheet & Strip
MIL-S-6721 is an old military standard for corrosion- and heat-resistant, chemically stabilized stainless steel, which is used for plates, sheets, and strips. It specifies the chemical and mechanical requirements for the material to be used in high-performance applications.
Status: It has been cancelled in June 1971, replaced by more modern AMS standards, namely AMS 5510 and AMS 5512, which are for 321 stainless steel in solution heat treated condition. These modern standards provide better corrosion resistance, better performance at high temperatures, as well as better weldability than the old military standard.
Superseded By AMS Standards
The following AMS specifications replaced MIL-S-6721:
- AMS 5510: 321 stainless steel, plate and sheet, solution heat-treated
- AMS 5512: 321 stainless steel, plate, corrosion and heat-resistant, solution heat-treated
These modern standards provide tighter controls over chemical composition, mechanical properties, and heat treatment, ensuring reliable performance for aerospace, defense, and industrial applications.
What is 321 Stainless Steel ?
321 Stainless Steel is a titanium stabilized chromium nickel austenitic stainless steel with corrosion resistance similar to 304/304L.
321 STAINLESS STEEL SPECIFICATIONS
SHEET SOLUTION HEAT TREATED
Annealed sheets offering excellent corrosion resistance and formability for demanding applications.
TUBING
Precision tubes designed for corrosion resistance and mechanical reliability in fluid systems.
321 BARS & FORGINGS
High-quality bars and forgings suitable for structural, machined, and high-stress components.
FEDERAL & MILITARY SPECIFICATIONS
Government-certified sheets ensuring performance and durability under critical service conditions.
OIL & GAS
Materials engineered to withstand sour gas, chloride stress, and harsh operating environments.
Certified Material for Critical Service
Materials produced and supplied to AMS 5510, AMS 5645, AMS 5689, and related specifications can be delivered with:
- Certificates of Compliance (CoC) confirming adherence to AMS and ASTM standards.
- Mill Test Reports (MTRs) specifying chemical composition, mechanical properties, and heat-treatment data.
- Traceability documentation from melt source to final product batch.
Such certification is essential for aerospace, oil & gas, and defense applications, where traceable quality assurance is required for safety and regulatory compliance.