ASTM A194

The ASTM A194 specification is an ASTM International standard that governs nuts intended for use in high-pressure, high-temperature service, or both. This standard covers a wide range of carbon, alloy, and stainless steel nuts, available in sizes from 1/4″ to 4″ (and metric sizes M6 through M100 nominal). Specifically, it includes carbon, alloy, and martensitic stainless steel nuts in that full size range, while austenitic stainless steel nuts are covered for sizes 1/4″ and M6 nominal and above. Common grades included in the A194 specification are 2H, 2HM, 3, 4, 6, 7, 7M, 8, 8M, 8T, and 16, among others. These nuts are typically paired with ASTM A193 bolts. The materials used to make these nuts must be hot-wrought bars, which may then undergo further processing like centerless grinding or cold drawing. Austenitic stainless steel materials can be solution annealed or annealed and strain-hardened, with specific care required by the purchaser to understand related requirements (like Supplementary Requirement S1) when ordering strain-hardened material. It’s also important to note that grade substitutions are not permitted without the purchaser’s explicit permission.