Can I order bolts to Type 304 or 316 stainless steel?
Type 304 and Type 316 are very common stainless steel grades that just refer to a type of stainless steel. If you were to look for Type 304 or 316 stainless steel bolts in the ASTM Fastener Standards Manual you aren’t going to find them. That is because they are steel grades as opposed to fastener specifications, but engineers will specify them, and contractors request them.
What is the issue?
The inherent problem with trying to order bolts to a stainless steel grade is that steel standards like Type 304 and Type 316 do not include the necessary fastener information such as bolt configuration, thread pitch, head style, dimensional tolerances, washer or nut compatibility, acceptable coatings, etc. For example, ASTM A193 Grade B8 is a fastener specification made from Type 304 stainless steel. It covers stainless bolts and studs used in high pressure and high-temperature applications and has the following sections detailing bolt specifics:
- Section 3: General Requirements and Ordering Information
- Section 4: Common Requirements
- Section 5: Manufacture Process
- Section 6: Heat Treatment
- Section 7: Chemical Composition
- Section 8: Heat Analysis
- Section 9: Mechanical Properties
- Section 10: Workmanship, Finish, and Appearance
- Section 12: Test Specimens
- Section 13: Suitable Nuts
- Section 14: Certification
- Section 15: Product Marking
- Supplementary Requirements
The specification for stainless steel bars and shapes is ASTM A276, but that doesn’t include any specifics about bolts and how to make them. Without these details, every mundane aspect of the fastener would need to be discussed and decided between the purchaser and the manufacturer, or assumptions would need to be made that may or may not meet the needs of the application the bolts are being used in.
The biggest issue with ordering hot forged stainless bolts, when not ordered to a fastener specification, is that manufacturers can skip the crucial step of solution annealing and testing. Fastener specifications A193, A320, and F593, which can be made fromType 304 or 316 stainless round bar, require solution annealing after forging, and F593 requires an inner granular test after solution annealing which will ensure optimum corrosion resistance. Bolts ordered to a steel grade will not require solution annealing or inner granular testing which could cause the bolts to corrode prematurely.
We always suggest engineers specify and contractors order bolts to a stainless steel ASTM fastener specification such as A193, A320, or F593 for the reasons listed above. Portland Bolt is happy to answer questions like these or similar. We are the bolt experts; feel free to use us as a resource.