Defining 18-8 Stainless Steel
Unless a specific alloy is required for a defined purpose, selection of an 18-8 or 300 series stainless will result in a more economic fastener with improved availability.
The most common specified stainless steel alloy is 304. Type 304 stainless steel is included in the 18-8 family of stainless steel. The 18-8 family also includes alloys: 302, 302HQ, 303, 303Se and 304L. 316 is not an 18-8, but is generally accepted as an 18-8 substitute. Since it has improved corrosion resistance over the 18-8 family.
The Industrial Fastener Institute (IFI) rates all 18-8 stainless steels as equivalent in corrosion resistance. ASTM Standard F593 and F594 Alloy Group 1 covers 18-8 stainless steels, and places the same minimum physical property requirements on finished products. 316 stainless steel also has the same physical properties as group 1, except with improved corrosion resistance.
Two of the most common reasons to consider specify 18-8 alloy over 304 are:
a. Not all products are as readily available in 304.
b. Most manufactures prefer to use 302HQ rather than 304 due to its better cold forming properties and improved tool life.
For further clarification or information specific to your requirements please contact us direct at MHF.