STS Industrial - Bolts & Screws

STAINLESS STEEL FASTENERS:

TYPES, GRADES, AND STANDARDS

The differences between 304 stainless, and ASTM A193 or A320 B8 stainless can be confusing. The table below offers a very brief explanation of some of the differences between the common stainless steel fastener grades and specifications.

STAINLESS STEEL

DESCRIPTION

304 Stainless Steel AISI 304 stainless steel.
316 Stainless Steel AISI 316 stainless steel.
18-8 Stainless Steel Family of stainless steel (including 302, 302HQ, 303, 303Se, 304, 304L, 305, and 384) that are composed of 18% Chromium and 8% Nickel.
ASTM F593 Stainless Steel ASTM F593 is a specification that more stringently specifies material strengths and chemical compositions for multiple classes of stainless steel . The tensile strengths are generally higher than 304 and 316 commercial grades, and at the same time, have tighter limitations.
ASTM A193 Grade B8 Class 1 Stainless Steel Carbide solution treated 304 stainless steel, tested to meet the stringent chemical and mechanical requirements as outlined in ASTM A193 for use in high temperature and high pressure service.
ASTM A193 Grade B8M Class 1 Stainless Steel Carbide solution treated 316 stainless steel, tested to meet the stringent chemical and mechanical requirements as outlined in ASTM A193 for use in high temperature and high pressure service.
ASTM A193 Grade B8 Class 2 Stainless Steel Strain hardened and carbide solution treated 304 stainless steel, tested to meet the stringent chemical and mechanical requirements as outlined in ASTM A193 for use in high temperature and high pressure service. Strain hardening gives Class 2 stainless steel additional tensile strength over standard Class 1 stainless steel.
ASTM A193 Grade B8M Class 2 Stainless Steel Strain hardened and carbide solution treated 316 stainless steel, tested to meet the stringent chemical and mechanical requirements as outlined in ASTM A193 for use in high temperature and high pressure service. Strain hardening gives Class 2 stainless steel additional tensile strength over standard Class 1 stainless steel.
ASTM A320 Grade B8 Class 1 Stainless Steel Carbide solution treated 304 stainless steel, tested to meet the stringent chemical and mechanical requirements as outlined in ASTM A193 for use in low temperature service.
ASTM A320 Grade B8M Class 1 Stainless Steel Carbide solution treated 316 stainless steel, tested to meet the stringent chemical and mechanical requirements as outlined in ASTM A193 for use in low temperature service.
ASTM A320 Grade B8 Class 2 Stainless Steel Strain hardened and carbide solution treated 304 stainless steel, tested to meet the stringent chemical and mechanical requirements as outlined in ASTM A193 for use in low temperature service. Strain hardening gives Class 2 stainless steel additional tensile strength over standard Class 1 stainless steel.
ASTM A320 Grade B8M Class 2 Stainless Steel Strain hardened and carbide solution treated 316 stainless steel, tested to meet the stringent chemical and mechanical requirements as outlined in ASTM A193 for use in low temperature service. Strain hardening gives Class 2 stainless steel additional tensile strength over standard Class 1 stainless steel.

Sources: ASTM Standards for Mechanical Fasteners and Related Processes 2nd Edition, Inch Fastener Standards 8th Edition, Kanebridge Fastener Reference Guide 4th Edition

Note: All material included on this page is informational only, and should not be used as one’s sole source for design purposes. STS Industrial, Inc. and its affiliates do not guarantee the accuracy of the information on this site, and retain no liability for the use or misuse of the information contained on this site.