{"id":6904,"date":"2022-02-10T01:53:16","date_gmt":"2022-02-09T17:53:16","guid":{"rendered":"https:\/\/xzfastener.com\/?p=6904"},"modified":"2026-06-23T01:55:03","modified_gmt":"2026-06-22T17:55:03","slug":"stainless-steel-bolt-grades-a2-70-a4-70-and-a4-80-explained","status":"publish","type":"post","link":"https:\/\/xzfastener.com\/ru\/stainless-steel-bolt-grades-a2-70-a4-70-and-a4-80-explained\/","title":{"rendered":"Stainless Steel Bolt Grades: A2-70, A4-70 and A4-80 Explained"},"content":{"rendered":"

Stainless steel bolt grades are often misunderstood in purchasing. Buyers may ask for \u201c304 stainless bolts\u201d or \u201c316 stainless bolts,\u201d but the actual fastener marking often appears as A2-70, A4-70, or A4-80.<\/p>\n\n\n\n

These markings tell two things: the stainless steel group and the mechanical property class. Both matter.<\/p>\n\n\n\n

What A2 and A4 Mean<\/h2>\n\n\n\n

Stainless Steel Group<\/h3>\n\n\n\n

A2 is commonly used for general corrosion-resistant stainless fasteners. It is often associated with 304-type stainless steel.<\/p>\n\n\n\n

A4 is used where stronger corrosion resistance is required. It is commonly associated with 316-type stainless steel and is preferred in chloride, marine, chemical, or wet environments.<\/p>\n\n\n\n

Buyers can review stainless steel fasteners<\/a> when selecting between A2 and A4 materials.<\/p>\n\n\n\n

What 70 and 80 Mean<\/h2>\n\n\n\n

Mechanical Property Class<\/h3>\n\n\n\n

The number after the dash indicates the property class. In practical purchasing terms, 70 means a minimum tensile strength level of about 700 MPa, while 80 means about 800 MPa.<\/p>\n\n\n\n

Grade<\/th>Common Material Group<\/th>Strength Class<\/th>Typical Use<\/th><\/tr><\/thead>
A2-70<\/td>304-type stainless<\/td>700 MPa class<\/td>General machinery, indoor, light outdoor use<\/td><\/tr>
A4-70<\/td>316-type stainless<\/td>700 MPa class<\/td>Marine, humid, chemical, outdoor use<\/td><\/tr>
A4-80<\/td>316-type stainless<\/td>800 MPa class<\/td>Higher-load corrosion-resistant assemblies<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

For load-bearing applications, buyers should compare stainless grades with high-strength fasteners<\/a> before replacing carbon steel bolts with stainless steel.<\/p>\n\n\n\n

A2-70 vs A4-70<\/h2>\n\n\n\n

Corrosion Resistance Is the Main Difference<\/h3>\n\n\n\n

A2-70 is suitable for many general industrial uses. It performs well in dry indoor environments and moderate outdoor exposure.<\/p>\n\n\n\n

A4-70 is better where general corrosion risk is higher. It is often selected for marine hardware, food processing equipment, coastal structures, and chemical plant applications.<\/p>\n\n\n\n

For non-stainless coating alternatives, buyers can also review various coated fasteners<\/a>.<\/p>\n\n\n\n

A4-70 vs A4-80<\/h2>\n\n\n\n

Same Corrosion Family, Higher Strength Class<\/h3>\n\n\n\n

A4-80 provides higher tensile strength than A4-70, while still using the A4 stainless group. It is useful where both corrosion resistance and higher mechanical performance are required.<\/p>\n\n\n\n

However, A4-80 should not be selected blindly. Confirm tightening method, nut matching, galling risk, thread fit, and inspection report requirements.<\/p>\n\n\n\n

Common Buyer Mistakes<\/h2>\n\n\n\n

Avoid these issues:<\/p>\n\n\n\n

    \n
  1. Assuming stainless steel is always stronger than alloy steel.<\/li>\n\n\n\n
  2. Using A2 in strong chloride exposure.<\/li>\n\n\n\n
  3. Ordering \u201c316 bolts\u201d without property class.<\/li>\n\n\n\n
  4. Mixing A4 bolts with unsuitable nuts or washers.<\/li>\n\n\n\n
  5. Ignoring galling during stainless assembly.<\/li>\n\n\n\n
  6. Forgetting MTC and batch traceability for project orders.<\/li>\n<\/ol>\n\n\n\n

    For standard stainless bolts, start from standard fasteners<\/a>. For special lengths, threads, or head styles, use custom non-standard fasteners<\/a>.<\/p>\n\n\n\n

    Final Advice<\/h2>\n\n\n\n

    A2-70, A4-70, and A4-80 are not just material names. They combine stainless steel group and strength class.<\/p>\n\n\n\n

    Choose A2-70 for general corrosion resistance, A4-70 for stronger corrosion resistance, and A4-80 where higher strength is also required. Always confirm size, thread, nut, washer, application environment, and test documents before orderng.<\/p>","protected":false},"excerpt":{"rendered":"

    Stainless steel bolt grades are often misunderstood in purchasing. Buyers may ask for \u201c304 stainless bolts\u201d or \u201c316 stainless bolts,\u201d but the actual fastener marking often appears as A2-70, A4-70, or A4-80. These markings tell two things: the stainless steel group and the mechanical property class. Both matter. What A2 and A4 Mean Stainless Steel […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[479],"tags":[504],"class_list":["post-6904","post","type-post","status-publish","format-standard","hentry","category-fastener-knowledge-library","tag-strength-grades-mechanical-properties"],"acf":[],"_links":{"self":[{"href":"https:\/\/xzfastener.com\/ru\/wp-json\/wp\/v2\/posts\/6904","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/xzfastener.com\/ru\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/xzfastener.com\/ru\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/xzfastener.com\/ru\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/xzfastener.com\/ru\/wp-json\/wp\/v2\/comments?post=6904"}],"version-history":[{"count":1,"href":"https:\/\/xzfastener.com\/ru\/wp-json\/wp\/v2\/posts\/6904\/revisions"}],"predecessor-version":[{"id":6905,"href":"https:\/\/xzfastener.com\/ru\/wp-json\/wp\/v2\/posts\/6904\/revisions\/6905"}],"wp:attachment":[{"href":"https:\/\/xzfastener.com\/ru\/wp-json\/wp\/v2\/media?parent=6904"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/xzfastener.com\/ru\/wp-json\/wp\/v2\/categories?post=6904"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/xzfastener.com\/ru\/wp-json\/wp\/v2\/tags?post=6904"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}