Photo by Alex Urezkov on Pexels
Reference for the stainless steel grades most commonly specified in UK engineering, cross-referencing AISI (American) and EN (European) designations. Stainless Steel Grades Reference Values are for solution-annealed plate unless noted. Fastener grades A2-70 and A4-80 follow ISO 3506, with the number indicating minimum tensile strength in units of 100 MPa.
| Grade (EN/AISI) |
Type |
Composition |
Typical Use |
Tensile (MPa) |
Yield (MPa) |
Corrosion Resistance |
| 304 / 1.4301 |
Austenitic |
18Cr-8Ni |
General purpose, food, architectural |
520 |
215 |
Moderate |
| 304L / 1.4307 |
Austenitic |
18Cr-10Ni-0.03C |
Welded fabrications, no sensitisation |
485 |
170 |
Moderate |
| 316 / 1.4401 |
Austenitic |
17Cr-12Ni-2Mo |
Marine, chemical, pharmaceutical |
520 |
215 |
High (chlorides) |
| 316L / 1.4404 |
Austenitic |
17Cr-12Ni-2Mo-0.03C |
Welded marine / chemical parts |
485 |
170 |
High (chlorides) |
| 321 / 1.4541 |
Austenitic |
17Cr-9Ni-Ti |
High temp up to 870C, aircraft exhaust |
515 |
205 |
Moderate |
| 2205 / 1.4462 |
Duplex |
22Cr-5Ni-3Mo |
Offshore, pressure vessels, high strength |
620 |
450 |
Very high |
| 2507 / 1.4410 |
Super Duplex |
25Cr-7Ni-4Mo-N |
Seawater, high chloride brines |
730 |
530 |
Excellent |
| 17-4 PH / 1.4542 |
Precipitation hardening |
17Cr-4Ni-Cu |
High-strength shafts, aerospace |
930 |
860 |
Moderate |
| A2-70 |
Austenitic (fastener) |
Based on 304 |
Bolts/nuts general purpose |
700 |
450 |
Moderate |
| A4-80 |
Austenitic (fastener) |
Based on 316 |
Marine-grade bolts/nuts |
800 |
600 |
High (chlorides) |
| 430 / 1.4016 |
Ferritic |
16Cr |
Automotive trim, domestic appliances |
450 |
250 |
Low |
How to choose a stainless steel grade
For most general engineering, 304 (EN 1.4301) is the default - it handles atmospheric corrosion and food contact at a reasonable price. Switch to 316 (EN 1.4401) whenever chlorides are present: seawater, de-icing salt exposure, swimming pools, chemical plants. The added molybdenum resists pitting corrosion.
Use the L (low carbon) variants - 304L, 316L - when parts will be welded in sections over 5 mm thick. Normal 304 and 316 can suffer carbide precipitation at the weld heat-affected zone, leaving it vulnerable to intergranular corrosion. L grades keep carbon below 0.03% to prevent this.
Duplex grades (2205, 2507) offer double the yield strength of standard austenitic grades and excellent chloride resistance, but cost 30-50% more and are harder to weld. Specify duplex only when corrosion or strength requirements justify it.
For fasteners, A2 (equivalent to 304) covers most general use. A4 (equivalent to 316) is needed for marine and chemical applications. The number after the dash (70, 80) is the minimum tensile strength: A2-70 = 700 MPa, A4-80 = 800 MPa.
Related standards
- BS EN 10088-1 - Stainless steels: list of grades
- BS EN 10088-2 - Stainless steels: sheet, plate, and strip
- BS EN 10088-3 - Stainless steels: bars, rods, wire, and sections
- ISO 3506-1 - Fasteners: mechanical properties of stainless steel bolts
- ASTM A240 - Chromium and chromium-nickel stainless steel plate
Stainless fasteners + tools
Shop the exact parts and tools referenced above on Amazon UK. Prices, stock, and delivery times update live; MLC earns a small commission on qualifying purchases at no cost to you.
As an Amazon Associate, MLC earns from qualifying purchases. The product links on this page support our work at no extra cost to you.
Frequently Asked Questions
What is the difference between 304 and 316 stainless steel?
316 contains 2% molybdenum, which gives it much better resistance to chloride-induced pitting corrosion. 304 handles atmospheric corrosion and food contact at lower cost, but fails in marine or salt-exposed environments. For any chloride or seawater exposure, specify 316.
What does A2-70 mean on a stainless bolt?
A2-70 means austenitic stainless steel (typically grade 304) fastener with 700 MPa minimum tensile strength. A4-70 and A4-80 use 316-equivalent composition for marine environments. The number after the dash is tensile in units of 100 MPa.
When do I need low-carbon (L) stainless grades?
Specify 304L or 316L for welded fabrications in sections over 5 mm thick, and for any stress-corrosion-sensitive environment. Standard 304 and 316 can form chromium carbides at the heat-affected zone during welding, which leaves that region vulnerable to intergranular corrosion. L grades keep carbon below 0.03% to prevent this.
What does the Stainless Steel Grades Reference provide for UK engineers?
The Stainless Steel Grades Reference provides a cross-referenced list of stainless steel grades commonly used in UK engineering, listing both AISI and EN designations. It includes details such as composition, typical uses, mechanical properties like tensile strength (MPa), and corrosion resistance.
What are the main types of austenitic stainless steels listed in the Stainless Steel Grades Reference?
The reference lists common austenitic grades including 304 / 1.4301 with a composition of 18Cr-8Ni, 304L / 1.4307 which is similar but with lower carbon content to prevent sensitisation, and 316 / 1.4401 with added molybdenum for better chloride resistance.
How can engineers choose the right stainless steel grade based on the Stainless Steel Grades Reference?
Engineers should consider the specific application requirements such as corrosion environment and mechanical properties when selecting a grade from the reference. For example, 316 / 1.4401 is preferred for marine applications due to its high chloride resistance.
What standards does the Stainless Steel Grades Reference follow for fastener grades?
Fastener grades A2-70 and A4-80 are specified in ISO 3506, where the number indicates minimum tensile strength in units of 100 MPa. This is noted on the reference table to help engineers understand compliance with international standards.
Are there UK suppliers listed for the stainless steel grades mentioned in the Stainless Steel Grades Reference?
While specific supplier details aren't provided, the reference guides engineers to local UK suppliers and manufacturers who stock these standard grades such as 304 / 1.4301 and 316 / 1.4401.
What is the typical tensile strength of grade 304 stainless steel according to the Stainless Steel Grades Reference?
The reference indicates that grade 304 (EN designation 1.4301) has a solution-annealed plate with a typical tensile strength of 520 MPa, making it suitable for general purpose applications requiring moderate corrosion resistance.
How does the cost and availability compare between 304L and 316 grades in the Stainless Steel Grades Reference?
Generally, grade 316 is more expensive than 304L due to its higher alloy content, specifically molybdenum which provides enhanced corrosion resistance. Availability may vary depending on specific application needs within UK engineering contexts.