chekc Difference Between A4 and A2 Stainless Steel
These are both austenitic stainless steel materials. The material composition is the primary difference that makes difference in the mechanical properties and other aspects of these materials. The a4 material has 16% chromium, 2% molybdenum and 10.5% nickel in the composition. The a2 material has 10.5% chromium in the composition. The a4 material has much corrosion resistance than the a2 material. The a4 grade material is used in marine grade applications mostly due to the higher corrosion resistance. The a4 material gets the high corrosion resistance due to the addition of molybdenum in the composition.
The materials are made from cold worked austenitic stainless steel under five different categories, A1 through A5. Each of the A grade also have sub grades such as A2-70 and A4-80. The numbers designated usually denote the minimum tensile strength in MPa. The A2-70 has 700MPa minimum tensile strength and the A4-80 has 800MPa minimum tensile strength as well.Both the materials have good temperature resistance up to 870 degrees Celsius.
Temperatures above this range can cause the formation of chromium carbide precipitation and reduce the corrosion resistance of the materials. However, the hardness of the materials could be improved by heating and cooling the material with the annealing methods. The annealing makes it possible to retain the strength, corrosion resistance and become harder so that it could be used in applications such as food production, transportation and other industries.
When it comes to a choice, the a2 grade is more general purpose material that can be used in domestic and general corrosive service applications. The a4 grade can be used in more corrosion prone applications such as marine, sea water, food grade and medical implants.
The visual identification is difficult except for printed markers on the products. The A2 and A4 grades of steels can be tested through various tests to find. A simple test would be to apply saline solutions and allow the materials to rest for 24 hours to see any rust or stain formation. The A2 material would form much stain quickly and the A4 material would not. Apart from that, there are other laboratory tests that can be carried out in any metallurgic laboratories.
The strength of these materials is similar. The A4 grade has 800MPa minimum tensile strength and 600MPa minimum yield strength. The A2 grade has 700MPa minimum tensile strength and 450MPa minimum yield strength. None of these materials could be heat treated to get more strength.
| GRADE | C | MN | P | S | SI | CR | NI | CU | |
|---|---|---|---|---|---|---|---|---|---|
| A2-70 | Min | - | - | - | - | - | 15.0 | ||
| Max | 0.1 | 2.0 | 0.05 | 0.03 | 1.0 | 20.0 | 19.0 | 4.0 | |
| 304 | Min | - | - | - | - | - | 18.0 | 8.0 | |
| Max | 0.08 | 2.0 | 0.045 | 0.03 | 0.75 | 20.0 | 10.5 | ||
| 304L | Min | - | - | - | - | - | 18.0 | 8.0 | |
| Max | 0.03 | 2.0 | 0.045 | 0.03 | 0.75 | 20.0 | 12.0 | ||
| 304H | Min | 0.04 | - | - | - | - | 18.0 | 8.0 | |
| Max | 0.10 | 2.0 | 0.045 | 0.03 | 0.75 | 20.0 | 10.5 |
Stainless Steel A4 Bolts
Stainless steel grade a2-80 Screws
stainless steel A2-80 Studs
IS 1367 grade a2-70 Nuts and Bolts
Grade A4 Stainless Steel Washer
| FASTENERS GRADE | SI | C | P | MN | S | MO | CR | NI | N | CU | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Max | ISO | 1.00 | 0.08 | 0.045 | 2.00 | 0.03 | 3.0 | 18.5 | 14.0 | - | 1.0 |
| Min | A4-70 | - | - | - | - | - | 2.0 | 16.0 | 10.5 | - | - |
| Max | ISO² | 1.00 | 0.03 | 0.045 | 2.00 | 0.03 | 3.0 | 18.5 | 14.0 | 0.22 | 1.0 |
| Min | A4-70 | - | - | - | - | - | 2.0 | 16.0 | 11.5 | 0.12 | - |
| Max | 0.75 | 0.08 | 0.045 | 2.0 | 0.03 | 3.00 | 18.0 | 14.0 | 0.10 | ||
| Min | 316 | - | - | 0 | - | - | 2.00 | 16.0 | 10.0 | - | |
| Max | 0.75 | 0.03 | 0.045 | 2.0 | 0.03 | 3.00 | 18.0 | 14.0 | 0.10 | ||
| Min | 316L | - | - | - | - | - | 2.00 | 16.0 | 10.0 | - | |
| Max | 0.75 | 0.10 | 0.045 | 0.10 | 0.03 | 3.00 | 18.0 | 14.0 | - | ||
| Min | 316H | 0 | 0.04 | - | 0.04 | - | 2.00 | 16.0 | 10.0 | - |
