What Is The Difference Between SS 304 And SS 202
The major difference between the 304 and 202 stainless steels is the nickel and chromium content. Both are austenitic stainless steels. The 202 grade has 16% minimum chromium and 0.5% minimum nickel in the composition where the 304 has 18% minimum chromium and 8% minimum nickel. Both of the steels are non-magnetic. The tensile strengths for both the materials are similar at 515MPa while the yield strength is higher for the 202 material with 275MPa and the 304 has about 205MPa. Both the materials also have manganese, iron, silicon, nitrogen, carbon, phosphorus and sulfur in the composition.
Both the materials look similar when they have not rusted. The best visual clue is a spark test. When ground with a grinder, the sparks of 304 fly longer and are more reddish in color. This is due to the higher density of the material and the high nickel content. The 202 spark test would produce yellowish sparks that do fly to longer distances. The corrosion tests under sea water or sodium chloride would produce more rusting in the 202 material than in the 304 material.
The applications depend mainly on the requirement of the application. High strength and high corrosive applications use 304 instead of 202. But the 202 material is very cost effective compared to the 304 and it could be used where applicable. For applications like making gates that have to last longer, the 304 is preferred. The applications like kitchenware which are cleaned regularly can use the 202 material for less cost. Also, the corrosion resistance of 202 is low so that it has to be selected only with applications that have less corrosion risk.
Since the 202 material has much iron than the 304, it is easier to weld with. Preheating or post weld heating is not necessary and it could be welded with most traditional welding methods. The 304 can also be welded with most traditional welding methods but welding is harder compared to the 202 grade. In contrast, the 202 grade can have high chromium carbide precipitation and develop much intergranular particles which can result in localized corrosion.
The 304 material develops less intergranular corrosion and rust after welding. The 202 material is prone to corrosion at the welded joints where the 304 is less prone to corrosion at the welded joints compared to the 202 grade.
The 202 grade is definitely cheaper as it has less nickel component compared to the 304. The nickel component is over 10 times lower so that it has significant price reduction. The 304 material is costlier compared to the 202 but is one of the most used materials in the metal applications due to its cost effectiveness combined with strength and corrosion resistance.
The choice of materials depends on various factors. If the kitchenware needs to be cheap then the 202 material can be used. If the kitchenware needs to last longer with less corrosion, then the 304 materials would be the best choice. In general, the 202 material is used mostly for the kitchenware and applications.
| Grade | UNS No | Old British | Euronorm | Swedish SS | Japanese JIS | ||
| BS | En | No | Name | ||||
| 304 | S30400 | 304S31 | 58E | 1.4301 | X5CrNi18-10 | 2332 | SUS 304 |
| Grade | Elongation (% in 50mm) minimum | Strength of Yield 0.2% Proof (MPa) minimum | Strength of Tensile (MPa) minimum | Pipe Hardness | ||
| Rockwell B (HR B) maximum | Brinell (HB) maximum | |||||
| 304 | 40 | 205 | 515 | 92 | 201 | |
| Grade | C | Mn | Si | P | S | Cr | Mo | Ni | N | |
| 304 | min. | – | – | – | – | – | 18.0 | – | 8.0 | – |
| max. | 0.08 | 2.0 | 0.75 | 0.045 | 0.030 | 20.0 | 10.5 | 0.10 | ||
| ELEMENT | CONTENT (%) |
|---|---|
| Iron, Fe | 68 |
| Chromium, Cr | 17- 19 |
| Manganese, Mn | 7.50-10 |
| Nickel, Ni | 4-6 |
| Silicon, Si | ≤ 1 |
| Nitrogen, N | ≤ 0.25 |
| Carbon, C | ≤ 0.15 |
| Phosphorous, P | ≤ 0.060 |
| Sulfur, S | ≤ 0.030 |
