How to check the grade of 304 or 202 stainless steel?

Update: 28-03-2020

The main differences between 202 and 304 stainless stee […]

The main differences between 202 and 304 stainless steels are both nickel and chromium. 202 has 16-18% chromium and 0.5-4.0% nickel, while 304 has 18-20% chromium and 8-10.5% nickel. Carbon content (0.08% in 304, 0.12% in 202), manganese (2% in 304, 5.5-7.5% in 202) have small differences, and there are slight differences in silicon, phosphorus and molybdenum content.

Both are austenitic steels, which are basically non-magnetic, but temporarily become magnetic by processing them. Manganese, like nickel, helps maintain the austenite phase in the steel. I can see that some 202 steels are magnetic because they contain less nickel. Although they have poor corrosion resistance and low toughness, the use of 304 in kitchenware and food processing can provide a cheaper alternative to 304. (Especially in the case of higher nickel prices).

202 and 304 are both non-magnetic austenite and cannot be distinguished using magnetic testing. The "200 series" is a Cr-Ni alloy with a higher manganese content but a lower nickel content than the "304 series". Can do spot inspection of manganese. Can also identify 202 and 304 stainless steel with portable analysis equipment based on spark emission or X-ray fluorescence spectroscopy