I The simple way is to use a magnet to attract. “Those that can suck well are generally iron screws, while those that are not easy to suck are generally stainless steel.”. Although stainless steel has a weak magnetic conductivity after processing, the difference between its magnetic conductivity and that of iron is still significant
II Use special reagents for testing. This is also a very common and extremely low-cost method.
III The scientific and accurate method is the material spectrum analyzer. The composition of each material is different, and using dedicated equipment to detect it is rigorous and scientific.