1. The magnetism of stainless steel is directly related to its metallographic structure

‌Austenitic stainless steel (such as 304, 316)‌

Theoretically, it is non-magnetic, but in actual production, it may produce weak magnetism due to cold processing (such as stamping, bending) or composition deviation. For example, 304 stainless steel may be magnetic after processing due to the partial conversion of austenite to martensite, but this does not affect its corrosion resistance.

Martensitic/ferritic stainless steel (such as 430, 420)‌

It is magnetic in itself and is often used for knives, fasteners, etc., but this type of material still belongs to the category of stainless steel. For example, a 430 stainless steel frying pan can be adsorbed by a magnet, but it is indeed a qualified stainless steel product.

2. Three major misunderstandings of magnet detection

‌False negative risk‌

Non-stainless steel materials such as zinc alloys and copper alloys are also non-magnetic and can be easily misjudged as "high-quality stainless steel".

False positive risk‌

Some inferior "stainless iron" (recycled steel demagnetization treatment) may be non-magnetic, but the anti-rust performance is extremely poor.

Ignore performance differences ‌

Corrosion resistance (such as 316>304>430) has no direct correlation with magnetism. Austenitic stainless steel is still better than magnetic ferritic stainless steel even with weak magnetism.

3. More scientific identification method ‌Professional testing ‌

Analyze the chromium and nickel content through a spectrometer (304 needs to contain 18% chromium and 8% nickel).

Observe the mark ‌

Regular products will be marked with the material (such as SUS304), avoid buying unmarked products.

Corrosion test ‌

Observe the rust condition by salt spray test or soaking in acidic solution (such as lemon juice).