How to identify the authenticity of special stainless steel materials

Stainless steel is increasingly popular for its beautiful appearance, corrosion resistance, durability, and safety. For example, all food processing machinery currently in use is made of stainless steel, unless otherwise specified by the customer. Our company manufactures double-layer pots made of stainless steel, available in 304 and 316 stainless steel.

Stainless Steel Double-Layer Pots

After purchasing a double-layer pot and receiving it, how can we confirm whether the pot body is made of the material we desire? The following are some ways to distinguish common stainless steel:

(Sensory)

1. Color Difference

Stainless steel that has been pickled has a smooth, silvery-white surface. Chromium-nickel stainless steel is silvery-white with a hint of tawny; chromium stainless steel is white with a slightly grayish luster; and chromium-manganese-nitrogen stainless steel has a similar, slightly lighter color. Unpickled stainless steel has a more heavily oxidized surface: chromium-nickel steel is brownish-white; chromium steel is brownish-black; and chromium-manganese-nitrogen stainless steel is black. Cold-rolled, unannealed chromium-nickel stainless steel has a silvery-white, reflective surface. Stainless steel, except for raw steel, generally turns white after pickling.

2. Identification using copper sulfate: Remove the oxide layer from the steel, place a drop of water on it, and rub it with copper sulfate. If it does not discolor, it is generally stainless steel. If it turns purple-red, it is non-magnetic, high-manganese steel; magnetic steel is generally ordinary steel or low-alloy steel. 3. Identification with a Magnet

A magnet can generally distinguish between the two types of stainless steel. This is because chromium stainless steel is attracted to magnets in any state. Chromium-nickel stainless steel is generally nonmagnetic in the annealed state, but some may become magnetic after cold working. However, high-manganese steel with a high manganese content is nonmagnetic. The magnetic properties of chromium-nickel-nitrogen stainless steel are more complex: some are nonmagnetic, some are magnetic, and some are nonmagnetic longitudinally but magnetic transversely. In summary, while magnets can generally distinguish between chromium and chromium-nickel stainless steels, they cannot accurately distinguish between some steel grades with special properties, let alone specific steel grades.