SS316 316 Stainless Steel Pipe Rectangular Tubing 0.5mm Thick

The test of stainless steel

The magnet test is NOT a correct way to verify stainless steel. Stainless steel is graded by the ingredients and percentages. Stainless is a man made alloy. The nickel content determines the grade of stainless. The chromium content must be 18% or more to be 304 stainless. It starts out as non-magnetic. After a 500 ton press squeezes the nickel it changes the distribution of the nickel. The same is true where the die cuts the stainless increasing the possibility that rust will eventually occur there. All stainless steel is magnetic except austenitic stainless steel which is actually 300 series stainless such as 304 and 316. However, 300 series stainless is non-magnetic only after it is freshly formed. 304 is almost for sure to become magnetic after cold work such as pressing, blasting, cutting, etc. Initially the cold work causes the stainless to pick up foreign particles such as free iron. Then at some spots the metallic crystal structure changes from austenite to martensite. 400 series stainless (ie. martensitic stainless steel) is magnetic. Stainless steel containing more nickel (310 and 316 grades) is more likely to remain non-magnetic after cold work.

316 Stainless Steel Pipe Specification

Elemental comparison of the different materials