Because industrial stainless steel pipe is divided into many types: 201,202,301,304,316, and the elemental nickel is magnetic. Which 201,202 nickel in general about 4, so the general magnet generally sucked no feeling. And 301,304,316, the higher the nickel content, the corresponding magnetic greater. And then one of these models can also be used to "add manganese" to weaken the magnetic, so that there is no magnetic are not necessarily.