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                        Why Stainless Steel Tapes Magnetism

                        2019-06-04

                        We often think that magnets adsorb stainless steel, verify its merits and demerits, do not absorb non-magnetic, think it is good, the real price; magnets, it is considered fake. In fact, this is an extremely one-sided and unrealistic method of identifying errors.

                        There are many kinds of stainless steel, which can be divided into several types according to the structure at room temperature.

                        Austenite type: 304, 321, 316, 310, etc.

                        Martensite or ferrite type: 430, 420, 410, etc.

                        Austenite type is non-magnetic or weak magnetic, martensite or ferrite is magnetic.

                        _stainless steel used as decorative tubesheet is mostly 304 austenitic material. Generally speaking, it is non-magnetic or weak magnetic. However, because of the fluctuation of chemical composition or different processing conditions caused by smelting, it may also appear magnetic, but this can not be considered as fake or unqualified. What is the reason?

                        _The above mentioned austenite is non-magnetic or weak magnetic, while martensite or ferrite is magnetic. Due to the segregation of composition or improper heat treatment during smelting, a small amount of martensite or ferrite in Austenitic 304 stainless steel will be formed. In this way, 304 stainless steel will have a weak magnetism.

                        In addition, 304 stainless steel after cold processing, the structure will also transform to martensite, the greater the deformation degree of cold processing, the more martensite transformation, the greater the magnetism of steel. Like a batch of steel strips, production of 76 tubes, no obvious magnetic induction, production of 9.5 tubes. Because the cold bending deformation is larger, the magnetic induction is more obvious. Because the deformation of square rectangular pipe is larger than that of circular pipe, especially in the corner part, the deformation is more intense and the magnetism is more obvious.

                        In order to completely eliminate the magnetism of 304 steel caused by the above reasons, the stable austenite structure can be restored by solution treatment at high temperature, thus the magnetism can be eliminated.

                        In particular, the magnetism of 304 stainless steel caused by the above reasons is totally different from that of other stainless steels, such as 430 and carbon steel. That is to say, the magnetism of 304 steel always shows weak magnetism.


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