Austenitic stainless steel (represented by 304) magnetic properties

Aug 15


Marine Lee

Marine Lee

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In real life, most people think that stainless steel is not magnetic, and with the magnet to identify stainless steel, this method is very scientific. First, zinc alloy, copper alloy can generally imitate the appearance of stainless steel color, there is no magnetic, easy to mistakenly believe that stainless steel; and even our most commonly used 304 steel, after cold processing, there will be different degrees of magnetic, So can not just a magnet to judge the authenticity of stainless steel. So how does the magnetism of the stainless steel come from?


According to the study of material physics,Austenitic stainless steel (represented by 304) magnetic properties Articles the magnetic properties of the metal are derived from the structure of the electron spin, and the electron spin belongs to the quantum mechanical properties, either upwards or downwards. In ferromagnetic metals, electrons are automatically rotated in the same direction, and some of the antiferromagnetic metal materials are in the regular pattern, while the adjacent electrons move in opposite directions or antiparallel spin, but for triangular crystals In the case of electrons, since the two electrons in each triangle must spin in the same direction, the spin structure is no longer present. In general, austenitic stainless steel (represented by 304) is non-magnetic, but may also be weakly magnetic, and ferrite (mainly 430, 409l, 439 and 445nf, etc.) and martensite As a representative) are generally with a magnetic. Stainless steel which has some steel (such as 304, etc.) classified as non-magnetic stainless steel "refers to its magnetic indicators below a certain value only, that is, generally stainless steel are more or less with a certain magnetic. It is mentioned that the austenite is non-magnetic or weak magnetic, and ferrite and martensite is magnetic, due to smelting component segregation or improper heat treatment, will cause austenitic stainless steel in a small amount of martensite or iron The 304 stainless steel is cold-processed, the structure will also be transformed into martensite, the greater the deformation of cold working, the greater the transformation of martensite, the magnetic will be stronger. Think.Therefore, 304 stainless steel will appear weak magnetic. To completely eliminate the magnetic properties of 304 stainless steel can be restored by high temperature solution to stabilize the austenite structure, thus eliminating the magnetic, so the magnetic properties of the material is the arrangement of the rules and the electron spin of the co-directional decision, we think The physical properties of the material, and the corrosion resistance of the material is determined by the chemical composition of the material is the chemical properties of the material, and whether the material has nothing to do with the magnetic.

From the stainless steel development prospects, 400 series instead of 300 series can be described as the trend. The 200 series of materials because of scrap recycling is facing many difficulties, the Department of non-environmentally friendly stainless steel, if the increase in the use of the steel is not conducive to the sustainable development of the entire stainless steel industry, so now many foresight of large enterprises are to 200, and look to the more potential for the development of 400 series of stainless steel. People often think that the magnet adsorption of stainless steel, to verify its advantages and disadvantages and authenticity, do not smoke non-magnetic, that is good, genuine; suction magnetic, is considered counterfeit fake. In fact, this is a very one-sided, unrealistic way to identify the wrong. A wide range of stainless steel, according to the organizational structure at room temperature can be divided into several categories

1. Austenitic type such as 304,321,316,310;
2. Martensitic or ferrite type such as 430,420,410;

Austenitic type is non-magnetic or weak magnetic, martensite or ferrite is magnetic. Most of the stainless steel commonly used as decorative tube sheet is austenitic 304 material, generally magnetic or weak magnetic, but due to smelting caused by chemical composition fluctuations or processing status may also appear magnetic, but this can not be considered fake or unqualified, what is the reason for this? The above mentioned austenite is non-magnetic or weak magnetic, and martensite or ferrite is magnetic, due to smelting component segregation or improper heat treatment, will cause austenitic 304 stainless steel in a small amount of martensite or iron Body tissue. In this way, 304 stainless steel will be with a weak magnetic. In addition, 304 stainless steel after cold processing, the structure will be transformed into martensite, cold forming the greater the degree of deformation, the greater the transformation of martensite, steel, the greater the magnetic. As a batch of steel, production Φ76 tube, no obvious magnetic induction, production Φ9.5 tube. Due to Ling bending deformation of the larger magnetic sense is obvious, the production side of the rectangular tube deformation than the tube, especially the corner part of the deformation is more intense magnetic more obvious. In order to completely eliminate the above-mentioned causes of the 304 steel magnetic, can be recovered by high temperature solution to stabilize the austenite structure, thereby eliminating the magnetic. In particular, it is due to the above reasons caused by the 304 stainless steel magnetic, with other materials of stainless steel, such as 430, carbon steel is not the same level of magnetic, that is, 304 steel magnetism always shows the weak magnetic. This tells us that if the stainless steel with weak magnetic or completely without magnetic, should be judged as 304 or 316 material; if the magnetic properties of carbon steel, showing a strong magnetic, because the judge is not 304 material.