Causes and elimination of ferromagnetism in austenitic stainless steel

Generally speaking, the most difficult way to test whether a material is stainless steel is to see whether a magnet can adsorb or not, and that it is stainless steel, which is not familiar with the performance of stainless steel. In fact, this method is very one-sided and unscientific.

Austenitic stainless steel is austenitic stainless steel at room temperature. Chromium is about 18%, nickel is about 8%-10%, and carbon is about 0.1%, so it has a relatively stable austenite structure. Chromium manganese austenitic stainless steel is developed on the basis of chromium nickel austenitic stainless steel, adding manganese or nitrogen to stainless steel to replace the precious metal nickel element. The austenite element in the tissue has nitrogen besides manganese, and also has a suitable amount of nickel. Manganese plays an important role in stabilizing austenite in stainless steel.

Generally speaking, austenitic stainless steel is not magnetic or weak magnetic, but some austenitic stainless steel is not necessarily a complete austenitic structure, so some austenitic stainless steel will show weak magnetic. Martensitic stainless steel and ferritic stainless steel are magnetic, which is due to the ferromagnetism of martensite and ferrite structure. Therefore, only when the permeability of the austenite stainless steel is close to 1 in the vacuum, the austenite stainless steel is close to nonmagnetic R.

The reason for the formation of magnetism of stainless steel is that the segregation of stainless steel billet or improper heat treatment will lead to the formation of a small amount of martensite or ferrite in austenite stainless steel, which will have weaker magnetic properties.

After cold processing, the microstructure of stainless steel will be partly transformed into martensite, and the greater the degree of cold working deformation, the more martensite transformation, the higher the corresponding magnetic.

When the stainless steel workpiece is machined, its edge is closely contacted with the high hardness carbon steel, so that it is made up of carbon steel at the edge of the working face to produce magnetism.

So how to eliminate the magnetic properties of stainless steel? First of all, to eliminate the magnetism of stainless steel completely, the stable austenite structure can be recovered by high temperature solution treatment so as to remove the magnetism. The concrete method is to heat up the stainless steel material to about 1050 degrees, and then use cold water to quench the carbide in the stainless steel.

The second is applying an alternating magnetic field decay, it can be used on DC demagnetization machine, a welding gun welding clamp at one end of the stainless steel material, the other end and then the other welding tongs clamped material diagonal, current decreases, and can be divided into several times; but the time can not be too long, and the number is not too otherwise, easy to burn machine.

Source: China Stainless Steel Pipe Manufacturer - Yaang Pipe Industry Co., Limited (www.yaang.com)