There are many kinds of stainless steel; According to the structure classification at room temperature,there are Martensite body type, Austenite body type, ferritin body type and duplex stainless steel;The Austenitic type has no magnetism or weak magnetism, while the other types have strong magnetism.
Stainless steel butterfly valve CF8(304), CF8M(316), CF3(304L), CF3M(316L) are austenitic stainless steel is non-magnetic or weak magnetic, but in smelting will cause a small amount of martensite or ferrite structure reconnect together, and the distribution is not uniform, less about 5%, more about 40%, When the content is high, the casting becomes magnetic. However, the strength of the casting will be better if the ferrite content is higher.
At present, the technology for 100% austenization treatment in our country and in the world is not.In the solution treatment of austenitic stainless steel castings, the carbide is only dissolved into the austenite, which enhances the corrosion resistance of the castings. It is impossible to change the content of martensite or ferrite, and only makes the structure change a little, so it has little effect on reducing the magnetism.Blank in the process of cold processing will also be filled with a little magnetic.
The key to reduce the magnetism of stainless steel butterfly valve is to control the content of martensite or ferrite, the less the magnetic, or make their structure fracture, uniform distribution. Pipes and plates are produced by the billet after many times of heating, extrusion, cooling and other processes. This process has broken the structure of martensite and ferrite, and made their distribution very uniform, so the magnetic properties of pipes and plates are small or impenetrable.
Stainless steel butterfly valve, whether our country or the standard of other countries, there is no magnetic testing this, it is not used as the qualified standard of stainless steel. In particular, due to different reasons caused by the magnetic austenitic stainless steel, stainless steel and other materials of stainless steel, carbon steel magnetic is not the same level, that is to say, the magnetic austenitic stainless steel is always shown to be weak magnetic.
