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In general, the castings produced by the use of 304 stainless steel, which are not magnetic, are micro - magnetic. What is the cause? Because:
1, the chemical composition equivalent component control is not in place.
Between manufacturers in order to reduce the cost of the Ni control of the lower limit of 8.0-8.2%, there is a certain amount of Cr/Ni reaches a certain value of the steel structure of ferrite, ferrite is magnetic; then using 1050~1080 C solution treatment can be completely dissolved in austenite ferrite will not have a magnetic.CNC Turning Aluminum Electroplate Part OEM&ODM
2. Cold working hardening.
When the austenitic stainless steel produces deformed martensite during cold processing, the deformation martensite increases the strength of the stainless steel, and the deformed martensite is magnetic. The deformed martensite can be disappearing by solid solution treatment and even annealing, but the strength of the steel will decrease.
The following degaussing method can be adopted if the cold working strength is guaranteed, and the weak magnetic or even non magnetic:
1, according to the phase diagram principle, reduce the Cr/Ni value, especially increase the Ni and Mn content to the upper limit. Before cold processing, the upper limit of solid solution treatment is carried out, the grain degree is controlled by 4 stages under the premise of ensuring the surface, and the magnetic properties of cold processing can be reduced.
2, the general 304 cold processing has a certain weak magnetic. After knocking or other impact, the austenite structure is transformed into martensite, and there will be some magnetism at this time. Heat to 1050 degrees, and then water quenched cold, can eliminate magnetic.Brass Sand Blast Custom Cnc Machining Part OEM&ODM
1. The understanding that "Cr/Ni reaches a certain value": This is the ratio of 2 equivalent.
Cr equivalent =Cr%+1.5 (Si%) +Mo%+Cb%-4.99
Ni equivalent =Ni%+30 (C%) +0.5 (Mn%) +26 (N%-0.02) +2.77
When the Cr equivalent /Ni equivalent <0.9 reaches the single austenite, there will be no magnetic.
2. The effect of adding nickel, adding manganese, adding nitrogen, reducing chromium, reducing silicon and so on can all achieve the effect of degaussing.
3, there is a "alloy degaussing agent" in the market, which can convert the residual ferrite in stainless steel into austenite, and it can also achieve the effect of degaussing. At the same time, the alloy degaussing agent is added to the corrosion resistance of the casting casting and the effect of salt spray test is good.