SS 304 Material Became magnetic after Formning?
SS 304 Material Became magnetic after Formning?
(OP)
Hello All
After forming Dish Head the SS 304 material became magnetic. I know Austenitic SS are not magnetic.
We doubted on the source of material and conucted re chemical analysis. The chemistry perfectly agrees with the material Spec SA 240- 304 not only that it perfectly matches the certificate.
Now why should the material which was non magnetic turn magnetic.
Had i performed Micro analysis before forming (Now also possible to perform since balance cut pieces of dish blank is availale) i would have seen Austenitic. What would i see in micro examination, Would i see Ferrite or martensite. If so how does this happen?
Would my ferrite scope show different reading in unformed plate and formed dish.
The problem with ferrite scope is that it shows various readings on the same plate.
After forming Dish Head the SS 304 material became magnetic. I know Austenitic SS are not magnetic.
We doubted on the source of material and conucted re chemical analysis. The chemistry perfectly agrees with the material Spec SA 240- 304 not only that it perfectly matches the certificate.
Now why should the material which was non magnetic turn magnetic.
Had i performed Micro analysis before forming (Now also possible to perform since balance cut pieces of dish blank is availale) i would have seen Austenitic. What would i see in micro examination, Would i see Ferrite or martensite. If so how does this happen?
Would my ferrite scope show different reading in unformed plate and formed dish.
The problem with ferrite scope is that it shows various readings on the same plate.





RE: SS 304 Material Became magnetic after Formning?
Cold working 304 will cause to become magnetic.
RE: SS 304 Material Became magnetic after Formning?
RE: SS 304 Material Became magnetic after Formning?
Many austenitic stainless steels like Type 302, 304, etc. are only metastable, that is, upon deformation some of the austenite transforms into martensite. The martensite makes the stainless steel somewhat magnetic. This topic has been covered on Eng-Tips before, so try a search for more information.
RE: SS 304 Material Became magnetic after Formning?
RE: SS 304 Material Became magnetic after Formning?
The reason your magnetometer gives different readings in different areas is because you have differing levels of strain hardening in different areas. If you mapped it, you'd find it will conform quite closely to the amount of deformation in the given area I'd bet.
RE: SS 304 Material Became magnetic after Formning?
If i put a portable microscope on the dish head would i see martensite at least in some locations?
Does it mean that if an austenitic material is formed or hammered severely and then we put it under micoscope we will see phase change to martensite?
RE: SS 304 Material Became magnetic after Formning?
A metallographic sample will show the phase change via the use of one of many etchants:
Ralph's Reagent
Vilella's Reagent
... to name a few.
RE: SS 304 Material Became magnetic after Formning?
As Flesh mentioned, you will need to create a polished metallographic section and then etch this in order to see the martensite. The microscope will need to have a magnification of at least 100x in order to resolve the martensite, which will have a needle-like appearance.
RE: SS 304 Material Became magnetic after Formning?
Further with cold working one can make even Austenitic material magnetic as the material would transform into martensitic after cold forming.
RE: SS 304 Material Became magnetic after Formning?