How to increase 304 SS hardness
How to increase 304 SS hardness
(OP)
I need some advice. I have a 304 SS ball (25-39 Rc according to manufacturer spec.) in an application where chemical compatibility is of great importance. My problem is that the 304 is just to soft, the 440C works well, however it is not compatible with the chemistry. Is there a way that i can increase the hardness of the 304?





RE: How to increase 304 SS hardness
RE: How to increase 304 SS hardness
RE: How to increase 304 SS hardness
RE: How to increase 304 SS hardness
RE: How to increase 304 SS hardness
During cold-working some of the austenite (FCC), which isn't real stable in 304, changes to one of the forms of the much harder martensite (BCT, as in diamond, I think).
RE: How to increase 304 SS hardness
As Metalguy stated, the FCC structure in Type 304 stainless steel is not stable during deformation, and martensite is formed. Depending on the degree of deformation, the subsequent strain hardening can produce strength levels of 1200 MPa, which would be in the high 30's HRC. The following document has a good graph of mechanical properties vs. degree of cold working for Type 304:
http://www.aksteel.com/pdf/markets_products/stainless/austenitic/304_304L_Data_Bulletin.pdf
RE: How to increase 304 SS hardness
RE: How to increase 304 SS hardness
RE: How to increase 304 SS hardness
As Metalguy states, the strain hardening occurs throughout the cross-section provided that the strain is developed throughout the cross-section. Wrought stainless steels are cold-rolled various amounts without subsequent annealing to produce increased strength throughout the cross-section. Shot-peening or roller burnishing would produce a similar effect, but only on the surface.
RE: How to increase 304 SS hardness
Quite often customers request us to increase the hardness of 304, which I have normally declined hence my question in this thread.
To summarise in small cold worked components the hardness increases,
RE: How to increase 304 SS hardness
But there is no way *we* can tell if it would work for you because we know nothing about your environment.
RE: How to increase 304 SS hardness
RE: How to increase 304 SS hardness
Furula is correct about choice of materials. Carpenter has some autenitics that can achieve very high hardnesses by strain hardening with good corrosion resistance, but at a price.
RE: How to increase 304 SS hardness
RE: How to increase 304 SS hardness
See my predicament Thread330-24316
RE: How to increase 304 SS hardness
RE: How to increase 304 SS hardness
“Wherever components are subjected to severe wear and corrosion attack.” Also useful for duplex SS & some nickel-based alloys (best corrosion resistance is for ferrite-free alloys containing some molybdenum).
"Kolsterising is a case-hardening process primarily for austenitic stainless steels. Wear resistance and resistance to galling is improved, while corrosion resistance remains unchanged.
The process involves diffusion of carbon into the work piece surface without the formation of chromium carbides. Post treatment surface hardness is equivalent to between 70 and 74 HRc. Standard case depths offered are 22 or 33 microns."
No change in dimension, so the treatment could easily be used for existing product lines. It also eliminates the galling problem of SS, so sounds like a winner.
RE: How to increase 304 SS hardness
RE: How to increase 304 SS hardness