How to increase the surface hardness of stainless steel bars
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The existing stainless steel 304 shaft is 900 long and 80 thick. It is required that the surface be hardened locally to increase the hardness to HB190. Since it is too slender to be rolled, what is the appropriate way to handle this?
Surfaces are generally strengthened physically (through cold working hardening), such as by cold rolling or shot blasting; when strengthening the hexagonal sealing grooves on 304 and 316 sealing flanges, I used flat finger wheels and beveled finger wheels for rolling. The hardness after rolling is equivalent to HB180～190. The key is to determine what the required thickness of the hardened layer is. You can also control the carbon at an upper limit in advance, of course while ensuring that intergranular corrosion is not an issue.
Forging treatment is essential.
The surface finish may be poorer after rolling or spraying； The shaft is long, and it tends to deform after rolling ； The compaction layer is thin, 1-2 mm.
I support this topic; let’s all learn together and exchange ideas. . . For products, it is necessary to ensure not only the hardness of the surface but also the hardness of the internal structure. I don’t quite understand your request – do you just want to ensure surface hardness, or something else? When producing stainless steel bars, we usually need to select different stainless steel ingots for hot rolling or forging, based on the compression ratio of the stainless steel bars, in order to meet the customers’ requirements. The higher the compression ratio, the better the structural integrity, and the greater the hardness.
It’s difficult in the case of already finished shafts, as rolling or forging increases their hardness and changes their dimensions completely. It’s better to buy a raw bar and have it forged and processed again.