Rule of Thumb for Determining Max Hardness of Steel? 2

[mxracer17788]

Is there a simple technique for determining the maximum hardness that steel can be processed to? If I have 1022 steel, how can I determine the max hardness value from carburizing or nitriding etc? Also, is there a way to create a localized alloy in a plain carbon steel through processing? In other words, if I have a thin rod (0.20" diameter) of 1022 steel and I want to make the left half of the rod similar to A-2 tool steel, is there a way to create a localized alloy in this area through processing? (Probably a dumb question but I thought I'd ask...). Also if I have a carburized tip of 1022 that will reach high service temperatures due to friction with steel, will this cause localized tempering in the hardened tip that will lower the hardness value? I'm assuming this isn't a problem with, say A-2 tool steel, but why?

 

[redpicker]

A simple rule of thumb is that steel can reach a maximum of about 65 HRC with rapid enough quenching. This requires a carbon content of around 0.80% or higher. This is also without any tempering; tempering will lower the hardness, but increase the ductility. The use of as-quenched (untempered) steel in not recommended. 1022 is a plain carbon steel with a nominal carbon content of 0.22%. With a 0.2" diameter rod, if carburized to 0.90-1.0% C, you might be able to achieve 55 HRC after tempering if your processing is controlled enough. You would have to mask the right half of the rod to prevent it from being carburized. Unless you need a high volume of these parts, I think I'd just get some hardened O1 drill rod.

The alloy elements in A2 tool steel (roughly 5% Cr, 1% Mo, .4% V) allow the steel to maintain its hardness during tempering and exposure to elevated temperatures. These elements also give the material it's air-hardening characteristics.

rp

 

[mxracer17788]

Awesome response RP much thanks! One more question, could nitriding, carbonitriding or some other surface heat treat process produce a case in 1022 that is harder than 55 HRC? I'm looking for a surface hardness of around 65 at 0.002" depth and a case of 55-60 at a depth of 0.004 to 0.009". Is this possible for 1022 steel by means of heat treatment? My goal is to form this tip into a steel cutting tool, and this is high volume application.

Thanks,
Jeff

 

[redpicker]

Yes, carbonitriding would be a process to investigate. Search for carbonitriding processers in your area and discuss your requirements with them, they should be able to be more specific as to their exact capabilities.

rp