Alloy content and austentizing temperature

[Jason Fry]

Jason, did you try to austenitize the steel at 1475 °F after the normalization? or just went with 1525? If you did it i may have missed it, otherwise i suggest to try to stay at 1475 after a 1650 normalization (and refining cycles, of course)

I just did 1525 this time. I have no less than 35 ft of this steel left. I'd prefer 1475 or 1500 for a final austentization, but I NEED this one to work, having already spent way too much time on it and failing miserably with the customer watching. If I can get a good RC 60 tempered knife out of this deal and move on, that'd be great. I'll certainly keep tweaking it. Having the RC tester right there next to the oven makes it less complicated

Next round of blades was planning as you suggest. 1650/1575/1500/quench. If we're on track with the coarse spheroidization theory, ought to work like a charm.

 

[Willie71]

I just did 1525 this time. I have no less than 35 ft of this steel left. I'd prefer 1475 or 1500 for a final austentization, but I NEED this one to work, having already spent way too much time on it and failing miserably with the customer watching. If I can get a good RC 60 tempered knife out of this deal and move on, that'd be great. I'll certainly keep tweaking it. Having the RC tester right there next to the oven makes it less complicated

Next round of blades was planning as you suggest. 1650/1575/1500/quench. If we're on track with the coarse spheroidization theory, ought to work like a charm.

Good plan. You can make a good guess of the carbon content based on your best Austentize temp. If its closer to 1500, then you are euctoid. If its closer to 1450, you are hyper-euctoid (0.95C) My Hitachi White was Rc67 after 1440F. Its 1.1C.

I find this stuff fascinating. :thumbup:

Of course, Chromium and Nickel will throw things in their own direction.

 

[me2]

I really don't want to be nitpicky, but I wanted to point out that the hardening temperature is not a good indicator of eutectoidness or carbon content related to the eutectoid point. Eutectoid steels will reach full hardness anywhere from 1400 to 1500 degrees, though lower temps will take some finesse. I've seen reports of a Rockwell of 68 when quenched from 1375, though that was a VERY knowledgable individual with top notch equipment.

 

[Willie71]

I really don't want to be nitpicky, but I wanted to point out that the hardening temperature is not a good indicator of eutectoidness or carbon content related to the eutectoid point. Eutectoid steels will reach full hardness anywhere from 1400 to 1500 degrees, though lower temps will take some finesse. I've seen reports of a Rockwell of 68 when quenched from 1375, though that was a VERY knowledgable individual with top notch equipment.

This is something I extrapolated from a discussion with a well known metallurgist. If you go higher than optimum, you get too much carbon into solution, and get retained austentite decreasing hardness. Since increasing carbon content decreases the austentizing temp according to Verhoeven, it seems to reason that the higher the carbon, the lower the austentizing temp to prevent retained austentite. I have done experiments with W1, W2, Hitachi White, 15N20, and 52100. I have a sweet spot that works for each of these steels in my shop.

 

[samuraistuart]

Me2....just wanted to say thank you for that blurb about the eutectoid steel and 1375F hardening just fine. I thought that might be very possible..but wasn't sure.

 

[me2]

I don't know if I'd say it hardens fine. There are diffusion issues at that temperature. It takes some effort, even in the research piece I saw.

 

[me2]

This is something I extrapolated from a discussion with a well known metallurgist. If you go higher than optimum, you get too much carbon into solution, and get retained austentite decreasing hardness. Since increasing carbon content decreases the austentizing temp according to Verhoeven, it seems to reason that the higher the carbon, the lower the austentizing temp to prevent retained austentite. I have done experiments with W1, W2, Hitachi White, 15N20, and 52100. I have a sweet spot that works for each of these steels in my shop.

The austenizing temperature is only decreased up to the eutectoid point. After that, it goes back up, if you want full austenite, which hardly anyone does. After that point, the austenizing temperature depends on how much carbon you want in solution and how much carbide you want left over. As long as you're dealing with plain carbon steels, which the OP basically is, but you are not, you can find a good temperature and stick with it even as carbon content goes up. All that will happen is the amount of carbide will go up with carbon content, but not the amount of carbon in solution.