J.Arthur Loose Posted January 9, 2011 Share Posted January 9, 2011 So I've completed and played with my low-temp salt tank to compliment the high one. Whee! It heats very evenly. Quenching into it is really anti-climactic. Nothing happens! I was expecting violent bubbling and boil over. I'm having a little trouble nailing down some facts with regards to martempering 15N20/1075. The first being if it's even a good idea due to the slightly hypoeutectoid nature of those steels. I do hear that oil quenching steels will martemper, and both of these are arguably oil quenchers, at least at blade dimensions. I certainly *could* simply quench in 150F Parks #50, clean up and temper in the low temp salt... the primary function here is escaping my kitchen oven's 28.5" diagonal length limitation. However, if possible, I'd love to enjoy some warpage reduction and convenience with my new toy tool, in steel materials I have in spades. For experimentation's sake, I heated a piece of the aforementioned combination up to 1455F and quenched it into 500F salt. The piece felt like it hardened a little as it cooled, but didn't seem to fully harden on reaching room temperature. I lowered the temp to 400F and tried again with somewhat better results. I tempered it for a half hour (it was midnight by this time...) at 525F or so, since Kevin Cashen in another forum suggested that martempering results might not be immediately perceptible until after tempering. I have a fairly springy piece, but I can bend it if I try, so again I think I missed something. I'll temper it some more this afternoon and see if that changes anything. It seems *different* than anything I've experienced, and it's possible this is simply what the material should be like, maybe I'll go for a more springy temper to see how the material responds. Current theories for better results include raising my initial heat temperature (I have been in the habit of keeping it low due to inequalities in the high temp salt tank which I think I have resolved, thus I think temps that used to average out above my internal thermocouple's reading are now reading more accurately...) I'm also variously thinking that 500 may have been too low, as evidence suggests that the Ms for .75C should be on the higher side; or that 400 may have been too high, as evidenced by some folks who claim to quench into 350F oil/salt. (Is this really martempering anymore?) I'm not finding good information on the Ms numbers for these materials. I note from searching here that Jake and Ben Potter have used 1075, going from 1500F to variously 475F and 375F, though of course, this may have changed since questions were posed in the forums. I did find a mention of a piece that Howard Clark "marquenched," online made of 15N20/1084, so I suppose anything is possible. Anyway, anyone have martempering experience with this combination? jloose.com Link to comment Share on other sites More sharing options...
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