Jerrod Miller

Tempering colors are not reliable at all. I find it best to ignore them completely. This is because they are created from an oxide layer being grown, and that is not just dependent on temperature, but also surface and atmosphere chemistry. What are you using to temper? If it is a kitchen oven or toaster oven, are you checking the temperature with a thermometer that isn't pre-installed in the unit? The built in thermometers are notoriously bad. Also, are you using anything else in the oven for thermal mass? How long are you tempering? You should be doing at least 2 cycles of at least 1

I'm thinking this is getting a bit off topic for this thread so if we really want to go further on this topic we should start a new thread. But to put it bluntly: Yes I have seen temper embrittlement and have broken the test bars (tensile, Charpy, and bend, as well as some actual broken parts) that failed with poor results due to it. Dozens of them. And only dozens because it is well understood by every metallurgist that it happens and we try to avoid it. It only occurs when something went wrong in the process. Could be the wrong HT program was used, bad weld procedure, or any number of

Your proof of concept/proof of process picture doesn't show anything to prove that it was good, let alone better than differentially hardening. Also, you skipped out on quoting the very next sentence from my post:

The book I was referencing it the ASM Heat Treater's Guide. I do not have Larrin Thomas' book. And yes...In theory shorter times at hotter temps can yield the same hardness as longer times at lower temps. This is a fairly dangerous game to play (but to be fair, this is done a lot in industry). Especially with steep curves it is best to avoid that practice. But when you are looking much later in the curve (note that the one you pictured is a log scale on the time axis) then you don't get nearly as much hardness loss for the same amount of hold time. (e.g. The first minute of

This is not normalizing. Normalizing requires a phase change. Keeping it below critical will help with stress relief, but won't do much for grain size reduction. This gets you a little bit of blue brittle martensite, which is bad. If you don't harden it you get a phase change gradient, which isn't too bad at all. Metallurgically speaking, your way is worse. Practically speaking though, I would doubt that it is significantly, or even measurably different. Unless of course you need a harder tang, then you have to do what you have to do. This is very import

This is a pinned thread, so I don't feel bad adding to it so long after the last post. I recently had the "opportunity" (it was necessary) to run a couple chunks of RR track on the spectrometer for work. They both came out as 1060. C~0.62 | Mn~0.73 | Si~0.11 | P~0.026 | S~0.030 | Cr~0.02 | Ni~0.06 | Cu~0.26 | Mo,V,Al, all else<0.01

One can want no Cr, but tolerate a certain level. But generally speaking you want a shallow hardening alloy, and there are many viable chemistry options that will achieve this goal. It is just that a little carbon goes a long way for depth of hardening.

Ii should also add that the aggressiveness of the acid used plays into things a bit, too. Generally speaking, a less aggressive acid is desired because it will be better able to show the differences for its preferred attack (you'll really see it eat at the martensite more than ferrite). If you get too aggressive of an acid then you won't really see the difference as much because it attacks everything quickly. Best analogy I can come up with is this: Imagine sitting next to a road. When you see a car go by at 90 miles per hour, then an hour later the same car passes at 100 mph. Could you

When you use acid to etch steel there are a couple things that come into play: Chemistry and energy. When we etch pattern welded steels, the chemistry difference is the big obvious difference. When you are etching things like a hamon (or other such hardening line, thin or wispy), you are looking at the energy difference. Martensite is a stressed lattice, and therefore is attacked first by the etchant, all other things being equal. So as others have mention with the different microstructures: your fully hardened (100% martensite) edge was readily attacked by the acid, the semi-hardened (mi

I went to show someone these and they are both currently out of stock/unavailable. Not sure if that means they sold out and will be back eventually, or if completely gone forever.

That is because you like to drink the tea afterwards, isn't it? Be honest.

Could be uneven cooling, too. The heating up to austenitic should have relieved all the stresses. Then again, if the grains weren't completely even (say from excessive growth in a single direction due to rolling), that could cause warping with even heating and cooling. So many variables! Isn't this fun?

Or something when wrong at some point after annealing and the bar got bent and re-straightened. At any rate, the bar should have been stress free after annealing, but something could have happened to introduce new stresses.

Have you tried normalizing it? The piece may well have stresses in it that you are causing to be imbalanced as you remove material. Normalize to remove stresses and see how it goes.

Have you checked out FABA yet?