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A lesson, for myself, for today.
A lesson, for myself, for today - Don't put all your trust in the sparks!
Although sparks can be useful in determining the approximate Carbon content of steel, don't bet the farm on it! Here are the sparks from the steel of my most recent smelt. The finished steel gave off great sparks. I would have guessed it had a lot of Carbon. Yet, the steel proved to be very shallow hardening. Quenching in water gave hardnesses of about 56HRC in a very narrow band. Quenching in brine brought it up to 58.5HRC. Frustrated by the low hardness, even though I had great sparks, it was time to bring out the microscope.
A sample, normalized at 1575F, was polished and etched in 2% Nital. The results are pretty clear. I made some very clean 0.40 - 0.45% Carbon Steel. It would be great for a lot of things, just not for straight razors.
It is amazing how such little things will change the results of a smelt. My only recent change was the source of my charcoal. But, this charcoal is so good, I don't want to go back to the commercial stuff. For now, it's back to tweaking rates and ratios, until I get the Carbon content back up. Until then, I will be flattening, quenching, and sorting my bloom material - Japanese style. I'm also thinking about tinkering with an Aristotle furnace...
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