|Axe heads axe heads rolly polly axe heads
||[May. 12th, 2004|11:51 pm]
Ok, got the first axe head completely forged. Took an additional hour, but the eye is shaped, the edge is beveled, and the axe head is now annealing.
Given the stresses induced by the forging, not to mention the grain growth induced by the extremely high heat of forge welding the edge on, I first normalized the blade twice. This is done by heating to the critical point, the point at which you could harden the blade by quenching rapidly, or anneal the blade by cooling very slowly. Instead of either of these options, however, to normalize you heat to critical and air cool (note, this only works on water and oil-cooled steels, air cooled steels will harden when "quenched" in air.) Normalizing avoids the nose of the time/temperature curve, so the steel doesn't harden, but it does cool faster than annealing would require. So, the crystaline structure reforms, breaking up any large crystals that may have formed due to high heat, while also releaving some of the stresses from the forging. Doing this twice will be enough to resize the grain. You'll still have residual stresses, however, so annealing is required to render the work stress free.
Annealing is done by first heating the metal to critical, then slowly cooling, so slow that not only does the steel recrystalize, but the carbon actually goes out of solution, resulting in a very soft and stress-free steel (wish it was that easy in real life). Professionals use a temperature controlled oven that can be programmed to ramp down temperatures slowly, often at the rate of 50 deg F. an hour or so. More primitive methods are still quite effective for the simpler steels, such as the 1050 that I used for the edge of the axe. At .50% carbon (1/2 of 1 percent) this is a very simple steel. Heating to critical then burying the piece in vermiculite, ash, or, as I did, leaving it in the hot forge while that cools down is quite effective.
Tomorrow, I hope to finish off the 2nd axe forging-wise. That is the one I started at the Demo from two weeks ago. I have the handles (cherry) already shaped, the bark trimmed off, and sitting in the vacuum chamber drying overnight. Tomorrow I'll go ahead and stabilize them (not period, but it will make the wood last a lot longer, plus keep the wood from splitting and so on.)
I've got some pics I'll upload over the weekend, that should keep those of you interesetd in such things happy.