(I try to use science in speech as sparingly as possible and only when it's absolutely necessary, still don't like scientism and highly technical gibberish (or jargon) or science for science's sake though and probably never will.)
Most of the industrial papers I've seen on the "advantages and disadvantages of hot forging" tend to favor the advantages. However, a list of disadvantages usually looks something like this,... oxidation (scaling), decarb, grain growth and/or irregular/uneven grain size, and "hot working fatigue". Add to this possible damage to the steel from improper forging, like under heating (cold fracturing), over heating or burning, trying to move too much metal too fast ("hot fracturing"), and you start to get a pretty good picture of how complicated and risky it really is.
Last edited by Tai Goo; 05-04-2012 at 12:40 PM.
On the points of thin wide stock I usually favor some type of stock reduction,... hot cut, score (or cold chisel) and snap, saw, grind etc.
Last edited by Tai Goo; 05-04-2012 at 12:43 PM.
This might be proper or it might not but if I want to forge down the width of a thin piece of stock most of my heat is in the middle. The steel moves toward the heat. So I heat the entire end of the bar, pull it out and lay each edge in the anvil to suck out some of the heat and through it back in the fire for a few more seconds. What I end up with is a bar that is hotter in the center than the edges. This way I can avoid the I-Beam effect... lol.
If I do cut an angle for the tip, it is always a back-cut opposite to my intended tip geometry. Then I forge the tip up as I do the bevel. This works great for damascus because it forces the grain to follow the edge.
While we’re on it,… Oddly enough, if you do some searching on the “advantages and disadvantages of hot forging”, you’ll usually see “grain refinement” listed as an advantage. However, I don’t think they are talking so much in terms of the crystalline structures,... but rather more in terms of grain flow, diminishing porosity, minimizing inclusions and impurities, getting everything into solution etc… “macrostructure stuff“, that can result in a superior blade.
Hot forging is a combination of thermal and mechanical.
... The hammer is your "magic wand" and your forge is the womb! LOL
Last edited by Tai Goo; 05-04-2012 at 02:06 PM.
I forged some thin-ish 52100 down one time- eight blades, I just wanted to use it all up.
After acid etching, they looked stunning to me, with the way it almost looked layered, but I ended up with pin holes in the blades, and only 1 survived.
Was it just working the steel too hot/much that caused the pin holes?
One advantage of reducing large round or bar stock over flat barstock is the fish lips affect can be avoided. Shape the tip while the stock is still thick enough in cross section and hot enough to be forged, then draw the blade out to its desired length.
Charles, I havent tried out the forge with the adjustment you suggested yet but I did get to pound it into submission. This knife will probably not get done, cause I just want to bang more out, not finish this one. Some one on here said a guy banged out 100 knives and by then he was pretty good.I have 99 more to go. I want to learn how to do this much better and more efficiently. Time will tell.
One part of hot forging that gets left out in many discussions is keeping the blade and anvil clean.
Brush the blade off with a wire brush when you take it out of the forge, and wipe the loosescale off the anvil every time you put the blade back in the forge. Hammering the scale into the steel is the cause of all those "pin holes" dings and spots on most forged blades. If kept clean and scale free, the finished blade can be smooth and pit free.
The other thing that gets missed is to curve your blade down like a banana, and then forge it back up to straight. This stretches the edge out as it lifts, and will help avoid warp later on.
If you have to straighten the blade by hammering the upward curved spine back down, you are compressing the edge. This may come back in HT as a wavy edge warp.
It is better to die fighting evil than to live under it.
Thanks again for the tips Stacy! It makes alot of sense.
I have only done about 7 so far, but I get tip cracks all the time, I still haven't gotten that process down, just allow for some grinding.
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