Join Date: Mar 2006
Location: Sturgeon Bay, Wisconsin
Ariel, No need to notch the ingot...it folds at the top on its own during forging...for two reasons. One being that unless high forces are delivered it is the natural tendency for metals to move more at the surface that the middle and they "fish mouth" or "duck bill". After more light forging the edges of the steel touch and you get a folded appearance. The second is that the poorest part of the ingot is the top and it almost always had gas pockets from the cooling process and as such is less dense and moves differently under the hammer. Often collapsing onto its center as forging progresses.
I have yet to see a "sound surface" at the top of an ingot. All ingots have some surface irregularities in them in the form of pockets or bulges and if the porosity is not visible it exists in micro form with the most porous at the top.
Often the top of the ingot becomes the spine of the blade. I would call the folded over bit a seam and I have seen several where the seam wanders from the spine onto the flat of the blade. In one case it fell off and was cold riveted back into place.
Ariel...if that broken blade is for sale I would like to purchase it and do chemical, hardness and microscopic analysis on it to add to my database.
That goes for anyone else who has broken crucible steel blades or bits and pieces.
Edit: It is a simple matter to add silicon to the steel when it is liquid (very hard to stop if glass is present actually) and I have yet to see any glass survive in the bar once forged out to a blade. It all goes away when the ingot is being forged into bars. This is due to its liquid nature at temperatures used for forging and also that if allowed to cool on the anvil it is untempered glass which is very brittle and simply falls away when left to its own devices after a day of forging.
Edit Edit: I would guess that large grain size (and shipping abuse) was the cause of the fracture. If the break is at all black on the edges then it could also have been a flaw from the quench which waited for the stress of shipping to finally break. Cracks caused in forging or the quench or almost always black color due to high temperature oxidation. In modern blades if the crack is yellow or blue then the crack was in the tempering stage of manufacture...the color is again due to oxides, but lower temperature oxidation.