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Blast! Cracking!


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Right! So right when im about to clean things up, have the handle all ready to go...

 

This is was a piece of salvaged steel (leaf spring) *I know I know... unknown steel...

Quenched in warm veg oil, just the cutting edge was brought to non-magnetic.

Tempered in a toaster oven at 400F for an hour. When I brought it out of the oven after it had cooled it was cracked. Was not (at least visually) cracked when I put it in...

Perhaps I should have tempered it at 350? What do you all think?

 

I did do some straightening and a little texturing before the HT while the blade was not at all hot. (not cold, but I could hold it with my leather gloves... so pretty much cold)

Perhaps I cracked it then but just couldnt see it till the temper?

 

Also - I had kinda a tough time getting the blade to forge out horizontally. I've looked a bit on here of any pictures of anyone forging out a cleaver like this, have not seen any WIP pics... was kinda tough getting the blade to be wide enough with the tank being flush with the spine.. does that make any sense?

 

Here are some pics.

 

Any thoughts?

Ideally id probably start with some known steel that is 3.5-4" wide, but I have all these spring segments about....

 

IMG_20140417_001057.jpg

 

8a4ad699-cfb5-4e1b-95c2-8040b4d82b7d.jpg

 

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I listen to the masters here and do it three or four times Lol. Still...accidents happen. My first blade was a file...did everything just right..but a few days after all was said and done, a tiny crack appeared!

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Ah, scrap steel. These things happen, several different factors: The steel could have had pre-existing damage, you may have forged it too cold (leaf springs can somtimes airharden in thin sections, and will crack if whacked), or you may have overheated it prior to quenching (the little bubbles in the scale indicate to me that you did, a bit). Normalizing 3X before quenching helps avoid the cracks, and will reduce grain size and improve the edge-holding ability of your blade as well.

 

I have a big pile of similar cracked stuff under my forge... :P

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Hi,

 

I had a similar looking crack on a draw knife I was making not too long ago. The issue was that I hardened the blade and then let it sit overnight before tempering. it cracked before the temper however, so this may not be the cause of your problem. Like you said it is possible there was a micro fracture in the steel that propagated during tempering, but there's really no way to know. However, I think the problem is more likely due to grain structure. If the blade was overheated the grain will grow causing excess stress which can lead to cracks like this. Make sure to use a magnet or other indicator so not to overheat the blade before quenching.

 

A couple things I notice from your description of the process: first, like Orien said, make sure you normalize (bring to critical and air cool) the blade several times before hardening. Normalizing reduces the grain size, whereas annealing once may not. Annealing only needs to be done once, after normalizing, if done right. I've heard some very prominent bladesmiths do not anneal at all, at least not the traditional way. Second, 400 degrees sounds like too low of a temperature for spring steel. When I make blades from leaf springs I temper at 450 or until it reaches a pretty purple color and it works well for me.

 

I'm not sure what you mean by, "was kinda tough getting the blade to be wide enough with the tank being flush with the spine." I'd say that looks like a pretty shape for a cleaver though.

 

Hope this helps!

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question...can it be melted and recast without loosing its properties???

 

Melting via induction can maintain the chemistry, with decent limits on change. The folks over in the Bloomers and Buttons section would likely point to crucible melting too. The properties you get will really come from heat treat. I'm not aware of any other "readily available" means of melting that won't also drastically change the chemistry. Microwave and laser come to mind, but those aren't easy to get your hands on.

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Yeah, I'm one who never anneals for forging (I do use it occasionally to set a blade up for hand-filing, though). "Real" annealing actually enlarges the grain, from what I understand, while normalizing makes it smaller.

 

Both are irrelevant during forging because you're way above critical temps, and it changes constantly anyway. But you do need to do one or the other after, to set it up for filing (anneal) or for the quench (normalize).

 

Recasting it, probably not without a furnace and crucible made to do so, but one could cut it into bits and use it in patternwelding, or something (never done this myself, but seen it done here... :) )

Edited by Orien M
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PS, I get what you mean about lining up the tang and the blade. Don't be afraid to hammer on the edges to push things where you want 'em, in this case a good heat and some blows to the inside edge of the tang would likely have done it. I often use a wood hammer on a wooden block for stuff like this.

Edited by Orien M
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Don't confuse annealing with normalizing they are different procedures, A critical anneal can cause carbides to clump instead of having a fine distribution. Normalizing will, if done correctly, decrease grain size and relieve stress in the steel.

 

Doug

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