Idiot cause Heat treat crack!

SteelSlaver

SteelSlaver

Joined
Feb 17, 2007
Messages
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Well, I am one of those learn the hard way guys. Read the whole Tool Steels Simplified book, even the chapter dealing with forces caused by HT The I get some of Mace and Bruno"s 1095 and go out and pound away to to make a blade with integral bolsters and cap. Hard to get the stuff thick enough in those areas by just hand forging so when I got close I arc welded some built up in the bolster cap area. When I was finished I tossed it in the forge at about 1450 and then shut it down closed it up and came back Friday and got it out. I took it in and ground it to near final shape. Then comes the stupid part, the area between the cap and the bolsters I clamped i my mill and milled it out all nice. Perfect, complete with a nice square inside corner on the scale side so I wouldn't have to work with it hardened. The blade side of the bolsters has a long radius from thickness to blade width. Did a bunch of file work on spine and top and bottom of handle flats, but, not any on bolsters. Yup, then I go out and do a nice bake in my electric oven and when I quench my brain still don't have the light on, because I do a tip and edge quench and only the bottom part of this nice thick section attached to the thin areas gets dunked for the first few seconds. I temper twice at 400 and all is good. Lol. Then as I grind away the minimal surface crap it looks great until suddenly there appears a crack in one bolster. Yup, my lack of thought had caught me. Great looking knife. Just what I wanted, except for the crack. Further inspection shows one starting at the cap. Lucky for me I was able to grind the bolsters off and get rid of the crack there as it was basically cracking the one side bolster off and was running parallel to the blade and a bit out from that line. I cut the cap off and and am now going with just a pinned set of scales, so it is not a total loss.

Here is my question, now that I am sure there is a problem with this :rolleyes: by experience instead of simply knowing it like I should have.:jerkit: How should I go about making and hardening an integral. I was going to forge weld on pieces the next one to get the guard and cap thickness I want, instead of arc welding built up. Although, I really don.t believe it was the welding that caused the crack though. I weld well and used a solid procedure, preheat, similar metal, etc. Plus I annealed everything after I was done. The crack was in from the weld zone and I realize the major stress zone is on the edge of the weld not actually in it. I believe it was from the square inside corner and the mass of steel that had to cool slower than the thin sections. So how do I do prep and heat treat something like this. Is it possible with 1095 or should I go to 5160. If I leave an inside radius how to I get a nice square corner for my scales or do I round the scales corner. do I do a point plunge on the blade and keep the bolsters out or do a instant complete submerge. Clay around the bolsters ? how do I do it. Thanks Jim
 
Lots of things can happen in the HAZ and it might be that combined with design features . Photo ??
 
I should have photoed first I guess but, I was POed and curious and ground the bolster and crack off. Here is a photo with wood scales glued on it. The area from where the wood begins to the black line was originally steel and the exact same shape. Where to black line is was milled square to the spine :rolleyes: .The crack ran parallel to the spine just outside what is now the edge of the steel. Like the whole left bolster was cracking off. I wanted the same lines as this photo. I know I could pin or solder the bolsters on I just wanted to a integral.
 

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I know it doesn't help much, but I feel for ya, Bro'. What a shame.:mad:
- Mitch
 
[. Hard to get the stuff thick enough in those areas by just hand forging
Jim have you tried upsetting,localize your heat and hammer down to build material--Got my knife back and looks great thanks--Butch:thumbup:
 
Well I will try making the knife I wanted again. With the next one I will forge weld on some 1095 to make the thickness I want in the bolster and cap areas. Then when I work it I will use a ball mill to leave some radius in the inside corners where the scales go. I will radius the scales to fit that radius. I think it was a combination of thick section with a square inside corner with some help from the weld that caused the crack. I may not even quench the bolster area next time. Just plunge it tip in until near that area. Thanks. I still got a good knife out of it, just not what I wanted. Jim
 
Well I have to agree with Don arc welding and tool steel do not mix well. You will have much better results with the forge welding. I also think you are corect in going with the radius on the bolsters. Sharp inside corners tend to cause problems. I jest heat treeted my first integral but I used 3/4 round O1. I also gave the bolsters a radius. No problems wih the heat treat. As for grinding that sucked. I dont have a mill handy so getting everything lined up was a pain. I will post a pic when I get the chance. Good luck next time.
Will Crump
 
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