Blade test

John Katt

John Katt

Joined
Mar 19, 2012
Messages
7,863
OK so I buy two stacks of leaf springs, 78 Chevy motor home $20 and I have my fingers crossed that it will be 5160, after reading what seems like a encyclopedia size book on heat treating with every recipe you can think of I settled on this method

annealed buy taking steel to just past magnetic in the forge shutting it off and letting it cool over night, next hammer out a basic blade shape and normalize 3 times allowing the blade to cool to black heat between cycles, then cool to room temperature, grind out a basic hollow ground shape and normalize 2 more cycles, now I am ready to heat treat,

with all my tinkering around, taking steel to non magnetic I haven't been comfortable with the speaker magnet on the bench method, just didn't seem sensitive enough, so I hung a rare earth magnet from a string and was happy doing it that way, I feel there is a fine line between weak and non-magnet state, so any way I did the best I could keeping the blade at non-magnetic for a 5 minute soak and then I oil quenched in 135 degree motor oil

so far so good.... ground off the scale and tempered in a toaster oven, 2 cycles at 400, allowing the blade to cool to room temp between cycles, sharpened the blade to a 5x belt, at this point it easily shaves the hair off my arm

so for the test, I started whacking a piece of 5/8 home depot steel rod, not sure what kind of rod they have? and I only managed to put 1 small chip in the blade ( whacked the entire length of the blade three times ) and then broke the blade in the vice to have a look at the grain structure.

So what do you guys think ;0)

edit--- the edge grind is 21 degrees



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How far did it bend before breaking? Did u do any edge retention testing, such slicing cardboard or rope or cutting wood.
 
I put the tip of the blade in the vice just far enough so the vice had a full bite on the spine and it snapped at about 30 degrees, after the toaster oven heat treat the entire knife was a light straw color, I never drew the spine temper down to blue

I chopped a 2x4 in half twice and the edge held up real nice, didn't cut any cardboard or rope but i can do that tomorrow and post the results

I think i was kinda focused on breaking the knife to see the grain structure and chopping a 2x4 didn't seem extreme enough, so i went to the steel, if i did that to my buck it would have been one big chip
 
the grain looks OK to me. its not super fine, but it doesn't look like it sustained much unhealthy grain growth. looks like you did alright, but as I am going to start heat treating my own soon I will look forward to what others have to say.
 
I have to disagree with Nebulae, that grain size is WAY too big. It has hardened, certainly, but not to the level you need for full performance.
The grain size you are looking for looks creamy, almost glassy, with no real visible particles.
As a good example, and something to calibrate your eye to, snap a piece off of an old file (the tip, not the handle).
As soon as you see that you'll know what you're after. Good luck!
 
I agree with Andy... the grain is coarse. Here is a really good picture that illustrates the fine/coarse ends of the spectrum. Your seems to be in the middle.

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A few points raised a brow for me...

1. There is no need to anneal prior to forging. You can omit that part from your process.
2. When you normalize, you should start at a higher heat(1600F or so) and reduce the temperature for subsequent cycles (1500F and 1425-1450F). You could even quench in there somewhere to further refine.
3. You said you soaked it for 5 minutes... in a forge or kiln? You have little chance of soaking in an open forge without overheating.

I think you may have not normalized as well as your could and definately overheated on the quench.

Rick
 
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I'm not sure how much cardboard and rope constitutes a good test but here is what I cut, also I was cutting into my bench like you would with a kitchen knife and a cutting board, after all that I was just barely able to cut a few hairs off my arm

some clarification on the soak time, I built a blown forge with a variable speed fan and I can turn it way down, and using a test piece protected from from the flame by a couple of fire bricks stacked inside the forge I adjusted it so it was holding the piece very near non magnetic also when I was heating the blade I was moving the piece in and out of the forge to help maintain the color, I know this isn't a perfect way to do things, but I am fairly sure I didn't go very far above non magnetic. my next big project is a PID controlled electric oven

I'm planing on whipping up another test blade in the next few days and I will give the high to low normalizing temps a try, with all the reading I have done I must have missed that part

Thanks for the tips keep-em coming

John-E-Katt



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well I think I nailed it, I did what you suggested Rick raised my normalizing temp and then cut it back for 2 more cycles and I quenched a little closer to red color

the grain structure between the two is like night and day looking through my mag visor

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jonekatt said:
well I think I nailed it, I did what you suggested Rick raised my normalizing temp and then cut it back for 2 more cycles and I quenched a little closer to red color

the grain structure between the two is like night and day looking through my mag visor

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Click to expand...



That grain looks substantially better
 
Thanks for the slap on the back and the "atta boy" guys ;0)

Sure feels good when you get something right on the 2nd try, I think I will cut up a few more test pieces and see how that goes, just to make sure I can reproduce the results

It would be nice if you could tell what the gain structure was without breaking the blade, I wonder if the tone of the ring that the piece makes is different when properly hardened?
 
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