Here we go again--needing help

v-6

v-6

Joined
Nov 24, 2007
Messages
952
i just got 7 blades ready , and brought they in the house to put them in the oven at 450 ,3 one hour sessions letting the cool to room temp .
6 of these knives were 1095 and this one was 5160
these were all quenched in oil, with nothing wrong .
why did this happen to this only 5160 and what can or should i do to rectify
this. i measued the edge of the blade and it says .055 the came new from Texas knifemakers

http://i29.photobucket.com/albums/c264/vern-vicki/MVC-009S.jpg
http://i29.photobucket.com/albums/c264/vern-vicki/MVC-012S.jpg

:confused:
 
Was the 5160 previously use as a leaf spring? Or used for something else maybe? Are you absolutly sure it went into the quench straight?
I don't use 5160 but I hear it is forgiving enough you can heat it up, straighten it and try heat treating again.
55 thousandths is plenty thich enough in my experience but as I said i don't use 5160.

ron
 
One thing I do is to hang my blades in the oven as opposed to lying them down on a tray or the rack. It's probably me just being paranoid, but I don't want the side of the blade facing the elements to heat up more quickly than the other side. I hang all my blades parallel to the bottom of the oven with the edge up.

That blade is pretty thin at the tip. Did you normalize prior to quenching?

--nathan
 
The blade is quite thin and the warp could be from uneven grinding. Is it flat or hollow ground? In some of my first hollow grinding attempts, I made some blades that were very thin toward the tip and ground deeper on one side. You can get some funky stuff with a hollow if it's really uneven.

I would straighten it, anneal and re-heat treat. Worst case is that it breaks. Next worse is that it warps again. Best case it comes out straight. Any case, you learn something new.
 
silver_pilate said:
One thing I do is to hang my blades in the oven as opposed to lying them down on a tray or the rack. It's probably me just being paranoid, but I don't want the side of the blade facing the elements to heat up more quickly than the other side. I hang all my blades parallel to the bottom of the oven with the edge up.

That blade is pretty thin at the tip. Did you normalize prior to quenching?

--nathan
Click to expand...
yes i normalize prior to quenching and every thing was ok till i took them to ht.
vern
 
vern,
What type of forge or heat source did you use for the HT?
How long was the blade in the forge?

The blade looks fine to me as far as thickness, and at .055 ,the edge is certainly not too thin.Sometimes a blade will warp for no apparent reason. There are a few things that you can try to straighten it:
1) Re-anneal the blade and straighten it .Then re-normalize it and re-do the HT.
2) Re-temper the blade at 500F and try to straighten it while hot. Put the blade in a vise, or make a straightening jig, and carefully over-flex the blade. Repeat until it is straight. This has some risk of the blade tip breaking off, but usually works fine with 5160.
3) Use the blade for testing. Sharpen it razor sharp and do all sorts of chopping and cutting,brass rod (edge flex) tests, and finally bend it until it breaks ( dull the edge before this test). Look at the grain structure after the break to see how your HT is doing. Once in a while all smiths should test a blade to destruction, just to see how tough their blades are, and how well the edge lasts.

Don't let a warped blade get you down. It happens.
Stacy
 
bladsmth said:
vern,
What type of forge or heat source did you use for the HT?
How long was the blade in the forge?

The blade looks fine to me as far as thickness, and at .055 ,the edge is certainly not too thin.Sometimes a blade will warp for no apparent reason. There are a few things that you can try to straighten it:
1) Re-anneal the blade and straighten it .Then re-normalize it and re-do the HT.
2) Re-temper the blade at 500F and try to straighten it while hot. Put the blade in a vise, or make a straightening jig, and carefully over-flex the blade. Repeat until it is straight. This has some risk of the blade tip breaking off, but usually works fine with 5160.
3) Use the blade for testing. Sharpen it razor sharp and do all sorts of chopping and cutting,brass rod (edge flex) tests, and finally bend it until it breaks ( dull the edge before this test). Look at the grain structure after the break to see how your HT is doing. Once in a while all smiths should test a blade to destruction, just to see how tough their blades are, and how well the edge lasts.

Don't let a warped blade get you down. It happens.
Stacy
Click to expand...

i used the wife's new oven. 1 hour @450 , let room cool, 3 hours like this
 
Vern, the household oven was used for tempering. Stacy is curious as to how you performed the heating to critical prior to quenching in oil: what did you use and and how did you use it. :)

--nathan
 
silver_pilate said:
Vern, the household oven was used for tempering. Stacy is curious as to how you performed the heating to critical prior to quenching in oil: what did you use and and how did you use it. :)

--nathan
Click to expand...

Ok this is how i did things.
brought forge to where i though was close to 1450 , put in knife and kept checking the knife with a magnet till it did not stick to th magnet and at that point i put it back in the forge for a count of 5 and straight to oil quinch with blade edge facing north and moving straight north to south till the oil quit
smoking. took out move to oven SET at 450, cooked for 1 hr took out let cool to room temp, three times.
that how i did it.
After the quench it was ok , after the oven and cool there is was.
vern

did i do it right ?
 
OK, you have given me a bit more to go on.
First, a five second soak at slightly above 1350 (non-magnetic) is a far cry from a 5 minute soak at 1550F, which is what 5160 needs.
Second, moving the blade from the quench tank at 200-400F into a 450F oven never allowed the blade to finish the martensite transition. You may have even got into bainite.
Last - I don't know if you are joking or not, but the North-South thing is just a light hearted gag that is bandied about with new smiths. It make no difference. Did you quench straight in, tip first? Or edge first?

These two problems may have created a blade that was incompletely transformed to austenite, then incompletely converted to martensite. The combined stresses of mixed structures could easily warp the blade. I would guess the blade is not as hard as you would think it is, either. It may skate a file, but the structures are a mixed bag. I would anneal the blade and re-do the HT with a longer soak at 1550F ( about 200F above non-magnetic).When the quench is done, allow to cool to room temperature before tempering.

Stacy
 
bladsmth said:
OK, you have given me a bit more to go on.
First, a five second soak at slightly above 1350 (non-magnetic) is a far cry from a 5 minute soak at 1550F, which is what 5160 needs.
Second, moving the blade from the quench tank at 200-400F into a 450F oven never allowed the blade to finish the martensite transition. You may have even got into bainite.
Last - I don't know if you are joking or not, but the North-South thing is just a light hearted gag that is bandied about with new smiths. It make no difference. Did you quench straight in, tip first? Or edge first?

These two problems may have created a blade that was incompletely transformed to austenite, then incompletely converted to martensite. The combined stresses of mixed structures could easily warp the blade. I would guess the blade is not as hard as you would think it is, either. It may skate a file, but the structures are a mixed bag. I would anneal the blade and re-do the HT with a longer soak at 1550F ( about 200F above non-magnetic).When the quench is done, allow to cool to room temperature before tempering.

Stacy
Click to expand...

tip first. the north south thing was so you would know that i was moving it in one direction and not in a big circle
vern
 
I have had 5160 warp like that on occassion from too much heat during grinding and uneven heat during heating it up for hardening( I use a torch) Never had much luck with thin tips like the one in the pic. I now leave a little extra mass up front during heat treat and remove it afterwards.
 
I'm with Stacy. It probally has partially hardened and on one side more than the other. It needs 1500-1550 degrees for a soak of about 5 minutes. Non-magnetic is not hot enough to harden the steel completely.

I have had blades do that if they are laying on their side while heating. I have better luck with them sitting on their spine edge up and off the floor of the oven because their own weight can bend them when they reach about 1500 degrees.

If you take just a second to sight down the knife before it goes into the quench you can see if its warped. If it is, straighten it out and put it back in the heat. Sometimes there is remaining stress from improper thermal cycles when normalizing. I have the best luck if I anneal the blade after normalizing.

I like to quench point first unless it has a differential heat treatment.
 
Yes Bruce, The temp was certainly too low. I think that, plus the moving from quench tank to oven without allowing a cool to room temp, would cause a delayed warp. I have seen blades warp while sitting on anvil to cool,that were straight when I took them out of the tank.Look at the sori formed in a katana. This is the extreme of controlled warp due to different structures being formed.
Stacy
 
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