Broke another one

M

Martin S.

Joined
Apr 17, 2007
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115
Have been trying 80crv2. Yesterday made a recurved chopper with a 10" blade. After quench noticed the blade wandered from the plunge line to tip about 1/4". Last one that did this I snapped in three pieces trying to straighten right out of the quench so knew better than to do that again. Ran this one through two hours at 400 degrees temper thinking it would work. Mild and mid pressure did nothing. Put some muscle into it and snapped cleanly in half. Grain looked very fine at the break.

Looks like this steel needs a higher temperature for tempering than the 1084 I've been using. What temperature is optimum for a large chopper or camp knife to eliminate this brittleness while still being able to hold a good edge?
 
Martin S. said:
Have been trying 80crv2. Yesterday made a recurved chopper with a 10" blade. After quench noticed the blade wandered from the plunge line to tip about 1/4". Last one that did this I snapped in three pieces trying to straighten right out of the quench so knew better than to do that again. Ran this one through two hours at 400 degrees temper thinking it would work. Mild and mid pressure did nothing. Put some muscle into it and snapped cleanly in half. Grain looked very fine at the break.

Looks like this steel needs a higher temperature for tempering than the 1084 I've been using. What temperature is optimum for a large chopper or camp knife to eliminate this brittleness while still being able to hold a good edge?
Click to expand...
I have straightened warps by clamping the blade between two straight pieces of steel during tempering. It sometimes takes a couple of cycles (each time tightening the clamps) but the blade usually comes out straight.
 
I would suggest 450F for a chopper in that steel. Clamp the blade to a large bar of steel and put a nickel under the blade to make it over-bend to compensate fro the warp. Run it through both tempers clamped. After the second temper and cooling off in cold water, unclamp the blade and see if the warp is gone. If not completely gone, re-temper while camped with two nickels under the balde. You may have to repeat several times while increasing the reverse bend to get it gone.
 
Stacy, even tempering at 400 as the op did, the blade shouldn't have broke when being straightened by hand, should it? I'm wondering if it didn't have a microcrack or something to contribute to the breakage.
 
I'll let Stacy supply the definitive answer, but with the thickness the chopper would normally have, there would be little flex to the blade. After proper tempering a blade will not "normally" bend and stay bent (as required for straightening). While it might flex some, it "should" come right back to the shape it had before flexing.

As the blade is removed from quench you should be able to bend blade easy (with gloves because it will be hot) and remove any warps from quenching. I don't work with high carbon much at all, but with SS there is a short window where the blade can be straighten.

Stacy's method of using nickles while tempering is a good idea - I usually use a small rod so it will reach across the metal I'm using to clamp blade to.

Ken H>
 
Yes, still should have cracked. Just can't force them like that. Use the temper to straighten as Stacy et al said.


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Have you tried straightening right out of the quench. I mean right away, still smoking hot. I quench and pull it out when it's cold enough that oil stocks to it but still smoking. Check for straightness real quick. If it has a bow I straighten by hand, it is still very soft so be cautious as you can over bend it. Then back in the oil to finish cooling. I have never worked with 80crv2 but it works like a charm on all the other steels I use, especially 5160.
 
You can straighten if you take it out of the quench after it passes the 'pearlite nose ' but before it hits the Ms temp.In that area it's still mostly austenite !
You can try straightening when hardened but AT at least 400 F.
You can straighten BEFORE HT by giving it a stress relief/sub-critical anneal [1200 F , 2 hours ] then HT
 
JTknives said:
Have you tried straightening right out of the quench. I mean right away, still smoking hot. I quench and pull it out when it's cold enough that oil stocks to it but still smoking. Check for straightness real quick. If it has a bow I straighten by hand, it is still very soft so be cautious as you can over bend it. Then back in the oil to finish cooling. I have never worked with 80crv2 but it works like a charm on all the other steels I use, especially 5160.
Click to expand...
Aldo says 80CRv2 is simply an improved version of 5160. It's probably a little more complicated than that, but I've pretty much switched over.
 
mete said:
You can straighten if you take it out of the quench after it passes the 'pearlite nose ' but before it hits the Ms temp.In that area it's still mostly austenite !
You can try straightening when hardened but AT at least 400 F.
You can straighten BEFORE HT by giving it a stress relief/sub-critical anneal [1200 F , 2 hours ] then HT
Click to expand...

:thumbup:
 
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