PDA

View Full Version : My first warped blade



PetrifiedWood
08-01-2011, 10:06 AM
Tried a 3/16" piece of O1 steel yesterday.

I cut out the profile, and ground the bevel, then put it in the kiln cold. Ramped up to 1475 and held for 10 minutes, quenched in 130 degree mineral oil. After tempering twice at 425 degrees, I brought it back out to clean it up and notice a slight curve along it's length.

So, I stuck the blade in the vise with some round bits of scrap metal to apply pressure where I needed it, and had to really crank it over to bend it severely before it would stay straight.

I was really surprised at just how tough the steel had become, and I think my HT worked for this steel.

So my questions are:

Is it ok to straighten blades like this after tempering?

And, what steps can I take to prevent warping in the future?

jkf96a
08-01-2011, 02:03 PM
If you got away with straightening the blade, then it worked. Straightening cold is often a recipe for disaster. Much safer to clamp them just past straight and run them through a temper cycle. There's a good post on bladeforums about it. As far as not warping to begin with, there are several things that can help. One, make sure your blade is heated evenly. If it's laying flat on the floor of your kiln, it will warp. Stand it up on its spine or use a holder. Two, normalize a forged piece at least twice before quenching. Three, agitate the blade in the quench oil only spine to edge or tip to handle, never side to side. If you do all those things, some will still warp :) That's the cost of doing business.

PetrifiedWood
08-01-2011, 02:10 PM
If you got away with straightening the blade, then it worked. Straightening cold is often a recipe for disaster. Much safer to clamp them just past straight and run them through a temper cycle. There's a good post on bladeforums about it. As far as not warping to begin with, there are several things that can help. One, make sure your blade is heated evenly. If it's laying flat on the floor of your kiln, it will warp. Stand it up on its spine or use a holder. Two, normalize a forged piece at least twice before quenching. Three, agitate the blade in the quench oil only spine to edge or tip to handle, never side to side. If you do all those things, some will still warp :) That's the cost of doing business.

I think you might have solved it then! I agitated side to side in my quench. This was flat ground O1 steel bar stock so it wouldn't have had any hammer forging stresses. I had it in the rack that evenheat sells for use in their kilns, spine down. It actually rested on it's spine and did not touch the pins on the sides of the rack at all. But I did move it side to side in the oil after the quench and I guess that could have caused the problem.

I hadn't thought of tempering in a clamp, but I didn't notice the warpage until after my second tempering cycle was over anyway. Would a third 2 hour temper hurt anything should I need to do this in the future?

jkf96a
08-01-2011, 02:35 PM
I've had no trouble with three or even four temper cycles when working with a crooked blade. You can get away with one hour cycles if you've already tempered and are just straightening.

Even though it wasn't forged, grinding can put stress into the steel. Wouldn't be too surprised if the surface grinding may have something to do with the warpage, but I think you're right that it was most likely the side to side agitation.

PetrifiedWood
08-01-2011, 06:27 PM
I've had no trouble with three or even four temper cycles when working with a crooked blade. You can get away with one hour cycles if you've already tempered and are just straightening.

Even though it wasn't forged, grinding can put stress into the steel. Wouldn't be too surprised if the surface grinding may have something to do with the warpage, but I think you're right that it was most likely the side to side agitation.

Thanks for your help and input. I appreciate it!

I'll give the clamp and temper method a try the next time I end up with a warped blade. I'm guessing it's best to run at least one temper cycle first before clamping to relieve some of the internal stress?

jkf96a
08-01-2011, 06:55 PM
Correct, I usually run the first temper before any clamping/straightening. Could probably get away with some minor clamping in the first temper cycle, but why push your luck?

PetrifiedWood
08-04-2011, 06:35 PM
Well I did another blade, this time in 5/32 O1 and agitated up and down, no warping! :)

The real test will be when I use the rest of that bar of 3/16" O1 and see what it does,