Quenching Frustration and Revelations

[Ragnarok Forge]

I am a bit conflicted right now.  I worked up 40 knife blanks over the winter. I quenched 15 more of them last weekend.   I am using old Nicholson files for a lot of this work, along with some Heller Rasps.  I get them for free from buddies after they wear them out.  

My  frustration is that the blades are hardened for half their length - tip end ( they skate a file and pass the brass rod test).  The back half of the blades are not fully hardened.  The front half of each blade has a very visible hardening line.

I triple normalized each blade prior to the quench.  I am using Canola Oil at 130 degrees.   The blades are brought up to quenching temp in a 2" X 4" rectangular tube in the forge. I am working carefully to keep the blade at just above non magnetic for 4 to 5 minutes and then quenching the blade.  

Based on steel color I have been worried I was getting to hot and enlarging the grain of my knives.  Based on the actual results from this last batch, I am thinking I am not hot enough in the back half of the blade.  The steel is high organge when it hits non-magnetic.  Any thoughts or tips you have would be great.

This one has been a learning lesson for me.  My last set was all small 1095 file and rasp knives and came out great.  The blades skated a file the entire blade length. This set of blades if for mid size knives.  

I am thinking that I need to get a thermocouple and electronic thermometer screen to verify temps.  I need to be able to lengthen my soak time on the steel to ensure even carbon distribution.

Anything else that you can add would be appreciated.  I am really happy with everything on the knives so far with the exception of the hardening results.  I am going out after dark tonight to renormalize the blades.  Then another effort will be made to quench them at a bit higher and more even heat along the blade length.

[Lin Rhea]

Clay,
      I did a little reading to try to help with this situation. My thinking is that you dont need to heat the  1095 steel any higher than 1475 degrees for your quench. I think your problem is the oil and uneven heating and/or cooling. I think you need a faster drop in temp to get it done. So, you may have to use brine or Parks 50. Parks 50 made a believer out of me.

May I make a suggestion? Harden a couple in the manner you describe above in the effort to make the correction. Test them to destruction. Again, I think this is the wrong approach, but it may take doing it to be convinced. That's natural. I'm that way myself.  

Then follow your earlier recipe, only use a faster quench and concentrate on the even heating and cooling. If you need to, send me a couple and I'll quench them in my Parks 50 and draw them and send them back to you to test.

[robtattoo]

Are you sure the files are, in fact, 1095?
I know that a lot of the files I used to use were W2, a water quenching steel.

I believe Lin is correct in thinking your quench medium may be too slow.

One further thought; do you quench tip-down or cutting edge down?

[Jeremy]

If the files are 1095, canola oil should work with the method you've been using on small to medium sized blades.  By medium-sized I mean under 5" length and under 3/16" thick.  Outside of those dimensions and the oil just can't cool the blade fast enough.  1095 is pretty unforgiving like that.

[Ragnarok Forge]

Lin, where do I find Parks 50 in smaller than 50 gallon drums?  Is there a good brine recipe you know of? I worked on temp control while renormalizing the blades last night.  I put a hard fire brick inside the forge against the end of the tube I heat the blades in, it worked great. I am thinking about using an interrupted quench 3 seconds in water and then into the canola.  I will use Parks 50 once I have it in my shop.    Rob Tattoo, I checked with Nicholson & Heller they both use 1095 for the files I have.   I am edge quenching. I believe this helps prevent the blade from developing reverse Sori that could occur with a full blade quench.  lin, I have a silly attachment to my knives and hate to break them.  I think it is time to break that. Your offer is very generous.  I will take you up on it.  I will send a pm to get your address.

[Lin Rhea]

Clay,
   My concern is that your impulse to raise the quenching temperature is going to enlarge the grain of the steel. If that happens, the blade wont be as tough and flexible. A test would give you an idea of it's toughness and allow you to see the grain if it did break.

I am thinking that the steel has a range that it will work and if it's in that range when you quench and still not hardening, it must be something else.

Holler at me.

[Ragnarok Forge]

Lin, I am sure you are right on the heating of the blades. I played with my system and checked the color of the steel against becoming nonmagnetic. I was already pushing being to hot.  The steel is becoming non magnetic at middle orange.   I will be bringing the blades to just above nonmagnetic and letting them soak for 10 minutes prior to an edge quench. The adjustments I made to my burners and my tube system should allow better control of my forge and blade heat to achieve a full soak to get the carbon to go fully into solution prior to quenching.  I have had good success with only a few failed blades using an interupted quench with 1095.  I plan to run a third normalization on most of the blades and then a interupted quench after full dark tonight.  Worst thing that happens is another lesson in humility.    

[Lin Rhea]

This stuff is a harsh teacher and keeps us humble, I agree. It's kind of like being married. It's predictable most of the time.

[Lin Rhea]

Dont get me wrong. There is a science to all this metalurgy, but the variables have to be sorted out to avoid confusion. Some things are reliable and pretty much non-negotiable, such as the quenching temperatures per the steel. The variables are things like quenchant, weather, timing, etc. We have to reduce the effects of the variables as much as possible. It is an amazing thing.

[tippit]

Clay,
You can get 5 gal buckets of Parks 50  from a group in Texas fairly reasonable.  If you can't find it, I have info back on my computer in Boston.  My wife & I leave Aiken on Friday pulling horses.  Should be back by Sunday.  PM me if you need address...Jeff

[DANA HOLMAN]

Jeff, i would like to know where its is in texas,
thanks
dana

[Ragnarok Forge]

Tippit,

I would definately like that info. I will pm you.

[Ragnarok Forge]

Ok success and failure occurred last night.  I cracked a bird and trout knife and properly hardened a skinner.  I used an interrupted quench, 3 seconds in water and then into canola oil.  The B & T cracked in the water.  I am going to break the B & T to check grain size tonight.