1084 hardening.

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I've been using 1084 to make several knives and I have been having inconsistent quench hardening results. Some blades harden the first try and some don't. I normalize each blade then heat until non-magnetic with a red/orange colour. I am using warm canola oil as a quenchant. I test each blade with a Nicholson file. I had blades harden only at the tip and some at edge and not all the way to the spine. Can someone give me tips or idea's on a way that would be Less problematic ?Maybe I'm quenching to hot? But I am checking with a magnet as soon as I can. I use a large coffee can maybe I need a bigger tank?
Thanks.
 

AVigil

Adam Vigil knifemaker working the grind
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Are you using a magnet as well?
 
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Yes, I test the whole blade with a magnet and if it doesn't stick I quench right away.
 
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I heat the steel to red/ orange, between 1500-1600 that is critical temp.
 

AVigil

Adam Vigil knifemaker working the grind
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Where did you get the 1084?
 
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Try using kosher salt as a temperature indicator, it melts at 1475*F and go just a little longer to get to your temp.

What type of forge/oven are you using? You could be getting lots of decarb which will test soft until ground down. Yes get a bigger quench tank, especially if quenching more than one knife in a short time period, atleast 1 or 2 gallon, more is better.


-Xander
 
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I use a 500 000 btu torch in a fire brick forge. I sand the carb off before testing with a file but maybe I have to remove more material. Thanks for the salt trick, I"ll try that next time and a bigger tank I will try too.
 
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Do you sand it off or grind it off? I often will take a couple passes at either 80 or 120 grit to test.

With torch & brick forges, often times the edges and tip will heat quicker, taking the knife out and letting those cool to black and putting the knife back in will keep from burning up the edge/tip and ensure a more uniform heat. Also using a muffle, a piece of black iron pipe inside the forge can reduce hot spots and over heating the edge.


-Xander
 
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I hand sand until I expose the steel but not very deep. I will go further next time and see. Ya I have to play around with the blades a little to get even heat and I will try putting something in the forge near the edge and tip.
Thanks guys.
 
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Your quenching temperature is too low It should be about 75 F above the critical temp
 

Stacy E. Apelt - Bladesmith

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+1

You need to heat to non-magnetic and then about 100 degrees higher for 1084. That should be a shade brighter than the blade was when non-magnetic.
 

Stacy E. Apelt - Bladesmith

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I heat the steel to red/ orange, between 1500-1600 that is critical temp.

The critical temperature is the point where the transformation to austenite occurs. For 1084 steel, that is around 1325F.

The non-magnetic point is also called the Curie point, and is about 1414F for steel.

The target point is the temperature that the elements are ready for quenching..... for 1084 is 1500F.

The critical point is far too low to quench the blade.....the Curie point (non-magnetic) is still too low to quench the blade.....about 75-100 degrees above that point is the target point, which is when you should quench the blade.
 
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I heat to the orange range, so about 1600. I thought i was quenching on the hot side>so quenching orange is ok? How many degrees would be the max for hardening, because I've read that steel won't harden if quenched to hot?
 

Stacy E. Apelt - Bladesmith

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The color that you think you see means very little. In a test a while back, they had about 100 well trained blacksmiths look at some steel that was pulled out of a temperature controlled oven. They did this with five different ranges from 1200F to 2400F. Nearly every answer was low. In the mid-range they were about 200-250F too low. Many thought the steel was 1600F when it was really 1900F. Only one person guessed the steel as being hotter than it actually was.

The ambient light can greatly skew the look of the steel. The temperature charts are merely guides, that is why a magnet is such a good tool....you can't fool it.

FWIW, the color orange is too hot. Orange red is about 1600F, orange is 1700F. Here is a good chart, but it may not agree with other charts, and the colors may not look the same to two different people.
http://www.stormthecastle.com/blacksmithing/blacksmith-steel-heat-and-coloring-chart.htm
 

Stacy E. Apelt - Bladesmith

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1600F is way too hot for 1084. it should be 1475F to 1500F. But, since you are only guessing at the temp, who knows how much too hot is really is. It is impossible to tell if the blade is damaged internally without destructive testing. Test the edge and see if it is chippy or rolls, that is about all you can do. A Rockwell test by a shop or near by smith would be good.

As to the steel being too hot:
While the right temp is what you want, too hot is far better than too cool. If quenched at 1600F, 1084 would probably survive the quench and be usable, but not optimal. If quenched at 1400, it may not harden well. At 1700F, I would suspect a bad blade.
The biggest problem with high temp is grain growth. That starts getting much greater after above 1600F.

During the quench:
At higher than target temps, the vapor jacket survives too long and is much larger, thus the steel may not miss the pearlite nose completely, and end up too soft. Such a blade may have hard and soft spots. Cracking can occur,too.
 
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I had trouble heat treating the first knife blade I forged. In my case I think it was because I let it cool too much before getting it to the quenchant.

It's a small blade, just 1 1/2 inches long, forged from a piece of scrap 1084. In this case I don't think the problem was the temp coming from the forge as much as how fast cooled once taken out. It lost color so much faster at that size than the couple larger pieces I've made that I'd get only a hit or two with the hammer. My quenching pot was across the yard because I was too lazy to find a long enough extension cord for the hot plate and it took me too long to walk across the yard. I may have paused for a long moment as I pulled it out. I didn't think to check with a file and had tempered it and was trying to put the edge on it when I realized it was too soft. I repeated the HT and it turned out great.

This is probably too obvious to be the problem but that didn't keep me from making the mistake!
 
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