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I just finished 2 plasma cut blades. How should I go about heat treating the blades after sharpening? I only have an oxy/acetylene torch to heat the blades so how should I go about it. The blades are made of mild steel about 0.77 in wide and about four in long. I would upload a photo but I forgot my USB cord.

Andrew Karow

 

Of the four elements, air, earth, water, and fire man stole only one from the gods. Fire. And with it, man forged his will upon the world."-anonymous

 

The Armorers accomplishing the knights, With busy hammers closing rivets up, Give dreadful note of preparation." -Shakespeare

 

“The pen may indeed be mightier than the sword, but the wordsmith would do well to welcome the blacksmith back into the fold, so that artisan craftsmanship the world over may fend off the ravages of industrialised homogeneity and bland monoculture.” -Alex Morritt
The blacksmith is the heart of the pack, and the blacksmith is the heart of the pack. - Me
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By "mild steel" I'm assuming you got it from a hardware store, meaning it is A36. In that case don't bother, it doesn't significantly respond to heat treat. You can search the forum for several discussions on the topic; just don't use the forum search tool, use Google and a site search. site:bladesmithsforum.com <search term>

 

Example: site:bladesmithsforum.com A36 heat treat

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Ok do you think if I quenched it in used motor oil that it could absorb some of the carbon or did I just spend 2 hours for nothing on the two blades.

Andrew Karow

 

Of the four elements, air, earth, water, and fire man stole only one from the gods. Fire. And with it, man forged his will upon the world."-anonymous

 

The Armorers accomplishing the knights, With busy hammers closing rivets up, Give dreadful note of preparation." -Shakespeare

 

“The pen may indeed be mightier than the sword, but the wordsmith would do well to welcome the blacksmith back into the fold, so that artisan craftsmanship the world over may fend off the ravages of industrialised homogeneity and bland monoculture.” -Alex Morritt
The blacksmith is the heart of the pack, and the blacksmith is the heart of the pack. - Me
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To expound on what Jerrod mentioned a little: If you want a functional knife then you must start with hardenable steel-- and even better -- knife quality steel. Each steel has its own heat treat regiments required to obtain a hard sharpenable utensil. Thats why a lot of makers do not use mystery steel from the scrap yard (not knowing the steel means you dont know IF its hardenable or how to HT it specifically) but prefer to purchase known steel. Look up knife steel types and have your go at it for real this time. It's not a complicated process but you have a few holes in your approach so far. Try a bit more reading and youll get there. Heating with your oxy torch should be fine, but you also need to have a quench media and a tempering plan for after hardening.

 

Case hardening is a long time 12hours + at high temps to absorb into the "skin" of the steel some carbon to be case hardened. Primarily only done in industrial settings due to the operating costs. You just spent 2 hours practicing grinding for the real thing. those are throwing knives or letter openers at best.

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Got to agreement with Gabriel you did learn something that you will use later on. Don't bother trying to case harden a36. Shoot me a pm. I have some cut pieces of bandsaw blade 2" wide foot or so long appx 1/8" thick. I use for Damascus and for fillet knives

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I wasn't grinding I was programming a CNC plasma cutter. I was replicating a blade that I had broken the tip off of. It was a lot of small complicated and precise measuring.

Andrew Karow

 

Of the four elements, air, earth, water, and fire man stole only one from the gods. Fire. And with it, man forged his will upon the world."-anonymous

 

The Armorers accomplishing the knights, With busy hammers closing rivets up, Give dreadful note of preparation." -Shakespeare

 

“The pen may indeed be mightier than the sword, but the wordsmith would do well to welcome the blacksmith back into the fold, so that artisan craftsmanship the world over may fend off the ravages of industrialised homogeneity and bland monoculture.” -Alex Morritt
The blacksmith is the heart of the pack, and the blacksmith is the heart of the pack. - Me
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The grinding part should come between the profile shaping and the heat treat. You'll want to get your plasma cut blanks "Ground" down to more of a knife blade shape prior to heat treating. You don't have to use a grinder, you can use files, or whatever, but the slang term is "Grind".

 

Don't take it to a thin edge before you heat treat it. leave the edge with some meat to it so that you don't have cracking or warping problems in the quench. then finish grind after you quench and then temper it. You could leave it full thickness before heat treating, bit then you have to remove a lot of hardened steel.

 

Given your other post advising someone to always orient their quench tank north, I think some more reading is in order. There is a lot of bad info on the internet. This place is a great exception to that. You'll find lots of great people willing to share hard learned knowledge. make the most of it, and good luck. This stuff is addictive.

Edited by Brian Dougherty

-Brian

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Not to mention on good steel the plasma cutter will leave a zone of decarb that must be ground off before final shaping. Since this was mild steel it doesn't matter, it's just practice.

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If this is the only mild steel knife you ever made your way ahead of me! I forged blades out of mine roof bolts(a36) for 6 months back when I first started. I always wondered why my sword bent so easily! 1986 no such thing as internet forums. If it wasn't Jim Hrosilous' book I might still be trying it LOL

www.hoyfamily.net

Isa 54:16 Behold, I have created the smith that bloweth the coals in the fire, and that bringeth forth an instrument for his work; and I have created the waster to destroy.Lu 22:36 Then said he unto them, But now, he that hath a purse, let him take it, and likewise his scrip: and he that hath no sword, let him sell his garment, and buy one. Mr 8:36 For what shall it profit a man, if he shall gain the whole world, and lose his own soul?
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Ok thanks for the info guys. (the quench tank orientation came from an old friend from Arizona long time blacksmith)

Andrew Karow

 

Of the four elements, air, earth, water, and fire man stole only one from the gods. Fire. And with it, man forged his will upon the world."-anonymous

 

The Armorers accomplishing the knights, With busy hammers closing rivets up, Give dreadful note of preparation." -Shakespeare

 

“The pen may indeed be mightier than the sword, but the wordsmith would do well to welcome the blacksmith back into the fold, so that artisan craftsmanship the world over may fend off the ravages of industrialised homogeneity and bland monoculture.” -Alex Morritt
The blacksmith is the heart of the pack, and the blacksmith is the heart of the pack. - Me
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These are the blades I've been working on.

0523091304.jpg

0523091313.jpg

Andrew Karow

 

Of the four elements, air, earth, water, and fire man stole only one from the gods. Fire. And with it, man forged his will upon the world."-anonymous

 

The Armorers accomplishing the knights, With busy hammers closing rivets up, Give dreadful note of preparation." -Shakespeare

 

“The pen may indeed be mightier than the sword, but the wordsmith would do well to welcome the blacksmith back into the fold, so that artisan craftsmanship the world over may fend off the ravages of industrialised homogeneity and bland monoculture.” -Alex Morritt
The blacksmith is the heart of the pack, and the blacksmith is the heart of the pack. - Me
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Seems that no one remembers about SuperQuench.

5# rock salt

24 oz of Dawn blue dish detergent

8 oz of Shackalee II (you can use Jet Dry from the dish washer section at the grocery store or any other surfactant).

Place in a 5 gal container and fill with water and stir until all of the salt is dissolved.

Robb Gunter invented this for hardening mild steel. In a demonstration he cut a section off of a mild steel bar and made a chisel from it and hardened it in SuperQuench, then used the chisel to cut the chisel to cut the original bar. Robb has told me that you should get a 53-54 RC and should then temper it at about 450 degrees. The tempering does not take any of the hardness out of the blade but will refine the grain structure.

While it will not make as good a blade as a good steel alloy, it will harden. I have had my EDCs made of Rail Road Spikes and half a horse shoe and had to sharpen them less often than my wife's Case Equine Special.

Wayne Coe
Artist Blacksmith
729 Peters Ford Road
Sunbright, Tennessee
706-273-8017
waynecoe@highland.net
www.WayneCoeArtistBlacksmith.com

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Seems that no one remembers about SuperQuench.

5# rock salt

24 oz of Dawn blue dish detergent

8 oz of Shackalee II (you can use Jet Dry from the dish washer section at the grocery store or any other surfactant).

Place in a 5 gal container and fill with water and stir until all of the salt is dissolved.

Robb Gunter invented this for hardening mild steel. In a demonstration he cut a section off of a mild steel bar and made a chisel from it and hardened it in SuperQuench, then used the chisel to cut the chisel to cut the original bar. Robb has told me that you should get a 53-54 RC and should then temper it at about 450 degrees. The tempering does not take any of the hardness out of the blade but will refine the grain structure.

Not really metallurgically sound info there. If you look at a TTT for mild (let's give the benefit of the doubt and say some nice 1025) you'll notice it is impossible to get much martensite. Tempering at 450F will drop it a couple points HRC if you do have some martensite, and not really do much refining of the grain. Grain refinement requires a bit of heat, deformation, and/or phase change; none of which can be said for a 450 F temper. If you don't lose any hardness at 450 F in a plain carbon steel, then you don't have martensite and thus have a letter opener. As for the chisel cutting the original bar, that isn't overly impressive. A 40 HRC chisel will definitely go through 20 HRC steel. That doesn't make it good for a knife. It's all good practice though, and not-so-great blades can still be useful. They can even be better than store bought, many of which are junk and yet people find them useful.

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I kinda agree with Jerrod you need a phase change to refine the grain.

Andrew Karow

 

Of the four elements, air, earth, water, and fire man stole only one from the gods. Fire. And with it, man forged his will upon the world."-anonymous

 

The Armorers accomplishing the knights, With busy hammers closing rivets up, Give dreadful note of preparation." -Shakespeare

 

“The pen may indeed be mightier than the sword, but the wordsmith would do well to welcome the blacksmith back into the fold, so that artisan craftsmanship the world over may fend off the ravages of industrialised homogeneity and bland monoculture.” -Alex Morritt
The blacksmith is the heart of the pack, and the blacksmith is the heart of the pack. - Me
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Not really metallurgically sound info there. If you look at a TTT for mild (let's give the benefit of the doubt and say some nice 1025) you'll notice it is impossible to get much martensite. Tempering at 450F will drop it a couple points HRC if you do have some martensite, and not really do much refining of the grain. Grain refinement requires a bit of heat, deformation, and/or phase change; none of which can be said for a 450 F temper. If you don't lose any hardness at 450 F in a plain carbon steel, then you don't have martensite and thus have a letter opener. As for the chisel cutting the original bar, that isn't overly impressive. A 40 HRC chisel will definitely go through 20 HRC steel. That doesn't make it good for a knife. It's all good practice though, and not-so-great blades can still be useful. They can even be better than store bought, many of which are junk and yet people find them useful.

I'm glad someone (other than me) said this. I would not have said it quite so well........

Edited by Joshua States

“So I'm lightin' out for the territory, ahead of the scared and the weak and the mean spirited, because Aunt Sally is fixin’ to adopt me and civilize me, and I can't stand it. I've been there before.”

The only bad experience is the one from which you learn nothing.  

 

Josh

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