Molecules in forged blades

[p. gannon]

Following the forging of a blade, its filing, grinding etc to close proximity of final form (not final heat treat, polish and sharpening) is it appropriate to heat the blade and allow to slowly cool three to four times in order to stabilize the molecules in the steel?

Thanks,
Paul

[rich pierce]

Hopefully we can get Wick Ellerbe or another person with good metallurgical knowledge to chime in.  From what I know, yes, but be careful to not get too much scaling during all that and to work in a carbon-rich environment.

[LRB]

  Not only appropriate, but really necessary. If you have forged it, you really should anneal it first, then heat to a nice bright red and let air cool about three times, at least to black. Do this in dim light. This is called normalizing and makes the grain smaller, while relieveing stresses. You may have heard of hammering the edge to pack the grain and make it smaller. This is a myth. The only way to reduce grain size is the normalizing process. Three times is enough. More times won't hurt, but you reach a point of diminished returns after three. Then go ahead with your heat treat. And don't fall for the "bring the blade to non-magnetic and quench". That is also a myth. Bring it about two shades of red hotter, then quench. I don't know of any steel that will properly harden below 1450°, with 1475°/1500° being better, and non-magnetic is only 1414° What steel are you working with? If you do not have a commercial quench oil, canola oil is your best bet.

[dannybb55]

I have a Knife that I forged in 1994 that was simply forged, annealed, pickled, drawfiled, ground fine on my 2 foot stone, hardened and tempered, There is plenty of carbon in the blade. She holds a keen edge and is tough enough to punch through a truck fender and pry a carriage bolt out of old oak. I tempered her to a straw colour and worked from back to edge. The original steel was a truck coil that I unwound, that piece was tough enough to kick back when I hit it. What does all of the extra work gain you? What more do you ask of your blade than cut, don't break and last?

[p. gannon]

I appreciate the replies.

I am using the omnipresent RR spike for the blade.  It is a poor quality steel but cheap (free) and a good for practice.  In the past I have case hardened them with useable results.


Paul

[ottawa]

when looking at RR spikes look for HC on the head that means high carbon steel no need to case harden .

[LRB]

RR spikes make good letter openers. The high carbon spikes are only .35 carbon. They will not make a serious blade. The plain RR spikes are even less in carbon, about like cold rolled mild steel.

[Chuck Burrows]

Try using Super Quench instead of oil - with the HC spikes I've gotten them into the 45RC range whihc while not great is usable and is close to what many originals were at.
Do a search on www.anvilfire.com for the Super Quench formual - nothing exotic is required.

[Canute Rex]

RR spikes are good enough for practicing your forging, but if you are going to spend your time finishing a knife I recommend buying real tool steel. Go to Admiral Steel (http://www.admiralsteel.com/shop/) and get some HR1075/1080. Then you will know what you are dealing with. A 36" x 1 1/4" x 3/16" piece will cost you all of $9 plus shipping.

Be careful not to get it yellow/white hot or you will burn off carbon. If you are working with a coal fire, make sure that you have a thick bed of coal and keep the blade horizontal on top of it. If you are working with propane or acetylene, make sure that the flame is slightly oxygen starved.

No need to anneal it multiple times - just heat it till it is non-magnetic (dull red) and stick it deep in a bucket full of wood ashes to cool. Leave it there for a few hours.

If you want to protect the blade from scaling when heating it for annealing or hardening, wet it and then rub it with chalk till it has an unbroken layer. I use powdered blue chalk-line chalk in a convenient squeeze bottle. You can use any color you like.

To harden, heat to a dull cherry red in dim light and quench it in vegetable oil (less toxic). Make sure to immerse the whole thing in one plunge. Remember that the surface of the oil could flame up - have a metal container with a metal cover.

To temper, heat veeeeerrrrrrryyyy slowly from the back of the blade. This is where patience pays off. Bring it to a bronze color at the cutting edge and as blue as possible at the back. Patience, patience, patience. A sponge soaked in your quench oil is useful for spot cooling areas that run too fast. Did I mention patience?

If you blow it, anneal twice, harden, and temper again.

Good luck!

[LRB]

  A very good suggestion on steel, but I would suggest that anyone wanting to heat treat a blade might want to do a little further research on the matter.

[David Rase]

Go to Admiral Steel (http://www.admiralsteel.com/shop/) and get some HR1075/1080. Then you will know what you are dealing with. A 36" x 1 1/4" x 3/16" piece will cost you all of $9 plus shipping.

Canute,  Thanks for the link to Admiral Steel.  They sell the perfect size pieces of steel.
DMR

[ottawa]

and I too thank you for the link prices a purrty good so are the sizes