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I Forge Iron

First time 440c knife


Matt Scanlan

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Not quite finished yet but I wanted to share my adventure thus far. I dont normally do stock removal but I got some metal as a christmas gift from my wife. (Shes awesome) So this is an experiment more than anything. Up till this point the most experience I have with a chromium alloy is 5160 but thats a whole nother ball field.

First off the metal when annealed is difficult to drill through, not sure if it was just me or if anyone else has had that issue but it seemed to gum up the flutes on my bit.

On the contrary it is a dream to grind, my little 1x30 grinder with a 40 grit belt chewed thru the metal like it was mad at it.

Next is what some may see as controversial but in my research I found how the steel is supposed to be wrapped in stainless steel foil and HT in an oven to limit oxygen exposure. I dont have an oven and I wasnt paying 100 dollars for foil to do a single knife so I decided to limit oxygen exposure by getting a carburizing atmosphere in my propane forge. My logic was if it can be forged then perhaps leaving out the 'proper steps' shouldnt hurt it too much. If anyone can explain the science behind having to limit oxygen exposure during HT but it can be carefully forged I would appreciate it. 

I eyeballed the temp and let it soak for 30 minutes then plate quenched it with aluminum and used my compressor to force some air over it. Came out straight and passed the file test. Next I tempered it at 410 degrees for an hour and then let it sit in a cooler full of dry ice for 4 hours (no real logic here but I read with dry ice the longer the better) 

After the cryo quench I file tested it again. I have to admit I was shocked at the noticeable difference in hardness from the HT. I then tempered it a second time and here is the result so far. Ill post a picture of the final product. Any and all constructive criticism is definitely accepted. 

20200103_231754.jpg

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On 1/4/2020 at 12:41 AM, Matt Scanlan said:

If anyone can explain the science behind having to limit oxygen exposure during HT but it can be carefully forged I would appreciate it. 

Typically the more complex stainless alloys require specific temperatures and ramp times to get all the contributing elements in the alloy fully into solution in the proper order.  This requires that the steel is kept at an elevated temperature for a long time.  Most people use electric heat treat ovens for this task so the temperatures and ramp times can be tightly controlled.  Most non-professional heat treat ovens don't have a good way to keep oxygen out during the process, so the work-around is the stainless foil.  Otherwise, because the steel is at elevated temperatures for so long - several hours in some cases - there would be significant decarburization of the steel during that time.

Obviously you got a hard blade with your method.  What I don't know is whether you got the most out of the steel that it has to offer by cutting some corners.  It would be interesting to see how much difference there is between your method and the manufacturer prescribed sequence though.

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ThomasPowers- the friend I'm making this for was going to pay upwards of $200 dollars for a knife of similar style, though it only had a 30 degree bevel at its edge. I decided to grind a steeper bevel on this before heat treat then the cutting edge to decrease the angle the knife had to be held to cut properly. The picture is rough ground to 80 grit, im working on getting everything to a 1500/2000 grit finish. 

Also I'm etching the blade and found that the alloy is completely resistant to hydrochloric acid and ferric chloride but reacts great with sulfuric acid. I have to fix a small portion where the acid got underneath the nail polish though. 

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2 hours ago, Buzzkill said:

Typically the more complex stainless alloys require specific temperatures and ramp times to get all the contributing elements in the alloy fully into solution in the proper order. 

Buzzkill thank you for that information. That makes more sense now. It was just puzzling to me that the steel required an oxygen free environment for heat treat but could be exposed to oxygen and repeated heating cycles in forging. I guess I'm more used to carbon steels. Stainless steels are still outside my comfort zone but after this experience I would like to learn more about them.

I agree I cut corners and would love to see the difference between my results and those of the prescribed method. If I had an oven at my disposal I would have strictly stuck to the manufacturers instructions, but as for now an oven is still on my dream list.

I can say the blade after the cryo quench is far harder than my experience with 1080. Perhaps in the future I could aquire a set of Rockwell testing files if I intend to use this steel again, but so far it hasn't been as much of a headache as I was expecting it to be. 

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Thanks for the information on it.  One thing I have run into is folks wanting copies of poorly designed commercial knives; because that's what they've seen. Some are so focused on them I bow out of the commission. (Of course others want copies of high end custom work---but don't want to spend the money for the time it takes for high end work...)

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And then there are the "fads" ...remember the Massive survival knives with a hollow handle?  I hold that a survival knife is the knife you are CARRYING when put into a situation where you need to survive.  Something too large and heavy that spends it's time under the car seat and is not carried doesn't meet that criteria.  And then there was the chisel pointed tantos, sigh----fairly rare in the historical record compared to other designs but popularized by a big name knife company here in the states.

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On 1/4/2020 at 1:41 AM, Matt Scanlan said:

let it sit in a cooler full of dry ice for 4 hours (no real logic here but I read with dry ice the longer the better) 

Take a look at this comment, from a separate discussion of subzero quenching:

This has links to a massive amount of really good info.

1 hour ago, ThomasPowers said:

remember the Massive survival knives with a hollow handle?

Thank you, John Rambo. 

 

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