Author Topic: hot enough?  (Read 5698 times)

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Offline paulc

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hot enough?
« on: November 18, 2021, 05:26:13 pm »
Since I had collected way too much crap scrap wood I burned a bunch today to clean-up the shop yard.  Figured while I was at it I would throw a couple mower blades, some hand powered hedge shears, and a couple lopping shear blades into the pile to see what the fire would do to it...I swear I saw at least some of the blades glowing at one point but maybe not enough?  When I tested the still insanely hot blades they grabbed the magnet immediately.  Burned the crap out of my thumb in the process....  does the magnet test only work after the metal has cooled?

Thanks, Paul


Offline Morgan

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Re: hot enough?
« Reply #1 on: November 18, 2021, 09:10:18 pm »
A fire of wood coals and a blower less powerful than that leaf blower will get the steel as hot as you want to the point of melting. There is a pretty big learning curve using wood or even charcoal, but itís plenty do-able and if you are going to be making stock removal blades, thereís no need for anything other than a hole in the ground for your fire and a source of forced air that you can dampen as needed. Working in the dark or near dark is easiest for me if Iím using charcoal or wood as it is much easier to see what is happening with the steel. In daylight, your steel can go from not hot enough to burned up in a hurry. Introduce air slowly, low volume and work your way up , if all youíre wanting to do is normalize and heat treat, you wonít need as much as you might think.

Offline paulc

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Re: hot enough?
« Reply #2 on: November 18, 2021, 11:09:04 pm »
Thanks Morgan, appreciate the response. Am I hearing you say this metal is ruined?  Or just that its really unlikely I got the results I was looking for?

Do I just need to try again, paying attention this time? Cause I sure wasn't paying attention today.

Thanks, Paul

Offline Morgan

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Re: hot enough?
« Reply #3 on: November 18, 2021, 11:52:37 pm »
No, the steel isnít ruined. The steel will become non magnetic in the 1400įish range. Hotter and it is still non magnetic, any cooler and it is magnetic. Steel will start to glow well before it is non magnetic.

Offline paulc

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Re: hot enough?
« Reply #4 on: November 19, 2021, 11:14:47 am »
So much to learn...so what did I accomplish yesterday other than burn some scrap wood and my thumb?  What kind of properties can I now expect in the "proto" blades?  Will the be easier or harder to shape?

Thanks so much!  Paul

Offline Don W

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Re: hot enough?
« Reply #5 on: November 19, 2021, 11:52:01 am »
One of the first forges I made I used and old vacuum cleaner for air. I rigged a cover for the exhaust and used a gate valve from a dust collector to cut the flow down. It was still to powerful so adding a T so much of the air flow could escape worked. It need to be just enough flow to feed the coals.

It will be magnetic until it's hot enough, then loose magnetic when it get to the point it needs to be. Once out of the fire it will gain it's magnetic properties back fairly quickly, but the temper will be gone.

Coals work better than fire, so if the scrap wood is pine or something like poplar, it's much harder to get it hot enough. Locust, oak and similar are best. Building a nice bed of coals is where you want to be.
Don

Offline paulc

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Re: hot enough?
« Reply #6 on: November 19, 2021, 01:23:19 pm »
Good info...def crap wood.  Mostly pine

Offline KHalverson

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Re: hot enough?
« Reply #7 on: November 19, 2021, 07:59:08 pm »
most good high carbon steel becomes non magnetic (critical) @ 1450 to 1500 degrees.

even though you can heat to over non magnetic once the steel cools it becomes magnetic again.
i would say you probably achieved a sub critical aneal..
the steel should be soft enough to easily file or drill.

Offline Gimlis Ghost

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Re: hot enough?
« Reply #8 on: November 19, 2021, 08:16:06 pm »
I had some old files I wanted to make into knife blades. I was using an old style two burner oil heater at the time. This type had seperate chambers with a cast iron ring around the inside above the vents the vaporised oil entered the chamber.
I placed a file crossways on the ring and lit the heater for the night. In the morning I cut off the heater and retreived the file. It had annealed enough I could cut it with a file so I worked it into a nice blade. Next day I took it outside and heated it with a MAP gas torch as much as I dared and dropped it into an old metal icetray full of burnt motor oil. The temper was perfect.

Offline Hawkdancer

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Re: hot enough?
« Reply #9 on: November 21, 2021, 02:19:18 am »
Somewhere, I read that salt will melt around the same temperature that is right for proper forging.  Smack me if I am wrong😀!  I assume it is coarse salt.
Hawkdancer
Life is far too serious to be taken that way!
Jerry

Offline GlisGlis

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Re: hot enough?
« Reply #10 on: November 22, 2021, 10:30:14 am »
beware that at that temperatures salt produces toxic chlorine compounds

Offline paulc

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Re: hot enough?
« Reply #11 on: November 26, 2021, 06:35:03 pm »
.....sub critical aneal..
the steel should be soft enough to easily file or drill.

KHalverson and everyone else...this steel is definitely soft enough to file and drill. I have one blade shaped and I think ready for final sanding and then handle added. 

Is it likely it is too soft, like the edge won't keep? Besides smacking the cutting edge to see what it does is there some other way to check it? I saw where you heated the handle w cutting edge in pan of water to keep the edge soft...did I read that right? By heating the handle to cherry red it will be softer than cutting edge so easier to machine?

How do I put hardness back into the cutting edge? Should I...?

Thanks so much! I hope the holiday treated everyone ok.PAUL

Offline Don W

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Re: hot enough?
« Reply #12 on: November 26, 2021, 07:53:39 pm »
Now you have to heat treat it to harden it again. Make sure you harden it before you put the handle on it
Don

Offline paulc

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Re: hot enough?
« Reply #13 on: November 26, 2021, 08:50:34 pm »
Is that when I heat it real hot then dunk in oil...?

Paul

Offline Don W

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Re: hot enough?
« Reply #14 on: November 27, 2021, 08:08:28 am »
Yes, but different metal heat treat different. I typically use Canola oil, it's like $3 a gallon at Walmart. (Or it was a year ago, it last a long time).

This is tricky without a propane forge, but the nice thing is you can try several times without hurting anything.

Here is what I do:
Heat untill loose magnetic, then dunk in oil. Let it cool. Then temper with 2 cycles in a toaster oven. 400 degrees for 2 hours each.

I write this up:
https://bladesmithing.timetestedtools.net/heat-treating-for-beginners/
Don