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A while back I started on a pair of mountain-man style throwing knives. They were cut from some random square tubing a friend of mine had lying around. I wasn't too concerned with the quality of the steel, since they're going to get thrown and banged up any way. I got them ground down and shaped, and cold-hammered the edges (this was before I'd built my forge).

 

When I got my forge built, I decided to use a clay temper to harden them. (Please keep in mind I was still mostly clueless about what I was doing at this point). For clay, I used white clay that is all over my place about 2 feet under ground. I mixed up a good thick paste, and smeared it on the blades, leaving the edges bare. I think it was about 1/4 inch thick on the spines.

 

Then I heated them orange-hot in the forge, and quenched them in water. The clay all came off, and I was left with a weird "splatter" pattern all over the blades. It's fairly deep,too. It has a texture you can feel.

 

What is it? What caused it? And how do I avoid it on future blades that I want to look good?

 

 

DSCF2047.JPG

DSCF2049.JPG

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Yep! Too hot! However, it's a look that I like and try manipulate, some succesfuly some not! You can remove it with sanding, but start to use a magnate to determine correct heat, as soon as the mag won't stick to the blade, it is ready for the. Quench, a very dull red...

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Yep too hot and if I understand the process correctly, if you heat treat in the dark or dim light and you can actually see whats happening in the blade, up until the point you are ready to quench you will see a flickering in the steel, this is the carbon getting ready to go into solution. Once that flickering stops then you are ready to quench. You can hold the steel at temp for a few minutes if you can.

The opposite phenomenon can be seen when you normalize.

When you take a blade that is in solution out of the forge and hold it in still air you will see a shadow start in the edges and move to the center and that is the carbon going form the liquid state back to a solid state in the steel.

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JFYI, when I make throwers, I don't HT treat them at all. Mostly I make them from mild steel. But even if I were to make them from 1080, I wouldn't HT them. I have seen hard blades throw chips when striking another blade, and If you got enough torque on a bad throw, you could break a blade, So from a safety point of view, I leave them as forged. I'd much rather they bend (which can be fixed) than break.

 

Caleb, it's heat alone that causes the alligator surface. You can get good results with clay, if you keep the temperatures right. That surface comes from being 400-500 degrees too hot. It's easy to overshoot the temps when using just your eye. Before I got a thermocouple, I did my HT in a dark forge, after dusk, to avoid that problem.

 

Geoff

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This was clayed the taken to orange, cooled slowly to air temp , then heated to just non magnetic and quenched,

 

 

Every now and again I mess around, here's another

And one more,

 

 

Dagum Miles them look very bad you need to send them to me for proper disposal <Grins>

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Thanks guys, if you are carefull with the clay you can manipulate it to get various pattening, I should be. HTing one on wednesday, so I'll take some pics of the process.

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