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P Jones

Problems with heat treating

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Ok, so I'm in the middle of a project making a blade with a hamon and got to the point where I was ready for the quench. I do all my normal steps and after it cools I grind off the scale and do a quick dip in acid to get a sneak peak at the pattern and to make sure everything worked. Nothing. This is probably the third attempt for me in making a hamon. The second had a slightly visible line, but not too defined. So a thought occurred to me: maybe the blade just didn't harden. I took a file and compared the sound to an untreated piece of the same steel. They both sounded exactly the same.

 

So to get a little practice in before I try the quench again, I cut off a couple of strips of steel and prepare a bit of an experiment. Three pieces total, the two I cut and the original bar of steel. The first would be quenched in water, the second in AAA oil, and the two would be compared to the original piece as well as each other. The oil preheated until I can only touch it for a little more than a second. Heat both pieces in a dark garage until they're about a dull orange color and quench each one. Pull them out, set them in a vice, and file test all three. They still sound the same with the file biting into all three pieces. 

 

I'm just stumped at the moment. I used this post from Zeb as a reference in the process. The steel is 1075. I'm looking around to see what information I can dig up, but I'm not sure what exactly I'm doing wrong. Is the steel too hot/cool before the quench, is this the wrong quench material (I also have a can of canola oil I can use), or are the gremlins responsible?

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Sounds like you're not getting hot enough.  Don't go by color alone, watch for decalescence as described by Zeb.  Then quench as quickly as possible.  It should harden in water, canola, and AAA, although you won't get as vibrant a hamon in AAA, it's a little slow for that.  

Other possible factors: your clay may be too thick.  You don't need a lot.

You may have decarb on the surface.  File some more and see if it skates deeper in.

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Thanks for the response. I played around and just heated the steel then watch it cool off. I can see the shadow Zeb's referring to. Just to see that I understand it right, the shadow is the crystal structure using energy to change from one structure to the other, and while it's cooling the color just before the shadow is the target temp for quenching?

 

I did give it another go using that method and ground away some of the surface before file testing again. The was a noticeable difference that time. I'll have to try the blade itself again in a little while here. Thanks for the tips on the hamon btw. I'll probably risk water on the next try to see how that goes.

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No, always quench on a rising heat the second the shadows go away.  If you wait for them to come back you will not harden your blade.

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OK Gotcha. 

Risked water quenching the blade and a learning experience occurred. Cracks along the edge etc. On the plus side it did harden and I could see a hamon upon etching it. I'll have to start over again either way, but thanks for the help.

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Did you order the material recently from the NJSB? There's a recent batch of 1075 that has high manganese content which promotes through hardening and therefore is not good for hamon. I have had this stuff harden beautifully but take no hamon. What it sounds like is the water quench was fast enough to cool it differentially but the cracks are obviously a no go. I did some more experiments with water quenching a 1075 piece today and had three fold success, though this was the low manganese 1075. I would try to order some new material and make sure it is low in manganese.

 

When water quenching I make sure to very carefully watch and keep mental note of what the colors in the steel are and what I am seeing in the shadow. You can make vibrant hamon from carefully controlling the heat at the edge, with propane as well as coal or charcoal. If you're using clay a lot of the difficulty is taken out. My advice is to know the steel and your temps. While non magnetic isn't something to go by on its own, it can be a useful tool to know you are in the range of 1420F (I believe) and you can adjust slightly hotter from there. 

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