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I'm new here. I've been making knives for a couple years now but I've always struggled getting the heat treat right. I have a forge and have read everything on this forum and others about heat treating.

 

Here's what's happening. I anneal the blade three times, I heat it to nonmagnetic and then quench. After I clean off the scale I see these raised areas in the steel. Almost like little bubbles. I'm very careful to not overheat the blade but I think thats what happening and I'm seeing grain growth. I'm not sure. This usually happens when I'm using 1095.

 

Can anyone take a look at these pictures and tell me what they think? Or is this normal and this just has to be ground off after the HT? Thanks for the help.

 

 

IMG_1939.JPG

 

IMG_1940.JPG

 

IMG_1941.JPG

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This is a surface chemistry issue, not grain growth. What shows up as features on a metal surface are effects from either decarburizing, carburizing, and/or oxidizing. Generally what people see are effects from oxidizing. You will only see grain growth effects when you look at a fracture surface (i.e. when you break the blade).

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I can't speak to the grain condition, but it does look like an over-heated oil quench on the surface.

 

It might help to be sure you're in a dark enough environment to observe the decalescence / shadows in the steel.

 

Magnets are not an exact science.

 

(I've got a couple early blades that look just like that)

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What shows up as features on a metal surface are effects from either decarburizing, carburizing, and/or oxidizing.

 

... and this is almost always a sure sign of over-heating for these effects to be so pronounced, in my own experience (my apologies to Jerrod, I have great respect for your knowledge on these things).

 

My suggestions:

Quench at night, with just enough light to be able to find the quench tank...

Research blade normalizing (no need to anneal 3 times), and decalescence in steel.

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I agree that it looks to have been overheated. It's always hard to say from a photo but it appears to me as if you're not getting a good austenitic conversion as well . One problem may be with using 1095 without a fast quench oil like a Park's 50. I would guess that if you go to a 1084 or 5160 that much of the problem will disappear.

 

Gary

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... and this is almost always a sure sign of over-heating for these effects to be so pronounced, in my own experience (my apologies to Jerrod, I have great respect for your knowledge on these things).

 

My suggestions:

Quench at night, with just enough light to be able to find the quench tank...

Research blade normalizing (no need to anneal 3 times), and decalescence in steel.

 

A certain level of heat is required for these reactions to happen (this won't happen like this at room temperature, after all) and the hotter you go the faster/more pronounced it is going to be. Given the typical forge environments when people try for a heat to quench I think it is very safe to say that over heating probably occurred, and almost certainly too much oxygen for the heat you had.

 

Also, I feel bad for not mentioning, as others thankfully have, that decalescence is your friend. Magnets are fun and all, but they aren't as helpful as one would think or hope.

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Normalize it a couple times then re-sand it and harden. You should be good to go, though you may have a bit of de-carb to get through. Assuming your blade isn't super thin that shouldn't be a problem.

 

Before you do that though get a chunk of the same material and play with it in (near) dark conditions, looking for decalescence and recalescence. That way you know what you are looking for.

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