Tempering question, I think I'm screwed.

[Angus McGunnigl]

I quenched and then forgot to re-polish the blade prior to tempering. I cleaned it up a bit, but for some reason left a bunch of black crap all over it.

I put it in an oven for an hour and now am thinking that the black crap is there forever.

Do I need to start over ? How clean should the blade be prior to tempering?

It's an old file. Am I screwed?

 

[zerogee]

Heat up some vinegar and soak the knife in it overnight or so -- the black scale should come off without much problem after that.

 

[silver_pilate]

Just soak or sand it off. It's normal and not a screw up. I never do any mechanical cleaning of a blade other than a rinse and brush-scrub prior to tempering, especially with high carbon steels as there is a good chance of the blade snapping from the internal stresses if you mess with it too much prior to tempering.

A blade heat treated in an open environment will have decarb that needs to be removed via grinder or sand paper after heat treating and tempering. A stainless blade treated in a foil pouch will have discoloration after heat treating and tempering that has to be cleaned up.

Bottom line: expect to do finishing work of some kind after heat treating.

Just be aware that warm vinegar can work faster than you think....

--nathan

 

[Angus McGunnigl]

Thanks for the replies. What a relief.

This is the first blade I believe that will be completely finished.

John Cougar Mellencamp once sang " ..I know alot of things, but I don't know alot of other things...."

That is a perfect description of my situation when it comes to this hobby.

Thanks again and thanks to all who post here. I am learing things !!!

 

[Will Leavitt]

Angus, this is one craft/hobby where the only thing you'll ever learn is that you have more to learn.

Classic example (and one I use to point out that the ABS is about learning and teaching) at Batsons year before there was a young 20ish man holding a discussion around his table in the tailgate sales area about mosaic damascus and pattern welding; he was surrounded by mastersmiths taking notes. One of the MS asked him about some welding technique (the only part of the question I understood was "what do you think about ---------------- -------- ----- welding?") his reply was "well we tried that and got trippy results." I noticed that one of the MS wrote "trippy results" down on his notepad. 60+ year old mastersmiths take the time to learn from a 20 something year old, there's something to be said for that.

Back to your original question, I usually just wipe most of the ATP-641 and Parks 50 off of the blade and toss it in the tempering oven. I can't remember the scientific reason but you should temper a blade as soon as possible after HT. I think it helps the martensite conversion.

 

[69_knives]

I can't remember the scientific reason but you should temper a blade as soon as possible after HT. I think it helps the martensite conversion.

and/or the less time you allow the blade to go "tink" the better off you will be.

 

[zerogee]

and/or the less time you allow the blade to go "tink" the better off you will be.

And less time to go all fumblefingers and drop a glass hard untempered blade on the concrete floor. You can then count the pieces and see how far they went, but it's not really all that much fun.