Heat treat dilema/question(s).

If your steel is right, your oven is right, your time at temperature is right, and your quench medium is right, then your files must be wrong.

I'd say check around for a shop with a hardness tester nearby and have them test a couple of the coupons (after they've been ground free of decarb).

--nathan
 
disclaimer.....I only have heat treat book(internet) knowledge.... There was a similar thread 3-4 months back.... the culprit eventually turned out to be not enough decarb removal.... It was being done, but taking off more metal than what was thought to be enough resulted in higher hardness test results.
 
It could be the decarb not being removed deep enough. I plan to track down a local Hardness tester, to get a professional test.
 
try ten thousandths, then 15 thousandths, then 20 thousandths when you have 3 successive readings that are virtually the same you know you are below the decarb layer and into the actual steel, a few thousandths you are definitely still in the decarb. I wish I still had access to a microscope to show you how deep decarb goes

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Okay I got back to it and seems I have a nice hard knife (around RC60 according to my files). I used 0-1, quenched at 1500, then tempered at 400.

The question I now have is since I needed to take off a certain amount of material from the bevels before getting to hard material, wouldn't the same apply to the blade edge?

For 0-1 heat treated unprotected in an oven at 1500 then tempered at 400 how much material would you say needs to be removed?

How about 1075? I am trying to plan leaving the extra material in front of the choil next time.
 
bladsmth said:
Ed, that is a common misconception, and is completely wrong. I understand what you were trying to say, though.
Actually heat radiates equally in all directions. It is warm air that rises over cooler air. This is called convection.
Heat is energy, and just like light, radiates until it is absorbed. It is not affected by gravity,while light, which is particle energy (photons) is minutely affected by gravity. Air, which is normal matter, is gravitationally affected, and thus warm air (less dense) rises over cool aid (more dense).
Click to expand...

The warm air rises over cooler air is also a misconception, while true it is not correct. A more proper term would be hot air travels to cooler air (or more generally, energy travels from point of highest concentration to lower concentration, depending on ease of flow.
In our open atmosphere, it does indeed rise due to the heat source being the ground (remember light="energy"=something needs absorb it to heat up. The ground absorbs some light and becomes kind of like a pan thus heat radiates to the source with less heat, which is our upper atmosphere, where there is little matter to absorb light the medium is of course air. In other places, it depends where the heat source is located and the area surrounding. (You can get warm air to travel downwards, or to the sides or radiate on all sides). Iirc that is the law of thermodynamics: "Heat cannot spontaneously flow from a colder location to a hotter location."

So if I put a heat source right at the edge of the earth's atmosphere who can guess what direction air will travel?
 
my general rule of thumb on an unprotected blade is .020" per side lost to decarb and finishing, if you plan for that you will have an edge at HT that is .040 plus or minus a few which will keep you from cracking and warping. I have been able to minimize my decarb layer by using charcoal to create a reducing atmosphere in my somewhat sealed kiln, but I still plan on losing at least .010 per side during the finishing process, and it works well for me

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