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Simple steels can be normalized, such as 1095, etc, and even steels with less than 0.80 (ish) carbon can be normalized, such as 1055 and 5160. They also form carbides; the carbides are just correspondingly simple to go with the simple steels. In the case of 1095, the carbides are iron...

Kevin, is that 20% increase in toughness from industrial/academic research on marquenching or from your own heat treatment evaluations for your blades?

The big reason for equalizing and preheating is to minimize thermal stresses due to different temperatures within the same piece. Another reason is rapid heatinreg will temporarily increase the critical temperature. Rapid heating without time for equalization can result in incomplete...

I sent mine out to a local heat treater, but my formula was a fairly standard heat to 1750 F, hold at temperature for 30 min (as recommended above), quench in air (let cool in air), then double temper at 350-375. My target hardness was fairly high at 61 HRc. The shop tested it and was right...

I have heard Kevin say the opposite, that if a home freezer makes a significant change, it might be time to re-evaluate the HT procedure. On the other hand, it won't hurt most likely, so have at it. Cryogenic treatment is rife with odd tales and sound science at the same time. A good search...

IF it was hot dipped, you won't get rid of all of it short of grinding the entire surface. Zinc diffuses into the steel surface and forms a bond with the iron and causes the surface of the steel to form intermetallic compounds with the zinc. There is a little zinc for a considerable depth into...

Just so anyone new knows what is being discussed, they mean stainless steel foil, not aluminum foil.

My interpretation is that there aren't as many carbides to dissolve, just as you describe, but the distance between the carbides will be greater. Thus, even for a hypoeutectoid steel like 5160, a little soaking will ensure the carbon is evenly distributed in the larger spaces between the...

Doug, I think you and Kevin are talking about 2 different points during heat treatment. There won't be any cementite outside the pearlite, just as you describe, but when austenizing, there won't be any pearlite either, or we hope not. In any case, there will be more ferrite, which has...

Just as a picky point, normalizing and tempering without hardening in between wont help much. Welds and the associated heat affected zone around them could well cool fast enough to harden without water.

Just wondering what is the usual way to grind a petty, single (chisel) bevel or double bevel? I've seen double bevel ones here, and zknives.com says they're usually single bevel. I have material for a couple and wanted to know what the standard way was. To offer my opinion, I'd like to do...

Use 97 or 98 percent alchohol. It's sold in drug stores as hospital sterilizing grade. The lower % turn to dry ice slushies.

What do you consider a "carbon steel" ? 10xx only, low alloy steels like 52100 and 5160, high alloy steels like M2, A2, 3v?

I wouldn't call knives a complicated shape. Triangles are about as simple a cross section as you can get, next to round rods and rectangles. They are more complicated than these, but much more complicated stuff gets successfully treated all the time. Gears, splines, bolts, threaded rods...

Know thy steel.

There is something to be said for not getting ahead of ones self.

So can you give any specific examples you've seen of overquenched blades?

I dont think I'd be exagerating to say that if you use high carbon steel, its a safe bet you have a few quench cracks, microscopic though they may be.

Oh. They are differrnt, but go together.

What?