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I looked into this a while ago. If you haven't yet, I recommend the section in Verhoevens book for bladesmiths on grain size and its effects on hardenability. He took 1080 down to an ASTM size of 14 or 15 on a wedge shape 1 inch wide and 1/4" thick at the spine, 1/32" at the edge. When...

What is the purpose of etching such a blade? Or any blade for that matter?

I think you may be on to something with the differences in ovens. There's no way to tell if one person's 375 is another's or not, without actually testing it. Most HT specs give a range for this reason. If my Goodwill toaster oven is off by 25-50 degrees, I won't cry too much, but if my $1500...

It is true that fusion welded joints are supposed to be stronger than the base material, but that has more to do with what filler is used and the design of the joint/weld. In tensile testing to qualify welding procedures, you want a break in the base material, not the heat affected zone or the...

Hey again Ed. Do you have any micrographs of what Rex described? Did he say anything aboutseeing differences between the different regions/microstructures of the blade?

Wonderful. Another night of productivity lost to reading. Thanks Tai.

Interesting. I'll have to investigate this further. Everything I've read up to this point has pointed to some sort of brittle failure when grain boundary fracture occurs. Impurities that segregate to the boundaries, prior austenite grains with carbide not fully disolved, liquid metal...

So when martinsite fractures, do you mean along the boundaries between plates or laths, or along the prior austenite boundaries? Industrially, you can end up with all kinds of things mixed together. Ask Page about the nickel super alloys. But there is a very good reason for each there, and...

Right on there Doug. The complexity of controlling bainite is why it only got honorable mention above. From the standpoint of eliminating a seemingly unneeded tempering step, proper bainite formation is way too involved. I have had people ask if one could just quench and get the hardness...

Exactly. Exception is when we want undisolved carbides for wear resistance, so in that sense, my example of 1095 was probably a bad choice. I'll remedy that. However, as you said, for the sake of keeping it simple, and for the simpler steels like 1084 and lower carbon contents, everything...

Just a caveat to all this. Mixed structures aren't always undesirable, but to start mixing them, we need to know what properties we're after and which structures to mix. Let's deal first with the undesirable mixtures, as this is what would lead to the ability to heat something like 1080 and...

For the sake of new members to the heat treating forum, a quick review of the phases we could get from heat treating steel is in order. Austenite: this is the structure we're after during the initial heating before the quench. The structures below come from changes in austenite as it cools...

I was thinking about this last night and thought it might be a topic others have wondered about as well. In all my reading of various shop talk forums, no one has really addressed this in detail. Much has been made of hardness testing and many more makers are using it to check on the...

I go as thin as I can hold. The last knife I reground was 0.015" behind the edge after sharpening on the slack belt at ~20 degrees per side. This was a large chopper with a 12" blade. I reground my old Buck Scoutlite all the way to a sharp edge flat to the belt, then back sharpened on the...

Can/have you asked your heat treater what they do? Can you specify the heat treatment you want? I test knives in all kinds of ways, appropriate to the knife. My first kitchen knife revealed some issues when used to chop into wood (simulated whacking of a cutting board). My last outdoor knife...

That is a fairly complex question. Many elements are ferrite stabilizers. These elements, such as chromium, raise the temperature at which austenite begins to form from ferrite. This is one of the reasons stainless steels have austenizing temperatures higher than carbon and low alloy steels...

Secondary hardening occurs from the precipitation of chromium carbides and molybdenum carbides and from conversion of retained austenite from the higher tempering temperature followed by cooling. Retained austenite conversion is good, as is the precipitation of carbides for high temperature...

Not kevin, but hopefully my answer will do. Eutectic starts as a liquid and goes to a lamellar pearlite like structure while eutectoid starts as a solid (austenite) and goes to a lamellar structure, like pearlite.

The hardening temperature of 9260 is higher than 5160. The stuff I found show up to 1650 F for hardening. Hypoeutectoid steels typically have higher hardening temperatures, and the high silicon content pushes it up more.

Ed, how was it determined that the last blade you tested broke along the grain boundaries? I ask because I have not seen any information that does not point to grain boundary fracture as an indicator of a problem, at least in knives and related ambient temperature uses.