Is that possible? (steel expert required)

molletta

molletta

Joined
Sep 1, 2004
Messages
1,598
I chop a blade knives with my Nexus,
I give a strong blow, sparkes exited, a piece steel detached on the second blade and knit on the blade of Nexus.

What is temperature that blade cath up?







 
When the two blades collide, it is possible for the shock to be high enough so that the steel can fracture. This is especially possible if you are chopping because it is very dynamic and there is a lot of twisting because people don't apply forces in perfectly straight lines. Thus pieces of metal from one blade can get stuck in the edge of another blade.

-Cliff
 
at that concentrated impact you can sort of "spot weld" two metals together, or at least squish them together fast enough that they tend to stick to each other, it happens alot when chopping into soft metal (like aluminum) with a hard steel blade.
 
I suspect the phenomena is related to galling (like in ball-type bearings without sufficient lubrication). That might be a good model anyway; in which case, a book or paper should have the basic equations to estimate the temperature at contact. Just a matter of finding them.

High stress in a relatively small area, deformation, and friction. Mmmm.

Well, anyway, thanks for the pictures. I've never seen that with knives (and haven't seen it much at all, when I think about it.)

Why did you do it, anyway?
 
Yes , it's cold welding [ the definition of galling] so it doesn't take any heat to do it !!
 
Sorry, molletta, I came to your test after I read this post.

"All metals are surrounded by surface layers (oxide) which must be disrupted if they are to be welded. Cold pressure welding, carried out at ambient temperature, relies upon the use of high compressive pressures. This provides interfacial deformations of 60% to 80% that break the oxide layers to expose fresh, uncontaminated metal that makes contact. In this state, interatomic forces take over to produce the weld."

You'd think some heat would be generated. Not sensible, perhaps, but something due to the molecular/granular movement.

Ah ... whatever.
 
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