Metallurgy of Steel for Bladesmiths- Dr. Verhoeven

[Mike Brubacher]

Can't speak for Scott, Jan but I know that you know that I'm not in that family.

[scott.livesey]

not sure what the Tesla family means.  i know Tesla developed multi phase AC, according to some accounts radio transmission and was not given the money or recognition he deserved.  I retired from USN in 1993, so I know things have changed a bit.  because of experience with automated systems, I worked factory maintenance till 2015 when I retired and had my left knee replaced.  
here are more resources, Tool Steels 5th edition by Roberts and Krause http://allaboutmetallurgy.com/wp/wp-cont...Steels.pdf  more in depth than the Verhoeven book, it covers all tool steel classes.
http://allaboutmetallurgy.com/wp/library-books/  lots of books about steel

[me2]

Well, Scott just killed my weekend.

[scott.livesey]

Well, Scott just killed my weekend.

sorry about that, I haven't even listed some of the university portals out there with lots and lots of papers about steel, even some steel that might make a good knife.
here is an all time classic Bain on Steel Alloys https://www.phase-trans.msm.cam.ac.uk/20...cbain.html
then look here https://www.phase-trans.msm.cam.ac.uk/index.html

[Rupert Lucius]

Well, Scott just killed my weekend.

sorry about that, I haven't even listed some of the university portals out there with lots and lots of papers about steel, even some steel that might make a good knife.
here is an all time classic Bain on Steel Alloys https://www.phase-trans.msm.cam.ac.uk/20...cbain.html
then look here https://www.phase-trans.msm.cam.ac.uk/index.html

Scott

Have you done any destructive testing on actual knife blades - yours or someone else's?

It would be impossible for me to destroy a blade with destructive testing.

[scott.livesey]

not on purpose. an early knife, that did not have a good temper, was dropped and broke into 3 pieces. was putting on a new handle and had the tang break while trying to open pin hole.
i do not have the equipment to evaluate the testing. the grinder, the etching solutions, a microscope. even with this equipment, all you can tell is grain size and maybe carbide distribution. I make kitchen knives. what useful information have I gained if I find that hitting the spine with a 3 pound hammer can force the blade thru a cinder block?
the basic high carbon steels used in knives, W1/1095, O1, O7, & 52100 have been used and tested by industry for a long time. you read what is out there and some common information on heat treat and performance shows up. when these steels are heated to 1485*F, +/-15*F, held at that temperature long enough to heat thru/stabilize, quenched in oil(W1/1095 need very fast oil), tempered twice for an hour at 350*F to 400*F they have finest grain size, least size change, best combination of hardness, charpy toughness, and torsional toughness.

[Rupert Lucius]

not on purpose.  an early knife, that did not have a good temper, was dropped and broke into 3 pieces.  was putting on a new handle and had the tang break while trying to open pin hole.
i do not have the equipment to evaluate the testing.  the grinder, the etching solutions, a microscope.  even with this equipment, all you can tell is grain size and maybe carbide distribution.  I make kitchen knives.  what useful information have I gained if I find that hitting the spine with a 3 pound hammer can force the blade thru a cinder block?  
the basic high carbon steels used in knives, W1/1095, O1, O7, & 52100  have been used and tested by industry for a long time.  you read what is out there and some common information on heat treat and performance shows up.  when these steels are heated to 1485*F, +/-15*F, held at that temperature long enough to heat thru/stabilize, quenched in oil(W1/1095 need very fast oil), tempered twice for an hour at 350*F to 400*F they have finest grain size, least size change, best combination of hardness, charpy toughness, and torsional toughness.

Scott

Testing to me would be more like securing the blade in a stump or vise and bending the blade 90* and bending back to the vertical, making a visual  inspection for cracks and etc. if any.

My microscopes are looking glasses somewhere between 10/20 power.

Rupert

[scott.livesey]

Scott

Testing to me would be more like securing the blade in a stump or vise and bending the blade 90* and bending back to the vertical,  making a visual  inspection for cracks and etc. if any.  My microscopes are  looking glasses somewhere between 10/20 power.
Rupert

an interesting test but what do the results tell you?  I doubt any knife I own would bend 45* without breaking or being permanently deformed.  to flex 90* and back is a function of geometry and, to a lesser degree, heat treat.  it would make a 'cool' video, but really tells us nothing about how the knife will perform.  
  with the BESS tester, knifemakers now have a sharpness standard that is becoming accepted.  so now instead of saying my blade can shave or cut newsprint, I can say a BESS score of 100, send the knife to another tester and he should get the same score.

[me2]

A bit of information on the Iron Carbon phase diagram. I feel like I left out a lot, but it was intended for knife knuts, and there's quite a bit that doesn't apply to them.


https://www.youtube.com/watch?v=lOJHrkh__SQ

[Mark Reich]

Unfortunately for me, I find about 98% of Dr. Verhoeven's writing doesn't really apply to me, directly. Not that it isn't interesting, and helps discussing things with proper terminology, and gives you some guidelines.

In fact, the only source of information specific to me, in my shop, using my equipment, has been generated by me. I think a lot bladesmiths are likely to feel that way. There are just too many variables. It's very similar to reloading high power ammunition. As a rule, shooters won't use the same load in seemingly identical firearms.

I've heard of full hardened 52100 at temps as low as 1430°, held for an hour. Likewise, I don't often hear of 1 hour tempering cycles, but I'm certainly not going to second guess your methods.

I just expect the average EDC blade will break long before you get to 45°. Means nothing to me. I actually own a couple hundred knives like that. I didn't make them.

Destruction testing doesn't apply to kitchen knives remotely as much as it would EDC knives, or hunting/survival knives.

I generally consider all my non-kitchen knives to be survival knives, and I damn sure want to know exactly what to expect out of them. Bolting a large torque wrench to a blade held in an immoveable vice, and measuring strength at 45°-90° flexes is the only way I can guarantee my knives will perform acceptably To Me.

If a blade is capable of a 90° flex or two, how likely is that knife to break- no matter what? That's the point. No matter what. Beat it with a sledgehammer, If You Have To. I know it won't break.

Yes, blade geometry is a large factor, especially when your blade is 1/16" thick. Or 1/4" thick, but nowhere near as important as differential heat treating an average 1/8" thick blade. I expect one of my "average" blades to flex to 45° and spring back most of the way immediately. If I leave it sitting there in the vise overnight, I expect it to keep straightening. I expect that to keep happening many many times.

I don't expect anyone except HEPK bladesmiths to continuously test knives like this. Nobody HAS to. I WANT to, especially with any blade that isn't almost perfect.

I Expect that to mean nothing to anyone else... unless you're buying a knife from me.