Help with translation from German.

[HoB]

Yes, searcher, that was a typo.

A few words as clarification: I tried to summarize a point that I though Landes wanted to make in his article, that a steel and blade in general should be optimized for its intended purpose. A blade intended to perform mostly pull cuts might benefit from a coarse grit finish, and maybe even a coarse grained steel. I tried to extent that argument to the heat treat as well that it might benefit from a heat treat that increases grain size, but I realize that I was not clearly thinking. While you might not want a heat treat that optimizes grain refinement, because you would like the edge a bit coarser grained, you would also lose toughness for example. So that was a goof. I am sorry.

Coarse grained means large carbides

AFAIK grain structure is not synonymous with carbide structure, so I believe this statement as such is incorrect and the heat treat has obviously an impact on the grain structure of a steel. However that grain structure is, as you say in your article, in the matrix (in the gum) not in the teeth (carbides). You might say that the grain structure in the matrix is irrelevant since the carbides "the teeth" as you call them do all the cutting. But I would very much disagree with that. A low alloy HC steel has very few carbides so it should be "toothless" and not be able to cut very well, but anybody who has been cut by a blade made from 1060 would probably disagree. But I think I understand what you want to say. In most knife steels with proper heat treat the grain size is mostly dependent on the carbides.

Mine do so, cause I make them myself all the way

Very impressive that you can make a low alloy steel at nearly full hardness at 64 Rc with an edge were you can observe visible deflection on transverse loading! The japanese chef knives that I have seen so far (which are clearly on the less expensive end of the spectrum but still more expensive than a Zwillings knife) are not as flexible. I like them nontheless.

I applaud you for trying to write a text to educate people that usually do not think about knife and cutting performance. I just felt that the tone and to some extent the layout of the article made the article mostly inaccessible for a general audience, precisely the audience that you seem to be targeting judging by the content. But of course this is simply a personal opinion. The above comments are more for the sake of the argument then actual disagreement with the content of your article.

 

[Cliff Stamp]

AFAIK grain structure is not synonymous with carbide structure, so I believe this statement as such is incorrect and the heat treat has obviously an impact on the grain structure of a steel.

There are two issues, the grain size of the austenite, which is retained in the steel after hardening, and the size of the carbides.

You might say that the grain structure in the matrix is irrelevant since the carbides "the teeth" as you call them do all the cutting. But I would very much disagree with that. A low alloy HC steel has very few carbides so it should be "toothless" and not be able to cut very well, but anybody who has been cut by a blade made from 1060 would probably disagree.

The arguement is generally that as a high carbide steel wears, the steel will wear around the carbides which increases the roughness of the surface, there are published papers on this for HSS. Of course you can easily leave the finish of any steel at a lower grit and it will easily outslice any coarse carbide steel when highly polished and will have better edge retention as well on a slice. Go low enough and AUS-4 will have better edge retention than S30V.

But I think I understand what you want to say. In most knife steels with proper heat treat the grain size is mostly dependent on the carbides.

Possibly more than the edge stability is more due to carbides, but this is problematic because if the steel is oversoaked and the austenite grains coarsen then lots of bad things start to happen. Maybe with optimal hardening carbide tends to dominate as grain sizes are more similar than carbide distribution in dissimilar steels, but such lines of reasoning tend to do little except confuse.

Very impressive that you can make a low alloy steel at nearly full hardness at 64 Rc with an edge were you can observe visible deflection on transverse loading!

Many low alloy steels have maximal torsional ductility at those hardness levels. The Japanese tend to in general use much higher carbon steels and in general to me seem to be far more brittle than they should be, often leading people to think that high hardness means minimal toughness. I would like to know exactly how they are hardened. The exact alloy also makes a lot of difference, note the difference in the responce of these two in terms of maximal deformation :

http://www.panix.com/~alvinj/graphA2vsO1.jpg

-Cliff

 

[HoB]

The martensite should also have a grain size.

 

[Cliff Stamp]

Yes, influenced by the austenite grain the finer it is, the finer the martensite. Generally most issues are critical therefore on the austenite grain and its grain boundries are nucleation cites for carbide precipitates and impurity segregates. It would also seem likely to me that they would directly influence edge stability if you consider them as essentially fault lines and think about their behavior in the edge of the knife itself and what would happen if they were to run along it.

-Cliff

 

[Roman Landes]

Well the steel used in the Yanagiba is the DIN Grade 1.1545 (C 105 W1) in the edge.
C ca. 1,05, Si 0,05, Mn 0,30, traces of p an S so very simmilar to white paper steel.
So the steel is hypereutectoid and after the HT there will be undissolved carbides

After welding it to a decor damascus strip of pure nickel and 1.1740 (C 60W) and with around 80 to 100 layers ans a strip of a gunbarel out of a leopard tank "by mistake (Thought i had a different steel)" the whole blade goes into the "repair shop"
Step1:
5 Times normalizing with quick "alpha-gamma-alpha" around 900°C frist than going down to 750°C.
Step 2:
Than the blade undergoes the sperodizing step to get the cementit on the grain boundaries "coped down" between 720 and 730°C 2-3 hrs soak than furnace cool.
Step 3: preheat to 600°C than 1st time Austenizing 850°C soak 3-4 min quench in oli 60°C
Step 4: than 2nd Austenizing 790°C soak 3-4 min (Temp sensor is always attached) quench in oil at 60°C (ends up between 67 and 68 HRC in the edge area depending o the thickness)
Step 5: Clean, and refrain from warpage at 100°C
Step 6: Temper between 160°C and 170°C 2 times for 1h ending at 65 to 64 HRC
Step 7: Check with "flextest".

This is how I do It