The riddle of Steel

I am going to do my best to discuss the different types of steel used to make knives, I am not an expert but I have done much reading on the subject. I also handle thousands of knives so I can tell first hand what impact different steels have on your knives.

First of all, in almost all of my experience dealing with customers and their knives, I can count on my hands how many of them made a knife purchase decision based on the type of steel used.

Also......we have all heard the term "Surgical Steel" and have seen it stamped on some knives, I have on myself.  This is a marking thing. there is no such thing as surgical steel, it doesn't mean any knife that has that on it isn't good though, it is just stainless or a percentage of chromium has been added to the process to make it stainless. Surgical Steel just sounds cool, it can lure you in, don't let that be a factor in your purchase.


It is also important to realise that even the most precious steel elements that are used to make knives can go to waste so to speak if the forging process is not perfect, if the heating, quenching, annealing elements for the entire process are not meticulously followed then it doesn't matter that the premium alloys went into the furnace so to speak.

There is a few different types of steel categories:
Stainless;
Carbon; and
Powdered Steel.

I'm just going to discuss the first two, the powdered steel is more for tools.


I am sure you all have heard and believe that Carbon steel knives are superior to stainless steel knives, they can take a finer edge at a more acute angle and as the steel tends to be harder the edge retention is carbon knives is superior.

I am not absolutely convinced that this is true, it may be true and from what I have seen the carbon Japanese knives I have sharpened will take an incredibly sharp edge, truly something to see and feel to be appreciated.
However, there are some drawbacks to carbon knives and also, the quality of stainless steel over the years has improved greatly, I have some sharpen some amazing stainless steel knives which can still have a high carbon content, basically there has to be a certain percentage of carbon added to the composition.


In order for a steel to be deemed stainless it has to have a certain percentage of Chromium in its chemical composition, it's 11% but unless you are the one adding the ingredients so to speak, I guess that is not overly important, just know it is Chromium that makes steel  resistant to rust.

Stainless Steel........NOT surgical steel :)

Just like cooking ingredients, knife manufactures,  Blade Smiths use different alloys and other items like sand to increase things like strength, resistance to rust, edge retention,

These elements are......if you are going to make a knife, add these to your shopping list. (By the way, there is only a handful of certified Blade Smiths in the world (relatively speaking).

* Carbon - This increase hardness, tensile strength and edge retention;
*Chromium does the same but it increases resistance to corrosion;
*Cobalt - From what I understand this element improves all the other elements effects but increases hardness and strength;
*Molybdenum - This is common element on some high quality knives, it allows the maker to increase the hardness of the knife and also helps prevent corrosion;
*Vanadium - Sounds like a character in a video game but increases strength and toughness
*Tungsten - Does the same as the others but improves the ability to make the knife harder. 

OH and you need IRON :)

Why is carbon so important, what's the deal with carbon?
Well it is abundant, one of the most common elements on earth, we all have carbon in us but that doesn't mean it is good for knives does it?
Carbon increases hardness, it is bond able to other elements and in the eyes of many blade smiths, in Japan especially, it is the key element to extraordinary knives, extraordinary because of their ability to become razor sharp and hold the edge and also, easy to re-sharpen.
I am sure there are metallurgists out there who could talk for days on carbon, I'm not one of those.

I have sharpened many many carbon knives and this is what I know.

Yes they can take extremely intense edges and I do find them easy to sharpen. However, the owner needs to be aware that they are prone to chipping, not all of them of course but some are, the steel is hard and can be  brittle so if not taken care of properly they can be chip. This is why one shouldn't use a Steel hone of a carbon knife, the fatigued metal is too hard to flex and be pushed back into alignment, it can just break off instead, and that is what can cause chips.

I see this a lot but, it is easy to fix though and should not be a deterrent in purchasing one of these knives.

VG 10 steel, chipped as seen here

Same knife in front, easy to fix.

Carbon steel knives just need care, you just need to be aware that they will rust so keep them dry after use. The blades will change colour, despite your best efforts, this is not a bad thing, this Patina as it is called is often desirable in fact, it can look pretty cool and is not indication of the knife being dirty, it's one of the riddles of steel.

(FYI, I was in a store in NYC and handled a $3,500 knife and spoke to a chef about the knife he was purchasing and sharpening. I asked him about being afraid to scratch the blade of his new Yanagiba by using coarse stones on the blade path. He didn't care about that at all, the edge was what he made his living from.....this has nothing to do with steel does it......it's in interlude).


What about VG 10 steel, the steel in Shun knives for example.

This is very popular high quality stainless steel (remember it only needs 11% chromium to be called stainless) and it is high in Cobalt. It is said to have high edge retention but in my experience with Shun knives, and I have sharpened hundreds of them, the edge retention is lacking but the ability of the steel to take a nice edge is awesome, they can get extremely sharp and easily sharpened. Many masters of knife making use VG 10. I have had some really  nice VG 10 knives at home and found them all very easy to sharpen and capable of extremely sharp edges.

 Some knives like Global have the alloy content listed, although I don't think every realises what the letters mean, like CROMOVA which very likely indicates Chromium, Molybdenum and Vanadium.  (they must have put the letters there on the knives so the guys won't forget want ingredients to add when they make them.)

Global knives which are extremely popular are also easy to sharpen and take a nice edge, I have one and it's quite good, no problem at all yet with any chipping and edge retention is decent, not amazing but decent.

What about White # 1 --------what do the various colours mean ?

(I can tell you that it has nothing to do with the colours of the elements in the steel, the blades are not white or anything like that)

These days the main steel used in the forging of Japanese knives is YSS, Yasuki Speciality Steel which was invented by Hitachi Metals and has a high carbon content.  This top quality steel comes in different varieties, differing because of the percentages of other metals and other materials. So when the steel manufacturer sends the steel to the makers, the steel is wrapped in different colour paper to differentiate them. Now this could just be a paper sticker on the box or container, but that is where the colour comes from. It is just a method to distinguish the various types of steel.

Now there are steels that are used just for hand tools but lets talk about knife steels.

The information below comes from a book called Japanese Kitchen Knives. Essential Techniques & Recipes by Hiromitsu Nozaki ......a very nice book by the way, I love it.
So this is not informationI know right off the top of my head,  I had to read about it from various sources, I'm not taking credit for anything here folks, just passing info along.

Kigami - YELLOW PAPER
Carbon steel less impurities than the steel used to make tools, so it is used for low quality kitchen knives,  so you don't really want to get this steel although it is still high in carbon and capable to a great edge.......that great edge will vanish quickly though.


Shirogami - WHITE PAPER......Now we're talking!
This is the ultimate YSS product, the best steel with the fewest impurities. Now not everyone can forge with this steel, it is difficult and expensive but the trade off, the lucky folks who own knives made of of this steel speak of astonishing edges. Now they will rust easily so you need to take care of them but it is worth it.  There is White Steel # 2 which is undoubtedly and even better composition, more expensive and more rare but makes awesome kitchen knives. The highest quality of Japanese Traditional Knives are probably made from this steel.

Aogami (BLUE PAPER)

This is another common steel, common but great, it is made by adding some ingredients to Shirogami
such as Tungsten and and Chromium. I am pretty sure that this is the most common steel used in high quality knives. I have sharpened many blue paper knives and I always ask myself the same question after I am done........"why do I not own one of these knives"?

Aogami Super is the same steel but with the addition of Molybdenum and Vanadium.



Swedish Steel

Misono knives which are awesome to are made from this very high quality steel which comes from Sweden.

Obviously there are other types of steel out there but I'm going to stop here for the moment.

OK one more and one of my ultimate favourites.


52100 High grade carbon steel which is made from iron, carbon and a little Chromium.
This is the steel used by Master Blade Smith Bob Kramer and we all know how amazing his knives are. He is one heck of a sharpener  as well.

By the way, Bob Kramer's carbon knives have been rated by some cooking magazines as the best carbon knives available....anywhere.

I just happened to be looking at one today actually, they really are exceptional knives.

I really hope that some you have found this enlightening. This is not the be all and end all of Steel, but it covers a lot of the steel we see in the knives we use.

I almost forgot one of the super steels:


ZDP-189, a premium Japanese powdered super-steel made by Hitachi, hardened to RC 62-67, with very high carbide volume. Along with S90V, it boasts some of the best edge-holding of any steel on the market.

( I just cut and pasted that from a Google search)

I know some folks who own Spyderco knives (I want a Spyderco ) and the ones made from this steel are quite expensive and not easy to sharpen but the edge retention is exceptional. You can get kitchen knives made from this steel too.

The hardest knife I have seen is in fact not a Japanese hand made knife, not carbon. It is a Henckels Twin Cermax with a hardness of 66. This is a beautiful knife and one of the sharpest out of the box knives  I have seen.

Now MAC knives which are very nice as well and I highly recommend MAC, are composed of secret ingredients, we don't know the compound. MAC are sharp when new, very sharp and nice and thin.
Easy to sharpen. Did you know that the box that a MAC comes in, which is quite nice is hand made and there is only one family that makes them.
I will get some pictures and add them.

MAC Yanagiba

I've sharpened one of these, it's very nice.

MAC Yanagiba

Peter

(I will talk about the Rockwell hardness scale soon)