I don't know what is SG-2. So I have to do some googling:
This is very interesting generic info on PM. I can see that SG2 are hardened to 64HRC. Other info - again it is 64HRC and "finest in use today molecular structure".
Are you talking about kitchen knifes of folder?
What will it be?
What is the composition of this steel?
Thanks, Vassili.
Information I found:
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Unlike VG-10, SG-2 is powdered steel. To understand what this means, you have to understand what powdered steel is, how it is made, and what advantages it brings to the table. The best way to do this is to first compare the perfect steel to the perfect chocolate chip cookie. When making steel the term carbides gets used a lot. A carbide is the combination of the carbon and chromium molecule. These carbides give the steel is hardness and resistance to rust. Carbides can combine to create different sizes or end up clustered in some parts of the steel leaving other areas without their benefit. How is this like a chocolate chip cookie? Well imagine if you mix the chocolate chips aka the carbides into the dough unevenly, and make the cookies. You will end up with some cookies with too many chips and some with none. This of course ruins the flavor and texture of the cookie. In steel, what you get is weak points and corrosion. The challenge when making steel is to keep the elements and carbides evenly displaced. The problem arises that when you mix all of the elements in large quantities, the outer part of the mixture cools faster than the inner part and the elements start to separate. The carbides also start to form unevenly and in different sizes, just like a poorly made chocolate chip cookie. Its also kind of like raw milk from a cow. If you let it sit, the cream rises to the top, and the solids sink to the bottom. Turning the molten mixture into powdered steel is like pasteurizing the milk. Once the process is completed the elements no longer separate, just like when raw milk is pasteurized and becomes whole milk, the cream and solids no longer separate.
How do they do this? First they heat up all the iron and elements in their recipe into a hot molten steel soup, and then mix it all together till they have even dispersal of all of the elements throughout the soup. Then they spray the molten mixture through something that resembles a garden hose nozzle set on wide disbursement. As they do this, liquid nitrogen is also sprayed through the same nozzle and instantly cools down each micro droplet making a perfect mini ingot with perfect size carbides and element dispersal. From there, you reheat the powder and form it into an ingot using what we call the HIP process
The way they form the powdered steel in to a large ingot, is to put the powder mixture in to a big steel can. A steel disc covering the top of the can is welded on, and then all of the air is sucked out and replaced with argon gas. The can is then put inside an auto clave, which is a large pressurized chamber, and then the chamber is filled with argon and heated up. This is called the HIP process, which stands for Hot Isostatic Press. Heating the argon causes it to expand creating perfectly even pressure, perfectly compressing the powder in to the ingot. The reason you have argon in both the auto clave and the canister, is so you have equal pressure on either side of the can. If you had argon only on the inside or only on the outside of the can, it would either be crushed or explode as the argon expanded in the HIP process. It is important to note that we dont heat up the powder till it is molten, only enough for the ingot to form. If we made it molten again, then everything we accomplished by making it into powder in the first place would be undone. The elements would start to separate and the carbides wouldnt have even dispersal or uniform size. The reason they use argon as opposed to hydrogen which also expands greatly when it is heated, is because argon is inert. Hydrogen isnt. If hydrogen is exposed to just one spark under that type of heat and pressure, which is entirely possible considering what we are working with, it would create what we call in the manufacturing world, a really big BOOM. Imagine the Hindenburg. I am sure you can see why that could be considered a bad thing. The end result is a perfect large ingot with absolute density, perfect grain structure, and perfectly even element and carbide dispersal ready for the rolling mill, where it is pounded down and clad with an SUS410 cover to form the blank for our Shun Elite. Similar to what we do for regular Shun.
What is the advantage here? Well imagine that steel is like fabric. Regular stainless steel would be like burlap. Strong but with lots of holes and hard to cut and sew. VG10 would be like denim. Much tighter weave easier to cut for sewing and a lot more durable. SG2 would be like fine silk. Super fine threads for maximum density, super flexible, easiest to cut and sew, and definitely the strongest fabric that will last the longest even though it is the thinnest. In all of the cutting steels that I have come across in my 17 years of housewares, SG2 simply blows everything else away for performance, edge retention, and re-sharpening. Because of the powderizing and HIP processes, you end up with an alloy that has a much higher density and grain structure with no imperfections or weak points. Just like silk. This allows us to increase the Rockwell hardness to 64, and the edge will still have flexibility so it wont chip, and can be re-sharpened. Even if it is paper thin.
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The core of a Shun Elite knife is SG-2 exotic powdered steel that is hardened under heat and pressure into a dense and hard alloy. The Rockwell (Hardness) rating of Shun Elite is 64, as compared to most kitchen knives ranging from 56 to 58 Rockwell. The SG-2 molecular structure is the finest in use today, resulting in an edge that lasts longer than any other available today. The edge is smooth and incredibly sharp, yet will still respond quickly to a honing rod when necessary.
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