SG2 and R2: Japanese powder
Let us start with the confusion over names, because here it is the main issue. SG-2, R2 and SGPS are one and the same steel. SG-2 is the maker’s designation, R2 is a second name for the same grade, SGPS is the name Fällkniven sells it under. SG stands for “Super Gold”; there is no gold in the steel, it is an internal grading of quality.
It is made by Takefu Special Steel — the same company that produces VG-10. Stated hardness is 62–63 HRC.
What “powder” means
Ordinary steel is cast and forged. Powder steel is first atomised into powder and then sintered into an ingot under pressure and heat. The procedure has one point: carbide size.
The wear resistance of a steel is determined by three things — the hardness of the steel itself, the hardness of the carbides and their quantity. More carbides and harder carbides mean the edge lasts longer. But carbides are hard and brittle, they make it easier for a crack to start, which means edge chipping and broken tips. Hence the fundamental fork in the road: wear resistance against toughness.
The way out of that fork is known: make the carbides small. For a given quantity of carbide, a fine carbide gives the same wear resistance with greater strength. Powder metallurgy delivers exactly that — in atomisation the carbides start out very fine.
Powder is not about “cleaner steel” in the advertising sense. It is about the hard inclusions not having time to grow.
The price of stainlessness
And here is the limitation that descriptions of powder stainless steels usually keep quiet about.
For a steel to be stainless it needs a lot of chromium. Chromium ties up carbon into chromium carbides — and those are softer than vanadium carbides, and in a powder steel they grow faster because they are less stable. As a result any powder stainless carries a substantial volume of chromium carbide, and its balance of strength and edge retention is worse than that of powder non-stainless steels alloyed with vanadium.
This is not a verdict on SG-2, it is a description of the class. Powder stainless is a compromise: you pay in toughness and you get a knife you do not have to wipe to death after every tomato.
What this gives you in the kitchen
The old argument that “carbon steel cuts better than stainless” used to be true: stainless steels were softer, duller and harder to sharpen. Powder alloys like SG-2 closed that argument. Hardness, acceptable strength and corrosion resistance now come in one piece of metal, and carbon steel has kept exactly one indisputable advantage — it is cheaper to make.
The practical side of high wear resistance cuts both ways, and that is worth thinking about in advance. The same property that makes the edge wear down slowly against food also works on the sharpening stone. A steel that holds an edge several times longer takes several times longer to sharpen.
Where you find it
SG-2 turns up in kitchen knives and in pocket knives. Kai uses it in the Shun Elite line, Fällkniven under its own name SGPS, including in the small U2.
With hardness it is the same story as everywhere else: Shun Elite knives are officially stated at 64 HRC, but there are signs that they are actually hardened to 62. Two points on the Rockwell scale is roughly a twofold difference in how long the knife lasts until the next sharpening, so the question is not academic.
Opinions differ on short pocket blades: it is possible that this steel suits them less well than it suits kitchen knives.
The neighbour: SRS-15
While we are on Japanese powder, SRS-15 stands next to it — also a Japanese powder steel, 63–65 HRC. Its carbon content is very high, and combined with tungsten and vanadium that gives very high wear resistance; it hardens without trouble to 64–65 HRC.
On stated figures SRS-15 looks stronger than SG-2. It is met noticeably more rarely — among kitchen knife makers Akifusa, for instance, works with it. That is, on the whole, the usual fate of a good steel: being in the catalogue and being in the shop are different things.
Who needs it
SG-2 is a step from VG-10 towards edge retention without giving up stainlessness. The step is real but small: a couple of points of HRC and a finer structure.
It makes sense if you are genuinely tired of sharpening and are prepared to sharpen less often but for longer and with the right stones. If your knife goes blunt not from work but from the dishwasher, a glass board and attempts to open a tin — powder will not help. It will chip in exactly the same way, only more expensively.