S7 steel is the ideal combination of hardness and malleability that makes for a good knife. It’s fully capable of retaining an edge while being tough enough to withstand a lot of pressure and wear.
The elements in S7 also make it resistant to electricity, which makes it very useful for all sorts of tools and knives. I want to discuss the properties and answer a few of the frequently-asked questions about S7 steel and explain why it makes such great knives.
What is S7 Steel?
There are many different metals and steels, but S7 is most-used in tools because of how functional it is. S7 steel is strong enough to retain an edge in knives, but not so high on the hardness scale that it can’t be compressed easily.
The main thing that this steel is known for is its resistance to shock and electricity, which is perfect for power tools and electric blades. However, I love to use S7 steel in knives as well. They stay sharp for a long time, don’t break, and are reliable.
Of course, the negative is the low amount of chromium which means that it needs to be cleaned or oiled more often than other steels. Let’s talk composition.
What are the Properties of S7 Steel?
Everything is made of elements and knives are no different. The main 2 that I pay attention to when it comes to making knives are carbon and chromium. There are, of course, other elements involved but these 2 set the foundation.
In this case, S7 steel generally has 0.5 percent of carbon and around 3.5 percent of chromium. Carbon in knives means how hard it is and how long it can retain an edge. Half a percent might sound low, but this falls right around the average amount.
While that means that S7 isn’t as hard as other steels, that doesn’t mean it’s weak. In fact, S7 steel is fun to forge into knives because of how it hardens into such a strong blade. That’s also why it’s used in many tools, because it lasts and it passes several tests that I’ll go into later.
Chromium is responsible for a knife’s resistance to the elements, especially moisture and liquid. Unfortunately, S7 steel is susceptible to humidity or other acidic substances like blood or sweat. As long as you keep it clean, though, an S7 knife will suit most of your needs.
What is the Hardness of S7 Steel?
On the Rockwell Hardness, or HRC, scale that all steels are measured on, S7 steel fully hardens between a 60 and 62 but I like to try for somewhere between 54 and 56. It’s slightly lower than the harder steels, like 52100, but it can still take punishment and hold an edge.
The reason I go with a lower hardness is because hardness doesn’t determine how good a knife is. Hardness affects the blade strength and edge, but a 54-56 hardness means that the knife will be easier to keep sharp.
One of the interesting features of S7 steel for a forger like myself is the way that it hardens. While some steels need to be quenched and molded, S7 steel air-hardens or hardens with oil. This makes it easier to work with, because I can make more in a shorter span of time.
I will say that the hardness of S7 steel in no way indicates that it’s not a strong piece of metal, because it definitely holds its own.
Will S7 Steel Rust?
Because of the low amount of chromium in the composition of S7 steel, it can fall prey to oxidation of moisture on the blade. If you take the knife in a humid environment or use it while hunting, you’ll need to clean and oil your blade soon after or during if you stay out there.
One of the best ways I’ve found around this issue is to coat your knife in protective oil. While it will eventually need to be cleaned anyway, the lack of weather resistance won’t be as much of a problem.
How Strong is S7 Steel?
What S7 steel lacks in resistance to the elements, it more than makes up for in toughness. It’s one of the stronger steels available for knife making because of how much it can withstand when it comes to work and impact.
There are a handful of tests to determine the strength of steel and the findings of S7 tell me that the steel is a lot stronger than the hardness or carbon levels might indicate. The resistance to shock is nice, but it also has a very high impact resistance.
S7 steel can take a great deal of compression without cracking, meaning that the steel itself is extremely strong. Add on the fact that it has a high melting point and S7 steel quickly becomes a strong contender.
I use heat treatment to temper my knives and some metals can crack or warp under the heat and pressure. If that happens, I don’t use it for making knives but S7 has never given me a problem. It’s soft enough to shape without losing strength.
Is it Easy to Sharpen S7 Steel Blades?
As I mentioned earlier, when I make an S7 knife I like to keep the hardness a little lower than maximum to make it easier to sharpen. Even at the highest possible hardness, though, the edge of S7 steel isn’t difficult to maintain.
A rule of thumb in knives is that harder steel is harder to sharpen, so S7 steel can take relatively longer to sharpen than something in the low 50’s or high 40’s. Still, because of the hardness it won’t need to be sharpened as often as those lower numbers.
Especially with the right coat or oils on it, S7 blades can last a long time and be easy to sharpen.
In short, S7 steel is one of the most versatile steels out there for tools and blades. It’s very resistant to impact and shock and can retain an edge for long periods of time. While it can be vulnerable to the elements and wear, a knife made from S7 steel is trustworthy.
The potential range of hardness allows for me to forge a knife that requires some maintenance without worrying about the actual steel chipping, warping, or breaking with use. I recommend S7 steel with confidence in a blade.