When it comes to blade steels, there are four factors that affect the blade’s performance which are: edge stability, abrasion resistance, tensile strength, and corrosion resistance and each of these qualities is affected by the size of the carbides formed during melting. Therefore, the perfect blade steel is strong, hard, tough, abrasion resistant, corrosion resistant, and holds an edge well. However, several of these factors are inversely proportional to one another. For instance, by increasing hardness, you decrease toughness and by increasing toughness, you decrease hardness. So, if you make the steel too hard, it may break or shatter in use but, if you make the steel too soft, then it won’t hold an edge.Consequently, hard blades steels tend to have more stable edges and greater resistance to microchipping but, by the same token, tough steels withstand impact far better because the edge tends to roll instead of chipping. In addition, each of these factors can be controlled to some extent by adding or leaving out certain elements from the alloy as well as adjusting the quantities of the elements added and precisely controlling the heat treating process. Consequently, stainless blade steels are often thought of as being hard steels whereas, high carbon, non-steels are often thought of as being tough steels.
So, what are the common elements added to steel to create blade steel alloys and why are they added?
- Carbon – This mineral transforms Iron into Steel when 2 % or more is present. However, only a mere 0.8+% can be absorbed by the iron and thus, the balance in extremely high carbon steel increases hardness. Also, Carbon serves to increase edge retention, hardness, tensile strength, and wear and abrasion resistance. Expressed as C.
- Chromium – Used in quantities greater than 10.5%, it produces stainless steels. Also, during melting, Chromium and Molybdenum form hard, double carbide, bonds which help improve both the abrasion resistance and the corrosion resistance of the steel.In addition, Chromium serves to increase hardness, toughness, tensile strength, and wear and abrasion resistance. Expressed as Cr.
- Molybdenum – Used to help improve the hardness, abrasion resistance, and corrosion resistance of blade steels. During melting, Cr and Mo form hard, double carbide bonds and it also it serves to increase hardness, toughness, tensile strength, and wear and abrasion resistance. Expressed as Mo.
- Vanadium – Helps to produce a fine grain during heat treat. Also it improves wear resistance and refines the gain structure for both good toughness and the ability to sharpen to a very keen edge. In fact, many people report that they are able to get knives using steels that contain Vanadium shaper than they can non-Vanadium steels such as ATS-34. Also, Vanadium serves to increase hardness, toughness, tensile strength, and wear & abrasion resistance. Expressed as V.
- Manganese – Increases toughness and hardenability in steel and helps to produce a fine, dense, grain structure by reducing the size of the carbides. Also, it serves to increase tensile strength and wear and abrasion resistance. Expressed as Mn.
- Nickel – Adds strength, toughness, and corrosion resistance to steel. Also, it serves to increase tensile strength and wear and corrosion resistance in steel. Expressed as Ni.
- Tungsten – Helps to produce a fine, dense, grain structure. Expressed as W.
- Cobalt – Increases strength and hardness, and permits quenching at higher temperatures. Also, it intensifies the individual effects of other elements in more complex steels. Expressed as Co.
- Silicon – Increases tensile strength in steel. Expressed as Si.
Furthermore, steel is defined as Iron with a Carbon content greater than 0.2% and a high carbon steel is defined as one that contains at least 1.0% Carbon by mass (although some manufacturers cheat by billing steels containing 0.5% to 0.8% Carbon as high carbon steels) and yet, steel can only absorb a maximum of 0.8% Carbon. Therefore, any additional carbon contained in high carbon steels serves to increase the hardness of the steel. In addition, according to which definition you prefer (I have found four different definitions so far), a stainless steel is defined as one that contains a either minimum of 10%, 11%, or 12% Chromium content by mass and the higher the Chromium content is, the more corrosion resistant the steel is. But, to be truly considered a stainless steel, it must contain at least 14% Chromium. Last, it should be noted that although Nickel is a far less common element in blade steels than Chromium, it serves the same purpose. So, what are the pros and cons of stainless blade steels versus those of high carbon non-steels? Well the answer to that question is as follows:
A high carbon tool steel is defined as any steel that contains at least 1.0% Carbon but less than 2.1% Carbon (any more than 2.1% and the resulting alloy is called “cast iron” instead because it is too hard to forge but is machineable). Also, non-stainless steels are less expensive to produce than most stainless steels, they have a high tensile strength and thus excellent impact resistance and thus they are far easier to forge than stainless steels, they are often significantly easier to sharpen and take a finer edge than stainless steels, and they can be differentially heat treated to create a hard edge with a ductile spine. On the other hand, non-stainless steels often don’t hold an edge as well as stainless steels and thus require sharpening more often and they are more prone to corrosion and thus, they require more care than stainless steels.
High Carbon photo example example below: Spyderco Lil’ Lionspy C181GTIP, Elmax Blade Steel, G-10 & Titanium Handle
By definition, stainless steel is Iron that contains at least 10.0% Chromium which then forms a sesquioxide-based surface oxide that adheres to surface of the steel and prevents corrosion. In turn, this locks the material into the Ferrite phase which is body-centric, moderately strong, and not too ductile. Also, stainless steels tend to do a better job of resisting corrosion and they tend to hold an edge better than non-stainless steels. On the other hand, stainless steels are more expensive to produce than non-stainless steels, they are difficult to forge, they can be brittle, and they can be difficult to sharpen.
A fine stainless steel photo example below: the ESEE 4P-MB-SS, stainless Stonewashed, 440C, Canvas Micarta Handles
So, as you can see, there are both advantages and disadvantages to knife blades made from either non-stainless or stainless steels. Therefore, when choosing a blade steel for any particular application, it is imperative that you choose the type of steel that best suits your purpose. Thus, for knives that will see use a heavy-duty chopping tool such as a large Bowie, a Parang, or an Enep, then a non-stainless tool steel is the best choice. But, for knives that are expected to take and hold and edge for extended periods of use such as hunting knives and chef’s knives, stainless steels are a better choice. In addition, some people like the patina that develops after a while on non-stainless steel knife blades while others absolutely hate it thus, to each his own. But, regardless of whether you choose a non-stainless steel or a stainless steel, it is important to do so with the pros and cons of each type of steel in mind.