Spyderco byte May 2023 - EDGE-U-CATION

Understanding Equivalent and Comparable Blade Steels​

Blade steel is a complex and often overwhelming topic. For knife enthusiasts trying to understand the performance differences they might expect from the myriad of knife steels out there, it can be a steep and frustrating learning curve.

One way of flattening that curve—at least a little bit—is to understand that many steels can be accurately compared to other steels. In fact, in some cases, two or more steels with different names can be the exact same material. By learning to group steels into comparable families and identifying equivalent or near-equivalent steels, you can make sense of the “alphabet soup” of blade steels much more easily.

Steel Comparisons​

One of the most useful ways of understanding the performance potential of a steel is to compare it to a known entity—specifically, a steel with which you are already familiar. Often, the steel manufacturers do this for you, as the alloy composition of many steels is frequently based on the “fine tuning” of an earlier formula.

An excellent case in point of this process is Crucible® Industries’ progression from CPM® S30V® to CPM S35VN, to CPM S45VN™. The development of CPM S30V was driven by former Crucible metallurgist Dick Barber. He asked renowned knifemaker Chris Reeve why he used BG42 steel instead of one of Crucible’s available steels. Reeve felt that BG42 outperformed the Crucible steels available at that time, but said if Crucible could make something better, he would be willing to use it. Accepting that challenge, Barber interviewed a number of leaders in the cutlery industry—including Spyderco co-founder Sal Glesser—and based on their input set out to develop a steel that offered better toughness, edge retention, and corrosion resistance than BG42, yet was easy to grind and heat treat.

Barber began with the alloy composition of another well-known blade steel, 154CM. First introduced to knifemaking by the legendary Robert W. Loveless, 154CM was, itself, based on an earlier cutlery steel—440C. By carefully adjusting the carbon and molybdenum content of 154CM’s base formula and adding vanadium, Barber was able to achieve all his target objectives. Introduced in 2001, the result was CPM S30V, which still holds a well-deserved place as one of the world’s premier cutlery steels.

In 2009, Crucible released CPM S35VN, which was based directly on CPM S30V. According to the CPM S35VN data sheet, Crucible’s stated goal was to enhance the steel’s toughness and machinability as compared to S30V while sacrificing some edge retention. To that end, they reduced the vanadium content, added 0.5% niobium, and eliminated the purposeful nitrogen addition of S30V.

Ten years later, Crucible introduced CPM S45VN, which they designed to offer improved corrosion and wear resistance over CPM S35VN. It used niobium and nitrogen to replace some vanadium and carbon to rebalance the steel’s properties of edge retention, wear resistance, corrosion resistance, and toughness.

As you can see from this historical progression, blade steels are very often developed through the refinement of previous steels. By paying careful attention to the subtle changes steel manufacturers make to a steel’s alloy composition, as well as their stated goals for creating the new material, you can develop a good intellectual understanding of a new steel’s performance potential. Based on your own hands-on experience with its historical precedents, you can then have a clearer idea of what to expect from a knife featuring that steel. Obviously, the more experience you have using knives with different blade steels, the more “data points” you will have on which to base your expectations and your opinions.

Direct Inspiration​

Another way that steels are developed is by taking the alloy composition of a proven ingot steel and enhancing it through the powder metallurgy or particle metallurgy processes. With an ingot steel, the base steel is mixed with alloying elements to achieve the desired alloy composition. The perfectly mixed molten steel is then poured into a mold, cast into a large ingot, and rolled to shape it into usable form. During this process, the alloys within the steel have a natural tendency to “segregate,” or separate. This reduces the uniformity of the steel’s microstructure and diminishes the desired effects of those alloys.

Powdered steels, or particle metallurgy steels, use high-pressure gas to rapidly cool the molten steel as it exits the crucible. This turns the steel into a fine powder and “freezes” its alloys in their perfectly mixed state. The powder is then reheated under extreme pressure to create a steel billet that is then rolled to finished form. This advanced process greatly reduces the segregation of the alloys, creates a finer, more uniform microstructure, and enables the alloys to better affect the steel’s properties.

One of the early examples of a steel that received the “upgrade” to powder metallurgy form was 154CM, mentioned earlier. Using their CPM (Crucible Particle Metallurgy) process, Crucible supercharged this proven steel without changing its alloy composition. The resulting steel, CPM 154, has more uniform carbide distribution, enhanced toughness, improved corrosion resistance, and better wear resistance than its ingot counterpart.

Two other notable examples of this approach—both conceived and driven by Spyderco—are Carpenter’s CTS® BD1/CTS BD1N and our own proprietary CPM SPY27®. CTS BD1 began with Sal Glesser’s vision for a particle metallurgy version of the steel used in the very first Spyderco knives: Japan’s Gingami-1. A true workhorse steel with a good balance of edge retention, toughness, and corrosion resistance, the properties of GIN-1’s alloy composition were significantly enhanced by the powder metallurgy process to create CTS BD1. Later, Carpenter added nitrogen to the steel (the “N” in “BD1N”), improving its qualities even further and making it ideal for use in knives with acute, high-performance edges—like the Murray Carter® Collection Wakiita™ Series and Minarai™ Series.

Similarly, CPM SPY27 was the result of close cooperation between Spyderco and Crucible Industries to create a particle metallurgy expression of another tried-and-true Japanese steel: VG-10. Although SPY27’s alloy mix is slightly enhanced with the addition of niobium and more molybdenum, it is otherwise very comparable to VG-10. Its performance, however, is significantly better in all categories, thanks to the benefits of Crucible’s CPM process.

Equivalent Steels​

As mentioned earlier, the “alphabet soup” of steel names can be extremely confusing and overwhelming. One quick and easy way to cut through the confusion (pun intended), is to realize that different steel manufacturers regularly make identical or nearly identical steels with different names. Sometimes known as “proprietary equivalents,” these steels typically contain the same key alloys in the same proportions. Although there may be minor differences in alloy percentages or in the presence of trace elements, for all intents and purposes, these steels are identical. In most cases, the manufacturing method used to create the steels is also the same or nearly so.

For example, as noted earlier, Crucible’s 154CM is a stainless ingot steel that has a respected reputation in the cutlery industry. As a knife enthusiast, you may have also heard of Hitachi’s ATS-34 and Damasteel® RWL-34. Although those three steels have different names and are manufactured by three different companies on three different continents, they are virtually identical. For the record, so are Bonpertuis T113, Carpenter® Technology’s CTS® BD4 and CTS BD4P, and Latrobe’s 14-4CrMo. All have the same alloy composition and manufacturing method and, when heat treated to the same standard, can be expected to perform identically.

If you are the proud owner of a Spyderco Watu™, Stovepipe™, Zoomer™, or some of the limited-edition Exclusive models we have produced, you may be a fan of Crucible’s CPM 20CV—a particle metallurgy steel known for its exceptionally good edge retention and corrosion resistance. Based on your positive experience with that steel, you might be interested to know that 20CV is equivalent to Böhler-Uddeholm M390 and Carpenter’s CTS 204P. As such, if you were considering knives made with those steels—like the SpyOpera™ and Pattadese™ or the Exclusive models we have made with 204P, you would know what to expect and be able to make a more educated decision on your purchase.

Many astute knife users appreciate Crucible’s CPM CRU-WEAR® for its superior combination of wear resistance and toughness. If you are a fan of CRU-WEAR, it might be helpful to know that the advanced alloy composition of this steel is also available in more than a dozen proprietary equivalent steels, including Carpenter SB Wear, Carpenter Micro-Melt® PD1, Carpenter Micro-Melt PD#1, Carpenter PD1, Carpenter PD#1, International Tool Steel ITS Special, Latrobe LSS PGK, Latrobe PGK, Latrobe Lescowear, Lohmann PGK, Spectrum Metal Solutions Spectrumwear, Thyssen-Krupp TSP3W, Vasco Metal Vascowear, Vasco Metal Vasco Wear, Zapp US2000, and Zapp Z-Wear.

Another helpful hint: As you can see from the list of CRU-WEAR equivalents, often the same steel from the same manufacturer can be seen rendered with several different spellings. Websites, magazines, knife-blade markings, and other sources may introduce even more variations in their usage of the steel’s name. Almost always, these variations do not represent different steels or variants of the same steel, just inconsistency or the lack of a well-defined standard.

Understanding knife steels is challenging, but the less you have to remember, the easier it becomes. Hopefully, the information in this article will help you better understand equivalent and near-equivalent steels and make the topic a little less daunting.