Spyderco byte December 2023 - EDGE-U-CATION - Salt Series Steels

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Spyderco byte December 2023 - EDGE-U-CATION - Salt Series Steels​


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Salt® Series Steels​

Since its introduction in 2003, Spyderco’s best-selling Salt® Series has set the cutlery industry standard in ultra-corrosion-resistant cutting tools. The key component of that series was H-1, a remarkable blade material that offers an exceptional balance of cutting performance and extreme corrosion resistance. In the two decades since then, the metallurgy of blade steels—including corrosion-resistant steels worthy of inclusion in our Salt Series—has evolved tremendously. Also, due to the far-reaching effects of the COVID-19 pandemic, the world’s steel manufacturing industry has experienced significant changes.

Currently, our Salt Series features four blade steels that are extremely resistant to corrosion. To help you choose the steel—and the knife—most appropriate to your needs, we would like to provide a quick synopsis of the advantages and disadvantages of each.

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H-1:​

The original Salt Series steel, H-1, was developed by Myodo Corporation in Japan. H-1 is an austenitic steel, which means it does not go through the traditional hardening and tempering processes of martensitic steels. Its unique alloy composition includes chromium, manganese, molybdenum, nickel, nitrogen, phosphorus, and only minimal amounts of carbon. This combination of elements allows it to be precipitation hardened during production. Also called age hardening, this process uses controlled heat to increase the tensile and yield strength of the material.

The real secret to H-1’s hardness, however, is the transformation of its retained austenite to hard martensite through the rolling of the steel. It begins as a 7mm-thick sheet and is progressively rolled down to the required finished thickness—typically 3.0mm or 2.5mm, depending upon the Spyderco model. The extreme compressive forces of this rolling process transform some of the steel’s austenite to hard martensite, increasing the overall hardness of the material without sacrificing its toughness or corrosion resistance. The result is a blade that holds an edge reasonably well, is incredibly strong and flexible, and offers extreme resistance to corrosion.

The disadvantage of H-1 is that it does not achieve the same degree of hardness as martensitic blade steels, so it offers less edge retention—especially in a PlainEdge configuration. For this reason, H-1 performs best in fully serrated SpyderEdge blades. Its unique properties also require H-1 blades to be hollow ground during production.
Currently, the only knives still in production using H-1 are Spyderco’s original Autonomy™ automatics. Once the steel for these knives is exhausted, they, like other H-1 models, will be transitioned to H-2.

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H-2:​

As the third largest steel producer in the world, Japan was particularly hard hit by the effects of the COVID-19 pandemic and was forced to restructure its steel industry. One of the consequences of that change was that H-1 could no longer be produced by its original mill. Fortunately, through close cooperation with our manufacturing partners in Japan, Spyderco was able to drive the development of a worthy replacement steel, appropriately named H-2.

In simple terms, H-2 takes the time-tested alloy composition and manufacturing processes of H-1 and refines them even further. The result is a steel that retains all the extraordinary qualities of the original, while being readily manufacturable.

Like H-1, H-2 is an austenitic steel that does not go through the traditional hardening and tempering processes of traditional martensitic steels. Instead, its austenite structure is transformed to hard martensite through intense rolling and cold-working processes. H-2’s finely tuned alloy composition rebalances all the original elements of H-1 and also adds a small amount of copper. The result is a steel that faithfully delivers the impressive strength and toughness of its predecessor while actually enhancing its extreme corrosion resistance—especially for use in saltwater environments.

Spyderco’s extensive in-house testing of H-2 has shown that its performance is very consistent with H-1. It is, without a doubt, the most corrosion-resistant blade steel currently available. It is also extremely tough and resilient. However, like H-1, its limited hardness makes it best suited for serrated edges and, in manufacturing, it must be hollow ground.

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LC200N:​

The Salt Series earned legions of devoted fans around the world. Fisherman, commercial divers, water sports enthusiasts, military personnel, and other demanding end users all appreciated having cutting tools that were well designed, incredibly tough, and fearlessly corrosion resistant. Over time, however, some of these end users began asking for Salt knives that offered better edge retention in a PlainEdge format. Some also expressed interest in full-flat-ground blades that offered thinner edge geometry.

To meet these needs, Spyderco went in search of other steels that could provide the extreme corrosion resistance necessary for a Salt Series knife, while satisfying these other performance requirements. One steel that “made the grade” was LC200N.

Manufactured by Zapp in Germany, LC200N is classified as a high-nitrogen, alloyed tool steel produced by the Pressurized Electroslag Remelting (PESR) process. The origins of the material, however, go back to a steel called Cronidur 30, which was manufactured by Krupp. Classified as a medium-carbon stainless steel, Cronidur 30’s most unique quality was the addition of 0.30%-0.50% nitrogen to its alloy mix. This allowed it to achieve a working hardness of 60-61 HRC—making it very suitable for knife blades. It is also noteworthy in that it is NASA’s material of choice for the ball bearings used in spacecraft.

Introduced in 2013, LC200N takes the same alloy mix as Cronidur 30 and uses the PESR process to increase the cleanliness of the steel and refine its microstructure. The result is a martensitic steel that can be heat treated to achieve working hardnesses of 60-62 HRC—higher than that of H-1 or H-2—while still offering a high, though not equal, degree of corrosion resistance. This, and the fact that it can be full-flat ground during manufacturing, make it an excellent choice for use in corrosion-resistant PlainEdge knives. LC200N is also easy to machine—a quality that also makes it easy to sharpen.

The disadvantages of LC200N are that its corrosion resistance, although excellent, still does not equal that of H-1 or H-2. It is also not an inexpensive material, so knives produced with it cost somewhat more than comparable H-2 models.

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CPM® MagnaCut®:​

One of the most exciting developments in knife steels in recent years has been CPM MagnaCut. Conceived by Dr. Larrin Thomas, a PhD in Metallurgical and Materials Engineering and the son of renowned custom bladesmith Devin Thomas, MagnaCut represents a uniquely different approach to stainless steel metallurgy that offers an unparalleled synergy of toughness, edge retention, and corrosion resistance.

The inspiration for MagnaCut began with Thomas’ fascination with Crucible® Industries’ CPM S30V, a powder metallurgy stainless steel developed specifically for use as a knife steel. Early powder metallurgy steels like CPM S60V®, Elmax, and M390 combined vanadium with a high chromium content (17-20%), resulting in steels that offered good wear resistance and corrosion resistance, but relatively low toughness. The culprit was the high chromium content of these steels, which created chromium carbides and a coarse microstructure that was detrimental to their toughness.

Non-stainless powder metallurgy steels like CPM 3V, CPM 4V, and Vanadis 8, have small vanadium carbides that provide excellent wear resistance and a finer microstructure, but at the expense of corrosion resistance.

In developing CPM S30V, Crucible decreased the chromium in the steel to limit the formation of large chromium carbides. Interestingly, this allowed the other alloys in the steel matrix to form carbides and left more chromium “in solution” in the steel. Chromium in solution enables the steel to form a microscopic layer of chromium oxide on its external surface, which is what protects it from rust.

Based on this principle, Thomas’ idea was to reduce a steel’s chromium content even further while adding other alloys to promote the formation of smaller, harder, wear-resistant carbides. After much trial and error, he found a narrow range of carbon and chromium content that would provide hardness and adequate chromium in solution for corrosion resistance. At the same time, he added vanadium and niobium to promote the formation of vanadium and niobium carbides for wear resistance and toughness.

MagnaCut is capable of achieving relatively high hardness—over 63 RC after conventional heat treatment and 64-65 RC with the added benefit of cryogenic treatment. This gives it edge retention is on par with respected blade materials like CPM S35VN, CPM 4V, and CPM CRU-WEAR. In terms of toughness, it surpasses even non-stainless steels renowned for their toughness, like CPM M4 and A2. Its most surprising quality, however, is its outstanding corrosion resistance, which approaches, but does not equal, that of Vanax and LC200N. Interestingly, even after cryogenic treatment, those steels can only achieve a hardness of 60-61 RC. MagnaCut can achieve higher hardnesses, while still offering outstanding toughness and excellent resistance to corrosion. Based on Spyderco’s extensive in-house testing, its level of corrosion resistance was impressive enough to make it worthy of inclusion in our elite Salt Series.

MagnaCut is a truly remarkable steel that offers a unique balance of properties. Although it is less corrosion resistant than LC200N, it offers the best edge retention of our Salt steels. And while it is not as tough as H-2, its toughness is impressive and outshines that of LC200N.

Choosing a blade steel is always a balancing act between the competing qualities of edge retention, toughness, corrosion resistance, and ease of sharpening. This is particularly true when you use your knife in or around the water where corrosion is a serious concern. Spyderco’s Salt Series offers an unparalleled choice of state-of-the-art, ultra-corrosion-resistant blade steels. No matter which one you prefer, we’ve got you covered.
 
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