1095 Steel -- Anatomy of a classic steel
The term “knife” can describe a seemingly endless array of products, from folding and automatic knives to fixed blades and skeletonized tools. The knife industry designs and manufactures widely various creations to meet an equally wide array of needs for numerous types of users. As a result, the people who make knives must work their way through a long list of decisions to determine and define the look, performance, and task application of each blade they create. Perhaps the single most important decision on that list concerns the selection of the steel that forms the centerpoint of the knife’s functional components: Its blade.
More so than at any time in the history of the knife industry, 21st century knife makers can select from a lengthy roster of blade steels, each with its own balance sheet of advantages, disadvantages, strengths, and weaknesses. In that selection process, no attribute or combination of specifications equals perfection. Some knife makers show a preference for certain steels on the basis of these metals’ abilities to demonstrate specific characteristics, but every steel represents an individualized balancing act among pluses and minuses. Enhance one attribute and another one suffers in a seesaw reaction. Many of the decisions among blade steels come down to choices between hardness and toughness, edge retention and ease of sharpening, corrosion resistance and toughness, and so on.
Modern metallurgy has formulated inventive solutions to the age-old problems that confront knife makers. For example, some alloy steels raise edge retention to unprecedented levels, but the metals themselves require advanced skills to sharpen correctly and effectively. At the same time, however, some knife designs call for the relatively old fashioned virtues of an easily sharpened blade that achieves a good edge and meets rugged working tasks with enduring toughness. For those applications, some designers reach for the tried and true performance of 1095 carbon steel.
Basic Steel Categories
Once you understand how 1095 steel fits into the category of carbon steels, and how carbon steels compare to other types, you can begin to visualize the basic criteria that help shape some of the choices among blade steels for an individual knife. Carbon steels consist of relatively simple mixtures of only a few elements. Along with the iron foundation that serves as the starting point for any steel, carbon steels incorporate varying amounts of the element that gives them their designation (between 0.12% and 2.00%), along with small amounts of other elements.
The American Iron and Steel Institute’s limits on the elemental chemistry of carbon steel state that it must not contain more than 1.65% manganese, 0.60% silicon, or 0.60% copper, and that it must not require more than a minimum of 0.40% copper. Additionally, a carbon steel formula must not require any minimum amount of many of the other elements that give alloy steels their performance characteristics, including the chromium, molybdenum, nickel, and vanadium frequently found in complex alloys, as well as cobalt, niobium, titanium, tungsten, and zirconium. In fact, the formula must not specify virtually any mandatory content other than iron and carbon.
The designation “1095 steel” represents the classification applied to the metal under the SAE International numerical system of steel categorization. Under this system, the first two digits of a four-digit classification represent the main element or elements added to iron to produce a particular type of steel. The last two digits represent the percentage of carbon in the formula. In the case of 1095 steel, the leading digit “1” identifies the metal as a carbon steel, the “0” shows that it contains no secondary alloying element, and the “95” represents its carbon content. Among carbon steels, 1095 steel carries the further limitation that its carbon content should not exceed approximately 1.00%. 1095 steel also includes 0.35% to 0.50% manganese, less than 0.05% sulfur, and less than 0.04% phosphorus.
Elements and Performance
Metallurgists build alloy formulas from a list of elements that add specific characteristics to and subtract specific limitations from the resulting metal. More isn’t always better. Some elements produce undesirable characteristics as the amounts of them increase. In most cases, each addition to elemental chemistry represents a tradeoff between two attributes.
Carbon, the element that transforms iron into steel, adds hardness, wear resistance, and edge retention. Chromium represents the hardest element in the periodic table, conferring hardness and wear resistance, along with corrosion resistance. Cobalt boosts hardness and toughness, and can multiply the effects of other alloying elements. Copper increases corrosion resistance. Manganese increases hardness and wear resistance, and can help remove oxygen from steel during production processes. Molybdenum raises hardness, toughness, and corrosion resistance. Nickel contributes to toughness at the same time that it reduces hardness. Niobium can replace carbon and produce a tough, hard alloy with corrosion resistance. Phosphorus boosts hardness but can lead to brittleness in large amounts; some metallurgists consider it a contaminating factor rather than a desirable part of an alloy recipe. Like manganese, silicon helps remove oxygen during steel production; it also helps increase hardness. Sulfur typically qualifies as a contaminant rather than a component, reducing toughness, although tiny amounts of it can make a steel easier to machine. Tungsten increases hardness and toughness. Vanadium helps develop toughness, wear resistance, and corrosion resistance. Titanium cuts weight, bumps up toughness and corrosion resistance, and can assist in building wear resistance.
In contrast to complex elemental blends, 1095 steel takes a far simpler approach to building a recipe for steel.
Non-Stainless Versus Stainless Steels
Unlike the relative simplicity of carbon steels, alloy steels rely on complex chemistries that add other elements to boost certain desirable performance attributes and minimize weaknesses that can limit knife blade endurance, performance, and versatility. Tool steels consist of high-carbon steels with added chromium, molybdenum, tungsten, and vanadium. Stainless steels depend on the percentage of chromium in their alloy chemistry to qualify for that designation.
The basic AISI categories start with carbon steels at “1” and move on to list eight alloy steels, each designated by the first digit in its classification number. The “2” series contains nickel. A “3” designates nickel-chromium formulas. Molybdenum steels’ classification numbers start with “4.” The leading digit “5” indicates chromium steels; the “6,” chromium-vanadium formulas. A “7” points to tungsten as the main alloying element. The “8” series includes nickel, chromium, and molybdenum. Finally, the “9” series incorporates silicon and manganese.
Beyond alloy steels, other formulas point to additional performance characteristics. Stainless steels must contain a minimum amount of chromium to carry that designation, typically between 12% and 14%. These alloys excel at corrosion resistance, and show greater amounts of wear resistance than carbon steels can muster.
1095 Steel: Attributes and Performance
Although 1095 steel is categorized on the basis of 0.95% carbon, its formula actually can contain anywhere from 0.90% to 1.03% of the element, depending on who manufactures it and what the steel maker’s customer requests in a specific production batch. Because of that carbon content level, 1095 qualifies as a high-carbon steel.
High carbon content can correlate with brittleness, which explains why 1095 steel rarely becomes the choice for long or thin blades, either of which could accentuate this drawback catastrophically at inopportune times. That potential negative balances out with the positive side of high-carbon steel, namely its toughness and durability. Those attributes make 1095 steel a popular choice for rugged bushcrafting and survival knives, applications that rely on and require a hardy blade stock, and typically use thick fixed blades. High-carbon steels such as 1095 also show up in springs and saw blades, both of which benefit from its toughness, in bladed farm equipment, and in wire.
Among the 10-series of carbon steels, the higher the numeric designation, the greater the percentage of carbon in the steel, and the correspondingly greater degrees of wear resistance. At the same time that carbon content climbs, toughness drops in one of the metallurgical tradeoffs that typify steel production. 1095 steel strikes enough of a balance among the pluses and minuses of carbon steels to serve as the most-popular choice for blade creation among the “10xx” series.
Perhaps the biggest negative among 1095 steel’s list of performance attributes is its innate lack of corrosion resistance. Devoid of any chromium or other elements that contribute to a steel’s ability to resist the forces of oxidation, 1095 steel can fall prey to humidity, moisture, salt, acidic foodstuffs, and any other rust-inducing forces it encounters.
Three approaches typify knife makers’ approach to countering 1095 steel’s vulnerability to oxidation. Hot bluing can add some corrosion resistance to 1095 steel. Some knives ship with coated blades designed to isolate the steel from its environment, preventing oxidation by adding protection against the cause of it. Other knives include a coating of oil designed to serve as temporary protection, and a recommendation to reapply a fresh coat as needed.
1095 Steel in Knife Production
Knife makers choose 1095 because of its hardness, workability, easy sharpening, and modest price. Stainless steels can cost four times as much as 1095 steel; steels produced through particle metallurgy can cost 10 times as much as standard carbon steels.
The two principal methods of knife blade construction include forging and material removal. Forging involves shaping the steel through hammer blows after heating it enough to make it workable. To harden the material, knife makers can heat the steel, quench it in oil or water to drop its temperature quickly enough to reach the desired performance, and then reheat the metal to temper it. The handmade process of forging becomes impractical if and when the knife maker chooses to produce blades in quantities greater than the smaller production levels common among new artisans and those who work as one-person enterprises.
For forging purposes, 1095 steel offers the types of characteristics that make it relatively easy to use successfully. Depending on the desired attributes of a finished knife, the steel can be edge quenched to produce a high degree of hardness for edge retention and cutting performance, leaving the rest of the blade slightly softer to give it enough toughness to withstand bending without breaking.
In addition to its suitability for forging, 1095 steel also lends itself equally well to production processes that rely on blankable metal. This process of material removal uses a water jet, laser, or wire to cut blade shapes—blanks—out of sheet steel.
The desirability of an individual steel for a specific knife making task comes down to factors beyond the elements incorporated in the recipe used to produce it. Heat treatment can make or break a particular steel, transforming it either into a hard, tough blade capable of accepting a productively sharp edge, or a brittle slab of metal that chips, fractures, and makes a better paperweight than a knife.
In addition to traditional knife design and production, 1095 steel also makes an appearance in the more-nearly exotic material known as Damascus steel. Produced from a combination of two steels, one bright, one dark, Damascus steel displays swirls and whorls of patterning like something visible through a black-and-white kaleidoscope. The two steels merge together through a forged welding process, followed by an acid etching step that accentuates the patterns formed as the metals fold together in layers. These patterns can form random or preplanned shapes. The origins of the Damascus steel production process lie in attempts to overcome the weaknesses of ancient steels and produce battle-ready blades. The byproduct of the production steps yields an aesthetic result prized in and of itself as a precious metal, regardless of any practical strengths it displays in a functional blade.
Some consumers prize Damascus steel for the ancient traditions it invokes. Although modern methods of producing this exotic two-metal blend may differ from the long-lost techniques the ancients would have used, the resulting steel carries a mystique based on its millennia of history as a prized material for swords and other weapons.
Because 1095 steel lacks so much as a trace of chromium or any other elements that could contribute to corrosion resistance, knives made from it require special care and attention to avoid the development of rust from environmental exposure to oxidizing substances and conditions. Simply wiping a 1095 steel knife dry may not remove all traces of contaminants from its blade. For example, if you cut citrus fruit with a 1095 steel blade, or work with such a knife in or near a body of salt water, you will need to clean the blade beyond what a cursory swipe with a cloth can accomplish. Likewise, if you store your knives in a basement workshop, the natural tendency toward developing and holding moisture that typifies many below-grade spaces can mean that your knife begins to rust from exposure to the humidity in the air. Unless you live in a desert climate, the same problems can develop if you keep your knives in a garage.
Many knife owners believe that the best place to store a blade is in the protective sheath that accompanied it when it shipped. Unfortunately, the converse holds true, especially for a carbon steel such as 1095. Leather sheaths absorb moisture and become sources of rust rather than protective shields against it. Thermoplastic sheaths can harbor moisture from environmental exposure or from the act of being cleaned.
To protect knives made from 1095 steel when you store them away, clean and dry them thoroughly, and apply a light, even coat of oil to their blades with a dry cloth before you place them in a humidity controlled environment. Refer to the knife manufacturer’s recommendations when you select the oil. Additionally, consider investing in desiccant packets like the ones many knife manufacturers include in their product boxes when they ship out new purchases to consumers. Dehumidifying your workshop, or choosing a better location with less moisture, also helps cut down on the risk of oxidation. It’s wise to check your knives frequently so you can avert any trace of oxidation before it appears on 1095 steel.
Elemental Alloy Formulation Comparisons: 1095 High-Carbon Steel vs. 440C and D2