Sunday, August 07, 2005
Knife Details
Blades
Material
Blades are usually made of steel(s); though there are a few knives using materials like high tech ceramic and titanium, these are very uncommon.
Stainless steels have gained popularity in the latter half of the twentieth century because they are highly resistant to corrosion (though they can rust under extreme conditions). Tests done by Razor Edge Systems, and described in their book "The Razor Edge Book of Sharpening" indicate that stainless steel knives hold an edge better than regular steels. Stainless and semi-stainless steels include D2, S30V, 154CM, ATS-34, and 440C. Chromium is the major alloying element in stainless steels, giving them the 'stainless' quality.
Steels having high carbon but low chromium content are prone to rust and pitting if not kept dry.
As of 2004 there are a variety of exotic steels and other materials used to form blades. Knife manufacturers such as Spyderco and Benchmade typically use 154CM, VG-10, S30V, and CPM440V (aka S60V), as well as high-speed high-hardness tool steels like D2 and M2.
Other manufacturers sometimes use titanium, cobalt, and cobalt containing alloys. All three are more ductile than typical stainless steels, but have quite a vocal support group despite concerns about health effects of cobalt content.
The craft of Damascus steel may be lost, but marketers today misuse it's name to apply to pattern welding, which creates layered and admired patterns. The cost of the process restricts it to high-end knives. There is typically more demand for exotic alloys in the utility, outdoor, and tactical or combat knife categories than there is in the kitchen knife category.
Forschner/Victorinox make decent, inexpensive kitchen knives; high-end manufacturers include Wüsthof, Global, Henckels and Böker (Tree Brand). Some manufacturers, particularly of kitchen knives, make ceramic blades; these stay sharp longer but due to their hardness chip and break more readily.
About Steel
All knife steel is martensitic, which means that small crystal grains and lattice irregularities, that make it hard, are formed as it cools from austenitic structure while hot to ferritic structure while cold. Knife steel has fairly low nickel content, because nickel tends to keep steel in the austenitic structure, even when cold. Stainless knife steels are high in carbon, but "carbon steel" means there is not also a lot of chromium.
Stainless steel is steel with very high (12–18%) chromium content. It is corrosion resistant (though knife steel is less so than higher nickel stainless steel) because, except in acid, one of the metals or one of the oxides is always stable. Stainless steel usually has particles of chromium (or other alloy metal) carbides.
These explain its reputation for long wear (the carbides are harder than the metal) and for being harder to sharpen and not taking as good an edge as rustable, low alloy ("carbon") steel (the ceramic particles themselves cannot be sharpened easily.) The bulk harness and toughness of stainless steel tend to be lower than those of low alloy steel.
Vanadium and molybdenum are important alloy metals because they make the gain size smaller, which improves hardness and toughness. Vanadium, and perhaps molybdenum, also increase corrosion resistance.
BLADE STEEL FACTS - CRKT
We select blade steels to achieve a balance of properties based on the anticipated use of the knife.
Steel is an alloy of iron, other metals and carbon. Stainless steel is a generic term for a family of corrosion-resistant alloy steels which contain 10.5% or more chromium. “Stainless” does not mean that these alloys will never stain or corrode, but that they “stain less” than steels which do not contain chromium.
Each alloy imparts different properties to the stainless steel. The chart at the bottom of the page shows in detail what each alloy element contributes.
All CRKT blades are either stamped, fine blanked, or laser cut from one of the high carbon stainless steels below. In selecting the appropriate steel, we look at the performance requirements of the blade, the knife price range, and our manufacturing and finishing methods.
There are trade-offs. While higher levels of carbon and final hardness levels keep an edge longer, they also make it more difficult to field-sharpen a blade.
Some premium alloys are low in nickel, and will stain if not kept clean and occasionally oiled after use. Consequently, we now feature AUS 8 as our premium alloy, which has compared very well to ATS 34 in performance tests conducted by international magazines.
Consider these examples: A mechanic who gives his work knife hard daily use, in contact with all types of solvents and moisture, will benefit from the durability, stain resistance and ease of sharpening found in 420J2 or AUS 4 steel. In contrast, the buyer of a CRKT Ultima or Alaska Pro Hunter expects a higher alloy steels, such as 1.4116 or AUS 8, with their exceptional combination of hardness and stain resistance.
Ductility, or toughness, has its place in knives that are subjected to hard us—or even abuse—as tactical and work knives must be, so we have selected higher toughness steels in many of these applications, as opposed to higher hardness steels.
Material
Blades are usually made of steel(s); though there are a few knives using materials like high tech ceramic and titanium, these are very uncommon.
Stainless steels have gained popularity in the latter half of the twentieth century because they are highly resistant to corrosion (though they can rust under extreme conditions). Tests done by Razor Edge Systems, and described in their book "The Razor Edge Book of Sharpening" indicate that stainless steel knives hold an edge better than regular steels. Stainless and semi-stainless steels include D2, S30V, 154CM, ATS-34, and 440C. Chromium is the major alloying element in stainless steels, giving them the 'stainless' quality.
Steels having high carbon but low chromium content are prone to rust and pitting if not kept dry.
As of 2004 there are a variety of exotic steels and other materials used to form blades. Knife manufacturers such as Spyderco and Benchmade typically use 154CM, VG-10, S30V, and CPM440V (aka S60V), as well as high-speed high-hardness tool steels like D2 and M2.
Other manufacturers sometimes use titanium, cobalt, and cobalt containing alloys. All three are more ductile than typical stainless steels, but have quite a vocal support group despite concerns about health effects of cobalt content.
The craft of Damascus steel may be lost, but marketers today misuse it's name to apply to pattern welding, which creates layered and admired patterns. The cost of the process restricts it to high-end knives. There is typically more demand for exotic alloys in the utility, outdoor, and tactical or combat knife categories than there is in the kitchen knife category.
Forschner/Victorinox make decent, inexpensive kitchen knives; high-end manufacturers include Wüsthof, Global, Henckels and Böker (Tree Brand). Some manufacturers, particularly of kitchen knives, make ceramic blades; these stay sharp longer but due to their hardness chip and break more readily.
About Steel
All knife steel is martensitic, which means that small crystal grains and lattice irregularities, that make it hard, are formed as it cools from austenitic structure while hot to ferritic structure while cold. Knife steel has fairly low nickel content, because nickel tends to keep steel in the austenitic structure, even when cold. Stainless knife steels are high in carbon, but "carbon steel" means there is not also a lot of chromium.
Stainless steel is steel with very high (12–18%) chromium content. It is corrosion resistant (though knife steel is less so than higher nickel stainless steel) because, except in acid, one of the metals or one of the oxides is always stable. Stainless steel usually has particles of chromium (or other alloy metal) carbides.
These explain its reputation for long wear (the carbides are harder than the metal) and for being harder to sharpen and not taking as good an edge as rustable, low alloy ("carbon") steel (the ceramic particles themselves cannot be sharpened easily.) The bulk harness and toughness of stainless steel tend to be lower than those of low alloy steel.
Vanadium and molybdenum are important alloy metals because they make the gain size smaller, which improves hardness and toughness. Vanadium, and perhaps molybdenum, also increase corrosion resistance.
BLADE STEEL FACTS - CRKT
We select blade steels to achieve a balance of properties based on the anticipated use of the knife.
Steel is an alloy of iron, other metals and carbon. Stainless steel is a generic term for a family of corrosion-resistant alloy steels which contain 10.5% or more chromium. “Stainless” does not mean that these alloys will never stain or corrode, but that they “stain less” than steels which do not contain chromium.
Each alloy imparts different properties to the stainless steel. The chart at the bottom of the page shows in detail what each alloy element contributes.
All CRKT blades are either stamped, fine blanked, or laser cut from one of the high carbon stainless steels below. In selecting the appropriate steel, we look at the performance requirements of the blade, the knife price range, and our manufacturing and finishing methods.
There are trade-offs. While higher levels of carbon and final hardness levels keep an edge longer, they also make it more difficult to field-sharpen a blade.
Some premium alloys are low in nickel, and will stain if not kept clean and occasionally oiled after use. Consequently, we now feature AUS 8 as our premium alloy, which has compared very well to ATS 34 in performance tests conducted by international magazines.
Consider these examples: A mechanic who gives his work knife hard daily use, in contact with all types of solvents and moisture, will benefit from the durability, stain resistance and ease of sharpening found in 420J2 or AUS 4 steel. In contrast, the buyer of a CRKT Ultima or Alaska Pro Hunter expects a higher alloy steels, such as 1.4116 or AUS 8, with their exceptional combination of hardness and stain resistance.
Ductility, or toughness, has its place in knives that are subjected to hard us—or even abuse—as tactical and work knives must be, so we have selected higher toughness steels in many of these applications, as opposed to higher hardness steels.
