There are three basic blade materials for modern Japanese style swords, these are: steel (commonly called carbon steel), stainless steel, and non-steel alloy (commonly called alloy).
Steel: Commonly called carbon steel - which is redundant - all steel by definition contains carbon. Steel is simply iron with carbon added. The carbon makes the iron stronger. There's nothing magical about carbon steel. Here's a breakdown of the various types of "plain" carbon steel and what they're good for:
Plain Carbon Steels
These steels are iron, usually (but not always) with less than 1 percent carbon, plus small amounts of manganese, phosphorus, sulfur, and silicon. The characteristics of these steels are primarily a product of carbon content, although the alloying and residual elements do have a minor influence.
Plain carbon steels are divided into four groups:
1. Low
2. Medium
3. High
4. Very high
Low. Often called mild steels, low-carbon steels have less than 0.30 percent carbon and are the most commonly used grades. These steels are too soft to hold an edge, and would be easy to bend with use. Some display swords are made from mild steel. Stainless is preferred because neither is fully functional and stainless looks better.
Medium. Medium-carbon steels have from 0.30 to 0.40 percent carbon. Increased carbon means increased hardness and tensile strength, with decreased ductility. These steels are too soft to hold an edge, and would be easy to bend with use. Some display swords are made from medium carbon steel. Stainless is preferred because neither is fully functional and stainless looks better. Carbon content of .40% is an important threshold; steel with a carbon content of .40% or greater can be hardened, below .40% it cannot be hardened.
High. With 0.45 to 0.75 percent carbon, these steels are capable of sword quality hardening, can hold an edge well, and make a good sword. Remember that a sword is not just a big knife. A functional sword will be subjected to stresses that a good knife has nightmares about!
Very High. With up to 1.50 percent carbon content, very high-carbon steels are used for the highest quality knives and functional swords.
The lowest carbon content usually found in functional swords is .45%, and this would be called 1045 carbon steel. The highest carbon content commonly found in swords is .95%, and this would be called 1095 carbon steel. The "10" that precedes the percentage indicates that it is plain carbon steel. Another prefix you might see is "52", as in 5260 steel. The "50" family of prefixes indicates the chromium content, and is usually used in spring steel.
The higher the carbon content, the more expensive and harder it is to work with, and the higher the price. Lower carbon steels are easier to forge and sharpen, but don't hold an edge as well.
Stainless Steels
There are many types of stainless steels which fill a variety of roles. For the purpose of this discussion, there are four basic types. All of them contain varying degrees of carbon, manganese, chromium, and vanadium, as well as a few other ingredients. It is the quantities and ratios of these ingredients which give each type its characteristics. It should be noted that although a very high quality functional knife can be made from stainless steel, it is impossible to make a fully functional sword from stainless. There are some stainless swords that can be used for Aikido, Iaido, and kata, but a stainless sword should never be used for tameshigiri; it will either bend or break, and usually on the first swing.
Here are the four types commonly used in swords and their general characteristics:
420, 420J and 420J2: Quite soft and not very rust resistant. Very inexpensive and easy to grind, so lots of cheap swords can be made very quickly. Swords made from these steels should do nothing but hang on the wall; even swinging one could break it.
440A: Soft but extremely rust resistant. Treat these swords as you would one made from 420 steel; it will look better than 420 steel, but will be very prone to bending. You could probably store a 440A sword in salt water and not have it rust; good quality diving knives are made from 440A.
440B: Harder than 440A, but less rust resistant. A good quality sword made from 440B can be used for Aikido, Iaido, or kata if the blade is thick enough and the tang is long enough (it doesn’t have to be a full tang, but it should be at least eight inches long and not be a rat-tail), but won’t be suitable for tameshigiri. Again, good quality diving knives are often made from this type of steel.
440C: The hardest and least rust resistant in the 440 family. These are the most functional stainless swords, but still can’t be used for tameshigiri.
Swords marked “440” not followed by an A, B, or C are usually A or B. Contrary to popular belief there is no such thing as “plain 440”.
There are other families of high quality stainless (such as D-2) that are used for knives, but not for swords, so that will be the topic of another review
Steel: Commonly called carbon steel - which is redundant - all steel by definition contains carbon. Steel is simply iron with carbon added. The carbon makes the iron stronger. There's nothing magical about carbon steel. Here's a breakdown of the various types of "plain" carbon steel and what they're good for:
Plain Carbon Steels
These steels are iron, usually (but not always) with less than 1 percent carbon, plus small amounts of manganese, phosphorus, sulfur, and silicon. The characteristics of these steels are primarily a product of carbon content, although the alloying and residual elements do have a minor influence.
Plain carbon steels are divided into four groups:
1. Low
2. Medium
3. High
4. Very high
Low. Often called mild steels, low-carbon steels have less than 0.30 percent carbon and are the most commonly used grades. These steels are too soft to hold an edge, and would be easy to bend with use. Some display swords are made from mild steel. Stainless is preferred because neither is fully functional and stainless looks better.
Medium. Medium-carbon steels have from 0.30 to 0.40 percent carbon. Increased carbon means increased hardness and tensile strength, with decreased ductility. These steels are too soft to hold an edge, and would be easy to bend with use. Some display swords are made from medium carbon steel. Stainless is preferred because neither is fully functional and stainless looks better. Carbon content of .40% is an important threshold; steel with a carbon content of .40% or greater can be hardened, below .40% it cannot be hardened.
High. With 0.45 to 0.75 percent carbon, these steels are capable of sword quality hardening, can hold an edge well, and make a good sword. Remember that a sword is not just a big knife. A functional sword will be subjected to stresses that a good knife has nightmares about!
Very High. With up to 1.50 percent carbon content, very high-carbon steels are used for the highest quality knives and functional swords.
The lowest carbon content usually found in functional swords is .45%, and this would be called 1045 carbon steel. The highest carbon content commonly found in swords is .95%, and this would be called 1095 carbon steel. The "10" that precedes the percentage indicates that it is plain carbon steel. Another prefix you might see is "52", as in 5260 steel. The "50" family of prefixes indicates the chromium content, and is usually used in spring steel.
The higher the carbon content, the more expensive and harder it is to work with, and the higher the price. Lower carbon steels are easier to forge and sharpen, but don't hold an edge as well.
Stainless Steels
There are many types of stainless steels which fill a variety of roles. For the purpose of this discussion, there are four basic types. All of them contain varying degrees of carbon, manganese, chromium, and vanadium, as well as a few other ingredients. It is the quantities and ratios of these ingredients which give each type its characteristics. It should be noted that although a very high quality functional knife can be made from stainless steel, it is impossible to make a fully functional sword from stainless. There are some stainless swords that can be used for Aikido, Iaido, and kata, but a stainless sword should never be used for tameshigiri; it will either bend or break, and usually on the first swing.
Here are the four types commonly used in swords and their general characteristics:
420, 420J and 420J2: Quite soft and not very rust resistant. Very inexpensive and easy to grind, so lots of cheap swords can be made very quickly. Swords made from these steels should do nothing but hang on the wall; even swinging one could break it.
440A: Soft but extremely rust resistant. Treat these swords as you would one made from 420 steel; it will look better than 420 steel, but will be very prone to bending. You could probably store a 440A sword in salt water and not have it rust; good quality diving knives are made from 440A.
440B: Harder than 440A, but less rust resistant. A good quality sword made from 440B can be used for Aikido, Iaido, or kata if the blade is thick enough and the tang is long enough (it doesn’t have to be a full tang, but it should be at least eight inches long and not be a rat-tail), but won’t be suitable for tameshigiri. Again, good quality diving knives are often made from this type of steel.
440C: The hardest and least rust resistant in the 440 family. These are the most functional stainless swords, but still can’t be used for tameshigiri.
Swords marked “440” not followed by an A, B, or C are usually A or B. Contrary to popular belief there is no such thing as “plain 440”.
There are other families of high quality stainless (such as D-2) that are used for knives, but not for swords, so that will be the topic of another review
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