I get asked many questions regarding the construction of swords and one of the most popular is what kinds of steel do I think are best? If we are talking about a European medieval sword, which we usually are, then the characteristics of an alloy should satisfy several traits. First, the steel has to be suitably tough. It has to resist shock well. This blade is going to (or at least designed to) encounter wood, cloth, and other metals with regularity. To be able to do this and survive (not break) it must be able to b and manipulate the shock properly. Part of this ability has to do with design and heat-treatment but we are just discussing the steel itself. Second the steel must be able to hold an edge reasonably well.
In general we need to look at a steel with between 50 and 75 points of carbon in it. That means between 0.50% and 0.75% carbon. A little carbon goes along way. Over the years I have found that steels with a higher carbon content tend to be a little brittle when used in longer blades. Plain carbon steel like 1080 and 1095 work just fine but their toughness is somewhat less than the other steels we will discuss. Steels with less than 50 points of carbon are generally too soft and do not harden to a great degree, making a blade that will be tough as can be but won’t hold an edge and will stay bent if flexed. Alloys with between 50 and 75 points of carbon also help satisfy our other desire, holding an edge. A word about sword edges. It is not absolutely vital for a sword to have a razor sharp thin edge. Taking into account the physics involved you can (and I have on various test mediums) cause tremendous amounts of damage with a flat edge. Obviously a sharp edge will cut more efficiently. That is after all what we are looking for; the ability to end a hostile encounter in the quickest manner possible. A sharp sword helps meet this goal better than a dull one. So we definitely want a blade steel that will take and hold a good edge.
So what do I use?
Over the years I have tried several steels for sword blades. As stated previously, 1080 and 1095 work fine but tend to be a little brittle. A broken sword is just as bad as a bent one, if not worse. 1050, 1060, and 1075 are all excellent plain carbon steels with the right amount of carbon to satisfy our criteria. S-1 and S-5 are low alloy steels used for chipping and riveting pneumatic tools and as such tend to absorb shock very well. Their edge-holding ability leaves a little to be desired however. 5160 seems to be about ideal in my opinion. 5160 has about 60 points of carbon in it but also contains several other elements to increase its toughness such as chromium and silicon. Chromium increases the depth penetration of hardening processes and the responsiveness to heat-treatment. Silicon increases the tensile strength and hardenability of a steel. Both of these elements are found in small quantities in 5160 (less than 1% each) but this is enough to impart their desirable characteristics into the steel. 5160 is commonly used in automotive leaf springs (though I always use new steel bar stock, not recycled springs). It holds an edge quite well, and resists shock very well. This steel seems to me to be about ideal for non-laminated sword blades.
A note about stainless steels for sword blades. I have experimented with a variety of stainless alloys for swords blades including 420, 440, ATS34, 154CM, and they all exhibited a high degree of brittleness; they broke. Companies that use stainless steels for sword blades compensate for this by making the blades thicker and tempering them softer making the blade heavy, unwieldy, and unable to hold an edge well. To me this is unacceptable. I have tested blades forged from 5160 (made by myself and others) extensively through the years and with proper design and heat-treatment as well as good forging technique, they perform admirably.