Originally Posted by Toudiyama[NL]

Often took months of work to finish a high grade sword for a high ranked samurai
lower raked would get the more quickly made swords

following a piece about the production

Production methods
Japanese swords and other edged weapons were manufactured by an elaborate method of repeatedly heating, folding and hammering the metal. This practice was originated from use of highly impure metals, stemming from the low temperature yielded in the smelting at that time and place. In order to counter this, and to homogenize the carbon content of the blades (giving some blades characteristic folding patterns), the folding was developed (for comparison see pattern welding), and found to be quite effective, though labour intensive. Contrary to popular belief, this does not result in super-strength of a blade.
The distinctive curvature of the katana is partly due to the differential heat treating it is subjected to. Unlike swords produced in many other locations, Japanese smiths did not harden the entire blade, but only the cutting edge. The hardening process will make the edge part of the blade contract less than the untreated steel when cooling down, something that aids the smith in establishing the curvature of the blade. The combination of hard edge and soft back of a katana and other Japanese blades is what cause them to be resilient and yet retain a good cutting edge.

Though seeming to be an indestructable blade, if the sword is not wielded with proper technique, the edge can be easily warped or rolled from the cutting of nearly any material (soaked reeds for example) resulting in lower effectiveness as a weapon.


Composition
Traditional Japenese Steel is considered to be one of the best for creating swords. The total composition varied from smith to smith and load to load of ore.
One more modern formula (from WWII) Called for:

composition: 0.04% molybdenum
0.05% tungsten
0.02% titanium
1.54% copper
0.11% manganese
0.1% to 3% carbon
a varying amount of silicon
and a few other traces
Iron was the balance (made up the bulk of the steel).


The high percentage of carbon gave the blade strength while the silicon increased the flexibility of the blade as well as its ability to withstand stress. Katanas were designed only to cut flesh, so the composition was not always adequate to effectively break armor.


Technique
The katana is designed for two specific functions, cutting and thrusting. Rather than slashing, chopping or slicing, the sword is made to cut through a target in a straight line. Cuts that do not cut all the way, or follow an arc on their way through the target can easily result in a warped or rolled edge.
There are other reasons for the curvature of the blade. Samurai were primarily cavalry, often charging on horseback into battle. A curved blade is much more effective in a cavalry charge than a straight one. This is the same reasons we see curved sabres given to officers and cavalry units in Europe and America in the 17th and 18th centuries.

While some people believe that katana and wakizashi were all the same, this could not be further from the truth. Tachi and no-dachi were also used (these being longer than katana), and katana themselves varied tremendously. They were often forged with different profiles, different blade thicknesses, and varying amounts of niku. Wakizashi were also not simply 'scaled down' katanas, they were often forged in hira-zukuri or other such forms, which were very rare on katana. Katana were more like eastern equivalent of rapiers, one wouldn't use a katana on an open battlefield (yari, naginata, yumi, and other such implements were preferred) very often, and in battles, they served as a secondary weapon.


Myths
Many myths surround Japanese swords, the most frequent being that the blades are folded an immense number of times, gaining magical properties in the meantime. Note that with each fold made by the maker, every internal layer is also folded, and so the total number of layers in a sword blade is two to the power of the number of folds made. As for magical properties, see above.
It also a myth that Japanese swordmaking techniques were vastly superior to those of the rest of the world. The Bible already mentions a Damast blade (made in Damascus with the distinctive Damast pattern on the steel) that would cut through a silk scarf that was dropped down on the edge. Toledo steel swords from Spain are another example of legendary quality swords from outside Japan.

As for the amount of weapons, Japan has few compared to the rest of Asia, doesn't matter where, most countries have more,