Pattern welding

From Freepedia

Image:DamascusSteelPocketKnife.jpg Pattern welding is the practice in sword and knife making of forming a blade of several metal pieces of differing composition that are forge-welded together and twisted and manipulated to form a pattern. Blades forged in this manner often display bands of slightly different coloration along their entire length. These bands can be brought out for cosmetic purposes by proper polishing or acid etching. Pattern welded blades are often tougher and more shock resistant than blades made out of single pieces of steel, although the difference is much less significant when compared to certain modern alloys.

Pattern welding was originally developed in Europe; the earliest known use is for decorative elements in Roman blades. The carbon content of the iron and steel produced in the bloomery process was highly variable, and repeated folding and welding was employed to remove excess slag and impurities from the metal and to homogenize it. Two or more batches of fairly uniform steel (each batch with a different composition) were then welded together. The different mechanical properties and response to etching of the different steels resulted in create blades with (possibly) improved use properties and distinctive visual appearence. The technique first appeared in 100-200 AD, and by 500 AD was being used by the Merovingian dynasty. Through their successors, the Carolingian dynasty, the technique became common throughout Europe by circa 700 AD.

However, during the subsequent centuries the technique was slowly lost, and by 1300 AD there are no examples of its use. It was during this same period that Damascus steel was being produced in the Middle East, and similarities in the markings led many to believe it was the same process being used. Swords made by pattern welding are sometimes said to be Damascus swords, though the process of making Damascus steel is an entirely different technique.

Pattern welding again fell from use in Europe during the 18th century, when English metalsmiths discovered the puddling furnace, and then rediscovered the Indian crucible-fired steels (wootz steel) which were far superior to any mechanical methods. By the 19th century pattern welding had largely disappeared, although today it is used in custom knife making.

The technique is more commonly associated with Japan, where it reached a high degree of development in the 14th century. Today the Japanese katana is still considered by many to be the best sword ever produced, and is so famed that the technique of folding metal to form blades is still thought by many to be Japanese in origin.

Examples of pattern welding in weaponry from the pre-colonial Philippines also exist.