Pattern welding
Encyclopedia
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. Often called Damascus steel
, blades forge
d in this manner often display bands of slightly different patterning along their entire length. These bands can be highlighted for cosmetic purposes by proper polishing or acid
etching. Pattern welding was an outgrowth of laminated or piled steel
, a similar technique used to combine steels of different carbon
contents, providing a desired mix of hardness and toughness. Although modern steelmaking
processes negate the need to blend different steels, pattern welded steel is still used by custom knifemakers for the cosmetic effects it produces.
Pattern welding developed out of the necessarily complex process of making blades that were both hard and tough from the erratic and unsuitable output from early iron smelting in bloomeries
. The bloomery does not generate temperatures high enough to melt iron and steel, but instead reduces
the iron oxide
ore
into particles of pure iron
, which then weld into a mass of sponge iron, consisting of lumps of impurities in a matrix of relatively pure iron, which is too soft to make a good blade. Carburizing thin iron bars or plates forms a layer of harder, high carbon steel on the surface, and early bladesmiths would forge these bars or plates together to form relatively homogeneous bars of steel. This laminating different types of steels together produces patterns that can be seen in the surface of the finished blade, and this forms the basis for pattern welding.
During the Middle ages
, Damascus steel
was being produced in the Middle East
and brought back to Europe. The similarities in the markings led many to believe it was the same process being used, and pattern welding was revived by European smiths who were attempting to duplicate the Damascene steel. While the methods used by Damascene smiths to produce their blades was lost, recent efforts by metallurgists and bladesmiths (such as Verhoeven and Pendray) to reproduce steel with identical characteristics have yielded a process that does not involve pattern welding.
A similar technique was also employed by Scandinavia
n Medieval sword
smiths. The Mora knife
is today manufactured with a similar technique. Today the traditional crucible steel
is seldom used, but the high carbon steel is usually tool steel
or stainless steel
.
s in particular were fond of twisting bars of steel around each other, welding the bars together by hammering and then repeating the process with the resulting bars, to create complex patterns in the final steel bar. Two bars twisted in opposite directions created the common chevron
pattern. Often, the center of the blade was a core of soft steel, and the edges were solid high carbon steel, similar to the laminates of the Japanese.
The American Bladesmith Society
's Master Smith test, for example, requires a 300 layer blade to be forged. Large numbers of layers are generally produced by folding, where a small number of layers are welded together, then the blank is cut in half, stacked, and welded again, with each operation doubling the number of layers. Starting with just two layers, eight folding operations will yield 256 layers in the blank. A blade ground from such a blank will show a grain much like an object cut from a block of wood, with similar random variations in pattern. Some manufactured objects can be re-purposed into pattern welded blanks. "Cable Damascus", forged from high carbon multi-strand cable, is a popular item for bladesmiths to produce, producing a finely grained, twisted pattern, while chainsaw
chains produce a pattern of randomly positioned blobs of color.
Some modern bladesmiths have taken pattern welding to new heights, with elaborate applications of traditional pattern welding techniques, as well as with new technology. A layered billet of steel rods with the blade blank cut perpendicular to the layers can also produce some spectacular patterns, including mosaic
s or even writing. Powder metallurgy
allows alloys that would not normally be compatible to be combined into solid bars. Different treatments of the steel after it is ground and polished, such as bluing
, etching, or various other chemical surface treatments that react differently to the different metals used can create bright, high-contrast finishes on the steel. Some master smiths go as far as to use techniques such as electrical discharge machining
to cut interlocking patterns out of different steels, fit them together, then weld the resulting assembly into a solid block of steel.
Sword
A sword is a bladed weapon used primarily for cutting or thrusting. The precise definition of the term varies with the historical epoch or the geographical region under consideration...
and knife
Knife
A knife is a cutting tool with an exposed cutting edge or blade, hand-held or otherwise, with or without a handle. Knives were used at least two-and-a-half million years ago, as evidenced by the Oldowan tools...
making of forming a blade of several metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
pieces of differing composition that are forge-welded
Forge welding
Forge welding is a solid-state welding process that joins two pieces of metal by heating them to a high temperature and then hammering them together. The process is one of the simplest methods of joining metals and has been used since ancient times. Forge welding is versatile, being able to join a...
together and twisted and manipulated to form a pattern. Often called Damascus steel
Damascus steel
Damascus steel was a term used by several Western cultures from the Medieval period onward to describe a type of steel used in swordmaking from about 300 BCE to 1700 CE. These swords are characterized by distinctive patterns of banding and mottling reminiscent of flowing water...
, blades forge
Forge
A forge is a hearth used for forging. The term "forge" can also refer to the workplace of a smith or a blacksmith, although the term smithy is then more commonly used.The basic smithy contains a forge, also known as a hearth, for heating metals...
d in this manner often display bands of slightly different patterning along their entire length. These bands can be highlighted for cosmetic purposes by proper polishing or acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
etching. Pattern welding was an outgrowth of laminated or piled steel
Laminated steel blade
A laminated steel blade or piled steel is a knife, sword, or other tool blade made out of layers of differing types of steel, rather than a single homogeneous alloy. The earliest steel blades were laminated out of necessity, due to the early bloomery method of smelting iron, which made production...
, a similar technique used to combine steels of different carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
contents, providing a desired mix of hardness and toughness. Although modern steelmaking
Steelmaking
Steelmaking is the second step in producing steel from iron ore. In this stage, impurities such as sulfur, phosphorus, and excess carbon are removed from the raw iron, and alloying elements such as manganese, nickel, chromium and vanadium are added to produce the exact steel required.-Older...
processes negate the need to blend different steels, pattern welded steel is still used by custom knifemakers for the cosmetic effects it produces.
History
Bloomery
A bloomery is a type of furnace once widely used for smelting iron from its oxides. The bloomery was the earliest form of smelter capable of smelting iron. A bloomery's product is a porous mass of iron and slag called a bloom. This mix of slag and iron in the bloom is termed sponge iron, which...
. The bloomery does not generate temperatures high enough to melt iron and steel, but instead reduces
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....
the iron oxide
Iron oxide
Iron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxides and oxyhydroxides.Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, and are widely utilized by humans, e.g.,...
ore
Ore
An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....
into particles of pure iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
, which then weld into a mass of sponge iron, consisting of lumps of impurities in a matrix of relatively pure iron, which is too soft to make a good blade. Carburizing thin iron bars or plates forms a layer of harder, high carbon steel on the surface, and early bladesmiths would forge these bars or plates together to form relatively homogeneous bars of steel. This laminating different types of steels together produces patterns that can be seen in the surface of the finished blade, and this forms the basis for pattern welding.
Pattern welding in Europe
By the 2nd and 3rd century AD, the Celts were commonly using pattern welding for decoration in addition to structural reasons. Alternating layers of steel would be forged into rods, which would then be twisted to form complex patterns when forged into a blade. By the 6th and 7th centuries, pattern welding had reached a level where thin layers of patterned steel were being overlayed onto a soft iron core, indicating that the pattern welding was primarily decorative rather than functional. By the end of the Viking era, pattern welding fell out of use in EuropeDuring the Middle ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...
, Damascus steel
Damascus steel
Damascus steel was a term used by several Western cultures from the Medieval period onward to describe a type of steel used in swordmaking from about 300 BCE to 1700 CE. These swords are characterized by distinctive patterns of banding and mottling reminiscent of flowing water...
was being produced in the Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...
and brought back to Europe. The similarities in the markings led many to believe it was the same process being used, and pattern welding was revived by European smiths who were attempting to duplicate the Damascene steel. While the methods used by Damascene smiths to produce their blades was lost, recent efforts by metallurgists and bladesmiths (such as Verhoeven and Pendray) to reproduce steel with identical characteristics have yielded a process that does not involve pattern welding.
A similar technique was also employed by Scandinavia
Scandinavia
Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...
n Medieval sword
Sword
A sword is a bladed weapon used primarily for cutting or thrusting. The precise definition of the term varies with the historical epoch or the geographical region under consideration...
smiths. The Mora knife
Mora knife
Mora knife is a term used to refer to a range of popular belt-knives manufactured by the cutleries of the town of Mora in Dalarna, Sweden, primarily by Mora of Sweden...
is today manufactured with a similar technique. Today the traditional crucible steel
Crucible steel
Crucible steel describes a number of different techniques for making steel in a crucible. Its manufacture is essentially a refining process which is dependent on preexisting furnace products...
is seldom used, but the high carbon steel is usually tool steel
Tool steel
Tool steel refers to a variety of carbon and alloy steels that are particularly well-suited to be made into tools. Their suitability comes from their distinctive hardness, resistance to abrasion, their ability to hold a cutting edge, and/or their resistance to deformation at elevated temperatures...
or stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....
.
Modern decorative use
The ancient swordmakers exploited the aesthetic qualities of pattern welded steel. The VikingViking
The term Viking is customarily used to refer to the Norse explorers, warriors, merchants, and pirates who raided, traded, explored and settled in wide areas of Europe, Asia and the North Atlantic islands from the late 8th to the mid-11th century.These Norsemen used their famed longships to...
s in particular were fond of twisting bars of steel around each other, welding the bars together by hammering and then repeating the process with the resulting bars, to create complex patterns in the final steel bar. Two bars twisted in opposite directions created the common chevron
Chevron (insigne)
A chevron is an inverted V-shaped pattern. The word is usually used in reference to a kind of fret in architecture, or to a badge or insignia used in military or police uniforms to indicate rank or length of service, or in heraldry and the designs of flags .-Ancient history:The chevron occurs in...
pattern. Often, the center of the blade was a core of soft steel, and the edges were solid high carbon steel, similar to the laminates of the Japanese.
The American Bladesmith Society
American Bladesmith Society
The American Bladesmith Society or ABS is an non-profit organization composed of knifemakers whose primary function is to promote the techniques of forging steel blades. The ABS was founded by Knifemaker William F...
's Master Smith test, for example, requires a 300 layer blade to be forged. Large numbers of layers are generally produced by folding, where a small number of layers are welded together, then the blank is cut in half, stacked, and welded again, with each operation doubling the number of layers. Starting with just two layers, eight folding operations will yield 256 layers in the blank. A blade ground from such a blank will show a grain much like an object cut from a block of wood, with similar random variations in pattern. Some manufactured objects can be re-purposed into pattern welded blanks. "Cable Damascus", forged from high carbon multi-strand cable, is a popular item for bladesmiths to produce, producing a finely grained, twisted pattern, while chainsaw
Chainsaw
A chainsaw is a portable mechanical saw, powered by electricity, compressed air, hydraulic power, or most commonly a two-stroke engine...
chains produce a pattern of randomly positioned blobs of color.
Some modern bladesmiths have taken pattern welding to new heights, with elaborate applications of traditional pattern welding techniques, as well as with new technology. A layered billet of steel rods with the blade blank cut perpendicular to the layers can also produce some spectacular patterns, including mosaic
Mosaic
Mosaic is the art of creating images with an assemblage of small pieces of colored glass, stone, or other materials. It may be a technique of decorative art, an aspect of interior decoration, or of cultural and spiritual significance as in a cathedral...
s or even writing. Powder metallurgy
Powder metallurgy
Powder metallurgy is the process of blending fine powdered materials, pressing them into a desired shape , and then heating the compressed material in a controlled atmosphere to bond the material . The powder metallurgy process generally consists of four basic steps: powder manufacture, powder...
allows alloys that would not normally be compatible to be combined into solid bars. Different treatments of the steel after it is ground and polished, such as bluing
Bluing (steel)
Bluing is a passivation process in which steel is partially protected against rust, and is named after the blue-black appearance of the resulting protective finish. True gun bluing is an electrochemical conversion coating resulting from an oxidizing chemical reaction with iron on the surface...
, etching, or various other chemical surface treatments that react differently to the different metals used can create bright, high-contrast finishes on the steel. Some master smiths go as far as to use techniques such as electrical discharge machining
Electrical discharge machining
Electric discharge machining , sometimes colloquially also referred to as spark machining, spark eroding, burning, die sinking or wire erosion, is a manufacturing process whereby a desired shape is obtained using electrical discharges...
to cut interlocking patterns out of different steels, fit them together, then weld the resulting assembly into a solid block of steel.
See also
- Wootz steelWootz steelWootz steel is a steel characterized by a pattern of bands or sheets of micro carbides within a tempered martensite or pearlite matrix. It was developed in India around 300 BCE...
, an IndiaIndiaIndia , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
n crucible steelCrucible steelCrucible steel describes a number of different techniques for making steel in a crucible. Its manufacture is essentially a refining process which is dependent on preexisting furnace products... - Bulat steelBulat steelBulat is a type of steel alloy known in Russia from medieval times and regularly mentioned in Russian legends as material of choice for cold steel. The name булат is a Russian transliteration of the Persian word پولاد , meaning steel...
, a RussiaRussiaRussia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
n crucible steel - Japanese sword construction, an intricate method of pattern welding.
- Mokume-ganeMokume-ganeis a mixed-metal laminate with distinctive layered patterns. Translating as burl metal, the name was borrowed from one type of pattern created in the forging of swords and other edged weapons.- History :...
, a similar technique, often involving precious metals, used to produce decorative pieces
External links
- Bladesmith Kevin Cashen's page on pattern welding
- Ancient carburisation of iron to steel: a comment
- Mediæval Sword Virtual Museum, which contains close-up images of Viking swords, showing the pattern welding structures.