Pattern Welded Damascus
Modern ‘damascus’ steels are actually pattern welded steels - steels of varying alloy content are be beaten into strips and these strips then forged together, one on top of the other. (A similar process was developed by Japanese swordsmiths) The resulting ingot would then be hammered into a long strip, folded over, hammered, folded over again and so on. This process would eventually produce a sword or knife blank composed of many alternating lamellae. Starting with a tough steel and a hard steel as the initial layers would ultimately produce a sword or knife blade with a hard edge and a tough core – in the hands of a skilled smith anyway! Part of the sharpness of good pattern welded blades might in fact have been responsible to the micro-cracking of the hard steel layers – in effect the blade would be micro-serrated.

In reality, many wootz type Damascus blades were probably quite unremarkable, probably inferior to their Western counterparts, but every now and again a skilled swordsmith would produce an exceptional blade and it was these that gave rise to the legendary status of the type. However, modern laminate and stress analysis theory, together with a greater understanding of alloying and heat treatment, should make it possible manufacture Damascus blades to this exceptional standard by design rather than by accident or trial and error. In parallel with the technical requirements for high performance laminated steels, one must consider that the aesthetic appearance of the steel is determined by the laminate structure of the billet.

Damascus billets are made by cutting and stacking layers of different steels together and welding them into a solid piece. This billet is then drawn and cut into two or more pieces, re-stacked and welded. The number of layers in the final billet will depend on the number of distinct layers in the initial billet and the number of times it is folded and welded. Each fold is a geometric progression 4,8,16,32,64,128,256,512 etc. Howard Clark has done some studies and has determined that after two folds the carbon has been evenly dispersed through out the billet and it is for all intents a homogeneous piece of steel. Optimal for pattern development in straight laminated billets is between 300 to 500 layers. Going the next step to 1,000 layers makes the pattern too fine and staying under 300 it appears wide and bold.

Wootz & damascus steels: what are they and what is the difference ?
By m. meles.


Damascus steel was originally believed to have been manufactured in Damascus, perhaps from steel imported from India ('wootz steel'.) Damascus steel has acquired a legendary reputation for strength and toughness, but is arguably best known for it’s aesthetic appearance – careful etching revealing the dendritic structure of the metal. In many cases the manufacturing technique is optimised to create a striking appearance, possibly at the expense of mechanical properties.

In reality, the average Saracens' swords were almost certainly inferior to the Crusaders' stronger, tougher steel and carburised iron weapons. Western smiths of the era worked their metals at higher temperatures and had a far better understanding of the forging process than their Indian counterparts. However, whenever a Crusader - with God on his side - was defeated, the answer surely must be in the mythical power of the Damascus sword rather than in the superior skill of its wielder... and a few of those wootz swords, mainly by chance, were rather good...

Wootz Damascus
Wootz steel is melted in small sealed clay crucibles from steel scraps and carbon bearing materials and after solidifying, was forged at a very low heat into sword blades. Sword remnants tested for content were often found to contain a significant amount of sulphur and phosphorous. It is believed that this made the cast ingots red short, difficult to forge and is very likely the governing secret to the success of Damascus blades. The higher heats that the European smiths were accustomed to would have crumbled the steel and it also would not have produced the kind of steel that made them famous. Although the task of forging at such a low and narrow band of temperature was difficult, the first side-affect or benefit was tougher and springier steel with superior edge holding properties. The second benefit was the pattern formed by the ghosting of the dendrites which were formed during the slow initial cooling of the ingot. It was discovered recently by Al Pendray and Dr. John Verhoeven that the trace amounts of vanadium were responsible for forming the Damascus patterns because they aligned along the grain boundaries of the dendrites and, due to forging at a reduced heat, retained the image throughout the forging process. Although it was the dendrite pattern that gave rise to the Damascening, it was soon learned how to enhance the patterns mechanically.

In order for the pattern to be readily observed on the surface of the blade, the decarburized and oxidized layer had to be ground off, the blade had to be cleaned and polished before it was etched. Wilkinson records that wood-ashes and water were used in India, or chalk and water to remove any surface grease. Other materials used to clean the steel include dry lime with water and tobacco ash (Sachse, 1994, 83). To etch the blades, Wilkinson (1837,191) discusses the use of dilute nitric and sulphuric acids at Cutch. He also records that a better effect is produced when the blade is immersed in a bath of copper sulphate in water for ten to thirty minutes (Wilkinson, 1937, 190-191). Sachse (1994, 84) refers to the use of ferric sulphate and ferrous sulphate to etch the blades. The etching reacts preferentially to the iron and carbide regions and the effect depends on the type of etchant used and the amount of time it reacts with the metal. According to Verhoeven and Jones (1987, 155) the white component (a.k.a. threads, see Classification of Damascus Patterns) of hypereutectoid Damascus patterned blades is the cementite. On hypoeutectoid blades the ferrite is the white or lighter component. The darker “background” colour is often a form of pearlite which appears darker, or having a pearl–like appearance, hence the name. However, which phases appear lighter or darker also depends on the microstructure and the etchant used.

In summary, the formation of the pattern particularly in hypereutectoid blades is due to the interdependent relationship between the elements contained in the crucible steel ingot and the forging process. The presence of phosphorous in the crucible steel dictated the low forging temperature. In turn, the low temperature forging produced spheroidal cementite. The presence in the ingot of the trace elements such as vanadium, molybdenum, chromium, niobium, or manganese promote the alignment of the spheroidal cementite in the steel, thus producing the Damascus pattern when etched. The relationship between the elemental composition of the ingot and forging method associated with hypoeutectoid blades has not been studied in detail. However, the presence of elements such as manganese promotes the growth of pearlite in the interdendritic region, whereas the dendrite is composed of ferrite. Slow cooling of the ingot will produce bigger bands and these bands can be observed when the blade is etched."


m. meles. 2007

Reproduced with kind permission.