Production of Crucible Steel by Co-Fusion: Archaeometallurgical Evidence from the Ninth-Early Tenth Century at the Site
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1 Turkmenistan is the country in the centre or the map, indicated by the cross-hatching. The city of Merv is located by the starin the lower right comer of Turkmenistan.
It has hitherto been commonly thought that the only method of making the famous patterned "Damascus Steel" was by using the so called Wootz process which involves the solid state carburization of iron in a crucible in order to form steel.Some types of Wootz ingots have evidently been made into blades exhibiting a watered pattern characteristic of Damascus steel. 105 Mat. Res. Soc. Symp. Proc. Vol. 462 ©1997 Materials Research Society
It is here proposed, however, that the process that has now been This discovered at Merv is distinct from the Wootz process. variation of steel making in crucibles by the co-fusion of wrought iron and cast iron was described by Islamic authors, especially al-Biruni (c. 973 - 1050) for the production of Damascus steel. The medieval Islamic writer al-Biruni describes the properties of wrought iron, cast iron as well as methods of He travelled throughout the Khurasan producing steel [1,2,3]. and most of his writings appear to be based on first hand He describes three methods for prodacing steel: experience. 1) The carburization of wrought iron by the diffusion This method is associated of carbon into solid wrought iron. with tv~term "wootz" for production of steel in crucibles, usually
in
India;
2) The decarburization of cast iron by removing carbon from the cast iron; The fusion of wrought iron and cast iron to get a 3) steel product of intermediate carbon content [2,3]. Al-Biruni states "this was the method (apparently fusion) used in Harat [sic.] and gave two different qualities of steel. One was the result of melting components equally so that they become united in the mixing operation and no component can be differentiated or seen independently... such steel is suitable for The second quality was obtained if the files or similar tools. degree of melting of the wrought and cast iron was different for each substance and thus the intermixing between both components is not complete, and their parts are shifted so that each of their two colors can be seen by the naked eye and it is called Firind is translated either as "damascus" [3] or firind " [2]. "pattern" [2]. THE CRUCIBLES The archaeometallurgical area at Merv was identified during 2 survey work as a scatter (approximately 10 mi ) of broken crucible fragments, which could be grouped into lids, walls and base All of the crucibles were broken but the dimensions, fragments. shape and features of the crucible are reconstructed in Figure 2. The height is estimated to be between 18 and 20 cm. The lids and upper parts of walls exhibit a gray coloured The raised hole in matrix. The lower walls have a white matrix. the lid would probably have been beneficial to the process because the flow of hot furnaces gasses across the top of this miniature chimney would have produced a slight Venturi effect, assisting the removal of gases from inside the crucible and impeding the
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