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It is well established25-28 that the ferrite / perlite bands of the hypoeutectoid steels result from microegregation of element X in the Fe-C-X alloys, where X is usually manganese, phosphorus, or an alloy addition. For the example X = P, it is established that the microegregation of phosphorus to the interdendritic regions (IRS) causes ferrite to be nuclear, preferably in the IRS. If the cooling rate is slow enough, the ferrite grows as allotriomorphs blocky grain limit and pushes the carbon past the growth front until perlite forms between the neighboring RIs. Apparently, lamination or forging deformation is quite effective in the alignment of the IRs of the solidified ingots in flat matrices, because the ferrite appears as flat bands parallel to the plane of deformation separated by bands of pearlite. The ferrite / sword 8 perlite bands were probably produced by this type of bands, probably caused by the microegregation of phosphorus.
A strong body of evidence has been obtained16-18 that supports the theory that the layered structures in the normal hyperkeutectoid Damascus steels are produced by a mechanism similar to the mechanism that causes ferrite / perlite bands in hypoeutectoid steels with an important difference in ferrite / perlite bands, the bands are formed in a single thermal cycle. For example, the ferrite / perlite bands can be destroyed by complete austenitization at low temperatures followed by rapid cooling and then reformed into a single heat until austenite, followed by a cool.26 suitably slow (low temperature austenitization is required for avoid homogenization of the microsegregated X element.) The carbide strips of Damascus wootz steel are destroyed by complete austenitization at low temperatures (above the Acm temperature), followed by cooling at all speeds, slow or fast. However, if the steel is then cycled repeatedly for maximum temperatures of around 50-100 ° C below Acm, the carbide strips begin to develop after a few cycles and become clear after 6-8 cycles.
The mechanism of formation of the carbides selectively grouped along the IR during the cyclic heating of the forging process is not resolved. It seems likely, however, that it is a selective thickening process, that the cementite particles spread over the RIs slowly become larger than their neighbors extending over the dendrite regions and shifting them outward. A model for such a selective thickening process has been presented.17 During the heating stage of each thermal cycle, the smaller cementite particles will dissolve, and only the larger particles will remain at the forging temperature, which is just below the temperature Acm. The model requires the atoms of segregated impurities that lie in the IRs to selectively reduce the mobility of the cementite / austenite interfaces in those regions. The larger particles would then occur in the IRs at the forging temperature. They are likely to maintain their dominant position in cooling because one would not expect the small particles that had dissolved to renucleate to cool in the presence of nearby cementite particles. These almost by the particles that provide sites for the growth of cementite prior to adequate local supercooling enough to nucleate new particles.
EXISTING BLADES quality damask
In the course of our research on the production of reconstructed Damascus Wootz steel sheets, it has become clear that it is much easier to forge blades of small ingots that show little or no damascene pattern than to produce blades with the damascene pattern. . Fe3C particles are still present in these blades, but they are arranged randomly instead of arranged in bands. Such blades are very widespread in the collections and are called blades.4 as they often granulate to produce the strip structure, the correct combination of the cooking time / temperature during ingot manufacture, the right chemical composition (additions of minor elements). importance), and adequate thermomechanical sequencing during the forging process is required. It is relatively easy to make an ingot that will not do it in the pattern of the forge.
Based on this experience, it seems likely that the fraction of crucible steel from India that was successfully forged in the damascene blades was probably very small; Most of the surviving Damascus wootz blades probably display low quality surface patterns. Craddock29 has reached the same conclusion based on an analysis of the literature on damascene steels with drawings. The results on the four Moser blades studied by Zschokke support this same conclusion. These blades were supposedly representative of good quality damascene blades from the east, and yet, of the four, only sword 9 shows the CFe3 bands of high quality characteristic of the best leaves of Damascus Wootz with museum quality.
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