Before the advent of CW, the traditional method of LMT was in practice, which was not only uneconomical but also suffering from several inadequacies like high rate of additive consumption with high dissolution time and also low additive yield & reproducibility.
Because of high surface area of powder it makes intimate contact with LM and improves the performance of the additive. This simple but innovative concept was the genesis of LMT with CW.
Genesis of CW
Before the advent of CW, the traditional method of LMT was in practice, which was not only uneconomical but also suffering from several inadequacies like high rate of additive consumption with high dissolution time and also low additive yield & reproducibility. These problems were encountered because of poor additive penetration deep in melt due to their low density, thermal instability, and entrapment in slag.
Besides this, the toxic metals like S, Te, Se, and Pb etc. when charged in ladle, used to generate toxic vapors. Subsequently penetration of additives briquettes in LM became more difficult due to an increase in ladle capacities in steel mills and to meet the above challenges, efforts were made by investigators in search of a viable alternative methods, till such time when it was conceived that; “If an additive powder encapsulated in a steel tube is quickly injected into the ladle, the momentary survival of steel tube in LM can help additive to reach deep inside the metal pool safely” and after release the additives start moving from bottom towards the top of ladle.
Because of high surface area of powder it makes intimate contact with LM and improves the performance of the additive. This simple but innovative concept was the genesis of LMT with CW. To materialize the above concept of additive charging, CW-mill, CW-additives and CW-injection machines were developed. Some patents relevant to these developments along with their titles are chronologically given in Table 2, as reference.
Table 2: List of patents
||Title of the patents
||Method of adding alloys to metals
||Method of casting metal
||Steel casting process and apparatus
||Method & apparatus for- additives in melt
||Manufacturing method -- cutting Pb-steel
||Method for --- elements to molten metal
||Method for refining molten Iron & Steel
||Method of introducing Al-wire ---method
||Method for making wrapped in----metal
||Method and means for adding---- metal
||Manufacture of a composite – product
||Process for adding Ca -- molten Fe- metal
||Process for automatic--- related equipment
||Apparatus for auto----- related equipment
||Ca-alloy steel addition and method there of
||Agent for the treatment of metals
||Method for storing & dispending CW
||Method of --- for treating molten metal
||CW for treating----method of manufacture
||CW for treating molten metal
||CW for introducing additives into a molten metal bath
||CW-EP Application European Patent-1812607
||A CW for injecting into a steel melt process of treating a steel melt using said wire
||Method for grain refining of steel grains refining alloy for steel & method for producing grain refining alloys
||method for adding a large quantity of manganese alloy during the production of steel through cored wires
||CW composition for increasing Ti content of steel
||Enhanced alloy recovery in molten steel bath utilizing CW doped with deoxidants
||CW method & device for the continuous production of CW
||Method & installation for introducing a CW into a bath of molten metal
||High dimensional CW containing O remover and a process for making the same
||Novel additive comprising Pb & Pb-alloy for treating bath of liquid steel
||Enhanced alloy recovery in molten steel bath utilizing CW doped deoxidants
||Strand Cladding of Calcium Cored Wire
||Wire for refining molten metal and associated method of manufacture
||Fluxed CW including molybdenum-tri oxide
||CW injection process in steel melts
|PAN- Patent application number & WO- for World Intellectual Property Organization
From the list of patent it may be seen that:
1) Initially inventions were made to improve the techniques of LMT.
2) There after, the focus was aimed on the creation of a technique, by which the additive could be penetrated deep inside the metal pool.
3) Subsequently it was realized that the coil penetration should be controllable enough for precise release of additives in liquid metal, irrespective of the ladle capacity & depth. Furthermore, it was also noticed that the voids between additive particles carry air (oxygen) and cause local oxidation. To counter the above deficiencies the metallurgy of the steel jacket, chemistry of additives & CW injection machines were improved. The solid core and doped additives were introduced, to counter the effect of entrapped air.
4) In the quest for enhancing the survival of the CW jacket for little more time under high temperature, thermal insulation on the outer surface of the coil and co-centric tubes were developed. Similarly to achieve better CW performances, variations in coil diameters, sheath thickness & seam lock formations were tried but these developments gradually raised the inventory of CW.
5) To reduce the inventories and to improve the performances, stranded and higher diameter CW, multifunctional additives, and high speed multiple wire feeding machines were developed.