Production Technology of Cored Wire Used for Liquid Metal Treatment in Steel Plants: Part Two
By Dr Pradeep K. Maitra
dipalyconsultants@hotmail.com

Abstract:

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
Year/USP-No Title of the patents Sl No
1952/2595292 Method of adding alloys to metals 1
1959/2882571 Method of casting metal 2
1964/3141767 Steel casting process and apparatus 3
1971/3598383 Method & apparatus for- additives in  melt 4
1973/3728109 Manufacturing method -- cutting Pb-steel 5
1973/3729309 Method for --- elements to molten metal 6
1978/4094666 Method for refining molten Iron & Steel 7
1978/4128414 Method of introducing Al-wire  ---method 8
1979/4163827 Method for making wrapped in----metal 9
1981/4297133 Method and means for adding---- metal 10
1982/4364770- Manufacture of a composite – product 11
1984/4481032 Process for adding Ca -- molten Fe- metal 12
1987/4711663 Process for automatic--- related equipment 13
1988/4765599 Apparatus for auto----- related equipment 14
1990/4956009 Ca-alloy steel addition and method there of 15
1994/5376160 Agent for the treatment of metals 16
1999/5988545 Method for storing & dispending CW 17
2000/6053960 Method of --- for treating molten metal 18
2001/6280497 CW for treating----method of manufacture 19
2002/6346135 CW for treating molten metal 20
2004/6770366 CW for introducing additives  into a molten metal bath 21
2005/274773 CW-EP Application European Patent-1812607 22
EP2006/1715065 A CW for injecting into a steel melt  process of treating a steel melt using said wire 23
2007/7226493 Method for grain refining of steel grains refining alloy for steel & method for producing grain refining alloys 24
PAP20060198756 method for adding a large quantity of manganese alloy during the production of steel through cored wires 25
WO/2006/008450 CW composition for increasing Ti content of steel 26
WO/2008/144617 Enhanced alloy recovery in molten steel bath utilizing CW doped with deoxidants 27
WO/2008/031473 CW method & device for the continuous production of CW 28
WO/2008/040915 Method & installation for introducing a CW into a bath of molten metal 29
WO/2008/009414 High dimensional CW containing O­ remover and a process for  making the same 30
WO/2008/152328 Novel additive comprising Pb & Pb-alloy for treating bath of liquid steel 31
PAP2008/0314199 Enhanced alloy recovery in molten steel bath utilizing CW doped deoxidants 32
(WO/2009/154701) Strand Cladding of Calcium Cored Wire 33
PCT/GB2006/079832 A1 Wire for refining molten metal and associated method of manufacture 34
WO/2009/130428 Fluxed CW including molybdenum-tri oxide 35
2010/7682418 CW injection process in steel melts 36
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.

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