Compositions and methods of production of alloy for treatment of liquid metals

#The present invention related to compositions and methods for production of an alloy for treatment of liquid metals and to the composition of an alloy additive for the treatment of liquid steel and other liquid metals and particularly to a silicon free calcium-aluminum-iron-manganese base alloy composition and methods of producing the same for the desulfurization of molten steel baths.

#The injection of various materials into molten iron, steels and other liquid metals using a substantially non-reactive carrier gas has been practiced for many years and for a variety of purposes. Most recently the injection of materials into steel ladles has assumed large scale importance in the steel industry, particularly for the purpose of desulfurization of the molten steel in the ladle, and of control of the shape of the remaining sulfide and oxide inclusions in the wrought steel.

#In general these prior art desulfurization practices have used calcium silicon alloys with about 65% silicon, calcium carbide with about 37.5% carbon, magnesium, magnesium aluminum alloys or mixtures of various lime based powder compositions. Each of these materials presents serious drawbacks in its use as a desulfurizing agent for injection. The lime base powder compositions which are available introduce excessive and undesirable amounts of hydrogen, cause substantial temperature losses in the molten metal and generally require excessive injection times. Magnesium and magnesium alloys, even when diluted at ratios of 5 to 1 with fluorspar or lime are extremely volatile at the temperatures of molten iron and steel. They either produce unacceptable splashing of metal and slag during injection or, if highly diluted, present the same problems as those of the lime-based powders discussed above. Calcium carbide, although very effective and economically attractive for steel desulfurization, is, as a practical matter, not usable in most circumstances because of the unacceptable carbon-pick up by the steel bath during injection. Finally, calcium-silicon, which has become by far the most popular in the steel industry for ladle injection, has serious shortcomings due to its high silicon content. Specifically, with the fast growing demand for extra low-sulfur, low-carbon, high manganese steels, a very strong economic incentive exists for using standard silico-manganese ferroalloy to provide a low cost source of low-carbon manganese units. However, the need to inject anywhere from three to ten pounds of calcium-silicon per ton of steel to desulfurize using the injection technique, introduces in many cases the entire silicon content allowed by the chemical specification for the particular grade of steel being poured. This directly conflicts with the use of low-carbon silico-manganese as the source of manganese values for the steel and forces the melter to turn to very high cost electrolytic or "massive" manganese. Thus, in the field of High Strength Low Alloy (HSLA) grades of steel for critical line pipe and plate applications, the use of calcium-silicon injection is undesirable.

#I have invented a new alloy composition for liquid steel injection which is essentially free of silicon and carbon and consists essentially of calcium and aluminum with optional amounts of iron and manganese and minor amounts, up to 10%, of magnesium, barium and the alkali metals. Calcium and aluminum and at least one of the two elements iron and manganese, are essential to the alloy. Iron and/or manganese are/is added for alloying purposes, for reducing the volatility of the alloy, to improve its crushability or to make the alloy self decrepitating. Preferably I add sufficient iron and/or manganese to make the alloy readily crushable or to make it self decrepitating. The other elements are optional and may be added for some desired purpose or purposes. Broadly the alloy of my invention comprises:

#Calcium--20% to 80%

#Aluminum--5% to 50%