GB827619A - Improvements in or relating to the treatment of molten metals - Google Patents

Abstract

A shaped solid, product for addition to molten metal to generate gas therein comprises a compacted intimate mixture of a solid particulate substance which, at the temperature of the molten metal, generates or is converted into a gas, and a solid particulate carrier material containing a compound that sinters on heating and remains as a coherent product after generation of the gas. The carrier material may be a mixture of refractory material of good heat-insulating properties and a sintering salt or it may contain two materials of different melting point, one of which has a lower melting point than the metal being treated and will react with the other to form a compound having a melting point above that of the molten metal, e.g. sodium or potassium borofluoride or a mixture thereof with sodium fluoride or borax with calcium fluoride. Alternatively the carrier material may contain a salt such as sodium silicofluoride which decomposes to give off a gas and to leave a high melting point residue. Materials to modify the grain of the metal, e.g. potassium borofluoride may also be included. The gas generating substance may be hexachlorethane. The product, in the form of a flat cylindrical tablet having a central aperture may be applied to the molten metal by threading the tablet on the end of a rod and plunging the rod into the molten metal or by locating the product within a cylindrical open coil at the end of a rod and plunging the rod into the molten metal. The product may be used to remove occluded or dissolved gases from molten metal, to remove metals from molten metal mixtures e.g. to remove magnesium from aluminium by means of chlorine or aluminium from copper alloys such as brass or bronze by means of oxygen or to add gases such as hydrogen to metals. The third Provisional Specification describes also the use of a solid body comprising a conditioning agent the body having a specific gravity greater than that of the metal being treated and being in the form of a compressed mixture of the agent and refractory or a refractory block impregnated or coated with the agent. The refractory block may have a weight e.g. of lead at its centre. The second Provisional Specification describes also the use of a porous container containing conditioning agent, the container having a detachable screw plug or being in two halves which can be screwed together. The container, which may be of perforated graphite, may include a block of heavy metal such as lead to make it self sinking. Alternatively the body may be so composed and be subjected to such a degree of compression that, on evolving gas, it becomes lighter than the molten metal and floats to the surface. A reactive metal such as sodium may be placed in a sealed container which will melt at the temperature of the metal to be treated, the container being placed in a porous refractory housing. The sodium may be associated with other conditioning agents. The first Provisional Specification describes also the use of a conditioning agent mixed with a materials which is destroyed or merges in or alloys with the molten metal treated. For example the said material, in the treatment of molten aluminium, may be aluminium or an alloy thereof with manganese or copper. Specifications 624,479 and 794,604 are referred to.