Patent GB-443450-A (GB)
Title: The manufacture of metal powders or mixtures of metal powders and metal oxide powders
IPC: B22F9/00
Filed: 1934-11-01
Abstract: Mixtures of metal powders and metal oxide powders are produced by forming an intimate mixture of molten metal and an inert hard granular solid material, the form of which is not changed at the temperature of the molten metal, and cooling the mixture preferably while continuing to mix the same.  The conditions are such that the powder produced contains not less than 20 per cent of unoxidized metal.  The powder may be separated from the dispersing agent by physical or chemical means.  The molten metal may be produced in situ by the reduction of a metal oxide which may itself be produced in situ by oxidizing another compound. Oxidation of the metal may be effected by exposing it for a short time to an oxidizing agent, e.g. a stream of air.  The dispersing agent may be sand or other minerals, glass, porcelain, carbides, metals, or metal compounds, and the granules are preferably between 2 and 3 mm. in diameter.  Lead may be mixed with sand, subjected to the action of an air current for \ba1/4\be to \ba1/2\be hour, and then cooled the stirring being continued throughout, the mixture of lead and lead oxide powder being separated from the sand by air separation.  Alternatively, the sand may be stirred into the molten lead or the molten lead may be allowed to trickle into the heated sand.  Specification 409,534 is referred to.ALSO:Metal powders or mixtures of metal powders and metal oxide powders are produced by forming an intimate mixture of molten metal and an inert hard granular solid material, the form of which is not changed at the temperature of the molten metal, and cooling the mixture preferably while continuing to mix the same. The conditions are such that the powder produced contains not less than 20 per cent of unoxidized metal.  The powder may be separated from the dispersing agent by physical or chemical means.  The molten metal may be produced in situ by the reduction of a metal oxide which may itself be produced in situ by oxidizing another compound.  Oxidation of the metal may be prevented or limited by the introduction of an inert gas, e.g. nitrogen.  To prevent sticking the powder may be allowed to become slightly oxidized, either by mixing some air or oxygen with the inert gas or by exposing the metal for a short time to an oxidizing agent, e.g. a stream of air.  The oxide may, if desired, be subsequently reduced by hydrogen.  The dispersing agent may be sand or other minerals, glass, porcelain, carbides, metals, or metal compounds, and the granules are preferably between 2 and 3 mm. diameter. Lead may be mixed with sand, subjected to the action of an air current for 1/4 to 1/2 hour, and then cooled, the stirring being continued throughout.  The slightly oxidized lead powder obtained is separated from the sand by air separation. Alternatively the sand may be stirred into the lead or the molten lead may be allowed to trickle into the heated sand.  In another example antimony sulphide is mixed with porous stoneware grit and stirred in air at about 700 DEG  C., antimony oxide being formed. Hydrogen is then passed over the mixture of oxide and grit until the oxide is reduced.  The mixture is cooled and the powdered antimony formed is separated from the grit by sieving.  The air and hydrogen may be introduced under pressure and the grit may be impregnated with a catalyst to accelerate the oxidation or the reduction.  The production of powdered zinc by dispersing molten zinc with granulated iron in an inert atmosphere is also described and the treatment of metals such as tin, bismuth, and cadmium is referred to.  Specification 409,534, [Group III], is referred to.