Water-atomized iron powders

Describe the difference between sponge powdered iron and water-atomized powdered iron. 

Water Atomization -100 Standard deviation 1.7-2.4 Fe, Cu, Cu alloys, Stainless steels. Tool steels, Ni alloys, Precious metals 104-106 400 15-60 Steel iron 0.5-5 Stainless steel Cu alloys High volume, Low cost Powder purity shapeXow EE... 

Water atomized iron powder, particle size >150 xm < 400 p,m, low inorganic insulation thickness, (Somatoy 550)... 

Three major quantities are used in P/M the bulk density of the loose iron powder (e.g., 3000 kg.m for water-atomized powder) which is lower than the apparent density due to air space. After compression, the compressed density doubles to about 6000 kg.m Finally, after sintering, the fusion that occurs between particles increases the steel s density to a density approaching the theoretical density or pore-free density. Three types of iron powders are available commercially. 

In the 1960s the A. O. Smith Company in the United States introduced a new method for the development of powdered metal, called water atomization. In this method, the pure metal is melted and a small stream of the liquid is allowed to flow from the bottom of the container of molten metal. A high-pressure blast of cold water hits the stream of metal, breaking it into small droplets that quickly solidify. Powdered metal particles made in this way are more smooth and dense than the sponge powder particles from oxide scrap. In addition to powdered iron metal, many copper, bronze, carbide, and brass parts are made through powder metallurgical processes. 

Sponge powdered iron contains many small holes in the iron particles due to the escaping of the oxygen when the iron is reduced. Water atomized powdered iron has much smoother and denser particles as the powder is formed from molten iron. 

In atomization, a stream of molten metal is stmck with air or water jets. The particles formed are collected, sieved, and aimealed. This is the most common commercial method in use for all powders. Reduction of iron oxides or other compounds in soHd or gaseous media gives sponge iron or hydrogen-reduced mill scale. Decomposition of Hquid or gaseous metal carbonyls (qv) (iron or nickel) yields a fine powder (see Nickel and nickel alloys). Electrolytic deposition from molten salts or solutions either gives powder direcdy, or an adherent mass that has to be mechanically comminuted. 

Powder Formation. Metallic powders can be formed by any number of techniques, including the reduction of corresponding oxides and salts, the thermal dissociation of metal compounds, electrolysis, atomization, gas-phase synthesis or decomposition, or mechanical attrition. The atomization method is the one most commonly used, because it can produce powders from alloys as well as from pure metals. In the atomization process, a molten metal is forced through an orifice and the stream is broken up with a jet of water or gas. The molten metal forms droplets to minimize the surface area, which solidify very rapidly. Currently, iron-nickel-molybdenum alloys, stainless steels, tool steels, nickel alloys, titanium alloys, and aluminum alloys, as well as many pure metals, are manufactured by atomization processes. 

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