Go lean with fluidized beds in aluminum heat treating.
While heat treatment often is necessary for aluminum castings, the process itself can violate lean manufacturing Lean manufacturing is the production of goods using less of everything compared to mass production: less human effort, less manufacturing space, less investment in tools, and less engineering time to develop a new product. principles. The low heat transfer rate in convection furnaces leads to a lengthy holding time to ensure the adequate quality of heat treated parts. The transition of liquid metal to the solid phase takes minutes, but heat treatment takes hours, making it difficult to create a one-piece process flow within a manufacturing facility.
Arizotah Enterprises, Plymouth, Minn., offers a heat treating solution using fluidized bed A fluidized bed is formed when a quantity of a solid particulate substance (usually present in a holding vessel) is forced to behave as a fluid; usually by the forced introduction of pressurised gas through the particulate medium. technology for aluminum castings that can reduce that time dramatically. A fluidized bed consists of a fine, hard media, such as sand, that is partially suspended by a gas. As the gas passes through the media, the particles become able to slide easily past one another, acting like a fluid, and thus allow continuous contact between solid particles and the parts being heat treated. This leads to a high rate of energy transfer and temperature control, allowing the solution heat treated castings to function at temperatures close to the solidus temperature and reducing the net solution heat treating time.
Fig. 1 shows the microstructure mi·cro·struc·ture
The structure of an organism or object as revealed through microscopic examination.
a structure on a microscopic scale, such as that of a metal or a cell evolution of as-cast material undergoing heat treatment through a convection furnace furnace, enclosed space for the burning of fuel. There are many kinds of furnaces, the type depending upon the fuel and the use to which the heat produced within it is put. Most familiar are the furnaces used in the heating of buildings. and heat treatment through the fluidized bed. The silicon particles of the microstructure evolved quicker in the fluidized bed, increasing the ductility ductility, ability of a metal to plastically deform without breaking or fracturing, with the cohesion between the molecules remaining sufficient to hold them together (see adhesion and cohesion). Ductility is important in wire drawing and sheet stamping. of the alloy and shortening the time needed for solution heat treating.
A typical fluidized bed system consists of a solution bed, water quench quench,
v to cool a hot object rapidly by plunging it into water or oil.
to put out, extinguish, or suppress; to cool (as hot metal) by immersing in water. tank and aging bed. A walking beam See Beam, 10.
See also: Walking conveys the parts through the bed, and a sentry robot inserts and removes castings from the beds. The fluidized bed approach allows the metalcaster to adhere more closely to a work-in-progress flow, de-clog congestion The condition of a network when there is not enough bandwidth to support the current traffic load.
congestion - When the offered load of a data communication path exceeds the capacity. in the heat treating department, reduce material handling and avoid moving castings from production to temporary storage and back into the production line.
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By using the one-layer racking method, rather than several layers in a batch as typical with convection furnaces, all parts experience parallel heating and cooling rates. Because every individual casting is exposed to heat at the same rate, the shadowing effects commonly encountered with convection furnaces are not seen. This leads to high quality parts with little or no reworking or scrapping.
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