Importance

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Abstract

This invention is a process for making micro-multiport tubing for use in automobile air conditioner heat exchangers. The tubing is a flat body with a row of side-by-side passageways, which are separated by upright webs. Processing of this tubing involves extrusion, a straightening and cutting operation, assembly and furnace brazing of the condenser. This invention improves the grain size of the metal in the tubing and also improves the metallurgical strength of the tubing. Ports are formed in the tubing during extrusion. These ports are separated by webs and the webs are extruded so that they have a reduced thickness at their centers. In response to successive cold working of the body, the webs are changed in shape to a more uniform thickness state. Stated other wise, in this invention, the webs are initially of hour glass shape such that when there is five percent change in material thickness, the strain is concentrated at the center of the web and results in at least fifteen percent cold work. With fifteen percent cold work or more, the amount of grain growth is controlled and the improvement in the metallurgical strength is achieved.

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First Claim