Spray footprint effect on the induced distortion by the cooling process in the aluminum extrusion process

An efficient cooling following an aluminum extrusion process can eliminate the extra solution heat treatment operation prior to the age hardening and produce sound extrudates (if properly controlled) without large distortions and residual stresses. Generally, a single nozzle provides a spatially varying water flux distribution and causes a non-uniform cooling rate over the surface, which is called a “cooling pattern” or a “footprint” in this study. In quench boxes, a set of several nozzles are used in order to spray over a hot extrudate (usually initial temperature is above 500 °C). The spray of the adjacent nozzles can overlap and provide an ideally uniform water flux distribution. s study, distortions of a free plate due to cooling by two types of nozzles with different footprints were compared: the elliptic and the uniform patterns of singular nozzles and multiple overlapped nozzles, respectively. The goal was to find the benefits and the disadvantages of the two footprints by comparing the distortions due to cooling. Some lab experiments were done in order to measure the impact force distribution of the sprays and the heat transfer coefficient (HTC). These experimental results were used to simulate the cooling process. y, it was shown that the setting parameters (i.e., ellipse angle, adjacent nozzles center to center distance called “pitch” and ellipse major diameter) of the elliptic footprint had a significant effect on the resulting distortion and should be selected properly. Using a set of nozzles with elliptic footprint overlapping each other can be advantageous because the cooling pattern can be tailored over the section being cooled and the higher cooling rates can be applied.