Aluminum extrusion: temperature
heat sources
when pressing aluminum profiles heat formed as a result of friction, and as a result of plastic deformation. heat generation and transmission starts immediately after the start pressing. Part of the resulting heat remains in the pressed aluminum, part and the matrix is transferred to the container, and a portion goes to raising the temperature of aluminum in that portion of the workpiece, which remains in the container. The sources of heat energy during the direct pressing process are shown in the figure: the work of plastic deformation and friction of aluminum on the container, boundary of the dead zone and the girdle aluminum matrix.
Figure
The outlet temperature of the matrix
Critical temperature compaction Aluminum is the temperature profile at the outlet of the matrix. This temperature influences:
- At first, quality aluminum profile and,
- Secondly, on a matrix life.
As for the quality profile, the temperature profile of the output affects the efficiency of its subsequent heat treatment, dimensional stability and appearance of surface defects. High temperature profile at the output of matrix increases the intensity of wear, and the worn matrix, in turn, It gives improved temperature girdle matrix.
The temperature distribution in the workpiece material and the aluminum profile at the outlet of the matrix depends on several factors, such as, material properties, Conditions of friction material container and matrix, ram speed, the ratio of pressing and type of matrix.
What influences the temperature profile
material properties
The mechanical properties of the aluminum alloy billet significantly affect the amount of heat, which is formed by deformation and friction. In case of deformation, heat dissipated current proportional to the voltage at a given temperature, strain and strain rate. In the case of friction, the temperature rises in proportion to the friction shear stress.
Friction
Distribution aluminum temperature strongly depends on the conditions of container, along the boundary of the dead zone and the girdle matrix.
Extrusion speed
The temperature profile of aluminum increases with increasing speed of the ram. This increase is due, that the rate of deformation is directly proportional to the ram speed, and the amount of heat generated in proportion to the deformation speed. The lower ram speed, the longer the time for heat transfer and dissipation.
The ratio of the pressing
The greater the ratio of pressing, the higher the temperature at the outlet of the matrix due to the severe plastic deformation.
Perimeter belt matrix
The temperature of the aluminum profile at the outlet of the matrix increases with the perimeter of the girdle matrix. This is because, that if the length of the belt from increasing its perimeter increases friction over the belt area of the matrix.
