Figure 8. A special stamp for the
process of co-extrusion
Figure 9. Hydraulic press PD-476
force 1.6 MH with a special stamp
Drawing of the bimetallic element in the form of a cup was carried out in two
stages. At the first stage, a two-layer blank was drawed without thinning in two
transitions. At the first transition, the inner layer was drawed, and at the second
transition – the outer layer was drawed with a punch with an elongated blank of the
inner layer. The gap of the stamp provided for drawing without thinning. The resulting
two-layer cup had physical contact of layers of different metals on the limiting surface.
The contact surfaces of the inner and outer layers were previously cleaned of oxide,
lubricant and other defective layers by chemical and mechanical means before drawing.
For further measurements of non-uniformity of deformation of the layers by drawing
with thinning leveled corciova the surface of the wall of the cup by mechanical means.
In the second stage, the pre-profiled cup was put on the punch and heated by the
inductor with high frequency currents to the deformation temperature. Temperature
control was carried out by thermocouples at three points at different heights of the cup.
Temperature range of heating were elected on the basis of the maximum temperature
deformation of the layer of material with lower temperature processing. As a lubricant
during the process, a mixture based on silicate glue and graphite, as well as a lubricant
for hot stamping of graphite B2 (GOST 3333-80) was used.
For fig. 10 experimental samples of two-layer blanks after the drawing without
thinning and with thinning of the wall with compression of 50%.
In the course of the experiment, the drawing force with the thinning of dissimilar
metals in the heated state was determined. Comparison of experimental results and
numerical calculations for the titanium + aluminum system with =0,3 it was shown
that the maximum calculation error does not exceed 7...10%. This is due to the
statistical dispersion of the mechanical properties of the metal layers.
The estimation of the calculated results was performed according to the
deformation characteristics: ahead of the layer with a lower yield strength and
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