The effect of severe plastic deformation by the conforming process of equal channel angular extrusion (ECAE-Conform) followed by cold rolling on the microstructures developed in a Cu-0.1Cr-0.1Zr alloy was investigated. Following the ECAE-Conform of 1 to 8 passes (corresponding strains were 0.8 to 6.4) cold rolling to a total strain of 4 was accompanied by substantial grain refinement and strengthening. An average grain size tended to approach 160 nm with an increase in the rolling reduction. An increase in the ECAE-Conform strain promoted the grain refinement during subsequent cold rolling. The fraction of the ultrafine grains with a size of 160 nm after cold rolling to a strain of 4 increased from 0.12 to 0.52 as the number of ECAE-Conform passes increased from 1 to 8. Correspondingly, the yield strength increased above 550 MPa. The strengthening could be expressed by a Hall–Petch type relationship with a grain size strengthening factor of 0.11 MPa m0.5.
The microstructure and mechanical properties of a Cu-0.25%Mg alloy subjected to either equal channel angular pressing (ECAP) or combined cold working, including ECAP followed by rolling and then drawing at room temperature, were investigated. ECAP led to the formation of strain-induced boundaries and the development of ultrafine equiaxed grains with an average size of about 0.6 μm after 4 passes. The microstructure after the combined cold working included fibrous grains elongated in the rolling/drawing direction with a sharp texture containing <001> and <111> fibers. The transversal grain size after combined cold working to a total strain of 5.7 achieved 0.43 μm. The yield strength and ultimate tensile strength after ECAP to a total strain of 9.6 were 570 and 600 MPa; whereas those after combined cold working to a total strain of 8.7 were 745 and 780 MPa, respectively. The reason of the difference in mechanical properties was discussed.
The prospects for fast replacement of submersible tundish nozzles in a continuous slab casting machine are assessed. It is shown that further improvement is required so as to increase the reliability. The operational forces in the drives of the submersible nozzles are studied experimentally, with different support ing structures in the casting system so as to ensure slipping friction and rolling friction between the supporting surface of the metal housing in the protective refractory component and the clamping elements. When flat sprung elements are replaced by rollers, the total drag on the submersible nozzles during fast replacement may be reduced from 0.6-1.3 to 0.4-1.0. That reduces the load on the hydraulic drive of the tundish casting sys tem by a factor of 1.2-1.3 and also increases its fault free life in long continuous casting runs. The results are used in the design of an improved system for fast replacement of the submersible nozzles.
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