Forming process of cross-connected finned micro-grooves in copper strips

Abstract

Using ploughing-extrusion method, a cross-connected finned micro-grooves structure was formed on the surface of copper strips with thickness of 0.4 mm. The structure was fabricated by making ‘V’-grooves in copper strips and perpendicular ‘V’-grooves on the opposite side that intersect the first set of grooves. Micro pores appear at the intersection of these cross-connected grooves, and micro fins appear on the groove fringes. So it can be defined as ‘pore-groove-fin’ structure. The preferable ‘pore-groove-fin’ structure can be obtained under the condition that the tool edge inclination angle (χ γ) is 45°, both the major extrusion angle (γ o) and the minor extrusion angle (γ′ o) are 30′, both the major formation angle (β) and the minor formation angle (β′) are 10°, the ploughing-extrusion depth ( f d ) is 0.32 mm and the groove pitch is 0.4 mm on surfaces A and B. The formed included angle of groove A is 70°, and the groove depth is 0.3 mm, while the included angle of opposite perpendicular groove B is 20° with the groove depth of 0.35 mm. The obtained fin height is 0.15 mm, the elliptical pore length is 0.2 mm and the width is 0.05 mm. Experiments show that f d has the greatest influence on the formation of micro pores. Bulges appear on the opposite surface B when the ploughing-extrusion depth on surface A ( f dA ) reaches a critical value. The ploughing-extrusion depth on surface B ( f dB ) has great influence on the re-growth of fin structure.