LARGE-DIAMETER ACCURATE TUBE OF ALUMINUM ALLOYS PRODUCING METHOD AND TUBE FORMED BY SUCH METHOD Russian patent published in 2007 - IPC B21C23/08 

FIELD: production of large diameter tubes from high strength aluminum alloys of system such as Al-Zn-Mg and Al-Zn-Mg-Cu satisfying high accuracy demands of wall thickness and diameter and also of tube rectilinearity.

SUBSTANCE: method comprises steps of casting, homogenization, cutting and mechanically working, induction heating of ingots, hot extrusion of tubes, straightening them by tension, quenching and aging. Hot extrusion is realized with use of lock joint of needle and needle holder in order to provide possibility for self centering of needle relative to die. Before guiding ingots to container ingots are turned around lengthwise axis by 180° in order to level temperature field of extruded metal. Ingots are subjected to mechanical working at wall thickness difference in range 0.6 - 1.0 mm and skewing of ends 0.4 - 0.7 mm. Tensile straightening of tubes with very large diameters and cross section surface areas not suitable for straightening in quenched state is realized in hot extruded state at residual deformation degree 1 - 3% and at lowest value of limit yield.

EFFECT: possibility for providing high accuracy of wall thickness, diameter and rectilinearity of tubes.

5 cl, 3 dwg, 3 notes