Device and method for extrusion forming of section-variable hollow member

The invention provides a device and a method for extrusion forming of a terrace surface-variable hollow member, and relates to a device and a method for extrusion forming of a hollow member. After the device and the method are used, the problem that the current terrace surface-variable hollow member is complex in manufacture flow process, multiple in required intermediate treatment working procedures, high in cost, and difficult in quality performance control can be solved. According to a first scheme, a mandrel and a set of stage dies are sequentially installed within an extrusion barrel from bottom to top, and a set of the stage dies and the mandrel are coaxially arranged. According to a second scheme, a set of stage dies and a mandrel are installed within an extrusion barrel from bottom to top; and the pressure is applied onto a punch head to enable the punch head to downwards move, and a ring-shaped blank is extruded from a die orifice of the last stage die to prepare shaped material. According to a third scheme, a piercer is integrated by connecting a first section, a second section and a third section. According to a fourth scheme, a set of stage dies and a mandrel are installed within an extrusion barrel from bottom to top, and are placed on a base; and the pressure is applied onto a punch head to enable the punch head to downwards move, and a ring-shaped blank is extruded from a the die orifice of the last stage die to prepare shaped material. The device and the method are used for forming the hollow member.