Backward extrusion die suitable for blank thick-walled tubular product relatively poor in plasticity and design method

Abstract

The invention discloses a backward extrusion die suitable for a blank thick-walled tubular product relatively poor in plasticity. The backward extrusion die comprises a positioning plate, an upper die, a die core and a lower die. The positioning plate of the upper die is of a cylindrical cavity structure, the die core is mounted in a center hole of the positioning plate of the upper die, and the upper die is mounted at the lower end of the positioning plate of the upper die; the upper die is of a cylindrical cavity structure, and the die core is of a cylindrical structure; the inner diameter of the upper die is greater than the outer diameter of the die core; the upper die and the die core are combined by the positioning plate to form a terrace die; the upper die, the die core and the lower die are mounted coaxially; when the terrace die and the lower die are assembled, the backward extrusion die of the blank is formed. A design method of the die comprises the following steps: S1, determining the outer diameter dimension of the end of the lower end of the die core and the inner diameter dimension of the end of the lower end of the upper die according to the dimension requirement onthe thick-walled tubular product needed to form; S2, determining the diameter and the height of the blank according to an extrusion deformation isovolumetric principle; and S3, determining the outerdiameter of the end of the lower end of the upper die and the inner diameter of the lower die of the die according to the diameter and the height of the blank. The thickness of the wall stretched by the backward extrusion die is great, so that the percent of pass is improved.

Description

technical field [0001] The invention belongs to the field of billet processing, in particular to a back-extrusion die and design method suitable for billet thick-walled pipes with poor plasticity. Background technique [0002] For the reverse extrusion forming of the billet tubular part, the mold usually used is the structure of the mandrel punch and the cylindrical part die. During reverse extrusion deformation, only the part of the pipe wall material close to the mandrel undergoes large tensile deformation. Through the stress-strain relationship inside the material, the deformation of the material near the mandrel drives the material farther away from the mandrel to produce out of shape. For blank materials with poor plasticity (such as AZ80, AZ31 magnesium alloy, etc.), when back-extruding relatively thick thick-walled (wall thickness greater than 20mm) pipes, the stress on the inner wall of the pipe cannot be transferred to the outer wall of the pipe in time, making the...

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Problems solved by technology

[0004] The technical problem to be solved by the present invention is to provide a reverse extrusion die and design method for thick-walled pipes with poor plasticity, so as to solve the difficult problem of forming thick-walled pipes with poor plasticity.

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