Uniform upsetting forming method for large-height-diameter-ratio magnesium alloy bar

Abstract

The invention discloses a uniform upsetting forming method for a large-height-diameter-ratio magnesium alloy bar. The uniform upsetting forming method includes the steps that firstly, a large-height-diameter-ratio upsetting forming die is designed, wherein the die comprises a male die body and a female die body, the end face of a punch of the male die body is in the shape with the convex middle and the concave periphery and has a wave outline composed of a concave arc, a convex arc and a concave arc in sequence when seen from the axial section, a plane is formed in the middle portion of the bottom of a die cavity of the female die body, a groove is formed in the periphery of the bottom of the die cavity of the female die body, the plane and the groove in the periphery are in smooth transition, and the wave shape with the two concave sides and the plane middle is shown when the bottom of the die cavity of the female die body is seen from the axial section; secondly, a circular shallow groove, namely, an upper groove, is turned in the surface of the upper end of a magnesium alloy cylinder blank, a circular shallow groove, namely, a lower groove, is turned in the surface of the lower end of the magnesium alloy cylinder blank, and a certain number of lubricant is smeared and reserved in each groove; thirdly, the die is preheated, and the magnesium alloy cylinder blank is placed in the die to be subjected to heat preservation and upsetting; and fourthly, upsetting extrusion forming is conducted on the magnesium alloy cylinder blank through the die, and die disassembling is performed. By means of the method, the forming uniformity is improved, the friction force between the die and the magnesium alloy bar is reduced, and performance of forgings is improved.

Description

technical field [0001] The invention relates to the field of plastic forming of metal materials, in particular to a uniform upsetting forming method with a large aspect ratio. Background technique [0002] At present, in the field of metal forming, upsetting is a commonly used forging and pressing forming method. During the upsetting process of large billets, due to the existence of friction between the die and the contact surface, the unevenness of the deformed metal flow is caused, and the deformation zone Uneven deformation of the metal occurs, resulting in different grain sizes and uneven performance of forgings; for bars with large aspect ratios, uneven deformation and instability will occur during upsetting, forming drums or double drums, It will cause great difficulties for the subsequent forming and reduce the utilization rate of materials. Especially for the magnesium alloy bar with large aspect ratio, the plasticity is poor, and cracks are easily generated from th...

AI Technical Summary

Problems solved by technology

[0002] At present, in the field of metal forming, upsetting is a commonly used forging and pressing forming method. During the upsetting process of large billets, due to the existence of friction between the die and the contact surface, the unevenness of the deformed metal flow is caused, and the deformation zone Uneven deformation of the metal occurs, resulting in different grain sizes and uneven performance of forgings; for bars with large aspect ratios, uneven deformation and instability will occur during upsetting, forming drums or double drums, It will cause great difficulties for subsequent forming and reduce the utilization rate of materials

Especially for the magnesium alloy bar with large aspect ratio, the plasticity is poor, and cracks are easily generated from the drum-shaped part, resulting in the scrapping of the billet

Some scholars have proved by simulation that the upsetting effect of the convex and concave dies in the shape of a conical surface is better than that of the convex and concave dies in a flat or concave surface, but the corresponding friction force increases due to the increased contact area between the convex and concave dies with the conical surface

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