Method for preparing rheo-die-casting large thin-wall part with uniform structure

Abstract

The invention discloses a method for preparing a rheo-die-casting large thin-wall part with a uniform structure. The method comprises the following specific steps that prepared semi-solid slurry with a uniform solid fraction is poured into a pressure chamber of a die-casting machine, and a temperature of the pressure chamber is controlled in a multi-section manner, so that the pressure chamber has a gradient temperature which is gradually reduced from a position close to a punch to a position close to a die cavity, then the solid fraction of the slurry in the pressure chamber is uniformly and gradiently increased from the position close to the punch to the position close to the die cavity, in this way, in a rheo-die-casting mold filling process, the defects that the solid fraction of the far end of casting mold filling is lower and the solid fraction of the near end of mold filling is higher due to the facts that residual liquid in the semi-solid slurry has better liquidity than a primary solid phase and the die-casting die cavity of the large thin-wall part is narrower and has larger mold filling resistance can be overcome, the method well solves the problem of uneven rheo-die-casting structure of the large thin-wall part, has important practical significance for improving the quality and comprehensive performance of the large thin-wall rheo-die-cast, and is particularly suitable for rheo-die-casting preparation of the large thin-wall part with the semi-solid slurry exceeding 20 kg and the casting projection area larger than 3000 cm < 2 >.

Description

technical field [0001] The invention belongs to the technical field of metal semi-solid processing, in particular to a method for preparing rheological die-casting large thin-walled parts with uniform structure. Background technique [0002] Die casting is the most efficient and economical production process for aluminum and magnesium alloy castings. With the rapid development of industries such as 5G and new energy vehicles, the size of castings has increased and the wall thickness has decreased, resulting in a sharp increase in the difficulty of forming. The large thin-walled parts produced by the traditional die-casting process have many casting defects, poor thermal conductivity and mechanical properties, difficult to heat treatment strengthening and welding, and difficult to meet application requirements. Therefore, process upgrades are urgently needed. In the 1970s, Professor M.C.Flemings of the Massachusetts Institute of Technology and others invented metal semi-soli...

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Problems solved by technology

[0005] The purpose of the present invention is to solve the problem of inhomogeneity in the structure of the rheological die-casting large-scale thin-walled die-casting die-casting far-end solid phase rate is far lower than the filling near-end, and to provide a rheological die-casting large-scale thin-walled part with uniform structure The method is to pour the prepared semi-solid slurry with uniform solid phase ratio into the pressure chamber of the die-casting machine, and control the temperature of the pressure chamber through multiple stages, so that the pressure chamber forms a gradient temperature from close to the punch to close to the mold cavity. As a result, the solid phase ratio of the semi-solid slurry in the pressure chamber increases uniformly from near the punch to close to the cavity, so that it can well compensate for the residual liquid in the semi-solid slurry compared with the primary The solid phase has better fluidity and the complex and narrow cavity of large thin-walled parts has a large filling resistance, which causes the solid-liquid separation of semi-solid slurry and the significant reduction of the solid phase rate at the far end of the filling mold.

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