Bi-crucible low pressure casting method for magnesium alloy hub and equipment thereof

Abstract

The invention aims to provide a method for producing a magnesium alloy hub based on bi-crucible low pressure casting equipment, thus improving production efficiency, enabling production process to be convenient and safe and enhancing quality of magnesium alloy automobile hub castings. The aim of the invention can be realized by adopting the bi-crucible low pressure casting equipment which mainly comprises a melting heat preservation furnace (1), a melting heat preservation crucible (2), a communicating tube (3), a casting crucible (4), an one-way valve (5), an intake tube (6), an air bleeder (7), a riser tube (8), a casting crucible (9), a casting mould (10) and a control system (11), wherein metal liquid in the melting heat preservation crucible (2) is controlled by the one-way valve (5), and liquid levels in the two crucibles are maintained to be same by communicating the communicating tube (3) and the casting crucible (4).

Description

technical field [0001] The invention relates to a low-pressure casting method and equipment thereof, in particular to a double-crucible low-pressure casting machine, which is suitable for low-pressure casting of magnesium alloy wheel hubs. Background technique [0002] With the increasingly stringent requirements of governments around the world on energy saving, safety and environmental protection, the automotive industry will encounter higher and higher technical thresholds. As the high-speed moving parts of the vehicle, the weight reduction of the wheel hub can effectively reduce energy consumption, improve the acceleration and braking performance of the vehicle, and improve driving comfort and safety. The use of lightweight materials to realize the replacement of the wheel hub is an effective way to achieve this goal. At present, there are at least 60 kinds of magnesium alloy parts used in automobiles, mainly including instrument panels, seat frames, steering wheels, engi...

AI Technical Summary

Problems solved by technology

Magnesium alloy liquid used for high temperature is easy to oxidize, burn and explode, so the production process of low pressure casting for magnesium alloy hub becomes complicated, including metal addition, magnesium liquid purification treatment, oxidation slag cleaning, etc.

In order to ensure the progress of production, the volume of the crucible should not be too small. Repeated pressurization of a large-volume crucible at high temperature will easily cause the crucible to bulge or even crack. If the crucible cracks and the magnesium liquid leaks into the furnace, a major explosion accident will inevitably occur at this time. Therefore, it is safe to Poor performance is always a nightmare for low-pressure casting of magnesium alloys

As production progresses, the liquid level in the crucible changes constantly, resulting in unstable casting process parameters, and magnesium alloys are very sensitive to process parameters. Therefore, the quality stability of low-pressure cast magnesium alloy products is not good.

The crystallization temperature interval of cast magnesium alloys is generally relatively large, the amount of eutectic in the structure is also small, and the volume shrinkage and linear shrinkage are large; the density of magnesium is small, and the heat capacity is low (volume specific heat and latent heat of solidification are respectively aluminum 75% and 36%), so the pressure head is small, easy to solidify and difficult to fill the mold; the coarse structure, looseness, and porosity are very sensitive to the thickness of the casting, which makes the problem of wall thickness effect very prominent; the hot cracking tendency of the casting is also large, magnesium The casting performance of the alloy is worse than that of aluminum alloy

Therefore, the research on the basic theory of magnesium alloy casting shows that low-pressure casting cannot guarantee to obtain wheel hub products with good performance, especially the above-mentioned casting defects are very unfavorable to the fatigue strength of the hub

Therefore, the traditional low-pressure casting magnesium alloy wheel has low performance and cannot meet the requirements of the method standard

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