Introduction

Magnesium alloy die casting has been widely used in automobile, communication and electronic industries, and with the accelerated pace of social development, the traditional production technology has been gradually unable to meet the magnesium alloy die casting actual production demand.

In the face of rapid changes in the market, in order to further improve the processing quality of magnesium alloy die casting, it is necessary to do further analysis on the basis of the existing, that is, based on the characteristics of the die casting, in order to meet the actual production demand for the purpose of selecting the appropriate production technology.

Magnesium alloy die casting characteristics

Compared with other metal alloys, magnesium alloy has the advantages of high vibration absorption performance, good cutting performance, high dimensional stability and recyclable, etc., the magnesium alloy processing, the production of die casting, using its vibration-absorbing characteristics can be used in automobiles, airplanes and other means of transportation parts, can effectively reduce the noise generated by vibration. And the use of its cutting characteristics, it can be fast cutting processing, do not need to be polished, the energy required for machining is only about 1/5 of steel, and can be effectively recycled.

For its good stability, size is not easy to deformation, good heat dissipation, corrosion resistance and other characteristics, can be applied to electronic equipment through the processing of parts, for example: the structure of the product and heat conduction performance of the comprehensive design and analysis, you can use magnesium alloy heat dissipation performance, the Cpu and other electronic parts generated heat channeling exclusion.

Magnesium alloy die casting production technology

Die casting processing is magnesium alloy casting process in the most widely used one, has the advantages of high efficiency, large batch, automation and so on, the production of castings has a clear contour, high dimensional accuracy, surface fine and so on.

In the magnesium alloy die casting processing production, can use hot chamber die casting machine or cold chamber die casting machine production, in general the hot chamber die casting machine is mainly used for the production and processing of small and medium-sized castings, especially thin-walled, and the appearance of the high requirements of the parts. And cold chamber die casting machine is mostly used for special requirements structure parts processing, such as airplanes, automobiles and other parts, functional requirements are more clear.

Magnesium alloy enthalpy value is low, solidification speed is relatively fast, in the die casting processing of each component, the pressure injection speed requirements are high, to ensure that can be completely full of casting, in general the speed control in aluminum alloy, zinc alloy processing of 1.5 times can be. And in the magnesium alloy die casting processing, to strictly control the processing temperature, equipped with the corresponding protection system to avoid the oxidation of the alloy liquid, can not directly use zinc alloy or aluminum alloy die casting machine for processing.

magnesium alloy die casting design control elements

1.Select die-casting machine

In the choice of die-casting machine, can design casting wall thickness as a reference basis, combined with the actual situation to choose with cold room die-casting machine or hot room die-casting machine for processing. Combined with the magnesium alloy die casting production experience analysis, in general, for less than 1kg of castings should choose to use the hot chamber die casting machine processing, the casting wall thickness control in the design range, the larger castings processing should choose to use the cold chamber die casting machine.

2.Determine the processing parameters

Processing parameters are reasonable directly affect the production efficiency of die casting machine. In magnesium alloy die casting production process, affect the alloy liquid filling molding of many factors, such as injection speed, injection pressure, filling time, die casting mold temperature. In determining the processing parameters, pay attention to because of the influence of die casting wall thickness and complexity and other factors, in a large range of changes in the process parameters in the selection of suitable production and processing parameters.

Compared with zinc alloy, aluminum alloy, magnesium alloy has the characteristics of high mobility, in determining the second level of pressure injection speed can be appropriately increased, generally will be magnesium alloy punch speed control in aluminum alloy die casting speed of 0. 3 times can be. In addition, in order to improve the finished rate of die casting processing, taking into account the pouring temperature and die casting mold temperature on its liquidity, it is necessary to strictly control the pouring and die casting mold temperature, so as to avoid the magnesium alloy solidification to form scrap.

3.Pouring system

In the pouring system design, need to do at the same time on the liquid metal flow direction, mold temperature distribution, exhaust overflow conditions, pressure transfer, filling time and liquid metal through the sprue at the temperature and flow state and other factors of comprehensive analysis, do a good job of coordination between the factors of analysis.

3.1 Filling speed: affected by the thermodynamic characteristics of magnesium alloy, the alloy liquid to the mold heat transfer rate is very fast, and has a large solidification interval, poor mobility, in order to improve the production effect of die casting, should avoid premature pouring of alloy liquid, and to ensure that the alloy liquid through the sprue at the temperature and flow state of the factors of the comprehensive analysis of the factors, do a good job of coordination between the analysis of the factors.

The alloy liquid, and to ensure that the alloy liquid can be filled into the cavity at high speed and smoothly. Generally speaking, the flow rate of the sprue is 90-100m/s can be, in which for thin-walled die casting, the speed of the inner sprue can be controlled at 20m/s left.

3.2 Position of inner pouring channel: generally magnesium alloy die casting are thin-walled parts, and alloy liquid solidification speed is fast, for the determination of the position of the inner pouring channel, we should try our best to avoid the direct impact on the surface of the cavity, so that the alloy liquid can keep the shortest path to flow in the cavity, to avoid the phenomenon of underpouring or cold segregation.

3.3 Filling time: the filling time is closely related to the speed of the inner sprue, especially for thin-walled castings with high surface quality requirements, so the filling time is generally determined to be 30% less than that of the aluminum alloy, and is usually valued at 10-100ms.

3.4 Inner sprue size: magnesium alloy die casting production, the inner sprue width should be controlled in the wall thickness of 50% or less, so as to avoid damage to the casting when trimming treatment. In order to minimize the thickness of the inner casting channel, and to ensure that magnesium alloy die castings to meet the requirements of thin wall, should also try to expand the cross-sectional area of the inner casting channel.

Magnesium alloy die casting surface processing technology

From the actual situation, now generally will use the processing solution to die casting surface processing, according to the film technology can be divided into anodic oxidation film and chemical film two kinds, which chemical film that is the use of chemical solution and die casting surface for a certain period of time contact, die casting surface and chemical solution after chemical reaction in the surface formation of protective film.

Conclusion

To improve the effect of magnesium alloy die casting processing and production, need for its characteristics, analysis of existing technology, do a good job of each production and processing links of the study, and take measures to optimize, improve the implementation of each processing link of the normative and rationality, and strive to continuously improve the effect of magnesium alloy die casting processing.