Research progress of extrusion casting technology for metal materials

Abstract:With the continuous development of China's metal materials casting, the study of its squeeze casting forming technology highlights the importance of significance. This paper first introduces the principle and characteristics of squeeze casting molding, analyzes the main methods of squeeze casting molding, discusses several major squeeze casting molding technology, and metal materials squeeze casting molding technology puts forward a few thoughts.

Keywords:metal materials; squeeze casting; forming technology; research

1, squeeze casting technology overview

Squeeze casting technology since the 30's before the introduction, so far there have been more than eighty years of history. China is also one of the earlier countries to study the squeeze casting technology, from the 1950s to date has been more than sixty years, its development from the process of exploration, theoretical research, production and application, rapid development, stable development and then rapid development of several stages.

Squeeze casting according to the specific form of work can also be called liquid die forging, in simple terms, squeeze casting technology is the liquefaction of the metal injected into the model made in advance, through the application of high pressure so that the liquid metal solidified under mechanical pressure, and gradually molding technology. Squeeze casting has many advantages, compared with other commonly used casting mode, first of all, squeeze casting material selection range, you can choose aluminum alloy, magnesium alloy, titanium alloy, etc.; Secondly, for the utilization of metal is very high, direct squeeze casting can be controlled in the metal utilization rate of more than 95%; In addition, squeeze casting casting formed by the organization of uniformity, surface smoothness, high precision, excellent mechanical properties. And another industry often used in the wake of molding method comparison, squeeze casting forming technology process is simple, forming effect is good, can manufacture complex shape parts and other advantages. Squeeze casting molding technology in the use of metal materials has been widely used in various industries, such as high-speed trains, aerospace, automotive appliances and other fields.

2. Features of squeeze casting molding

The squeeze casting process has special requirements for casting equipment, and currently only part of the castings have better results. First of all, squeeze casting equipment, the need to provide low speed but the flow of liquid metal filling capacity, speed of about 0.5-3m / s, the flow rate of up to 1-5kg / s, so that the molten metal can be smoothly cast within the gas discharge, and fill the casting, and then the casting filled with the instant (50ms-150ms), should be able to cast within the casting casting specific pressure increased to 60-100MPa, so that the Alloy will be able to solidify under high pressure molding. Due to the aforementioned low speed and large flow, and squeeze casting inside the pouring channel has a riser to make up for the role of shrinkage, inside the pouring channel caliber is larger, and is located in the casting of the most fertile parts.

Because of the above characteristics, squeeze casting is suitable for thick-walled castings (10-50mm), but the casting size should not be too large (less than 200mm). The same as die-casting, squeeze casting can only use mold release agent, does not apply insulation coating, so the metal solidification speed is very fast, up to 300-400 degrees Celsius / s, compared with the metal type gravity casting cooling speed, up to its 3-5 times, elongation is higher than the other casting methods about 2-3 times.

3, several major extrusion casting forming technology

3.1. Pressure casting

Pressure casting features: magnesium alloy melting point is very low, good fluidity, good filling capacity, latent heat of solidification is small, fast solidification speed, the thermal shock of the pressure casting type is small. Magnesium alloy and iron basically does not react, will not erode the steel crucible and die casting type, not only to avoid the crucible on the magnesium alloy liquid pollution, but also prolonged the life of the steel crucible and die casting type. Magnesium alloy can be both cold room and hot room die casting, in the appropriate pressure, can obtain complete dense components. Magnesium alloy die casting cold chamber die casting and hot chamber die casting. Among them, hot chamber die casting is generally used for small-size thin-walled, complex shape castings, cold chamber die casting is mainly used for the wall thickness of the mass production of parts.

3.2. Vanishing mold casting

Disappearing mold casting principle is to use and casting shape and size of the plastic mold instead of casting mold, made solid casting, pouring metal liquid so that the plastic vaporization, so as to form the ideal casting. Magnesium alloy disappearance casting has the following advantages: the use of dry sand, to avoid the ordinary sand casting due to moisture caused by the magnesium alloy combustion problems, and disappearance of the mold gasification formed by the reduction of the atmosphere, which can inhibit the magnesium alloy oxidation and combustion; magnesium alloy liquid pouring, so that the plastic film vaporization, the gas material on the magnesium alloy extremely easy to oxidation played a natural role in the protection of the magnesium alloy; ③ magnesium alloy shrinkage rate is large, the dry sand concessions are good, you can avoid magnesium alloy Solidification shrinkage when the warm tendency.

3.3 Centrifugal casting

Centrifugal casting of magnesium alloy is a special molding method newly proposed in the past few years, which is proposed for the preparation of complex thin-walled magnesium alloy high-quality components. Centrifugal casting has the following advantages: the alloy melt in the centrifugal force field under solidification and molding, by the centrifugal pressure is a gradient pressure, compared with other casting process pressurization, has a unique alloy melt filling flow and solidification and molding characteristics. Centrifugal casting process can significantly increase the solidification of the alloy melt shrinkage pressure, reduce shrinkage holes and other casting defects, improve the performance of magnesium alloy.

4 extrusion casting technology outlook

In recent years, the proportion of non-ferrous metal parts in automotive parts is increasing, but most of them are concentrated in the engine parts and non-load-bearing parts, for the chassis security parts, due to its high performance requirements, the use of non-ferrous metal materials to replace ferrous metal materials is still in its infancy. In order to reduce the weight of the car, it is required that automotive castings must be lightweight, thin-walled, precise, tough. Therefore, the cast iron parts of automobiles are constantly replaced by light weight aluminum castings. Extrusion casting instead of ordinary casting, low-pressure casting and part of the forging, in order to achieve the purpose of improving the accuracy of the blank, reduce the machining allowance, reduce the consumption of raw materials, reduce costs is an inevitable trend.

The development trend of the squeeze casting equipment is mainly reflected in the use of such equipment itself is wider, through the most basic technology research and development, so that the original equipment for technological research and development, broaden the molding speed of the equipment, as well as squeeze casting molding process of the use of the scope. For example, the winter to mechanical company through the continuous innovation of technology, the extrusion casting equipment for high precision degree of research and development, so that in the implementation of the extrusion casting process, the extrusion speed reached 0, 05 meters per second and even 13 meters per second degree; and the extrusion casting mode of the interlocking method of innovation, the current commonly used in industrial manufacturing of die-casting machine has a cylinder, hybrid and other types of functionality of the extrusion casting machine. Casting machine. Finally is the control system of such equipment, the control system can complete the whole process of extrusion casting molding, so that the extrusion casting machine to complete the whole process of real-time control effect, the control system from the original operation control into an intelligent assembly control system, optimize the effectiveness of the use of extrusion casting equipment.

5 Conclusion

Squeeze casting as a combination of casting and forging advanced molding process technology, will replace part of the forging process, the production of those due to forging molding difficulties, and general casting can not meet the performance requirements of the parts. The application of squeeze casting forming technology in metal materials is conducive to the substantial realization of energy saving, material saving, cost reduction, can significantly reduce the limitations of impurities in raw materials, and promote sustainable development. But at the same time, increase investment in the development of China's independent intellectual property rights of the squeeze casting equipment and process is an effective way to improve the level of China's squeeze casting, but also the development of China's squeeze casting industry is imperative.

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