A semi-solid composite squeeze casting molding method for magnesium alloy castings

Abstract

The invention relates to a semisolid combined extrusion casting forming method of a magnesium alloy casting. With respect to the situation that the slurry quality is difficult to control in magnesium alloy semisolid extrusion casting and the disadvantages that the slurry preparation and forming connection is poor and the stability is poor, by adopting the semisolid combined extrusion casting forming method of the magnesium alloy casting, integration of semisolid slurry preparation and extrusion casting forming is realized through a combined extrusion casting technique. The semisolid combined extrusion casting forming method is advanced in technology, data is precise and full and accurate, the prepared casting is precise in shape, a primary phase consists of spheroidal and near-spheroidal grains, dendritic grains are few, the grain size is reduced, the metallurgical structure compactness is good, the strength of extension reaches 205Mpa, the elongation percentage reaches 6.2%, and the semisolid combined extrusion casting forming method of the magnesium alloy casting is advanced.

Description

technical field [0001] The invention relates to a semi-solid compound extrusion casting molding method for magnesium alloy castings, which belongs to the technical field of magnesium alloy casting molding methods. Background technique [0002] Magnesium alloy has the advantages of low density and high specific strength. It is suitable for lightweight structural parts and is widely used in automobiles, aerospace, computers, communications and other industries. However, the low plasticity and ductility of magnesium alloys at room temperature seriously restrict the application of magnesium alloys. Semi-solid forming technology is the most effective way to improve the plasticity and ductility of magnesium alloys. [0003] Magnesium alloy semi-solid forming technology includes thixoforming and rheological forming. The semi-solid metal blank used in thixoforming has a high solid phase fraction, which is more convenient in transportation and heating, and is easy to realize automati...

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Problems solved by technology

[0003] Magnesium alloy semi-solid forming technology includes thixoforming and rheological forming. The semi-solid metal blank used in thixoforming has a high solid phase fraction, which is more convenient in transportation and heating, and is easy to realize automatic operation. ; However, the cost of thixoforming equipment is high, the processing residues cannot be recovered quickly, the surface oxidation of the billet is caused by secondary remelting, the production cycle is long, and the energy consumption is high, which restricts the development of thixoforming technology; Reheating is required, energy consumption is low, and there are few process links, but rheological deformation is difficult in the quantitative transportation and transfer of slurry. Therefore, high-quality semi-solid slurry can be prepared in a short time. Semi-solid slurry The rapid connection between rheological forming and rheological forming has become the key technology of rheological forming

[0004] Squeeze casting technology is a new metal processing method in the field of semi-solid processing. This technology applies mechanical pressure to the liquid or semi-liquid metal injected into the mold cavity to make the solidified shell plastically deform, liquid or semi-liquid The metal is fed in time under the action of isostatic pressure to obtain castings with dense structure and high mechanical properties; squeeze casting technology has two methods: direct squeeze casting and indirect squeeze casting. Direct squeeze casting is that the pressure directly acts on the liquid state. On the metal surface, the pressure transmission distance is short, but the molten metal must be filled accurately and quantitatively. At the same time, there is a secondary filling process for complex special-shaped parts, which is prone to defects such as cold shuts. Therefore, it is only suitable for the production of castings with simple shapes and symmetrical structures; In indirect squeeze casting, the pressure is transmitted to the metal melt in the mold cavity through the runner, so the pressure transmission distance is long, and defects such as shrinkage and porosity are prone to occur

[0005] How to efficiently and stably combine the semi-solid forming technology with the squeeze casting technology and realize the precise control of the forming process has become the key to the semi-solid forming of magnesium alloy castings; at present, most of the semi-solid squeeze casting technologies for magnesium alloys use pulping first and then extrusion The method of die casting, that is, using electromagnetic stirring, ultrasonic waves and other external fields, or through external devices such as inclined plates and serpentine runners to prepare semi-solid slurry, and then pour the slurry into the cavity of the mold, and realize extrusion on the extruder. Die-casting, the process is complicated, special equipment is required, and the cost is high. In this process, the quality of the slurry is extremely difficult to control. Industrial Application of Semi-solid Forming Technology

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