In the ordinary casting process, the initial crystal grows in the way of dendrites, and when the solid phase rate reaches about 20% the dendrites form a continuous network skeleton and lose macroscopic mobility. If strong stimulation is applied during the solidification of metal, the dendritic network skeleton easily formed during ordinary casting will be broken into dispersed particles suspended in the remaining liquid phase, and this alloy prepared by stirring is generally called a non-dendritic semi-solid alloy. This semi-solid alloy still has good fluidity when the solid phase rate reaches 50%-60% and can be formed using conventional forming processes such as pressure casting, extrusion casting, continuous casting, vacuum casting, etc. to achieve metal forming.
1, Preparation of semi-solid alloys
To realize the semi-solid die-casting, first of all, we must prepare the semi-solid alloy slurry with the non-dendritic organization. The current preparation methods of semi-solid alloy slurry mainly include mechanical stirring method, electromagnetic stirring method, strain-induced melting activation method, jet casting method, semi-solid isothermal heat treatment method, near liquid phase line casting method, and chemical grain refinement method, etc.
2, The application of semi-solid die-casting
It is expected that the main market for semi-solid die-casting is the automobile industry for quite a long period of time, and aluminum alloy and magnesium alloy are the main materials for semi-solid die-casting in the automobile manufacturing industry.
Through the die-casting process real-time control research, so that the whole die-casting process is under dynamic monitoring, improve the performance of die-casting, reduce die-casting scrap, and can make an ordinary die-casting machine for semi-solid metal die-casting forming.
Automotive wheel hubs are mostly made of steel, to reduce the quality of the car now increasingly use aluminum alloy, its forming process is mainly low-pressure casting, but low-pressure casting has a high scrap rate, low productivity shortcomings. The use of semi-solid die-casting forming, can customer service the above disadvantages, and improve the strength of the product, reduce the quality.
The semi-solid metal forming process has various characteristics and advantages that traditional processing and forming technology does not have, in the past decade, the rapid development of semi-solid forming technology, has gradually become a new field of competition, known as a new generation of emerging metal forming technology.