(1) Oxygenated pressure casting is to fill the chamber and cavity with oxygen to replace the air and other gases before filling the cavity with liquid aluminum metal. Its characteristics are: eliminate or reduce the porosity, improve the quality of casting; Simple structure, convenient operation, less investment. (2) Vacuum pressure casting is to remove the air in the die casting cavity first, and then press into the liquid metal. Its characteristics are as follows: it can eliminate or reduce the porosity in the die casting, improve the mechanical properties and surface quality of the casting; The back pressure of the mold cavity is greatly reduced during die casting, and the alloys with lower specific pressure and poor casting properties can be used.
The influence factors of the two metamorphic layer of the middle wire cutting: 1, the metallographic structure and element composition of the workpiece material due to the discharge effect of the electric spark, the metallographic structure of the surface layer of the workpiece material has changed significantly, forming discontinuous. A metamorphic layer of uneven thickness. It is related to parameters such as workpiece material, electrode wire material, pulse power supply and working fluid. Metallographic analysis shows that large austenite remains in the metamorphic layer. When using molybdenum wire electrode wire and working solution containing carbon, the content of molybdenum and carbon elements in the metamorphic layer increased greatly by spectroscopic analysis and electron probe detection. When copper wire electrode wire and deionized water were used, the content of copper element in the metamorphism layer was increased without carburization.