Purpose. To increase the level of homogeneity of the structure and properties of castings made from aluminum alloys, vacuum refining, modification and casting in a protective atmosphere with MHD supply of liquid metal are used. To improve the properties of the secondary alloy ML5, treatment of the liquid metal with a submersible argon-arc plasma torch was used.
Specifications. On the basis of a modernized vacuum MHD installation, a technology for semi-continuous casting of ingots from deformable alloy 1570 has been developed, as well as a technology for the production of master alloys and fibrous nanocrystalline modifiers of the Al-Sc-Zr system necessary for producing ingots. The increase in tensile strength after modification of alloy 1570 with a complex alloy is 5%, and when processing the melt with fibers – 11% compared to ingots obtained using industrial technology. To protect the ML5 alloy from oxidation, SF6 shielding gas was used in the atmosphere of the holding furnace and its pulse supply into the mold at the moment of injecting a dose of metal. The quality of the metal is improved by additional vacuuming of the mold. Increasing the injection speed of a dispersed-turbulent dose of metal to 60 m/s and pre-pressing it at the final stage helps to obtain a dense, defect-free casting with fine fine grains. The new technology, in addition to doubling the weight of the casting, increases its corrosion resistance by more than 5 times.
Application area. Mechanical engineering, metallurgy and foundry.
Advantages. For the first time, the technology of semi-continuous casting of ingots from deformable alloy 1570 based on a modernized vacuum MHD installation was used in practice. It has been shown that in order to obtain high-quality products from the ML5 alloy, it is necessary to use casting machines with a hot pressing chamber. The production of castings is carried out at a pressing pressure increased by 20% and an optimal speed of inlet of liquid metal into the mold of 50-70 m/s. To obtain high-quality titanium casting, it is advisable to use water-cooled casting molds, due to this the strength properties of the castings are increased and the microstructure is dispersed. Castings from VT6 alloy contain 20% beta phase, which is 2 times higher than standard values.
Technical and economic effect. New technical solutions have no analogues in foreign practice and make it possible to improve properties, structural stability and obtain high-quality metal products from non-ferrous alloys with new functionality. New technological solutions make it possible to obtain metal products with increased relative (to the weight of the product) performance characteristics (heat transfer for radiators, weight of fuel tanks up to their capacity for rocketry). The mechanical properties of the VT6 alloy in the cast state exceed standard values by 15-25% and amount to ~1100-1150 MPa with a plasticity level that is twice as low (5-6%). After heat treatment (hardening and aging), the strength of the cast metal increases to 1270 MPa, and ductility increases to ≥ 7.1%.
Advantages. To ensure a residual hydrogen content in ingots of Al-Mg alloys of no more than 0.12 cm3/100g, the technological parameters of the processes for preparing such alloys in an MHD installation and their vacuum refining were determined. When casting ingots from alloys containing easily oxidized elements, crystallizers with a protective atmosphere over the hardening metal are used. To influence the structure and properties of cast products from magnesium alloy ML5, various modes of processing liquid metals with argon and carbon dioxide plasma were used. The technological modes of high-pressure casting of magnesium alloy ML5 are analyzed. The influence of various factors of electron beam casting technology on the structure and phase composition of titanium alloys and their mechanical properties was studied.