Manufacture of thin-walled steel castings via consumable additive patterns

Abstract

The problems of thin-walled steel casting are usually connected with insufficient level of alloy fluidity in the field of operating casting temperatures, as well as with appearing counter-pressure for the alloy which fills the narrow mould sections. These sections correspond to thin walls of the future casting, depending on restricted gas permeability of a mould. To solve these problems, the methods of precise casting via thermodeleting patterns, as well as the methods of external effect on metallic melt which fills the mould. This work analyzes the accumulated experience of casting via lost and consumable patterns, the features of their practical realization in the conditions of a casting mould vacuum treatment; their disadvantages are shown as well. The authors formulated the task to eliminate the revealed disadvantages, to provide stability of the technological process and high quality of manufactured castings (in particular for surface defects, non-metallic inclusions, violations of geometrical shape and dimension accuracy) together with lowering of labour intensity and energy intensity of casting in comparison with Replicast–CS-process as a prototype. The innovative technology of casting via consumable patterns was suggested and successfully tested in the conditions of operating production facilities. This technology differs from the prototype in such way, that the patterns are fabricated via additive technologies providing obtaining of internal cellular adjustable structure from the material which is burnt at the temperature not more than the lower temperature threshold of polymorphic transformations of a filling agent of refractory suspension. This refractory suspension is applied on the pattern block with 1-2 layers, sintering of ceramic shell and burning of a pattern block are carried out after placing the pattern block in a moulding box and its filling by fluid self-hardening mixture. Then mould filling by metallic melt is conducted after solidification and restoration of the required gas permeability of fluid self-hardening mixture, while vacuum treatment of the mould is stopped after reaching the solidus temperature by metal. The authors believe that the suggested technology can be used for manufacture of castings of special duty from low-carbon steels and other alloys, which are sensitive to destruction of consumable patterns manufactured via additive technologies (additive patterns).The research was carried out at the expenses of subvention within the framework of Kazan(Privolzhskiy) Federal University in order to rise its competitiveness among the leading global scientific and education centers.