Method for removing ceramic core of hollow blade of turbine of aircraft engine

Abstract

A method for removing a ceramic core of a hollow blade of a turbine of an aircraft engine comprises the four steps of primary core removing, secondary core removing, third core removing and ultrasonic cleaning. The concentration of KOH alkali liquor used in primary core removing is 40%, the concentration of KOH alkali liquor used in secondary core removing is 30%, and the concentration of KOH alkali liquor used in third core removing is 40%. Every time core removing is conducted, the temperature of the alkali liquor ranges from 160 DEG C to 200 DEG C, the pressure of the alkali liquor fluctuates between 0.4 MPa and 0.5 MPa, water is added every six hours, and soaking time is 48 hours. According to the method, the concentration of the alkali liquor is reduced, the water is added every six hours, and it is guaranteed that salt generated due to reactions is sufficiently dissolved; the alkali liquor is replaced every 48 hours, the concentration of the alkali liquor changes in a stepped mode, and it can be guaranteed that the chemical reactions are conducted effectively; the pressure of the alkali liquor fluctuates in a pulse mode, core cracking can be facilitated, the reaction interface between the alkali liquor and the core is enlarged, and the reacting dose is increased. Through the method, the ceramic core removing period can be shortened to six days from over twenty days, and the first pass yield of core removing can be higher than 90%.

Description

Technical field [0001] The invention relates to precision casting, in particular to a method for removing a ceramic core of an aeroengine turbine hollow blade. Background technique [0002] Aero-engine turbine blades are currently the most complex hollow blades in China. The ceramic cores in precision casting are extremely difficult to remove, which is one of the bottlenecks restricting the mass production of blades. [0003] According to chemical reaction SiO 2 +2KOH→K 2 SiO 3 +H 2 O, the ceramic core generally uses caustic potash to remove the core. [0004] Based on the fact that the speed of the chemical reaction is related to the concentration, temperature and pressure of the lye, the core removal process of the transmission only pays attention to increasing the concentration of the lye to speed up the reaction under a certain temperature and pressure. For example, the earliest use of molten alkali for core removal is based on this principle. Because the molten alkali damages t...

AI Technical Summary

Problems solved by technology

For example, the earliest use of molten alkali for core removal is based on this principle. Because molten alkali seriously damages blades, and has disadvantages such as low safety and difficult operation, it has now been eliminated.

Subsequent core removal is replaced by high-concentration lye with a mass fraction of 70%, which has a better effect on castings with simple structures, but for blades with complex cavity structures, experiments have found that too high lye concentration is not conducive to the reaction

The reason is that high-concentration lye cannot quickly dissolve the salts generated by the reaction, causing them to form viscose-like substances in the cavity; these viscose-like substances are restricted by the complex cavity and cannot flow out of the cavity quickly. Finally, it covers the reaction interface between the ceramic core and the lye, which hinders the continuation of the chemical reaction between the ceramic core and the lye

As a result, the core removal cycle is as long as 20 days, and the quality of the core removal is poor, and it is easy to store residual cores. The pass rate of the core removal is less than 50%, which not only causes waste of resources and increases in cost, but also affects the development of the engine. and production