Aviation Titanium Alloy Blade To Realize Several Necessary Conditions Of CNC Belt Grinding And The Corresponding Countermeasures

For aviation engines, once the core machine is finalized, the subsequent development is mainly through the use of new technologies and new designs, increasing the fan diameter, increasing the number of pressurized compressor stages, improving the design of high-pressure compressor and high-pressure turbine blades, and improving the high-temperature-resistant properties of high-pressure turbine blade materials and coatings to improve the efficiency of the components and the thrust of the engine. Among them, the development of high-temperature thermal component materials that characterize the cycle parameters is relatively slow, while the improvement of pressurizer blade and fan blade design is more frequent, and it can be said that titanium alloy pressurizer blade and fan blade manufacturing is one of the key technologies in aero-engine manufacturing.
At present, almost all domestic aero-engine manufacturing enterprises use manual grinding of inlet and exhaust edges to manufacture titanium alloy compressor blades, fan blades and guide blades, with large difference in the thickness of inlet and exhaust edges of the blades, poor consistency, inaccurate profiles, and low quality of the blades. As the turbine industry gradually adopts CNC belt grinding machine to process blade profile and inlet/exhaust edge, aero-engine manufacturing enterprises have also put forward the requirement of adopting CNC belt grinding to process inlet/exhaust edge, and they are eager to solve the problem of inlet/exhaust edge grinding processing of this aero-engine blade manufacturing through CNC belt grinding. In this paper, through the analysis of aviation titanium alloy blade process characteristics and different blade CNC belt grinding production practice, process test, verification analysis, summarize and put forward the aviation titanium alloy blade to achieve CNC belt grinding several necessary conditions and corresponding countermeasures.
Difficulties in grinding inlet and exhaust edges
There is a big difference between the manufacturing process of aero-engine blade and that of turbine blade. The former mainly adopts the molding method, while the latter mainly adopts the material removal method. Turbine blade material is mostly stainless steel, generally first milling out the blade radial surface as a radial datum, machining shoulder or tongue and groove with the top hole as an axial datum, and then use multi-axis linkage machine tools to process the leaf body profile, and finally by CNC belt grinding and polishing is completed; aviation blades are generally made of titanium alloy precision forging, casting method of manufacturing pressurized air blades, the use of diffusion bonding/super-plastic molding (DB/SPF) method Manufacture of titanium alloy wide chord fan blade, blade profile is guaranteed by mold molding, profile accuracy space error of not more than 0.15mm, no longer processed after molding, directly used as a benchmark for profile positioning fixture used to process the root mortise and groove and exhaust edge. Therefore, the processing of aviation titanium alloy blade is mainly the processing of the inlet and exhaust edge, for CNC belt grinding, the processing difficulties are the following major aspects.
(1) aviation blade inlet and exhaust edge is very thin, large fan blade is only R0.3mm or so, some small compressor blade will even reach R0.1mm level. This makes in the belt grinding, must use a very small contact force for grinding, otherwise it is difficult to ensure the accuracy of the profile, which for the belt grinding device contact force control puts forward a very high demand.
(2) Uneven grinding allowance. Forged titanium alloy compressor blade and super plastic molding fan blade generally use milling or wire cutting inlet and exhaust edge forging edge (to ensure that the chord width), and then inlet and exhaust edge grinding and polishing process, this processing characteristics make the inlet and exhaust edge rounded (or local elliptical section) part of the machining allowance is very uneven, the following figure: the red part of the blank outer outline, the arc part of the inlet and exhaust edge of the theoretical curve.

(3) Blade deformation problem. This problem and uneven grinding allowance is the same kind of problem, forging titanium alloy blade and super plastic molding blade are in a certain temperature to complete the deformation, by the residual stress affects the existence of deformation, especially the pressurized air blade, the deformation of the order of magnitude and the thickness of the blade intake and exhaust edge in the same order of magnitude, to 0.1mm or more, which is the general type of aerospace blades and the space error of about 0.05mm compared to the too large, it must be It must be corrected.
(4) Benchmark issues, profile positioning, blade clamping consistency issues. Precision forging blade and super plastic molding blade profile accuracy is very good, but it is still a coarse datum, which is still coarse compared with the milling datum of turbine blade. As mentioned above, this clamping positioning error is comparable to the blade deformation error in order of magnitude, which is also an important influence factor that cannot be disregarded and must be solved by correcting the coordinate system.
In addition, when the inlet and exhaust edge grinding, the cooling conditions are not good, the heat dissipation conditions of the very thin edge are not good, and the blade inlet and exhaust edge is prone to ablation, which also brings certain difficulties to the blade inlet and exhaust edge grinding; for the super-plastic molding fan blade, in addition to the inlet and exhaust edges, the type surface also needs to be ground and polished, and there are also problems of non-uniformity of the type surface allowance, deformation error, and so on.