The processing difficulties of titanium alloy structural parts and the factors affecting the processing deformation of weakly rigid structures, and the control methods of processing deformation of weakly rigid structural parts are proposed from several aspects, such as the selection of machine tools, the selection of cutting tools, and effective cooling. Titanium alloy materials have excellent properties such as light weight, high strength and high temperature resistance. For example, using TC18 titanium alloy instead of high-strength structural steel as landing gear, the aircraft structure can reduce the weight by about 15%. Therefore, the new high-strength titanium alloy is widely used in the main bearing parts of foreign advanced airplanes. For example, in the U.S. B-1 bomber fuselage structure materials, titanium alloy accounts for about 21%; Russian Il-76 aircraft titanium amount has reached 12.5% of the weight of the fuselage structure. From the development trend, the use of titanium alloys in Europe and the United States has gradually increased, which also indicates that the extensive use of titanium alloys, especially some new titanium alloys, has become the development direction of aerospace design. However, most aerospace products use thin-walled parts with relatively complex structures and high precision requirements. Due to the thin wall resulting in poor stiffness of the part, it is easy to produce processing bending deformation under the action of the cutting force, and the wall thickness dimension is inconsistent, resulting in super poor. At present, the common method used by enterprises is repeated finishing milling. Due to the small thermal conductivity of titanium alloy, low modulus of elasticity (about 1/2 of steel), high chemical activity, small margin, can not be milled, often resulting in less cutting phenomenon. In order to ensure that the size of the parts can only be manually polished, the processing cycle of the parts is greatly improved, and the surface of the parts may be overheated.
Titanium alloy structural parts parts cutting processing solutions
The main factors affecting the processing of titanium alloy weak rigid structure are: machine tool just tool selection, process parameters, effective cooling and so on. In the processing process, the role of various factors, the interaction of influence, the accumulation of deformation errors resulting in the processing of the weak rigid structure of super poor, processing deformation is difficult to control.
Selection of machine tools
Machine tool - fixture - tool rigidity is better, the clearance between the machine tool components should be adjusted, the spindle radial runout should be small.
Tool selection
The development and application of new cutting tool materials is mainly the result of improved cutting productivity. Cutting tools have evolved considerably over the past few decades to include carbide coatings, ceramics, cubic boron nitride, and polycrystalline diamond. These are effective for machining cast iron, steel and high temperature alloys. However, none of these tools have improved the machinability of titanium alloys because the cutting tool materials used to cut titanium alloys require very important properties, these include
(1) Good thermal hardness to resist very high stresses;
2) Good thermal conductivity to reduce thermal gradients and thermal shock;
3) good chemical inertness to reduce the tendency to react chemically with titanium;
4) good toughness and fatigue resistance to accommodate chip splitting processes. Tungsten carbide-based (WC/co) carbide tools are considered to perform in almost all titanium cutting processes. Some tests have shown that all carbide-coated tools have a greater wear rate than those that are uncoated. Although the quality of ceramic tools has improved and they are increasingly being used for machining hard-to-cut materials, especially high-temperature alloys (e.g., nickel-based high-temperature alloys), they have not replaced cemented carbide and high-speed steel because of their poor thermal conductivity, low fracture toughness, and reaction with titanium. When cutting titanium alloys, carbide cutter materials (cubic boron nitride and polycrystalline diamond) have low wear rates and good performance.
Thin wall milling deformation is the main problem in the milling process of titanium alloy weakly rigid structural parts. Due to the low modulus of elasticity of titanium alloy, the cutting force is relatively large, the thin wall is easy to deform in the milling process, the result is that the actual thickness of the thin wall is greater than the theoretical thickness. To solve this problem, it is necessary to minimize the milling process of the thin wall by the perpendicular direction of the machining surface caused by the deformation of the thin wall force.
