The pressure processing of titanium alloy is more similar to that of steel than that of non-ferrous metals and alloys. Many technological parameters of titanium alloy in forging, volume stamping and plate stamping are close to those of steel processing. But there are also some important characteristics, which must be paid attention to in the pressure processing of chin and chin alloys.
Although it is generally believed that the hexagonal lattice of titanium and titanium alloy has low plasticity during deformation, various pressure processing methods for other structural metals are also suitable for titanium alloy. The ratio of yield point to strength limit is one of the characteristic indexes of whether metal can withstand plastic deformation. The larger the ratio, the worse the plasticity of the metal. For industrial pure titanium in cooling state, the ratio is 0.72-0.87, while that of carbon steel is 0.6-0.65 and that of stainless steel is 0.4-0.5.
Volume stamping, free forging and other operations related to the processing of large section and large size billets are carried out in the heating state (higher than = ys transition temperature). The heating temperature range of forging and stamping is between 850-1150 ℃. Alloy BT; m) 0, bt1-0, ot4 ~ 0 and ot4-1 have satisfactory plastic deformation in cooling state. As a result, most of the parts made of these alloys are formed by the middle annealed blank without heating and stamping. During the cold plastic deformation of titanium alloy, regardless of its chemical composition and mechanical properties, the strength will be greatly improved, and the plasticity will be correspondingly reduced. Therefore, annealing treatment between processes must be carried out.
The groove wear of the blade in titanium alloy machining is the local wear of the back and front along the cutting depth direction, which is often caused by the hardening layer left by the previous machining. The chemical reaction and diffusion of cutting tool and workpiece material at the processing temperature over 800 ℃ is also one of the reasons for the formation of groove wear. Because in the process of machining, titanium molecules of the workpiece accumulate in front of the blade, and "weld" to the blade under high pressure and high temperature, forming chip accretion tumor. The carbide coating of the blade will be taken away when the chip deposit is peeled off from the blade.
Due to the heat resistance of titanium, cooling is very important in the process of machining. The purpose of cooling is not to overheat the blade and tool surface. Use the end coolant, so that the best chip removal effect can be achieved when performing square shoulder milling and face milling of dimples, cavities or full grooves. When cutting titanium metal, the chip is easy to stick to the blade, which causes the next round of milling cutter to rotate and cut the chip again, which often causes the edge line to break. Each blade cavity has its own coolant hole / injection to solve this problem and enhance constant blade performance. Another clever solution is threaded cooling holes. Long edge milling cutters have many blades. Applying coolant to each hole requires a high pump capacity and pressure. However, it can block the unnecessary holes according to the needs, so as to maximize the liquid flow to the required holes.