Titanium alloy is difficult to process how to choose alloy tool material

Titanium alloy is difficult to process how to choose alloy tool material, titanium alloy cutting process selection of Shuo precision tool material characteristics in the manufacturing industry, often encounter processing titanium alloy materials, and due to the characteristics of titanium it is extremely difficult to process; Compared with common metals, titanium alloys have better strength, toughness, ductility, and better oxidation resistance and corrosion resistance. This makes titanium alloys widely used in aerospace, automotive, chemical and medical devices and other fields. The coating of processing titanium alloy tools also plays a good role in cutting tools, good coating can improve the wear resistance of the tool, improve its high temperature hardness, heat insulation performance, thermal stability, impact toughness, etc., so as to greatly improve the cutting speed and service life of the tool. Titanium alloy in toughness, ductility, especially strength is far more than other metal materials, can produce high unit strength, good rigidity, light weight product parts. In recent years, titanium alloy has been widely used in aircraft to replace aluminum alloy, the reason is that titanium alloy has good thermal stability, high temperature strength, at 300-500 ° C, its strength is about 10 times higher than aluminum alloy, and the working temperature can reach 500 ° C. It has superior corrosion resistance to alkali, chloride, chlorine organic items, nitric acid, sulfuric acid, etc. At the same time, titanium alloy in a humid environment and seawater medium, the resistance to pitting, acid corrosion, stress corrosion far exceeds that of stainless steel. Products made of titanium alloy also have high hardness, high melting point, non-toxic, non-magnetic and other characteristics. Based on the above series of excellent properties, titanium alloys are first used in aviation. In 1953, the United States Douglas Company for the first time applied titanium materials to DC2T engine pods and fire walls, and achieved good results. In the aerospace field, the fan, compressor, skin, fuselage and landing gear of the aviation engine are the first to use titanium alloy as a key material, making the overall weight of the aircraft reduced by about 30%-35%, and titanium alloy has also been successfully applied to the pressure housing of nuclear submarines, seawater piping systems, condensers and heat exchangers, exhaust fan blades, thrusters and shafts, springs, and fire protection on aircraft carriers Equipment, propeller, water jet propulsion device, rudder and other Marine components. In addition, due to its good biocompatibility, corrosion resistance, mechanical properties and processing properties, titanium alloy has become the most suitable biomedical metal materials, successfully used in artificial knee joints, femoral joints, dental implants, dental roots and denture metal supports, etc. Among them, Ti6AI4V is commonly used as a medical implant material, and TI3AI-2.5V alloy is also used as a replacement material for femur and tibia in clinical practice because of its good cold formability, corrosion resistance and mechanical properties.

The difficulties of titanium alloy processing (1) the deformation coefficient is small, which is a relatively obvious feature in the cutting of titanium alloy materials. In the process of cutting, the area of contact between the chip and the front tool surface is too large, the chip travel on the front tool surface is much larger than the general material chip, in such a long time walking will lead to serious tool wear, and the friction during the walking process will cause the temperature of the tool to rise. (2) The cutting temperature is high, on the one hand, the deformation coefficient mentioned earlier will lead to a part of the temperature increase. The main aspect of the high cutting temperature in the titanium alloy cutting process is because the thermal conductivity of titanium alloy is very small, and the length of the contact between the chip and the front tool surface is short, under the influence of these factors, the heat generated during the cutting process is difficult to conduct out, mainly stored near the tip of the tool, causing the local temperature to be too high. (3) Vibration, in the finishing process, the low elastic modulus of titanium alloy and the dynamic cutting force are the main causes of vibration in the cutting process. (4) The thermal conductivity of titanium alloy is very low, and the heat generated by cutting is not easy to disperse. The turning process of titanium alloy is a process of large stress and strain, which will produce a lot of heat, and the high heat generated during processing can not be effectively diffused, while the contact length of the cutting edge of the tool and the chip is short, so that a large amount of heat is gathered on the cutting edge, the temperature rises sharply, the blade softens, and the tool wear is accelerated. (5) The chemical effect of titanium alloy is large, and at high temperatures, titanium alloy is easy to react with the tool material to accelerate the formation of the crescent. However, the cutting process of titanium alloys is basically carried out at high temperatures. When the cutting temperature is high to a certain extent, molecules such as nitrogen and oxygen in the air can easily chemically interact with titanium materials, resulting in the formation of a brittle hard skin. In addition, the plastic deformation of the machined surface of the workpiece in the cutting process of titanium material leads to the occurrence of cold hardening phenomenon, and the hardening phenomenon occurs on the machined surface of the workpiece material. These phenomena can aggravate the wear of the tool and reduce the fatigue strength of the titanium material. (6) The tool is very easy to wear, the wear of the tool is the result of many comprehensive factors together, in the cutting process of titanium alloy material, It is easy to cause the breaking of the tool, titanium materials generally show a strong chemical affinity between the tool materials under high temperature conditions, and the tool and titanium alloy material are easy to bond at high temperature, which lead to the service life of the tool is too short. Therefore, the cutting of titanium alloy materials must pay attention to two aspects, that is, to maintain a low cutting temperature and improve the rigidity of the tool or the material being cut, and the coating tool is a way to improve the rigidity of the tool. Due to the high chemical activity and low thermal conductivity of titanium alloy, the cutting temperature is high in the cutting process, the chemical reaction is intense, the tool fails quickly, resulting in short tool life and high processing cost. The causes of tool wear include mechanical friction and physical and chemical reactions under the action of cutting force and cutting temperature. In view of the difficulty of titanium alloy machining, the selected tool materials must meet the requirements of high hardness, high strength, high thermal conductivity, chemical stability and good red hardness. The industry test shows that the processing effect of titanium alloy is better PCD diamond tool, but because of its high price, it limits the wide range of processing, and optimizing the process parameters can make the cutting efficiency of titanium alloy materials be improved to a certain extent, but the range is not large; High pressure cutting fluid, low temperature cutting and heat pipe heat transfer cooling lubrication methods are being studied in this direction