The research of titanium alloy grinding has a history of decades in foreign countries. It has in-depth research on titanium alloy grinding mechanism and titanium alloy grinding performance. It has formed applicable codes and standards. , Cooling liquid, processing method, grinding process parameters are clearly defined. At present, it is a very mature technology abroad and has been widely used in the aviation field. The accuracy of products has been greatly improved, making the aerospace manufacturing technology ahead of China for decades.
Features of titanium alloy materials: (1) high specific strength; (2) good heat resistance; (3) good corrosion resistance; (4) small thermal conductivity; (5) small elastic modulus.
Grinding processing characteristics caused by the material characteristics of titanium alloy: (1) high grinding force and high grinding temperature; (2) complicated deformation during grinding; (3) serious adhesion of the grinding wheel, which can cause the grinding wheel Abrasive particles break and fall off.
By carrying out the titanium alloy grinding test, the titanium alloy grinding is studied in depth, and the grinding parameters for suppressing grinding burns and grinding cracks are explored. Factors Affecting Grinding Burns of Titanium Alloys:
The exothermic phenomenon in the grinding area is the main cause of burns. The exothermic result changes the metallurgical structure of the surface layer of the workpiece, which greatly changes its mechanical properties and serviceability.
2. Machine tool
In order to ensure the dimensional accuracy of parts and the stability of various processing parameters, and can achieve contour grinding, vibration grinding and other functions. The machine tool has a vibration grinding function, an operation panel, and a portable operation unit. The speed of the dressing tool can be set. At the same time, it has the function of correcting the entire workpiece and dressing the special grinding wheel.
According to the general principles of material, particle size and hardness selection of grinding wheels for titanium alloy grinding, the grades of grinding wheels suitable for grinding of titanium alloy were determined. The grinding wheel structure is relatively loose and has certain pores. When grinding titanium alloys, the efficiency is higher, the grinding temperature is lower, and the grinding wheel is not blocked. The diamond dressing roller is used to complete the grinding wheel. The hardness of the grinding wheel is medium to soft, and the particle size of the abrasive is 60-120.
Grinding wheel grade:
Norton GC60-J10 V02P 35M / S produced by Saint-Gobain Abrasives
Grinding wheel size: 60
Abrasive material: Silicon Carbide (GC)
Grinding wheel hardness: soft (J)
Grinding wheel structure: loose (10)
Grinding wheel bonding agent: ceramic bonding agent (V02)
The smallest diameter of grinding wheel available: 350mm
The shape of the grinding wheel for grinding arc-shaped teeth is shown in Figure 1. It is a cup-shaped grinding wheel. The length of the grinding wheel is H.
According to the selection principle of the coolant composition and the machine tool manufacturer's recommendation, we have selected the internationally used Castrol semi-synthetic cutting fluid as the coolant for the grinding of titanium alloys, and ensure that the nozzle direction can be directly poured into the parts and the wheel when pouring the coolant On the contact surface, the maximum flow rate is used at the same time to achieve sufficient cooling. Grinding fluid not only has good cooling performance, but also its lubrication performance inhibits the adhesion of the grinding wheel to the titanium alloy and reduces the grinding temperature. The grinding fluid does not contain chlorides or sulfides that contaminate titanium alloys. When grinding titanium alloy, the flow rate of the grinding fluid is not less than 15-20ml / min.
Castrol's semi-synthetic cutting fluid HYSOL X related information: is a high-tech, multi-purpose, bio-stable solvent semi-synthetic cutting fluid with good lubrication and extreme pressure characteristics. A variety of metal processing has excellent performance. Water quality is highly adaptable, but its low foam properties are more prominent in soft water. Can be widely used in the aviation industry. This product is chlorine-free.
(1) Application of coolant: suitable for processing many different metals on high-speed machining centers and flexible machining systems using the latest technology. In processing steel, titanium alloy, cast iron and even various difficult-to-machine metals such as stainless steel, nickel silicon aluminum steel.
(2) The role of the coolant: This product is designed for most metal processing, and is also applicable to large central cooling systems and small cooling devices. Suitable for milling, drilling, boring, reaming, broaching and low-feed grinding.
(3) Advantages of coolant: a. Good processing brightness and can prolong tool life, even for materials that are difficult to process. b. Wide range of applicable materials and processing methods. c. Even at extreme pressures above 70 bar, foaming is rare. d. Does not corrode and pollute aluminum. e. Strong water quality adaptability and long service life. f. Good lubricating characteristics can reduce the residual of lubricating fluid and ensure the machine and parts are clean. g. The operator and the environment are not at risk of contaminating free chlorine, nitrite and phenol. h. It will not damage the paint marks and other markings usually on parts.
According to the machine tool manual and the relevant foreign standards, determine the grinding wheel speed of 35m / s and the workpiece speed of 100r / min. Because the titanium alloy material is easy to adhere to the grinding wheel, it is not easy to dissipate heat. In order to ensure the permeability of the grinding wheel, the grinding wheel is trimmed once before semi-finishing and finishing. After solidifying the basic factors affecting grinding burns, the machine tools, grinding wheels, coolant, and grinding parameters will focus on optimizing the contact area, grinding depth, and feed amount between the grinding wheel and the workpiece.
Titanium alloy grinding burn acid corrosion inspection
(1) The acid, alkali and water tank used for acid etching inspection shall have sufficient volume to ensure that the parts can move freely and be completely immersed.
(2) The container material and the solution in the container shall not react or damage the inspected parts. The container is made of polyvinyl chloride or austenitic stainless steel.
(3) All containers should be labelled with the solution and covered with a lid when not in use.
(4) The acid-etched work site should be well ventilated.
Nitric acid, hydrofluoric acid, alcohol, deionized water
3. Acid etching procedure
(1) Inspection before acid etching. Before the acid corrosion inspection, the surface of the parts shall be free from bumps, scratches, rust spots, etc. that may affect the inspection results.
(2) Degreasing. Immerse the parts in gasoline for washing. If necessary, use a nylon brush dipped in gasoline to wash until the oil is removed completely.
(3) Cleaning. Clean the degreased parts with alcohol for 2 minutes. Ensure that the parts get a wet, stain-free, uniform, and shiny surface.
(4) Erosion. Immerse the cleaned parts in the prepared acid etching solution and shake the parts. The residence time is about 90s at room temperature, and then a macro inspection is performed. If the macro inspection reveals insufficient corrosion, it is etched for another 30 seconds in the original solution.
(5) Rinse. The whole was immersed in running water at room temperature and rinsed for 3 minutes.
(6) Blow dry. Dry parts with clean, dry compressed air.
Inspection method: use Olympus SZX16 solid microscope to inspect all the surfaces to be inspected at a magnification of 10X ～ 30X