Titanium alloy has low density, high specific strength (strength/density), good corrosion resistance, high heat resistance, good toughness, plasticity, and weldability. Currently, titanium alloy has been widely used in many fields such as aerospace, automobiles, medicine, sports goods, and electrolytic industry. However, poor thermal conductivity, high hardness, and low elastic modulus also make titanium alloys difficult to machine metal materials. This article summarizes some process measures in titanium alloy cutting based on its process characteristics.
Try to use hard alloy cutting tools as much as possible. Tungsten cobalt hard alloys have the characteristics of high strength and good thermal conductivity, and are not prone to chemical reactions with titanium at high temperatures, making them suitable for processing titanium alloys.
Reasonable selection of tool geometric parameters for titanium alloy parts processing technology. To reduce cutting temperature and reduce tool adhesion, the tool rake angle can be appropriately reduced by increasing the contact area between the chip and the rake surface to dissipate heat; At the same time, increase the back angle of the tool to reduce the phenomenon of tool adhesion and reduced accuracy of the processed surface due to the rebound of the processed surface and frictional contact with the back surface of the tool; The tool tip should adopt arc transition to enhance tool strength. When processing titanium alloy, it is necessary to frequently grind the cutting tool to ensure its sharp edge and smooth chip removal
Suitable cutting parameters. The following plan can be used to determine cutting parameters: lower cutting speed - high cutting speed will cause a sharp increase in cutting temperature; Moderate feed rate - high feed rate leads to high cutting temperature, while low feed rate leads to accelerated wear of the blade due to long cutting time in the hardened layer; Greater cutting depth - cutting with the tool tip over the hardened layer on the surface of titanium alloy can improve tool life.
During machining, the cutting fluid flow rate and pressure should be high, and the machining area should be fully and continuously cooled to reduce the cutting temperature.
When selecting a machine tool, attention must always be paid to improving stability to avoid vibration trends. Vibration can cause the blade to shatter and damage the blade. At the same time, the rigidity of the titanium alloy processing system is better to ensure that a larger cutting depth is used during cutting. However, the titanium alloy processing has a large rebound and clamping force, which can exacerbate workpiece deformation. Therefore, during precision machining, auxiliary support such as assembly fixtures can be considered to meet the rigidity requirements of the process system.
The milling method generally adopts forward milling. In titanium alloy processing, the sticking and chipping of the milling cutter caused by reverse milling are much more severe than the damage of the milling cutter caused by forward milling.
The common problems in grinding are the blockage of the grinding wheel caused by chips and the surface burns of the parts. Due to the processing technology of titanium alloy parts, it is advisable to use green silicon carbide grinding wheels with sharp abrasive particles, high hardness, and good thermal conductivity during grinding; F36~F80 can be used according to the different grinding wheel particle sizes of the processed surface smoothness; The hardness of the grinding wheel should be relatively soft to reduce the adhesion of abrasive particles and debris, and to reduce grinding heat; The grinding feed should be small, the speed should be low, and the emulsion should be sufficient.
When drilling titanium alloy, it is necessary to grind the standard drill bit to reduce the phenomenon of burning and breaking the drill bit. The machining process and grinding method for titanium alloy parts: appropriately increase the top angle, reduce the front angle of the cutting area, increase the back angle of the cutting area, and double the taper of the cylindrical edge. During processing, the number of tool retractions should be increased. The drill bit should not stay in the hole, and the chips should be removed in a timely manner. Sufficient emulsion cooling should be used to observe the dull of the drill bit, and the chips should be removed in a timely manner. Sufficient emulsion cooling should be used to observe the dull of the drill bit, and it should be replaced and polished in a timely manner.
Titanium alloy reaming also requires the modification of standard reamers: the width of the blade of the reamer should be less than 0.15mm, and the cutting and calibration parts should have a circular transition to avoid sharp points. When reaming, a group of reamers can be used for multiple times of reaming, with each increase in the diameter of the reamer below 0.1mm. The spindle speed should be slightly slower, and the machine should not stop when retracting the tool. Reaming holes using this method can achieve high smoothness requirements.
Tapping thread is the most difficult part in titanium alloy machining. Due to excessive torque, the tap teeth will quickly wear out, and the rebound of the processed part can even cause the tap to break in the hole. When using a regular tap for machining, the number of teeth should be appropriately reduced according to the diameter size to increase the chip holding space. After leaving a 0.15mm wide blade on the calibration teeth, the back angle should be increased to about 30 °, removing 1/2 to 1/3 of the tooth back, and retaining 3 buckles of the calibration teeth before increasing the taper degree. It is recommended to use a jumping tooth tap to effectively reduce the contact area between the tool and the workpiece, and the processing effect is also good.
To learn more about precision parts processing, please contact Dongguan Boxin Precision Machinery Co., Ltd., website: www.gddgbx.com
