Titanium cutting process measures include: turning, milling, grinding, drilling, reaming and tapping. Today, we will summarize for you:
【Car cutting】
Turning titanium is easy to obtain better surface roughness, work hardening is not serious, but the cutting temperature is high, and the tool wears quickly. In view of these characteristics, the following measures are mainly taken in terms of tools and cutting parameters:
Tool material: YG6, YG8, YG10HT are selected according to the existing conditions of the factory.
Tool geometry parameters: suitable front and rear angles of the tool, tool tip rounding.
Low cutting speed, moderate feed rate, deep cutting depth, sufficient cooling, the tool tip cannot be higher than the center of the workpiece when turning the outer circle, otherwise it will be easy to stick the tool, and the tool will be biased when finishing turning and turning thin-walled parts. The angle should be large, generally 75-90°.
【Milling cutting】
Titanium alloy milling is more difficult than turning, because milling is intermittent cutting, and the chips are easy to bond with the cutting edge. When the sticky teeth cut into the workpiece again, the sticky chips are knocked off and a small piece of tool material is taken away, forming a collapse The blade greatly reduces the durability of the tool. Metal processing WeChat, the content is good and worthy of attention. Therefore, three measures have been taken for titanium alloy milling:
Milling method: generally adopt down milling.
Tool material: high-speed steel M42.
Improve the rigidity of the process system from the workpiece clamping and equipment.
What needs to be particularly pointed out here is: general alloy steel processing does not use down milling. Due to the influence of the machine tool screw and nut clearance, during down milling, the milling cutter acts on the workpiece, and the component force and feed in the feed direction If the direction is the same, it is easy to cause intermittent movement of the workpiece table, resulting in knife hitting. For down milling, the cutter tooth hits the crust at the beginning of the cut, causing the cutter to break. However, because up-milling chips vary from thin to thick, the tool is prone to dry friction with the workpiece during the initial cutting, which increases the sticking and chipping of the tool. For titanium alloys, the latter contradiction is even more prominent.
In addition, in order to make titanium alloy milling smoothly, the following points should be noted:
Compared with the general standard milling cutter, the rake angle should be reduced, and the back angle should be increased. ; The milling speed should be low. www.t0917.com; Try to use sharp tooth milling cutters and avoid using relief tooth milling cutters; the tip of the tool should be smoothly transferred; use a large amount of cutting fluid. ; In order to improve the production efficiency, the milling depth and width can be appropriately increased. The milling depth is generally 1.5～3.0mm for rough machining and 0.2～0.5mm for finishing.
【Grind cut】
The common problem in grinding titanium alloy parts is that the sticky debris causes the grinding wheel to block and the surface of the part burns. The reason is the poor thermal conductivity of the titanium alloy, which causes high temperatures in the grinding zone, so that the titanium alloy and the abrasive are bonded, diffused and strongly chemically reacted. Sticky chips and blockage of the grinding wheel lead to a significant decrease in the grinding ratio. As a result of diffusion and chemical reactions, the workpiece is burned on the ground surface, resulting in a reduction in the fatigue strength of the parts, which is more obvious when grinding titanium alloy castings. To solve this problem, the measures taken are:
Choose a suitable grinding wheel material: green silicon carbide TL.
Slightly lower wheel hardness: ZR1.
The coarser grinding wheel size: 60.
Slightly lower grinding wheel speed: 10～20m/s.
Slightly smaller feed rate, fully cooled with emulsion.
【Drill cut】
Titanium alloy drilling is more difficult, and tool burn and drill breakage often occur during processing. This is mainly caused by several reasons such as poor sharpening of the drill bit, delayed chip removal, poor cooling, and poor rigidity of the process system. Therefore, the following points must be paid attention to in the drilling of titanium alloys:
Tool material: high-speed steel M42, B201 or cemented carbide.
Reasonable drill sharpening: increase the top angle, reduce the front angle of the outer edge, increase the rear angle of the outer edge, and increase the inverted cone to 2 to 3 times that of the standard drill.
Retract the knife frequently and remove the chips in time, paying attention to the shape and color of the chips. If the chips appear feathery or the color changes during the drilling process, it indicates that the drill is blunt, and the sharpening should be changed in time.
Add enough cutting fluid: generally use soybean oil, if necessary, add French OLTIP special oil for drilling and tapping.
Improve the rigidity of the process system: the drill mold should be fixed on the worktable, the drill mold guide should be close to the processing surface, and the short drill bit should be used as much as possible.
There is another noteworthy problem: When manual feed is adopted, the drill must not stay in the hole, otherwise the drill blade will rub against the machined surface, causing work hardening and dulling the drill.
【Hinge cut】
The tool wear is not serious when titanium alloy reaming, cemented carbide and high-speed steel reamer can be used. Commonly used in factories are W18Cr4V, M42, YW1, YG8, YG10HT, etc. When using cemented carbide reamer, the rigidity of the process system similar to drilling should be adopted to prevent the reamer from chipping. Metal processing WeChat, the content is good and worthy of attention. The main problem that occurs when titanium alloy reaming is that the reaming is not perfect, the following solutions can be taken:
Use whetstone to narrow the width of the reamer blade to prevent the blade from sticking to the hole wall, but to ensure sufficient strength, generally the blade width is 0.1~0.15mm.
The transition between the cutting edge and the calibration part should be a smooth arc. After wear, it should be sharpened in time, and the arc of each tooth must be the same size; if necessary, the inverted taper of the calibration part can be enlarged; reaming twice. The rough reaming allowance is 0.1mm, and the fine reaming allowance is generally less than 0.05mm; the spindle speed is 60r/min; when the reaming is completed, the hand reaming cannot be reversed and exited, and the reaming machine should not stop and exit the reamer.
【攻 丝】
Titanium alloy tapping, especially for small holes below M6mm, is quite difficult. Mainly because of the small chips, it is easy to bond with the cutting edge and the workpiece, resulting in large surface roughness and large torque. When tapping, improper selection and improper operation of taps can easily lead to work hardening, extremely low processing efficiency and sometimes tap breaks. The solution is as follows:
It is preferred to use a threaded jumper tap, the number of teeth should be less than the standard tap, generally 2 to 3 teeth. The cutting taper angle should be large, and the taper part is generally 3 to 4 thread lengths. In order to facilitate chip removal, a negative inclination angle can also be ground on the cutting cone. Try to choose short taps to increase the rigidity of the taps. The inverted taper part of the tap should be appropriately enlarged compared to the standard to reduce the friction between the tap and the workpiece.
When processing the threaded bottom hole, first rough drill and then use the reaming drill to ream the hole to reduce the work hardening of the bottom hole. For threads with a pitch of 0.7～1.5mm, the size of the bottom hole can be machined to the upper difference of the standard thread bottom hole specified by the national standard and can be increased by 0.1mm.
If it is not limited by the position of the screw hole and the shape of the workpiece, try to use machine tapping to avoid work hardening caused by uneven feed and stop in the middle of manual tapping.
