What is the difference between titanium plates and stainless steel plates?

1. Turning

The turning of titanium alloy products is easy to obtain better surface roughness, and the 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°.

2. Milling

Milling of titanium alloy products 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. Chipping 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: Climbing milling is generally used. Tool material: high-speed steel M42. Improve the rigidity of the process system in terms of workpiece clamping and equipment.

What needs to be 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, which will cause the knife to hit. For down milling, the cutter tooth hits the crust at the beginning of the cut, causing the cutter to break. However, since the chips of up-milling are 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. In the case of 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. Use sharp tooth milling cutters as much as possible 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 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.

3. Grinding

The common problems in grinding titanium alloy parts are sticky debris causing blockage of the grinding wheel and burns on the surface of the part. The reason is the poor thermal conductivity of the titanium alloy, which causes high temperature 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.

In order to solve this problem, the measures taken are: select the appropriate grinding wheel material: green silicon carbide TL. Slightly lower grinding wheel hardness: ZR1. Coarse wheel size: 60. Slightly lower grinding wheel speed: 10-20m/s. Slightly smaller feed rate, fully cooled with emulsion.

4. Drilling

It is difficult to drill titanium alloys, and the phenomenon of burning tools and broken drills often occurs during the 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 titanium alloy drilling processing: 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. Withdraw 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 tool should be changed and sharpened in time.

Add enough cutting fluid: Soybean oil is generally used, and French OLTIP special oil for drilling and tapping can be added when necessary. Improve the rigidity of the process system: the drilling jig should be fixed on the worktable, the drilling jig guide should be close to the processing surface, and the short drill bit should be used as much as possible. There is also a problem worth noting: 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.

5. Reaming

When titanium alloy reaming, the tool wear is not serious, and cemented carbide and high-speed steel reamers 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 that of drilling should be adopted to prevent the reamer from chipping. Metal processing WeChat, the content is good and worthy of attention. The main problem of titanium alloy reaming is that the reaming is not perfect. The following measures can be taken: use oilstone to narrow the width of the reamer blade to prevent the blade from sticking to the hole wall, but ensure sufficient strength. Generally, the blade width is 0.1 ~0.15mm is better.

The transition between the cutting edge and the calibration part should be a smooth arc, and it should be sharpened in time after wear, and the size of the arc of each tooth should be the same; 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 exiting, and the reaming machine should exit the reamer without stopping.

6, tapping

It is very difficult to tap titanium alloy products, especially small holes below M6mm. Mainly because the chip is small, it is easy to bond with the blade and the workpiece, resulting in a large surface roughness value and a large torque. When tapping, improper selection and improper operation of taps can easily cause work hardening, extremely low processing efficiency and sometimes tap breaks. The solution is as follows:

It is preferred to use a jump-tooth tap with a wire in place, and the number of teeth should be less than that of a 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 in the national standard and it is allowed to increase 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 stoppage in the manual tapping.
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