Turning of titanium alloy parts (3)

The increasing use of titanium alloys has driven the development of cutting technology with a focus on efficient turning of titanium alloys. Chris Mills, senior manager of process management and technical support at Sandvik Coromant, emphasizes that chemical wear is the primary tool failure mechanism when turning titanium, and high temperatures accelerate chemical wear. When the hot swarf slashes across the rake face of the tool, the cobalt is actually "pushed out" from the blade. Mills describes how to reduce the cutting temperature in two steps: the first step is to use a tool geometry design (such as a square or round blade with a 45° lead angle) to reduce the chip thickness to reduce the cutting temperature and reduce The resulting crater wear can eventually lead to higher feed rates and longer tool life; the second step is to use a high pressure coolant with a special morphology. Not only does this coolant have high pressure, but it also exhibits a very precise laminar spray pattern that creates a “water wedge” between the chip and the rake face of the insert to hold the chip and minimize contact with the rake face. To avoid crater wear.

Sandvik's Jetbreak cooling system has a pressure of 1000-3000 psi and uses a 1.27mm diameter nozzle and a standard emulsified coolant that not only cools but also lifts the lifting force of the chips, reducing chip and rake faces. Friction and temperature between. Use this system to increase cutting speed by 50%.

Mills describes the effect of combining the two cooling strategies described above: when machining a titanium alloy with a CNC cutting blade with a -5° lead angle with optimized cutting parameters (cutting speed: 40 m/min, feed rate: 0.3 mm/rev) Tool life is about 20 minutes; when machining with a round insert or a square insert with a 45° lead angle, the cutting speed can be increased to 50-60m/min, the feed rate is increased to 0.4mm/rev, and it can be similar. Tool life. Since more workpiece material can be removed at the same time, the productivity can be doubled by using only a square blade. If a high pressure cooling system is used, the cutting speed can be increased by another 50%.

The high pressure coolant must be transported through the passage inside the machine spindle (instead of the external pipe). The coolant flows through a dedicated connector on the Sandvik Capto quick change tool chuck, which is controlled by Capto. This high pressure cooling system can be easily installed when the machine is installed.

For workshops that often process titanium alloy parts (especially expensive large aerospace parts), increasing productivity by 50% is worth investing in special tool chucks and machines with high-pressure cooling systems. This high-pressure cooling system has a unique advantage in turning titanium alloys because it does not produce crater wear as much as other workpiece materials.

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