Procedures and Precautions in Machining Titanium Alloys

Abstract

Titanium alloys have unique machining properties. While the cutting forces are only slightly higher than in machining steels, there are other characteristics that make these alloys more difficult to machine than steels of equivalent hardnesses. For example, the chip-tool contact area in turning a titanium alloy is only about one-third to one-half as great as that for turning a steel. Also, the thermal conductivity of titanium alloys is about one-sixth of that of steels. This combination of a small contact area and the low thermal conductivity results in very high cutting temperatures. At a cutting speed of 100 ft. /min., the temperature developed at the cutting edge of a carbide tool is 1000ºF when cutting a steel, while on the titanium alloy, the temperature reaches 1300ºF. Hence, the cutting speeds on titanium alloys must be lower in order to maintain a tool-chip temperature below that which results in short tool life.