Titanium and titanium alloy quirks (heat, welding, ignition)

?Likely causes

• Thermal conductivity is low, so cutting heat concentrates at the cutting edge and the tool wears easilyAgreed by 2+ makers^{[1][2][3][4][5]}
• It is chemically active and reacts with the tool at high temperature, causing seizure and weldingAgreed by 2+ makers^[1][5][3]
• Young's modulus is about half that of steel, so deflection and chatter tend to occurOne maker^[1]
• Large fluctuation in cutting force causes chippingOne maker^[2]
• Low feed causes work hardeningAgreed by 2+ makers^[3][6]
• Chips tend to be recut in slotting and pocketingOne maker^[7]
• Titanium is classified as a flammable solid that may explode as dust or ignite on contact with air (take care when handling fine chips)One maker^[8]

✓Fixes

Cutting conditions

• Keep the cutting speed low to hold down the cutting temperatureAgreed by 2+ makers^[1][9][3]
• Do not reduce the feed too much (so that heat escapes into the chips and work hardening is avoided)Agreed by 2+ makers^[3][6]
• Keep the tool load constant with climb milling (chips going from thick to thin), trochoidal milling, and similar methodsAgreed by 2+ makers^[3][5]

Tool

• Use a sharp edge with a large rake angle and tools designed for titaniumAgreed by 2+ makers^[3][2][5]

Setup

• Grip firmly with a rigid machine and a shrink-fit or hydraulic holderOne maker^[3]
• Prepare for ignition from sparks and chips, and take fire prevention measures when using non-water-soluble oilOne maker^[10]

Coolant

• For drills and end mills, use water-soluble fluid in large volume at high pressure; for taps, use non-water-soluble fluid with priority on lubricityAgreed by 2+ makers^{[11][1][3][5]}

Where sources differ: No Japanese primary source from a tool manufacturer was found on ignition of titanium chips itself. The basis for ignition is only the MHLW GHS classification (titanium in general) and Mitsubishi Materials' general fire precautions.

▦Notes by material

• Pure titanium: Easier to machine than titanium alloys, and tools for stainless steel can be used^[2][12]

↔Related problems