The Discovery of Titanium
Titanium was discovered before 1800 and was named after the Titans, the sons of the Sky and Earth gods in Greek mythology. Ever since that time, titanium has been recognized as having one of the highest strength-to-weight rations of any metal. Once it was realized that titanium would work well as a structural metal, people figured out it was tough to machine.
Characteristics of Titanium
Titanium has several characteristics that make it a great structural metal, but these can make machining very difficult. Here are some of the reasons:
- Heat Resistance – Titanium does not absorb heat readily and deflects it quickly, therefore the cutting tool gets hotter than with other metals.
- Work Hardening – The lack of a built-up-edge concentrates cutting forces into the cutting zone, putting tremendous stress on the cutting tool and often times crater wear is greatly increased in the tool.
- “Springiness” – Titanium moves away from the cutting tool, requiring higher pressures on the tool and increased depth of cut to avoid chatter and rubbing. However, these pressures and depths may cause tolerance issues.
These machining hurdles can be overcome with proper tool, fluid and rigidity selection. As a starting point to address these problems, think about machining stainless 316 and other hard metals. The techniques for these metals are often successful when working with titanium.
Machining Tips to Increase Efficiency
Although machining titanium can be challenging, here are some tips to get started or maybe solve some problems:
- Low Cutting Speeds – Low speeds will help keep tool tip temperatures low and help with tool life.
- Moderate Feed Rates – Rates will not affect temperature like speeds, so use a moderate feed rate appropriate for your operation. Through the tool coolant is always best for titanium.
- High Fluid Volumes – Regardless of the type of fluid, use generous amounts to reduce heat and carry away chips/swarf.
- Sharp tools – Tool wear comes quickly with titanium and is difficult to predict and replacing tools a little early can save some trouble.
- Continuous Metal Feed – Work hardening occurs when the tool stays in contact with the metal and can cause surface defects.
- Depth of Cut – Cut deep to overcome deflection of the titanium metal.
Recommended Tools for Machining Titanium
As discussed previously, using sharp tools is critical to titanium machining performance. As such, tools with titanium aluminum nitride coatings (TiAlN) are an excellent choice. These tools offer superior heat and wear resistance as well as reducing chip welding at the insert surface.
Tools to stay away from include ceramics and cubic boron nitride. Ceramic dust created during the machining process is prone to ignition and high titanium machining temperatures increase this risk. CBN suffers from binder degradation with titanium, and this can lead to rapid cratering of the tool.
Choosing a Metalworking Fluid for Titanium
Due to the high temperatures encountered with titanium machining, water-based coolants are the fluid of choice. Water-based products offer superior cooling when compared to oil and do not carry the fire risks associated with oil.
When it comes to which type of coolant, the oil-content in the fluid can be critical. Since water cools better than oil, lower oil-containing products have been shown to give better machining results than high oil products. Of the water-dilutable products, full synthetics with no oil are the best performers. Advancements in tool technology have resulted in cooling and chip removal to be more important than wear protection when selecting a fluid. Ask your coolant provider about the percentage of oil in your coolant. It might be time to consider something else.
If you would like to find out which fluid is best for you or have any questions, send us a message or call us at 562-595-8491 and ask to speak to an Account Manager.