TITANIUM -> PROCESSING TIPS

 

End Cutting (back to top)

When subjected to localised heat, titanium has a tendency to weld to the tool and to jam. This can be avoided by reducing the cutting speed and ensuring an abundant supply of coolant (oil emulsions, specially treated oils, 5-10% alkali nitrite or phosphate-water solutions). Feed speed should be regular and not too slow.

Turning and Milling (back to top)

Turning tools made of high-speed steels with a high cobalt content or of other hard metals can be used for working with titanium. Climb milling is preferable to conventional milling, since this minimises the risk of damage to the milling tool caused by built up edges and the adherence of the shavings. Please note! Titanium dust and shavings are very combustible.

Please see the tables below for more details on the proper cutting conditions and tool angles for turning and milling titanium materials.

Drilling (back to top)

Drills made of high-cobalt, high-speed steels can be used, with the shortest possible unsupported length of drill and a stronger core than is used for austenitic chrome-nickel steel. To prevent friction build-up, the drill must be applied with maximum pressure and the chips removed frequently by disengaging the drill. Adequate cooling with chlorinated cutting oil is also important.

Planing (back to top)

By reducing the cutting speed to about half of that used for austenitic chrome-nickel steel and using tungsten-carbide cutting tools, planing titanium generally presents no difficulties.

Cutting Conditions and Tool Angles for Drilling (back to top)

Degree of nose (angle)		8 bis 7
Angle of rifling / twist		90
Gradb. kl. Bohrungen Grad		118-140
Twist angle GradHinterschliffwinkel		29-35
GradSchnittgeschwindigkeit		10-12
[m/mm]		8 bis 18
Feed up to 6 mm Ø [mm/U]		0,07 bis 0,1
over 6 mm Ø [mm/U]		0,1 bis 0,2

Thread Cutting (back to top)

Outside threads should be cut on the lathe to prevent the galling that can occur with threading dies, screw plate dies, etc. The thread depth should be increased gradually.

When cutting inside threads, the tap must have a thick core and a shortened cutting edge, with a strong back taper and flank relief. The best rake angle is 5°. Sulphurous cutting oil or a compound containing carbon tetra chloride, molybdenum disulfide or graphite can be used.

Titanium can be sawed at speeds 25% lower than those used for steels. Oxide layers on the surface lead to increased tool wear and must therefore be removed prior to machining by pickling, grinding or sandblasting. Sulphurous or chlorinated oils are used for cooling.

Grinding (back to top)

Titanium can be ground using various, using abundant amounts of the usual coolants and maintaining a low wheel speed.

(4-12 m/s for plain grinding)

Vitrified-bond silicon carbide wheels of grade J, K or L, or corundum wheels work well. For grains finer than 320 there is a risk of rapid wheel adhesion.

Welding Titanium (back to top)

Fusion welding

Keep in mind heated titanium's high affinity for gases!

Hydrogen can already lead to embrittlement at temperatures as low as 250°C.

Burners (back to top)

Jets sized 7 to 8, as well as the use of gas lenses and vertical burners (80-90°) with short arc have proven successful.

Protection (back to top)

The welding zone should be protected from outside air during cooling through argon shielding. It is advantageous here to use porous sintered metal that releases argon without turbulence. Conventional welding argon is inadequate; for titanium welding argon with 99.99% purity and a dew point of 50°C is required.

Root Protection (back to top)

The root side of the piece must be protected during welding by a snugly fitting copper plate and an additional argon shield. An inadequate supply of argon is just as damaging as a stream that is too strong, since this will cause an uneven flow of the weld.

No Welding with Steel or Aluminium (back to top)

Titanium cannot be welded with other construction materials since the connections between the metals would be too brittle. Connections using vanadium or molybdenum are possible but are rarely used in practise.

Electron Beam Welding (back to top)

Electron beam welding is particularly suitable for titanium. Impulse welding is another possibility.

Soldering (back to top)

Titanium can be soldered using several different methods. Difficulties may be encountered due to the fact that intermetallic phases can be formed, making for brittle soldering points. To achieve satisfactory results, it is of the utmost importance that the surfaces be cleaned and descaled.
Experience has shown that flame soldering is a good method to choose. Silver brazing alloys work the best.

Chipless Forming(back to top)

Pure Titanium (back to top)

For cold deep drawing only the softest titanium 3.7025 (Grade 1) is suitable. The harder grades require greater radii and higher forces for bending, chamfering, pressing, flanging, seaming, etc., resulting in a more pronounced springback, so that frequently a cold-hot forming at 250-400°C is preferable. The number of recrystallising interim annealings required is then also reduced. The piece must be heated evenly for good results; suitable lubricants include those containing molybdenum sulphide.

Titanium Alloys (back to top)

At room temperature titanium alloys have a high yield point to tensile strength ratio, usually over 90%, so that only a narrow elastic area remains for plastic formability. Cold forming can therefore be used only in exceptional cases. Recommended are either heat forming at temperatures between 500 and 800°C or cold forming followed by hot pressing. For parts that must be formed precisely this process is indispensable. It eliminates the need for interim or subsequent heat treatments and reduces the scrap rate. The oxide layers that are formed due to air contact during the heating process in general improve the antifriction properties and simultaneously serve as a lubricant medium.

Annealing and Pickling (back to top)

Annealing times and temperatures for recrystallisation and stress relieving for the major titanium materials are shown in the table below. Electric furnaces are can be used for performing these processes, as can gas or oil-fired furnaces if set to an excess air content of 10-15% and provided the piece does not come into direct contact with the gas flame. Optimal are protective atmosphere (inert gas) furnaces and vacuum furnaces.

Slight discolouring that occurs during the stress relieving process can be removed by pickling. Mixtures of 25% HNO3 and 0.5 to 4% HF have proven successful here. For thicker oxide and scale layers we recommend the use of molten salts, such as the Hookerband , which works at a temperature of about 500°C, or sandblasting followed by pickling.

In all annealing and pickling processes there is a risk of hydrogen absorption, so the piece should be carefully checked once processing is concluded.

 

 

PROPERTIES
FIELDS OF APPLICATION
OVERVIEW OF MATERIALS

End Cutting
Turning and Milling
Drilling
Planing
Cutting Conditions and Tool Angles for Drilling
Thread cutting
Grinding
Welding Titanium
Burners
Protection
Root Protection
No Welding with Stell or Aluminium
Electron Beam Welding
Soldering
Chipless Forming
Pure Titanium
Titanium Alloys
Annealing and Pickling