FABRICATING TITANIUM

The fabrication of titanium product forms into complex shapes is routine for many fabricators. These shops recognized long ago that titanium is not an exotic material requiring exotic fabrication techniques. The quickly learned that titanium is handled much like other high performance engineering materials, provided titanium's unique properties are taken into consideration.

Important differences between titanium and steel or nickel-base alloys need to be recognized. These are:

titanium's lower density
titanium's lower modulus of elasticity
titanium's higher melting point
titanium's lower ductility
titanium's propensity to gall
titanium's sensitivity toward contamination during welding

Compensation for these differences allows titanium to be fabricated, using techniques similar to those with stainless steel or nickel-base alloys.

The following sections deal with common operations used in fabricating titanium. The information given is intended to be used as guidelines. It is by no means exhaustive. Further information is available from TIMET and from experienced titanium fabricators.

WORK AREA
The fabrication of titanium demands attention to cleanliness. It is not uncommon for shops which handle several metals to isolate an area to be used especially for titanium. Welding, in particular, requires freedom from contaminants which might degrade the properties of titanium. Thus, the area set aside for titanium should be free of air drafts, moisture, dust, grease and other contaminants which might find their way into the weld metal.

SHEARING
The annealed industrial titanium alloys can be sheared using capacity limitations applicable to 300 series stainless steels. Sheared edges on plate over 3/8-inch in thickness should be inspected for cracks. Filing the sheared edge in preparation for welding is good practice to prevent entrapment of contaminants which might degrade weld properties.

FLAME CUTTING
Oxy-gas cutting processes, useful for steel, can also be used on titanium. Smaller cutting tips and higher travel speeds can be employed. The cut edge on titanium is contaminated with oxygen and carbon and must be removed by grinding or machining. It is recommended that a minimum of 1/16-inch of metal below the lowest point of the cut roughness be removed.
Cutting allowances will include about 1/8-inch for kerf, plus 1/16-inch for roughness, plus a minimum of 1/16-inch for removal of contamination. Thick plate will require larger allowances.

The contaminated cut surface is extremely hard. If machining is to be used to remove the contamination, the tool point must penetrate beneath the contaminated layer or tool life will be short.

CAUTION
Torch cutting of titanium produces large volumes of white, titanium dioxide smoke, which must be vented. In addition, the cutting discharge is extremely hot and brilliant. Measures should be taken to prevent damage from the discharge. Operators should wear dark glasses and full face protection.