When forming titanium sheets hot forming is usually preferred to cold forming, although the latter is sometimes used. Typically, there are four methods used for forming titanium sheets:
• Power Brake
• Drop Hammer
Titanium is most easily formed and at prime working condition when in the annealed condition.
Hydraulic Press Forming
Rubber pad hydraulic press forming can be used to successfully fabricate parts that are flat with contoured or straight edges. Cold work is most effective when done in stages alongside annealing. It is most successful during cold hyropress forming with a semi-finished condition, hot-sizing to blueprint finish and final creep forming.
Cracks or bends can be eliminated during the additional hot forming stage using a specially designed controlled contoured bulge shrink flange.
During creep forming in a furnace or hot sizing equipment dies are machined to blueprint requirements. Typically 10-20 minutes at 1000°F is enough, however time and temperature to hot size are tailored to suit the titanium alloy in question.
Power Brake Forming
Using a round-nosed male punch and through-like female die Brake forming can be used to create angles, hat sections and channels. During this process the sheet metal blank is laid over the trough die and angle created by fabricating the sheet into the trough using the male die.
Angles, hat sections, Z-sections and channels can all be created using stretch forming. This process can be achieved by gripping the specific section in knurled jaws, loading it until plastic deformation begins before wrapping the section around a male die, this process should be done with ultimate care and at a slow pace for the best results possible.
Drop Hammer Forming
Drop hammer forming can be performed at both elevated and room temperatures. Kirksite, the zinc based alloy, is suitable for use with both male and female dies where few parts are required. Steel inserts should be used for larger runs. In drop hammer forming a finished part, which requires little or no handwork can be achieved by warming the female die to almost 300°F removing the chill before heating the blank to somewhere between 800 – 1000°F for a short period of time. To finish the part needs to be struck and set in die.
Hot Vs Cold Forming
During the process of hot forming there is increased ductility, lower forming pressures and reduced springback. Preheated dies are recommended for use to prevent chilling. Once titanium blanks are heated to the point deformation is taking place (Usually at temperatures of 400 – 600°F for commercially pure grades and 800 – 1300°F for the alloy grades) its behavior will change, performing more like annealed 1/8 hard stainless steel. However when commercially pure titanium is cold formed it will act more like 1/8 to ¼ hard stainless steel.
Stress relief aids cold forming when more than once stage of fabrication is required during the forming process. Heat treatment should be used to relieve residual stresses inflicted once all forming procedures are complete.
For more information on the forming processes we offer here at NeoNickel or for advice on all our alloys feel free to contact us today! Don’t forget to check out our Twitter page also, for all our latest news.