Titanium brazing outline
|Titanium is ideal as the material for the frame of spectacles because of its solidity, lightness and high corrosion resistivity, however, its weak point is the difficulty of machining and joining when compared with those for nickel-silver and hinickel alloy.
This is because the titanium is liable to be embrittled through oxidation and nitridation due to its remarkably activated state realized at the temperature exceeding the transformation point, and also because the elasticity is reduced through being annealed due to the prolonged heating time.
AII the welding machines introduced in this paper have been developed as the brazing machines for the titanium frames, of which operability is excellent and the brazing quality is also high as described in the following.
1 ) When compared with other heating devices, since heat is generated bythe contact resistance on the joining surface, the exothermal efficiency is excellent, the heating time is short, and the surface heat is absorbed by a closely contacting electrode tip, therefore the thermal effect on the periphery is extremely less, and the work is not softened or embrittled.
2) Accuracy is demanded for electrodes and jigs to protect the power supply surface (worksurface). As a result, any operator even unskilled, can make the setting at an accurate position in a short time, and if a technician previously sets the required brazing conditions, the same brazing results can be obtained even by an unskilled
3) The close fitting function by the electrode pressurization is effective to the spreading and fitting of brazing filler metal, and stabilizes the brazing strength. Further, since the junction clearance is small (the brazing layer between the junction surface is thin), the crack is hardly produced on the brazing filler metal and the fatigue life is extended.
4) lt is sanitary since the brazing is carried out in the atmosphere of inert gas without using the flux. It is also economical since the local shielding is made synchronously only at the time of welding.
5) Since aIl kinds ofthese machines are provided with the down slope control, the proper brazing temperature can be maintained through protecting the work from overheating and quenching, leading to make the high quality and stabilized brazing operation possible.