Product Code: PIC2008_406

Automated, Diodelaser-Based Brazing of Carbide Tips for Optimised Saw Blade Fabrication
Authors:
Christian Stahlhut, Laser Zentrum Hannover e. V.; Hannover Germany
P. Kallage, Laser Zentrum Hannover E.V.; Hannover Germany
A. Ostendorf, Laser Zentrum Hannover E.V.; Hannover Germany
H. Haferkamp, Laser Zentrum Hannover E.V.; Hannover Germany
H. Brand, Laser Zentrum Hannover E.V.; Hannover Germany
P. Dtgen, Laser Zentrum Hannover E. V. ; Hannover Germany
Presented at PICALO 2008

For the increase of wear-resistance circular saw blades are equipped with carbide tips of different composition. At present, inductive brazing is the exclusive joining process, in order to achieve sufficient connecting characteristics between the tool steel master blade and the carbide tip. For induction brazing a typical, wide thermal load on the saw tooth entails hardness increase and thus a degradation of the mechanical properties. Moreover, thermal distorsion of the saw blade makes an additional, expensive straightening process necessary.Laser beam brazing is characterised by a locally and temporally precise control of energy input, resulting in almost no hardness increase of the saw tooth with increased strength of the connection. From first successful laboratory brazing investigations no definite information about the useful properties of an automatically brazed saw blade could be achieved yet.Because of that, a conventional induction brazing automat was retooled on laser-based brazing. For this the inductance loops were dismantled, the tooth support and -mounting plate changed and a one inch optic processing head of a fibre-coupled diode laser and a high-power laser mirror were integrated into the automat. The laser beam is projected onto the cutting face of the carbide tip, so the brazing zone is heated uniformly by heat conduction. This brazing strategy enables a much smaller heat input into the master blade, compared to conventional inductive brazing. Moreover, a reduction of manufacturing time due to this new laser application could be achieved.The test results show a reduction of brazing time of 33%. The metallographic investigations from cross sections of the brazing zone exhibit an extremely reduced heat affected zone. The degradation of mechanical properties of the master blade can be completely avoided by adapting the parameters.