Trumpf Laser- Und Systemtechnik Gmbh

Marcel Schäfer

Philipp Scheible

Tim Hesse

Nicolai Speker

Thomas Graf

Patrick Haug

Steffen Kessler

Peter Stritt

Methods for determining the quality of a weld of a workpiece welded by laser-beam welding, wherein at least a partial region of a molten pool and/or of a surrounding area of the molten pool is observed by means of a measuring system during the laser-beam welding and the quality of the weld of the welded workpiece is determined on the basis of the observation result. At least one characteristic value that correlates with molten pool oscillation of the molten pool is observed during the laser-beam welding and a measure of an amplitude of the molten pool oscillation and/or a measure of a frequency of the molten pool oscillation is determined from the observed time curve of the characteristic value. A probability and/or a frequency for the occurrence of hot cracks at the weld of the workpiece is inferred.

Detection of hot cracks in laser welding

A laser beam directed is moved relative to a workpiece to weld along a weld seam and form a weld pool in the area surrounding the laser beam. The weld pool has a characteristic oscillation frequency f, and a laser power is modulated with a modulation frequency f and a modulation amplitude &#x3a0;=1&#x2212;P/P, where Pis minimal and Pis maximal laser power during a modulation period. For a normalized characteristic oscillation frequency &#x39b;and a normalized modulation frequency &#x39b;, &#x39b;&#x2265;2.2*&#x39b;, with &#x39b;=f&#xb7;d/&#x3bd;, where &#x3bd; is the feed rate of the laser beam, and dis diameter of a beam focal spot. Also, &#x39b;=f&#xb7;d/v, where fis a measured characteristic oscillation frequency, dthe diameter of the beam focal spot, and vis the feed rate of laser beam, all during a test measurement without modulation of the laser power.

Laser welding of steel with power modulation for hot-cracking prevention

Growing community of inventors

Ditzingen, Germany

Marcel Schäfer