Abstract: A method of laser welding steel sheets that have a thin corrosion protective coating of zinc. The steel sheets are positioned vertically. A pulsed laser beam, which is positioned normal to the sheets is applied to the sheets to melt the material of the sheets and create a weld. During welding, the laser beam is pulsed ON and OFF and the sheets and pulsed laser beam are moved vertically relative to each other such that laser heating of the material creates a cavity. Liquid or molten material flows vertically downwardly by gravity to elongate the cavity and thereby facilitate the escape of zinc vapors from the cavity.

Abstract: A method of laser welding steel sheets that have a thin corrosion protective coating of zinc. The steel sheets are positioned vertically. A laser beam, which is positioned normal to the sheets is applied to the sheets to melt the material of the sheets and create a weld. During welding, the sheets and laser beam are moved vertically relative to each other such that laser heating of the material creates a cavity. Liquid or molten material flows vertically downwardly by gravity to elongate the cavity and thereby facilitate the escape of zinc vapors from the cavity.

Abstract: Ultrasonic transducers spring biased into seating engagement in a pair of opposed spot welding tips transmit and receive ultrasonic waves and associated circuitry measures the time of flight between the transducers which is a function of tip separation, workpiece temperature and nugget size which are indicators of the progress of a weld. The rate of change of flight time is measured and the weld current is adjusted early in the weld cycle to maintain a preset rate of weld growth. The weld current is terminated later in the cycle if the transit time rate falls below another preset value. Otherwise the weld current and termination time follow a standard schedule.

Abstract: To obtain a measure of the size of a spot weld nugget, the weld is scanned with an ultrasonic beam of about 20 megahertz frequency. The ultrasonic signal transmitted through the part is analyzed to determine the presence of the part and the presence of a weld. The detected signal is gated to pass a portion of the signal which has been multiply reflected through the weld region to a bandpass filter which passes frequencies that are selectively attenuated by a weld nugget much more than the surface bond or stick zone surrounding the nugget so that the energy content of the filtered signal is used to determine the presence of nugget material at any point during the scan. A chart recorder controlled according to the energy content of the filtered signal produces a characteristic signature for each weld which distinguishes between the extent of the stick zone and the nugget of each weld so that the weld nugget size is readily determined.