Laser beam welding method and apparatus

Abstract

While steel sheets are positioned and held by a holding mechanism, a first laser beam is applied to a heating region of the steel sheet to space the steel sheet from the other steel sheet by a predetermined distance. A second laser beam is applied to a welding region to weld the steel sheets. An amount of heat applied by the first laser beam, a moving speed of the first laser beam, and a focused spot diameter of the first laser beam are set to keep the sheet irradiated with the first laser beam in an unmelted state and plastically deform the sheet.

1 . A method of welding overlapping ends of at least three sheets by applying laser beams thereto, comprising the steps of:
 positioning and holding said sheets with a holding mechanism, and applying as many laser beams as the number of at least two interfaces provided by contacting surfaces of the sheets, substantially simultaneously to the interfaces thereby to weld the sheets to each other.   
     
     
         2 . An apparatus for welding overlapping ends of at least three sheets by applying laser beams thereto, comprising:
 a holding mechanism for positioning and holding overlapping ends of said sheets;   a laser beam applying mechanism for applying as many laser beams as the number of at least two interfaces provided by contacting surfaces of the sheets, substantially simultaneously to the interfaces; and   an amount-of-heat control mechanism for controlling the amounts of heat applied by said laser beams depending on the material and/or thickness of said sheets.   
     
     
         3 . An apparatus for welding overlapping ends of at least three sheets by applying laser beams thereto, comprising:
 a holding mechanism for positioning and holding overlapping ends of said sheets;   a laser beam applying mechanism for applying as many laser beams as the number of at least two interfaces provided by contacting surfaces of the sheets, substantially simultaneously to the interfaces; and   an applied position control mechanism for controlling the applied positions of said laser beams depending on the material and/or thickness of said sheets.   
     
     
         4 . An apparatus for welding overlapping ends of at least three sheets by applying laser beams thereto, comprising:
 a holding mechanism for positioning and holding overlapping ends of said sheets;   a laser beam applying mechanism for applying as many laser beams as the number of at least two interfaces provided by contacting surfaces of the sheets, substantially simultaneously to the interfaces;   an amount-of-heat control mechanism for controlling the amounts of heat applied by said laser beams depending on the material and/or thickness of said sheets; and   an applied position control mechanism for controlling the applied positions of said laser beams depending on the material and/or thickness of said sheets.