Welding equipment for metallic materials and method for welding metallic materials

Abstract

A method for spot-welding metallic materials includes: sandwiching the metallic materials with a pair of electrodes; a pre-heating step for pre-heating a region different from a given region which should be welded by applying electric power having a high frequency to the pair of electrodes; and a welding step for spot-welding a given region of the metallic materials by applying electric power for welding to the pair of electrodes. The heating time in the pre-heating step and that in the welding step are independently controlled.

What is claimed is: 
     
         1 . A method for spot-welding metallic materials, comprising:
 sandwiching the metallic materials with a pair of electrodes;   a pre-heating step for pre-heating a region different from a given region which should be welded by applying electric power having a high frequency to the pair of electrodes; and   a welding step for spot-welding a given region of the metallic materials by applying electric power for welding to the pair of electrodes,   wherein the heating time in the pre-heating step and that in the welding step are independently controlled.   
     
     
         2 . The method for spot-welding metallic materials according to  claim 1 , wherein before ending applying the electric power having the high frequency in the pre-heating step, applying electric power for welding to the pair of electrodes in the welding step starts. 
     
     
         3 . The method for spot-welding metallic materials according to  claim 1 , following the welding step, further containing a step for controlling time and power for applying electric power having the high frequency to the pair of electrodes and heating the spot-welded region of the metallic materials. 
     
     
         4 . The spot-welding method for metallic materials according to  claim 1 , wherein a spot-welding power source is connected to the pair of electrodes for supplying a spot-welding power to the pair of electrodes, and the spot-welding power is either AC electric power having a frequency lower than that of the high frequency or DC electric power. 
     
     
         5 . The spot-welding method for metallic materials according to  claim 1 , wherein before ending applying the electric power having the high frequency in the pre-heating step, applying electric power having a frequency lower than that of the high frequency for welding to the pair of electrodes in the welding step starts. 
     
     
         6 . The spot-welding method for metallic materials according to  claim 1 , wherein before ending applying the electric power having the high frequency in the pre-heating step, applying DC electric power for welding to the pair of electrodes in the welding step starts. 
     
     
         7 . The method for spot-welding metallic materials according to  claim 1 , wherein the electric power applied in the welding step is electric power having a frequency lower than that of the high frequency, and the method further comprises, following the welding step by applying the electric power having the frequency lower than that of the high frequency, a step of controlling time and power for applying electric power having the high frequency to the pair of electrodes and heating the spot-welded region of the metallic materials. 
     
     
         8 . The method for spot-welding metallic materials according to  claim 1 , wherein the electric power applied in the welding step is DC electric power, and the method further comprises, following the welding step by applying the DC electric power, a step of controlling time and power for applying electric power having the high frequency to the pair of electrodes and heating the spot-welded region of the metallic materials. 
     
     
         9 . The spot-welding method for metallic materials according to  claim 1 ,
 wherein an inductance for blocking current is connected between a spot-welding power source and the pair of electrodes,   wherein a capacitor for blocking current is connected between a high-frequency power source and the pair of electrodes,   wherein the inductance blocks high-frequency current supplied from the high-frequency power source to the pair of electrodes so as to prevent the high-frequency current from flowing into the spot-welding power source, and   wherein the capacitor blocks current supplied from the spot-welding power source to the pair of electrodes so as to prevent the current from the spot-welding power source from flowing into the high-frequency power s