| 摘要 |
PURPOSE:To obtain the sheet of Al or Al-alloy excellent in weldability by confining the surface contact resistance of the sheet of Al or Al-alloy. CONSTITUTION:When the thickness of surface oxidized film on the sheet of Al or Al-alloy is >=1500Angstrom , the generation of blow hole in MIG welding and TIG arc welding, the generation of pickup in resistance spot welding, the scattering of molten Al which is called dust and sticking phenomenon to welded sheet, etc., are liable to be generated. The thickness of this surface oxidized film of 1500Angstrom in thickness is equivalent to the contact resistance of 0.1OMEGA of the surface of sheet and it is possible to use contact resistance value industrially as the indicator of the degree of removement of the surface oxidized film of the sheet of Al or Al-alloy. Removement of surface oxidized film can be stably done by removing the surface oxidized film by cleaning by continuously passing the coil-like rolled stock through the lye of which pH is controlled. |
