Method for preparing a precoated sheet and associated installation

A method for preparing a precoated sheet in view of its welding to another sheet, the method comprising the following successive steps:

• providing a precoated sheet comprising a metallic substrate with a precoating on at least one face of the precoated sheet;
• and
• removing through laser ablation at least one portion of the precoating on the at least one face of the precoated sheet in a removal zone, the laser ablation being performed in a direction of ablation, the laser ablation being carried out in an installation,
• wherein the installation comprises at least one protective element comprising a protective surface, and
• during the laser ablation, the protective surface contacts the precoated sheet in register with a laser beam as the laser beam removes the at least one portion of the precoating through laser ablation, the contact between the protective surface and the precoated sheet defining a contact area, the contact area delimiting an outside of the precoated sheet including the at least one portion of the precoating and an inside of the precoated sheet on an opposite side of the contact area as the outside,
• a plane tangent to the protective surface at the contact area forms a dihedral angle with a plane of the at least one face of the precoated sheet, the dihedral angle being strictly smaller than 90°, the dihedral angle being the angle between a portion of the at least one face of the precoated sheet located on an inside of the contact area and a portion of the tangent plane extending away from the precoated sheet, and
• the protective surface is located on a trajectory of precoating material ejected sideward toward an inner edge of the removal zone during the laser ablation, a path of the laser beam not being located along the inside of the precoated sheet.