MANUFACTURE OF DEFORMED STRIP

PURPOSE:To prevent adverse expansional phenomena occurring at the forming time of a central thin stepped part by forming a thin stepped parts on both side parts in a 1st rolling stage and forming the central thin stepped part in a 2nd rolling stage. CONSTITUTION:First, a flat strip stock P is set on a work line; 2nd, a shallow groove is formed on both side parts of the stock P by top narrow parts of a roll relating to thin stepped parts; 3rd, the grooves are rolled to spread and to deepen to form an intermediate groove 1'; 4th, the grooves 1' are rolled to have a wider width and a prescribed depth to form both side thin stepped parts 1; 5th, the top part of a roll relating to a central thin stepped part forms a shallow groove at the center of a frustum part; 6th, that groove is rolled to spread and to deepen to form the central thin stepped part 2; 7th, both thin stepped parts 1, 2 are subjected to final skin-pass forming and the stock P is cut at both side thin stepped parts 1 to obtain a special shape strip P'. Thus, the shape and dimensional accuracies of the central thin stepped part are improved.