| 摘要 |
PURPOSE:To remove coating film only from the surface of lapped edge and to minimize the area of exposed iron in resistance welding of lapped edge of a blank of tin free steel by bending the edge along the boundary line and removing the chromium coating film. CONSTITUTION:The edge 17 of a blank 16 of tin free steel is bent in two steps to form a step 18. It is then so formed that the upper face 17a1 of the right side edge 17a in the figure which is to become a lapped part is positioned nearly parallel to the upper face 16a and slightly higher than the face, and the lower face 17a2 of the left side edge 17a in the figure is positioned nearly parallel to the lower face 16b and slightly higher than the face. The chrominum coating film 5 on the faces 17a1, 17a2 is removed by a rotary removing tool 9 having nearly horizontal axial line while carrying the blank 16 in the direction of the arrow, and an exposed part 10 of iron is formed. In this case, even if shaking of rotation occurs in the tool 9, proceeding of the part 10 to the part 18 or inside thereof crossing the boundary 21 between parts 17a, 18 does not take place. |
