| 摘要 |
PURPOSE: A reinforcing bar is provided to strengthen a fireproof door by being combined to the door with a double-face welding method. CONSTITUTION: A reinforcing bar(3') forms small protrusions(4) in several places in both sides by symmetrically punching the upper end and the lower end. The protrusion unit is welded into an inner plates(2) and an outer plate(1) by a spot welding. Therefore, the spot welding is conducted in a short time and both plates are fully welded, so a fireproof door is prevented from deforming or twisting caused by a long term impact and a noise from the door disappears.
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