| 摘要 |
In the production of spiral tubes, the maximum required curvature of the strip for producing the tube is first determined, so that the finished tube has the desired residual moment. After bending the strip to the maximum curvature, the said strip can spring back out of the bent state. The maximum curvature is determined by taking into consideration the thickness, the Young's modulus and the yield stress of the strip and also from the desired curvature of the finished tube and its required residual moment. By adjusting the position of three rows of shaping rollers which are arranged at the corners of a triangle, the flat strip is continuously bent to form a spiral which exhibits the maximum curvature determined in this manner. The spiral-shaped strip thus obtained can spring back to the diameter of the finished tube, and the extent of this springing back is interrupted if the tube diameter is reached before complete springing back; if the springing back stops before the tube diameter is reached, the spiral-shaped strip is widened. Finally, the seam of the spiral-shaped strip is welded when the said strip has the desired final tube diameter. <IMAGE>
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