| 摘要 |
<p>Parent patent describes the forming of metal strip into tube, followed by seam welding and drawing of the tube. After welding and before drawing, rolling was employed for continuous redn. of the tube dia., but this process leads to welding defects when mfg. tubes of small dia. (3-48mm. dia.). In this addn. to avoid welding defects on small dia. tubes, the rolling mill is located upstream of the welding operation. The rolling mill pref. uses two rolls which partly close the tube while also reducing the dia. One or more forming funnels fitted with hard metal- or ceramic-rings or grooved rolls may be located upstream of the rolling mill to form the metal strip into tube.</p> |
