MANUFACTURING DEVICE FOR SPIRAL STEEL PIPE BY COMBINED WELDING

PURPOSE:To perform forming up to side edges of a beltlike steel sheet and to prevent forming of a bamboo nodular joint on the pipe by pushing up pressure rollers for electric resistance welding arranged on a welding joining part. CONSTITUTION:The spiral spiral steel pipe is manuafactured by a combined welding method where an electric resistance welding method and a submerged arc welding method are combined. When the beltlike steel sheet is bent spirally by forming rollers C, plastic deformation is applied on the side edges left as unformed by pressurization rollers D which superpose and pressurize mutually groove projections formed on the beltlike steel sheet side edges mutually. At this time, since the side edges left as unformed are in a projected state outward, the pressurization rollers D are located at the upper level than the lower level of the beltlike steel sheet bend spirally, by which plastic deformability can be increased by the pressurization rollers D. Consequently, forming shortage of bending of the side edges at the time of forming of bending can be filled up and projection of a welded joint part of the manufacture pipe can be prevented.