NECESSITY OF INCORPORATING HOT-STRETCH REDUCING MILL WITH TUBE WELDING PROCESS IN TERMS OF DEVELOPMENT OF WELDED TUBE TECHNOLOGY——ALSO ON DEVELOPMENT TREND OF DOMESTIC WELDED PIPE CATEGORY

The co-authors describe the history of development of ERW pipe technology with the mid-1950s as a milestone． Before the mid-50s， ERW pipes had been generally produced by means of the continuous furnace process with exception of electrical heating and of hot-stretch reducing mill process to improve quality of weld seam of the low-frequency welded pipe， lessen strip size number and increase productivity of the mill line． Along with the introduction of the hi-frequency welded pipe technique ，use of the said hot-stretch reducing process will increase construction investment and operation costs， damage product quality and fail to get welded pipes “Seamless”． Based on some research achievements made overseas and at home in this field， critcism of the point of view of the so called “Seamless welded tube” is made and proposals concerning developing domestic ERW pipe technologies are put forward．