| 摘要 |
PURPOSE: A high intensity high-frequency welding steel pipe a manufacturing method thereof are provided to suppress the formation of over predetermined sized oxide inclusion on a remaining interface after a welding or to control the amount of bead projection of the inner and outer surface of welding part and remove the spring back phenomenon at the same time, thereby secure the strength above the base material. CONSTITUTION: A high intensity high-frequency welding steel pipe includes a welding unit which is formed by high-frequency welding a base material (1) to a steel pipe. The base material includes carbon of 0.3 to 0.9 wt%, manganese of 15 to 30 wt%, aluminum of 0.01 to 4.0 wt%, silicone of 0.5 wt% or less (excluding 0%), phosphorus of 0.05 wt% or less, sulfur of 0.01% or less, and nitrogen (N) of 0.01 wt% or less (excluding 0%). The base material includes at least one or two kinds of niobium (Nb) of 0.02 to 0.10 wt%, titanium (Ti) of 0.01 to 0.10 wt%, vanadium (V) of 0.02 to 0.05 wt%, remaining iron (Fe) and the other unavoidable impurities. The interface, which is remained after the welding, has Mn-Al based oxide inclusion which has the major axis length of below 3μm. |
