Steel material for welded steel pipe, having excellent longitudinal uniform elongation, manufacturing method therefor, and steel pipe using same

A method of manufacturing a steel material for a welded steel pipe having excellent longitudinal uniform elongation, the method comprising:

• reheating a steel slab within a temperature range from 1100 to 1200° C., the steel slab including, by wt %, carbon (C):
• 0.02 to 0.07%, silicon (Si):
• 0.05 to 0.3%, manganese (Mn):
• 0.8 to 1.8%, aluminum (Al):
• 0.005 to 0.05%, nitrogen (N):
• 0.001 to 0.01%, phosphorus (P):
• 0.020% or less, sulfur (S):
• 0.003% or less, nickel (Ni):
• 0.05 to 0.3%, chromium (Cr):
• 0.05 to 0.5%, niobium (Nb):
• 0.01 to 0.1%, and a balance of iron (Fe) and inevitable impurities;
• terminating finishing rolling of the reheated steel slab within a temperature range from Ar3 to 900° C. to manufacture a hot-rolled steel plate;
• primarily cooling the hot-rolled steel plate to Bs or higher at a cooling rate of 2 to 15° C./s;
• secondarily cooling the hot-rolled steel plate to a temperature of 350 to 500° C. at a cooling rate of 20 to 50° C./s after the primarily cooling;
• and
• air-cooling the hot-rolled steel plate to a room temperature after the secondarily cooling.