The invention discloses a manufacturing method of a seamless steel
pipe. The manufacturing method comprises the following steps of making steel: feeding a SiCaBa
alloy core wire after slagging
molten steel in a steel
ladle, and expanding
slag to form foamed
slag; adjusting the amount, the
alkalinity and the fluidity of the
slag according to slag conditions, and adding SiC
powder,
silicon calcium (
barium),
silicon iron and
calcium carbide so as to reduce refined slag to form white slag; adding 0.13-0.20% of carbon, 0.25-0.50% of
silicon, 0.9-1.3% of
manganese, less than or equal to 0.030% of
phosphorus, less than or equal to 0.030% of sulphur, 0.03-0.10% of
vanadium, 0.015-0.040% of
aluminium, less than or equal to 0.20% of
chromium, less than or equal to 0.10% of
nickel, less than or equal to 0.10% of
molybdenum, less than or equal to 0.10% of
titanium, and less than or equal to 0.20% of
copper; pouring out a part of the refined slag, and retaining a slag layer, the
molten steel surface layer of which is less than or equal to 100 mm; stirring in vacuum; feeding an
aluminium wire with the
diameter of 12 mm after breaking vacuum; feeding a pure
calcium wire for modifying inclusions; blowing by using
argon so that the
molten steel is uniform; continuously
casting; rolling; thermally treating; straightening; and detecting flaws. The seamless steel
pipe prepared by the invention has high strength, high
toughness, low carbon equivalent and good
welding property, and therefore, the use reliability and the safety are increased.