This invention discloses a production process for T250 seamless steel pipes. The steel composition for T250 seamless steel pipes, by
mass percentage, is: C: ≤0.007%, Si: ≤0.12%, Mn: ≤0.13%, P: ≤0.01%, S: ≤0.007%, Ni: 17.8~20.2%, Cr: ≤0.60%, Co: ≤0.60%, Mo: 2.65~3.35%, Ti: 1.1~1.7%, Al: 0.03~0.17%, Cu: ≤0.60%, O: ≤0.0 The steel
pipe has the following specifications: 0.25% N, ≤0.0025% N,
hardness ≤34HRC, grain size ≥5, tensile strength ≥1760MPa, yield strength ≥1660MPa (Rp0.2), elongation ≥6.0%, reduction of area ≥45.0%, average full-size
impact energy at
room temperature longitudinal Charpy V-notch ≥14J, outer
diameter φ114~φ325mm, and wall thickness 15mm~55mm. The manufacturing process includes billet preparation,
forging,
solution treatment of the forged bar,
forging processing,
extrusion molding, solution heat treatment, and aging heat treatment. This invention improves
metal purity, refines bar grains, reduces component segregation, enhances
material density, and stabilizes mechanical properties; eliminates shrinkage cavities and cracks, improving finished product quality; and enables seamless steel to maintain stable performance in high-temperature and corrosive environments (such as
marine engineering), suitable for extreme working conditions, and applicable to the production of high-performance seamless steel pipes.