| 摘要 |
PURPOSE:To manufacture economically a seamless pipe excellent in toughness as it is rolled, by subjecting the seamless pipe to specific heat treatment during hot rolling, then by subjecting it to the last rolling, and by cooling it compulsively in a specific temp. range. CONSTITUTION:In manufacture of a seamless steel pipe by hot rolling, a slab is heated to a temp. not lower than 1,200 deg.C, and is worked to an intermediate raw pipe, a sheel, by passing it through a piercer, an elongator, a plug mill and a reeler etc. The shell is cooled with water etc. compulsively to a temp. not higher than 500 deg.C, and is heated once again to a temp. range Ac3-1,000 deg.C so as to make the crystal grains fine. Subsequently, it is finally hot sized to finish to a desired sectional shape. It is either cooled with air, or cooled at a cooling rate not higher than 10 deg.C/sec in the temp. range 800-600 deg., hereby a semaless steel pipe having excellent toughness is manufactured without annealing, tempering and without addition of particular elements. |
