PRODUCTION OF HIGH STRENGTH AND HIGH TOUGHNESS HOLLOW FORGING EXCELLENT IN STRESS CORROSION CRACKING RESISTANCE AND HOLLOW FORGING

摘要

PROBLEM TO BE SOLVED: To provide a high strength and high toughness hollow forging in which the hardness of a base metal is not remarkably reduced even by softening, heating and treating a weld zone, capable of securing ≥65 kfg/mm² proof stress, excellent in stress corrosion cracking resistance and easy in welding assembly. ;SOLUTION: A cast ingot contg., by weight, 0.01 to 0.2% C, 0.10 to 0.50% Si, 0.2 to 1.0% Mn, 0.50 to 1.50% Cr, 0.3 to 1.0% Mo, 0.10 to 0.20% V, 0.0005 to 0.0030% B, 0.01 to 0.05% Al, 0.01 to 0.50% Ti, ≤0.01% N and the balance substantially Fe is heated to a hot forging temp. range, is forged and is formed into a hollow forging, which is then subjected to quenching and tempering, is thereafter welded with a pipe, is heated to less than the Ac₁ point so that the hardness of the welded heat-affected zone becomes to ≤22 HRc and is cooled.;COPYRIGHT: (C)1999,JPO