PROCESS FOR PRODUCTION OF COMMON RAILS AND PARTIALLY STRENGTHENED COMMON RAILS

This invention relates to a method producing a common rail excellent in fatigue strength from an inexpensive steel which uses as the material of the common rail a steel for high-strength liquid phase diffusion bonding having good toughness and fatigue strength, which steel contains, in mass%, C: 0.01 to 0.3%, Si: 0.01 to 0.5%, Mn: 0.01 to 3.0%, Cr: 1.0 to 12.0% and Mo: 0.1 to 2.0%, further contains, in mass%, V: 0.01 to 1.0%, B: 0.0003 to 0.01%, Ti: 0.01 to 0.05% and N: 0.001 to 0.01%, has P content limited to 0.03% or less, S content to 0.01% or less and O content to 0.01% or less, further has total content of grain boundary segregated embrittling elements As, Sn, Sb, Pb and Zn limited to 0.015% or less, and a balance of unavoidable impurities and Fe. The steel is used for liquid phase diffusion bonding. The production method uses a pulsed laser beam to perform laser-peening in the presence of a transparent liquid with respect to the vicinity of the boundary between the inner surface 21 of each branch hole 6 and the inner surface 22 of the rail hole 5, located at an opening peripheral zone of the branch hole 6. The surface layer of steel of the opening peripheral zone is thereafter removed.