Patent ID: 8354613

Claim:
A method of producing a common rail, wherein the common rail is tubular, having a cylindrical wall enclosing a rail hole and multiple branch holes formed in the cylindrical wall, the branch holes connected to the rail hole, and wherein the cylindrical wall of the common rail is a steel for high-strength liquid phase diffusion bonding having good toughness and fatigue strength, the steel comprising, 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%, Mo: 0.1 to 2.0%, V: 0.01 to 1.0%, B: 0.0003 to 0.01%, Ti: 0.01 to 0.05%, N: 0.001 to 0.01%, a P content limited to 0.03% or less, a S content limited to 0.01% or less, an O content limited to 0.01% or less, a 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 method comprising: obtaining liquid phase diffusion bonded steel in a shape approximately that of the common rail; laser-peening with a pulsed laser beam a proximal region of a boundary between the inner surface of each branch hole and the inner surface of the rail hole, wherein the irradiated region is in contact with a transparent liquid; and removing a surface layer of steel from a region of the opening peripheral zone where a residual compression stress is reduced by melting and resolidification owing to the laser-peening, thereby increasing the fatigue strength of the opening peripheral zone.