STEEL SHEET HAVING EXCELLENT BENDING WORKABILITY AND DRILLING RESISTANCE AND BURIED TUBE PROTECTIVE STRUCTURE USING THE STEEL SHEET

• Main Authors: KUMAGAI TATSUYA, KIBE MASAOMI, MURAOKA HIROHIDE, OGUCHI NORITAKE
• Format: Patent
• Language: English
• Published: 13.09.2007
• Subjects: ALLOYS; BLASTING; CHEMISTRY; EARTH DRILLING; ENGINEERING ELEMENTS AND UNITS; FERROUS OR NON-FERROUS ALLOYS; FIXED CONSTRUCTIONS; GALLERIES; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVEFUNCTIONING OF MACHINES OR INSTALLATIONS; HEATING; JOINTS OR FITTINGS FOR PIPES; LARGE UNDERGROUND CHAMBERS; LIGHTING; MEANS FOR THERMAL INSULATION IN GENERAL; MECHANICAL ENGINEERING; METALLURGY; MINING; PIPES; SHAFTS; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; THERMAL INSULATION IN GENERAL; TREATMENT OF ALLOYS OR NON-FERROUS METALS; TUNNELS; WEAPONS

PROBLEM TO BE SOLVED: To provide a protection method where a construction for protecting a buried tube from the damage from the upper face and side faces is simple and economical to non-excavation pipeline installation technique in a buried tube construction, particularly, to a drilling technique using a drill bit clad with a super hard material, and to provide an inexpensive steel sheet having excellent bending workability and drilling resistance used therefor. SOLUTION: The buried tube protective structure is characterized in that steel sheets each having excellent bending workability and drilling resistance which has a composition comprising, by mass, 0.12 to 0.18% C, 0.05 to 0.60% S, ≤2.25% Mn, Mn/C>8, ≤0.008% S and 0.005 to 0.1% Al, and the balance Fe with inevitable impurities, has a structure essentially consisting of martensite or a mixed structure of martensite and lower bainite, in which the total structural fraction of the martensite and the lower bainite is ≥85% and the structural fraction of ferrite is ≤10%, and has the average Brinell hardness of 360 to 450; wherein the steel sheets which have been subjected to bending to a gate shape are arranged at fixed intervals from a buried tube so as to cover the upper face and both the side faces of the buried tube. COPYRIGHT: (C)2007,JPO&INPIT