Abstract: Provided is a laser welding method of materials having different thicknesses that can achieve excellent weld strength regardless of the thickness of a thick plate, and a welded member having different thicknesses.

Abstract: A welded portion shape of a cross-section perpendicular to the shaped steel longitudinal direction is set to satisfy a>0 mm, b>0 mm, c?0.14Tw, d?0 mm, e?0 mm, a+d?2 mm and b+e?2 mm; where a is a front melting width of the web material (on the laser beam irradiation side), b is a rear melting width of the web material (on the laser beam non-irradiation side), c is a maximum weld penetration depth, in a plate pressure direction, into the flange material, d is a front melting width of the flange material (on the laser beam irradiation side), e is a rear melting width of the flange material (on the laser beam non-irradiation side), and Tw is the plate thickness of the web material.

Abstract: A sleeve 10 for introduction of a pressurized fluid, which is attached to a rockbolt main body 1, comprises a cylindrical projecting part 11 of a large diameter and a bearing-plate-holding part 12 of a diameter smaller than an aperture of a bearing plate 6. The projecting part 11 and the bearing-plate-holding part 12 preferably has the same inner diameter. When the rockbolt main body 1 is embedded in a bedrock or ground, the bearing plate 6 locates on an edge of a rockbolt-setting hole of the bedrock or ground, and the bearing-plate-holding part 12 extends through the bearing plate 6 into the rockbolt-setting hole. Since the projecting part 11 and the bearing plate 6 are disposed on a sprayed concrete layer, a projection height of the rockbolt is remarkably decreased. Consequently, lining concrete 8 is applied onto the sprayed concrete layer with ease, and the bedrock or ground is reinforced with high reliability.

Abstract: A high-strength steel pipe rockbolt has an expansive rockbolt main body prepared by processing a high-strength steel sheet of 1.8-2.3 mm in thickness with a tensile strength of 490-640 N/mm2 and an elongation of 20% or more into a welded pipe and roll-forming the welded pipe into a shaped pipe having one or more concavities extending along an axial direction. Use of the high-strength steel sheet ensures sufficient strength of the shaped pipe regardless of a decrease in thickness. The thin welded pipe is also advantageous in resistance to cracking caused by accumulation of strains introduced during roll-forming, swaging both ends of the welded pipe and hydraulic expansion. Moreover, expansive deformation of the shaped pipe is initiated by injection of a pressurized fluid at a low pressure, so that the expansive deformation is completed in a short time period with an improved working efficiency.

Abstract: A lock bolt of a high strength steel pipe, wherein an expansion type lock bolt body is formed of a deformed pipe manufactured by using, as a raw material, a high tension steel plate having a tensile strength of 490 to 640 N/mm2, an elongation of 20% or more, and a plate thickness of 1.8 to 2.3 mm and having a single or a plurality of recessed parts extending in the axial direction of the deformed pipe. Since the high tension steel plate is used in the lock bolt, sufficient strength can be secured for the lock bolt though the steel plate is thin, and cracking due to stains introduced in a molding process, a both end shrinkage process, and a pressurizing/expanding process can be suppressed. Since an expansion start pressure when a pressurized fluid is press-fitted and inflated is also low, a time in which the expansion/deformation is completed can be shortened and workability can also be improved.

Abstract: A sleeve 10 for introduction of a pressurized fluid, which is attached to a rockbolt main body 1, comprises a cylindrical projecting part 11 of a large diameter and a bearing-plate-holding part 12 of a diameter smaller than an aperture of a bearing plate 6. The projecting part 11 and the bearing-plate-holding part 12 preferably has the same inner diameter. When the rockbolt main body 1 is embedded in a bedrock or ground, the bearing plate 6 locates on an edge of a rockbolt-setting hole of the bedrock or ground, and the bearing-plate-holding part 12 extends through the bearing plate 6 into the rockbolt-setting hole. Since the projecting part 11 and the bearing plate 6 are disposed on a sprayed concrete layer, a projection height of the rockbolt is remarkably decreased. Consequently, lining concrete 8 is applied onto the sprayed concrete layer with ease, and the bedrock or ground is reinforced with high reliability.

Abstract: In a method for making thin-walled metal pipes, application of a pre-deformation to a metal sheet by plastic bending longitudinally perpendicular thereto, and forming the metal sheet into a pipelike shape by use of the widthwise curvature resulting from residual stress of the metal sheet receiving such plastic bending, when its lengthwise curvature is reduced to zero, the metal sheet being joined together at its junction.