An NPR non-magnetic steel material for rock bolt and a production method thereof are disclosed. The NPR non-magnetic steel material for rock bolt has a composition, in weight percent, consisting of: C: 0.4-0.7%, MN: 15-20%, Cr: 1-18%, Si: 0.3-3%, Ca: 0.05-0.15%, Cu: ≤0.03%, Ni: ≤0.02%, S: ≤0.001%, P: ≤0.001%, and the rest being Fe and unavoidable impurity elements. The NPR non-magnetic steel material for rock bolt and the production method thereof effectively solve the problems of steel materials for rock bolt in the prior art such as strong magnetism, low tensile strength and low effective elongation. The NPR non-magnetic steel material for rock bolt has a fully-austenitized structure and is non-magnetic, its yield strength is adjustable in the range of 600-1000 MPa, and its elongation is adjustable in the range of 20-60%.

A shaft furnace, in particular a blast furnace, includes a metal jacket defining the furnace outer wall and a protective layer protecting the inner surface of the outer wall. At least one condition monitoring probe is arranged inside within the protective layer to monitor the latter. The condition monitoring probe is connected to a wireless module arranged outside the outer wall to transmit condition monitoring data. The wireless module is located inside a casing mounted to the outer surface of the metal jacket. The condition monitoring probe includes one or more conductive loops positioned at predetermined depths below the front face of the cooling plate body, or of the refractory lining, so that wear of the body, resp. refractory, can be detected by a change of an electrical characteristic of the loop(s) due to abrasion.

A high strength member according to the present invention is the high strength member having a bending ridge line portion formed from a steel sheet, the member having a tensile strength of 1470 MPa or higher, a residual stress of 300 MPa or lower in an end surface of the bending ridge line portion, and a Vickers hardness (HV) of 200 or higher and 450 or lower in the end surface of the bending ridge line portion.

A high-strength steel sheet includes a predetermined chemical composition, a microstructure contains, by volume percentage, 80% or more of tempered martensite, and a remainder consists of ferrite and bainite, the microstructure contains 5.0×10.sup.11 pieces/mm.sup.3 or more of, per unit volume, precipitate containing Ti and having an equivalent circle diameter of 5.0 nm or less, Hvs/Hvc which is a ratio of an average hardness Hvs at a position of a depth of 20 μm from a surface to an average hardness Hvc at a position of 0.20 to 0.50 mm from the surface is 0.85 or more, and the tensile strength is 1,180 MPa or more.

A device for strengthening a straight pipe, including a first positioning mold, a second positioning mold, a split mold, a rounding mold, a first cavity and a second cavity. A method for strengthening a straight pipe is further provided. The split mold is adjusted to position the pipe. The pipe is inserted into the first and second positioning molds. First and second sealing rings are arranged in an inner cavity of the pipe. Hydraulic oil is injected into the first cavity to expand the pipe to perform an expanding deformation. When the hydraulic oil is unloaded, the split mold moves towards an axis of the first positioning mold to perform a reducing deformation. After the expanding and reducing deformations, the pipe is transported into the rounding mold, and hydraulic oil is injected into the second cavity to expand the pipe to perform the rounding.

A tube assembly includes at least first and second tubes configured for coupling at respective ends. The first and second tubes each include a base material, and a weld interface at the respective end. The weld interface is proximate to an inner diameter and an outer diameter of the first and second tubes, and includes a weld interface segment extending therebetween. A work hardened weld assembly couples the base material of each of the first and second tubes. The work hardened weld assembly includes a weld fusion zone between the weld interfaces of the first and second tubes and the weld interface segments of the first and second tubes. The weld fusion zone is work hardened and at least the weld interface segments of the first and second tubes are work hardened between the work hardened weld fusion zone and the base material of the first and second tubes.

A device for strengthening a straight pipe, including a first positioning mold, a second positioning mold, a split mold, a rounding mold, a first cavity and a second cavity. A method for strengthening a straight pipe is further provided. The split mold is adjusted to position the pipe. The pipe is inserted into the first and second positioning molds. First and second sealing rings are arranged in an inner cavity of the pipe. Hydraulic oil is injected into the first cavity to expand the pipe to perform an expanding deformation. When the hydraulic oil is unloaded, the split mold moves towards an axis of the first positioning mold to perform a reducing deformation. After the expanding and reducing deformations, the pipe is transported into the rounding mold, and hydraulic oil is injected into the second cavity to expand the pipe to perform the rounding.

An NPR non-magnetic steel material for rock bolt and a production method thereof are disclosed. The NPR non-magnetic steel material for rock bolt has a composition, in weight percent, consisting of: C: 0.4-0.7%, Mn: 15-20%, Cr: 1-18%, Si: 0.3-3%, Ca: 0.05-0.15%, Cu: ≤0.03%, Ni: ≤0.02%, S: ≤0.001%, P: ≤0.001%, and the rest being Fe and unavoidable impurity elements. The NPR non-magnetic steel material for rock bolt and the production method thereof effectively solve the problems of steel materials for rock bolt in the prior art such as strong magnetism, low tensile strength and low effective elongation. The NPR non-magnetic steel material for rock bolt has a fully-austenitized structure and is non-magnetic, its yield strength is adjustable in the range of 600-1000 MPa, and its elongation is adjustable in the range of 20-60%.

A drive shaft includes a first annular wall and a second annular wall joined together via a friction-welded portion. The first annular wall and the second annular wall have outer diameters of 30 to 50 mm and wall thicknesses of 3 to 5 mm. A burr created at the friction-welded portion has a connection radius of greater than or equal to 0.5 mm, a base radius of greater than or equal to 0.5 mm, a burr base angle of less than or equal to 40°, and a burr slope length of 0.2 to 5 mm.

A tube assembly includes at least first and second tubes configured for coupling at respective ends. The first and second tubes each include a base material, and a weld interface at the respective end. The weld interface is proximate to an inner diameter and an outer diameter of the first and second tubes, and includes a weld interface segment extending therebetween. A work hardened weld assembly couples the base material of each of the first and second tubes. The work hardened weld assembly includes a weld fusion zone between the weld interfaces of the first and second tubes and the weld interface segments of the first and second tubes. The weld fusion zone is work hardened and at least the weld interface segments of the first and second tubes are work hardened between the work hardened weld fusion zone and the base material of the first and second tubes.