Abstract: This wire for gas-shielded arc welding is a wire for joining a plurality of thin steel sheets by gas-shielded arc welding, the wire including, in mass %, with respect to a total mass of the wire: C: 0.06 to 0.15%; Si: more than 0 to 0.18%; Mn: 0.3 to 2.2%; Ti: 0.06 to 0.30%; Al: 0.001 to 0.30%; and B: 0.0030 to 0.0100%, in which Si, Mn, Ti, and Al satisfy Expressions (1) and (2). Si×Mn?0.30??Expression (1) (Si+Mn/5)/(Ti+Al)?3.

Abstract: A plasma torch comprises a cascade between a cathode and an anode. The cascade is an inter-electrode insert. An interior of the cascade is shaped so that a diameter of the interior expands in series in a plurality of steps from a side of the cathode to a side of the anode. As a result of the cascade being provided, the output power of the plasma torch is obtained not by an increase in the electric current but by an increase in the arc electric voltage. Therefore, the lifespan of each of the electrodes, i.e., the cathode and the anode, becomes remarkably longer. In addition, since a quasi laminar flow of the plasma is generated in the interior of the cascade, a fluctuation in the output power of the plasma jet is reduced. Thus, it is possible to lower the driving and operating costs.

Abstract: An impact treatment method for improving fatigue characteristics of a welded joint comprising pressing an impact pin against the surface of a base metal material near a toe of a weld bead and making it move relatively to the weld line direction to apply hammer peening treatment or ultrasonic impact treatment, characterized by using as the impact pin an impact pin having a tip curvature radius of ½ or less of a thickness of the metal material and between 2 to 10 mm and, on a surface of a base metal material up to a range where a distance from the toe of the weld bead to the center of the impact treatment position is within 2.5 times the tip curvature radius of the impact pin and where the impact pin does not contact the weld metal during impact treatment, applying hammer peening or ultrasonic impact treatment so as to cause by the impact pin residual plastic deformation where an impact dent has a groove depth of 0.

Abstract: A plasma torch comprises a cascade between a cathode and an anode. The cascade is an inter-electrode insert. An interior of the cascade is shaped so that a diameter of the interior expands in series in a plurality of steps from a side of the cathode to a side of the anode. As a result of the cascade being provided, the output power of the plasma torch is obtained not by an increase in the electric current but by an increase in the arc electric voltage. Therefore, the lifespan of each of the electrodes, i.e., the cathode and the anode, becomes remarkably longer. In addition, since a quasi laminar flow of the plasma is generated in the interior of the cascade, a fluctuation in the output power of the plasma jet is reduced. Thus, it is possible to lower the driving and operating costs.

Abstract: The present invention provides a boom and arm member of a construction machine excellent in weld zone fatigue strength and a method of improvement of its fatigue strength, that is, a boom and arm member of a construction machine superior in weld zone fatigue strength, the boom and arm member of a construction machine characterized in that toes of full penetrated weld zones of the boom and arm member have vibration strike marks, and a method of improvement of its fatigue strength. Preferably, the residual stress of the bottom surface of the vibration strike marks is a 10 MPa or higher compressive residual stress.

Abstract: An effective volume Vep of a member is calculated with a stress correction amount ?corr added to an effective stress (stress amplitude) ?ip at each position of the member so that a fatigue strength of the member varying corresponding to an average stress varying depending on the position of the member is apparently constant at a value when the average stress on the member is 0 (zero) irrespective of the position of the member, and a cumulative fracture probability Pfp due to fatigue of the member is derived using the effective volume Vep of the member.

Abstract: An impact treatment method for improving fatigue characteristics of a welded joint comprising pressing an impact pin against the surface of a base metal material near a toe of a weld bead and making it move relatively to the weld line direction to apply hammer peening treatment or ultrasonic impact treatment, characterized by using as the impact pin an impact pin having a tip curvature radius of ½ or less of a thickness of the metal material and between 2 to 10 mm and, on a surface of a base metal material up to a range where a distance from the toe of the weld bead to the center of the impact treatment position is within 2.5 times the tip curvature radius of the impact pin and where the impact pin does not contact the weld metal during impact treatment, applying hammer peening or ultrasonic impact treatment so as to cause by the impact pin residual plastic deformation where an impact dent has a groove depth of 0.

Abstract: A method of production of a metallic product with a nanocrystallized surface layer comprising subjecting a surface layer of a metallic product to ultrasonic impact treatment by one or more ultrasonic indenters vibrating in a plurality of directions, then subjecting the surface layer subjected to the ultrasonic impact treatment to heat treatment at a low temperature to cause precipitation of nanocrystals.

Abstract: A method of improvement of toughness of a heat affected zone in a multi-layer welded joint, a fillet welded joint, and a one-pass or several-pass large heat input welded joint of a steel plate is provided, that is, a method of improvement of toughness of a heat affected zone in a welded joint of a steel plate characterized subjecting a surface of a heat affected zone formed by a last pass of a multi-layer welded joint of a steel plate to impacts by an ultrasonic vibration tool or shot peening by ultrasonic vibration steel balls to thereby make an average of longitudinal axis of crystal grains up to a depth of 2 mm or more from the surface of the steel plate in the microstructure adjacent to a fusion line (FL) of a weld metal and a steel plate matrix in said heat affected zone formed by the last pass the equivalent of the crystal grain size of the steel plate matrix before the welding at a depth of ¼ of a thickness t from the surface of the steel plate.

Abstract: The present invention provides a boom and arm member of a construction machine excellent in weld zone fatigue strength and a method of improvement of its fatigue strength, that is, a boom and arm member of a construction machine superior in weld zone fatigue strength, the boom and arm member of a construction machine characterized in that toes of full penetrated weld zones of the boom and arm member have vibration strike marks, and a method of improvement of its fatigue strength. Preferably, the residual stress of the bottom surface of the vibration strike marks is a 10 MPa or higher compressive residual stress.

Abstract: Ceramic plates for side dams of twin-drum continuous strip casters comprising a REAG phase of 10 to 90 vol. %, a Sialon phase of 5 to 50 vol. %, a BN phase of 5 to 50 vol. % and an amorphous phase of over 0 to 20 vol. %, with the REAG phase comprising at least one rare-earth aluminum garnet phase selected from YAG, ErAG, YbAG and DyAG phases and the Sialon phase having a chemical formula, Si6?zAlzOzN8?z, wherein Z is between 0.05 and 1.9.

Abstract: Ceramic plates for side dams of twin-drum continuous strip casters comprising a REAG phase of 10 to 90 vol. %, a Sialon phase of 5 to 50 vol. %, a BN phase of 5 to 50 vol. % and an amorphous phase of over 0 to 20 vol. %, with the REAG phase comprising at least one rare-earth aluminum garnet phase selected from YAG, ErAG, YbAG and DyAG phases and the Sialon phase having a chemical formula, Si6-zAlzOzN8-z, wherein Z is between 0.05 and 1.9.

Abstract: A method of improvement of toughness of a heat affected zone in a multi-layer welded joint, a fillet welded joint, and a one-pass or several-pass large heat input welded joint of a steel plate is provided, that is, a method of improvement of toughness of a heat affected zone in a welded joint of a steel plate characterized subjecting a surface of a heat affected zone formed by a last pass of a multi-layer welded joint of a steel plate to impacts by an ultrasonic vibration tool or shot peening by ultrasonic vibration steel balls to thereby make an average of longitudinal axis of crystal grains up to a depth of 2 mm or more from the surface of the steel plate in the microstructure adjacent to a fusion line (FL) of a weld metal and a steel plate matrix in said heat affected zone formed by the last pass the equivalent of the crystal grain size of the steel plate matrix before the welding at a depth of ¼ of a thickness t from the surface of the steel plate.

Abstract: This invention provides a black low thermal expansion high specific rigidity ceramic sintered body having a black tone, manifesting very small thermal expansion at room temperature and abounding in rigidity and specific rigidity, and a method for the production thereof. The black low thermal expansion high specific rigidity ceramic sintered body is characterized by having a chemical composition comprising 8.0–17.2 mass % of MgO, 22.0–38.0 mass % of Al2O3, 49.5–65.0 mass % of SiO2, a total of 0.1–2 mass % of one or more transition elements as reduced to oxides, and 0–2.5 mass % of Li2O, and having the mass ratios satisfy the relationships of (SiO2?8×Li2O)/MgO?3.0 and (SiO2?8×Li2O)/Al2O3?1.2. The method for the production of a black low thermal expansion high specific rigidity ceramic sintered body of this invention is characterized by forming the sintered body in an atmosphere of a non-oxidizing gas at a temperature in the range of 1200–1500° C.

Abstract: A method of production of a metallic product with a nanocrystallized surface layer comprising subjecting a surface layer of a metallic product to ultrasonic impact treatment by one or more ultrasonic indenters vibrating in a plurality of directions, then subjecting the surface layer subjected to the ultrasonic impact treatment to heat treatment at a low temperature to cause precipitation of nanocrystals.

Abstract: An electroconductive low thermal expansion ceramic sintered body is disclosed which containing a ?-eucryptite phase in a quantity of not less than 75 vol. % and not more than 99 vol. % and having an absolute value of thermal expansion coefficient of not more than 1.0×10?7/K at a temperature of 0° C. to 50° C., a volumetric specific resistance of not more than 1.0×107 ?·cm, and a specific rigidity of not less than 40 GPa/g/cm3.

Abstract: An electroconductive low thermal expansion ceramic sintered body is disclosed which containing a &bgr;-eucryptite phase in a quantity of not less than 75 vol. % and not more than 99 vol. % and having an absolute value of thermal expansion coefficient of not more than 1.0×10−7/K at a temperature of 0° C. to 50° C., a volumetric specific resistance of not more than 1.0×107 &OHgr;·cm, and a specific rigidity of not less than 40 GPa/g/cm3.

Abstract: The low thermal expansion and high rigidity ceramic sintered body of this invention is characterized by assuming as a crystal structure a hexagonal close-packed structure and substantially comprising solid solution crystal grains represented by the formula: MgaLibFecAldSieOf (wherein a is in the range of 1.8 to 1.9, b is in the range of 0.1 to 0.3, c is in the range of 0 to 0.2, d is in the range of 3.9 to 4.1, e is in the range of 6.0 to 7.0, and f is in the range of 19 to 23). It is further characterized by the solid solution crystal grains having lattice constants in the ranges, a0 in the range of 9.774 to 9.804 Å and c0 in the range of 9.286 to 9.330 Å, the relative density of the sintered body being of not less than 98%.

Abstract: An oxide superconducting material includes a REBa2Cu3O7−x phase (RE designating one or a combination of two or more rare earth elements including Y), particles composed of Ce, Ba, Cu and O dispersed therein, and RE2BaCuO5 or RE4Ba2Cu2O10 dispersed therein. A method is provided for producing the superconducting material from a mixed powder obtained by adding a Ce—Ba—Cu—O system additive to a starting material powder containing RE, Ba, Cu and O.

Abstract: A fixture capable of a brittle pre-crack introduction of prescribed shape and size in a ceramic specimen with high reproducibility comprises an anvil provided on the upper side thereof with a central groove perpendicularly intersecting a specimen to be mounted thereon for pre-crack introduction and a groove for positioning the specimen and a platelike pusher possessing a smooth and flat lower surface. To ensure stability of the brittle pre-crack introduction, the positioning groove in the anvil is so formed as to rise rectangularly in an equal length on either side of the central groove and the overall length of the positioning groove, i.e. the sum of the lengths of the raised portions plus the width of the central groove, is kept from exceeding the length of the specimen. To enhance the results of the introduction, the lower surface of the pusher is finished with roughness of not more than 0.8S and flatness of not more than 0.01 mm.