There is provided a duplex stainless steel tube including a chemical composition consisting of, in mass %, C: 0.008 to 0.030%, Si: 0.10 to 0.70%, Mn: 0.80 to 2.60%, P: 0.030% or less, S: 0.0001 to 0.0050%, O: 0.0004 to 0.0150%, Sn: 0.0001% or more to less than 0.0100%, Cu: 0.10 to 2.50%, Ni: more than 2.50 to 5.50% or less, Cr: 21.5 to 25.5%, Mo: 0.10 to 0.50%, N: 0.050 to 0.200%, Al: 0.200% or less, and optional elements, with the balance: Fe and impurities, wherein 4S+8O+Sn is 0.0040 to 0.0900, and 4S+Sn is 0.0180 or less.

The invention relates to a method and a device for strengthening the surface of workpieces, in particular of metal ones, by mechanical effects accompanying the impact of small projectiles or by mechanical effects accompanied by the impact of a shockwave induced by plasma created by electric evaporation of a metal foil. The device comprises a polymer strip with a metal foil on the surface of the side diverted from the surface of the workpiece in which foil bridges are formed to form projectiles, further comprising two electrodes and adjacent to the metal foil located on the polymer strip, wherein bridges are formed between the contact surface areas of the metal foil, and the electrodes and between which the plasma is formed, are mounted in a support body, through which flat conductors and are connected to a switch for switching large currents and high voltages with a high-voltage source. The polymer strip with the metal foil tightly abuts the support body with the electrodes and the electrodes and protrude above the upper surface of the support body to provide electric contact with the contact surface areas of the applied metal foil. The method of strengthening the surface of workpieces by means of the device according to the invention consists in that one cycle of strengthening the surface of workpieces involves the action of an electric current pulse supplied from a high voltage source after closing the switch by conductors to electrodes between which a high voltage is applied, thereby shorting the circuit on the metal foil at the location of the bridges to form a plasma expanding and by a compressive force acting on the polymer strip part of which hits as a projectile the surface of the workpiece. The plasma is generated by the electric current pulse, in addition to the expansion pressure, is also accelerated by the electromagnetic Lorentz force caused by the passage of electric current, through this plasma in the generated magnetic field.

A method of colorizing stainless steel strip involves the continuous surface treatment of stainless steel strip with aqueous suspensions of rare earth oxide nano or micro particles or aqueous rare earth nitrate solutions of nano or micro particles. The surface treatment can be applied by roll coating, spraying or other conventional application techniques. The coated strip is then continuously annealed. The surface treatment can provide a variety of colors. It also improves corrosion resistance of the processed stainless steel strip. Steel strip treated in this manner is suitable for a variety of applications in the building systems, automotive and appliance markets.

A method of colorizing stainless steel strip involves the continuous surface treatment of stainless steel strip with aqueous suspensions of rare earth oxide nano or micro particles or aqueous rare earth nitrate solutions of nano or micro particles. The surface treatment can be applied by roll coating, spraying or other conventional application techniques. The coated strip is then continuously annealed. The surface treatment can provide a variety of colors. It also improves corrosion resistance of the processed stainless steel strip. Steel strip treated in this manner is suitable for a variety of applications in the building systems, automotive and appliance markets.

An apparatus is provided, the apparatus comprising: (i) a diode-pumped solid-state laser oscillator configured to generate a pulsed laser beam having predefined beam characteristics corresponding to a current setting selection of a controller; and (ii) an amplifier configured to amplify an energy and modify a beam profile of the pulse laser beam. A beam detector is coupled to the generated beam to monitor a combination of: (i) a beam pulse width; (ii) a beam diameter; and (iii) an energy level, and generates an error signal to be sent back as a feedback signal to the controller. The controller configures the current source to output a correction current to tune the DPSSL oscillator, the wave plate, and the first polarizer to rotate a correction polarization angle and adjust the energy amplification or temporal profile to within a defined performance tolerance.

A method for peening an obstructed region of a metal assembly that is obstructed by an obstructing part of the metal assembly is provided. The method includes determining an optimal peening path for treating the obstructed region irrespective of the obstructing part; identifying a portion of the obstructing part within the optimal peening path; determining a section of the portion of the obstructing part that is removable without affecting a mechanical integrity and functionality of the obstructing part; removing, by machining, the section so as to create additional space along the optimal peening path; and peening the obstructed region, a path of the peening at least partially crossing through the additional space. A method for peening a nuclear reactor pressure vessel is also provided.

A method for peening an obstructed region of a metal assembly that is obstructed by an obstructing part of the metal assembly is provided. The method includes determining an optimal peening path for treating the obstructed region irrespective of the obstructing part; identifying a portion of the obstructing part within the optimal peening path; determining a section of the portion of the obstructing part that is removable without affecting a mechanical integrity and functionality of the obstructing part; removing, by machining, the section so as to create additional space along the optimal peening path; and peening the obstructed region, a path of the peening at least partially crossing through the additional space. A method for peening a nuclear reactor pressure vessel is also provided.

Surface material of a mold molding surface and surface treatment method. A molding surface of material including metal and in which the molding surface reaches 50° C. or higher during molding is subjected to rapid thermal processing by injecting a substantially spherical shot with a hardness equal to or greater than the surface hardness of the mold and a size of #220 (JIS R6001-1973) or smaller at an injection pressure of 0.2 MPa or more and bombarding the surface with the shot, causing the temperature to rise locally and instantaneously at a bombarded portion to refine the surface structure of the surface and to form numerous smooth arc-shaped indentations on the entire surface of the surface. Then, powder including titanium having size of #100 or smaller is injected at an injection pressure of 0.2 MPa or more to form a coating of titanium oxide on the surface of the surface.

Surface material of a mold molding surface and surface treatment method. A molding surface of material including metal and in which the molding surface reaches 50° C. or higher during molding is subjected to rapid thermal processing by injecting a substantially spherical shot with a hardness equal to or greater than the surface hardness of the mold and a size of #220 (JIS R6001-1973) or smaller at an injection pressure of 0.2 MPa or more and bombarding the surface with the shot, causing the temperature to rise locally and instantaneously at a bombarded portion to refine the surface structure of the surface and to form numerous smooth arc-shaped indentations on the entire surface of the surface. Then, powder including titanium having size of #100 or smaller is injected at an injection pressure of 0.2 MPa or more to form a coating of titanium oxide on the surface of the surface.

A valve spring which has an excellent fatigue limit is provided. A chemical composition of the valve spring according to the present embodiment contains, in mass %, C: 0.50 to 0.80%, Si: 1.20 to less than 2.50%, Mn: 0.25 to 1.00%, P: 0.020% or less. S: 0.020% or less: Cr: 0.40 to 1.90%, V: 0.05 to 0.60%, Ca: 0.0001 to 0.0050%, and N: 0.0100% or less, with the balance being Fe and impurities. In the valve spring, a number density of V-based precipitates having a maximum diameter ranging from 2 to 10 nm is 5000 to 80000 pieces/μm.sup.3, and a numerical proportion of Ca sulfides with respect to a total number of oxide-based inclusions and sulfide-based inclusions is 0.20% or less.