The invention relates to a stainless steel. The stainless steel consists of in weight % (wt. %): TABLE-US-00001 C 0.32-0.50 Si 0.1-1.0 Mn 0.1-0.8 Cr11-14 Mo 1.8-2.6 V 0.35-0.70 N 0.05-0.19 optional elements, balance Fe and impurities.

The present invention relates to a method for manufacturing a high strength and high toughness steel material which is mainly used at an extremely low temperature and used in various parts of ships for LNG transport and LNG fuel vehicles.

Provided according to a preferable aspect of the present invention are a low-temperature steel material having excellent toughness in a welding portion thereof and a manufacturing method therefor, the low-temperature steel material comprising, by weight %, 0.02-0.06% of C, 6.0-7.5% of Ni, 0.4-1.0% of Mn, 0.02-0.15% of Si, 0.02-0.3% of Mo, 0.02-0.3% of Cr, 50 ppm or less of P, 10 ppm or less of S, 0.005-0.015% of Ti, 60 ppm or less of N, with a Ti/N weight % ratio of 2.5 of 4, and the balance of iron (Fe) and other inevitable impurities; and having: an effective grain size of 50 micrometers or less, with a boundary angle found to be 15 degrees or greater as measured by EBSD in an area of a fusion line (FL)-FL+1 mm in a weld heat-affected zone of a weld portion welded at a heat input of 5-50 kJ/cm; and an impact toughness of 70 J or higher at −196° C. as measured in an area of fusion line (FL)-FL+1 mm.

A blank material is formed from a steel sheet, a first quenching of the blank material is performed, and a second quenching of the blank material is performed after the first quenching. When the first quenching is performed, the blank material is heated to a first temperature of not lower than (Ac3 point—50)° C. nor higher than 1200° C. at an average heating rate of 2° C./sec or more, and the blank material is cooled from the first temperature to a second temperature of 250° C. or lower. When the second quenching is performed, the blank material is heated from the second temperature to a third temperature of not lower than (Ac3 point—50)° C. nor higher than 1200° C. at an average heating rate of 2° C./sec or more, and the blank material is cooled from the third temperature to a fourth temperature of 250° C. or lower. Forming of the blank material is performed in the first quenching or the second quenching or both of the above.

Thermally configurable structural elements (e.g., aircraft components such as an aircraft winglet spar) capable of assuming at least first and second structural configurations are provided whereby the structural element includes an integral actuation mechanism may be formed of sintered shape memory alloy (SMA) particles and sintered non-SMA particles formed by an additive layer manufacturing (ALM) process, such as 3D printing. The ALM process thereby provides by at least one thermally configurable region, and at least one non-thermally configurable region which is unitarily contiguous with the at least one thermally configurable region. The at least one thermally configurable region is capable of assuming at least first and second positional orientations in response to the presence or absence of a thermal input to thereby cause the structural element to assume the at least first and second structural configurations, respectively.

Provided herein is a high-strength seamless steel pipe, and a method for manufacturing same. A high-strength seamless steel pipe of the present invention has a yield strength of 758 MPa or more, and a K.sub.ILIMIT value of 23.0 MPa√m or more as an evaluation index of sulfide stress corrosion cracking resistance.

In the present invention, provided is a steel sheet having a predetermined chemical composition and a metallographic structure, in which A/B, which is a ratio of a length A of an interface between epitaxial ferrite and ferrite to a length B of an interface between the epitaxial ferrite and martensite in a cross section that is along a rolling direction and perpendicular to a surface of the steel sheet at a position of ¼ of a sheet thickness from the surface of the steel sheet is more than 1.5, a ratio of a major axis to a minor axis of the martensite is 5.0 or more, and a tensile strength is 980 MPa or more.

A method for controlling carbide network in a bearing steel wire rod by controlling cooling and rolling, comprises the following steps: rapidly rolling a bar to a wire rod and spinning it into a loose coil, controlling the rolling temperature at 780° C.-880° C.; and the spinning temperature at 750° C.-850° C.; carrying out on-line controlling cooling of continuous loose coils using EDC water bath austempering cooling process, controlling the cooling rate at 2.0° C./s-10° C./s, and controlling the final cooling temperature within 620-630° C.; after EDC water bath austempering cooling, using slow cooling under a cover, and the temperature is controlled to be 400° C.-500° C. when being removed out of the cover; after slow cooling, collecting coils, and cooling in air to the room temperature.

A seamless steel pipe of the present invention is a seamless steel pipe having a composition including, in mass %, C: 0.01 to 0.12%, Si: 0.01 to 0.8%, Mn: 0.10 to 2.00%, P: 0.050% or less, S: 0.040% or less, Al: 0.010 to 0.100%, Cu: 0.03 to 0.80%, Ni: 0.01 to 0.50%, Mo: 0.01 to 0.20%, Sb: 0.002 to 0.50%, Cr: 0.004% or less, W: 0.002% or less, and the balance Fe and incidental impurities, and a structure including a ferrite phase having an area percentage of 50 to 65%, a pearlite phase having an area percentage of 2% or less, and one or both of a bainite phase and a martensitic phase representing the remainder, the seamless steel pipe having a yield strength of 230 MPa or more, and a tensile strength of 380 MPa or more.

Methods for improving a toughness and a strength of a stainless steel material are described herein. For example, a high strength stainless steel material can comprise at least 11 wt. % Cr, between 0.01 wt. % and 1.0 wt. % Ni, more 0 wt. % Mo, more than 0 wt. % W, more than 0 wt. % Ti, more than 0 wt. % Nb, and more than 0 wt. % V. In some examples, the high strength stainless steel material can be heat treated with at least one quench treatment and at least one tempering heat treatment. In some examples, the high strength stainless steel material can comprise between 0.01 wt. % and 0.5 wt. % Ni, no more than 0.25 wt. % Mo, no more than 0.1 wt. % W, no more than 0.1 wt. % Ti, no more than 0.1 wt. % Nb, and no more than 0.1 wt. % V.