5results about How to "Reduce grain size" patented technology

This hot-rolled steel sheet has a predetermined chemical composition, in which, when a region of 1 / 8 to 3 / 8 of a sheet thickness in a sheet thickness direction from a surface is defined as a 1 / 4 depth position, a microstructure at the 1 / 4 depth position includes, by area fraction, retained austenite: less than 3.0%, ferrite: less than 30.0%, and pearlite: less than 5.0%, at the 1 / 4 depth position, an average number density of Ti-based carbides having a longest diameter of 15 nm or more is 1.0 × 104 / mm2 or more, and an average grain size dq is 15.0 µm or less, and a tensile strength is 980 MPa or more.

A method for manufacturing a high-strength steel sheet having a tensile strength of more than 1100 MPa and a yield strength of more than 700 MPa, a uniform elongation UE of at least 8.0% and a total elongation of at least 10%, made of a steel containing in percent by weight: 0.1% ≤ C ≤ 0.25%, 4.5% ≤ Mn ≤ 10%, 1% ≤ Si ≤ 3%, 0.03% ≤ Al ≤ 2.5% , the remainder being Fe and impurities resulting from the smelting, the composition being such that CMnIndex = Cx(1 + Mn / 3.5) ≤ 0.6, the method comprising the steps of annealing a rolled sheet made of said steel by soaking it at an annealing temperature TA higher than the Ac1 transformation point of the steel but less than 1000°C, cooling the annealed sheet to a quenching temperature QT between 190°C and 80°C at a cooling speed sufficient to obtain a structure just after cooling containing martensite and retained austenite, maintaining the steel sheet at an overaging temperature PT between 350°C and 500°C for an overaging time Pt of more than 5 s cooling the sheet down to the ambient temperature. Sheet obtained.

The invention relates to a method for welding dissimilar metal through electron beam composite ultrasonic vibration, in particular to an electron beam composite ultrasonic vibration welding method for Ti-6Al-4V and T2 pure copper. The method comprises the following specific steps: firstly, carrying out pre-welding pretreatment on a weldment; then the workpiece and the three-axis sliding rail are placed into a welding chamber; then, an ultrasonic device is assembled, and the distance between an ultrasonic rolling head ball and an electron beam and the pressure between the ultrasonic rolling head ball and the to-be-welded workpiece are adjusted; and then ultrasonic parameters and electron beam welding parameters are set. And finally, the welding chamber is vacuumized, double-electron-beam welding is conducted, the front electron beam is located on the copper side, the rear electron beam is located on the titanium side, and the two welding seams are adjacent but not overlapped. The welding method has the welding characteristics that aiming at the problems of coarse weld grains, larger post-welding residual stress and the like in the electron beam welding dissimilar metal process, an ultrasonic rolling head ball is adopted for vibrating a welding material, and sound streaming and cavitation effects are generated on a welding pool, so that the grains are refined, air holes are discharged, the welding residual stress is eliminated, and the mechanical property of a welding joint is further improved.

This invention provides a method for producing ML40Cr hot-rolled wire rod, comprising the following steps: (a) heating the billet; (b) rough rolling, pre-finish rolling, and finish rolling the product from step (a) to form coils into wire; (c) controlling the temperature of the wire using a STEM air-cooled line and closing the insulation cover for heat preservation; (d) coiling the product from step (c) and passing it through an insulation corridor for further heat preservation, wherein the temperature of the coiled product entering the insulation corridor is controlled at 745–755°C, the temperature after passing through the insulation corridor is controlled at 200–300°C, and the time spent passing through the insulation corridor is controlled at 100–105 min; (e) finishing the ends of the product after passing through the insulation corridor and then packaging it. Reducing the pearlite clusters and grains in the product's metallographic structure helps improve its uniformity and thus enhances the product's performance.