A high strength steel sheet having excellent surface quality and formability with a tensile strength of 980 MPa or more and a TS-El balance of 30000 MPa % or more is provided. A high strength steel sheet comprises: a chemical composition containing C: 0.08% to 0.30%, Si: 2.0% or less, Mn: more than 3.0% and 10.0% or less, P: 0.05% or less, S: 0.01% or less, Al: 1.5% or less, Ti: 0.010% to 0.300%, and N: 0.0020% to 0.0100% in a range satisfying 1.1(Ti+Mn.sup.1/2/400)/(0.01+5N)6.0; and a microstructure including a retained austenite phase and a ferrite phase, wherein a ratio Mn/Mn of an average Mn concentration (Mn) of the retained austenite phase to an average Mn concentration (Mn) of the ferrite phase is 1.5 or more.

A high strength steel sheet having excellent surface quality and formability with a tensile strength of 980 MPa or more and a TS-El balance of 30000 MPa % or more is provided. A high strength steel sheet comprises: a chemical composition containing C: 0.08% to 0.30%, Si: 2.0% or less, Mn: more than 3.0% and 10.0% or less, P: 0.05% or less, S: 0.01% or less, Al: 1.5% or less, Ti: 0.010% to 0.300%, and N: 0.0020% to 0.0100% in a range satisfying 1.1(Ti+Mn.sup.1/2/400)/(0.01+5N)6.0; and a microstructure including a retained austenite phase and a ferrite phase, wherein a ratio Mn/Mn of an average Mn concentration (Mn) of the retained austenite phase to an average Mn concentration (Mn) of the ferrite phase is 1.5 or more.

A funnel shaped mold for casting slabs of steel which is configured to be cooled by a fine spray of a cooling liquid on the outside of the mold.

A method of heat transfer between a metallic or non-metallic item and a heat transfer fluid is provided. The method includes a fluid medium and nanoparticles. A thickness/lateral size ratio of the nanoparticles is below 0.00044. The nanoparticles do not include carbon nanotubes.

Described herein are thin metal strips having hot rolled exterior side surfaces characterized as being primarily or substantially free of all prior austenite grain boundaries, or at least primarily or substantially free of all prior austenite grain boundaries, and including elongated surface structure. As a result, because the prior austenite grain boundaries are not primarily or substantially present, all such prior austenite grain boundaries are not susceptible to grain boundary etching due to acid etching or pickling. In particular examples, the thin metal strips undergo hot rolling performed with a coefficient of friction equal to or greater than 0.20 with or without use of lubrication.

A method for operating a casting/rolling system and to a corresponding system for casting and rolling an endless strand material. The casting/rolling system comprises a strand casting machine and a rolling train arranged downstream of the strand casting machine. The method has the following step: controlling the drive for the rollers of the first roller frame of the rolling train by means of a drive control in response to a target value specification of the pass sequence model. Furthermore, the drive of the at least one strand guiding roller is controlled by a strand guiding roller drive control in response to a target value specification of the strand casting machine drive model.

A method of heat transfer between a metallic or non-metallic item and a heat transfer fluid including a fluid medium, hydrophobic nanoparticles having a lateral size between 26 and 50 m and a dispersing agent is provided. The nanoparticles concentration/dispersing agent concentration ratio in weight is between 3 and 18 and the nanoparticles do not include carbon nanotubes. A heat transfer fluid is also provided.

A method of heat transfer between a metallic or non-metallic item and a heat transfer fluid including a fluid medium, hydrophobic nanoparticles having a lateral size between 26 and 50 m and a dispersing agent is provided. The nanoparticles concentration/dispersing agent concentration ratio in weight is between 3 and 18 and the nanoparticles do not include carbon nanotubes. A heat transfer fluid is also provided.

Described herein are thin metal strips having hot rolled exterior side surfaces characterized as being primarily or substantially free of all prior austenite grain boundaries, or at least primarily or substantially free of all prior austenite grain boundaries, and including elongated surface structure. As a result, because the prior austenite grain boundaries are not primarily or substantially present, all such prior austenite grain boundaries are not susceptible to grain boundary etching due to acid etching or pickling. In particular examples, the thin metal strips undergo hot rolling performed with a coefficient of friction equal to or greater than 0.20 with or without use of lubrication.

A spray apparatus for cooling a metal strand in a continuous casting machine, wherein at least one multiple-nozzle head and at least one switching valve are provided, wherein the multiple-nozzle head has at least a first and a second nozzle, wherein the switching valve is arranged upstream of the multiple-nozzle head, and wherein the switching valve is flow-connected to all the second nozzles in the multiple-nozzle head, in order to enable or to shut off a supply of spray liquid to all the second nozzles.