To provide a heat-treated steel excellent in both tensile strength and toughness.

A heat-treated steel contains 0.38 to 1.05% by mass of C, 0.0 to 1.0% by mass of Mn, 0.0 to 0.50% by mass of Cr, and 0.0 to 1.5% by mass of Si with the remainder being Fe and unavoidable impurities, wherein an average crystal grain size at a grain boundary setting angle of 15 is 10C+7 (m) or less (wherein, C represents a carbon content (%)).

The method for the heat treatment of a steel reinforcing element (F) for a tire comprises a transformation of the steel microstructure and in which the temperature of the reinforcing element (F) is reduced during the transformation of the steel microstructure by simultaneously extracting heat from the reinforcing element (F) and supplying heat to the reinforcing element (F).

The method for the heat treatment of a steel reinforcing element (F) for a tire comprises a transformation of the steel microstructure and in which the temperature of the reinforcing element (F) is reduced during the transformation of the steel microstructure by simultaneously extracting heat from the reinforcing element (F) and supplying heat to the reinforcing element (F).

A method for annealing a hot-rolled steel strip controls the annealing temperature with high accuracy to obtain excellent magnetic properties across the entire length of the steel strip. Specifically, the method used for an electrical steel sheet containing 1.6 to 5.0 mass % Si, using a continuous annealing line including heating, soaking and cooling zones in this order from the upstream side, the annealing line heating conditions are determined from slab temperature distribution information in the longitudinal direction during heating, or from information steel strip temperature distribution in the longitudinal direction during hot rolling. The heating conditions of the annealing line are determined by a rapid heating device on the upstream side of the soaking zone, arranging a thickness meter on the upstream side of the rapid heating device, and setting the heating temperature for the steel strip by the rapid heating device to achieve a target annealing temperature.

A furnace for performing a thermal treatment of a continuously moving metal strip includes: a hybrid wall lining facing inwardly of the furnace, the hybrid wall lining including a stack of polycrystalline fibre modules, and graphite lintels being fixed between or in the polycrystalline fibre modules; and electric heating elements provided inside the furnace along one or more vertical walls, and fixed on a side of the hybrid wall lining facing inwardly of the furnace. The polycrystalline fibre modules include fibres with at least 95% of Al2O3 so as to be compatible with a hydrogen protective atmosphere, a thickness of the polycrystalline fibre modules being between 200 and 500 mm. The electric heating elements are attached to the graphite lintels by a first anchoring system. The graphite lintels protect the electric heating elements against strip deviations by being cantilevered above the electric heating elements and protruding from the hybrid wall lining.

A furnace for performing a thermal treatment of a continuously moving metal strip includes: a hybrid wall lining facing inwardly of the furnace, the hybrid wall lining including a stack of polycrystalline fibre modules, and graphite lintels being fixed between or in the polycrystalline fibre modules; and electric heating elements provided inside the furnace along one or more vertical walls, and fixed on a side of the hybrid wall lining facing inwardly of the furnace. The polycrystalline fibre modules include fibres with at least 95% of Al2O3 so as to be compatible with a hydrogen protective atmosphere, a thickness of the polycrystalline fibre modules being between 200 and 500 mm. The electric heating elements are attached to the graphite lintels by a first anchoring system. The graphite lintels protect the electric heating elements against strip deviations by being cantilevered above the electric heating elements and protruding from the hybrid wall lining.