Resistance annealing furnace to anneal at least one metal or metal alloy wire, strand, string, wire rod or strip, the annealing furnace having at least two electric axles provided with respective electric contact rings for conveying the metal or metal alloy wire, strand, string, wire rod or strip, and a DC voltage generator, which can be supplied by an AC voltage (Uac) to generate an annealing voltage (Uann) applied between the two electric axles so as to produce an electric current in the portion of the metal or metal alloy wire, strand, string, wire rod or strip extending between the two electric axles, which provokes an annealing due to the Joule effect. At least one of the electric contact rings is made of a non-metal electric conductor material, for example graphite.

An apparatus and a method for rapidly heating cold-rolled strip steel (10). The apparatus for rapidly heating cold-rolled strip steel (10) comprises a heating zone, a soaking zone, and a cooling zone, and the heating zone is sequentially divided into a first heating section (1), a second heating section (2), a third heating section (3), and a fourth heating section (4) along a moving direction of the strip steel (10) to be heated, the first heating section (1) and the fourth heating section (4) being radiant heating sections, and the second heating section (2) and the third heating section (3) being inductive heating sections. The method for rapidly heating cold-rolled strip steel (10) uses the apparatus for rapidly heating cold-rolled strip steel (10) to heat the strip steel (10).

A resistance annealing furnace for annealing a metal wire, strand, string, wire rod or strap having at least two electric axes provided with respective pulleys to convey the metal wire and a DC voltage generator suppliable with an AC voltage to generate an annealing voltage applied between the two electric axes so as to provoke the annealing due to Joule effect. The DC voltage generator has active supplying means supplied with the AC voltage so as to generate an intermediate DC voltage, a pulse width modulator to transform the intermediate voltage into a first PWM voltage with the same amplitude, a voltage transformer to transform the first PWM voltage into a second PWM voltage with a smaller amplitude, and a voltage rectifier stage to transform the second PWM voltage into the annealing voltage.

A resistance annealing furnace for annealing a metal wire, strand, string, wire rod or strap having at least two electric axes provided with respective pulleys to convey the metal wire and a DC voltage generator suppliable with an AC voltage to generate an annealing voltage applied between the two electric axes so as to provoke the annealing due to Joule effect. The DC voltage generator has active supplying means supplied with the AC voltage so as to generate an intermediate DC voltage, a pulse width modulator to transform the intermediate voltage into a first PWM voltage with the same amplitude, a voltage transformer to transform the first PWM voltage into a second PWM voltage with a smaller amplitude, and a voltage rectifier stage to transform the second PWM voltage into the annealing voltage.

Provided is a hot-band annealing equipment provided with a heating zone, a soaking zone and a cooling zone for subjecting a Si-containing hot rolled steel sheet to hot-band annealing, wherein when the Si-containing hot rolled steel sheet is subjected to hot-band annealing with the hot-band annealing equipment provided with a rapid heating device at an upstream side of the heating zone and/or in an inlet side of the heating zone, the hot rolled steel sheet is heated by not lower than 50 C. at a heating rate of not less than 15 C./s by using the rapid heating device to improve a descaling property, whereby descaling can be performed only by pickling without requiring mechanical descaling or heating the steel sheet in the pickling process. Also provided are a hot-band annealing method and a descaling method using the above equipment.

A resistance annealing furnace for annealing a metal wire, strand, string, wire rod or strap having at least two electric axes, which are provided with respective pulleys for conveying the metal wire, and DC voltage generator means suppliable by an AC voltage source to generate an annealing voltage applied between the two electric axes. The DC voltage generator means has a first voltage rectifier stage connectable to the AC voltage source to generate an intermediate DC voltage, an active power filter, connected so as to compensate the current harmonics at the input of the first voltage rectifier stage, a pulse width modulator to transform the intermediate voltage into a first PWM voltage, a voltage transformer to transform the first PWM voltage into a corresponding second PWM voltage, and second voltage rectifier means to transform the second modulated PWM voltage into the annealing voltage.

A resistance annealing furnace for annealing a metal wire, strand, string, wire rod or strap having at least two electric axes, which are provided with respective pulleys for conveying the metal wire, and DC voltage generator means suppliable by an AC voltage source to generate an annealing voltage applied between the two electric axes. The DC voltage generator means has a first voltage rectifier stage connectable to the AC voltage source to generate an intermediate DC voltage, an active power filter, connected so as to compensate the current harmonics at the input of the first voltage rectifier stage, a pulse width modulator to transform the intermediate voltage into a first PWM voltage, a voltage transformer to transform the first PWM voltage into a corresponding second PWM voltage, and second voltage rectifier means to transform the second modulated PWM voltage into the annealing voltage.

Provided is a wiredrawn product drawn from a heat-treated steel containing: 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 a GOS value/average crystal grain size is greater than or equal to ?0.6?GAM value+1.5 at a grain boundary setting angle of 2? and a step number of 0.07 ?m.

A method for controlling surface reactions on a steel strip running through a furnace includes, successively, a first section, a second section, and a third section separated by a sealing element, an atmosphere in the second and third sections being oxidizing and reducing respectively, the method including: heating, in the first section, the steel strip to between 600 and 750 C., while causing the atmosphere therein to be slightly oxidizing and to include: an H.sub.2 content inferior to 2%; an O.sub.2 content inferior to 0.1%; an H.sub.2O or CO.sub.2, or H.sub.2O+CO.sub.2 content superior to 0.03%; a controlled dew point ranging from 50 to 15 C.; and a controlled concentration of CO+CO.sub.2 maintained below 2%. All percentages are expressed in terms of volume.

A method for controlling surface reactions on a steel strip running through a furnace includes, successively, a first section, a second section, and a third section separated by a sealing element, an atmosphere in the second and third sections being oxidizing and reducing respectively, the method including: heating, in the first section, the steel strip to between 600 and 750 C., while causing the atmosphere therein to be slightly oxidizing and to include: an H.sub.2 content inferior to 2%; an O.sub.2 content inferior to 0.1%; an H.sub.2O or CO.sub.2, or H.sub.2O+CO.sub.2 content superior to 0.03%; a controlled dew point ranging from 50 to 15 C.; and a controlled concentration of CO+CO.sub.2 maintained below 2%. All percentages are expressed in terms of volume.