Provided is a continuous hot-dip galvanizing apparatus comprising: a vertical annealing furnace having heating, soaking zone, and cooling zones therein; and a hot-dip galvanizing line downstream of the cooling zone. The heating, soaking, and cooling zones each have, in its upper portion, at least one upper hearth roll and, in its lower portion, at least one lower hearth roll. The soaking zone has a first and second humidified gas supply ports to supply a humidified gas having a dew point of 10° C. to 30° C. to the soaking zone. The first and second humidified gas supply ports are 1.0 m to 5.0 m lower than the center of the lower and upper hearth rolls, respectively, and overlap the steel sheet. The first humidified gas supply port is provided only for an ascending pass and the second humidified gas supply port is provided only for a descending pass.

Provided are a method of predicting hydrogen content in steel of a steel strip etc. Provided is, in a continuous galvanizing line that performs manufacturing processes including an annealing process, a coating process, and a reheating process of a steel strip, a method of predicting hydrogen content in steel of a steel strip downstream of the reheating process, including acquiring at least one parameter selected from operation parameters of the continuous galvanizing line and transformation rate information measured in at least one of the annealing process and the reheating process as input data, and predicting hydrogen content in steel of a steel strip downstream of the reheating process using a prediction model of hydrogen content in steel that has been trained by machine learning and that outputs information on hydrogen content in steel of a steel strip downstream of the reheating process as output data.

Equipment for the continuous hot dip-coating of a metal strip 9 including an annealing furnace, a tank 2 containing a liquid metal bath 3, a snout connecting the annealing furnace and tank 2, through which the metal strip 9 runs in a protective atmosphere and the lower part of the snout, the sabot 5, is at least partly immersed in the liquid metal bath 3 in order to define with the surface of the bath, and inside this snout, a liquid seal 6, an overflow 7 not connected to the snout, the overflow 7 including at least one tray 8, placed in the vicinity of the strip 9 when entering the liquid metal bath 3 and encompassed by liquid seal 6.

A continuous hot-dip galvanizing apparatus has a vertical annealing furnace, one or more hearth rolls, a hot-dip galvanizing apparatus, an alloying line, and humidified gas supply ports. When the steel sheet having a Si content of 0.2 mass % or more is conveyed inside the annealing furnace, the humidified gas supply ports positioned in a latter part of the soaking zone supply the humidified gas to the soaking zone and the at least one dry gas supply port supplies the dry gas to the soaking zone. When the steel sheet having a Si content of less than 0.2 mass % is conveyed inside the annealing furnace, the plurality of the humidified gas supply ports do not supply the humidified gas to the soaking zone and the at least one dry gas supply port supplies the dry gas to the soaking zone.

An equipment for the continuous hot dip-coating of a metallic strip comprising: an annealing furnace, a tank containing a liquid metal bath, a snout connecting the annealing furnace and said bath, through which the metallic strip runs in a protective atmosphere and the lower part of said snout, the snout tip, is at least partly immersed in the liquid metal bath in order to define with the surface of the bath, and inside this snout, a liquid seal, a moveable support system, on at least one tank side, comprising connecting means, an overflow connected to said moveable support system through said connecting means, comprising at least one vat and at a least one pump.

Provided is a method for producing a galvannealed steel sheet. When the steel sheet passing through the soaking zone is a type of steel containing 0.2 mass % or more of Si, both dry gas and humidified gas are supplied to the soaking zone, where the humidified gas is supplied only from the humidified gas supply port positioned in a latter part of the soaking zone among a plurality of humidified gas supply ports, where the latter part of the soaking zone is determined considering a sheet passing speed V and a target temperature T on the exit side of the soaking zone.

A method comprises: annealing a steel sheet by conveying the steel sheet through a heating zone, a soaking zone, and a cooling zone in the stated order in an annealing furnace; and then applying a hot-dip galvanized coating onto the steel sheet discharged from the cooling zone. Reducing or non-oxidizing humidified gas and reducing or non-oxidizing dry gas are supplied into the soaking zone. A CO gas concentration is measured using a CO gas concentration meter provided in an exhaust portion for gas in the soaking zone. A decarburized layer thickness of the steel sheet is calculated from the measured CO gas concentration. At least one of a flow rate and a dew point of the humidified gas is controlled so that the calculated decarburized layer thickness is less than or equal to a predetermined thickness.

Disclosed is a treatment line for the continuous treatment of metal strips having a dual purpose, i.e. for producing strips that are annealed and dip-coated with a metal alloy and for producing strips that are annealed and not coated, comprising a dual-purpose cooling tower, i.e. for cooling strips that are annealed and not coated in a non-oxidizing atmosphere and for air-cooling strips that are annealed and coated.

A method for rinsing an overflow chamber at the bath-side end of a snout of a device for hot-dip coating a metal strip is presented. The snout guides the metal strip in a protective gas atmosphere before the metal strip is coated with a metal melt. A rinsing cycle is carried out in the overflow chamber of the snout by feeding metal melt from the molten bath into the overflow chamber and at the same time, sucking and pumping said melt out of the overflow chamber back into the molten bath. This rinsing cycle can be performed even when the snout has been retracted from the melt by supplying the melt from the molten bath to the overflow chamber with a delivery pump.

A device for removing foreign material from a molten metal surface in a steel sheet hot-dip galvanizing process, of the present invention, comprises: a snorkel part of which the end portion is submerged under the molten metal surface of a hot-dip galvanizing bath so as to encompass a steel sheet inserted into the hot-dip galvanizing bath, in order to prevent the oxidization thereof; a snout including a dam unit having a dam forming part which encompasses the steel sheet from the end portion of the snorkel part so as to be spaced a predetermined gap from same, and which allows a molten galvanizing solution inside the hot-dip galvanizing bath to flow over toward the inner peripheral surface of the snorkel part so as to prevent the foreign material that falls onto the molten metal surface inside the snorkel part from attaching to the steel sheet; and a molten zinc discharge unit which is provided inside the snorkel part so as to pump, toward the molten metal surface inside the hot-dip galvanizing bath, the molten galvanizing solution having flowed over the dam forming part of the damp unit, thereby preventing the foreign material included in the molten galvanizing solution, having flowed over the dam forming part, from mixing into the molten galvanizing solution inside the hot-dip galvanizing bath and re-polluting the molten galvanizing solution or flowing into the snorkel part again.