JP2005163057A - Hot dip galvannealed steel plate manufacturing device, and method for controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method for manufacturing a longitudinal hot dip galvannealed steel plate with a heat-retaining zone to adequately perform iron diffusion of a galvanized layer after a galvanized steel plate passes through an electromagnetic induction heating alloying furnace. <P>SOLUTION: In the longitudinal galvannealed steel plate manufacturing device, a plurality of tubular flame burners to blow fuel gas and air for combustion from the tangential direction of the tubular burner are installed facing each other across a steel plate passing through the heat-retaining zone at a lower side of the heat-retaining zone or immediately before the heat-retaining zone installed on the downstream side of an electromagnetic induction heating alloying furnace. As necessary, a thermometer to measure the temperature of hot gas in the heat-retaining zone and/or a thermometer to measure the surface temperature of a wall surface on the steel plate transport side of the heat-retaining zone are provided in the heat-retaining zone. An operation means to estimate the temperature of the steel plate on the outlet side of the heat-retaining zone from the measured temperature by these thermometers and the operational condition, and a control device to control the fuel flow rate and the air flow rate to match the predetermined hot gas temperature obtained by the operation with the measured temperature of the hot gas are provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an apparatus and a method for producing a vertical alloyed hot-dip galvanized steel sheet, and more particularly, to maintain a retentive zone that appropriately diffuses iron in a plated layer after the steel sheet to be plated has passed through an electromagnetic induction heating alloying furnace. And a temperature control method thereof.

  FIG. 4 shows an outline of a conventional vertical manufacturing apparatus for alloyed hot-dip galvanized steel sheet. The alloyed hot-dip galvanized steel sheet manufacturing apparatus 100 immerses the steel sheet from the annealing furnace in the zinc pot 20, changes the transport direction upward by the sink roll 30 and exits the zinc pot 20, and then the wiping nozzle 40. Thus, the zinc adhesion amount is controlled to a predetermined basis weight. Thereafter, the alloy passes through the alloying furnace 50 and the retentive zone 70, and during that time, iron is diffused into the plating layer to perform alloying, and alloying is stopped in the cooling zone 140, resulting in the alloyed hot-dip galvanized steel sheet 130.

  Alloyed hot-dip galvanized steel sheet 130 has recently been used for a wide range of coatings from thin to thick, and poorly alloyed unless precise temperature control is performed depending on the steel type, steel sheet size, operating conditions, etc. Therefore, temperature control with high accuracy is desired not only in the alloying furnace 50 but also in the retentive zone 70.

  The alloying furnace 50 is broadly classified into a system using a direct fire burner and an electromagnetic induction heating system. Patent Document 1 relates to a system using a direct fire burner as a thermal compensation means for temperature control in the tropical zone 70. A method of diluting the combustion exhaust gas of the direct-fired burner of the conversion furnace 50 with air and introducing it into the retentive zone 70 is proposed, and effective use of energy and gas at a uniform temperature are introduced into the retentive zone.

On the other hand, Patent Document 2 proposes a method using an electric heater as a heat compensation means for the heat retention 70 in the electromagnetic induction heating alloying furnace, and Patent Document 3 discloses a burner for preventing heating unevenness on the heat retention entrance. Proposes a method of installing
JP-A-8-269668 Japanese Patent Laid-Open No. 5-9697 Japanese Patent Laid-Open No. 7-16317

 However, if an electric heater is used as the heat compensation means of the retentive zone 70 in the electromagnetic induction heating alloying furnace, zinc powder may adhere and trip, and the equipment cost increases as a countermeasure. In addition, when performing heat compensation in the burner, it is necessary to control the combustion of the burner according to the heating unevenness generated in the alloying furnace, and it is difficult to determine the location where the heating unevenness occurs.

  When a general turbulent diffusion flame burner is used, the flame directly hits the steel plate, locally becomes hot, and may cause uneven alloying. It is difficult to heat.

  For the reasons described above, in a vertical alloyed hot-dip galvanized steel sheet manufacturing apparatus in which electromagnetic induction heating alloying is installed, an inexpensive and good temperature controllable tropical heat compensation means is desired.

  The present invention has been made to solve the above-mentioned various problems, and is a vertical alloying and melting with a retentive zone that appropriately performs iron diffusion of a plating layer after passing through an electromagnetic induction heating alloying furnace. An object of the present invention is to provide a galvanized steel sheet manufacturing apparatus and a control method thereof.

The object of the present invention can be achieved by the following means.
1. A tubular flame burner that blows fuel gas and combustion air from the tangential direction of the tubular burner immediately below the retentive or immediately before the retentive installed downstream of the electromagnetic induction heating alloying furnace, and a steel plate that passes through the retentive A vertical alloyed galvanized steel sheet manufacturing apparatus, wherein a plurality of such steel sheets are installed so as to face each other.
2. A thermometer for measuring the hot air gas temperature in the heat retention zone in the retentive zone, and a control device for controlling the fuel flow rate and the air flow rate of the tubular flame burner in order to match the measured value of the hot air gas temperature with a target value. 2. The apparatus for producing a vertical alloyed galvanized steel sheet according to 1, wherein

The vertical alloyed galvanized steel sheet manufacturing apparatus according to 31 is further provided with a thermometer for measuring hot air gas temperature in the retentive zone and a thermometer for measuring the surface temperature of the steel sheet transport side wall in the retentive area. Type alloyed galvanized steel sheet manufacturing apparatus, calculation means for predicting the steel sheet temperature on the tropical rain discharge side from the measured temperature values and operating conditions of these thermometers, predetermined hot air gas temperature and hot air gas determined by the calculation An apparatus for producing an alloyed galvanized steel sheet, comprising a control device for controlling a fuel flow rate and an air flow rate in order to match temperature measurement values.
4 A method for producing an alloyed hot-dip galvanized steel sheet, in which a hot-dip galvanized steel sheet having a predetermined adhesion amount is passed through an electromagnetic induction heating alloying furnace and a retentive zone, wherein a hot air gas temperature value at the lower part of the retentive zone is a target A method for producing an alloyed hot-dip galvanized steel sheet, characterized by controlling a fuel flow rate and an air flow rate of a tubular flame burner installed at a lower side or an entrance of the retentive zone so as to have a value.
Manufacturing equipment.

  According to the present invention, since a burner for generating hot air is directly installed in the retentive zone, the equipment can be made more compact and the equipment cost can be reduced than a hot air generator using a general turbulent diffusion flame burner. is there. Moreover, since the steel plate temperature in the tropical region is controlled with high accuracy, it becomes possible to manufacture an galvannealed steel plate having a predetermined degree of alloying.

  A vertical alloyed hot-dip galvanized steel sheet manufacturing apparatus according to the present invention blows a fuel flame and combustion air from a tangential direction of a tubular flame burner to a tubular flame burner immediately before a heat retention lower part or a heat retaining body. It is characterized by installing a plurality in the width direction. The tubular flame burner can complete combustion in the combustion cylinder compared to a general turbulent diffusion flame burner in which the flame extends in the axial direction of the burner, stable combustion is possible even at a high air ratio, and combustion exhaust gas and flame It has features such as a tendency to spread radially on the exit side.

  FIG. 1 is a schematic diagram illustrating the structure of a vertical alloyed hot-dip galvanized steel sheet manufacturing apparatus according to the present invention. In FIG. 1, 1 is an apparatus body, 2 is a zinc pot, 3 is a sink roll, 4 is a wiping nozzle, 5 Is an electromagnetic induction heating furnace, 6 is a tubular flame burner, 7 is a tropical zone, 8 is a hot air gas thermometer, 10 is a cooling zone, 11 is a static pressure pad, 12 is a control device, and 13 is a steel plate.

  The vertical alloyed hot-dip galvanized steel sheet manufacturing apparatus according to the present invention includes a zinc pot 2 that immerses a steel sheet 13 from an annealing furnace (not shown), and a carrying direction of the steel sheet after the zinc pot 2 exits. A sink roll 3 that changes the upward direction, a wiping nozzle 4 that adheres zinc to the steel sheet to a predetermined basis weight, an electromagnetic induction heating furnace 5 that alloyes the adhered zinc on the steel sheet surface, and an iron coating layer. The retentive zone 7 for alloying by diffusion and the cooling zone 10 for stopping the alloying are the basic components, and a plurality of tubular flame burners 6 are attached to the bottom of the retentive zone 7 or at the inlet of the hot zone 7, It arrange | positions so that it may oppose on both sides.

  The tubular flame burner 6 is placed under the retentive zone 7 or immediately before the entrance of the retentive zone 7 so that the flame is not directly applied to the steel plate, and the tubular flame burner 6 is adjusted to a high air ratio combustion to adjust the combustion exhaust gas temperature. Therefore, local temperature increase of the steel sheet can be prevented.

  Further, the vertical alloyed hot-dip galvanized steel sheet manufacturing apparatus according to the present invention may be provided with a static pressure pad 11 that suppresses vibration of the steel sheet on the upper part of the heat retention zone 7 on the steel sheet exit side.

  The tubular flame burner 6 is provided with a tubular combustion chamber with an open end, a nozzle injection port that opens on the inner surface of the combustion chamber, and a nozzle that blows fuel and oxygen-containing gas separately or premixed, The nozzle injection direction is substantially the same as the tangential direction of the peripheral surface of the combustion chamber.

  FIG. 2 shows a vertical alloyed hot-dip galvanized steel sheet manufacturing apparatus according to another embodiment of the present invention. In addition to the vertical alloyed hot dip galvanized steel sheet manufacturing apparatus shown in FIG. 1, a suction duct 14 that guides hot air out of the system by an exhaust blower 15 is provided on the steel sheet exit side upper part of the retentive zone 7.

  FIG. 3 shows a vertical alloyed hot-dip galvanized steel sheet manufacturing apparatus according to another embodiment of the present invention. A retentive wall surface thermometer 9 for measuring the temperature of the wall surface on the side through which the steel plate passes is provided in the retentive zone 7 of the vertical alloyed hot-dip galvanized steel sheet manufacturing apparatus having the configuration shown in FIG. Below, the effect of the tropical wall surface temperature measurement by the tropical wall surface thermometer 9 is demonstrated.

  Transfer of heat to the steel plate 13 in the retentive zone 7 includes heat transfer between the gas inside the retentive zone 7 and the steel plate 13, heat radiation between the wall of the retentive zone 7 and the steel plate 13, and further, the gas inside the retentive zone 7 When the gas contains carbon dioxide or water vapor, the heat radiation of the gas inside the retentive zone 7 and the steel plate can be considered.

  Among these, the heat radiation between the gas and the steel plate has a relatively low gas temperature, and since the gas emissivity is small, it can be said that a large error hardly occurs even if ignored. Therefore, the temperature of the steel plate 13 may be determined by taking into consideration heat transfer with the gas inside the retentive zone 7 and heat radiation from the retentive wall.

  However, the surface temperature of the tropical retentive wall immediately after the installation of the mobile retentive area is considerably low compared to the target steel plate temperature because it is placed outside the line and cooled even if hot air is supplied. Low. Therefore, even if the gas temperature inside the retentive zone is set to the steel plate target temperature, the steel plate temperature does not rise to the target value due to thermal radiation with the retentive wall.

  Therefore, it is possible to control the fuel and / or air to measure the heat retention wall temperature, calculate the amount of heat received by heat radiation with the heat retention wall, and make the hot air gas temperature so that the steel plate becomes the target value. The device configuration and the control method are effective for setting the steel plate temperature to the target value.

Examples will be described below. 3 is immersed in the zinc pot 2 at a speed of 90 m / min using the galvannealed steel sheet manufacturing apparatus shown in FIG. ² (per one side), raise the steel plate temperature to 520 ° C in the electromagnetic induction heating alloying furnace 5 and carry it to a heat retention zone of about 10m in length. Examined.

  A hot air generator 6 having a tubular flame burner as a main part is installed in the mobile retentive zone 7. In addition, a thermometer 8 for measuring the temperature of hot air from the hot air generator and a thermometer 9 for measuring the temperature of the wall surface of the tropical zone 7 were attached to the tropical zone 7.

  In this embodiment, the hot air generator 6 has a diameter of 50 mm and is provided with six on one side at equal intervals in the width direction of the steel sheet. The fuel is coke oven gas and the fuel gas is 15 Nm3 / h at the maximum. Can be supplied.

  The measurement of the steel sheet temperature is performed immediately after the mobile retentive zone 7 is installed in the line (Example 1) and when the surface temperature of the retentive wall rises to around 500 ° C after a sufficient time has elapsed after installation (implemented) Example 2) was performed. In addition, for comparison, when the mobile tropics are not installed (Comparative Example 1), when the tropics are installed and hot air is not supplied (Comparative Example 2), the steel plate is maintained immediately after installation. Steel plate temperature measurement was carried out when hot air of 500 ° C., which is the same as the heat target temperature of 500 ° C., was supplied (Comparative Example 3).

  The results are shown in Table 1. Examples show examples of the present invention. Although the decrease in steel sheet temperature can be suppressed by installing the tropical zone, in order to further promote alloying in the tropical zone, adjusting the hot air temperature to be supplied in consideration of the surface temperature of the tropical zone wall as shown in the present invention example It was confirmed that the steel plate temperature could be controlled with high accuracy immediately after installation, when the wall temperature in the tropical zone was still cold.

The figure which shows one Embodiment of the vertical alloying hot-dip galvanized steel plate manufacturing apparatus based on this invention. The figure which shows other embodiment of the vertical galvannealed steel plate manufacturing apparatus which concerns on this invention. The figure which shows other embodiment of the vertical type galvannealed steel plate manufacturing apparatus based on this invention. The figure which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Zinc pot 3 Sink roll 4 Wiping nozzle 5 Electromagnetic induction heating furnace 6 Tubular flame burner 7 Retentive zone 8 Hot-air gas thermometer 9 Retentive wall surface thermometer 10 Cooling zone 11 Static pressure pad 12 Controller 13 Steel plate 20 Zinc Pot (conventional example)
30 sink roll (conventional example)
40 Wiping nozzle (conventional example)
50 Alloying furnace (conventional example)
70 tropical rain (conventional example)
100 devices (conventional example)
130 Alloyed galvanized steel sheet (conventional example)
140 cooling zone (conventional example)

Claims (4)

A tubular flame burner that blows fuel gas and combustion air from the tangential direction of the tubular burner at the bottom of the tropics or immediately before the temperament installed downstream of the electromagnetic induction heating alloying furnace, sandwiches the steel plate that passes through the temperament. A vertical alloyed galvanized steel sheet manufacturing apparatus characterized in that a plurality of them are installed so as to face each other. The thermostat has a thermometer for measuring the hot air gas temperature in the warm zone, and a controller for controlling the fuel flow rate and the air flow rate of the tubular flame burner in order to match the measured value of the hot air gas temperature with the target value. The vertical alloyed galvanized steel sheet manufacturing apparatus according to claim 1. The vertical alloyed galvanized steel sheet manufacturing apparatus according to claim 1, further comprising a thermometer for measuring hot air gas temperature in the retentive zone and a thermometer for measuring the surface temperature of the steel sheet conveying side wall in the retentive area. Vertical alloyed galvanized steel sheet manufacturing apparatus, calculation means for predicting the steel sheet temperature on the tropical rain discharge side from the measured temperature value and operating conditions of these thermometers, predetermined hot air gas temperature and hot air determined by the calculation An apparatus for producing an alloyed galvanized steel sheet, comprising a control device for controlling a fuel flow rate and an air flow rate in order to make the gas temperature measurement values coincide with each other. A method for producing an alloyed hot-dip galvanized steel sheet in which a hot-dip galvanized steel sheet having a predetermined adhesion amount is passed through an electromagnetic induction heating alloying furnace and a retentive zone, wherein a hot air gas temperature value at the lower part of the retentive zone is a target value A method for producing an alloyed hot-dip galvanized steel sheet, characterized by controlling the fuel flow rate and air flow rate of a tubular flame burner installed at the lower side or at the entrance of the tropics.

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