JP2679421B2 - Equipment for the production of galvannealed steel sheets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called alloyed hot-dip galvanized steel sheet manufacturing apparatus for carrying out heat treatment after hot-dip galvanizing, and more particularly to a continuous alloyed hot-dip galvanized steel sheet manufacturing apparatus.

That is, in a continuous hot-dip galvanizing method for a steel sheet, the steel sheet is continuously heated and reduced, and then dipped in a hot-dip galvanizing bath to apply a plating treatment to the surface of the steel sheet. Immediately after such hot dip galvanizing, the present invention performs a heat treatment on a plated steel sheet in which the amount of deposit is controlled to a required amount by a gas drawing method or the like to diffuse iron from the steel sheet into the galvanized layer. The present invention relates to an apparatus for producing a galvannealed steel sheet for alloying treatment.

[0003]

2. Description of the Related Art Conventionally, as a heating method for alloying a hot-dip galvanized steel sheet, a direct heating method by gas heating has been generally used. In recent years, induction heating (hereinafter abbreviated as I / H) has been used.
Internal heating method is also being adopted. According to the I / H method, the temperature controllability is particularly improved, while the gas heating method improves the responsiveness.

As a method using induction heating, all I / I switching to induction heating is used as an alternative to the gas heating method.
Combination that uses both H method and gas heating method
Two types of I / H methods are being adopted.

[0005] I / H type alloying treatment (hereinafter abbreviated as GA)
Has been known for a long time (see Japanese Patent Publication No. 37-3103, etc.),
Regarding the combination I / H system with the gas heating system, Japanese Patent Application Laid-Open No. 61-207563 also discloses a gas heating + I / H system (post I / H system) and an I / H + gas heating system (pre-I / H system).
Method).

[0006]

DISCLOSURE OF THE INVENTION The present inventors have paid attention to the superiority of the post I / H method among the combination I / H methods and examined the problems in the apparatus.

That is, the merit of the post I / H method is
(1) The I / H device can be separated from the gas heating furnace and fixed in the online position (the gas heating furnace is
The board will burn out if it is not taken offline). Therefore, the equipment cost is low and the structure is simple, and (2) I / H heating is the final heating, and it is efficient because the furnace temperature can be secured by using the exhaust gas of the gas heating furnace. 3) Heat resistance against exhaust gas from gas heating furnace, heat shock, and further problems of durability, (4) Appropriate power specifications (frequency, voltage, current, etc.) to obtain heating efficiency are set appropriately. There are problems.

An object of the present invention is to solve the problems (3) and (4) described above, and to use the post I / H method of the combination I / H method which makes use of the merits of (1) and (2) described above. An object of the present invention is to provide an apparatus for manufacturing an alloyed hot-dip galvanized steel sheet by the H method.

[0009]

The inventors of the present invention have
As a measure for heat resistance, heat shock, and durability against the exhaust gas of the gas heating furnace of (3), the exhaust gas flow rate or the exhaust gas temperature is controlled above the outlet of the gas heating furnace, that is, on the I / H coil inlet side to control the inner wall of the induction heating device. Limiting the temperature and controlling the temperature of the inner wall of the induction heating device,
By installing expansion bellows at both or one of the entrances and exits of the I / H coil to prevent damage to the I / H coil due to thermal expansion, and by attaching a heat insulating material to the inner wall of the I / H coil and preventing contact with running steel plates. , I learned that problem solving can be done more effectively.

Further, the present inventors have found that it is preferable to set the heating frequency to 10 KHz or more in order to increase the heating efficiency.

It should be noted that 10 KHz is the largest power supply device currently available as a general-purpose type, and the desired efficiency can be obtained even with a thin steel plate of 0.6 mm. Here, 10KHz is a nominal value, generally, it is 9.8 to 9.9KHz to be exact, and 9KHz or more is broadly defined. Further, if the required heating amount can be obtained, 10 KHz or more is preferable.

[0012]

Next, the present invention will be further described with reference to the accompanying drawings. FIG. 1 is a schematic explanatory view of an apparatus for alloying a hot-dip galvanized steel sheet according to the present invention.
With respect to the plated steel sheet 12 pulled up from 10, the amount of coating adhered is adjusted within a predetermined range by the wiping nozzle 14.

The hot dip galvanized steel sheet 12 is then sent to a hot dip galvanized steel sheet alloying apparatus 15 according to the present invention.
The device 15 is composed of a gas heating furnace 16 and an induction heating device 20. The whole including a holding zone and a cooling zone, which will be described later, is housed in a supporting frame mechanism 17, and is appropriately mounted on a deck 18 of each stage by a fixed frame 19.

The plated steel sheet 12 enters the gas heating furnace 16 and is usually heated to 500 to 550 ° C. The galvanized steel sheet 12 exiting the gas heating furnace 16 is further discharged from the gas heating furnace 16.
Entering the induction heating device 20 provided between the side and the holding band , the temperature control action allows precise adjustment within the temperature range.

FIG. 2 is an enlarged partial view of the induction heating device 20 of FIG. 1. As shown in FIG. 2, according to the present invention, the temperature adjusting means 30 for limiting the inner wall temperature of the induction heating device 20 is induction-heated. It is installed at the device entrance. The purpose of providing the temperature adjusting means 30 is to adjust the temperature of the holding zone atmosphere, and an air blowing nozzle or the like is exemplified as the temperature adjusting means for that purpose. In the illustrated example, the air blowing fan 27 is driven based on the measured in-furnace temperature.

A thermometer is installed in order to prevent the temperature of the inner wall of the I / H from being raised more than necessary (temperature control) and to keep it at the required temperature, and suction of the draft air at the I / H inlet is performed. or controlling the amount or blowing can be performed heat shock avoidance or inner wall protected by performing Air. The position of the thermometer is preferably the position shown, but the position above the I / H coil is also possible.

Alternatively, the exhaust gas from the gas heating furnace 16
Scan or restrict the intake引量, or (not shown) damper device for sucking air from the outside may be a provided. Many specific modifications of the damper device 32 are conceivable, which will be apparent to those skilled in the art from the above description. In the example shown in FIG. 1, the draft control fan 2
6 is provided.

As described above, it is effective to provide an exhaust gas control damper or a draft control fan at the outlet of the gas heating furnace for controlling the amount of exhaust gas, and the controllability is further improved in combination with the former temperature adjusting facility.

Also, as shown in FIG. 2, in order to separate the I / H coil from the front and rear equipment, an expansion bellows 40 may be provided on the upper and lower sides or on one side to absorb the thermal expansion of the front and rear equipment. The elastic bellows is made of, for example, a heat resistant cloth (asbestos), and is not limited to a specific structure as long as it has a predetermined airtightness and can absorb thermal expansion. May be made from stainless steel.

When the thermal expansion is too large, the I / H coil body must avoid the pressing force of the upper and lower equipment, and the I / H difference due to the thermal expansion difference.
This is because the coil body will be damaged.

FIG. 3 is a partial sectional view showing the structure of the I / H coil. The inner surface of the coil 42 is covered with a heat insulating layer 44, and the heat insulating layer 44 covers the inner wall portion of the I / H coil. Configure. In this way, the inner wall of the I / H coil 42 is protected by a refractory material (castable), caul board or the like having excellent heat insulating properties to prevent heat from being transferred to the coil itself. The heat insulating layer 44 forming the inner wall portion is appropriately determined according to a specific device. Further, since contact with a running steel plate may occur due to flapping and warpage of the steel plate, it is required to have excellent heat resistance, as well as impact resistance and hardness. Guides for these 46
It is also effective to provide the above and protect the guide wall by colliding with the guide guide before contacting the inner wall.

[0022]

Next, the present invention will be described more specifically with reference to examples. Using the apparatus shown in FIG. 1, the galvanized steel sheet was subjected to an alloying treatment after the completion of hot-dip galvanizing. The alloying conditions were as follows.

Steel plate dimensions: 0.70 mm thickness x 1540 mm width Zn deposition amount: One side 60/60 g / m ² Gas heating furnace: Fuel C gas, fuel load factor 60%, ultimate temperature
500 ℃ I / H heating: Frequency 10 KHz (9.9KHz), power rating Max 10
00kw (320kw)

FIG. 4 is a graph showing the temperature change of the steel sheet in this example. As can be seen, the steel sheet charged into the gas furnace at 430 ° C was first heated to 500 ° C and then I /
The H heating raises the temperature to 520 ° C, at which temperature alloying is completed in the holding zone. In the cooling zone, it is cooled to 300 ℃ and taken out of the furnace.

According to the present invention, the temperature control means (illustrated example: air from the air blowing fan 27 and exhaust gas from the gas heating furnace 16 are mixed, and the furnace atmosphere temperature is set to 520 ° C. The temperature of the steel plate itself is The temperature range is adjusted to the above temperature range by I / H heating.) The post I / H method can operate stably, and the improvement in responsiveness of the gas heating method, which is an advantage of I / H heating, is complemented. The operational effect is increasing.

The present invention has the following advantages. The equipment structure of the present invention is a post I / H method, a furnace temperature adjusting means is provided at the inlet for I / H protection, a telescopic bellows,
The heat pattern was the same except that a heat-resistant material was used, and the product quality and the like were the same as the conventional example. When comparing the cost of electricity consumption and gas heating fuel consumption,
In the post I / H method according to the present invention as compared with the H method,
Running costs have been halved. Gas heating method vs. post I / H, even if the variations in alloying degree are compared
According to the present invention, the method is 1% vs. 0.5%, and the variation is halved. In terms of alloying degree, this means that GA (alloying degree) = 8.5% ± 1% became 8.5% ± 0.5%. Looking at the unsteady response improvement, the gas heating method vs.
Post I / H method = 270 Ton vs 18 Ton, which means that the yield loss decreased by 252 tons / month. post
When the service life of the I / H coil by the I / H method is evaluated, it is about 1
There were no problems with refractory cracks even after a lapse of years.

[0027]

As described above, according to the present invention, the operation temperature is remarkably stabilized and the obtained alloyed alloy has a simple structure in which the furnace temperature adjusting means is provided on the inlet side of the I / H heating device. The quality of the hot-dip galvanized steel sheet exceeds that of the conventional one, and its practical significance is great. Further, the above-mentioned effect is further promoted by providing a telescopic bellows and lining a heat insulating material on the inner wall of the I / H coil.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of an apparatus for producing galvannealed steel sheet according to the present invention.

FIG. 2 is a partially enlarged view of the device according to the present invention.

FIG. 3 is a schematic explanatory view showing a partially modified example of the device according to the present invention.

FIG. 4 is a graph showing changes in steel plate temperature according to an example of the present invention.

[Explanation of symbols]

 10: Hot dip galvanizing bath 12: Coated steel plate 14: Wiping nozzle 15: Alloying device 16: Gas heating furnace 20: Induction heating device 22: Holding zone 24: Cooling zone

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-199365 (JP, A) JP-A-63-85661 (JP, A) JP-A-61-207564 (JP, A)

Claims (4)

(57) [Claims] 1. A method for alloying hot-dip galvanizing,
The alloying device, the holding zone and the cooling zone are continuously provided, and
Alloying apparatus and a gas heating furnace, the outlet side and the coercive of the gas heating furnace
An induction heating device provided between the induction heating device and a holding band, the induction heating device comprising an induction heating coil, and the induction heating device is provided with a temperature adjusting means for controlling the furnace temperature in the holding zone provided on the outlet side of the induction heating device. An apparatus for producing a galvannealed steel sheet, which is installed at the entrance of the apparatus. 2. The production of an alloyed hot dip galvanized steel sheet according to claim 1, wherein expansion bellows are installed at one or both of an inlet and an outlet of the induction heating device to absorb thermal expansion of the induction heating device. apparatus. 3. The production of an alloyed hot dip galvanized steel sheet according to claim 1, wherein a heat insulating material is attached to the inner wall of the induction heating device to improve the thermal shock resistance, heat resistance, and durability of the induction heating device. apparatus. 4. The apparatus for producing a galvannealed steel sheet according to claim 1, wherein an exhaust gas flow rate control means is installed at the outlet of the gas heating furnace.