JPH05209258A - Method for removing foreign matter in hot-dipping bath and device therefor - Google Patents

Abstract

PURPOSE:To greatly reduce the time to remove the deposited bottom dross in removing the bottom dross to be deposited on the bottom of a hot-dipping tank by adding the float-promoting element. CONSTITUTION:After an element to promote floating of foreign matters is added by using a device consisting of a movable pump supporting mechanism 7 provided on the top of a hot-dipping tank 1, a driving part 9 supported by the pump supporting mechanism 7 and a pump 12 for a hot-dipping bath which is connected to the driving part 9 and immerses a discharge pipe 16 in the bath facing toward the bottom part of the hot-dipping tank 1, suction of the molten metal is started in the hot-dipping bath 2 and the sucked molten metal is discharged against the deposited foreign matters, and convection is caused in the hot-dipping bath 2 due to forced stirring, promoting the substitution reaction between the foreign matters forming alloys and the element to promote floating of the foreign matters, thus floating of the foreign matters. This method allows the time to remove and treat the foreign matters deposited in the hot-dipping tank to be greatly reduced, and enables reduction of the stopping time of the hot-dipping line in the periodical maintenance, and at the same time, increases the production of hot-dipped steel strip.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for removing foreign matter in a bath of molten metal plating called bottom dross, which deposits on the bottom of a bath of molten metal plating.

[0002]

2. Description of the Related Art In recent years, surface-treated steel sheets, such as hot-dip galvanized steel sheets, which are excellent in corrosion resistance, weldability and paintability, are rapidly growing in demand for applications such as automobiles, civil engineering, construction and home appliances. .. As a method of manufacturing this surface-treated steel sheet,
Continuous hot-dip galvanizing, continuous hot-dip aluminum and other continuous hot-dip metal plating methods are mainly used.
In the continuous hot dip metal plating method, as shown in FIG. 2, the steel strip 21 whose mechanical properties have been adjusted and whose surface has been cleaned and activated in a continuous furnace has a molten metal bath 23 through a snout 22.
The support roll 2 is immersed in the plating metal 24 inside and the direction of travel is changed by the sink roll 25 in the bath.
After being pulled up from the molten metal bath 23 via 6 and 27, gas is jetted from the wiping nozzle 28 to squeeze out the excess plating solution to adjust the amount of plating deposition. Then, the plated steel strip 21 is cooled to room temperature after passing through the top roll 29.

In the plating metal 24 in the molten metal tank 23 of the above continuous metal plating method, the sink roll 2 immersed in the plated steel strip 21 or the molten metal tank 23 is disposed.
5, Fe eluted from the in-bath rolls such as the support rolls 26 and 27 and the supporting frame of the in-bath rolls reacts with Zn of the plating metal to form the bottom dross 30 containing FeZn ₇ as a main component. The specific gravity of this bottom dross 30 is
Since the plating metal is heavier than Zn, it settles and deposits on the bottom of the molten metal bath 23. This tendency is due to Al in the plated metal 24.
This is particularly remarkable in the molten metal tank 23 of the production line of the alloyed hot-dip galvanized metal strip with a small amount of addition. The bottom dross 30 deposited on the bottom of the molten metal tank 23 is rolled up from the bottom of the molten metal tank 23 by the movement of the plated steel strip 21, and adheres to the surface of the plated steel strip 21 to significantly impair the product appearance on the surface of the steel strip. Become. This bottom dross 30
The plated steel strip 21 on which is attached becomes a problem particularly in a steel plate used for an extremely severe surface quality application such as an outer plate of an automobile. Therefore, the bottom dross 30 deposited on the bottom of the molten metal tank 23 needs to be removed.

As a method for removing bottom dross accumulated on the bottom of the molten metal tank, conventionally, the entire continuous hot dip galvanizing line is completely stopped for several days or the operation is interrupted to remove the bottom dross accumulated on the bottom of the molten metal tank. It was done by manual labor, which had a poor scraping effect. However, it is extremely uneconomical to suspend a line with large capital investment for several days. As a countermeasure against this, an alloy component (for example, Al) that reacts with iron or iron alloy having a higher specific gravity than the hot dip galvanizing bath to generate an iron-based metal having a lower specific gravity than the galvanizing bath is added. Of the surface of the plating bath is made higher than that of other parts in the bath, and bottom dross generated during hot dip galvanizing of steel products is floated on the surface of the bath (JP-A-47-38630). As an auxiliary means for accelerating this reaction, as shown in FIG. 3, the floating dross 31 generated by the above reaction and floating in the plating bath is passed through a gas blowing pipe 32 of a small diameter to gas such as N _2. And the floating dross 31 is floated by the bubbles 33 to remove the floating dross 31. Also,
As a method utilizing this principle, a molten metal tank has been developed in which a partition is provided in the molten metal tank and a reaction melting tank provided with an agitator is provided in the molten metal tank. As another method, a ceramic fiber sheet is arranged so that a part of its longitudinal direction is immersed in the galvanizing bath, and bottom dross attached to the sheet in the galvanizing bath is removed from the galvanizing bath. A method of feeding from one side and taking out by pulling up on the other side (Japanese Patent Laid-Open No. 61-190055), in a hot dip metal passage of a hot metal flow guide which is attached to an electromagnetic pump and raises a part of the hot dip metal bath. A method in which a dross filter is provided and the galvanized metal is circulated by an electromagnetic pump to remove the dross by the dross filter.
Japanese Patent No. 52563).

[0005]

[SUMMARY OF THE INVENTION However, the method disclosed in JP-A-47-38630 are more than just a substitution reaction by adding Al, it takes a long time to floating processing dross, also, N ₂ blowing Even if auxiliary means such as bubbling is used, the treatment time is not sufficiently shortened because the zinc bath has a large specific gravity and the amount of gas blown is limited. In addition, when a large amount of gas is blown in, the plating bath is scattered around the molten metal tank due to the rapid floating of the gas, which causes various problems such as a safety problem. In addition, the method of using a molten metal tank provided with a reaction melting tank with an agitator inside the molten metal tank has the effect of suppressing the alloying of the plating film by Al, so that the production quality of the plating line is alloyed. In the case of steel sheet, the amount is limited to the smallest possible amount. If a large amount of Al is constantly added to generate top dross and promote floating, a part of it remains in the plating bath, causing poor alloying. And the quality deteriorates.

Furthermore, the method disclosed in Japanese Patent Laid-Open No. 61-190055 uses a large amount of sheets made of ceramic fibers, which increases the cost accordingly, and thus has not yet been put to practical use. .. Furthermore, the technique disclosed in Japanese Utility Model Laid-Open No. 57-52563 is not practical because the dross filter causes clogging in a short time.

The object of the present invention is to promote the substitution reaction and floatation of the bottom dross and the floatation promoting element when the bottom dross deposited on the bottom of the molten metal plating bath is removed by adding the floatation promoting element, An object of the present invention is to provide a method and an apparatus for removing foreign matters in a molten metal plating bath, which can significantly reduce the time for removing the accumulated bottom dross.

[0008]

[Means for Solving the Problems] The inventors of the present invention have conducted earnest research to achieve the above object. As a result, by sucking the plating bath in the molten metal plating bath and discharging it toward the bottom dross accumulated at the bottom of the molten metal plating bath, if convection due to forced agitation of the plating bath occurs,
Iron-zinc alloy and A without air oxidation of plating bath
It was clarified that the substitution reaction with l and the floatation of accumulated foreign matter can be promoted, and the present invention was reached.

That is, the present invention is a method for removing foreign matter deposited on the bottom of a molten metal plating tank by adding the foreign matter floating promoting element to the surface and removing the foreign matter floating promoting element, and then sucking the plating metal bath. Then, the foreign matter is discharged toward the deposited foreign matter, and convection is generated in the plating metal bath by forced agitation to promote the substitution reaction between the foreign matter forming alloy and the foreign matter floating promoting element and the floating.

Further, a movable pump support mechanism provided on the upper portion of the molten metal plating tank, a drive section supported by the pump support mechanism, and a discharge port directed to the bottom portion of the molten metal plating tank connected to the drive section. It is an apparatus for removing foreign matter in a hot-dip galvanizing bath, which comprises a hot-dip galvanizing metal bath pump.

[0011]

In the present invention, after the foreign matter floating promoting element is added to the molten metal plating tank, the plating metal bath is sucked and discharged toward the deposited foreign matter to cause convection by forced agitation in the plating metal bath. The replacement reaction between the alloy forming the foreign matter and the foreign matter floating promoting element is promoted by the convection due to the forced stirring and the floating of the deposited foreign matter is promoted without air-oxidizing the plating metal bath. As a result, the iron-foreign material levitation promoting element alloy having a smaller specific gravity than the plating metal bath generated by the substitution reaction between the alloy forming the alien material and the foreign material levitation promoting element is rapidly floated by convection due to forced stirring. The reaction time and the floating treatment time of the deposited foreign matter can be greatly shortened.

Further, in the apparatus for removing foreign matter in the molten metal plating bath of the present invention, the pump support mechanism for moving the pump and the molten plating metal bath pump connected to the drive unit is movably provided. As a result, the discharge port can be uniformly positioned in the entire molten metal plating bath. As a result, the foreign matter deposited on the bottom of the molten metal plating tank is forcibly stirred by the molten plated metal discharged from the discharge port, and the substitution reaction between the bottom dross that has sedimented and accumulated and the foreign matter floating promoting element is promoted to float. At the same time as the dross is formed, the floating on the hot-dip metal bath is promoted and the surface becomes a dross. Then, the top dross floating on the hot-dip metal bath is discharged and removed to the outside of the hot-dip bath by human or mechanical force.

The pump support mechanism according to the present invention may have any structure as long as it can support and move the drive unit and the hot dip metal bath pump connected to the drive unit. For example, it is suspended by a wire from a hook of a crane. The drive unit installed on the support base and the drive shaft of the drive unit are connected to the impeller shaft in the pump casing via the coupling, and the direction change lever provided on the support base is manually operated to rotate the hook of the crane. A system in which the pump support mechanism can be moved by moving the crane or by moving the crane, or the drive mechanism and the hot dip metal bath pump connected to this are installed in the suspension support mechanism that can move back and forth to the upper part of the hot metal plating tank. Etc. are recommended. Further, as the foreign matter floating promoting element in the present invention, for example, if the hot-dip plated metal is Zn, Al having a stronger affinity for Fe than Zn is added to the plating bath.

[0014]

【Example】

Example 1 Details of the method of the present invention will be described below with reference to FIG. FIG. 1 is an overall configuration diagram of an apparatus for removing foreign matter in a hot dip galvanizing bath according to the present invention. In FIG. 1, 1 is a hot dip galvanizing tank, 2 is a zinc bath in the hot dip galvanizing tank 1,
3 is a bottom dross deposited and deposited on the bottom of the hot dip galvanizing tank 1, 4 is a floating dross in the zinc bath 2, and 5 is a top dross on the surface of the zinc bath 2. 6 is a hook of a crane (not shown), 7 is a support base suspended from the hook 6 by a wire 8, and an electric motor 9 is installed on the support base 7.
If the impeller (not shown) in the pump casing 14 is rotated via the impeller shaft 13 of the molten zinc pump 12 that is connected to the rotary shaft 10 of FIG. 1 via the coupling 11, the zinc bath 2 is sucked from the suction port 15. It is configured to inject from the discharge pipe 16 toward the bottom dross 3 settled and deposited on the bottom of the hot dip galvanizing tank 1. Reference numeral 17 is a guide rod, and 18 is a direction changing lever, which is configured so that the position of the discharge pipe 16 of the molten zinc pump 12 can be changed by manipulating the direction changing lever 18 manually.

Since the bottom dross 3 settled and deposited on the bottom of the hot-dip galvanizing tank 1 is removed because of the above-described configuration, Al is contained in the hot-dip galvanizing tank 1, for example, 0.35.
After adding so as to have a concentration of about%, a pump 12 for molten zinc installed on a support base 7 suspended by a wire 8 on a hook 6 of a crane (not shown) is placed in a zinc bath 2 of a galvanizing tank 1. insert. When the electric motor 9 is driven to rotate an impeller (not shown) in the pump casing 14 via the impeller shaft 13, the molten zinc sucked from the suction port 15 is discharged from the discharge pipe 16 to the bottom of the galvanized bath 1. It is circulated and injected toward the bottom dross 3 that has settled and accumulated. As a result, the zinc bath 2 is forcibly stirred by the molten zinc discharged from the discharge pipe 16 of the molten zinc pump 12, the convection of the zinc bath 2 is caused, and the bottom dross 3 that has been sedimented and deposited floats, so that the substitution reaction occurs. Is significantly promoted, and the Fe--Zn alloy has a lighter specific gravity than the zinc bath 2.
At the same time as the -Al alloy is formed into the floating dross 4, the floating on the surface of the zinc bath 2 is promoted, and the top dross 5 floats on the surface of the zinc bath 2. The top dross 5 floating on the surface of the zinc bath 2 is discharged and removed to the outside of the hot dip galvanizing tank 1 by manpower or mechanical force. In this case, according to the present invention, unlike the conventional gas stirring, since the stirring is performed in the zinc bath 2 in the hot dip galvanizing tank 1, there is no danger of blowing up the zinc bath 2 and the zinc bath 2 Also, since dross is not oxidized, dross generation due to oxidation can be suppressed.
By manipulating the direction changing lever 18 manually, the position of the discharge pipe 16 of the hot-dip galvanizing pump 12 is changed to convert the bottom dross 3 of the entire bottom of the hot-dip galvanizing tank 1 into the top dross 5. It can be removed in a short time.

Example 2 Using the foreign matter removing device in the molten metal plating bath of Example 1,
Bottom dross was removed in a galvanizing tank having a capacity of 160 tons, and the result was compared with the conventional case of N ₂ blowing with a small diameter pipe. It took about 24 hours to blow N _{2 with a} small-diameter pipe, but 8 to 1 in the method of the present invention.
It was possible to shorten it to 0 hours, and it was possible to shorten the working time significantly.

[0017]

As described above, according to the method and apparatus for removing foreign matter in a molten metal plating bath of the present invention, the repair time, which is conventionally set by the restriction of foreign matter treatment in the molten metal plating bath, can be greatly shortened. It is possible to shorten the stoppage period of the hot-dip galvanizing line due to the periodic repair, and the production amount of hot-dip galvanized steel strip can be increased accordingly. Further, compared with the conventional case, there is a great advantage that the molten metal is prevented from scattering and the safety is improved.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an apparatus for removing foreign matter in a hot-dip galvanizing bath according to the present invention in Example 1.

FIG. 2 is a schematic diagram showing an outline of a general continuous hot-dip metal plating line.

FIG. 3 is a schematic explanatory view of a conventional method for removing foreign matter in a hot-dip galvanizing bath.

[Explanation of symbols]

 1 Hot dip galvanizing tank 2 Zinc bath 3,30 Bottom dross 4,31 Floating dross 5 Top dross 6 Hook 7 Support 8 Wire 9 Electric motor 10 Rotating shaft 11 Coupling 12 Zinc bath pump 13 Impeller shaft 14 Casing 15 Suction port 16 Discharge Pipe 17 Guide rod 18 Direction conversion lever 21 Steel strip 22 Snout 23 Molten metal tank 24 Hot-dip metal 25 Sink roll 26, 27 Support roll 28 Wiping nozzle 29 Top roll 32 Small diameter pipe 33 Bubbles

Claims (2)

[Claims] 1. A method for removing foreign matter deposited on the bottom of a molten metal plating tank by adding the foreign matter floatation promoting element to float and removing the foreign matter floatation promoting element, and then suctioning and depositing a plating metal bath. Discharge foreign matter in a molten metal plating bath characterized by accelerating the substitution reaction and floating of the foreign matter forming alloy with the foreign matter levitation promoting element by causing convection in the plating metal bath by forced agitation toward the foreign matter. Method. 2. A movable pump support mechanism provided on an upper portion of the molten metal plating tank, a drive unit supported by the pump support mechanism, and a discharge port connected to the drive unit and directing a discharge port toward the molten metal plating tank bottom portion. A device for removing foreign matter in a hot-dip galvanizing bath consisting of a hot-dip galvanizing metal bath pump.