JP4794763B2 - Snout of continuous hot dipping equipment - Google Patents

Description

【００２２】
表に示したように、比較例では浴面上昇時にスナウト内の浮遊物量が急増しているのに対し、発明例では浮遊物量の変動は殆どなく、浮遊物の少ない良好な浴面状態が安定に維持されている。この相違は、比較例ではスナウト内壁面に浮遊物が付着するのに対し、発明例ではセラミックス皮膜の効果として浮遊物の付着現象が抑制防止されることによる。発明例における浮遊物の付着防止効果は、使用後におけるスナウト内壁面の表面状態の相違にも明瞭に示されている。このように発明例はスナウト内壁面の浮遊物の付着が防止され、浮遊物の少ないめっき浴面が維持される効果として、製品めっき鋼板の表面欠陥の発生率は比較例の半分に大きく低減している。発明例における製品表面欠陥の防止効果は、参考例（供試スナウト１）のそれをも上回っている。
【００２３】
【発明の効果】
本発明のスナウトは、内壁面に対する浮遊物の付着が抑制防止されることにより、めっき浴面の浮遊物量の急増（内壁面に付着した浮遊物が浴面上昇に伴って再溶解することにより生じる）は未然に防止される。従って、本発明のスナウトを用いて行なう溶融金属めっき操業においては、ポンプ等による浮遊物の外部排出を適宜実施することにより、スナウト内のめっき浴面を浮遊物の少ない状態に安定に維持し、浮遊物に起因するめっき製品の表面欠陥を抑制防止することができる。また浮遊物の付着防止効果として、スナウトの補修頻度が減少し、耐用寿命が改善されることにより、メンテナンスの軽減および溶融金属めっきライン効率の向上等の効果も得られる。
【図面の簡単な説明】
【図１】本発明のスナウトの要部を示す断面図である。
【図２】スナウトの内側のめっき浴面近傍を模式的に示す斜視図である。
【図３】連続溶融金属めっきラインのめっき装置部を模式的に示す正面図である。
【図４】スナウト内のめっき浴面の上下変動とスナウト内壁面の浮遊物の付着状態を示す断面説明図である。
【符号の説明】
１ ：焼鈍炉
２ ：スナウト
２_１：セラミックス皮膜
３ ：溶融金属めっき浴（めっき浴）
３_１：浴面
４ ：シンクロール
Ｆ ：浮遊物（ドロス）
Ｄ ：付着物
Ｗ ：被めっき材（ストリップ）
ａ,ｂ：スナウトポンプのダクト開口位置（吸込口,吐出口）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the improvement of the snout of a continuous molten metal plating apparatus, and in particular, maintains the plating bath surface in the snout in a good bath surface state with less suspended matter, and is effective for surface defects of plated products caused by suspended matter. Therefore, suppression can be prevented.
[0002]
[Prior art]
In hot dip plating lines such as continuous hot dip aluminum plating and hot dip galvanization, strips such as cold-rolled steel strips, which are plated materials derived from an annealing furnace, are introduced into a plating bath via a snout. In FIG. 3, 1 is an annealing furnace, 2 is a snout, and 3 is a molten metal plating bath. The snout (2) is inclined between the annealing furnace (1) and the plating bath (3), and the lower end is immersed in the plating bath (3). The material (strip) (W) to be plated is introduced into the plating bath (3) through the snout (2), and plated by passing through the bath through the sink roll (4). Snout (2) is a member (cylindrical body made of heat-resistant alloy cast steel or the like) for blocking atmospheric contact of strip (W) and preventing oxidative contamination (causing plating defects) on the strip surface, The inner space is maintained in an inert atmosphere such as nitrogen gas.
[0003]
As shown in FIG. 4, suspended matter (F) is inevitably generated on the surface of the molten metal plating bath. The suspended matter (F) is a fluid in a molten or semi-molten state mainly composed of oxides and is generally called dross. The suspended matter (F) present on the bath surface (3 ₁ ) in the snout (2) tends to adhere to the surface of the strip (W) introduced into the bath, causing non-plating to the plated product, and dross. This causes a surface defect called pulling or bumping.
[0004]
As a preventive measure, a method of sucking and discharging the suspended matter (F) to the outside with a pump (snout pump) is employed. As shown in FIG. 2, a bath is provided with a suction duct on one of the bath surface portions (a) and (b) in the vicinity of both ends of the strip (W), and a discharge duct (a molten metal sucked together with suspended matter) on the other. The pump is driven in a timely manner according to the bath surface condition monitored from the snout viewing window (not shown), and the suspended matter amount is managed not to stay on the plating bath surface.
[0005]
[Problems to be solved by the invention]
In hot dip plating operations, the amount of suspended matter in the snout increases temporarily, and the incidence of surface defects in the plated product may increase. This phenomenon is caused by the suspended matter adhering and depositing on the inner wall surface of the snout, and then the adhering deposit being remelted.
As shown in FIG. 4, as the plating bath surface (3 ₁ ) descends from the position (a) of the chain line (the plating bath is gradually consumed as the plating operation progresses), the suspended matter on the bath surface becomes a snout. It adheres (D) to the inner wall surface of (2).
[0006]
After the plating bath surface level is lowered as described above, the plating bath comes into contact with the deposit (D) when the plating bath surface rises (supplement of molten metal bath), and the deposit (D) is re-dissolved. The amount of suspended matter increases rapidly. This sudden increase in suspended matter (F) cannot be dealt with by a snout pump alone, and the frequency of contamination (attachment) of the material to be plated by the suspended matter (F) increases, resulting in an increased incidence of surface defects in the plated product. To do.
The present invention provides an improved snout to overcome the above problems in continuous molten metal plating operations.
[0007]
[Means for Solving the Problems]
The snout of the continuous molten metal plating apparatus of the present invention is ZrO ₂ : 6 as a protective film that suppresses and prevents the adhesion of suspended matter on the inner wall surface of the region in contact with the plating bath at the lower end immersed in the molten metal plating bath. _{~30mass%, SiO 2: 30~40mass%} , CaO: contains 30~55mass%, inevitable impurities has a structure covered by providing a thermal spray coating of ceramics is less than 15 mass%.
[0008]
In the snout of the present invention, the surface of a required region is coated with a ceramic film (which blocks contact between the snout base material and the molten metal), so that the amount of floating matter that accompanies vertical fluctuation of the plating bath surface (floating) (Which is caused by re-dissolution after an object adheres to the inner wall surface) is suppressed and prevented. Therefore, the plating bath surface (3 ₁ ) is kept in a clean state with a small amount of suspended matter by performing timely discharge operation of suspended matter (F) in the snout in the plating operation, resulting in suspended matter (F). Surface defects of the plated product can be suppressed and prevented.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The snout of the present invention is produced by forming a ceramic film on a required region (a portion in contact with the molten metal plating bath) on the inner surface of a cylindrical body (snout substrate) made of a heat-resistant alloy. FIG. 1 schematically shows the lower end of the snout (site immersed in the plating bath). (2 ₁ ) is a snout substrate, and (2 ₂ ) is a ceramic film covering the inner wall surface of the lower end portion.
[0010]
Grade to form the ceramic film is a Z rO ₂ -SiO _{2 -CaO-based, ZrO 2: 6~30mass%, SiO} 2: 30~40mass%, CaO: was adjusted to the composition range of 30～55Mass% Those are preferred . In addition, in order to ensure low wettability and reaction resistance to the molten metal necessary for preventing adhesion of suspended matter, inevitable impurities (TiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , MgO, HfO, etc.) are 15 mass. It is better to regulate to less than% (total amount).
[0011]
The thickness of the ceramic film is suitably in the range of about 150 to 500 μm. If it is thinner than this, the film life is poor, and on the other hand, if it is excessively thick, peeling due to the difference in thermal expansion coefficient from the snout substrate (heat-resistant cast steel) is likely to occur, and the stability is impaired.
[0012]
It is desirable to provide an undercoat and laminate the ceramic film as a top coat so as to improve the adhesion of the ceramic film to the snout substrate and to maintain the function of preventing adhesion of suspended solids stably. The undercoat can be formed as a thermal spray coating containing one or more metal components selected from Co, Cr, Ni, W, Mo and the like. The film thickness of the undercoat may be about 100 to 200 μm.
[0013]
The thermal spraying of the undercoat and ceramic coating is performed as a pretreatment according to the usual method, after surface purification (such as degreasing) and surface roughening (such as shot blasting) are performed on the target area of the surface of the snout substrate. A method (oxygen / acetylene combustion flame spraying, arc spraying, plasma spraying, etc.) may be used.
[0014]
The thermal sprayed ceramic coating has poor surface smoothness. Finishing the coating surface to be smooth is effective in enhancing the effect of preventing adhesion of suspended matters, and it is preferable to finish the surface with a surface roughness of Ra of about 6 μm or less and Rmax of about 18 μm or less.
[0015]
The snout substrate (2 ₁ ) of the present invention may be formed by connecting a plurality of appropriate heat-resistant cast steel cylinders as in the prior art, and the formation of an undercoat and a ceramic film by thermal spraying. May be performed on the inner wall surface of the lowermost snout substrate (2 ₁ ) in contact with the plating bath, with the region including the vertical fluctuation width (for example, ± 100 mm) of the bath surface as a target.
[0016]
【Example】
Pretreatment (cleaning and roughening) of the inner surface at the lower end of the snout substrate (heat-resistant cast steel, equivalent to SCH12), and after laminating the undercoat and ceramic coating by plasma spraying and finishing machining of the ceramic coating surface A test snout is prepared and used for an actual machine use test of a continuous molten aluminum plating line.
The sample snout 1 is a reference example ( using CaO—SiO ₂ ceramics for the top coat ), and the sample snout 2 is an invention example ( using ZrO ₂ —SiO ₂ —CaO ceramics for the top coat ).
[0017]
(1) Snout production
(1.1) Test snout 1
(1) Undercoat (alloy film)
Composition (mass%): Cr 25%, Ni 5%, W 10%, Co balance film Thickness: 150 μm
( ₂ ) Top coat (CaO-SiO ₂ ceramic film)
Composition (mass%): CaO 44%, SiO ₂ 54% (impurity 2%)
Film thickness: 250 μm
Surface roughness: Ra 3 μm, Rmax 18 μm
[0018]
(1.2) Test Snout 2
(1) Undercoat (alloy film)
Composition (mass%): Cr 8.5%, Mo 29%, Co balance film Thickness: 150 μm
( ₂ ) Top coat (ZrO ₂ —SiO ₂ —CaO based ceramic coating)
Composition (mass%): ZrO ₂ 25%, SiO ₂ 30%, CaO 43%, (impure content 2%)
Film thickness: 200 μm
Surface roughness: Ra 4 μm, Rmax 18 μm
[0019]
(2) Practical use test plating bath composition: Al-9% Si bath temperature 650 ± 20 ° C
Material to be plated: Cold rolled carbon steel sheet (sheet width 800 x sheet thickness 0.8, mm)
The suspended matter (F) generated on the bath surface in the snout was appropriately discharged by a snout pump (a suction duct and a discharge duct were arranged at positions a and b in FIG. 2).
[0020]
Table 1 shows the operation results of the molten aluminum plating. The comparative example is the result of operation using the conventional snout (same as that of the invention example and the reference example except that it does not have a ceramic coating) (the discharge operation of the suspended matter by the snout pump is the same condition as the invention example and the reference example) Implemented).
[0021]
[Table 1]

[0022]
As shown in the table, in the comparative example, the amount of suspended matter in the snout increases rapidly when the bath surface rises, while in the invention example, there is almost no change in the amount of suspended matter, and a good bath surface state with less suspended matter is stable. Is maintained. This difference is due to the fact that suspended matter adheres to the inner wall surface of the snout in the comparative example, whereas the adhesion phenomenon of suspended matter is suppressed and prevented as an effect of the ceramic film in the inventive example. The effect of preventing adhesion of suspended solids in the inventive example is clearly shown in the difference in the surface state of the inner wall surface of the snout after use. As described above, the invention example prevents the adhesion of suspended matter on the inner wall surface of the snout, and maintains the plating bath surface with less suspended matter. As a result, the incidence of surface defects in the product-plated steel sheet is greatly reduced to half that of the comparative example. ing. The effect of preventing product surface defects in the invention example exceeds that of the reference example (sample snout 1).
[0023]
【The invention's effect】
The snout of the present invention is produced by the rapid increase in the amount of suspended matter on the plating bath surface (the suspended matter adhering to the inner wall surface is re-dissolved as the bath surface rises) by preventing the suspension from adhering to the inner wall surface. ) Is prevented beforehand. Therefore, in the molten metal plating operation performed using the snout of the present invention, by appropriately performing the external discharge of the suspended matter by a pump or the like, the plating bath surface in the snout is stably maintained in a state with less suspended matter, It is possible to suppress and prevent surface defects of the plated product caused by the suspended matter. In addition, as the effect of preventing adhesion of suspended matter, the repair frequency of the snout is reduced and the service life is improved, so that the effects of reducing maintenance and improving the efficiency of the molten metal plating line can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a main part of a snout according to the present invention.
FIG. 2 is a perspective view schematically showing the vicinity of the plating bath surface inside the snout.
FIG. 3 is a front view schematically showing a plating apparatus section of a continuous molten metal plating line.
FIG. 4 is an explanatory cross-sectional view showing vertical fluctuations of the plating bath surface in the snout and the state of adhesion of floating substances on the inner wall surface of the snout.
[Explanation of symbols]
1: Annealing furnace 2: Snout 2 ₁ : Ceramic film 3: Molten metal plating bath (plating bath)
3 ₁ : Bath surface 4: Sink roll F: Floating matter (Dross)
D: Deposit W: Plated material (strip)
a, b: Snout pump duct opening position (suction port, discharge port)

Claims (4)

In snout immersed lower end portion in a molten metal plating bath, in a region in contact with the molten metal of the inner wall _{thereof, ZrO 2: 6~30mass%, SiO} 2: 30~40mass%, CaO: containing 30～55Mass% In addition, the insolubility of a continuous molten metal plating apparatus in which a ceramic sprayed coating having an inevitable impurity content of 15 mass% or less is formed. The continuous coating according to claim 1 , wherein a thermal spray coating comprising one or more metal components selected from Co, Cr, Ni, W, and Mo is used as an undercoat, and a ceramic thermal spray coating is formed thereon as a top coat. Snout of molten metal plating equipment.     The thickness of the thermal spray coating of ceramics is 150-500 micrometers, Snout of the continuous hot metal plating apparatus of Claim 1 or Claim 2.   The thickness of an undercoat is 100-200 micrometers, Snout of the continuous molten metal plating apparatus of Claim 2 or Claim 3.

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