JPH07166315A - Top roll for hot dip metal coating - Google Patents

Abstract

PURPOSE:To maintain the initial adequate crown of a top roll at all times in spite of a fluctuation in operating conditions in hot dip metal coating line. CONSTITUTION:A metallic sleeve 3 consisting of a metal different from the metal of the top roll 1 of a continuous hot dip coating line, having the coefft. of thermal expansion almost equal to the coefft. of thermal expansion of the top roll and having an excellent thermal conductivity is fitted into the roll barrel 2 of the top roll 1. Cooling medium passages 8 are spirally formed on the inner side of this sleeve from the width center of the top roll 1 toward both sides. A cooling water supply pipe 6 is connected near to the width center of these cooling medium passages 8 and discharge pipes 7 are connected to both ends in the width direction. As a result, the flatness defect, buckling, meandering, etc., of the plated steel strip are suppressed and the stable passage of the strip is secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a top roll which a steel strip after plating first contacts in a continuous hot dip galvanizing line.

[0002]

2. Description of the Related Art Recent surface-treated steel sheets, such as hot-dip galvanized steel sheets, are used in various fields such as household electrical appliances, building materials and automobile exterior materials because of their excellent corrosion resistance. Along with this, quality requirements from users are also increasing day by day. Especially for steel sheets for automobiles and the like, it is essential to improve the level of manufacturing technology because extremely fine surface flaws are the subject of claims.

In the continuous hot-dip galvanizing line, as shown in FIG. 4, a steel strip 32, whose mechanical properties and invasion temperature into the plating bath are adjusted in a continuous furnace 31, is provided with a plating bath 34 through a snout 33. Penetrate into the plating bath inside. The steel strip 32 that has penetrated into the plating bath is changed in direction by a pass orbiting roll 35 called a non-driving sink roll that is immersed in the plating bath, and is lifted above the plating bath.
With respect to the steel strip 32 pulled up from the plating bath, the amount of the plated metal adhered is adjusted by the wiping nozzle 36. Next, the steel strip 32, in which the amount of the plated metal adhered is adjusted, is cooled by a cooling device 38 by air or steam without passing through a heating furnace 37 for alloying treatment, and the top roll 39 is passed. After passing through the cooling device 40 to be air-cooled, the water-cooled tank 41 is immersed and cooled.

In the above continuous hot-dip galvanizing line, many process rolls are used for passing the strip of plated steel strip, and a predetermined initial crown is given to those rolls for stable strip passing. Is common. Of the above process rolls, the top roll is given an initial crown for stable threading as described above, but since plated steel strips with various temperatures, strip widths and strip thicknesses are conveyed, Thermal crown is generated. As a result, in the top roll, the contact between the roll surface and the steel strip becomes incomplete, and the flattening of the steel strip (ear wave / medium stretch) and meandering occur.

As measures against this, conventionally, the roughness of the surface of the top roll is changed, the roll is cooled, and the like. As a conventional method of suppressing the thermal crown in the top roll, a method of suppressing the thermal crown by cooling the roll with water is known. As a method for cooling this roll, as shown in FIG. 5, an internal penetration type in which the cooling water 52 is introduced from one side of the top roll 51 and led out to the opposite side, as shown in FIG. A type in which 62 is introduced to flow out from the central portion of the top roll 61 to both sides, or as shown in FIG.
A type is adopted in which the cooling water 72 is introduced from one of the top rolls 71, passes through in a spiral shape, and flows out to the opposite side. The temperature gradient and thermal crown in each of the methods shown in FIGS. 5 to 7 are as shown in FIGS. 8 to 10.

Further, in order to suppress the roll heat crown and maintain the surface roughness, the plated steel sheet is cooled with a cooling medium immediately before the top roll, and then the plated steel sheet is brought into contact with the top roll, The surface of the roll that is inert to the hot-dip metal and becomes fine powder due to contact wear with the rotating top roll is brought into close contact with a contact body such as blade-shaped carbon or talc that adheres the hot-roll metal to the surface of the top roll. To protect the roll surface roughness by reducing the amount of heat crown applied to the surface roll and protecting the roll surface roughness (Japanese Patent Application Laid-Open No. 51-77538). The inside is cooled, not one top roll. By rotating the steel strip by 90 degrees while cooling the steel sheet with a plurality of cooling rolls, the contact arc length between the cooling roll group and the plated steel sheet can be reduced. The Rukoto, roll - How to minimize the effect of thermal crown between the steel sheet (JP 59-18
No. 5767) has been proposed. However,
JP-A-51-77538, JP-A-59-1857
In the method disclosed in Japanese Patent Publication No. 67, it is difficult to ensure uniform cooling over the entire width of the steel strip, and uneven plating causes uneven flatness of the plated steel strip and meandering of the steel strip.

As a method of preventing the heat crown of the hearth roll, a metal sleeve of a different kind of metal and having excellent heat conductivity is fitted inside the roll barrel so as to prevent the heat from rolling in the axial direction of the roll barrel. A method of accelerating heat transfer to mitigate the temperature gradient and suppress the generation of roll heat crown at the contact portion between the steel plate and the roll (JP-A-4-56733).
No.) is proposed.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The hearth roll disclosed in No. 33 promotes axial heat transfer in the roll barrel to mitigate the temperature gradient and holds the contact portion between the steel plate and the roll at the same temperature as the steel plate to suppress the occurrence of roll heat crown. However, when heat is removed by cooling like a top roll, the temperature gradient between the roll and the plated steel strip is large and a thermal crown is likely to occur, which is difficult to apply.

An object of the present invention is to propose a top roll capable of always maintaining an initial proper crown in a hot dip galvanizing line even if the operating conditions change.

[0010]

[Means for Solving the Problems] The present inventors have conducted various test studies in order to achieve the above object. As a result, the main cause of the thermal crown generation in the top roll is the temperature gradient in the width direction of the top roll body, and this temperature gradient in the width direction has almost the same coefficient of thermal expansion inside the roll barrel of the top roll. A metal sleeve that is a different type of metal and has excellent thermal conductivity is fitted to promote axial heat transfer in the roll barrel, and a cooling medium spirally inside from the widthwise center of the top roll to both sides. It was clarified that the temperature gradient in the width direction of the top roll can be suppressed to the minimum by flowing the.

That is, according to the present invention, in a top roll of a continuous hot dip galvanizing line, a metal sleeve, which is made of a different kind of metal having substantially the same coefficient of thermal expansion and is excellent in heat conductivity, is fitted inside the roll barrel of the top roll, A cooling medium passage is formed in a spiral shape from the widthwise center of the top roll toward both sides, and a cooling water supply pipe is connected near the widthwise center of the cooling medium passage and discharge pipes are connected at both widthwise ends. It is a characteristic top roll for continuous hot dip plating.

[0012]

In the present invention, by fitting a metal sleeve of different metals having substantially the same coefficient of thermal expansion and having excellent thermal conductivity inside the roll barrel of the top roll,
Heat transfer in the roll axis direction is promoted and the temperature gradient is relaxed. Further, a cooling medium passage is formed in a spiral shape from the widthwise center of the top roll toward the inside, and a cooling water supply pipe is connected near the widthwise center of the cooling medium passage and discharge pipes are connected at both widthwise ends. As a result, the central part of the roll that receives the largest amount of heat is cooled, and the temperature in the width direction of the roll can be made uniform. By the synergistic effect of relaxing the temperature gradient by promoting heat transfer in the roll axial direction and homogenizing the temperature in the roll width direction by cooling from the center of the roll that receives the largest amount of heat, the occurrence of thermal crown is suppressed, and the plating It is possible to prevent the flatness failure and the meandering of the plated steel strip due to the uneven cooling in the width direction of the steel strip, and it is possible to stably pass the plated steel strip.

In the present invention, the roll barrel of the top roll, that is, the material of the outer sleeve and the material of the inner sleeve are different kinds of metals having substantially the same thermal expansion coefficient, and the inner sleeve is a metal having a higher thermal conductivity than the outer sleeve. As long as it is configured, it is not particularly limited, but as shown in Table 1, for example, stainless steel and copper, which are different kinds of metals having substantially the same thermal expansion coefficient, and copper having excellent thermal conductivity are used as the inner sleeve. By using it, it is possible to suppress the generation of thermal stress that induces creep and the like, and promote the heat transfer in the roll axial direction to relax the temperature gradient. Further, the supply of the cooling medium to the spiral cooling medium passage formed from the widthwise center of the top roll toward the both ends inside the top roll, by supplying the cooling medium from the both ends of the top roll to the widthwise center, The cooling medium sequentially passes through the spiral cooling medium passages formed from the center in the width direction toward both ends, and is cooled from the central portion of the roll that receives the largest amount of heat, so that the temperature in the roll width direction can be made uniform. it can. The cooling medium used is not particularly limited as long as it can cool the outer sleeve via the inner sleeve, but water is generally used.

[0014]

[Table 1]

[0015]

【Example】

Embodiment 1 Hereinafter, details of the present invention will be described with reference to FIGS. 1 to 3 showing an embodiment. 1 is a vertical cross-sectional view of a top roll of the present invention, FIG. 2 is a partial cross-sectional view for explaining a multi-layer structure of the top roll of the present invention, and FIG. 3 is an explanatory view of a thermal crown generation state of the top roll, (A) is the case of the conventional top roll, (b) is the case of the top roll of this invention. 1 and 2, reference numeral 1 is a top roll, which is a top roll barrel (hereinafter referred to as an outer sleeve).
A metal inner sleeve 3 having a coefficient of linear expansion substantially equal to that of the outer sleeve 2 and an excellent heat transfer coefficient is attached to the inner side of the second sleeve 2 by shrink fitting or the like. Reference numeral 4 denotes a plated steel strip, which is conveyed along the outer sleeve 2 of the top roll 1 with its traveling direction turned by 90 °. As shown in FIG. 3B, both ends of the inner sleeve 3 are located inside the inner side surface of the outer sleeve 2 to separate them from each other. The separation distance between the two is not particularly limited, but the separation distance is for blocking the flow of heat, and is not limited as long as the action and effect thereof are secured, but 1 mm is generally sufficient.

Reference numeral 5 denotes a roll shaft of the top roll 1, on both ends of which a cooling water supply pipe 6 for supplying cooling water and a discharge pipe 7 for discharging the cooling water are fitted. Reference numeral 8 denotes a spiral cooling water passage formed on the inner surface of the inner sleeve 3 of the top roll 1. The cooling water passage 8 is divided into two parts at the center of the top roll 1 in the width direction, and a cooling water supply pipe 6 is provided near the center of the width direction via a communication pipe 9. Cooling water is supplied from the top roll 1 through the spiral cooling water passage 8 from the center of the top roll 1 in the width direction, and is discharged from both ends to the discharge pipe 7 through the communication pipe 10.

With the above construction, the top roll 1 uses a metal having a coefficient of linear expansion substantially equal to that of the outer sleeve 2 and an excellent heat transfer coefficient for the inner sleeve 3, so that the temperature in the width direction is not affected. Uniformity is rapidly diffused and homogenized. Further, by disposing both ends of the inner sleeve 3 apart from the inner surface of the outer sleeve 2, the plated steel strip 4 can be conveyed under the same conditions without being affected by heat from the inner surface of the outer sleeve 2. Even so, the heat transfer in the width direction of the top roll 1 is promoted, and the temperature gradient is relaxed. Moreover,
The spiral cooling water passage 8 formed on the inner surface of the inner sleeve 3 is supplied with the cooling water from the cooling water supply pipe 6 through the communication pipe 9 in the vicinity of the center of the top roll 1 in the width direction, and the spiral cooling is sequentially performed. By being discharged from the discharge pipe 7 from both ends via the water passage 8 and the communication pipe 10, it is cooled from the central portion of the roll which receives the largest amount of heat from the plated steel strip 4, and the width direction of the top roll 1 is reduced. It is possible to make the temperature uniform. In the top roll 21 of the conventional structure shown in FIG. 3A, a heat gradient CRS occurs due to heat absorption from the plated steel strip 22 and particularly in the vicinity of both ends of the plated steel strip 22. The top roll 1 of this invention is
Due to the synergistic effect of promoting the heat transfer in the width direction by the inner sleeve 3 and equalizing the temperature in the width direction by the cooling water in the spiral cooling water passage 8, as shown in FIG. It is mitigated and the occurrence of thermal crown CRS is prevented. In addition, [CRS] in FIG. 3 represents a thermal crown per coated steel strip width. The thickness of the inner cylinder is not particularly limited, but a thicker one than the outer cylinder is preferable for improving the thermal conductivity.

Example 2 As shown in Table 2, the roll of the present invention shown in FIG. 1 having a crown amount of 2.0 mm, the outer cylinder of which is made of stainless steel having a wall thickness of 25 mm and the inner cylinder of which is made of copper having a wall thickness of 20 mm; 30m
The amount of crown made of stainless steel of 2.0m
The normal roll shown in FIG. 6 of m is disposed as the top roll of the continuous hot-dip galvanizing line, the thickness of the plated steel strip immediately before the top roll is 350 ° C., the wall thickness is 0.8 mm, and the plate width is 120.
A line speed of 100 m / m for a 0 mm plated steel strip while cooling the top roll with cooling water at a temperature of 25 ° C.
While being conveyed in, the heat crown in the width direction of the top roll was measured, and the meandering amount of the plated steel strip was measured. The results are shown in Table 3.

[0019]

[Table 2]

[0020]

[Table 3]

As shown in Table 3, the use of the top roll according to the present invention makes it possible to suppress the generation of thermal crown in the width direction of the top roll,
As a result, it was possible to prevent the flatness failure and the meandering of the plated steel strip due to the uneven cooling of the plated steel strip in the width direction, and it was possible to pass the plated steel strip stably. On the other hand, when a normal roll is used, it is 5 in the width direction of the top roll.
A heat crown of 0 to 70 μm is generated, and due to uneven cooling in the width direction of the plated steel strip, 30 to 50 mm is applied to the coated steel strip.
It was impossible to stably pass the plated steel strip.

[0022]

As described above, the top roll of the present invention can suppress the thermal crown at a low cost and without control, thereby suppressing the flatness failure of the plated steel strip, buckling and meandering. This makes it possible to carry out stable threading, which is a great advantage for the industry.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a top roll of the present invention.

FIG. 2 is a partial cross-sectional view for explaining the multilayer structure of the top roll of the present invention.

3A and 3B are explanatory views of a generation state of a thermal crown of a top roll, in which FIG. 3A shows a conventional top roll, and FIG. 3B shows a top roll of the present invention.

FIG. 4 is a schematic system diagram of a continuous hot dip galvanizing line.

FIG. 5 is a schematic view showing an example of a conventional top roll cooling system.

FIG. 6 is a schematic view showing another example of a conventional top roll cooling system.

FIG. 7 is a schematic view showing another example of a conventional top roll cooling system.

8 is a graph showing the relationship between the distance from the center of the plated steel strip, the temperature, and the amount of radial crown when the top roll of FIG. 5 is used.

9 is a graph showing the relationship between the distance from the center of the plated steel strip, temperature, and the amount of radial crown when the top roll of FIG. 6 is used.

10 is a graph showing the relationship between the distance from the center of the plated steel strip, the temperature, and the amount of radial crown when the top roll of FIG. 7 is used.

[Explanation of reference symbols] 1, 21, 39, 51, 61, 71 Top roll 2 Outer sleeve 3 Inner sleeve 4, 22 Plated steel strip 5 Roll shaft 6 Cooling water supply pipe 7 Discharge pipe 8 Cooling water passage 9, 10 Communication pipe 31 Continuous Furnace 32 Steel Strip 33 Snout 34 Plating Tank 35 Pass Orbital Roll 36 Wiping Nozzle 37 Heating Furnace 38, 40 Cooling Device 41 Water Cooling Tank 52, 62, 72 Cooling Water

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshiro Matsumoto, Yoshiro Matsumoto, 5-1-1109, Shimaya, Konohana-ku, Osaka City, Osaka Prefecture Sumitomo Metal Industries, Ltd. (72) Yoshiyuki Souda 4 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture 5-33, Sumitomo Metal Industries, Ltd.

Claims (1)

[Claims] 1. In a top roll of a continuous hot dip galvanizing line, a metal sleeve having different thermal expansion coefficients and having excellent thermal conductivity is fitted inside the roll barrel of the top roll, and the top roll is placed inside. A cooling medium passage is formed in a spiral shape from the center of the
A top roll for continuous hot dip plating, characterized in that a cooling water supply pipe is connected near the center of the cooling medium passage in the width direction and discharge pipes are connected at both ends in the width direction.