Title of the invention: Pass roll for hot-dip galvanized steel sheet manufacturing equipment, hot-dip galvanized steel sheet manufacturing facility and hot-dip galvanized steel sheet manufacturing method
Technical field
[0001]
　The present invention relates to a manufacturing facility for a hot-dip galvanized steel sheet.
Background technology
[0002]
　In a hot-dip galvanized steel sheet manufacturing facility, the steel strip is galvanized by immersing it in a galvanized bath. In the hot-dip galvanized steel sheet manufacturing facility, in order to achieve both miniaturization of the facility and securing of processing time for each treatment applied to the steel strip, a plurality of rolls (hereinafter, “pass roll”) along the steel sheet manufacturing line are used. Is provided. The steel strip discharged from the coil is sent to the downstream side via a pass roll so as to be folded back many times on the steel sheet production line.
[0003]
　When the steel strip comes into contact with the pass roll, microslip may occur between the steel strip and the pass roll. This microslip causes the zinc plating layer to peel off from the surface of the steel strip, and the peeled zinc adheres to the pass roll. Zinc adhering to the pass roll may adhere to the surface of the subsequent steel strip or generate indentations, which causes poor quality. In this specification, the phenomenon in which zinc peeled from the surface of the steel strip adheres to the peripheral surface of the pass roll is referred to as zinc winding.
[0004]
　As a method for suppressing the occurrence of zinc winding, Patent Document 1 discloses the use of a roll made of a phenol resin based on a mineral fiber. Further, Patent Document 2 discloses that a material obtained by mixing a rubber binder and an inorganic filler with fibers having heat resistance and chemical resistance is used for the roll surface. Patent Document 3 discloses that a non-woven fabric layer composed of a base cloth made of heat-resistant fibers, a non-woven fabric made of para-aramid fibers, and a non-woven fabric made of PBO (polyparaphenylene benzobisoxazole) fibers is provided on the roll surface. Has been done.
Prior art literature
Patent documents
[0005]
Patent Document 1: Japanese Patent Application Laid-Open
No. 54-117333 Patent Document 2: Japanese
Patent Application Laid-Open No. 63-030974 Patent Document 3: Japanese Patent Application Laid-Open No. 2000-064014
Outline of the invention
Problems to be solved by the invention
[0006]
　Since the steel strip passing through the galvanizing bath is immersed in the molten zinc, the surface of the steel strip is hot on the outlet side of the galvanizing bath. Therefore, the steel strip having a high surface temperature comes into contact with the pass roll installed near the outlet side of the galvanizing bath, and the surface temperature of the pass roll rises. In this case, in the pass roll disclosed in Patent Document 1, the phenol resin is thermally decomposed, and the function of suppressing the occurrence of zinc winding of the pass roll is gradually lost. Similarly, in the pass roll disclosed in Patent Document 2, the rubber binder is thermally decomposed, and the function of suppressing the occurrence of zinc winding of the pass roll is lost. Therefore, in the pass rolls of Patent Documents 1 and 2, it is necessary to frequently perform maintenance of the pass roll in order to maintain the effect of suppressing the occurrence of zinc winding, and the productivity is lowered. Further, although the surface layer of the pass roll disclosed in Patent Document 3 is composed of PBO fibers, the effect of suppressing the occurrence of zinc winding may not be obtained depending on the pass roll manufacturing conditions and operating conditions, and the quality is good. There was room for improvement from the viewpoint of stable production of hot-dip galvanized steel sheets.
[0007]
　The present invention has been made in view of the above circumstances, and the hot-dip galvanized steel sheet is made so that the effect of suppressing the occurrence of zinc winding by the pass roll for manufacturing equipment of the hot-dip galvanized steel sheet can be obtained longer and more stably. The purpose is to improve the productivity of.
Means to solve problems
[0008]
　One aspect of the present invention for solving the above problems is a pass roll for manufacturing equipment of a hot-dip galvanized steel sheet, which has a roll body and a heat-resistant felt layer covering the roll body, and the heat-resistant felt layer is thermally decomposed. It is characterized in that the temperature is 420 ° C. or higher and the surface hardness evaluation index at 400 ° C. is more than 0.11 μm / N.
[0009]
　Further, one aspect of the present invention from another viewpoint is a hot-dip galvanized steel sheet manufacturing facility, wherein the pass roll is a roll through which a steel strip subjected to hot-dip galvanizing in a galvanized bath is passed. It is said.
[0010]
　One aspect of the present invention from yet another viewpoint is a method for producing a hot-dip galvanized steel sheet, in which a steel strip is immersed in a galvanized bath of a steel sheet production line to produce a hot-dip galvanized steel sheet, in the galvanized bath. As a pass roll through which a hot-dip galvanized steel strip is passed, the roll body is covered with a heat-resistant felt layer having a thermal decomposition temperature of 420 ° C or higher and a surface hardness evaluation index of more than 0.11 μm / N at 400 ° C. It is characterized in that the hot-dip galvanized steel sheet is manufactured using a pass roll.
Effect of the invention
[0011]
　It is possible to improve the productivity of the hot-dip galvanized steel sheet by making it possible to obtain the effect of suppressing the occurrence of zinc winding by the pass roll for the manufacturing equipment of the hot-dip galvanized steel sheet for a longer time and stably.
A brief description of the drawing
[0012]
FIG. 1 is a diagram showing a partial configuration of a hot-dip galvanized steel sheet manufacturing facility according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a schematic configuration of a pass roll according to an embodiment of the present invention.
[Fig. 3] Fig. 3 is a diagram for explaining a method for measuring a surface hardness evaluation index.
FIG. 4 is a diagram showing a partial configuration of a hot-dip galvanized steel sheet manufacturing facility according to another embodiment of the present invention.
Mode for carrying out the invention
[0013]
　Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the present specification and drawings, elements having substantially the same functional configuration are designated by the same reference numerals to omit duplicate description.
[0014]
　As shown in FIG. 1, the hot-dip galvanized steel sheet manufacturing facility 1 of the present embodiment includes a hot-dip galvanized apparatus 2 that performs a galvanizing treatment of the steel strip S. The hot-dip galvanizing apparatus 2 includes a galvanizing bath 3 in which molten zinc is stored, a pass roll 4 (hereinafter, “entry pass roll”) arranged upstream of the zinc plating bath 3 in the steel sheet production line, and a zinc plating bath. It includes a bath roll 5 arranged in 3 and a pass roll 6 (hereinafter, “outside pass roll”) arranged on the downstream side of the galvanized bath 3 of the steel sheet production line. The steel strip S travels along the steel plate production line along the direction of the arrow in FIG. 1 while changing the traveling direction via the inlet pass roll 4, the bath roll 5, and the outlet pass roll 6. Although FIG. 1 shows a part of the configuration of the hot-dip galvanized steel sheet manufacturing facility 1, the configuration on the upstream side of the galvanized bath 3 is the same as before.
[0015]
　As shown in FIG. 2, the exit side pass roll 6 installed on the downstream side of the galvanizing bath 3 is composed of a roll body 6a and a heat-resistant felt layer 6b covering the roll body 6a. The term "heat-resistant felt layer" as used herein refers to felt made of heat-resistant fibers having a thickness in the radial direction of the roll body 6a, which exists over the entire surface of the roll body 6a. Felt is a non-woven fabric defined in JIS L 0222, in which fibers are oriented in one direction or randomly, and the fibers are bonded by entanglement and / or fusion and / or adhesion. The heat-resistant felt layer 6b is provided so as to cover the entire peripheral surface of the roll body 6a, and when the steel strip S comes into contact with the exit side pass roll 6, it comes into contact with the heat-resistant felt layer 6b.
[0016]
　The method of providing the heat-resistant felt layer 6b on the surface of the roll body 6a is not particularly limited, and for example, a method of covering the roll body 6a with a felt made of tubular heat-resistant fibers and fixing the felt layer 6a, or a method of lining the surface of the roll body 6a. A method of pasting felt made of heat-resistant fibers, a felt made of heat-resistant fibers having a width equal to the total width of the roll body 6a is wound around the roll body 6a, or a felt made of heat-resistant fibers shorter than the total width of the roll body 6a is wrapped around the roll body 6a. There is a method of spirally winding around 6a. Further, the heat-resistant felt layer 6b may be composed of a single layer or a plurality of layers. In the heat-resistant felt layer having a multi-layer structure, for example, a roll body 6a covered with a tubular felt is covered with another tubular felt, or a felt having a width equal to the total width of the roll body 6a is formed on the roll body 6a. It can be obtained by stacking and wrapping.
[0017]
　The heat-resistant felt layer 6b is made of fibers having a thermal decomposition temperature of 420 ° C. or higher, which is higher than the melting point of zinc (419.5 ° C.). Since the heat-resistant felt layer 6b of the present embodiment has such a thermal decomposition temperature, the heat-resistant felt layer 6b does not thermally decompose even if the steel strip S after the galvanizing treatment comes into contact with the exit side pass roll 6. It has become. The upper limit of the thermal decomposition temperature is not particularly limited. The fiber constituting the heat-resistant felt layer 6b is not particularly limited as long as it is a heat-resistant fiber having a thermal decomposition temperature of 420 ° C. or higher, but is preferably a polyparaphenylene benzobisoxazole (PBO) fiber, for example.
[0018]
　The exit side pass roll 6 may have a multi-layer structure by providing another layer between the roll body 6a and the heat-resistant felt layer 6b. When the exit side pass roll 6 has a multi-layer structure, the heat-resistant felt layer 6b is provided on the outermost layer. It is preferable that the output side pass roll 6 has a structure in which the heat-resistant felt layer 6b is in contact with the surface of the roll body 6a in order to exert the zinc winding suppressing effect for a longer period of time even in a state where wear deterioration has progressed.
[0019]
　It is preferable that the thickness of the heat-resistant felt layer 6b is appropriately changed within the range of 1 to 20 mm depending on the equipment configuration, operating conditions, and the like. Considering the heat shrinkage of the heat-resistant felt layer 6b, it is preferable that the heat-resistant felt layer 6b is thin so that the change in roll diameter due to temperature change is small. From this viewpoint, the thickness of the heat-resistant felt layer 6b is preferably 20 mm or less. On the other hand, from the viewpoint of improving the durability of the heat-resistant felt layer 6b, the thickness of the heat-resistant felt layer 6b is preferably thick to some extent, and is preferably 1 mm or more. Therefore, the thickness of the heat-resistant felt layer 6b is preferably 1 to 20 mm. Further, from the viewpoint of improving durability, the thickness of the heat-resistant felt layer 6b is more preferably more than 5 mm.
[0020]
　As described above, the output side pass roll 6 of the present embodiment is provided with the heat-resistant felt layer 6b on the surface of the roll body 6a, so that the steel strip S after the zinc plating treatment is formed on the roll body 6a of the output side pass roll 6. It does not come into direct contact, which makes it less likely that zinc wrapping will occur. Further, since the heat-resistant felt layer 6b of the output side pass roll 6 of the present embodiment has a thermal decomposition temperature of 420 ° C. or higher, even if the steel strip S after the zinc plating treatment comes into contact with the output side pass roll 6, the heat-resistant felt layer 6b However, it does not decompose thermally, and the effect of suppressing the occurrence of zinc winding can be maintained. Therefore, the frequency of maintenance of the output side pass roll 6 can be reduced, and the operating time of the hot-dip galvanized steel sheet manufacturing facility 1 can be lengthened. This makes it possible to improve the productivity of the hot-dip galvanized steel sheet.
[0021]
　By the way, when the present inventors analyzed the surface of the pass roll in which zinc winding was generated in the conventional pass roll not provided with the heat-resistant felt layer 6b, the zinc was simply bitten into the recessed portion on the surface of the pass roll. It has been found. From this finding, it was found that zinc winding is a phenomenon that occurs when the zinc on the surface of the steel strip is scraped off by the passroll because the surface hardness of the pass roll is larger than the hardness of the zinc fixed to the surface of the steel strip. It was. That is, by making the hardness of the heat-resistant felt layer 6b smaller than the hardness of the galvanized layer on the surface of the steel strip S, it is possible to stably obtain the effect of suppressing zinc winding by the exit side pass roll 6. Become. In particular, even when the same fiber is used, the hardness of the felt differs depending on the manufacturing conditions (for example, the porosity of the felt and the method of hardening), so that the effect of suppressing the occurrence of zinc winding can be stably obtained. Therefore, it is important to specify the hardness of the heat-resistant felt layer 6b.
[0022]
　In the case of an elastic body such as felt, there is no hardness evaluation method in a high temperature state. Therefore, in order to derive a preferable hardness relationship between the heat-resistant felt layer 6b and the galvanized layer on the surface of the steel strip S, a surface hardness evaluation index is defined as a new index regarding the hardness of the heat-resistant felt layer 6b. For the measurement of the surface hardness evaluation index, for example, TMA (thermomechanical analyzer), which is an apparatus for measuring the high temperature softening point of an organic substance, is used. In TMA, it is possible to measure the amount of deformation when a probe is pressed against a sample and a non-oscillating load (constant load) is applied at a certain temperature. As shown in FIG. 3, in the present specification, the point where the tip of the probe contacts the surface of the sample is set as a reference point, the amount of change in the pushing load from the reference point of the probe is ΔF, and the amount of change in the pushing load is ΔF [ Let Δd [μm] be the amount of deformation of the sample at the position where the probe is pushed when the value becomes N]. Then, the value of Δd / ΔF [μm / N] at this time is defined as the surface hardness evaluation index. The surface hardness evaluation index means that the larger the value, the lower the surface hardness of the sample. A probe with a tip diameter of 500 μm is used, and the maximum load used for evaluation is 18 g.
[0023]
　The present inventors measured the surface hardness evaluation index of the galvanized steel sheet at 400 ° C. The galvanized steel sheet measured here is a hot-dip galvanized steel sheet (GI) before alloying, and is a type of steel sheet having the softest plating layer among the hot-dip galvanized steel sheets. The measurement results are shown in Table 1 below. Table 1 also shows a surface hardness evaluation index at 400 ° C. when PBO fibers are used as the heat-resistant felt layer 6b.
[table 1]

[0024]
　As shown in Table 1 above, the surface hardness evaluation index of the galvanized layer on the surface of the steel strip S is 0.11 μm / N. As described above, since the galvanized steel sheet in Table 1 is the type of steel sheet having the softest plating layer among the hot-dip galvanized steel sheets, other types of hot-dip galvanized steel sheets such as alloyed hot-dip galvanized steel sheets (GA) are used. In the steel sheet, the value of the surface hardness evaluation index at 400 ° C. is less than 0.11 μm / N. Therefore, the heat-resistant felt layer 6b manufactured so that the surface hardness evaluation index exceeds 0.11 μm / N becomes relatively soft with respect to the plating layer of any kind of hot-dip galvanized steel sheet. Therefore, even if the heat-resistant felt layer 6b and the steel strip S come into contact with each other, the phenomenon that zinc adhering to the surface of the steel strip S is scraped off is extremely unlikely to occur. As a result, the effect of suppressing the occurrence of zinc winding can be stably obtained, and the productivity of a high-quality hot-dip galvanized steel sheet can be improved.
[0025]
　From the viewpoint of increasing the hardness difference of the hot-dip galvanized steel sheet from the plated layer and more effectively suppressing the occurrence of zinc winding, the surface hardness evaluation index of the heat-resistant felt layer 6b is more preferably 3 μm / N or more, and 5 μm. It is more preferably / N or more. The upper limit of the surface hardness evaluation index of the heat-resistant felt layer 6b is not particularly limited. If the heat-resistant felt layer 6b is worn out and loses its function as a felt layer, the effect of suppressing zinc winding is lost. It is necessary to replace the heat-resistant felt that covers 6a. That is, the faster the wear progress rate of the heat-resistant felt layer 6b, the more frequently the heat-resistant felt is replaced. Therefore, from the viewpoint of improving productivity by slowing the progress rate of wear of the heat-resistant felt layer 6b and reducing the frequency of replacing the heat-resistant felt, the heat-resistant felt layer 6b is softer than the plating layer of the hot-dip zinc-plated steel plate. The surface hardness evaluation index of the heat-resistant felt layer 6b is preferably 100 μm / N or less so as not to be excessive. Further, the heat-resistant felt layer 6b preferably has a uniform hardness in the thickness direction so that the magnitude of the zinc winding suppressing effect does not change with wear of the heat-resistant felt layer 6b.
[0026]
　Although one embodiment of the present invention has been described above, the present invention is not limited to such an example. It is clear that a person skilled in the art can come up with various modifications or modifications within the scope of the technical idea described in the claims, and of course, the technical scope of the present invention also includes them. It is understood that it belongs to.　
[0027]
　Further, the configuration of the hot-dip galvanized steel sheet manufacturing facility 1 is not limited to that described in the above embodiment. For example, as shown in FIG. 4, an alloy in which zinc plating is alloyed on the downstream side of the galvanized bath 3 A chemical furnace 7 may be provided. In this case, since the surface of the steel strip S is in a high temperature state on the outlet side of the alloying furnace 7, the outlet path roll installed on the downstream side of the alloying furnace 7 is installed so that the effect of suppressing zinc winding is not lost by thermal decomposition. It is preferable that the thermal decomposition temperature of the heat-resistant felt layer 6b of No. 6 is 420 ° C. or higher.
[0028]
　In the above embodiment, the heat-resistant felt layer 6b is provided only on the exit side pass roll 6 of the hot-dip galvanized steel sheet manufacturing facility 1 having the hot-dip galvanizing treatment facility, but the pass roll having the heat-resistant felt layer 6b is described above. Not limited to the form, it can be applied as a pass roll through which a steel strip S hot-dip galvanized in a galvanized bath is passed. When the pass roll having the heat-resistant felt layer 6b is used as a roll for passing the hot-dip galvanized steel strip S in a galvanizing bath, the effect of suppressing zinc winding can be stably obtained. ..
Example
[0029]
　The pass roll according to the present invention was applied as a top roll installed on the downstream side of the galvanized bath, and a plate passing test was carried out for one month in a hot-dip galvanized steel sheet manufacturing facility. Although the maximum plate temperature in the plate passing test was 416 ° C., the hot-dip galvanized steel sheet could be produced without causing quality defects or manufacturing troubles on the surface of the steel sheet. PBO fiber was used as the heat-resistant felt layer, and the surface hardness evaluation index of the heat-resistant felt layer at 400 ° C. was 7.45 μm / N.
Industrial applicability
[0030]
　The present invention can be used in the production of hot-dip galvanized steel sheets.
Code description
[0031]
1 Hot-dip galvanized steel sheet manufacturing equipment
2 Hot-dip galvanized equipment　
3 Galvanized bath
4 Entering pass
roll 5 Bath roll
6 Outer pass
roll 6a Roll body
6b Heat-resistant felt layer
7 Alloying furnace
Δd Sample deformation amount
ΔF Probe pushing load Change amount of
S steel strip
The scope of the claims
[Claim 1]
　A pass
　roll for a hot-dip galvanized steel sheet manufacturing facility, which has a roll body and a
　heat-resistant felt layer covering the roll body. The heat-
　resistant felt layer has a thermal decomposition temperature of 420 ° C. or higher and a surface at 400 ° C. The hardness evaluation index is more than 0.11 μm / N.
[Claim 2]
　In the pass
　roll for manufacturing equipment of the hot-dip galvanized steel sheet according to claim 1, the heat-resistant felt layer is in contact with the surface of the roll body.
[Claim 3]
　In the pass roll for manufacturing equipment of the hot-dip galvanized steel sheet according to claim 1 or 2, the
　heat-resistant felt layer is made of polyparaphenylene benzobisoxazole fiber.
[Claim 4]
　The
　heat-resistant felt layer has a thickness of 1 to 20 mm in the pass roll for manufacturing equipment of the hot-dip galvanized steel sheet according to any one of claims 1 to 3 .
[Claim 5]

The pass roll according to any one of claims 1 to 4 in a 　hot-dip galvanized steel sheet manufacturing facility is a roll through which a steel strip subjected to hot-dip galvanizing in a galvanized bath is passed.
[Claim 6]
　It is immersed steel strip galvanizing bath of steel sheet production line for manufacturing a galvanized steel sheet, a method of manufacturing a galvanized steel sheet,
　to Tsuban a steel strip subjected to hot-dip galvanizing in the galvanizing bath The hot-dip galvanized steel sheet is manufactured as a pass roll by using a pass roll in which the roll body is covered with a heat-resistant felt layer having a thermal decomposition temperature of 420 ° C. or higher and a surface hardness evaluation index of more than 0.11 μm / N at 400 ° C. To do.　
[Claim 7]
　In the method for producing a hot-dip galvanized steel sheet according to claim 6, the
　heat-resistant felt layer is in contact with the surface of the pass roll.
[Claim 8]
　In the method for producing a hot-dip galvanized steel sheet according to claim 6 or 7, the
　heat-resistant felt layer is made of polyparaphenylene benzobisoxazole fiber.
[Claim 9]
　In the method for producing a hot-dip galvanized steel sheet according to any one of claims 6 to 8, the
　heat-resistant felt layer has a thickness of 1 to 20 mm.