JP2016040065A - Method of manufacturing cold-rolled steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a cold-rolled steel strip, which can reduce scale remaining on a surface of the cold-rolled steel strip after a polishing step, and which can suppress a deterioration in corrosion resistance of the cold-rolled steel strip after polishing.SOLUTION: In at least final polishing, a surface of a cold-rolled steel strip is polished by using a granular elastic body polishing belt 31 that comprises a belt body 300, a plurality of granular elastic bodies 310 provided on a surface of the belt body 300 and a plurality of abrasive grains 301 adhering to an outer surface of each granular elastic body 310.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for manufacturing a cold-rolled steel strip in which the surface of the cold-rolled steel strip is polished a plurality of times.

  As a method for manufacturing this type of cold-rolled steel strip that has been conventionally used, for example, a method for manufacturing a cold-rolled steel strip shown in Patent Document 1 below is used. That is, in the conventional configuration, a plurality of polishing stands each having a polishing belt are arranged in series, and the surface of the cold-rolled steel strip is polished by each polishing stand. The polishing belt of each polishing stand has a belt main body and a plurality of abrasive grains directly attached to the belt main body.

JP 2000-5996 A

  In the conventional cold rolled steel strip manufacturing method as described above, the surface of the cold rolled steel strip is polished only by a polishing belt having a belt main body and a plurality of abrasive grains directly attached to the belt main body. Therefore, the following problems may occur. That is, in the above-described polishing belt, the crushed abrasive grains and the polishing rods removed from the surface of the cold-rolled steel strip may be clogged between the abrasive grains (that is, clogging may occur). ). Thus, when the polishing bar or the like is clogged between the abrasive grains, the contact area between the surface of the cold rolled steel strip and the polishing belt increases, and the surface temperature of the cold rolled steel strip is higher than the assumed temperature due to frictional heat. Thus, a scale (oxide film) may be formed on the surface of the cold rolled steel strip. Such scale formation is also called polishing burn. When scale occurs on the surface of the cold-rolled steel strip, the formation of a passive film is hindered at the position where the scale exists, resulting in a situation where the corrosion resistance deteriorates.

  The present invention has been made in order to solve the above-described problems, and its purpose is to reduce the scale remaining on the surface of the cold-rolled steel strip after the polishing step, and to cold-rolled steel after polishing. It is providing the manufacturing method of the cold-rolled steel strip which can suppress the corrosion-resistant fall of a strip.

  A method for manufacturing a cold-rolled steel strip according to the present invention is a method for manufacturing a cold-rolled steel strip including a polishing step for polishing the surface of the cold-rolled steel strip a plurality of times, at least in the final polishing, The surface of the cold-rolled steel strip is formed by using a granular elastic body polishing belt having a plurality of granular elastic bodies provided on the surface of the belt body and a plurality of abrasive grains attached to the outer surface of each granular elastic body. Grind.

  According to the method for producing a cold rolled steel strip of the present invention, since the surface of the cold rolled steel strip is polished at least in the final polishing using the granular elastic abrasive belt, the surface of the cold rolled steel strip after the polishing step The remaining scale can be reduced, and the corrosion resistance of the cold-rolled steel strip after polishing can be suppressed.

It is a block diagram which shows the grinding | polishing equipment for enforcing the manufacturing method of the cold rolled steel strip by Embodiment 1 of this invention. It is a block diagram which shows the grinding | polishing surface of the direct adhesion grinding | polishing belt contained in the grinding | polishing belt of FIG. It is a block diagram which shows the grinding | polishing surface of the granular elastic body grinding | polishing belt contained in the grinding | polishing belt of FIG. It is a graph which shows the relationship between the use time of the granular elastic body polishing belt of FIG. 3, and the corrosion resistance of a cold-rolled steel strip.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing a polishing facility for carrying out a method of manufacturing a cold-rolled steel strip according to Embodiment 1 of the present invention. In the figure, the polishing equipment is equipment for carrying out a polishing process for polishing the surface of the cold rolled steel strip 1 a plurality of times, along the line direction 1a along which the cold rolled steel strip 1 before polishing is conveyed. A plurality of polishing stands 2 arranged in series are included. The polishing stand 2 includes first to fourth polishing stands 2a to 2d provided in order from the upstream side along the line direction 1a.

  The first to fourth polishing stands 2a to 2d are provided with a polishing belt 3, an idle roll 4, a contact roll 5, and a billy roll 6, respectively. The polishing belt 3 is an endless belt body and is wound around the idle roll 4 and the contact roll 5 so as to be circulated. The billy roll 6 is a roller disposed below the contact roll 5 and supports the cold-rolled steel strip 1 in the first to fourth polishing stands 2a to 2d. That is, in the first to fourth polishing stands 2 a to 2 d, when the cold rolled steel strip 1 passes between the contact roll 5 and the billy roll 6, the polishing surface of the polishing belt 3 is placed on the cold rolled steel strip 1. Are in sliding contact. Although not shown, a cooling oil for cooling the cold rolled steel strip 1 and the polishing belt 3 is supplied to a contact position between the cold rolled steel strip 1 and the polishing belt 3.

  Next, FIG. 2 is a configuration diagram showing a polishing surface of a directly attached polishing belt 30 included in the polishing belt 3 of FIG. In the figure, the direct adhesion polishing belt 30 includes a belt main body 300, a plurality of abrasive grains 301, and an adhesive 302.

  The belt main body 300 is an endless belt-like member made of cloth or paper. The abrasive grains 301 are hard members for polishing the surface of the cold-rolled steel strip 1, and are composed of, for example, alumina abrasive grains, SiC abrasive grains, or the like. The abrasive grains 301 are directly attached to the front surface of the belt main body 300 by an adhesive 302. That is, the directly attached polishing belt 30 means the polishing belt 3 in which the abrasive grains 301 are directly attached to the surface of the belt main body 300, unlike a granular elastic polishing belt 31 described later.

  Next, FIG. 3 is a configuration diagram showing a polishing surface of the granular elastic polishing belt 31 included in the polishing belt 3 of FIG. In addition, the same code | symbol is attached | subjected and demonstrated about the structure equivalent to or corresponding to the direct adhesion grinding | polishing belt 30 demonstrated using FIG. The granular elastic body polishing belt 31 includes a belt main body 300, a plurality of granular elastic bodies 310, a plurality of abrasive grains 301, and an adhesive 302.

  The belt main body 300 is an endless belt-like member made of cloth or paper. The granular elastic body 310 is formed by, for example, an elastic body such as cork in a granular form, and is attached to the surface of the belt main body 300 by an adhesive 302. The abrasive grains 301 are hard members for polishing the surface of the cold rolled steel strip 1, and are attached to the outer surface of the granular elastic body 310 by an adhesive (not shown). That is, the granular elastic body polishing belt 31 means the polishing belt 3 in which the abrasive grains 301 are attached to the surface of the belt main body 300 via the granular elastic body 310.

  As the abrasive grains 301, SiC abrasive grains having good crushability are preferably used, but other abrasive grains such as alumina abrasive grains and zirconia can also be used. The particle diameter of the granular elastic body 310 is about 2 mm, whereas the particle diameter of the abrasive grains 301 is about 50 μm to 1 mm.

  In the above description, the granular elastic body 310 is described as being adhered to the belt main body 300 by the adhesive 302. However, when the belt main body is made of the same material as the granular elastic body, the belt main body is granular elastic. It may be provided integrally with the body.

The granular elastic body polishing belt 31 has the following characteristics.
That is, the granular elastic body 310 is compressed when pressed against the cold rolled steel strip 1 and is restored when released from being pressed against the cold rolled steel strip 1 by circulation of the granular elastic polishing belt 31. Is done. It is conceivable that the abrasive grains 301 and the abrasive wrinkles removed from the surface of the cold-rolled steel strip 1 are clogged between the abrasive grains 301 by the polishing with the abrasive grains 301. It is considered that polishing wrinkles and the like can be removed from between the abrasive grains 301 by the vibration caused by That is, the polishing belt 3 of the present embodiment can prevent clogging of the polishing belt 3, and cold rolling can be performed by increasing the contact area with the surface of the cold rolled steel strip 1 and increasing frictional heat. It has the characteristic that it can avoid that the surface temperature of the steel strip 1 becomes higher than an assumed temperature.
Further, the pressing force of the abrasive grains 301 against the cold rolled steel strip 1 is appropriately adjusted by the elasticity of the granular elastic body 310. That is, the polishing belt 3 of the present embodiment has a pressing force reduced as compared with the direct adhesion polishing belt, so that the surface temperature of the cold-rolled steel strip 1 is less likely to increase than when the direct adhesion polishing belt is used.

  Returning to FIG. 1, the granular elastic body polishing belt 31 is used in at least the fourth polishing stand 2d. That is, in the method for manufacturing the cold rolled steel strip 1 according to the embodiment of the present invention, the surface of the cold rolled steel strip 1 is polished using the granular elastic body polishing belt 31 at least in the final polishing. By comprising in this way, it is avoided that the surface temperature of the cold-rolled steel strip 1 becomes higher than an assumed temperature after the final polishing, and a scale (oxide film) is formed on the surface of the cold-rolled steel strip 1 after the final polishing. It is avoided that it is formed. Thereby, the scale remaining on the surface of the cold rolled steel strip 1 after the polishing step can be reduced, and the corrosion resistance of the cold rolled steel strip 1 can be improved.

  The number of stages of the polishing stand 2 using the granular elastic body polishing belt 31 is appropriately changed according to the required polishing amount of the cold-rolled steel strip 1 or the like.

Next, an example is given. The inventor manufactured the cold-rolled steel strip 1 under the conditions shown in Tables 1 and 2 below.

  In Table 1, “direct adhesion” indicates that the direct adhesion polishing belt 30 is used as the polishing belt 3, and “granular elastic body” indicates that the granular elastic body polishing belt 31 is used as the polishing belt 3. Yes. Further, “# 120” and the like indicate the count of the abrasive grains 301 used in each polishing belt 3. Alumina is used as the abrasive grains 301 of the directly attached polishing belt 30. The granular elastic body polishing belt 31 uses cork as the granular elastic body 310 and SiC as the abrasive grains 301.

  The corrosion resistance test was performed by CCT (Cyclic Corrosion Test) determination. CCT judgment is the corrosion resistance of spraying salt water on the test piece, drying the test piece, and placing the test piece in a wet environment repeatedly, and then evaluating the degree of rusting by comparison with a standard sample. It is a judgment. The salt spray was carried out by spraying 35 ° C. salt water containing 5% by weight of NaCl over the entire test piece for 15 minutes. Drying was performed by blowing hot air of 60 ° C. over the entire test piece. The standing in a humid environment was performed by leaving the test piece in an environment of 95% RH and 50 ° C. for 3 hours. These salt spray, drying, and standing in a wet environment were repeated 20 times, and then compared with a standard sample by visual observation. The standard sample was prepared in five stages for each degree of rusting. The standard sample in the first stage has a corrosion area area ratio of 20% or more, and the standard sample in the second stage has a corrosion area area ratio of less than 20% and 10% or more. The standard sample in the stage has an area ratio of the corrosion area of less than 10% and 5% or more, and the standard sample in the fourth stage has an area ratio of the corrosion area of less than 5%. The standard sample of the sample shows almost no corrosion. “4.0” and “2.0” in Table 1 indicate that the results of the corrosion resistance test were comparable to the standard samples in the fourth and second stages. Moreover, “4.5” in Table 1 indicates that the result of the corrosion resistance test was between the fourth-stage standard sample and the fifth-stage standard sample.

  No. in Table 1 As in the second and fourth embodiments, when the cold-rolled steel strip 1 is polished by using the directly attached polishing belt 30 in the fourth polishing stand 2d, the corrosion is increased and the corrosion resistance of the cold-rolled steel strip 1 is deteriorated. It was. On the other hand, no. As in the first and third embodiments, when the cold rolled steel strip 1 is polished by using the granular elastic body polishing belt 31 in the fourth polishing stand 2d, the cracking is suppressed and the corrosion resistance of the cold rolled steel strip 1 is reduced. It was getting better. From this result, the superiority of polishing the cold-rolled steel strip 1 using the granular elastic body polishing belt 31 at least in the fourth polishing stand 2d, that is, at least in the final polishing was confirmed.

  Next, FIG. 4 is a graph showing the relationship between the usage time of the granular elastic body polishing belt 31 of FIG. 3 and the corrosion resistance of the cold rolled steel strip 1. As shown in FIG. 4, the granular elastic body polishing belt 31 having a usage time of less than 50 minutes, less than 100 minutes, less than 150 minutes, less than 200 minutes and more than 200 minutes is used depending on the usage time of the granular elastic body polishing belt 31. Changes in the corrosion resistance of the cold rolled steel strip 1 were investigated. As a result, a good CCT determination result could be obtained even with the granular elastic body polishing belt 31 exceeding 200 minutes.

  In such a method of manufacturing the cold-rolled steel strip 1, the surface of the cold-rolled steel strip 1 is polished using the granular elastic body polishing belt 31 at least in the final polishing. It can be avoided that the surface temperature becomes higher than the assumed temperature, and the formation of scale (oxide film) on the surface of the cold-rolled steel strip 1 after the final polishing can be avoided. Thereby, the scale remaining on the surface of the cold rolled steel strip 1 after the polishing step can be reduced, and the corrosion resistance of the cold rolled steel strip 1 can be improved.

DESCRIPTION OF SYMBOLS 1 Cold-rolled steel strip 30 Direct adhesion grinding | polishing belt 31 Granular elastic body grinding | polishing belt 300 Belt main body 301 Abrasive grain 310 Granular elastic body

Claims (2)

A method for producing a cold rolled steel strip comprising a polishing step of polishing the surface of the cold rolled steel strip multiple times,
At least in the final polishing, a granular elastic body polishing belt having a belt main body, a plurality of granular elastic bodies provided on the surface of the belt main body, and a plurality of abrasive grains attached to the outer surface of each granular elastic body is used. A method for producing a cold rolled steel strip, comprising polishing a surface of the cold rolled steel strip. In the polishing without using the granular elastic body polishing belt, the surface of the cold-rolled steel strip is polished using a direct adhesion polishing belt in which a plurality of abrasive grains are directly attached to a belt body. Item 2. A method for producing a cold-rolled steel strip according to Item 1.

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