JP2019155474A - Roll for rolling, surface treatment steel plate, cool rolling steel plate and production method thereof - Google Patents

Abstract

To provide a rolling roll which can be used as a temper rolling roll and/or cool rolling roll capable of temper rolling a surface treatment steel plate for producing a surface treatment steel plate comprising simultaneously, extremely excellent press molding property and preferable after-coating clarity, a production method and a temper rolling method of the surface treatment steel plate, and a surface treatment steel plate comprising extremely excellent press molding property and preferable after-coating clarity.SOLUTION: A rolling roll 10 of the invention comprises, arithmetic average roughness Ra on a roll surface (outer peripheral surface 11) which is 1-10 μm, arithmetic average undulation Wa which is 0.01-0.10 μm, and a peak number PPI for 1 inch which is 300-2000.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a roll for rolling, a surface-treated steel sheet, a cold-rolled steel sheet, and a method for producing them, and more specifically, a roll for rolling that can be suitably used for temper rolling of a surface-treated steel sheet or a cold-rolled steel sheet, and a method for producing the same. The present invention relates to a method for producing a surface-treated steel sheet, a surface-treated steel sheet excellent in press formability and post-paint clarity, a method of producing a cold-rolled steel sheet, and a cold-rolled steel sheet excellent in press formability and post-paint clarity.

  In general, there are two properties that are generally required for a steel sheet: excellent appearance and excellent formability.

  As an index that has a significant effect on the appearance of a steel sheet, the sharpness after painting of the steel sheet (sometimes simply referred to as “sharpness”) has attracted attention. The post-paint clarity is to evaluate the sharpness on the surface of the steel sheet after coating the steel sheet with a paint or the like. In particular, when steel plates are used for automobile outer panels and electrical appliances, the appearance of coated steel sheets is one of the elements that directly appeals to users, so it is desirable to ensure good post-paint clarity. It is rare.

  In addition, as a method for improving the corrosion resistance of products such as automobiles, the use ratio of surface-treated steel sheets subjected to plating treatment is increasing. Therefore, the importance of techniques for improving the post-painting sharpness of the surface-treated steel sheet is also increasing. In particular, from the viewpoint of design with an emphasis on corrosion resistance, a thick-plated steel sheet such as a hot-dip plated steel sheet is required today, and even when using such a thick-plated surface-treated steel sheet, the sharpness after painting is more important. It is thought to be.

  In addition, as a specific example of the formability that is another characteristic required for the steel sheet, press formability can be mentioned. More specifically, it is important to prevent adhesion between the mold and the steel plate (press original plate) during press molding. In particular, steel plates for automobiles are premised on being used after being press-molded into various shapes, and therefore it is desired that the steel plate has excellent press-formability.

  By the way, the improvement of the post-painting sharpness has been mainly a problem of the painting technique, and therefore, the painting method and the technique for improving the paint have been actively studied. In recent years, multi-layer coating has become widespread, increasing the number of processes in the automobile manufacturing line and contributing to an increase in cost. For this reason, more technical elucidation of the clearness after painting is required. On the other hand, the influence of the surface roughness of the steel sheet, which has been considered to have a small influence on the post-painting sharpness, has been clarified particularly in high-quality steel sheets. The following Non-Patent Documents 1 and 2 are cited as documents showing the relationship between the surface roughness of a steel sheet and the sharpness after painting.

  Non-Patent Document 1 reports the relationship between the center line average roughness of the steel sheet and the sharpness after painting. However, Non-Patent Document 1 merely states that the surface roughness of the steel sheet needs to be as small as possible in order to improve the sharpness. That is, considering only the sharpness after painting, it is optimal to make the surface of the steel plate a bright surface (a surface with extremely small surface roughness).

  However, a surface-treated steel sheet having a bright surface cannot be used as a steel sheet for press forming of a steel sheet for automobiles or the like because of its extremely poor press formability and handling property during processing. Actually, particularly in the case of a steel sheet to be subjected to press forming, a dull weight is provided to provide fine irregularities on the surface of the steel sheet for the purpose of improving the press formability and handling properties. When the dull weight is applied, the surface roughness of the steel sheet becomes large, and naturally, the sharpness is not good.

In Non-Patent Document 2, a more detailed study is made on the influence of the surface roughness of a steel sheet on the sharpness after painting. Specifically, temper rolling is performed using rolls that have been dulled by shot blasting, electrical discharge machining, and laser machining to produce steel sheets with various arithmetic average roughness Ra and PPI (peak per inch). As a result of investigating the vividness after coating with a thickness of 55 to 80 μm, the following has been clarified.
(1) The sharpness improves as Ra of the steel sheet decreases.
(2) The PPI of the steel sheet does not affect the sharpness.
(3) In the roughness pattern of the steel sheet, the waviness (surface irregularities having a long wavelength and cycle) component remains even after coating, which greatly affects the sharpness.
(4) From the simulation results of shot blasting, it is inferred that the method using shot blasting is difficult to suppress the occurrence of waviness, and the waviness remaining on the surface of the steel sheet hinders the improvement in sharpness. .
(5) In laser dull processing (dull weighting by laser processing), the wave length of waviness is determined by the size and spacing of the microcrater (recesses generated by the laser). By controlling the wavelength, it is possible to improve the sharpness while maintaining the surface roughness necessary for press working. In laser dull processing, a large number of flat portions also contributes to an improvement in sharpness.

  As described above, the press formability and sharpness of the steel sheet vary greatly depending on the surface texture of the steel sheet (particularly the form of microscopic irregularities on the surface including Ra, etc.), so that the surface texture can be appropriately controlled. is important.

  For example, in press molding, in order to prevent adhesion between a mold and a steel plate, it is necessary to improve oil retention at the interface between the mold and the steel plate. In order to improve the oil retention, it is necessary to impart an arithmetic average roughness Ra of a certain value or more to the steel sheet surface. Moreover, it is considered that the larger the peak count (PPI) is, the more effective the oil retention is.

  On the other hand, in order to improve the sharpness after painting, the long-period surface irregularities (hereinafter sometimes simply referred to as irregularities) that remain on the steel sheet surface and adversely affect the sharpness even after painting are reduced. It is necessary to.

  That is, in order to achieve both excellent press formability and good post-paint clarity, the size and number of short-period surface irregularities indicated by indices such as Ra and PPI are increased, and indices such as Wa It is required to reduce the size and number of the long-period surface irregularities indicated by. However, since the short-period irregularities and the long-period irregularities on the steel sheet surface have a positive correlation, it is difficult to control only one of them to be larger or smaller.

  In addition to Non-Patent Documents 1 and 2, Patent Document 1 discloses a technique for improving the sharpness after painting. In Patent Document 1, as a roll for temper rolling for producing a high-definition steel sheet, a roll obtained by machining the filtered center line waviness Wca to 1.1 μm or less and Ra to 1.0 μm or more by electric discharge machining is used. A method is disclosed. However, in principle, since random irregularities are formed in electrical discharge machining, when Ra defined by the average height of short-period components exceeds 2.0 μm, Wca defined by the average height of long-period components is also The technology of Patent Document 1 cannot achieve both excellent press formability and good post-painting sharpness, such as inevitably increasing and it is not easy to control Wca to 1.1 μm or less.

Japanese Patent Publication No. 6-23409

T.G.NILAN, B.M.PERFETTI and B.J. SCIALABBA: SAE Tech. Paper Ser. , No. 800208 (1980) Kouyama Kouzo and 4 others, “Effect of surface roughness on the sharpness after painting”, Iron and Steel, Japan Iron and Steel Institute, 1989, vol. 75, no. 11, P2090-2097

  Here, according to the laser dull processing described in Non-Patent Document 2, short-period unevenness and long-period unevenness can be individually controlled to some extent, but there is a problem that long-period unevenness cannot be reduced due to the heat effect of processing heat generation. is there.

  The present invention has been made in view of the above-mentioned problems, and is a surface-treated steel sheet that has been subjected to temper rolling of a surface-treated steel sheet and has both excellent press formability and good post-painting sharpness at the same time. The present invention provides a roll for temper rolling and / or a roll for rolling that can be used as a roll for cold rolling, a method for producing the roll, and a method for producing a surface-treated steel sheet and a cold-rolled steel sheet. It is an object to provide a surface-treated steel sheet (surface-treated steel sheet as a press original sheet) and a cold-rolled steel sheet that have both press formability and good post-paint clarity.

The present invention has been made to achieve the above object, and the gist thereof is as follows.
[1] A roll for rolling, the arithmetic average roughness Ra, the arithmetic average waviness Wa, and the number of peaks PPI per inch are Ra: 1 to 10 μm and Wa: 0.01 to 0, respectively. Roll for rolling characterized by being 10 μm and PPI: 300-2000.
[2] The rolling roll according to [1], wherein the roll has a plurality of hemispherical protrusions having a diameter of 10 to 40 μm arranged at intervals of 5 to 20 μm on the surface of the roll.
[3] The roll comprises a roll substrate and a coating layer covering the roll substrate, and the coating layer has a surface having a hardness higher than that of the roll substrate [1] or The rolling roll according to [2].
[4] The roll for rolling according to [3], wherein the coating layer is made of diamond-like carbon.
[5] The roll for rolling according to any one of [1] to [4], wherein the roll is a roll for cold rolling.
[6] The roll for rolling according to any one of [1] to [4], wherein the roll is a roll for temper rolling.
[7] A method for producing the rolling roll according to any one of [1] to [6], wherein a pulse width of more than 100 femtoseconds to 10 picoseconds is formed on a surface of a cylindrical roll material. The manufacturing method of the roll for rolling characterized by having the process of irradiating a short pulse laser.
[8] Using the rolling roll according to any one of [1] to [6], temper rolling with an elongation of 0.1 to 2.0% is performed on the surface-treated steel sheet. A method for producing a surface-treated steel sheet.
[9] A surface-treated steel sheet that has been subjected to temper rolling, wherein the arithmetic average roughness Ra, arithmetic average waviness Wa, and the number of peaks PPI per inch are Ra: 0.5 to 10 μm, respectively. Wa: 0.01 to 0.6 μm, PPI: 300 to 2000, a surface-treated steel sheet.
[10] The surface-treated steel sheet according to [9], wherein the steel sheet has a plurality of hemispherical depressions having a diameter of 10 to 40 μm arranged at an interval of 5 to 20 μm on the surface of the steel sheet.
[11] A cold-rolled steel sheet, wherein the rolling roll according to any one of [1] to [6] is used and cold rolling is performed at a rolling reduction of 5 to 30% on the steel sheet. Production method.
[12] Surface arithmetic average roughness Ra, arithmetic average waviness Wa, peak number PPI per inch are Ra: 0.5-5 μm, Wa: 0.01-1 μm, PPI: 300-2000, respectively. Cold-rolled steel sheet characterized by
[13] The cold-rolled steel sheet according to [12], having a plurality of hemispherical depressions having a diameter of 10 to 40 μm arranged on the surface of the steel sheet at an interval of 5 to 20 μm.

  According to the present invention, it is possible to provide a rolling roll suitable for the production of a surface-treated steel sheet or a cold-rolled steel sheet having both excellent press formability and good post-paint clarity. And when temper-rolling the unheated rolled material of the surface-treated steel sheet using the roll for rolling of the present invention as a roll for temper rolling, it had both excellent press formability and good post-paint clarity. A surface-treated steel sheet can be obtained, and when the roll for cold rolling of the present invention is used as a roll for cold rolling, temper rolling is performed on a non-tempered rolled material of a cold-rolled steel sheet. A cold-rolled steel sheet having excellent post-painting sharpness can be obtained.

It is a schematic diagram which shows an example of the roll for rolling which concerns on this invention. It is the (a) enlarged plan view and (b) enlarged sectional view which show the example of the surface shape of the roll for rolling of FIG. It is a schematic diagram which shows an example of a temper rolling mill. It is a schematic diagram of the sliding test for press moldability evaluation. In Example 1, it is a figure which shows the example which evaluated press moldability. In Example 1, it is a figure which shows the example which evaluated the sharpness after coating. In Example 2, it is a figure which shows the example which evaluated press moldability. In Example 2, it is a figure which shows the example which evaluated the post-painting sharpness.

  The roll for rolling of the present invention is used for cold rolling and / or temper rolling, and the roll surface has an arithmetic average roughness Ra (hereinafter also simply referred to as “Ra”): 1 to 10 μm, an arithmetic average waviness Wa. (Hereinafter also simply referred to as “Wa”): 0.01 to 0.1 μm, number of peaks per inch PPI (hereinafter also simply referred to as “PPI”): irregularities satisfying 300 to 2000 (these Ra, Wa and PPI) The unevenness satisfying the above range is hereinafter also referred to as “predetermined unevenness”). Since the roll for rolling of the present invention has unevenness on the surface (outer peripheral surface) in which each value of Ra, Wa, and PPI is limited as described above, for example, the surface-treated steel sheet before temper rolling is temper-rolled. By using for the surface-treated steel sheet after temper rolling, it gives very excellent press formability and good post-paint clarity, that is, very excellent press formability by temper rolling. A surface-treated steel sheet having good post-painting sharpness can be produced. Here, the surface-treated steel sheet is a steel sheet whose surface has been subjected to a plating treatment or the like in order to enhance corrosion resistance. Specific examples include a galvanized steel sheet, a tin-plated steel sheet, an aluminum-plated steel sheet, and an alloy-plated steel sheet made of a plurality of metals. Etc.

  Ra is preferably 1.0 to 3.0 [mu] m among the limited range of 1 to 10 [mu] m. Further, Wa is preferably 0.04 to 0.07 μm among the limited range of 0.01 to 0.10 μm. The PPI is preferably 350 to 1300 among the limited range 300 to 2000 of the value.

  The rolling roll of the present invention is preferably a dull roll having irregularities on the surface by ultrashort pulse laser processing, rather than a dull roll having irregularities on the surface by conventional shot blasting or electric discharge machining.

  Ultrashort pulse laser processing (also referred to as optical ablation) is laser processing using a pulse laser having a pulse width of several picoseconds (ps) to several femtoseconds (fs) or less. Ultra-short pulse laser processing directly breaks the molecular or atomic bonds that make up the material, making it simple thermal processing (laser light is absorbed by the surface of the solid material and converted to heat, and the thermal energy It is a process performed while melting the material.) Furthermore, when an ultrashort pulse is used, the portion irradiated by the laser is removed in a very short time, so that the thermal energy does not have time to spread around the material, and most of it is used for removing the material. As a result, they work together and the heat-affected layer is remarkably reduced, so ultrashort pulse laser processing is a very clean process and does not alter the material, so there is no need for troublesome post-processing. . Therefore, in the ultrashort pulse laser processing, fine predetermined unevenness (hereinafter, “unevenness” is also referred to as “unevenness pattern”) can be formed. That is, an uneven pattern satisfying Ra of 1 to 10 μm, Wa of 0.01 to 0.10 μm and PPI of 300 to 2000 can be formed on the roll surface. Furthermore, in the ultrashort pulse laser processing, the uneven distribution can be made regular and uniform.

  On the other hand, the Ra range of the dull roll having irregularities on the surface by shot blasting is about 0.5 to 3.6 μm, and the PPI range is about 150 to 500. It should be noted that the uneven distribution of the dull roll whose surface is uneven by shot blasting is random and irregular uneven distribution. And the range of Ra of the dull roll with which the unevenness | corrugation was provided to the surface by electric discharge machining is about 0.5-7.2 micrometers, and the range of PPI is about 100-600. Moreover, although the surface can be provided with unevenness by electric discharge machining, the unevenness distribution of the applied dull roll is random and irregular unevenness distribution.

  As described above, in the ultrashort pulse laser processing, it is possible to increase the Ra value and the PPI value indicating the short-period unevenness, and to improve the press formability, as compared with shot blasting and electric discharge processing. At the same time, the Wa value indicating the long-period irregularities can be lowered to improve the post-painting sharpness. The reason for this is that in shot blasting and electrical discharge machining, if the Ra value is increased, the values of Wa and PPI also increase, whereas in ultrashort pulse laser machining, the texture pattern pattern is on the order of microns. This is because the values of Ra, Wa and PPI can be controlled independently of each other.

Furthermore, laser processing applied to conventional dull rolls includes a YAG laser and a CO ₂ laser. However, these conventional laser processings have a thermal effect on the processed part, so that debris generated during processing on the roll surface In this conventional laser processing, the surface shape is Ra: 1 to 10 [mu] m, Wa: 0.01 to 0.10 [mu] m, and PPI: 300, because an altered portion that is melted by heat and re-solidified is generated. It is difficult to produce a roll for rolling that satisfies all the conditions of ˜2000. Furthermore, in shot blasting, electrical discharge machining, and laser machining applied to conventional dull rolls, Ra: 1 to 10 μm, Wa: 0.01 to 0.10 μm, and PPI: 300 to 2000 are all satisfied, and It was not possible to produce a rolling roll with regular and uniform roll surface irregularities.

Here, Ra is an arithmetic average roughness specified in JIS B 0601-1994.
The PPI is defined by the SAE 911 standard, is the number of uneven peaks per unit length (1 inch (2.54 cm)), and is a value at a count level of ± 0.63 μm.
Wa is an arithmetic mean swell defined in JIS B 0601-1994, and a long period component (λc = 0.8 mm, λf = 8 mm) having a wavelength of 0.8 mm to 8 mm is extracted from the irregularities on the surface of the steel plate Find the undulation curve.
Ra, PPI, and Wa can be measured using, for example, Surfcom 1500SD3 (manufactured by Tokyo Seimitsu).

  In addition, the rolling roll of the present invention has a roll surface that satisfies Ra: 1 to 10 μm, Wa: 0.01 to 0.10 μm, and PPI: 300 to 2000 as described above. Are regularly and uniformly, that is, grooves, depressions or protrusions having the same shape are arranged in a predetermined direction, for example, in the roll axis direction and / or the roll circumferential direction, without being spaced apart, continuously or at the same interval It is preferable. Note that the same shape and the same interval here do not necessarily need to be exactly the same shape and interval. For example, the groove width, depth, recess diameter and depth, and protrusion diameter and height are within ± 10% of the target value, and the grooves, recesses, and protrusions have the same shape. May be considered. Thus, by making the predetermined irregularities on the roll surface of the rolling roll of the present invention regular and uniform, regular and uniform irregularities on the surface of the steel sheet by cold rolling using the rolling roll. It is possible to impart a very excellent press formability and a good post-paint clarity to the entire steel sheet. In particular, when the surface-treated steel sheet before temper rolling is temper-rolled using the roll for rolling of the present invention, very excellent press formability and good over the entire surface-treated steel sheet after temper rolling. It is possible to uniformly impart the sharpness after painting. The rolling roll of the present invention for cold rolling may be hereinafter referred to as “the cold rolling roll of the present invention”, and the rolling roll of the present invention for temper rolling is hereinafter referred to as “ It may be referred to as “temper rolling roll of the present invention”.

  In the present invention, by providing irregularities on the surface by ultrashort pulse laser processing, it is possible to substantially prevent debris generated during processing and altered portions melted by heat and re-solidified on the roll surface. , Ra: 1 to 10 μm, Wa: 0.01 to 0.10 μm, and PPI: 300 to 2000, it is possible to form a regular and uniform uneven pattern.

The specific example of the uneven | corrugated pattern on the surface of the roll for rolling of this invention is demonstrated below.
The rolling roll of the present invention according to the above specific example has a plurality of protrusions provided at predetermined intervals on the roll surface (outer peripheral surface).

  Specifically, for example, a plurality of hemispherical protrusions that form fine predetermined irregularities may be provided on the roll surface of the rolling roll according to the above specific example. A rolling roll in which a plurality of hemispherical protrusions are provided on the roll surface will be described with reference to FIG. 2 is an enlarged plan view and an enlarged cross-sectional view showing examples of the surface shape of the rolling roll, FIG. 2 (a) is an enlarged plan view of the outer peripheral surface of the rolling roll of FIG. 1, and FIG. ) Is a cross-sectional view taken along the line CC in FIG.

  As shown in FIG. 2, a plurality of protrusions 12 are provided on the entire roll surface on the roll surface (outer peripheral surface 11) of the cylindrical rolling roll 10. The plurality of projections 12 are hemispherical, have a diameter y of y = 10 to 40 μm, preferably y = 10 to 20 μm, and are provided so that the interval z of the projections 12 is z = 5 to 20 μm. . The interval z between the protrusions 12 is the shortest distance between adjacent protrusions.

  In this way, by forming a rolling roll in which a plurality of hemispherical protrusions having a diameter y = 10 to 40 μm, preferably y = 10 to 20 μm, are provided on the surface (outer peripheral surface) at intervals of 5 to 20 μm. It is possible to improve the oil retaining property of the lubricating oil and the resistance to wear powder accumulation during press molding, and to increase the isotropic property. Further, since the hemispherical projections having a predetermined diameter y = 10 to 40 μm, preferably y = 10 to 20 μm are arranged at a predetermined interval z = 5 to 20 μm, regular and uniform unevenness is obtained. The surface of the steel sheet (including the surface-treated steel sheet) is regular and uniform by cold rolling using the rolling roll or by temper rolling using the rolling roll. Unevenness can be imparted. Here, on the roll surface as shown in FIG. 2, the region of the protrusion 12 becomes the convex portion of the concave / convex pattern, and the region other than the projection 12 becomes the concave portion of the concave / convex pattern. The processing conditions by short pulse laser processing (irradiation conditions of ultra-short pulse laser that changes for each part in the processing surface) are removed from the material surface layer of the cylindrical roll material that is the processing material. It can be realized by adjusting so as to be within a condition range in which only a portion to be a convex portion remains.

  The hemispherical protrusion includes a sphere-shaped protrusion whose height is less than the radius of the sphere. In the above specific example, the case where the protrusion is a hemispherical protrusion has been described, but the shape of the protrusion is not limited to a hemispherical shape, and may be, for example, a conical protrusion.

  The rolling roll according to the present invention includes a roll base and a coating layer covering the roll base, including a cold rolling roll and a temper rolling roll. It is good also as a roll for rolling characterized by being a hard coat layer which has a surface whose hardness is higher than that. During the temper rolling of the surface-treated steel sheet using the rolling roll of the present invention in the absence of the hard coating layer, the roll surface wears as the rolling distance increases and the predetermined unevenness range can be maintained. As a result, a desired uneven pattern may not be imparted to the surface-treated steel sheet. However, by using a rolling roll having a hard coating layer on the surface of the roll base, it is possible to suppress the wear of the roll. The hardness of the hard coating layer is, for example, 1000 HV or more and 7000 HV or less in terms of Vickers hardness. Specific examples of the material for forming the hard coating layer include, for example, diamond-like carbon (hereinafter also referred to as DLC). The thickness of the hard coating layer is, for example, 1 to 3 μm. When the thickness of the hard coating layer is 1 to 3 μm, the thickness is sufficiently thin with respect to the predetermined unevenness provided on the roll base of the rolling roll. This predetermined unevenness can be maintained on the roll surface of the cold rolling roll without being crushed. Specifically, for example, the hardness of the surface of the roll base material is generally about 90Hs (cold hardness 820 HV) of cold tool steel, but DLC having a film thickness of about 1 to 3 μm on the surface of the roll base material. If the hard coating layer is provided, the textured surface is covered with a hard coating layer having a Vickers hardness of 1000 HV to 7000 HV, so there is no possibility of wear due to an increase in the rolling distance. In addition, Vickers hardness can be measured on the conditions of test force = 0.5-10N using a Vickers hardness meter.

  As described above, the rolling roll of the present invention can be manufactured by imparting predetermined irregularities to the roll surface by ultrashort pulse laser processing. That is, the method for producing a rolling roll according to the present invention includes a step of irradiating the surface of a roll base material forming a cylindrical roll material with an ultrashort pulse laser having a pulse width of 100 femtoseconds to 10 picoseconds. Features. The pulse width range of 100 femtoseconds to 10 picoseconds is a pulse width range suitable for imparting the predetermined unevenness to the surface of the roll base material. Moreover, when manufacturing the roll for rolling which has a hard film layer on the surface of a roll base material, a hard film layer is rolled by a vapor phase growth method etc. after the process of irradiating the surface of a roll base material with an ultrashort pulse laser. What is necessary is just to form on the surface of a base material.

  The rolling roll of the present invention can be suitably used for temper rolling of a surface-treated steel sheet as a temper rolling roll. That is, the manufacturing method by temper rolling of the surface-treated steel sheet of the present invention (hereinafter also simply referred to as “tempered rolling method of the present invention”) is performed on the surface-treated steel sheet using the roll for temper rolling of the present invention. Thus, temper rolling with an elongation of 0.1 to 2.0% is performed.

  The temper rolling is cold rolling with a low elongation rate applied to a steel sheet for the purpose of adjusting the hardness. The elongation of temper rolling is, for example, 0.1 to 2.0%.

  And in the temper rolling method of this invention, a surface-treated steel plate is made into the object of temper rolling. As described above, the surface-treated steel sheet is a steel sheet that has been subjected to plating treatment or the like in order to improve corrosion resistance. Specific examples include galvanized steel sheets, tin-plated steel sheets, aluminum-plated steel sheets, and alloy plating with multiple metals. A steel plate etc. can be mentioned.

  The surface-treated steel sheet subjected to such surface treatment as plating is temper-rolled using the roll for temper rolling of the present invention. Specifically, for example, as shown in FIG. 3, which is a schematic diagram showing an example of a temper rolling mill, the surface-treated steel sheet 101 is applied with lubricating oil from the spray nozzles 102 a and 102 b to be in a wet state, or Then, in a dry state without applying lubricating oil, it is supplied to a temper rolling mill and sandwiched between a pair of upper and lower work rolls 103a and 103b, thereby performing temper rolling with an elongation of 0.1 to 2.0%. . Note that the straight left-pointing arrow in FIG. 3 is the sheet passing direction of the surface-treated steel plate 101. In the temper rolling method of the present invention, the temper rolling roll of the present invention (for example, comprising the rolling roll 10 of FIG. 1) is used as the work rolls 103a and 103b. Since the roll for temper rolling of the present invention has the predetermined irregularities according to the present invention on the surface (outer peripheral surface 11) of the roll, the irregularities corresponding to the predetermined irregularities of the roll for temper rolling are surfaced during temper rolling. It can be imparted (transferred) to the treated steel sheet, and the surface-treated steel sheet after temper rolling can have both excellent press formability and good post-paint clarity.

  Here, as described in [9] above, the surface-treated steel sheet after temper rolling has Ra: Wa, PPI on the surface of the steel sheet, Ra: 0.5 to 10 μm, Wa: 0.01-0. It is characterized by being 6 μm and PPI: 300-2000. In addition, the surface-treated steel sheet having this feature is preferably a plurality of hemispherical depressions having a diameter of 10 to 40 μm and arranged at intervals of 5 to 20 μm on the surface of the steel sheet as described in [10] (see [[ 2), and a depression corresponding to the “projection” described in 2). The hemispherical depression includes a sphere-shaped depression whose depth is less than the radius of the sphere. The surface-treated steel sheet after temper rolling is subjected to press molding, painting, etc., and used as an outer panel for automobiles, electrical appliances, and the like.

  In the above, the example of using the rolling roll of the present invention as the temper rolling roll of the present invention for the temper rolling of the surface-treated steel sheet has been described, but the temper rolling roll of the present invention will be described later. You may use for other temper rolling. Here, as other temper rolling, temper rolling of the steel plate which is not surface-treated is mentioned, for example.

Moreover, the roll for rolling of this invention can also be used suitably for the cold rolling of a cold-rolled steel plate as a roll for cold rolling.
That is, the manufacturing method by cold rolling of the cold rolled steel sheet of the present invention (hereinafter also simply referred to as “the cold rolling method of the present invention”) is the cold rolling roll of the present invention as described in [11] above. Is used to cold-roll the steel sheet at a reduction rate of 5 to 30%.

  The cold rolling method of the present invention is a tandem cold rolling mill having a plurality of rolling stands. The predetermined unevenness according to the present invention is formed on the surface (outer peripheral surface 11) of the cold rolling roll of the cold rolling mill of the final stand. Therefore, at the time of cold rolling, irregularities corresponding to the predetermined irregularities of the roll for cold rolling can be imparted (transferred) to the cold rolled steel sheet, and the cold rolled steel sheet after cold rolling is very excellent It is possible to have both press formability and good post-paint clarity.

  Here, the cold-rolled steel sheet after cold rolling has a plurality of hemispherical depressions with a diameter of 10 to 40 μm arranged at intervals of 5 to 20 μm on the surface, as described in [13] above, and [12] As described in [12], the arithmetic average roughness Ra, the arithmetic average waviness Wa, and the peak number PPI per inch are Ra: 0.5 to 5 μm, Wa: 0.01 to 1 μm, and PPI: It is preferable that it is 300-2000. The cold-rolled steel sheet after cold rolling is subjected to press molding, painting, or the like, and is used as a member for automobiles, an electrical appliance or the like.

Hereinafter, the present invention will be described by way of examples for further understanding of the present invention. However, the examples do not limit the present invention.
[Example 1]
In Example 1, temper rolling was performed with an experimental rolling mill as shown in FIG. As the material to be rolled, a surface-treated steel sheet that was in the state after hot-dip galvanizing treatment of a cold-rolled steel sheet and was not subjected to temper rolling was used. Further, the work rolls 103a and 103b as temper rolling rolls have irregularities with different texture forms on the cylindrical roll outer peripheral surface of a cold tool steel SUJ2 (JIS G4805) having a diameter of 500 mm. What performed the process to provide was used. Specifically, in Comparative Example 1, a roll having irregularities on the entire outer peripheral surface of the roll by shot blasting, and in Comparative Example 2, a roll having irregularities on the entire outer peripheral surface of the roll by electric discharge machining were used as rolls for temper rolling. . In Invention Example 1, which is an embodiment of the present invention, hemispherical protrusions having a diameter y = 40 μm are formed on the outer peripheral surface of the roll at an interval z = 20 μm by ultrashort pulse laser processing with a pulse width of 180 to 190 fs. A roll for rolling provided over the entire surface was used as a roll for temper rolling. About each roll for temper rolling, Ra, PPI, and Wa were each measured with the above-mentioned measuring method. In Example 1 of the present invention in which hemispherical protrusions were provided, the PPI was measured in the direction passing through the protrusions (extending direction of the CC line in FIG. 2). The results are shown in Table 1. Immediately before the temper rolling mill, lubricating water was sprayed on the front and back surfaces of the steel sheet, and temper rolling was performed at an elongation rate of 1% with the temper rolling mill.

  Moreover, Ra, PPI, and Wa of the surface-treated steel sheet after temper rolling were measured by the above-described measuring methods. The results are shown in Table 1.

  As shown in Table 1, the roll for rolling of Invention Example 1 had Ra of 1 to 10 μm, Wa of 0.01 to 0.10 μm and PPI of 300 to 2000. Specifically, in Inventive Example 1, Ra was 3.68 μm, Wa was 0.06 μm, and PPI was 610. In addition, the uneven distribution of Invention Example 1 was regular and uniform.

  On the other hand, as shown in Table 1, in shot blast comparative example 1, Ra is 1.76 μm, Wa is 0.98 μm, and PPI is 229. In electric discharge machining comparative example 2, Ra is 1.79 μm and Wa is 1 0.06 μm and PPI of 203. Further, the uneven distribution of Comparative Example 1 and Comparative Example 2 was random and irregular.

  The surface-treated steel sheet after temper rolling had Ra of 2.67 μm, Wa of 0.56 μm, and PPI of 610 in Invention Example 1. Further, the uneven distribution of the surface-treated steel sheet of Invention Example 1 was regular and uniform.

  Furthermore, as an evaluation of press formability of the surface-treated steel sheet after temper rolling, a sliding test was performed with a testing machine as shown in FIG. In the sliding test, a pressing force P is applied to the upper and lower pressing pieces 40a and 40b having a curvature radius R of R = 20 mm, a test piece 41 having a width of 20 mm and a length of 300 mm is pulled out in the direction of the arrow, and the pulling force D at that time is measured. To do. The drawing speed of the test piece is 100 mm / sec, the moving distance is 80 mm, and the surface pressure is 300 MPa. A press oil having a viscosity of 16.3 cSt at 40 ° C. was applied to the test piece and drawn. The friction coefficient μ was determined by μ = pulling force D / (2 × pressing force P). The results are shown in FIG. As shown in FIG. 5, the coefficient of friction was 0.16 in Comparative Example 1, the coefficient of friction was 0.15 in Comparative Example 2, and the coefficient of friction was 0.11 in Example 1 of the present invention.

  In the post-paint clarity test, the surface-treated steel sheet after temper rolling is subjected to phosphate treatment, electrodeposition coating (20 μm), intermediate coating (35 μm), top coating (35 μm), and clear coating (25 μm) in this order. The coated plate produced by the application was evaluated with an NSIC value measured using a “map sharpness measuring device NSIC type” manufactured by Suga Test Instruments Co., Ltd. The result is shown in FIG. The NSIC value is 100 for blackboard polished glass, and the closer the value is to 100, the better the sharpness is. As shown in FIG. 6, the NSIC value was 28 in Comparative Example 1, the NSIC value was 45 in Comparative Example 2, and the NSIC value was 75 in Invention Example 1.

  Thus, it can be seen that Example 1 of the present invention is very excellent in press formability since PPI is remarkably large compared to Comparative Examples 1 and 2. In addition, since Example 1 of the present invention has a remarkably small Wa, it can be seen that the sharpness after painting is very excellent. Therefore, it can be said that Example 1 of the present invention made it possible to achieve both excellent press formability and improved post-paint clarity.

  Moreover, it obtained by making the hard film layer (henceforth "DLC hard film layer") which consists of DLC on the roll base-material surface of each roll for temper rolling produced like the example 1 of this invention. When the roll was used as a roll for temper rolling and an actual operation test was conducted at a rolling distance of 3 km, the DLC hard coating layer maintained the irregularities before the temper rolling without wearing the irregularities on the roll surface. It was confirmed. On the other hand, when an actual operation test with a rolling distance of 1 km was carried out using the roll for temper rolling without the DLC hard coating layer of Example 1 of the present invention, the rolling distance was not problematic to the temper rolling. Initial wear of irregularities occurred around 1 km.

[Example 2]
In Example 2, cold rolling with a rolling reduction of 20% was performed with an experimental cold rolling mill (not shown). As a material to be rolled, a cold rolled steel sheet having an arithmetic average roughness Ra of 0.1 μm on the surface of the steel sheet was used, and a total of three cases of Invention Example 2, Comparative Example 3, and Comparative Example 4 were rolled. Here, in the present invention example 2, the comparative example 3, and the comparative example 4, the rolling rolls of the inventive example 1, the comparative example 1, and the comparative example 2 are used as the cold rolling rolls for the above-described cold rolling for experiments. It was used for the work roll of the machine (not shown).

  Ra, PPI, and Wa of the cold-rolled steel sheets after each cold rolling of Invention Example 2, Comparative Example 3, and Comparative Example 4 were measured in the same manner as in Example 1. The results are shown in Table 2.

  As shown in Table 2, it can be seen that the cold-rolled steel sheet of Example 2 of the present invention has significantly higher PPI and significantly lower Wa than the cold-rolled steel sheets of Comparative Examples 3 and 4. Therefore, since PPI is remarkably large, it is very excellent in press moldability like Example 1 of the present invention, and because Wa is remarkably small, it is very excellent in post-painting sharpness as in Example 1 of the present invention.

  The friction coefficient μ was determined by the same sliding test as in Example 1. As a result, as shown in FIG. 7, it was 0.21 and 0.20 in Comparative Example 3 and Comparative Example 4, respectively, whereas in Example 2 of the present invention, it was 0.13, which is lower, and press formability is improved. It was found to be an excellent cold-rolled steel sheet.

  Further, the NSIC value was measured by the same post-paint clarity test as in Example 1. As a result, as shown in FIG. 8, it was 22 and 34 in Comparative Example 3 and Comparative Example 4, respectively, whereas in Example 2 of the present invention, it was 67 that was much higher and cold rolling excellent in sharpness after coating. It turned out to be a steel plate.

DESCRIPTION OF SYMBOLS 10 Roll 11 Outer peripheral surface 12 Protrusion 40a, 40b Pressing piece (a is up, b is down)
41 Specimen 101 Surface-treated steel plate 102a, 102b Spray nozzle (a is up, b is down)
103a, 103b Work roll (a is up, b is down)

Claims (10)

  A roll for rolling, which has a plurality of hemispherical protrusions having a diameter of 10 to 40 μm arranged at intervals of 5 to 20 μm on the surface of the roll, and the arithmetic average roughness Ra and arithmetic average undulation Wa of the surface of the roll , And the number of peaks per inch PPI is Ra: 1 to 10 μm, Wa: 0.01 to 0.10 μm, and PPI: 300 to 2000, respectively.   The rolling according to claim 1, wherein the roll includes a roll base material and a coating layer that covers the roll base material, and the coating layer has a surface having a hardness higher than that of the roll base material. Rolls.   The roll for rolling according to claim 2, wherein the coating layer is made of diamond-like carbon.   The said roll is a roll for cold rolling, The roll for rolling as described in any one of Claims 1-3 characterized by the above-mentioned.   The said roll is a roll for temper rolling, The roll for rolling as described in any one of Claims 1-3 characterized by the above-mentioned.   It is a method of manufacturing the roll for rolling as described in any one of Claims 1-5, Comprising: The ultrashort pulse laser whose pulse width is 100 femtoseconds-10 picoseconds is irradiated to the surface of a cylindrical roll raw material. The manufacturing method of the roll for rolling characterized by having the process to do.   A surface-treated steel sheet, which is subjected to temper rolling with an elongation of 0.1 to 2.0% for the surface-treated steel sheet, using the rolling roll according to any one of claims 1 to 5. Manufacturing method.   A surface-treated steel sheet subjected to temper rolling, the surface of the steel sheet having a plurality of hemispherical depressions having a diameter of 10 to 40 μm arranged at intervals of 5 to 20 μm, and an arithmetic average roughness of the surface of the steel sheet Surface treatment, characterized in that Ra, arithmetic mean waviness Wa, number of peaks PPI per inch are Ra: 0.5 to 10 μm, Wa: 0.01 to 0.6 μm, PPI: 300 to 2000, respectively. steel sheet.   A method for producing a cold-rolled steel sheet, comprising performing cold rolling at a rolling reduction of 5 to 30% on a steel sheet using the rolling roll according to any one of claims 1 to 5.   The surface has a plurality of hemispherical depressions having a diameter of 10 to 40 μm arranged at intervals of 5 to 20 μm, and the arithmetic average roughness Ra, arithmetic average waviness Wa, and the number of peaks PPI per inch are Ra. : Cold rolled steel sheet characterized by being 0.5-5 μm, Wa: 0.01-1 μm, PPI: 300-2000.

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