JP2018164942A - Cold rolling roller, manufacturing method for cold rolling roller, conditioning rolling method for surface treatment steel plate, and surface treatment steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cold rolling roller which can be used as a conditioning rolling roller capable of manufacturing the surface treatment steel plate having both of extremely superior press forming properties and satisfactory image clarity after coating at the same time by performing conditioning rolling of a steel plate subjected to surface treatment, and a manufacturing method for the cold rolling roller and a conditioning rolling method for the surface treatment steel plate, and to provide the surface treatment steel plate having both of the extremely excellent press forming properties and the preferable image clarity after the coating at the same time.SOLUTION: A cold rolling roller of which a surface has an arithmetic average roughness Ra of 1 to 10 μm, an arithmetic average waviness Wa of 0.01 to 0.1 μm and the number of peaks PPI per one inch of 300 to 2000 is provided.SELECTED DRAWING: None

Description

  The present invention is a roll for cold rolling that can be suitably used for temper rolling of a surface-treated steel sheet and a method for producing the roll, a temper rolling method for a surface-treated steel sheet, and a surface treatment that is excellent in press formability and post-paint clarity. It relates to steel sheets.

  There are two general characteristics required of a steel sheet: excellent appearance and excellent formability.

  As an index that has a significant effect on the appearance of a steel sheet, the post-paint clarity 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 plate after coating the steel plate 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 technology for improving the post-painting sharpness of the surface-treated steel sheet is becoming increasingly important. In particular, a thick-coated steel sheet such as a hot-dip steel sheet is required from a design that emphasizes corrosion resistance, and even when using such a thick-plated surface-treated steel sheet, the sharpness after painting is considered to be more important. It has been.

  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 (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 the painting method and the improvement of 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 increased costs. Therefore, further 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 shown as a document showing the relationship between the surface roughness of the 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 press-formed, a dull weight is provided to provide unevenness on the surface of the steel sheet for the purpose of improving the press formability and handling properties. Since the steel sheet with a dull weight is increased in surface roughness, the sharpness is naturally 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, electric 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, the wavelength of waviness is determined by the size and spacing of microcraters (recesses generated by lasers). It is possible to improve the sharpness while maintaining the surface roughness. 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 post-painting sharpness, it is necessary to reduce long-period irregularities (swells) that remain on the steel plate surface even after painting and adversely affect the sharpness.

  In other words, in order to achieve both excellent press formability and good post-paint clarity, the size and number of short-period irregularities indicated by indicators such as Ra and PPI are increased, and indicators such as Wa are used. It is required to reduce the size and number of the long-period irregularities shown. 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 temper rolling roll for producing a high-sharp steel sheet, there is a method of using a roll obtained by machining a filtered center line waviness Wca to 1.1 μm or less and Ra to 1.0 μm or more by electric discharge machining. It 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-wavelength 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 in that long-period unevenness cannot be reduced due to the thermal effect of processing. is there.

  The present invention has been made in view of the above-mentioned problems, and temper-rolled a steel sheet that has been subjected to surface treatment, and at the same time has both excellent press formability and good post-paint clarity. It is an object of the present invention to provide a cold rolling roll that can be used as a temper rolling roll capable of producing a surface-treated steel sheet, a manufacturing method thereof, and a temper rolling method for a surface-treated steel sheet. It is another object of the present invention to provide a surface-treated steel sheet having both excellent press formability and good post-paint clarity.

  In order to achieve the above object, the present invention has the following features.

[1] Cold rolling characterized in that the surface has an arithmetic average roughness Ra of 1 to 10 μm, an arithmetic average waviness Wa of 0.01 to 0.1 μm, and a peak number PPI per inch of 300 to 2000. Rolls.
[2] The cold according to [1], wherein a plurality of grooves having a V-shaped cross section having a depth of 5 to 10 μm and an angle of 60 to 120 ° are provided on the surface substantially in parallel to each other. Roll for rolling.
[3] The roll for cold rolling according to [1], wherein a plurality of hemispherical depressions having a diameter of 10 to 40 μm are provided on the surface at intervals of 5 to 20 μm.
[4] The roll for cold rolling as described in any one of [1] to [3], wherein the surface has a film harder than the base material of the roll for cold rolling.
[5] The roll for cold rolling according to [4], wherein the coating is diamond-like carbon.
[6] The cold rolling roll according to any one of [1] to [5], which is a temper rolling roll.
[7] Any one of [1] to [6], including a step of irradiating the surface of the cylindrical roll with an ultrashort pulse laser having a pulse width of 100 femtoseconds to 10 picoseconds. The manufacturing method of the roll for cold-rolling of description.
[8] Using the roll for cold rolling 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 temper rolling method for a surface-treated steel sheet characterized by
[9] A surface having an arithmetic average roughness Ra of 0.5 to 10 μm, an arithmetic average waviness Wa of 0.01 to 0.6 μm, and a peak number PPI per inch of 300 to 2000. Treated steel sheet.
[10] The surface is provided with a plurality of stripe-shaped protrusions having a triangular cross section having a height of 5 to 10 μm and an apex angle of 60 to 120 °, substantially parallel to each other. [9] The surface-treated steel sheet described in 1.
[11] The surface-treated steel sheet according to [9], wherein a plurality of hemispherical protrusions having a diameter of 10 to 40 μm are provided on the surface at intervals of 5 to 20 μm.

  According to the present invention, it is possible to provide a cold rolling roll that can be used as a temper rolling roll suitable for the production of a surface-treated steel sheet that has both excellent press formability and good post-paint clarity. . Then, when the temper rolling is performed using the roll for cold rolling according to the present invention, a surface-treated steel sheet having both excellent press formability and good post-paint clarity can be obtained.

It is a schematic diagram which shows an example of the roll for cold rolling. It is an enlarged plan view and an enlarged sectional view for explaining a surface example of a roll for cold rolling. It is an enlarged plan view and an enlarged sectional view for explaining a surface example of a roll for cold rolling. It is an expanded sectional view explaining the example of the surface of the roll for cold rolling. It is an enlarged plan view and an enlarged sectional view for explaining a surface example of a roll for cold rolling. 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-formability evaluation of a surface treatment steel plate. It is a graph which shows the example which evaluated the press formability of the surface treatment steel plate. It is a graph which shows the example which evaluated the post-painting sharpness of the surface treatment steel plate.

  The surface of the roll for cold rolling of the present invention has an arithmetic average roughness Ra (hereinafter also simply referred to as “Ra”) of 1 to 10 μm and an arithmetic average waviness Wa (hereinafter also simply referred to as “Wa”) of 0. The number of peaks PPI of 01 to 0.1 μm per inch (hereinafter also simply referred to as “PPI”) is 300 to 2000. Since the roll for cold rolling according to the present invention has predetermined irregularities on the surface (outer peripheral surface) in this way, for example, by using it for temper rolling of a surface-treated steel sheet, very excellent press formability and good coating It is possible to produce a surface-treated steel sheet that has both post-clarity. The Ra is preferably 1.0 to 3.0 μm. Wa is preferably 0.04 to 0.07 μm. Moreover, PPI is 350-1300.

  The roll for cold rolling according to the present invention is formed on the surface by laser processing with an ultrashort pulse, rather than a dull roll having irregularities on the surface by conventional shot blasting or a dull roll having irregularities on the surface by electric discharge machining. It is preferably a dull roll provided with irregularities.

  Ultra-short pulse laser processing (photoablation) in picoseconds (ps) or femtoseconds (fs) is not a simple thermal processing because it directly breaks the molecular or atomic bonds that constitute 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, these work together and the heat-affected layer significantly decreases, so laser processing using picosecond or femtosecond ultrashort pulses is extremely clean and does not alter the material. There is no need for troublesome post-processing. Therefore, in laser processing using an ultrashort pulse with a pulse width of picoseconds or femtoseconds, it is possible to form predetermined fine irregularities, that is, Ra on the roll surface is 1 to 10 μm and Wa is 0.01 to It is possible to make 0.1 μm and PPI satisfy 300 to 2000. In addition, 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. 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. Further, the uneven distribution of the dull roll whose surface is uneven by shot blasting is random and irregular.

  In this way, in laser processing using picosecond or femtosecond ultrashort pulses, Ra and PPI values indicating short-period irregularities can be increased and press formability can be improved compared to shot blasting and electric discharge machining. At the same time, it is possible to improve the sharpness after painting by lowering the Wa value indicating long-period unevenness. This is because, in shot blasting and electrical discharge machining, if the Ra value is increased, both the Wa value and the PPI value are increased. However, in ultrashort pulse laser processing, the texture pattern can be freely designed on the micron order. , Ra value, Wa value and PPI can be controlled independently.

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 0.1 [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 cold rolling roll that satisfies all of ~ 2000. Furthermore, in shot blasting, electric discharge machining, and laser machining applied to conventional dull rolls, Ra: 1 to 10 μm, Wa: 0.01 to 0.1 μm, and PPI: 300 to 2000 are all satisfied, and A regular and uniform roll could not be produced.

  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 having a wavelength of 0.8 mm to 8 mm (λc = 0.8 mm, λf = 8 mm) among the irregularities on the surface of the roll or steel plate. Is obtained for the undulation curve extracted.

  Ra, PPI, and Wa can be measured using Surfcom 1500SD3 (manufactured by Tokyo Seimitsu).

  Further, the roll for cold rolling of the present invention has surface irregularities in addition to satisfying Ra: 1 to 10 μm, Wa: 0.01 to 0.1 μm and PPI: 300 to 2000 as described above. It is preferable that the grooves and the recesses having the same shape are arranged in a predetermined direction continuously or at the same interval without being spaced apart. In addition, the same shape and the same space | interval may not be completely the same. By making the irregularities on the surface regular and uniform in this way, it is possible to impart regular and uniform irregularities to the surface of the steel sheet by cold rolling, and very excellent press formability and good The sharpness after coating can be imparted uniformly over the entire steel sheet. In the present invention, by providing irregularities on the surface by laser processing with an ultra-short pulse, substantially no debris generated during processing and denatured portions melted by heat and re-solidified on the roll surface. Therefore, even a fine unevenness of Ra: 1 to 10 μm, Wa: 0.01 to 0.1 μm and PPI: 300 to 2000 can be formed into a regular and uniform uneven pattern.

  The specific example of the unevenness | corrugation of the surface of the roll for cold rolling of this invention is demonstrated below.

  In the roll for cold rolling of the present invention, a plurality of grooves extending in any direction may be provided substantially parallel to each other on the surface (outer peripheral surface), and a plurality of depressions are provided at predetermined intervals. It may be.

  Specifically, for example, in the roll for cold rolling of the present invention, a plurality of grooves having a V-shaped cross section may be provided substantially parallel to each other on the surface (outer peripheral surface). A roll for cold rolling in which a plurality of grooves having a V-shaped cross section are provided on the surface in substantially parallel to each other will be described with reference to FIGS. FIG. 1 is a schematic view showing an example of a cold rolling roll. 2 is an enlarged plan view and an enlarged cross-sectional view illustrating an example of the surface of the cold rolling roll, and FIG. 2A is an enlarged plan view of the outer peripheral surface of the cold rolling roll of FIG. FIG. 2B is a cross-sectional view taken along line AA of FIG.

  As shown in FIG. 1, the cold rolling roll 10 has a cylindrical shape. The surface (outer peripheral surface 11) of the cold rolling roll 10 is parallel to the axial direction of the cold rolling roll 10 from one end in the axial direction of the cold rolling roll 10 to the other end. A plurality of grooves formed up to the portion are provided. That is, the plurality of grooves formed from one end to the other end of the cold rolling roll 10 are arranged in parallel to each other in the axial direction of the cold rolling roll 10. As shown in FIG. 2, the plurality of grooves 21 have a V-shaped cross section in a direction perpendicular to the axial direction of the cold rolling roll 10, and the grooves 21 have a depth d of 5 to 10 μm and an angle. θ is 60 to 120 °.

  As described above, the surface (outer peripheral surface) is cold in which a plurality of grooves 21 having a V-shaped cross section, a depth d: 5 to 10 μm, and an angle θ: 60 to 120 ° are arranged substantially in parallel with each other. By setting it as the roll for rolling, the oil retention property of the lubricating oil at the time of press molding and the deposition property of an abrasion powder can be improved. Further, as described above, since the groove has a V-shaped cross section having a predetermined depth d and a predetermined angle θ, it becomes a roll for cold rolling having regular and uniform irregularities on the surface. Regular and uniform irregularities can be imparted to the surface of the steel sheet.

  FIG. 2 shows an example in which grooves 21 having a V-shaped cross section are continuous without a gap, but grooves having a V-shaped cross section are provided with a gap x as shown in FIG. It may be done. FIG. 3 is an enlarged plan view and an enlarged sectional view for explaining an example of the surface of the cold rolling roll, and FIG. 3A is an enlarged plan view of the outer peripheral surface of the cold rolling roll, and FIG. ) Is a sectional view taken along line BB in FIG. In FIG. 3, the same components as those in FIG.

  In FIG. 3, as in FIG. 2, the surface of the cylindrical cold rolling roll 10 (outer peripheral surface 11) is parallel to the axial direction of the cold rolling roll 10 and the cold rolling roll 10. A plurality of grooves 21 formed from end to end in the axial direction are provided, and the plurality of grooves 21 have a V-shaped cross section in a direction perpendicular to the axial direction of the roll 10 for cold rolling. The groove 21 has a depth d of 5 to 10 μm and an angle θ of 60 to 120 °. And the groove | channel 21 of FIG. 3 is provided with the space | interval x, and the non-groove part 22 which maintained the outer peripheral surface of a cylindrical roll exists between the adjacent groove | channels 21. FIG. The interval x between the grooves 21 is preferably 20 μm or less. The interval x between the grooves 21 is the shortest distance between adjacent grooves.

  Further, the groove having a V-shaped cross section may not be a V-shaped groove having a complete cross section, as shown in FIG. FIG. 4A and FIG. 4B are enlarged cross-sectional views illustrating examples of the surface of the cold rolling roll, and are enlarged cross-sectional views in a direction perpendicular to the axial direction of the cold rolling roll 10. is there.

  In the above description, an example in which a plurality of grooves 21 are provided in parallel to the axial direction of the cold rolling roll 10 has been described. However, the direction in which the grooves 21 are provided is not particularly limited, and the grooves 21 are formed around the roll. It may be provided along the direction, and may be provided in other directions. In the above description, the groove having a V-shaped cross section is described. However, the cross-sectional shape of the groove is not limited. For example, the groove may have a semicircular cross section.

  The roll for cold rolling of the present invention may have a plurality of hemispherical depressions on the surface. A cold rolling roll having a plurality of hemispherical depressions on the surface will be described with reference to FIG. FIG. 5 is an enlarged plan view and an enlarged cross-sectional view for explaining an example of the surface of the cold rolling roll, and FIG. 5 (a) is an enlarged plan view of the outer peripheral surface of the cold rolling roll of FIG. FIG. 5B is a cross-sectional view taken along the line CC of FIG.

  In FIG. 5, a plurality of depressions 31 are provided on the entire surface of the cold rolling roll 10 on the surface (outer peripheral surface 11) of the cylindrical cold rolling roll 10. The plurality of depressions 31 are hemispherical, have a diameter y of 10 to 40 μm, and are provided so that the interval z is 5 to 20 μm. In addition, the space | interval z of the hollow 31 is the shortest distance between adjacent hollows.

  In this way, by forming a cold rolling roll having a plurality of hemispherical depressions having a diameter of 10 to 40 μm on the surface (outer peripheral surface) at intervals of 5 to 20 μm, the lubricating oil can be maintained during press molding. Oiliness and wear powder accumulation can be improved, and isotropic properties can be increased. Further, as described above, since the hemispherical depressions having a predetermined diameter y are arranged at predetermined intervals, a cold rolling roll having regular and uniform irregularities on the surface is obtained. Regular and uniform irregularities can be imparted to the surface.

  In addition, the said hemispherical hollow contains the spherically-shaped hollow whose depth is less than the radius of a sphere. Moreover, although described about the hemispherical hollow in the above, the shape of a hollow is not limited, For example, a conical hollow may be sufficient.

  Moreover, you may make it the roll for cold rolling of this invention have a hard film which is a film harder than the base material of the roll for cold rolling on the surface. As the rolling distance becomes longer during the temper rolling of the surface-treated steel sheet, the surface of the cold rolling roll as the temper rolling roll is worn and cannot maintain the predetermined range, and as a result, the desired uneven pattern is surface treated. There are cases where it cannot be applied to steel plates. However, wear can be suppressed by using a cold rolling roll having a hard coating on the surface. The hardness of the hard coating is, for example, 7000 Hv or less in terms of Vickers hardness. Specific examples of the hard coating include DLC (diamond-like carbon). The thickness of the hard coating is, for example, 1 to 3 μm. If the thickness of the hard film is 1 to 3 μm, the thickness is sufficiently thin with respect to the predetermined unevenness provided on the base material of the roll for cold rolling. The predetermined unevenness can be maintained on the surface of the roll for cold rolling without doing so. Specifically, for example, the hardness of the roll surface is generally 90Hs (Vickers hardness 820Hv) of cold tool steel, but the surface of the roll is hard of DLC (diamond-like carbon) with a film thickness of about 1 to 3 μm. If a film is provided, the textured surface is covered with a hard film having a Vickers hardness of 1000 Hv to 7000 Hv, so there is no possibility of wear due to the rolling distance. The Vickers hardness can be measured using a Vickers hardness meter.

  As described above, such a roll for cold rolling according to the present invention can be manufactured by providing irregularities on the surface by laser processing with an ultrashort pulse. That is, the manufacturing method of the roll for cold rolling of this invention has the process of irradiating the surface of a cylindrical roll with the ultrashort pulse laser whose pulse width is 100 femtoseconds-10 picoseconds. Moreover, when manufacturing the roll for cold rolling which has a hard film on the surface, what is necessary is just to form a hard film on the surface by a vapor phase growth method etc. after the process of irradiating an ultrashort pulse laser.

  The roll for cold rolling of the present invention can be suitably used for temper rolling of a surface-treated steel sheet. That is, the temper rolling method for the surface-treated steel sheet of the present invention (hereinafter also simply referred to as “the tempered rolling method of the present invention”) uses the roll for cold rolling of the present invention and the elongation rate of the surface-treated steel sheet. It is characterized by performing temper rolling of 0.1 to 2.0%.

  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. A surface-treated steel sheet is a steel sheet that has been subjected to a plating treatment or the like in order to enhance corrosion resistance. Specific examples include galvanized steel sheets, tin-plated steel sheets, aluminum-plated steel sheets, and alloy-plated steel sheets with multiple metals. be able to.

  The surface-treated steel sheet subjected to such surface treatment as plating is temper-rolled using the roll for cold rolling of the present invention. Specifically, for example, as shown in FIG. 6 which is a schematic diagram showing an example of a temper rolling mill, the surface-treated steel sheet 101 is applied with a lubricating oil from the spray nozzles 102a and 102b to be in a wet state, or Suppose that it is in a dry state without applying lubricating oil, is supplied to a temper rolling mill, and is subjected to temper rolling with an elongation of 0.1 to 2.0% by sandwiching with a pair of upper and lower work rolls 103a and 103b. . In addition, the arrow of FIG. 6 is the sheet passing direction of the surface-treated steel plate 101. In the temper rolling method of the present invention, the cold rolling roll 10 of the present invention is used as the work rolls 103a and 103b. Since the roll 10 for cold rolling according to the present invention has predetermined irregularities on the surface, the irregularities corresponding to the predetermined irregularities of the roll for cold rolling are imparted (transferred) to the surface-treated steel sheet during temper rolling. The surface-treated steel sheet after temper rolling can have both excellent press formability and good post-painting sharpness.

  By rolling the surface-treated steel sheet using the roll for cold rolling 10 of the present invention, irregularities corresponding to the predetermined irregularities on the surface of the roll 10 for cold rolling are imparted (transferred) to the surface, and the surface is arithmetic The surface-treated steel sheet of the present invention having an average roughness Ra of 0.5 to 10 μm, an arithmetic average waviness Wa of 0.01 to 0.6 μm, and a peak number PPI per inch of 300 to 2000 is obtained. The surface-treated steel sheet of the present invention has regular and uniform surface irregularities. Thereby, very excellent press formability and good post-painting sharpness can be imparted uniformly over the entire surface-treated steel sheet of the present invention. As for Ra of the surface treatment steel plate surface of this invention, 0.8-5 micrometers is preferable. Wa is preferably 0.1 to 0.6 μm. PPI is preferably 400-1500.

  The specific example of the unevenness | corrugation of the surface of the surface treatment steel plate of this invention is demonstrated below. For example, by rolling the surface-treated steel sheet using the roll for cold rolling according to the present invention shown in FIG. 2, irregularities corresponding to the irregularities on the surface of the cold rolling roll are imparted (transferred) to the surface, and the surface In addition, a surface-treated steel sheet is obtained in which a plurality of streak-like projections having a triangular cross section with a height of 5 to 10 μm and an apex angle of 60 to 120 ° are provided substantially parallel to each other. The plurality of streak-like protrusions are formed in parallel to the width direction of the surface-treated steel sheet and from one end to the other end in the width direction. In addition, when the roll for cold rolling of this invention shown in FIG. 3 is used, according to the unevenness | corrugation of the surface of the said roll for cold rolling, the said several line | wire-like protrusion is formed at intervals x. Further, the cross-sections of the plurality of streaky protrusions do not have to be perfect triangles so as to correspond to the irregularities on the surface of the cold rolling roll of the present invention shown in FIGS. 4 (a) and 4 (b). The direction in which the plurality of streaky protrusions are formed is not particularly limited, and may be formed in parallel to the longitudinal direction of the surface-treated steel sheet or in other directions. The cross-sectional shape of the plurality of streaky protrusions is not particularly limited, and may be, for example, a semicircular shape.

  Further, by rolling the surface-treated steel sheet using the roll for cold rolling of the present invention shown in FIG. 5, irregularities corresponding to the irregularities of the surface of the cold rolling roll are imparted (transferred) to the surface, and the surface In addition, a surface-treated steel sheet in which a plurality of hemispherical protrusions having a diameter of 10 to 40 μm are provided at intervals of 5 to 20 μm is obtained. The hemispherical protrusion includes a sphere-shaped protrusion whose height is less than the radius of the sphere. Further, the shape of the plurality of protrusions is not particularly limited, and may be, for example, a conical shape.

The surface-treated steel sheet of the present invention has regular and uniform irregularities as described above on the surface. Thereby, it has very excellent press formability and good post-painting sharpness, and the press formability and post-painting sharpness can be obtained uniformly over the entire surface-treated steel sheet.
The surface-treated steel sheet of the present invention is suitably used as an outer panel for automobiles, electrical appliances, etc. after being subjected to press molding or painting.

  Moreover, in the above, although the example which used the roll for cold rolling of this invention for the temper rolling of a surface-treated steel plate was described, the roll for cold rolling of this invention may be used for other cold rolling. . For example, you may use for the temper rolling of the steel plate which is not surface-treated, and you may use for cold rolling other than temper rolling.

  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.

  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. In addition, a temper rolling roll having a diameter of 500 mm and a material for forming irregularities on a cylindrical roll outer peripheral surface made of cold tool steel SUJ2 (JIS G4805) 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 the temper rolling roll. Further, in Example 1, by ultrashort pulse laser processing with a pulse width of 180 to 190 fs, it is formed on the outer peripheral surface of the roll from one end in the axial direction of the roll to the other end in parallel to the axial direction of the roll. The cross-sectional shape in the direction perpendicular to the axial direction of the roll is V-shaped, and a plurality of grooves having a depth d of 6 μm and an angle θ of 118 degrees are continuously formed without any interval, and the outer peripheral surface of the roll The roll provided in the whole was used as a temper rolling roll. In Example 2, an ultrashort pulse laser processing with a pulse width of 180 to 190 fs, a roll in which a semispherical depression having a diameter y of 40 μm is provided on the entire outer peripheral surface of the roll at an interval of 20 μm on the outer peripheral surface of the roll. Used as. About each temper rolling roll, Ra, PPI, and Wa were each measured with the above-mentioned measuring method. In Example 1 in which a V-shaped groove was provided, PPI was measured in a direction perpendicular to the direction in which the V-shaped groove was provided (A-A line in FIG. 2), and Example 2 in which a hemispherical depression was provided. Then, PPI was measured in the direction passing through the depression (CC line in FIG. 5). The results are shown in Table 1. Immediately before the temper rolling mill, water lubrication was sprayed on the front and back surfaces of the steel sheet, and cold rolling with an elongation rate of 1% was performed 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, in the tempered rolls of Examples 1 and 2, Ra was 1 to 10 μm, Wa was 0.01 to 0.1 μm, and PPI was 300 to 2000. Specifically, in Example 1, Ra was 1.72 μm, Wa was 0.0467 μm, and PPI was 1244, and in Example 2, Ra was 2.75 μm, Wa 0.0596 μm, and PPI was 406. Moreover, the uneven | corrugated distribution of Examples 1-2 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. Moreover, the uneven distribution of Comparative Examples 1 and 2 was random and irregular.

  In the surface-treated steel sheet after temper rolling, in Example 1, Ra is 0.99 μm, Wa is 0.12 μm, and PPI is 1016. In Example 2, Ra is 2.12 μm and Wa is 0. .56 μm and PPI was 406. Moreover, the uneven distribution of the surface-treated steel sheets of Examples 1 and 2 was regular and uniform. On the other hand, in Comparative Example 1, Ra was 1.10 μm, Wa was 1.57 μm, and PPI was 177. In Comparative Example 2, Ra was 1.31 μm, Wa was 0.89 μm, and PPI was 203. Moreover, the uneven distribution of the surface-treated steel sheets of Comparative Examples 1 and 2 was random and irregular.

  Furthermore, a sliding test was performed with a testing machine as shown in FIG. 7 as an evaluation of the press formability of the surface-treated steel sheet after temper rolling. In the sliding test, a pressing force P is applied to an upper and lower pressing piece having a radius of curvature of 20 mmR, and a test piece having a width of 20 mm and a length of 300 mm taken from the surface-treated steel sheet after temper rolling is drawn out in the direction of the arrow. The force D is measured. 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 coefficient of friction μ was determined by μ = pulling force / (2 × pressing force). The results are shown in FIG. The surface-treated steel sheet after temper rolling has a friction coefficient of 0.16 in Comparative Example 1, a friction coefficient of 0.15 in Comparative Example 2, and a friction coefficient of 0.11 in Example 1 of the present invention. 2, the coefficient of friction was 0.12.

  In addition, the sharpness after coating is applied to the surface-treated steel sheet after temper rolling by phosphate treatment, electrodeposition coating (20 μm), intermediate coating (35 μm), top coating (35 μm), and clear coating (25 μm). The NSIC values of the coated plates prepared in order were evaluated by measuring them using a mapping sharpness meter (HA-NSIC manufactured by Suga Test Instruments). NSIC value is 100 for blackboard polished glass, and the closer the value is to 100, the better the visibility. The results are shown in FIG. The surface-treated steel sheet after temper rolling has an NSIC value of 28 in Comparative Example 1, an NSIC value of 41 in Comparative Example 2, an NSIC value of 75 in Example 1 of the present invention, and an NSIC value in Example 2. 52.

  As described above, Examples 1 and 2 have the same or larger Ra as compared with Comparative Examples 1 and 2, and PPI is remarkably large. Therefore, Examples 1 and 2 are very excellent in terms of press formability. I understand that. Moreover, since Examples 1-2 are remarkably small compared with Comparative Examples 1-2, it turns out that Examples 1-2 are very excellent also about the clearness after coating. Therefore, it can be said that Examples 1-2 were able to achieve both excellent press formability and improved post-paint clarity.

  In addition, using a roll obtained by generating a DLC hard film on the surface of each tempered roll produced in the same manner as in Example 1 and Example 2, the actual operation with a rolling distance of 3 km was used. When the test was carried out, it was confirmed that the unevenness on the surface was not worn by the DLC hard film, and the unevenness before temper rolling was maintained. On the other hand, when an actual operation test with a rolling distance of 1 km was carried out using the tempered rolling rolls having no DLC hard coating of Examples 1 and 2, the rolling distance was 1 km although there was no problem with the temper rolling. In the vicinity, initial wear of irregularities occurred.

DESCRIPTION OF SYMBOLS 10 Roll for cold rolling 11 Outer peripheral surface 21 Groove 22 Non-groove part 31 Depression 101 Surface treatment steel plate 102a, 102b Spray nozzle 103a, 103b Work roll

Claims (11)

  A roll for cold rolling, characterized in that the surface has an arithmetic average roughness Ra of 1 to 10 μm, an arithmetic average waviness Wa of 0.01 to 0.1 μm, and a peak number PPI per inch of 300 to 2000.   The roll for cold rolling according to claim 1, wherein a plurality of grooves having a V-shaped cross section with a depth of 5 to 10 μm and an angle of 60 to 120 ° are provided substantially parallel to each other on the surface. .   The roll for cold rolling according to claim 1, wherein a plurality of hemispherical depressions having a diameter of 10 to 40 μm are provided on the surface at intervals of 5 to 20 μm.   The roll for cold rolling according to any one of claims 1 to 3, wherein the surface has a film harder than the base material of the roll for cold rolling.   The roll for cold rolling according to claim 4, wherein the coating is diamond-like carbon.   It is a temper rolling roll, The roll for cold rolling as described in any one of Claims 1-5 characterized by the above-mentioned.   It has the process of irradiating the surface of a cylindrical roll with the ultrashort pulse laser whose pulse width is 100 femtoseconds-10 picoseconds, Cold rolling as described in any one of Claims 1-6 characterized by the above-mentioned. Manufacturing method for a roll.   Using the cold rolling roll according to any one of claims 1 to 6, temper rolling is performed at an elongation of 0.1 to 2.0% on the surface-treated steel sheet. Temper rolling method for treated steel sheets.   A surface-treated steel sheet having a surface having an arithmetic average roughness Ra of 0.5 to 10 μm, an arithmetic average waviness Wa of 0.01 to 0.6 μm, and a peak number PPI per inch of 300 to 2000.   The plurality of streaky protrusions having a triangular cross section having a height of 5 to 10 μm and an apex angle of 60 to 120 ° are provided on the surface substantially parallel to each other. Surface treated steel sheet.   The surface-treated steel sheet according to claim 9, wherein a plurality of hemispherical protrusions having a diameter of 10 to 40 μm are provided on the surface at intervals of 5 to 20 μm.