Electroplated steel sheet with excellent surface appearance and its manufacturing method

Abstract

To provide a zinc-nickel electroplated steel plate and a production method thereof, in which the surface appearance after hairline processing is beautiful, the plate is price competitive to existing stainless steels or vinyl laminated steel plates, and furthermore, a high productivity in a coil polishing line can be ensured.SOLUTION: A zinc-nickel alloy electroplated steel plate includes: a base steel plate; and a zinc-nickel plated layer arranged on at least one of the surfaces of the base steel plate with a hairline pattern formed. The surface roughness of the base steel plate surface forming a boundary face to the zinc-nickel plated layer is 0.7-1.0 μm based on a center line average roughness (Ra) as a reference.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electroplated steel sheet having an excellent surface appearance and a method for producing the same, More specifically, the present invention relates to a zinc-nickel alloy electroplated steel sheet having excellent surface appearance and image clarity, and It relates to a manufacturing method. [Background technology]

[0002] The pure zinc-coated steel sheet has an eta-shaped hexagonal close-packed crystal structure (Hexagona The thin hexagonal plate-like crystal structure (close packing) is aggregated. In the case of zinc-nickel plated steel sheet, the plate-like crystals have disappeared and the surface texture has a granular crystal morphology.

[0003] In addition, zinc-nickel plated steel sheets contain nickel, which is an electrochemically stable and lightweight element. Addition of zinc provides excellent corrosion resistance and high microhardness of the coating layer to pure zinc-coated steel sheets. The excellent corrosion resistance of zinc-nickel plated steel sheets is due to the selective corrosion of zinc during the corrosion process. The first step is the formation of zinc hydroxide corrosion products on the surface, and the second step is the formation of a nickel-enriched layer on the bottom. This is because the formation of zinc-nickel alloys suppresses the formation of red rust caused by the dissolution of the base iron. The increase in microhardness with increasing nickel content in the coating layer of nickel-coated steel sheets is not linear. The results show a nonlinear behavior with a sharp increase in the gamma phase alone.

[0004] Recently, carbon steel plated steel sheets have been used to apply hairline patterns to the surface of the steel sheets. Steel sheets with a surface appearance similar to that of stainless steel due to the addition of a turn are used in the field of visual appliance materials. In this way, hairline pattern steel sheets with polished plating layers have been attracting attention. For stainless steel or vinyl coated metal This has the advantage that it is possible to achieve the same or better surface appearance at a lower manufacturing cost.

[0005] It ensures clear hairline patterns when processing plated steel sheets, and has excellent polishing properties. To ensure the abrasive efficiency, the plating layer must be hard and corrosion resistant. Electrogalvanized steel sheet (EG) and molten zinc are attracting attention as rivals to nickel-plated steel sheet. In the case of lead-plated steel sheet (GI), the hardness of the plating layer is 60 to 70 Hv, and the zinc-nickel The surface polishing efficiency and surface appearance after polishing are both poor. There is a point.

[0006] In addition, electrolytic zinc-coated steel sheets and hot-dip zinc-coated steel sheets are vulnerable to the formation of white rust, so During transportation and storage of the steel sheet, corrosion products in the form of white rust formed on the surface remain on the steel sheet surface even after polishing. Not only does this impair surface quality, but the amount of plating remaining after polishing is smaller than before polishing. However, under unfavorable conditions, rapid corrosion will occur, resulting in deterioration of the surface appearance.

[0007] Improves surface appearance such as image clarity and gloss after hairline processing of zinc-nickel plated steel sheet Various researches are being conducted to improve the physical properties of the plating layer before and after hairline processing. In reality, there is insufficient consideration of correlations that take into account changes in characteristics. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been devised in view of the above-mentioned circumstances, and provides a method for producing a surface after hairline processing. Zinc-nickel alloy electroplated steel sheet with beautiful surface appearance and excellent image clarity and its manufacturing method Provide the law. [Means for solving the problem]

[0009] According to one aspect of the present invention, there is provided a base steel sheet; and a heat-insulating film disposed on at least one surface of the base steel sheet. The zinc-nickel plating layer includes a zinc-nickel plating layer having an aligning pattern formed thereon. The surface roughness of the base steel sheet surface that forms the interface with the coating layer is based on the center line average roughness (Ra). A zinc-nickel alloy electroplated steel sheet having a thickness of 0.7 to 1.0 μm is provided.

[0010] The zinc-nickel plating layer is gamma (Ni5Zn 21 ) consists of a single phase It is possible.

[0011] The zinc-nickel plating layer may have a hardness of 250 to 400 Hv.

[0012] According to another aspect of the present invention, a method for producing a steel sheet comprising the steps of: temper rolling a base steel sheet; The sheet is immersed in a sulfuric acid bath containing nickel sulfate hydrate and zinc sulfate hydrate to deposit a layer on the base steel sheet. forming a zinc-nickel plating layer; and coating the zinc-nickel plating layer with a polishing agent. Manufacture of zinc-nickel alloy electroplated steel sheet including the steps of processing with a hairline pattern and A method is provided.

[0013] The temper rolling step is carried out using an electric discharge roll in capacity (-) mode. This can be done.

[0014] The surface of the roll may be coated with chromium.

[0015] The temper rolling step may be performed at a drawing rate of 0.3 to 1.2%.

[0016] The surface roughness of the above temper rolled base steel sheet surface is based on the center line average roughness (Ra). It can be 0.7 to 1.0 μm.

[0017] The zinc-nickel plating layer formed on the above-mentioned base steel sheet is gamma (Ni5Zn 21 )single It may consist of one phase.

[0018] The hardness of the zinc-nickel plating layer formed on the base steel sheet is 250 to 400 Hv. It is possible.

[0019] The center line average of the zinc-nickel plating layer after the above polishing and hairline pattern processing The variation in roughness can be from -1.00 to -0.35 μm.

[0020] The rate of change in surface roughness of the zinc-nickel plating layer by the above polishing is 60 to 85%. The rate of change in the surface roughness of the zinc-nickel plating layer due to hairline pattern processing is 1 It can be 5-40%.

[0021] The thickness of the plating layer after the above polishing and hairline pattern processing is The thickness may be 0.2 to 0.75 times the thickness of the plating layer before the align pattern processing. Effect of the Invention

[0022] According to the present invention, the surface appearance after hairline processing is beautiful, and the existing surface appearance is improved. Not only is it price-competitive with stainless steel or vinyl laminated steel, but it also has coil grinding capabilities. Zinc that can ensure high productivity in the Coil Polishing Line Nickel electroplated steel sheet and a method for its manufacture are provided. [Brief description of the drawings]

[0023] [Figure 1] 1 shows an image of a steel sheet surface after polishing and hairline processing according to the present invention and an analysis result at 2,000 times magnification using a scanning electron microscope (SEM), where (a) shows Example 1 and (b) shows Comparative Example 1. [Diagram 2] 1 shows the results of analyzing the roughness profile in the direction perpendicular to the rolling direction of a steel sheet before and after polishing and hairline processing according to Example 1 of the present invention, where (a) shows the state before processing and (b) shows the state after processing. [Diagram 3] 1 shows the results of analyzing the roughness profile in the direction perpendicular to the rolling direction of a steel sheet before and after polishing and hairline processing according to Comparative Example 1 of the present invention, where (a) shows the state before processing and (b) shows the state after processing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Preferred embodiments of the present invention will now be described with reference to various examples. The disclosed embodiment may be modified into several other forms, and the scope of the present invention will be described below. The present invention is not limited to the embodiments described above.

[0025] The present invention relates to an electroplated steel sheet having an excellent surface appearance and a method for producing the same, More specifically, the present invention relates to a zinc-nickel alloy electroplated steel sheet having excellent surface appearance and image clarity, and It relates to a manufacturing method.

[0026] Zinc-nickel alloy electroplated steel sheets with hairline patterns are usually In the polishing line, polishing, hairline polishing, brushing, surface cleaning, and heat After the air drying process, the product is painted on the color coating line to complete the final product. The inventors have been working on the development of a new product after hairline processing of zinc-nickel plated steel sheet. During various studies on improving the surface appearance such as image clarity and gloss, zinc-nickel plating The hardness of the coating, the surface roughness of the raw material before polishing and hairline processing are It is a major factor that affects productivity and surface appearance such as gloss and image clarity after processing. The above-mentioned points have been confirmed, and the present invention has been completed.

[0027] According to one aspect of the present invention, there is provided a base steel sheet; and a heat-insulating film located on at least one surface of the base steel sheet. The zinc-nickel plating layer includes a zinc-nickel plating layer having an aligning pattern formed thereon. The surface roughness of the base steel sheet surface that forms the interface with the coating layer is based on the center line average roughness (Ra). A zinc-nickel alloy electroplated steel sheet having a thickness of 0.7 to 1.0 μm is provided.

[0028] The type of the base steel sheet is not particularly limited, and may be a hot-rolled steel sheet, a cold-rolled steel sheet, or the like, as long as the technology to which the present invention pertains is applicable. As long as it can be used in the field of the present invention, it does not matter which one is used. In the above-mentioned method, the base steel sheet is subjected to electroplating of zinc or nickel particles during zinc-nickel electroplating. The surface roughness of the coated steel sheet is determined by the adhesion characteristics, as described below. A preferred rolling method in the temper rolling process that determines the final surface roughness and the associated It is necessary to set the surface roughness of the base steel sheet.

[0029] At least one surface of the base steel sheet is coated with a zinc-nickel plating formed by electroplating. A zinc-nickel plating layer is formed on the surface of the zinc-nickel plating layer, and a hairline pattern is formed on the zinc-nickel plating layer. It can be said that it is.

[0030] The surface roughness of the surface of the base steel sheet that forms the interface with the zinc-nickel plating layer is the center line average The roughness (Ra) is preferably 0.7 to 1.0 μm. In this case, the surface roughness is uniform during plating, but the plating adhesion deteriorates. On the other hand, when the surface roughness exceeds 1.0 μm, the plating material is the same as the base steel. The surface roughness increases due to the influence of the roughness characteristics of the plate, which results in the outer surface of the hairline processing. However, it has the disadvantage that the appearance of the surface deteriorates after the hairline processing. Considering the increase in surface roughness of the base steel sheet after lead-nickel electroplating, The surface roughness is more preferably 0.7 to 0.9 μm.

[0031] The zinc-nickel plating layer formed on the above-mentioned base steel sheet is gamma (Ni5Zn 21 )single It is preferably made of one phase. It ensures good corrosion resistance in electroplating of zinc-based alloys. In order to achieve this, it is necessary to estimate the corrosion rate of zinc, which is electrochemically active in a corrosive environment. It is necessary to reduce the corrosion rate and maintain the sacrificial corrosion protection for a long time. phase, not only is the gamma phase electrochemically stable, but also mixtures such as eta + gamma Since there is no galvanic corrosion caused by the potential difference between the crystal phases, excellent corrosion resistance is ensured. In addition, the nickel content in the plating layer increases in the region of the gamma single phase. The hardness of the plating layer is rapidly improved, making it easier to ensure a high hardness of the plating layer.

[0032] In particular, as described later, in the present invention, in order to form a zinc-nickel plating layer on a base steel sheet, The applied acid bath has a non-uniform nickel distribution through the thickness compared to the alkaline bath, and the surface The nickel content gradually increases from the coating layer to the interface of the base steel sheet. The higher the nickel content in the plating layer, the greater the nickel depletion in the surface region. This reduces the area of ​​the surface where hairline polishing is performed. Therefore, it is possible to achieve substantially high hardness of the plating layer and an excellent surface appearance associated therewith.

[0033] In addition, the hardness of the zinc-nickel plating layer formed on the base steel sheet of the present invention is 250 to 40 0Hv. When the hardness of the zinc-nickel plating layer is less than 250Hv, During hairline pattern processing, part of the plating layer is peeled off, resulting in uniform hairline in the rolling direction. This hinders the formation of a rolling pattern, increases the rolling force on the material, and causes fine grains in the surface structure during operation. The higher the hardness of the plating layer, the easier it is to polish the surface. It is highly efficient, but when the hardness of the zinc-nickel plating layer exceeds 400Hv, While there is only a slight improvement in the ease of surface polishing, the zinc content in the plating layer is relatively high. The increase in nickel content, which is relatively expensive, increases the residual stress in the zinc-nickel plating layer. This causes fine cracks on the surface, which reduces price competitiveness. do not have.

[0034] According to another aspect of the present invention, a method for producing a steel sheet comprising the steps of: temper rolling a base steel sheet; The sheet is immersed in a sulfuric acid bath containing nickel sulfate hydrate and zinc sulfate hydrate to deposit a layer on the base steel sheet. forming a zinc-nickel plating layer; and polishing the zinc-nickel plating layer. Manufacture of zinc-nickel alloy electroplated steel sheet including the steps of processing with a hairline pattern and A method is provided.

[0035] First, a base steel sheet is prepared. The base steel sheet is pretreated by degreasing or pickling. The cleanliness of the surface can be ensured, and the pretreatment conditions are not particularly limited in the present invention. stomach.

[0036] The above-mentioned base steel sheets are affected by the electrodeposition characteristics of zinc or nickel particles during zinc-nickel electroplating. In order to determine the surface roughness of the plated steel sheet, the final surface roughness of the base steel sheet is determined. The present invention provides a method for rolling steel sheets in a temper rolling process and a method for improving the surface roughness of the steel sheets. It is necessary to determine this.

[0037] Thus, the step of temper rolling the base steel sheet is performed by discharge heating in capacity (-) mode. In the processing method using temper rolls, Shot blasting is a process that uses metal grit to The physical method is to project grit onto the roll surface to give it roughness, whereas the discharge method is to apply electric discharge. The process removes particles from the roll surface by electrical sparks between the roll and an electrode in an insulating liquid to reduce the roughness. Therefore, the rolls manufactured by the EDM method have a short circuit. The rolls manufactured through hot blasting have increased uniformity of roughness and reduced deviation of roughness. This has the advantage of reducing the amount of light emitted by the lens and providing excellent image clarity.

[0038] In addition, in the EDM mode, the capacity (+) and impulse (-) modes are The reproducibility of roughness during work is worse than other modes, and the workability of the Impulse (+) mode is Although it has excellent roughness, it has the largest number of peaks per unit length, which is less than that of zinc-nickel electroplating. The disadvantage of this is that it hinders uniform electrodeposition during machining, so the EDM process in capacity (-) mode is It is preferable to use a rolling mill to temper roll the base steel sheet.

[0039] At this time, the service life of the roll is extended to flatten the roll roughness caused by the passage of time. In order to reduce the surface roughness deviation between the workpieces and the associated surface roughness deviation, the surface of the roll is coated with chrome. It is more preferable to coat the

[0040] Meanwhile, in consideration of the surface roughness and strength of the steel sheet, the temper rolling step is performed in a range of 0.3 to 1.2 It is preferable that the stretching ratio during temper rolling is less than 0.3%. If the transfer rate is less than 100%, the effect of adjusting the surface roughness of the base steel sheet becomes insufficient due to the decrease in the transfer rate. On the other hand, if the elongation rate during temper rolling exceeds 1.2%, the surface roughness of the base steel sheet increases. In both cases, work hardening occurs due to potential multiplication, which increases the yield strength and However, there is a problem in that processing cracks occur during press molding.

[0041] As described above, the surface roughness of the temper-rolled base steel sheet surface is calculated based on the centerline average roughness (Ra). The preferred thickness is 0.7 to 1.0 μm. If the thickness is less than 0.7 μm, the plating Although the surface roughness is uniform, the coating adhesion is deteriorated. If the surface roughness exceeds 1.0 μm, the plated material will be affected by the roughness characteristics of the base steel sheet. This increases the surface roughness, which deteriorates the surface appearance after hairline processing. However, it has the disadvantage of being difficult to maintain a beautiful surface appearance after hairline processing and to use zinc-nickel electrodes. Considering the increase in surface roughness of the base steel sheet after electroplating, the surface roughness of the base steel sheet is 0 It is more preferable that it is 0.7 to 0.9 μm.

[0042] The above-mentioned temper rolled base steel sheet is immersed in a sulfuric acid bath containing nickel sulfate hydrate and zinc sulfate hydrate. The zinc-nickel plating layer is formed on the base steel sheet by immersion. The method for forming the coating layer is not particularly limited. For example, the base steel sheet is vertically coated with a coating material. After placing it at the negative electrode of a tube-type electroplating simulator, a sulfuric acid bath plating solution was circulated. A zinc-nickel plating layer is formed on one side by the same method as above, and a zinc-nickel plating layer is formed on the other side by the same method as above. A method for forming a galvanic plating layer can be used.

[0043] The sulfuric acid bath is preferably an acidic bath having a pH of 0.5 to 3.5. High electrical conductivity in alkaline baths allows high current efficiency and thick films can be formed in the normal current density range. The alloying elements are distributed unevenly along the thickness direction. The zinc-nickel alloy electroplated steel sheet has a zinc-nickel plating on the surface of the plating layer. The distribution shows that the nickel content increases toward the interface of the zinc-nickel layer. As corrosion progresses, nickel-enriched lamellar layers form on nickel-alloy electroplated steel sheets. In the case of acid bath, the base steel sheet and the solder joint are formed and corrosion is suppressed. The nickel concentration at the interface of the zinc-nickel plated steel sheet is relatively high, and the corrosion resistance of the zinc-nickel plated steel sheet is improved. The strengthening mechanism is the nickel-enriched layer, which is strengthened after polishing and hairline polishing. This also contributes to ensuring stable corrosion resistance.

[0044] In addition, under acidic bath conditions, nickel sulfate or carbonate, which are the nickel sources for zinc plating baths, Nickel dissolution is fast, so in commercial production, raw materials are not yet used for nickel replenishment. To prevent surface defects such as dents caused by dissolved particles, an acid bath is more effective than an alkaline bath. It is beneficial.

[0045] The sulfuric acid bath contains 40 to 60 g / L of nickel sulfate hydrate and 60 to 90 g / L of zinc sulfate hydrate. It is preferable that the content of nickel sulfate hydrate is less than 40 g / L and the content of zinc sulfate aqueous solution is less than 40 g / L. If the amount of hydrate exceeds 90 g / L, the hardness of the zinc-nickel plating layer formed is 250 Hv This may result in part of the plating layer peeling off during hairline pattern processing. This prevents the uniformity of the hairline pattern in the rolling direction from being achieved, and increases the rolling force on the material. The problem is that fine craters are generated in the surface structure during operation. When zinc sulfate hydrate exceeds 60g / L and zinc sulfate hydrate is less than 60g / L, the zinc- The hardness of the nickel plating layer can exceed 400Hv, which makes the surface easier to polish. While the additional improvement in corrosion resistance is small, the relatively expensive nickel is used in comparison with the zinc in the plating layer. The increase in zinc content increases the residual stress in the zinc-nickel plating layer, which leads to the surface roughness. This is undesirable because it causes fine cracks on the surface and reduces price competitiveness.

[0046] The hardness of the zinc-nickel plating layer thus formed is 250 to 400 Hv. In the case where the hardness of the zinc-nickel plating layer is less than 250Hv, it is preferable to use a hairline. During pattern processing, part of the plating layer peels off, making it difficult to ensure a uniform hairline pattern in the rolling direction. This hinders the maintenance of the material, increases the rolling force on the material, and causes fine craters to form in the surface structure during operation. The higher the hardness of the plating layer, the easier it is to polish the surface, and the higher the efficiency. However, if the hardness of the zinc-nickel plating layer exceeds 400Hv, surface polishing is required. While there is only a small improvement in the ease of plating, it is relatively expensive compared to the zinc in the plating layer. The increase in nickel content increases the residual stress in the zinc-nickel plating layer. This is undesirable because it causes fine cracks on the surface and reduces price competitiveness.

[0047] In addition, the zinc-nickel plating layer is gamma (Ni5Zn 21 It is preferable that the material is made of a single phase. In order to ensure good corrosion resistance in electroplating of zinc-based alloys, the corrosion ring It reduces the corrosion rate of zinc, which is electrochemically active under environmental conditions, and acts as a sacrificial protection. It is necessary to maintain feeding habits for a long time. In this respect, if the gamma monophasic Not only are the phases electrochemically stable, but the potential difference between the crystalline phases in mixed phases such as eta + gamma Since there is no galvanic corrosion caused by the above, excellent corrosion resistance can be ensured. In addition, the hardness of the plating layer increases with increasing nickel content in the gamma single phase region. This dramatically improves the hardness of the plating layer, making it easier to ensure high hardness.

[0048] Next, the zinc-nickel plating layer is polished and processed into a hairline pattern. The above polishing and hairline pattern processing are performed using a commonly used abrasive belt. The method can be performed using, but is not limited to, the following.

[0049] Polishing is to flatten the material before hairline processing and to improve the gloss of the material after hairline processing. The amount of plating that is polished by adjusting the degree of rolling force, i.e., the amount of plating remaining after processing, is In the case of hairline processing, it plays a role in determining the amount of It serves to impart a hair-like pattern to the surface of zinc-nickel plated steel sheet.

[0050] More specifically, the polishing base is used from the viewpoint of removing the surface plating layer and ensuring the flattening effect. The rotation speed of the belt is faster than that of the hairline abrasive belt. It is preferable that the surface roughness of the hairline polishing belt is larger than that of the hairline polishing belt.

[0051] Accordingly, the total change in surface roughness after polishing and hairline processing was When the total surface roughness is taken as 100%, the contribution rate of polishing to the change in surface roughness is 60-85%. The contribution rate of change in surface roughness due to hairline pattern processing is preferably 15 to 40%. If the contribution rate of the polishing to the change in surface roughness is less than 60%, the degree of flattening of the surface roughness is insufficient. If the loss rate exceeds 85%, it is difficult to ensure a beautiful surface appearance after processing. The loss is so great that the remaining plating amount is not reached and craters appear on the surface of the plating layer. On the other hand, the change in surface roughness of the hairline pattern processing may occur. If the contribution rate of oxidation is less than 15%, the hairline pattern on the steel sheet surface is not easily recognized by the naked eye. If it exceeds 40%, the surface roughness will be increased due to the unevenness of the hairline pattern profile. There is a problem in that the appearance is deteriorated.

[0052] The change in surface roughness after polishing and hairline processing compared to before was calculated as follows: It can be derived using a formula. Contribution rate of change in surface roughness due to polishing = (Ra before processing - Ra after polishing) x 100 / ( Before processing Ra - After processing Ra) Contribution rate of change in hairline surface roughness = (Ra after polishing - Ra after hairline) x 100 / (Ra before processing - Ra after processing)

[0053] On the other hand, the center of the zinc-nickel plating layer after the above polishing and hairline pattern processing The change in linear average roughness is preferably -1.00 to -0.35 μm. If the rolling force is less than 100%, the increase in rolling force to flatten the surface may cause fine cracks or cracks in the plating layer. On the other hand, if the difference is more than -0.35μm, the surface flatness is poor. The effect of smoothing is insufficient, or the depth of peaks and valleys on the roughness profile in the vertical direction of rolling is too small. The problem is that the surface quality deteriorates as the surface roughness increases. The roughness profile in the transverse direction should be regular and uniform sine curve. is preferred.

[0054] The thickness of the plating layer after the above polishing and hairline pattern processing is It is preferable that the thickness of the plating layer before the align pattern processing is 0.2 to 0.75. That is, the thickness of the plating layer after the above polishing and hairline pattern processing and the polishing and It is preferable that the ratio of the thickness of the plating layer before and after hairline pattern processing is 0.2 to 0.75. If it is less than 0.2, the plating thickness of the raw material before polishing and hairline processing is thick. Or the plating thickness of the processed material is thin, which increases manufacturing costs and requires removal through grinding. Not only does the increased plating amount increase the load during coil polishing, but it also reduces the corrosion resistance of the processed material. On the other hand, if it exceeds 0.75, the polishing effect is small and The drawback is that it is difficult to ensure a beautiful surface appearance.

[0055] The zinc-nickel electroplated steel sheet of the present invention as described above can be polished, It has excellent gloss and image clarity after coating, and realizes a hairline pattern surface appearance. Not only is it more cost-competitive than stainless steel or vinyl laminated steel, High productivity can be ensured by high speed operation of the coil polishing line. EXAMPLES

[0056] (Example) The present invention will be described in more detail below with reference to examples. It is intended for purposes of clarification and is not intended to limit the invention.

[0057] Using a temper rolling tester, the temper rolling roll processing method, processing mode and elongation rate are controlled. The base steel plate (ultra-low carbon Steel) was manufactured.

[0058] After this, zinc sulfate heptahydrate and nickel sulfate hexahydrate that had been degreased and pickled were added, and the mixture was electrochemically A zinc-nickel plating layer was formed on the base steel sheet through electroless plating. The base steel sheet was placed at the negative electrode of a vertical plating cell type electroplating simulator, and then the plating The solution is circulated to form a zinc-nickel plating layer on one side, and then the same process is carried out on the other side. The zinc-nickel plating layer is formed in a variety of ways to control the plating weight on both sides of the base steel sheet. Ta.

[0059] When forming the above plating layer, the pH of the plating bath was 1.5 to 2.5, and the current density was 100 A / dm 2. The flow rate is 1.5 m / s. The sulfuric acid bath contains sodium sulfate to compensate for the conductivity of the plating bath. Thorium was added at 30 g / L.

[0060] After this, the zinc-nickel plating layer is formed in the polishing and hairline processing device. The zinc-nickel plated steel sheet was then passed through the wire to finally achieve the hairline pattern. The polishing belt and the hairline polishing belt were set at 120 The manufacturing conditions for each test piece are shown in Tables 1 and 2 below. He explained it in a logical manner.

[0061] [Table 1]

[0062] [Table 2]

[0063] The zinc-nickel plated steel sheets manufactured as above were used to measure the microhardness and The physical properties of the steel sheet and the crystalline phase were analyzed to determine the effect of the surface appearance when the hairline pattern was formed. The hardness of the plating layer was measured using an ultra-micro hardness tester (Shimadzu, DUH-W The crystalline phase of the plating layer was measured using an X-ray diffraction analyzer. (Rigaku, D / MAX 2500V / PC) with CuKα radiation at 40kV After irradiating the specimen with an accelerating voltage, the acquired peaks were analyzed by JCPDS.

[0064] In addition, to investigate the effect of the elongation rate of temper rolling on the yield strength of the steel plate, After processing it into KS 13B, it was subjected to an Instron tensile test in the yield zone. 10MPa / s until yielding, deformation rate after yielding 0.007s -1 The yield strength was evaluated.

[0065] The zinc-nickel plated steel sheet manufactured as above and the polishing and hairline treatment materials The plating layer was dissolved using a diluted hydrochloric acid solution, and the weight difference before and after was analyzed to determine the change in plating amount. We confirmed that the system was

[0066] In addition, the surface structure of the test pieces was measured for some of the polished and hairline processed materials. The samples were analyzed using a JEOL JSM-7001F field emission scanning electron microscope (FE-SEM) and The causes of the differences in surface appearance, such as image quality, were analyzed.

[0067] Furthermore, the above-mentioned uncoated steel sheets, zinc-nickel-coated steel sheets, Veeco Integrator is used for hairline processing materials after polishing and polishing alone. A three-dimensional non-contact roughness measuring device (Mfg. instruments) was used to measure the roughness of the surface by measuring 2.4 mm wide and 1.8 mm long. The roughness of the areas was measured to determine the change in the surface roughness of the steel sheet due to the process.

[0068] In addition to the above analysis items for each process step, corrosion resistance, image clarity, and press formability are measured. The results are shown in Table 3. The corrosion resistance, image clarity, and press formability were evaluated as follows. It is.

[0069] 1.Corrosion resistance Corrosion resistance (red rust occurrence rate) was measured by cutting the test piece into a size of 75 x 150 mm and then attaching the ends to a tape. Fluorocarbon tape (Nitto Denko Corp. NITOFLON, No. 903U The test pieces were masked with a salt spray tester STP-200 (SUGA Te st Instruments, Japan, and JIS (Japanese Industrial Standards (Japa In accordance with Industrial Standards Z 2371, Progress (5% sodium chloride, 1-2ml spray volume per hour, chamber temperature 35℃) If the result is between 0% and 10%, it is considered very good, and if it is between 10% and 40%, it is considered good. , 40% to 70% was rated as normal, and over 70% was rated as insufficient.

[0070] 2. Imageability Image clarity was measured using a Rh A Distance Imaging (DOI) measuring instrument was installed. The method used was to measure the quantification of image quality.

[0071] If the DOI value is over 30, it is very good. If it is over 20-30, it is good. If it is 10, it is good. A score of up to 20 was rated as fair, and a score of less than 10 was rated as inadequate.

[0072] 3. Press formability Press formability was evaluated by painting some test pieces of the hairline and polished material. For the final material, use VS&Ein Chemical's MVP 840TW non-water-soluble plastic processing oil. After application, the SIMPAC 250 ton servo press (SV1P-250) The steel plate was pressed with a load of 13 tons using a press machine to confirm the results. The occurrence rate of paint damage was calculated by dividing the length of the paint peeling on the side of the ridge by the entire circumference. In this case, even if peeling occurs only on the bead or drawing part, it is considered that there is no paint peeling. It was determined to be a distance.

[0073] The evaluation method is as follows: if the incidence of paint damage is less than 10%, it is considered excellent, and if it is between 10% and 20%, it is considered poor. Generally, cases exceeding 20% ​​were rated as insufficient.

[0074] [Table 3]

[0075] Referring to Tables 1 to 3 above, in the case of Examples 1 to 5 which satisfy the conditions proposed by the present invention, It can be seen that the alloy has excellent corrosion resistance, image clarity, and press workability. In the case of ~16, the present invention proposes temper rolling, zinc-nickel electroplating, and polishing. , and the hairline polishing conditions are not met, so corrosion resistance, image clarity, and press workability are poor. It can be seen that the above is not secured.

[0076] Specifically, in the cases of Comparative Examples 1 to 5 and Comparative Example 13, the temper rolling conditions proposed by the present invention ( Roll processing method and processing mode, temper rolling elongation rate and associated steel sheet roughness) Therefore, excellent levels of corrosion resistance, image clarity, and press workability are not ensured at the same time. In particular, it can be seen that the yield strength of the base steel sheet increases as the elongation ratio of the temper rolling increases. However, the zinc-nickel plating layer has a much higher hardness than the typical pure zinc plating layer. The deformation of the base steel sheet is restricted by the coating layer, which deteriorates the formability of the final product. It is important to control the elongation rate of skin pass rolling to an appropriate level because it can be a major factor in the It can be seen that is important.

[0077] In the case of Comparative Examples 6 to 12, the zinc-nickel electroplating conditions proposed by the present invention (zinc sulfate) were used. The amount of lead and nickel sulfate hydrate, plating time (plating amount), hardness of the plating layer, and crystalline phase) As a result, it is not possible to simultaneously ensure excellent levels of corrosion resistance and image clarity. You can see that.

[0078] In the cases of Comparative Examples 14 to 16, the polishing and hairline polishing steps were Since the contribution rate of the change in surface roughness does not satisfy the conditions proposed by the present invention, the corrosion resistance and It can be seen that it is not possible to simultaneously ensure an excellent level of image clarity.

[0079] On the other hand, FIG. 1 shows an image of the surface of a steel sheet after polishing and hairline processing according to the present invention. and Scanning Electron Microscope, The results of the analysis using a SEM at a magnification of 2,000 times are shown in (a). Example 1, (b) shows Comparative Example 1. Referring to FIG. 1, The steel sheets produced have a clear hairline pattern in the rolling direction on the surface and microstructure, and the surface quality is excellent. In contrast, in the case of Comparative Example 1, the hairline pattern on the surface and fine structure was clear. It can be seen that the surface quality is not excellent.

[0080] FIG. 2 shows the vertical rolling direction of a steel sheet before and after polishing and hairline processing according to Example 1 of the present invention. The results of analyzing the roughness profile in the direction are shown in Fig. 1. (a) is before processing, (b) 3 shows the results before and after polishing and hairline processing according to Comparative Example 1 of the present invention. The results of analyzing the roughness profile of a steel plate in the direction perpendicular to the rolling direction are shown in Fig. 1. (a) is a (b) shows the sample before processing, and (b) shows the sample after processing.

[0081] 2 and 3, the steel plate manufactured according to Example 1 has a rough surface and a roughness of 0.01 mm. It can be seen that the depth of the valley is small and the shape of the curve is regular and uniform. In the case of the steel plate manufactured by Comparative Example 1, the depth of the peaks and valleys is relatively large compared to that of Example 1. Not only that, but the period of the curve is also irregular.

[0082] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto. However, various modifications may be made without departing from the technical spirit of the present invention as set forth in the claims. It will be apparent to one of ordinary skill in the art that various modifications and variations are possible. do.

Claims

1. A step of temper rolling the base steel sheet; immersing the temper-rolled base steel sheet in a sulfuric acid bath containing nickel sulfate hydrate and zinc sulfate hydrate to form a zinc-nickel plating layer on the base steel sheet; and polishing and hairline patterning the zinc-nickel plating layer; The rate of change in surface roughness of the zinc-nickel plating layer by the polishing is 60 to 85%, and the rate of change in surface roughness of the zinc-nickel plating layer by the hairline pattern processing is 15 to 40%, The temper rolling step is performed at a drawing ratio of 0.3 to 1.2%, The surface roughness of the temper-rolled base steel sheet surface is 0.7 to 1.0 μm based on the center line average roughness (Ra), A method for producing zinc-nickel alloy electroplated steel sheet.

2. 2. The method for producing a zinc-nickel alloy electroplated steel sheet according to claim 1, wherein the temper rolling is performed using an electric discharge roll in a capacity (-) mode.

3. 3. The method for producing a zinc-nickel alloy electroplated steel sheet according to claim 2, wherein the surface of the roll is coated with chromium.

4. 2. The method for producing a zinc-nickel alloy electroplated steel sheet according to claim 1, wherein the hardness of the zinc-nickel plating layer formed on the base steel sheet is 250 to 400 Hv.

5. The zinc-nickel plating layer formed on the base steel sheet is gamma (Ni ５ Zinc ２１ 2. The method for producing a zinc-nickel alloy electroplated steel sheet according to claim 1, characterized in that the zinc-nickel alloy electroplated steel sheet is made of a single phase.

6. 2. The method for producing a zinc-nickel alloy electroplated steel sheet according to claim 1, wherein a change in center line average roughness of the zinc-nickel plating layer after the polishing and hairline patterning is −1.00 to −0.35 μm.

7. The method for producing a zinc-nickel alloy electroplated steel sheet according to claim 1, characterized in that the thickness of the plating layer after the polishing and hairline patterning is 0.2 to 0.75 times the thickness of the plating layer before the polishing and hairline patterning.

Images