rolling rolls

Abstract

The present application relates to a roll. A roll according to an embodiment of the present application includes: a roll base material; and a chromium-containing plating layer formed on the roll base material and having a maximum length of a crack formed on a surface of 5 μm or less. A roll according to another embodiment of the present application includes: a roll base material; a chromium-containing plating layer formed on the roll base material; and a first coating layer formed on the chromium-containing plating layer and containing titanium nitride.

Description

Technical Field

[0001] This utility model relates to a roll, a method for manufacturing a roll, and a method for manufacturing an electrode therethrough. More specifically, it relates to a roll, a method for manufacturing a roll, and a method for manufacturing an electrode therethrough, wherein the roll includes a roll substrate and a chromium-containing plating layer formed on the roll substrate and having a maximum length of less than 5 μm for cracks formed on the surface. Background Technology

[0002] The manufacturing process of secondary battery electrodes involves mixing, coating, rolling, slitting and notching, and drying. In particular, the rolling process reduces the thickness of the coated active material electrode, thereby increasing its density. However, during rolling, the active material electrode passes between a pair of upper and lower rolls, and pressure is applied to the rolls to reduce its thickness. This can cause friction between the roll surface and the active material electrode. Consequently, the rolling process leads to wear on the roll surface, resulting in a shortened roll life.

[0003] To prevent this problem, a hard chromium plating layer is typically formed on the roll surface, increasing the roll hardness to approximately 700-900 Hv, thereby reducing roll wear and extending service life. However, hard chromium plating uses a solution (CrO3 and H2SO4) mixed with anhydrous chromic acid and sulfuric acid as the plating bath. Hydrogen residue generated in the plating bath can lead to hydrogen embrittlement due to hydrogen penetration into the substrate, and hair cracks can occur in the plating layer due to residual stress during the plating process. If these hair cracks are large enough for the plating solution to penetrate between the cracks, the plating solution may flow out and remain on the roll surface during the roll heat treatment for dehydrogenation, causing problems when applying additional high-hardness coatings. Furthermore, the possibility of polishing and cleaning solutions penetrating the roll surface during the preparatory processes of polishing and cleaning before applying the additional high-hardness coating cannot be ruled out. Furthermore, if cracks on the coated surface spread due to stress caused by rolling load, the cracks may connect with each other and fall off, becoming a decisive factor in shortening the life of the roll.

[0004] To further increase the service life of the rolls, DLC (diamond-like carbon) or additional WC (tungsten carbide) coating is sometimes deposited on the hard chrome plating to increase the hardness to the 2000 Hv level during rolling.

[0005] DLC utilizes hydrocarbon groups (C) n H nWhile plasma gas deposition can increase hardness to 2000 Hv, the coefficient of friction is too low (0.05), which may cause slippage during rolling. Furthermore, the large number of hydrogen ions and atoms generated by hydrogen-based plasma can lead to hydrogen embrittlement of the substrate when the generated hydrogen diffuses into it.

[0006] WC is primarily applied using thermal spraying. However, due to the relatively large particle size and rough surface of WC, thermal spraying can cause quality defects on rolled electrodes. Although sputtering with acetylene gas (C2H2) and tungsten carbide (WC) can form multilayer stacks of WC and WC / C layers to improve coating life, the use of hydrocarbon-based plasma gases generates a large number of hydrogen ions and atoms. The resulting hydrogen diffuses into the substrate, raising concerns about hydrogen embrittlement. Furthermore, if hydrogen molecules are formed, blistering defects can sometimes occur.

[0007] Therefore, there is a need to develop a roll, a method for manufacturing the roll, and a method for manufacturing electrodes therethrough, wherein the roll, the method for manufacturing the roll, and the method for manufacturing electrodes therethrough can minimize foreign matter defects and hydrogen defects in the final coating by preventing the penetration of plating solution, and the hardness of the final coating is relatively increased, thereby improving wear resistance. Utility Model Content

[0008] Technical issues

[0009] The technical problem to be solved by this utility model relates to providing a roll, a method for manufacturing the roll, and a method for manufacturing electrodes therethrough. Specifically, it relates to a roll, a method for manufacturing the roll, and a method for manufacturing electrodes therethrough, wherein the roll includes a chromium-containing plating layer formed on the roll substrate and having a maximum crack length of less than 5 μm on the surface.

[0010] The technical problems to be solved by this utility model are not limited to the above-mentioned problems. Those skilled in the art to which this utility model pertains can clearly understand the problems not mentioned through this specification and the accompanying drawings.

[0011] Technical solution

[0012] According to one embodiment of the present invention, a roll includes: a roll substrate; and a chromium-containing plating layer formed on the roll substrate and having a maximum length of less than 5 μm for cracks formed on the surface.

[0013] The roller substrate may have surface irregularities with a maximum height of 5 μm to 25 μm.

[0014] The roller substrate may contain chrome steel.

[0015] The thickness of the chromium-containing coating can be from 100 μm to less than 150 μm, and the hardness of the chromium-containing coating can be from 1000 Hv to less than 1300 Hv.

[0016] The residual hydrogen density of the chromium-containing plating can be 0.1 ppm / cm³. 3 Up to 0.25 ppm / cm 3 the following.

[0017] The roll according to this embodiment may further include a coating formed on the chromium-containing plating, the coating may include a metal nitride.

[0018] The coating may include a chromium nitride layer formed on the chromium-containing plating and a titanium nitride layer formed on the chromium nitride layer.

[0019] The coating may also include a chromium coating located between the chromium-containing plating layer and the chromium nitride layer.

[0020] According to another embodiment of the present invention, a roll includes: a roll substrate; a chromium-containing plating layer formed on the roll substrate; and a first coating formed on the chromium-containing plating layer and comprising titanium nitride.

[0021] The roll according to this embodiment may further include one or more second coatings formed between the chromium-containing plating and the first coating and containing chromium or its nitride.

[0022] The thickness of the second coating can be from 0.2 μm to less than 1 μm, and the hardness of the second coating can be from 1000 Hv to less than 2000 Hv.

[0023] The first coating may include: a first sub-coating formed on the chromium-containing plating or the second coating and comprising titanium nitride (TiN); a second sub-coating formed on the first sub-coating and comprising titanium-aluminum composite nitride; and a third sub-coating formed on the second sub-coating and comprising titanium carbonitride (TiCN).

[0024] The thickness of the first sub-coating to the third sub-coating is respectively between 0.3 μm and 1.5 μm, and the hardness can gradually increase from the first sub-coating to the third sub-coating.

[0025] The first sub-coating can have a hardness of 2000 Hv or higher, the second sub-coating can have a hardness of 2500 Hv or higher, and the third sub-coating can have a hardness of 3000 Hv or higher.

[0026] The coefficient of friction can gradually decrease from the first sub-coating to the third sub-coating.

[0027] The first sub-coating may have a coefficient of friction of 0.65 to 0.75, the second sub-coating may have a coefficient of friction of 0.55 to 0.65, and the third sub-coating may have a coefficient of friction of 0.35 to 0.45.

[0028] The first to the third sub-coatings can have a concentration of 100 ppm / cm 3 The following is the residual hydrogen density.

[0029] A method for manufacturing a roll according to another embodiment of the present invention includes: a step of forming surface irregularities on the surface of a roll substrate; a step of forming a chromium-containing plating layer on the roll substrate using a plating solution containing chromium-containing raw materials and sulfuric acid; and a step of coating a metal nitride layer on the chromium-containing plating layer. In the step of forming the chromium-containing plating layer, the plating solution further contains a sulfonic acid organic catalyst, or the plating is performed while the plating solution is heated to a temperature of 65 degrees Celsius or higher and 90 degrees Celsius or lower.

[0030] The step of forming the surface irregularities may include sandblasting or shot blasting the surface of the roller substrate.

[0031] The method for manufacturing the roll according to this embodiment may further include a step of heat-treating the roll at a temperature of 130°C to 250°C for 8 to 40 hours after forming the chromium-containing plating to remove residual hydrogen.

[0032] The method for manufacturing the roll according to this embodiment may further include a step of polishing and / or cleaning the chromium-containing plating layer between the step of forming the chromium-containing plating layer and the step of coating the metal nitride layer.

[0033] The chromium-containing raw material may include anhydrous chromic acid, and the sulfonic acid organic catalyst may include alkyl sulfonates having 1 to 5 carbon atoms.

[0034] The step of coating the metal nitride layer may include the step of plasma vacuum deposition (sputtering) of the metal nitride.

[0035] The step of coating the metal nitride layer may include: depositing titanium nitride (TiN) on the chromium-containing plating layer; depositing a titanium-aluminum composite nitride on the titanium nitride; and depositing titanium carbonitride (TiCN) on the titanium-aluminum composite nitride.

[0036] The method for manufacturing a roll according to this embodiment may further include a step of coating chromium or chromium nitride on the chromium-containing plating layer between the step of forming the chromium-containing plating layer and the step of coating the metal nitride layer.

[0037] A method for manufacturing a secondary battery according to another embodiment of the present invention includes: a step of forming an electrode active material layer on a current collector; and a step of rolling the electrode active material layer using the aforementioned rolls.

[0038] Beneficial effects

[0039] According to the embodiments, the present invention has the following advantages in the roll, the method for manufacturing the roll, and the method for manufacturing the electrode therethrough: since the chromium-containing plating layer including the maximum length of the crack formed on the surface of the roll substrate is less than 5 μm, the penetration of the plating solution is prevented, thereby minimizing foreign matter defects and hydrogen defects in the final coating film, and relatively increasing the hardness of the final coating film, thereby improving wear resistance.

[0040] Furthermore, the present invention relates to a roll, a method for manufacturing a roll, and a method for manufacturing electrodes thereof, which performs crack miniaturization or crack-free plating on the substrate of the roll to generate a coating in a manner that prevents the plating solution from penetrating into the cracks while preventing the coating surface from falling off due to rolling load, thereby improving the coating life of the roll.

[0041] Furthermore, the roll, the method for manufacturing the roll, and the method for manufacturing the electrodes thereof of this invention can deposit Ti-based nitrides on the coating to form a coating with increased hardness, which is higher than that of existing DLCs and can also ensure a friction coefficient suitable for rolling.

[0042] The effects of this utility model are not limited to those described above, and those skilled in the art to which this disclosure pertains can clearly understand the effects not mentioned from this specification and the accompanying drawings. Attached Figure Description

[0043] Figure 1 This is a diagram showing a rolling mill roll according to an embodiment of the present invention.

[0044] Figure 2 and Figure 3 It is Figure 1 The enlarged view of the surface of the center part of the roll is shown in the figure.

[0045] Figure 4 This is a magnified view of the surface of the center part of the comparative example roll.

[0046] Figures 5 to 9 This is a flowchart illustrating a method for manufacturing a roll according to another embodiment of the present invention.

[0047] Figure 10 This is a flowchart illustrating an electrode manufacturing method according to another embodiment of the present disclosure.

[0048] Figure 11 and Figure 12 This is a SEM image showing the experimental results based on Experiment Example 1. Detailed Implementation

[0049] Hereinafter, several embodiments of the present invention will be described in detail with reference to the accompanying drawings to enable those skilled in the art to readily implement the present invention. The present invention can be implemented in various different forms and is not limited to the embodiments described herein.

[0050] To clearly illustrate this utility model, parts unrelated to the description have been omitted, and throughout the specification, the same or similar constituent elements are labeled with the same reference numerals.

[0051] Furthermore, for ease of explanation, the dimensions and thicknesses of the structures shown in the accompanying drawings are arbitrarily illustrated; therefore, this invention is not necessarily limited to what is shown in the drawings. In the drawings, the thicknesses of each layer and region have been enlarged to clearly show them. Also, in the drawings, the thicknesses of some layers and regions have been exaggerated for ease of explanation.

[0052] Furthermore, throughout the specification, when a part is referred to as "including" a constituent element, it does not mean that other constituent elements are excluded, but rather that other constituent elements may be included, unless otherwise stated.

[0053] Additionally, throughout the instruction manual, when referred to as a "plane," it means viewing the target portion from above, and when referred to as a "section," it means viewing the cross-section of the target portion cut vertically from the side.

[0054] The following will describe in detail the roll, the method for manufacturing the roll, and the method for manufacturing the electrode therethrough according to this embodiment.

[0055] Figure 1 This is a diagram showing a rolling mill roll according to an embodiment of the present invention. Figure 2 and Figure 3 It is Figure 1 The enlarged view of the surface of the center part of the roll is shown in the figure.

[0056] Reference Figure 1 and Figure 2 According to an embodiment of the present invention, the roll 1000 may include a roll substrate 1100 and a chromium-containing plating layer 1200 formed on the roll substrate 1100. Here, the roll 1000 may be a main roll used in the rolling process of the electrode production process of a lithium secondary battery.

[0057] More specifically, the roller substrate 1100 may include a central portion 1110, which serves as the portion for pressing down on the electrodes, and a pair of end portions 1150 integral with the central portion 1110. However, the shape of the roller substrate 1100 is not limited to this. Figure 1 Furthermore, various shapes can be applied as long as they are used to press down on the electrodes.

[0058] The roller substrate 1100 may contain chromium steel. More specifically, the roller substrate 1100 may be made of high-chromium steel. As an example, the roller substrate 1100 may be made of 3% chromium steel. In addition, the roller substrate 1100 may have a hardness of 700 Hv or more to 800 Hv or less.

[0059] Here, hardness can be the average of values ​​measured using a Vickers hardness tester. For example, hardness can be the average of five measurements taken under a load of 300 kgf. The same explanation applies to hardness in the following sections.

[0060] The surface of the roller substrate 1100 can be modified. More specifically, the surface of the roller substrate 1100 can be modified by methods such as sandblasting or shot blasting to form surface irregularities 1100p after removing foreign matter. As an example, such as Figure 2 As shown, the roller substrate 1100 may have surface irregularities 1100p with a maximum height of 5 μm or more to 25 μm or less. Here, the surface irregularities 1100p may be formed on the surface of the roller substrate 1100 facing the chromium plating layer 1200.

[0061] Therefore, in the roll 1000 according to this embodiment, since the surface protrusions 1100p formed on the roll substrate 1100 have the maximum height within the above range, the adhesion can be effectively improved by increasing the contact area between the roll substrate 1100 and the chromium plating layer 1200, and the chromium plating layer 1200 can be effectively prevented from falling off the roll substrate 1100.

[0062] In contrast, when the surface unevenness 1100p is less than 5 μm, it is difficult to effectively improve the adhesion beyond the self-adhesion between the roller substrate 1100 and the chromium-containing plating layer 1200. Furthermore, when the surface unevenness 1100p is greater than 25 μm, it is difficult to adequately ensure the thickness of the chromium-containing plating layer 1200, and the thickness deviation of the chromium-containing plating layer 1200 becomes larger depending on the position of the surface unevenness 1100p, resulting in poor adhesion and the potential for surface cracking.

[0063] The maximum length of a crack formed on the surface of the chromium-containing plating 1200 can be less than 5 μm. As an example, the crack length can be measured by averaging 10 maximum values ​​confirmed by taking SEM images of the chromium-containing plating 1200 using an electron microscope at a magnification of 1500 (unit: μm). The same explanation can be given in the following text.

[0064] More specifically, when plating with a chromium-containing plating bath containing chromium-containing raw materials (chromium oxide) and sulfuric acid, the chromium-containing plating layer 1200 can be a crack-refining or crack-free plating layer. As an example, the crack-refining or crack-free chromium-containing plating layer 1200 can be formed by further adding a sulfonic acid-based organic catalyst (alkyl sulfonate, etc.) to the chromium-containing plating bath or by performing the plating treatment at a temperature of 65°C to 90°C (more preferably 70°C to 80°C). Such crack-refining or crack-free plating can form cracks with a length of 5 μm.

[0065] Therefore, in the roll 1000 according to this embodiment, since the maximum length of the crack formed on the surface of the chromium-plated layer 1200 is less than 5 μm, the maximum length of the crack formed on the surface of the chromium-plated layer 1200 is very short compared to the case where the maximum length of the crack in a typical plating layer is 12 to 15 μm. That is, by doing so, the roll 1000 according to this embodiment can prevent the connection between cracks and can minimize defects induced by cracks. In other words, this can significantly reduce the wear of the roll 1000, thereby reducing production costs and electrode defect rate.

[0066] In contrast, in conventional coatings performed on existing rolls, the maximum crack length is 12-15 μm. Long cracks generated in conventional coatings can connect with each other in a three-dimensional manner, and there is a problem that part of the coating surface detaches due to roll load, and subsequent additional coatings are also peeled off.

[0067] In addition, the thickness of the chromium-containing plating 1200 can be more than 100 μm and less than 150 μm, and the hardness of the chromium-containing plating 1200 can be more than 1000 Hv and less than 1300 Hv.

[0068] Therefore, in the roll 1000 according to this embodiment, the hardness gradually increases in the order of substrate 1100 and chromium-containing plating 1200, thereby effectively preventing a decrease in adhesion due to abrupt changes in hardness. Furthermore, the substrate 1100 and the chromium-containing plating 1200 may include the same components to impart continuity of composition, thereby effectively preventing a decrease in adhesion due to abrupt changes in composition.

[0069] Furthermore, the residual hydrogen density of the chromium-containing plating 1200 after heat treatment can be 0.1 ppm / cm³. 3 Up to 0.25ppm / cm 3 The residual hydrogen density before and after heat treatment can be measured using thermal desorption spectroscopy (TDS). For example, the residual hydrogen density can be measured using thermal desorption-gas chromatography-mass spectrometry (TD-GC / MS), which involves heating the corresponding samples before and after heat treatment to 80 degrees Celsius, measuring the amount of hydrogen gas removed from the sample surface, and dividing the result by the sample volume.

[0070] More specifically, after forming a chromium-containing plating layer 1200 by performing crack minimization or crack-free plating on the surface of the roller substrate 1100, it can be heat-treated at a temperature of 130°C to 250°C for 8 to 40 hours. After heat treatment, residual hydrogen contained in the chromium-containing plating layer 1200 is removed, and the residual hydrogen density contained in the chromium-containing plating layer 1200 can be within the above-mentioned range.

[0071] Therefore, in the roll 1000 according to this embodiment, since the chromium plating layer 1200 has the aforementioned residual hydrogen density after heat treatment, it is possible to prevent residual hydrogen from penetrating into the roll substrate 1100 and causing hydrogen embrittlement, and it is also possible to prevent hydrogen molecule formation in the coating 1300 ( Figure 3 Bubbling defects induced by )

[0072] like Figure 3 As shown, the roll 1000 according to this embodiment may further include a coating 1300 formed on the chromium-containing plating layer 1200. Here, the coating 1300 may include a metal nitride. As an example, the coating 1300 may include a chromium nitride layer 1310 formed on the chromium-containing plating layer 1200 and a titanium nitride layer 1320 formed on the chromium nitride layer 1310. In addition, the coating 1300 may also include a chromium coating 1330 located between the chromium-containing plating layer 1200 and the chromium nitride layer 1310.

[0073] The coating 1300 will now be described in more detail, and the same applies to this embodiment.

[0074] Reference Figure 1 and Figure 3According to another embodiment of the present invention, the roll 1000 includes: a roll substrate 1100; a chromium-containing plating layer 1200 formed on the roll substrate 1100; and a first coating 1320 formed on the chromium-containing plating layer 1200 and including titanium nitride.

[0075] Here, in Figure 2 As mentioned above, the chromium plating 1200 can be a crack-refining or crack-free plating, or it can be a plating based on existing general crack plating.

[0076] Additionally, the roll 1000 according to this embodiment may also include one or more second coatings 1310, 1330 formed between the chromium-containing plating layer 1200 and the first coating layer 1320 and containing chromium or its nitride. More specifically, the second coatings 1310, 1330 may refer to the chromium coating layer 1330 and the chromium nitride layer 1310.

[0077] Here, the first coating 1320 and the second coatings 1310 and 1330 can be deposited by plasma method.

[0078] For example, such as Figure 3 As shown, in the roll 1000 according to this embodiment, the chromium coating 1330 may be located between the chromium plating layer 1200 and the chromium nitride layer 1310, and the chromium nitride layer 1310 may be located between the chromium coating 1330 and the first coating 1320.

[0079] The first coating 1320 may include: a first sub-coating 1321 formed on the chromium nitride layer 1310 or the second coatings 1310, 1330 and including titanium nitride (TiN); a second sub-coating 1322 formed on the first sub-coating 1321 and including titanium-aluminum composite nitride; and a third sub-coating 1323 formed on the second sub-coating 1322 and including titanium carbonitride (TiCN).

[0080] More specifically, the thicknesses of the first to third sub-coatings 1321, 1322, and 1323 can each be between 0.3 μm and 1.5 μm, and the hardness can gradually increase from the first sub-coating 1321 to the third sub-coating 1323. For example, the first sub-coating 1321 can have a hardness of 2000 Hv or higher, the second sub-coating 1322 can have a hardness of 2500 Hv or higher, and the third sub-coating 1323 can have a hardness of 3000 Hv or higher.

[0081] Therefore, the roll 1000 according to this embodiment has the following advantages: since the first coating 1320 can have a gradually increasing hardness, it can effectively prevent a decrease in adhesion due to a sharp change in hardness, and since the hardness of the final coating is 3000 Hv or higher, it can effectively improve wear resistance. Furthermore, the hardness change is small after the outermost Ti nitride coating is peeled off, thereby preventing rapid wear of the roll 1000.

[0082] In addition, the thickness of the second coating 1310 and 1330 can be 0.2 μm or more to 1 μm or less, and the hardness of the second coating 1310 and 1330 can be 1000 Hv or more to 2000 Hv or less.

[0083] Therefore, in the roll 1000 according to this embodiment, the hardness gradually increases in the order of chromium plating 1200, second coating 1310, 1330 and first coating 1320, thereby effectively preventing the decrease in adhesion due to abrupt changes in hardness.

[0084] Meanwhile, the second coatings 1310 and 1330 contain the same components as the chromium-containing plating 1200, thereby providing continuity of components and effectively preventing poor adhesion due to abrupt changes in components. Similarly, the first coatings 1320 are all titanium nitride layers, thus also providing continuity of components and effectively preventing poor adhesion due to abrupt changes in components.

[0085] The first sub-coating 1321 to the third sub-coating 1323 can have a gradually decreasing coefficient of friction. Here, the coefficient of friction can be an average value measured using a tribometer. As an example, the coefficient of friction can be an average value measured using a tribometer under a load of 5 N and a speed of 200 rpm. The coefficient of friction can be described similarly in the following sections.

[0086] As an example, the first sub-coating 1321 may have a coefficient of friction of 0.65 to 0.75, the second sub-coating 1322 may have a coefficient of friction of 0.55 to 0.65, and the third sub-coating 1323 may have a coefficient of friction of 0.35 to 0.45.

[0087] Therefore, in the roll 1000 according to this embodiment, since the coefficient of friction of the first coating 1320 is 0.3 or higher, the adhesion between the coatings 1300 can be sufficiently ensured, and the coefficient of friction of the final coating can be ensured to be at a level suitable for rolling, thereby effectively preventing the phenomenon of electrode slippage between the rolls 1000.

[0088] The first to third sub-coatings 1321, 1322, and 1323 can have a concentration of 100 ppm / cm³. 3 The following is the residual hydrogen density.

[0089] Therefore, in the roll 1000 according to this embodiment, since the first sub-coating to the third sub-coating 1321, 1322, 1323 have the above-mentioned residual hydrogen density, it is possible to prevent residual hydrogen from penetrating into the roll substrate 1100 to cause hydrogen embrittlement, and it is also possible to prevent hydrogen molecularization to induce blistering defects in the coating 1300.

[0090] Figure 4 This is a magnified view of the surface of the center part of the comparative example roll.

[0091] Reference Figure 4 The roll according to the comparative example includes: a roll substrate 1100'; a general hard chrome plating 1200' formed on the roll substrate 1100'; a chromium nitride layer 1300' formed on the general hard chrome plating 1200'; and a DLC (diamond-like coating) coating 1400'.

[0092] Here, the roller substrate 1100' can be made of high-chromium steel with a hardness of 700 Hv or more to 800 Hv or less. Additionally, the general hard chrome plating 1200' can have a thickness of 100 μm or more to 150 μm or less and a hardness of 800 Hv or more to 1000 Hv or less. Furthermore, the chromium nitride layer 1300' can have a thickness of 0.1 μm or more to 1.0 μm or less and a hardness of 1500 Hv or more to 1900 Hv or less. Additionally, the DLC coating 1400' can have a thickness of 1 μm or more to 2 μm or less, a hardness of 2000 Hv, and a coefficient of friction of 0.05 or more to 0.2 or less.

[0093] At this point, as mentioned above, since the maximum length of the crack in a typical hard chrome plating 1200' is 12~15μm, such long cracks can be connected to each other in a three-dimensional manner, and there is a problem that due to the roll load, a part of the plating surface detaches, and subsequent additional coatings are also peeled off.

[0094] Furthermore, the DLC coating 1400' is typically formed using ion beam deposition with hydrocarbon-based plasma gas. The resulting hydrogen atoms are molecularized and aggregate, forming blister-type defects, which contribute to coating peeling. Additionally, as mentioned above, the hardness of the DLC coating 1400' is limited to 2,000 Hv, which may be insufficient to ensure the roll's wear resistance. Moreover, the DLC coating 1400' has an excessively low coefficient of friction (0.05~0.2), resulting in insufficient adhesion to the roll substrate 1100'. Therefore, a buffer layer such as the chromium nitride layer 1300' is necessary between the DLC coating 1400' and the roll substrate 1100'.

[0095] Unlike this, such as Figures 1 to 3 As shown, in the roll 1000 according to this embodiment, since the maximum length of the crack formed on the surface of the chromium plating layer 1200 is less than 5 μm, the defects induced by the crack can be minimized, and the wear of the roll 1000 can be significantly reduced, thereby reducing production costs and reducing electrode defect rate.

[0096] Furthermore, according to this embodiment, the roll 1000 is deposited by plasma method with a first coating 1320 comprising titanium-based nitrides (TiN, TiCN, and TiAlCN) having low residual hydrogen density, high hardness, and relatively high coefficient of friction, thereby reducing friction with electrodes containing active materials that cause wear, and thus effectively extending the life of the roll.

[0097] In the following, a method for manufacturing a roll according to another embodiment of the present invention will be described.

[0098] Figures 5 to 9 This is a flowchart illustrating a method for manufacturing a roll according to another embodiment of the present invention.

[0099] Reference Figure 3 and Figure 5 A method for manufacturing a roll according to another embodiment of the present invention includes: step S100 of forming surface irregularities 1100p on the surface of a roll substrate 1100; step S200 of forming a chromium-containing plating layer 1200 on the roll substrate 1100 using a plating solution containing chromium-containing raw materials and sulfuric acid; and step S200 of coating a metal nitride layer 1320 on the chromium-containing plating layer 1200.

[0100] Reference Figure 3 and Figure 6 The step S100 of forming the surface unevenness may include a step S110 of sandblasting or shot blasting the surface of the roller substrate 1100. In addition, after step S110, a step S120 of cleaning the surface of the roller substrate 1100 may be performed.

[0101] In step S200, which forms a chromium-containing coating, the chromium-containing raw material may include anhydrous chromic acid.

[0102] Furthermore, in step S200, which forms a chromium-containing plating layer, a sulfonic acid-based organic catalyst is further added to the chromium-containing plating bath, or crack minimization or crack-free plating can be performed by heating the chromium-containing plating bath at a temperature of 65°C to 90°C (more preferably 70°C to 80°C). In this case, the sulfonic acid-based organic catalyst may comprise an alkyl sulfonate having 1 to 5 carbon atoms.

[0103] Reference Figure 3 , Figure 5 and Figure 7 The method for manufacturing the roll according to this embodiment may further include a step S400, after forming a chromium-containing plating layer S200, heat-treating at a temperature of 130°C to 250°C for 8 to 40 hours to remove residual hydrogen. More specifically, step S400 may be performed between steps S200 and S300. In this case, the heating temperature for removing hydrogen is 140°C to 200°C, and the holding time is 10 to 30 hours. Then, cooling is performed by furnace cooling until the temperature drops below 50°C.

[0104] Additionally, between step S200 (forming the chromium-containing plating layer) and step S300 (coating the metal nitride layer), steps S500 and S600 may be included to polish and / or clean the chromium-containing plating layer 1200. More specifically, steps S500 and S600 may be performed additionally after step S400. In this case, in step S500, after the heat treatment step S400 for hydrogen removal, surface polishing can be used to ensure roughness, thereby adjusting the coefficient of friction to not exceed 0.7. Furthermore, after S500, step S600 may clean the surface of the roll 1000 using ultrasonic or plasma methods, and after the surface is clean, step S300 (coating the metal nitride layer) can be performed.

[0105] Step S300, which involves coating a metal nitride layer, may include a step of plasma vacuum deposition (sputtering) of the metal nitride. More specifically, see [link to documentation]. Figure 3 and Figure 8 The step S300 of coating a metal nitride layer may include: step S310 of depositing titanium nitride (TiN) on a chromium-containing plating layer 1200; step S320 of depositing a titanium-aluminum composite nitride on titanium nitride; and step S330 of depositing titanium carbonitride (TiCN) on the titanium-aluminum composite nitride.

[0106] Reference Figure 3 and Figure 9 The method for manufacturing the roll according to this embodiment may further include steps S340 and S350, between step S200 (forming a chromium-containing plating layer) and step S300 (coating a metal nitride layer), of coating chromium or chromium nitride onto the chromium-containing plating layer. More specifically, as... Figure 9 As shown, after step S200 of forming a chromium-containing plating layer, step S340 of depositing chromium on the chromium-containing plating layer 1200 and step S350 of depositing chromium nitride on the chromium coating can be additionally performed.

[0107] Therefore, the roll manufacturing method according to this embodiment has the following advantages: In step S200, the chromium-containing coating is formed by crack minimization or crack-free coating, thereby preventing the penetration of the plating solution due to cracks, fundamentally blocking foreign matter defects flowing out from cracks during the heat treatment process, and improving the yield of the plasma coating process. Furthermore, by using crack minimization or crack-free coating, the chromium-containing coating increases its hardness to 1,000~1,300 Hv, thus preventing rapid wear even after the outermost Ti nitride coating is peeled off.

[0108] Furthermore, in the method for manufacturing the roll according to an embodiment of the present invention, in step S300 of coating the metal nitride layer, by depositing Ti-based nitride, the coefficient of friction is reduced to 0.4 to 0.7, and the hardness gradually increases to a maximum of 3,500 Hv. This reduces roll wear and fundamentally prevents coating peeling caused by blistering defects due to hydrogen generation, thereby significantly extending the life of the roll 1000. In other words, the method for manufacturing the roll according to this embodiment can reduce production costs by extending the replacement cycle of the roll 1000 and improve the rolling productivity of stable electrode active materials.

[0109] Figure 10 This is a flowchart illustrating an electrode manufacturing method according to another embodiment of the present disclosure.

[0110] Reference Figure 10 A method for manufacturing a secondary battery according to another embodiment of the present invention includes: step S700 of forming an electrode active material layer on a current collector; and step S800 of rolling the electrode active material layer using a roll 1000.

[0111] Therefore, in the secondary battery manufacturing method according to this embodiment, since the secondary battery can be manufactured by rolling the electrode active material layer using a roll 1000 with a relatively long life, it has the advantage of increasing productivity while reducing the production cost of the secondary battery.

[0112] The present invention will be described below through more specific embodiments, but the following embodiments are used to illustrate the present invention by way of example, and the scope of the present invention is not limited thereto.

[0113] <Example 1>

[0114] First, a high-strength steel substrate made of SKD11 material with dimensions of 40mmL x 20mmW x 10mmH was used. The surface of this roller substrate was sandblasted using alumina (Al2O3) with an average particle size of approximately 90μm as an abrasive to achieve an average surface roughness (Ra) of approximately 3μm. Pure water at 20°C to 25°C (room temperature) was then sprayed onto the sandblasted roller substrate surface, completely covering the surface and repeated three times for 15 minutes each time, to clean the surface.

[0115] Simultaneously, an aqueous solution containing 200 g / L anhydrous chromic acid, 25 g / L sulfuric acid, and 10 g / L ethyl sulfonate catalyst was prepared and used as the plating bath. The temperature of the plating bath was maintained at 50 degrees Celsius.

[0116] The roller substrate is immersed in the above plating solution and electroplated at 50 degrees Celsius to form a chromium-containing plating layer with a thickness of 100~200μm on the surface of the roller substrate.

[0117] <Example 2>

[0118] In the same manner as in Example 1, after forming a chromium-containing plating on the roller substrate, heat treatment was performed at a temperature of 130°C to 250°C for a period of 8 to 40 hours to remove residual hydrogen.

[0119] <Example 3>

[0120] After forming a chromium-containing coating on the roller substrate in the same manner as in Example 1, a chromium nitride (CrN) coating with a thickness of 0.3~0.5 μm, a titanium nitride (TiN) coating with a thickness of 0.5~1.0 μm, a titanium-aluminum composite nitride (TiAlN) coating with a thickness of 0.5~1.0 μm, and a titanium carbonitride (TiCN) coating with a thickness of 0.5~1.0 μm are sequentially deposited on the chromium-containing coating by plasma vacuum (sputtering).

[0121] At this point, sputtering is performed in a vacuum under conditions where a heater generates heat at a temperature of 80 degrees Celsius to 200 degrees Celsius is present.

[0122] <Comparative Example 1>

[0123] First, a high-strength steel substrate made of SKD11 material with dimensions of 40mmL x 20mmW x 10mmH is used.

[0124] Simultaneously, an aqueous solution containing 200 g / L anhydrous chromic acid and 25 g / L sulfuric acid was prepared and used as the plating solution. The temperature of the plating solution was maintained at 50 degrees Celsius.

[0125] The roller substrate is immersed in the above plating solution and electroplated at 50 degrees Celsius to form a chromium-containing plating layer with a thickness of 100~200μm on the surface of the roller substrate.

[0126] <Comparative Example 2>

[0127] In the same manner as Comparative Example 1, after forming a chromium-containing plating on the roller substrate, heat treatment was performed at a temperature of 130 degrees Celsius to 250 degrees Celsius for a period of 8 to 40 hours to remove residual hydrogen.

[0128] <Comparative Example 3>

[0129] After depositing a buffer layer (CrN) with a thickness of 0.1 to 1.0 μm on the chromium-containing plating of Comparative Example 1, DLC coating with a thickness of 1.5 to 2.5 μm was performed. Here, DLC coating can be performed using hydrocarbon-based (CnHn) plasma gas.

[0130] <Experimental Example 1: SEM Image Acquisition and Crack Size Confirmation>

[0131] SEM images of the chromium-containing coatings of Example 1 and Comparative Example 1 were captured using an electron microscope. Figure 11 This is the SEM image of Example 1. Figure 12 This is the SEM image of Comparative Example 1.

[0132] Specifically, the cross-sections of the samples prepared in Example 1 and Comparative Example 1 were magnified to SEM 1500x (unit: μm), and the average of the 10 confirmed maximum (Max) values ​​was calculated as the representative value.

[0133] Reference Figure 11 and Figure 12 It can be confirmed that in the case of Example 1, most of the cracks were less than 5 μm in length, while in the case of Comparative Example 1, cracks with a length of more than 10 μm were generated.

[0134] Therefore, unlike Comparative Example 1, when the alkyl sulfonate catalyst is used with the plating solution as in Example 1, it can be confirmed that the crack length is effectively reduced. That is, compared with Comparative Example 1, the situation in Example 1 can effectively prevent defects induced by cracks.

[0135] <Experimental Example 2: Measurement of Hydrogen Content, Residual Hydrogen Mass Ratio, and Hardness of Chromium-Containing Plating>

[0136] The residual hydrogen density and hardness of the chromium-containing platings of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were measured respectively, and the results are shown in Table 1.

[0137] Hydrogen content was measured using thermal desorption-gas chromatography-mass spectrometry (TD-GC / MS). The samples from Examples 1, 2, Comparative Example 1, and 2 were heated to 80 degrees Celsius, and the amount of hydrogen detached from the sample surface was measured. The residual hydrogen mass ratio was calculated by dividing the previously measured hydrogen content by the sample weight.

[0138] Hardness was measured using a Vickers hardness tester, and the average of five measurements was taken under a 300 kgf load.

[0139] [Table 1]

[0140] Referring to the results of hydrogen content and residual hydrogen mass ratio in Table 1, when comparing Example 1 and Comparative Example 1, it can be confirmed that, compared with Comparative Example 1, a relatively large amount of hydrogen detached from the surface of the chromium-containing plating in Example 1. Furthermore, when comparing Example 2 and Comparative Example 2, it can be confirmed that, compared with Comparative Example 2, a relatively large amount of hydrogen detached from the surface of the chromium-containing plating in Example 2.

[0141] Thus, it can be confirmed that in the chromium-containing coatings manufactured as in Examples 1 and 2, the amount of hydrogen detached or removed from the surface of the chromium-containing coating is relatively greater than that in the chromium-containing coatings manufactured as in Comparative Examples 1 and 2.

[0142] When Example 2 is compared with Example 1, it can be confirmed that, compared with Example 1, a relatively small amount of hydrogen detaches from the surface of the chromium-containing plating. Furthermore, when Comparative Example 2 is compared with Comparative Example 1, it can be confirmed that, compared with Comparative Example 1, a relatively small amount of hydrogen detaches from the surface of the chromium-containing plating.

[0143] Thus, it can be confirmed that, through the heat treatment process shown in Example 2 and Comparative Example 2, the hydrogen contained in the chromium-containing plating has been partially removed, thereby reducing the amount of hydrogen detached or removed from the surface of the chromium-containing plating compared to Example 1 and Comparative Example 1.

[0144] Referring to the hardness results in Table 1, when comparing Example 1 with Comparative Example 1, it can be confirmed that the hardness of the chromium-containing layer in Example 1 is relatively greater than that in Comparative Example 1. Furthermore, when comparing Example 2 with Comparative Example 2, it can be confirmed that the hardness of the chromium-containing layer in Example 2 is relatively greater than that in Comparative Example 2.

[0145] Thus, it can be confirmed that the chromium-containing plating produced as in Comparative Examples 1 and 2 has a greater hardness than that produced in Comparative Examples 1 and 2. When referring to the experimental results of Experimental Example 1, compared with Comparative Example 1, Example 1 formed cracks of shorter length, thereby minimizing plating defects. Therefore, it can be confirmed that the hardness of the chromium-containing plating of Example 1 is greater than that of Comparative Example 1. The same explanation can be given for Example 2.

[0146] When Example 2 is compared with Example 1, it can be confirmed that the chromium-containing plating of Example 2 has a greater hardness than that of Example 1. Furthermore, when Comparative Example 2 is compared with Comparative Example 1, it can be confirmed that the chromium-containing plating of Comparative Example 2 has a greater hardness than that of Comparative Example 1.

[0147] Thus, through the heat treatment process as in Example 2 and Comparative Example 2, the hydrogen contained in the chromium-containing coating has been partially removed, thereby minimizing coating defects. It can be confirmed that the chromium-containing coatings of Example 2 and Comparative Example 2 have greater hardness than those of Example 1 and Comparative Example 1.

[0148] <Experimental Example 3: Measurement of Residual Hydrogen Density, Hardness, Friction Coefficient, and Adhesion Force of Coatings>

[0149] The residual hydrogen density, hardness, coefficient of friction, and adhesion of the coatings of Example 3 and Comparative Example 3 were measured, and the results are shown in Table 2.

[0150] The residual hydrogen density was measured by thermal desorption-gas chromatography-mass spectrometry (TD-GC / MS), and could be obtained by dividing the result of measuring the amount of hydrogen removed from the sample surface by heating the samples of Example 3 and Comparative Example 3 to 80 degrees Celsius by the volume of the sample.

[0151] The Vickers hardness tester was used to measure the hardness using the average of five measurements under a load of 300 kgf.

[0152] The coefficient of friction was measured using a tribometer under a load of 5 N and a speed of 200 rpm.

[0153] Adhesion force was measured by a scratch test, in which the force at which peeling occurs was measured while pressure was increased. In Comparative Example 3, the measurement was performed under a load of 0.5 to 30 N and a speed of 0.55 mm / sec, and in Example 3, the measurement was performed under a load of 1 to 60 N and a speed of 0.55 mm / sec.

[0154] [Table 2]

[0155] Referring to Table 2, it can be confirmed that the residual hydrogen density of the DLC coating in Comparative Example 3 is 690 ppm / cm³. 3 Conversely, in Example 3, the residual hydrogen density was 0 in all coatings. When the hydrogen density was 500 ppm / cm³... 3 In the above cases, bubbling defects occur due to residual hydrogen. Therefore, such bubbling defects occur in Comparative Example 3, while in contrast, bubbling defects can be effectively prevented in Example 3.

[0156] In addition, it can be confirmed that the hardness of the DLC coating of Comparative Example 3 is 2,000 Hv, while in contrast, the hardness of the coating of Example 2 gradually increases in the order of chromium nitride (CrN) coating, titanium nitride (TiN) coating, titanium-aluminum composite nitride (TiAlN) coating, and titanium carbonitride (TiCN) coating.

[0157] Furthermore, it can be confirmed that the coefficient of friction of Comparative Example 3 is 0.05, while in contrast, the coating of Example 3 has a coefficient of friction of 0.4 to 0.7. Generally, when the coefficient of friction is below 0.1, electrode slippage occurs between the rolls during rolling. This slippage occurs in Comparative Example 3, while in contrast, slippage can be effectively prevented in Example 2.

[0158] Furthermore, it can be confirmed that the adhesion force of Comparative Example 3 is 17.8 N, while the adhesion force of Example 3 is 30 N. That is, in the case of Example 3, due to the high adhesion force, the coatings hardly peel off, while in the case of Comparative Example 3, due to the lower adhesion force than in Example 3, coating peeling is more likely to occur.

[0159] The preferred embodiments of the present utility model have been described in detail above, but the scope of the present utility model is not limited thereto. Various modifications and improvements made by those skilled in the art using the basic concepts of the present utility model as defined in the claims also fall within the scope of the present utility model.

[0160] Explanation of reference numerals in the attached figures

[0161] 1000: Rolls

[0162] 1100: Roller substrate

[0163] 1200: Chromium plating

[0164] 1300: Coating

Claims

1. A rolling mill roll, comprising: Roller substrate; as well as A chromium-containing plating is formed on the roller substrate, and the maximum length of the cracks formed on the surface is less than 5 μm.

2. The roll according to claim 1, wherein, The roller substrate has surface irregularities with a maximum height of 5 μm to 25 μm.

3. The roll according to claim 1, wherein, The roller substrate contains chromium steel.

4. The roll according to claim 1, wherein, The thickness of the chromium-containing plating layer is between 100 μm and 150 μm. The hardness of the chromium-containing plating is above 1000 Hv and below 1300 Hv.

5. The roll according to claim 1, wherein, The residual hydrogen density of the chromium-containing plating is 0.1 ppm / cm³. 3 Up to 0.25 ppm / cm 3 the following.

6. The roll according to claim 1, wherein, The roll also includes a coating formed on the chromium-containing plating. The coating contains a metal nitride.

7. The roll according to claim 6, wherein, The coating comprises a chromium nitride layer formed on the chromium-containing plating and a titanium nitride layer formed on the chromium nitride layer.

8. The roll according to claim 7, wherein, The coating also includes a chromium coating located between the chromium-containing plating layer and the chromium nitride layer.

9. A rolling mill roll, comprising: Roller substrate; A chromium-containing plating layer is formed on the roller substrate; The chromium-containing plating layer includes a first coating containing titanium nitride.

10. The roll according to claim 9, wherein, It also includes one or more second coatings formed between the chromium-containing plating and the first coating and containing chromium or its nitrides.

11. The roll according to claim 10, wherein, The thickness of the second coating is 0.2 μm or more but less than 1 μm. The second coating has a hardness of 1000 Hv or more to 2000 Hv or less.

12. The roll according to claim 10, wherein, The first coating includes: A first sub-coating is formed on the chromium-containing plating or the second coating and contains titanium nitride (TiN). A second sub-coating, formed on the first sub-coating and comprising a titanium-aluminum composite nitride; and A third sub-coating is formed on the second sub-coating and contains titanium carbonitride (TiCN).

13. The roll according to claim 12, wherein, The thicknesses of the first sub-coating to the third sub-coating are respectively between 0.3 μm and 1.5 μm. The hardness gradually increases from the first sub-coating to the third sub-coating.

14. The roll according to claim 13, wherein, The first sub-coating has a hardness of over 2000 Hv. The second sub-coating has a hardness of over 2500 Hv. The third sub-coating has a hardness of over 3000 Hv.

15. The roll according to claim 12, wherein, The coefficient of friction gradually decreases from the first sub-coating to the third sub-coating.

16. The roll according to claim 15, wherein, The first sub-coating has a coefficient of friction of 0.65 to 0.

75. The second sub-coating has a coefficient of friction of 0.55 to 0.

65. The third sub-coating has a coefficient of friction of 0.35 to 0.

45.

17. The roll according to claim 12, wherein, The first sub-coating to the third sub-coating has a concentration of 100 ppm / cm. 3 The following is the residual hydrogen density.

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