Grinding method of gradient nano roller

Abstract

The present application belongs to the field of roll grinding, in particular to a grinding method of gradient nano roll, comprising the following steps: a) placing the gradient nano roll to be ground in an electrolytic cell, the composition of the electrolyte used including acid, corrosion inhibitor and solvent; b) after the arrangement of step a) is completed, electrolytic corrosion is carried out on the surface of the gradient nano roll by power supply; in step b), the target corrosion depth of the gradient nano roll is predetermined, and the time of the electrolytic corrosion is calculated according to the formula; c) after the electrolytic corrosion is completed, the gradient nano roll after corrosion is ground; in step c), the porosity of the grinding wheel used is 15-20%; the temperature of the grinding is controlled below 200 DEG C. The method can realize efficient and low-cost grinding repair of high-hardness roll without damaging the gradient nano structure.

Description

Technical Field

[0001] This invention belongs to the field of roll grinding, and particularly relates to a grinding method for gradient nano rolls. Background Technology

[0002] Rolls, as core components of rolling mills, are widely used in steel, non-ferrous metals, automotive, and mining industries. The global market size reached tens of billions of yuan in 2024 and continues to grow. Main materials include alloy forged steel, alloy cast steel, and cast iron. Functionally, they can be categorized into work rolls, intermediate rolls, and support rolls. The main failure modes of rolls are wear, cracking, spalling, and fracture. Wear and cracking are the primary causes of roll failure. Surface quality issues, such as uneven microstructure, lack of density, elemental segregation, uneven hardness, and microcracks, can lead to notch sensitivity, causing cracks to develop under working stress and propagate further, resulting in roll failure. Research (Huang Qingxue, "Research and Application of Rolling Mill Bearing and Roll Life") shows that the failure rate of hot-rolled and cold-rolled work rolls due to normal wear is 25% and 50%, respectively, while the failure rate due to cracking is 60% and 20%, respectively. In addition, the working layer accounts for only 15% to 20% of the total hardened layer thickness, which leads to a sharp drop in the surface hardness of the roll after regrinding. A large number of rolls are scrapped prematurely due to insufficient performance before reaching the minimum roll diameter, and the rolling loss of a single roll is as high as several thousand tons.

[0003] Traditional methods for improving the wear resistance and hardness of roll materials include further alloying and increasing the depth of the surface hardened layer. These methods have certain limitations. For example, alloying suffers from a strength-plasticity inversion problem, meaning that high-strength materials lack sufficient toughness and fatigue resistance, making them prone to cracking or spalling under alternating stress. For instance, 9Cr2Mo achieves a hardness of HRC58-62 after quenching, but the crack propagation rate under alternating stress increases by 3-5 times. Furthermore, the use of multiple alloying elements makes smelting and purification difficult, violating the principles of a circular economy and creating recycling barriers. Surface hardening technology faces challenges such as the risk of quenching cracks, microstructure coarsening and performance degradation, and energy consumption and efficiency bottlenecks. For example, rapid cooling leads to differences in thermal expansion between the surface and core, significantly increasing the tendency for cracking in tensile stress concentration areas; deep hardening requires extended high-temperature holding time, and austenite grain coarsening (ASTM grade 3-4 → 1-2) reduces impact toughness by 50%; single-process induction hardening takes more than 8 hours, and energy consumption accounts for 25% of the roll production cost.

[0004] Therefore, some scholars have proposed applying material simplification to the rolling mill industry. Without introducing external elements, a gradient nanostructure (surface nanocrystals - subsurface ultrafine grains - core coarse grains) with high hardness, high wear resistance and fatigue resistance can be prepared on the surface of the rolling mill through surface mechanical grinding, rolling and pressing processes. The surface nanocrystals (hardness HRC≥65) provide ultra-high wear resistance, and the gradient structure coordinates plastic deformation through dynamic grain boundary migration, thereby increasing fatigue life by 2 to 3 times.

[0005] Because rolls are subjected to high stress and friction for extended periods, their surfaces are prone to damage and material adhesion, necessitating periodic regrinding. Typically, work rolls require regrinding after several hundred hours of rolling. While gradient nanotechnology significantly improves roll performance, the ultra-high surface hardness poses a severe challenge to subsequent grinding and repair processes. Traditional grinding methods reduce the efficiency of corundum / silicon carbide wheels by 70%, while diamond wheels are prohibitively expensive (5-10 times the price of traditional wheels), and the accumulated grinding heat (>800℃) can easily induce surface phase transformations and microcracks. Existing technologies such as laser processing and electrical discharge machining can alleviate grinding difficulties to some extent, but they also have their own limitations.

[0006] (1) Laser processing technology utilizes localized melting to remove materials. However, a large heat input can lead to a large heat-affected zone (>200 μm), disrupting the continuity of the surface gradient structure and coarsening the surface nanocrystals and subsurface ultrafine grains, thereby affecting its microstructure and mechanical properties. In addition, the investment cost of laser equipment is high, making it less cost-effective for large-scale production. Furthermore, laser processing efficiency is lower than that of grinding wheels, and it may face problems of insufficient laser power or precision in the processing of some special materials.

[0007] (2) Electrical discharge machining (EDM) is a machining method that removes metal from the surface of a workpiece through electrical discharge. Although this technology has certain advantages in machining high-hardness materials, it also has some limitations, such as low machining efficiency (<5mm). 3 / min); a relatively serious heat-affected zone is generated on the surface of the workpiece, which affects the microstructure and properties of the material; conductive materials are also required, while the application of non-conductive or difficult-to-conduct materials is greatly limited.

[0008] In summary, existing technologies cannot achieve efficient and low-cost grinding repair of high-hardness rolls without damaging the gradient nanostructure, which severely restricts the industrialization and promotion of this technology. Summary of the Invention

[0009] In view of this, the purpose of the present invention is to provide a grinding method for gradient nano-rolls, which can achieve efficient and low-cost grinding repair of high-hardness rolls without damaging the gradient nanostructure.

[0010] This invention provides a grinding method for gradient nano-rolls, comprising the following steps:

[0011] a) Place the gradient nano-roll to be ground in an electrolytic cell, connect the positive terminal of the power supply to the surface of the roll, place the cathode connected to the negative terminal of the power supply at a certain distance from the roll, and set several reference electrodes on the surface of the roll; inject the electrolyte into the electrolytic cell, and the liquid level covers the surface of the roll.

[0012] In step a), the electrolyte comprises acid, corrosion inhibitor and solvent;

[0013] b) After completing the arrangement in step a), electrolytic corrosion is performed on the surface of the gradient nanoroller by applying electricity;

[0014] In step b), the target corrosion depth of the gradient nanoroll is predetermined, and the electrolytic corrosion time is calculated according to formula (I):

[0015] Formula (I);

[0016] In equation (I): D(t) is the target corrosion depth, in μm; Anode current density, unit: A / m 2 M is the weighted average molar mass of elements in the roll, in g / mol; Z is the charge transfer number in the metal dissolution reaction; F is the Faraday constant; ρ is the roll density, in kg / m³. 3 f(GSD) is the grain size influence factor; g(κ) is the electrolyte conductivity influence factor; g(m) is the surface roughness influence factor; g(dis) is the crystal defect influence factor; g(e) is the elemental influence factor; D P The pulse duty cycle is t; the corrosion time is t, in seconds.

[0017] c) After the electrolytic corrosion is completed, the corroded gradient nano-roll is ground;

[0018] In step c), the porosity of the grinding wheel used in the grinding is 15-20%; the grinding temperature is controlled below 200°C.

[0019] Preferably, in formula (I) Calculate according to formula (II):

[0020] Formula (II);

[0021] In equation (II), i0 is the exchange current density, in A / m. 2 η is the overpotential, in V; α a α is the anode transfer coefficient; c R is the cathode transfer coefficient; R is the gas constant.

[0022] Preferably, f(GSD) in equation (I) is calculated according to equation (III):

[0023] Formula (III);

[0024] In equation (III), k0 is the grain size factor, which is 0.15 mm. 1 / 2 .

[0025] Preferably, g(κ) in formula (I) is calculated according to formula (IV):

[0026] Formula (IV);

[0027] In equation (IV), k is the electrolyte conductivity, in S / m; Ac is the corrosion contact area, in m². 2 L represents the electrode spacing in meters (m); V represents the applied voltage in volts (V).

[0028] Preferably, g(m) in formula (I) is calculated according to formula (V):

[0029] Formula (V);

[0030] In equation (V), B is the roughness coefficient, with units of μm. -m ;R a is the roughness, in μm; m is the roughness index, with a value of 1.2.

[0031] Preferably, g(dis) in formula (I) is calculated according to formula (VI):

[0032] Formula (VI);

[0033] In equation (VI), C is the dislocation coefficient, which takes the value of 3.0 × 10⁻⁶. -15 m 2 ;ρ dis Dislocation density, in units of m -2 .

[0034] Preferably, g(e) in formula (I) is calculated according to formula (VII):

[0035] Equation (VII);

[0036] In equation (VII), g C (e) represents the influence factor of element C; g Cr (e) represents the influence factor of Cr element;

[0037] g in equation (VII) C (e) Calculate according to formula (VIII):

[0038] Equation (VII);

[0039] In equation (VII), [C] solid The value represents the dissolved carbon content, expressed in wt%; [C] carbide The carbon content in the carbides is expressed in wt%; [Cr] carbide Chromium content in carbides, in wt%

[0040] g in equation (VII) Cr (e) Calculate according to formula (IX):

[0041] Formula (IX);

[0042] In formula (IX), [Cr] solid The values ​​represent the dissolved chromium content, in wt%; [Cr] carbide The chromium content in the carbide is expressed in wt%.

[0043] Preferably, in step a), the gradient nano-roll to be ground is pretreated before being placed in the electrolytic cell. The specific pretreatment process includes:

[0044] The gradient nano roll to be ground is surface cleaned, and then a protective layer is set on the surface of the non-grinding area of ​​the roll, followed by immersion in acid solution for a period of time.

[0045] Preferably, in step a), H + The concentration of the acid in the electrolyte is calculated to be 0.02~0.4 mol / L.

[0046] Preferably, in step a), the electrolyte further comprises a stabilizer; the stabilizer is thiourea and polyethylene glycol; the concentration of thiourea in the electrolyte is 0~0.2wt%; and the concentration of polyethylene glycol in the electrolyte is 0~0.1wt%.

[0047] Preferably, in step b), the electrolyte temperature for electrolytic corrosion is 10~40℃; and the current density for electrolytic corrosion is 100~500A / m. 2 .

[0048] Preferably, in step c), the grinding temperature is controlled by a combination of air cooling and emulsion cooling.

[0049] Compared with the prior art, the present invention provides a grinding method for a gradient nano-roll, comprising the following steps: a) placing the gradient nano-roll to be ground in an electrolytic cell, connecting the positive electrode of a power supply to the surface of the roll, placing a cathode connected to the negative electrode of the power supply at a certain distance from the roll, and setting several reference electrodes on the surface of the roll; injecting electrolyte into the electrolytic cell, the liquid level covering the surface of the roll; in step a), the electrolyte comprises acid, corrosion inhibitor and solvent; b) after completing the arrangement in step a), electrolytic corrosion is performed on the surface of the gradient nano-roll by applying electricity; in step b), the target corrosion depth of the gradient nano-roll is predetermined, and the electrolytic corrosion time is calculated according to formula (I); in formula (I), D(t) is the target corrosion depth, in μm; Anode current density, unit: A / m 2 M is the weighted average molar mass of elements in the roll, in g / mol; Z is the charge transfer number in the metal dissolution reaction; F is the Faraday constant; ρ is the roll density, in kg / m³. 3 f(GSD) is the grain size influence factor; g(κ) is the electrolyte conductivity influence factor; g(m) is the surface roughness influence factor; g(dis) is the crystal defect influence factor; g(e) is the elemental influence factor; D P t represents the pulse duty cycle; t represents the corrosion time in seconds; c) After completing the electrolytic corrosion, the corroded gradient nanoroll is ground; in step c), the porosity of the grinding wheel used for grinding is 15-20%; the grinding temperature is controlled below 200℃. This invention first performs controllable micro-corrosion on the roll surface of the gradient nanoroll, reducing the surface hardness while preserving the integrity of the roll's gradient structure. Specifically, an acidic electrolyte is selected for electrolytic corrosion of the gradient nanoroll surface. A corrosion inhibitor is added to the electrolyte to suppress intragranular corrosion of the roll material, allowing only grain boundary dissolution and ensuring precise grain boundary dissolution. Based on this, the accurate electrolytic corrosion time is calculated using relevant formulas to create a 10-12 μm softening layer on the roll surface, preventing excessive corrosion from damaging the integrity of the roll's gradient structure. Subsequently, the softened roll surface is ground with a grinding wheel with a porosity of 15-20% to increase the chip removal rate and improve grinding efficiency; at the same time, the grinding temperature is strictly controlled to avoid thermal damage to the roll caused by local overheating. The method provided by this invention can achieve efficient and low-cost grinding repair of high-hardness rolls without damaging the gradient nanostructure, and has good market prospects. Detailed Implementation

[0050] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] This invention provides a grinding method for gradient nano-rolls, comprising the following steps:

[0052] a) Place the gradient nano-roll to be ground in an electrolytic cell, connect the positive terminal of the power supply to the surface of the roll, place the cathode connected to the negative terminal of the power supply at a certain distance from the roll, and set several reference electrodes on the surface of the roll; inject the electrolyte into the electrolytic cell, and the liquid level covers the surface of the roll.

[0053] In step a), the electrolyte comprises acid, corrosion inhibitor and solvent;

[0054] b) After completing the arrangement in step a), electrolytic corrosion is performed on the surface of the gradient nanoroller by applying electricity;

[0055] In step b), the target corrosion depth of the gradient nanoroll is predetermined, and the electrolytic corrosion time is calculated according to formula (I):

[0056] Formula (I);

[0057] In equation (I): D(t) is the target corrosion depth, in μm; Anode current density, unit: A / m 2 M is the weighted average molar mass of elements in the roll, in g / mol; Z is the charge transfer number in the metal dissolution reaction; F is the Faraday constant; ρ is the roll density, in kg / m³. 3 f(GSD) is the grain size influence factor; g(κ) is the electrolyte conductivity influence factor; g(m) is the surface roughness influence factor; g(dis) is the crystal defect influence factor; g(e) is the elemental influence factor; D P The pulse duty cycle is t; the corrosion time is t, in seconds.

[0058] c) After the electrolytic corrosion is completed, the corroded gradient nano-roll is ground;

[0059] In step c), the porosity of the grinding wheel used in the grinding is 15-20%; the grinding temperature is controlled below 200°C.

[0060] In the method provided by the present invention, in step a), the surface hardness of the gradient nanoroll to be ground is preferably HRC≥65; the grain size of the outermost layer (nanocrystalline layer) of the gradient nanoroll to be ground is preferably 20~50nm, and the layer thickness is preferably 20~70μm, more preferably 50μm; the grain size of the second outermost layer (ultrafine crystalline layer) of the gradient nanoroll to be ground is preferably 100-500nm, and the layer thickness is preferably 100~200μm, more preferably 150μm; the grain size of the core (coarse grain) of the gradient nanoroll to be ground is preferably ≥1μm.

[0061] In the method provided by this invention, in step a), the gradient nano-roll to be ground is pretreated before being placed in the electrolytic cell. The specific pretreatment process includes:

[0062] The gradient nano roll to be ground is surface cleaned, and then a protective layer is set on the surface of the non-grinding area of ​​the roll, followed by immersion in acid solution for a period of time.

[0063] In the pretreatment process provided by the present invention, the purpose of surface cleaning is to remove oil and oxide layer from the surface of the roll; the cleaning agent for surface cleaning is preferably an alkaline cleaning agent, preferably a NaOH solution, and the concentration of the NaOH solution is preferably 5~10wt%; the surface cleaning method is preferably immersion cleaning, and the immersion cleaning time is preferably 10~30min, more preferably 20min.

[0064] In the pretreatment process provided by the present invention, the non-grinding area includes, but is not limited to, the roller neck, shaft head, and soft belt area; the protective layer is preferably an epoxy coating, a modified epoxy coating, or an epoxy composite coating, wherein the modified epoxy coating is preferably a fluorinated modified epoxy resin coating, and the epoxy composite coating is preferably a polyurethane-epoxy resin composite coating; the thickness of the protective layer is preferably 100~300μm, more preferably 150~200μm.

[0065] In the method provided by the present invention, in step a), the cathode is preferably a graphite rod; the distance between the cathode and the roll is preferably 10~20cm.

[0066] In the method provided by the present invention, in step a), the reference electrode is preferably an Ag / AgCl electrode.

[0067] In the method provided by this invention, in step a), the acid in the electrolyte is preferably sulfuric acid and / or hydrochloric acid; with H + The concentration of the acid in the electrolyte is preferably 0.02~0.4 mol / L, more preferably 0.04~0.2 mol / L.

[0068] In the method provided by the present invention, in step a), the corrosion inhibitor in the electrolyte is used to inhibit intragranular corrosion; the corrosion inhibitor is preferably thiourea and / or benzotriazole; the concentration of the corrosion inhibitor in the electrolyte is preferably 0.02~0.2wt%, more preferably 0.05~0.1wt%.

[0069] In the method provided by the present invention, in step a), the electrolyte preferably further includes a stabilizer for stabilizing the diffusion layer; the stabilizer is thiourea and polyethylene glycol; the concentration of thiourea in the electrolyte is preferably 0~0.2wt%, more preferably 0.05~0.15wt%, and the concentration of polyethylene glycol in the electrolyte is preferably 0~0.1wt%, more preferably 0.02~0.08wt%.

[0070] In the method provided by the present invention, in step a), the pH value of the electrolyte is preferably 0.5 to 2, more preferably 0.75 to 1.5.

[0071] In the method provided by this invention, in step b), the formula (I) Calculate according to formula (II):

[0072] Formula (II);

[0073] In equation (II), i0 is the exchange current density, in A / m. 2 η is the overpotential, in V; α a α is the anode transfer coefficient; c is the cathode transfer coefficient; R is the gas constant, with a value of 8.314 J / (mol·K).

[0074] In the method provided by this invention, in step b), f(GSD) in equation (I) is calculated according to equation (III):

[0075] Formula (III);

[0076] In equation (III), k0 is the grain size factor, which is 0.15 mm. 1 / 2 .

[0077] In the method provided by this invention, in step b), g(κ) in formula (I) is calculated according to formula (IV):

[0078] Formula (IV);

[0079] In equation (IV), k is the electrolyte conductivity, in S / m; Ac is the corrosion contact area, in m²; L is the electrode spacing, in m; and V is the applied voltage, in V.

[0080] In the method provided by this invention, in step b), g(m) in formula (I) is calculated according to formula (V):

[0081] Formula (V);

[0082] In equation (V), B is the roughness coefficient, with units of μm. -m ;R a is the roughness, in μm; m is the roughness index, with a value of 1.2.

[0083] In the method provided by this invention, in step b), g(dis) in formula (I) is calculated according to formula (VI):

[0084] Formula (VI);

[0085] In equation (VI), C is the dislocation coefficient, which takes the value of 3.0 × 10⁻⁶. -15 m 2 ;ρ dis Dislocation density, in units of m -2 .

[0086] In the method provided by this invention, in step b), g(e) in formula (I) is calculated according to formula (VII):

[0087] Equation (VII);

[0088] In equation (VII), g C (e) represents the influence factor of element C; g Cr (e) represents the influence factor of Cr element.

[0089] In the method provided by this invention, in step b), g in formula (VII) C (e) Calculate according to formula (VIII):

[0090] Equation (VII);

[0091] In equation (VII), [C] solid The value represents the dissolved carbon content, expressed in wt%; [C] carbide The carbon content in the carbides is expressed in wt%; [Cr] carbide The chromium content in the carbide is expressed in wt%.

[0092] In the method provided by this invention, in step b), g in formula (VII) Cr (e) Calculate according to formula (IX):

[0093] Formula (IX);

[0094] In formula (IX), [Cr] solid The values ​​represent the dissolved chromium content, in wt%; [Cr] carbide The chromium content in the carbide is expressed in wt%.

[0095] In the method provided by this invention, in step b), the exchange current density of the electrolytic corrosion is preferably 100~500 A / m. 2 Specifically, it can be 100A / m 2 200A / m 2 300A / m 2 400A / m 2 500A / m 2 .

[0096] In the method provided by the present invention, in step b), the voltage of the electrolytic corrosion is preferably 2V~5V, specifically 2V, 3V, 4V, or 5V.

[0097] In the method provided by the present invention, in step b), the overpotential of the electrolytic corrosion is preferably 0.05V~0.15V, specifically 0.05V, 0.06V, 0.07V, 0.08V, 0.09V, 0.1V, 0.11V, 0.12V, 0.13V, 0.14V, or 0.15V.

[0098] In the method provided by the present invention, in step b), the conductivity of the electrolyte for electrolytic corrosion is 5S / m to 15S / m, specifically 5S / m, 6S / m, 7S / m, 8S / m, 9S / m, 10S / m, 11S / m, 12S / m, 13S / m, 14S / m, or 15S / m.

[0099] In the method provided by this invention, in step b), the roughness of the electrolytic corrosion is preferably no greater than 0.6. To ensure work efficiency, the roughness value only needs to be uniform.

[0100] In the method provided by this invention, in step b), the pulse empty ratio of the electrolytic corrosion is preferably 0.1 to 0.2 to avoid excessively rapid corrosion and to improve processing accuracy and surface quality. Specifically, the pulse empty ratio can be 0.1, 0.12, 0.14, 0.16, 0.18, or 0.2.

[0101] In the method provided by the present invention, in step c), the grinding wheel used for grinding is preferably a resin CBN grinding wheel or a ceramic bonded corundum grinding wheel.

[0102] In the method provided by the present invention, in step c), the porosity of the grinding wheel used for grinding is 15-20% to enhance the chip dissolving ability and avoid grinding blockage; the porosity of the grinding wheel can specifically be 15%, 16%, 17%, 18%, 19% or 20%.

[0103] In the method provided by the present invention, in step c), the grit size of the grinding wheel used for grinding is preferably 200~600#, specifically 200#, 210#, 220#, 230#, 240#, 250#, 260#, 280#, 300#, 350#, 400#, 450#, 500# or 600#.

[0104] In the method provided by the present invention, in step c), the linear speed of the grinding wheel is preferably 20~50m / s, specifically 20m / s, 25m / s, 30m / s, 35m / s, 40m / s, 45m / s or 50m / s.

[0105] In the method provided by the present invention, in step c), the grinding temperature is controlled below 200°C, preferably 60~150°C; the grinding temperature is preferably controlled by air cooling combined with emulsion cooling. The preferred temperature of the air-cooled air is 20-30℃, specifically 20℃, 25℃, or 30℃; the preferred air velocity is 20-40 m / s, specifically 20 m / s, 25 m / s, 30 m / s, 35 m / s, or 40 m / s; the preferred concentration of the emulsion is 3-10 wt%, specifically 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%; and the preferred flow rate of the emulsion is 10-20 L / min, specifically 10 L / min, 11 L / min, 12 L / min, 13 L / min, 14 L / min, 15 L / min, 16 L / min, 17 L / min, 18 L / min, 19 L / min, or 20 L / min.

[0106] In the method provided by the present invention, in step c), the grinding amount (the thickness of material removed from the surface of the roll during the grinding process, i.e., the amount removed in the radial direction) is preferably 0.05~0.15mm, specifically 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.1mm, 0.11mm, 0.12mm, 0.13mm, 0.14mm or 0.15mm.

[0107] In the method provided by the present invention, in step c), after the grinding is completed, the surface roughness Ra of the roll is preferably ≤0.1μm, specifically 0.01μm, 0.02μm, 0.03μm, 0.04μm, 0.05μm, 0.06μm, 0.07μm, 0.08μm, 0.09μm or 0.1μm.

[0108] In the method provided by the present invention, for gradient nanorolls that have undergone protective layer pretreatment, it is preferable to remove the protective layer after grinding.

[0109] The method provided by this invention can achieve efficient and low-cost grinding repair of high-hardness rolls without damaging the gradient nanostructure. More specifically, it has at least the following advantages:

[0110] (1) By controlling the micro-corrosion of the roll surface of the gradient nano roll, the surface is softened only in the range of 10~12μm (hardness is reduced to HRC 55~60), while preserving the integrity of the gradient nano structure (the ultrafine grains in the subsurface layer and the coarse grains in the core are not affected by heat).

[0111] (2) When the corrosion depth is consistent, the time required for corrosion is basically the same. The larger the diameter of the roll, the higher its efficiency.

[0112] (3) A pulse power supply is used, and the relationship between efficiency and surface quality is balanced according to actual production needs by adjusting the pulse idle ratio;

[0113] (4) Apply a protective layer to the non-working areas of the roll (roll neck, shaft head and soft belt) to avoid electrolyte corrosion and improve process reliability.

[0114] For clarity, the following examples will be used to provide a detailed description.

[0115] In the following embodiments of the present invention, unless otherwise specified, the relevant operations are performed at room temperature (25°C) and normal pressure (1 atm).

[0116] Example 1

[0117] A gradient nano-scale Cr3 roll (Φ435×1240mm) underwent surface micro-corrosion synergistic grinding treatment. The roll achieved a surface hardness of HRC≥65, with a grain size of 20~50nm in the outermost layer (0~50μm), 100~500nm in the second layer (50~200μm), and a coarse grain size ≥1μm in the core. The specific treatment process is as follows:

[0118] 1) Roll pretreatment:

[0119] First, the rolls are immersed in a 5wt% NaOH solution for 20 minutes to remove oil, rust, and scale from the roll surface, roll neck, shaft head, and soft belt area. Then, fluorinated modified epoxy resin is sprayed onto the roll neck, roll head, and soft belt area of ​​the rolls, with a coating thickness of 200μm and an acid resistance rating of Class A.

[0120] 2) Micro-corrosion treatment:

[0121] The roll is placed in an electrolytic cell, and its surface is connected to the positive terminal of a DC power supply via a conductive clamp. A graphite rod connected to the negative terminal of the power supply is placed 10 cm away from the roll. Multiple Ag / AgCl electrode films are attached to the surface of the roll to be etched as reference electrodes. The prepared electrolyte (0.1 mol / L H2SO4, 0.1 wt% thiourea, 0.05 wt% polyethylene glycol, pH=1) is injected into the electrolytic cell, ensuring the liquid level covers the roll surface. Electrolytic etching is then performed on the roll surface, with a target etching depth of 10~12 μm and an exchange current density of 400 A / m. 2 The electrolyte temperature for electrolytic corrosion is 25℃, and the electrolytic corrosion time is 10 minutes.

[0122] The theoretical corrosion depth is calculated according to formulas (I) to (IX). The calculation process is as follows:

[0123] Select an exchange current density of 400 A / m 2 The anode-cathode transfer coefficient is 0.5, the Faraday constant is 96485 C / mol, the gas constant is 8.314 J / (mol·K), the charge number is 2, the molar mass is 56 g / mol, the density is 7.85 g / cm³, the overpotential is 0.1 V, and the temperature is 298 K.

[0124] The anode current density is:

[0125] ;

[0126] The grain size influence factor is:

[0127] (Average grain size is 35nm);

[0128] The conductivity is:

[0129] (Electrolyte conductivity 8 S / m, electrode spacing 0.1 m, applied voltage 3 V);

[0130] The surface roughness factor is:

[0131] ;

[0132] The crystal defect factor is:

[0133] (In cold deformation, the dislocation density is approximately 2 × 10⁻⁶) 15 );

[0134] In this alloy steel, the carbon content of carbides is 0.25%, the carbon content of solid solution is 0.05%, the chromium content of carbides is 1.39%, and the chromium content of solid solution is 1.61%.

[0135] The carbon element's influence factor is:

[0136] ;

[0137] The influence factor of chromium is:

[0138] ;

[0139] The element impact factor is:

[0140] ;

[0141] To ensure the surface structure and quality during the corrosion process, a pulse void ratio of 0.16 was selected.

[0142] The theoretical calculated value is:

[0143] .

[0144] 3) Grinding process:

[0145] The gradient nano-roll, after undergoing micro-corrosion treatment, was ground. The grinding wheel used was a resin CBN wheel with 18% porosity (220# grit), and the wheel linear velocity was 30 m / s. The cooling method was a combination of air cooling and emulsion cooling. The cooling air temperature was 25℃, and the cooling air velocity was 35 m / s. The emulsion was obtained by diluting a stock emulsion with water. The stock emulsion was a water-based formula (containing 65 wt% mineral oil, 12 wt% nonionic emulsifier, 3 wt% triethanolamine, 1.5 wt% sulfurized fatty acid ester, and the balance being water, pH=8), with a diluted emulsion concentration of 8 wt%. The emulsion flow rate during cooling was 18 L / min. This cooling method controlled the grinding temperature between 80 and 150℃. The grinding depth was 0.08 mm. After grinding, the surface roughness of the roll was Ra=0.06 μm.

[0146] 4) Post-processing:

[0147] Apply German Pfinder AP760 cleaning agent evenly to the roller neck, roller head, and soft belt area at a spraying temperature of 40°C. After the cleaning agent has been left for 10 minutes, rinse with deionized water and remove the residual epoxy resin coating with a nylon scraper.

[0148] Example 2

[0149] A Cr5 roll (Φ85×1677mm) with gradient nanostructures underwent surface micro-corrosion and synergistic grinding treatment. The roll achieved a surface hardness of HRC≥65, with a grain size of 20~50nm in the outermost layer (0~50μm), 100~500nm in the second layer (50~200μm), and a coarse grain size ≥1μm in the core. The specific treatment process is as follows:

[0150] 1) Roll pretreatment:

[0151] First, the rolls are immersed in a 5wt% NaOH solution for 20 minutes to remove oil, rust, and scale from the roll surface, roll neck, shaft head, and soft belt area. Then, a polyurethane-epoxy resin composite coating with a thickness of 150μm and a wear resistance rating of Class B is sprayed onto the roll neck, roll head, and soft belt area. Finally, the roll surface is immersed in a 10wt% HNO3 solution for 5 minutes to activate the grain boundaries.

[0152] 2) Micro-corrosion treatment:

[0153] The roll is placed in an electrolytic cell, and its surface is connected to the positive terminal of a DC power supply via a conductive clamp. A graphite rod connected to the negative terminal of the power supply is placed 10 cm away from the roll. Multiple Ag / AgCl electrode films are attached to the surface of the roll to be etched as reference electrodes. The prepared electrolyte (0.1 mol / L H2SO4, 0.1 wt% thiourea, 0.05 wt% polyethylene glycol, pH=1) is injected into the electrolytic cell, ensuring the liquid level covers the roll surface. Electrolytic etching is then performed on the roll surface, with a target etching depth of 10~12 μm and an exchange current density of 400 A / m. 2 The electrolyte temperature for electrolytic corrosion is 25℃, and the electrolytic corrosion time is 10 minutes.

[0154] The theoretical corrosion depth is calculated according to formulas (I) to (VIII). The calculation process is as follows:

[0155] The approximate molar mass of a Cr5 roll is M = 56 g / mol, the number of electrons transferred is n = 2, and the density is ρ = 7.85 g / cm³. 3 The exchange current density is selected as 400 A / m. 2 The anode-cathode transfer coefficient is 0.5, the Faraday constant is 96485 C / mol, the gas constant is 8.314 J / (mol·K), the overpotential is 0.1 V, and the temperature is 298 K.

[0156] The anode current density is:

[0157] ;

[0158] The grain size influence factor is:

[0159] (Average grain size is 35nm);

[0160] The conductivity is:

[0161] (Electrolyte conductivity 8 S / m, electrode spacing 0.1 m, applied voltage 3 V);

[0162] The surface roughness factor is:

[0163] ;

[0164] The crystal defect factor is:

[0165] (In cold deformation, the dislocation density is approximately 2 × 10⁻⁶) 15 );

[0166] In this alloy steel, the carbon content of carbides is 0.9%, the carbon content of solid solution is 0.1%, the chromium content of carbides is 2%, and the chromium content of solid solution is 3%.

[0167] The carbon element's influence factor is:

[0168] ;

[0169] The influence factor of chromium is:

[0170] ;

[0171] The element impact factor is:

[0172] ;

[0173] To ensure the surface structure and quality during the corrosion process, a pulse void ratio of 0.16 was selected.

[0174] The theoretical calculated value is:

[0175] .

[0176] 3) Grinding process:

[0177] The gradient nano-roll, after undergoing micro-corrosion treatment, was ground. The grinding wheel used was a ceramic-bonded corundum wheel with a porosity of 20% (240# grit), and the wheel linear velocity was 40 m / s. The grinding cooling method was a combination of air cooling and emulsion cooling. The cooling air temperature was 25℃, and the cooling air velocity was 30 m / s. The emulsion used was obtained by diluting a stock emulsion with water. The stock emulsion was a water-based formula (containing 60 wt% synthetic ester, 10 wt% sodium petroleum sulfonate, 2 wt% diethanolamine, 1 wt% phosphate ester, and the balance being water, pH=7~8). The diluted emulsion concentration was 5 wt%, and the emulsion flow rate during cooling was 15 L / min. This cooling method controlled the grinding temperature between 60~120℃. The grinding allowance was 0.1 mm. After grinding, the surface roughness of the roll was Ra=0.05 μm.

[0178] 4) Post-processing:

[0179] Apply German Pfinder AP760 cleaning agent evenly to the roller neck, roller head, and soft belt area at a spraying temperature of 40°C. After the cleaning agent has been left for 10 minutes, rinse with deionized water and remove the residual epoxy resin coating with a nylon scraper.

[0180] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A grinding method for gradient nano-rolls, characterized in that, Includes the following steps: a) Place the gradient nano-roll to be ground in an electrolytic cell, connect the positive terminal of the power supply to the surface of the roll, place the cathode connected to the negative terminal of the power supply at a certain distance from the roll, and set several reference electrodes on the surface of the roll; inject the electrolyte into the electrolytic cell, and the liquid level covers the surface of the roll. In step a), the electrolyte comprises acid, corrosion inhibitor and solvent; b) After completing the arrangement in step a), electrolytic corrosion is performed on the surface of the gradient nanoroller by applying electricity; In step b), the target corrosion depth of the gradient nanoroll is predetermined, and the electrolytic corrosion time is calculated according to formula (I): Equation (I); In equation (I): D(t) is the target corrosion depth, in μm; Anode current density, unit: A / m 2 M is the weighted average molar mass of elements in the roll, in g / mol; Z is the charge transfer number in the metal dissolution reaction; F is the Faraday constant; ρ is the roll density, in kg / m³. 3 f(GSD) is the grain size influence factor; g(κ) is the electrolyte conductivity influence factor; g(m) is the surface roughness influence factor; g(dis) is the crystal defect influence factor; g(e) is the elemental influence factor; D P This refers to the pulse duty cycle. t represents the corrosion time, in seconds. c) After the electrolytic corrosion is completed, the corroded gradient nano-roll is ground; In step c), the porosity of the grinding wheel used in the grinding is 15-20%; the grinding temperature is controlled below 200°C.

2. The grinding method according to claim 1, characterized in that, In formula (I) Calculate according to formula (II): Formula (II); In formula (II), i0is the exchange current density, in A / m 2 ; η is the overpotential, in V; a a is the anode transfer coefficient; a c is the cathode transfer coefficient; R is the gas constant.

3. The grinding method according to claim 1, characterized in that, f(GSD) in equation (I) is calculated according to equation (III): Formula (III); In formula (III), k0 is a crystal grain size coefficient, and has a value of 0.15 mm 1 / 2 .

4. The grinding method according to claim 1, characterized in that, In equation (I), g(κ) is calculated according to formula (IV): Formula (IV); In equation (IV), k is the electrolyte conductivity, in S / m; Ac is the corrosion contact area, in m². 2 L represents the electrode spacing in meters (m); V represents the applied voltage in volts (V).

5. The grinding method according to claim 1, characterized in that, In equation (I), g(m) is calculated according to formula (V): Formula (V); In equation (V), B is the roughness coefficient, with units of μm. -m ;R a is the roughness, in μm; m is the roughness index, with a value of 1.

2.

6. The grinding method according to claim 1, characterized in that, In equation (I), g(dis) is calculated according to equation (VI): Formula (VI); In equation (VI), C is the dislocation coefficient, which takes the value of 3.0 × 10⁻⁶. -15 m 2 ; ρ dis Dislocation density, in units of m -2 .

7. The grinding method according to claim 1, characterized in that, In equation (I), g(e) is calculated according to formula (VII): Equation (VII); In equation (VII), g C (e) represents the influence factor of element C; g Cr (e) represents the influence factor of Cr element; g in equation (VII) C (e) Calculate according to formula (VIII): Equation (VII); In equation (VII), [C] solid The value represents the dissolved carbon content, expressed in wt%; [C] carbide The carbon content in the carbides is expressed in wt%; [Cr] carbide Chromium content in carbides, in wt% g in equation (VII) Cr (e) Calculate according to formula (IX): Formula (IX); In formula (IX), [Cr] solid The values ​​represent the dissolved chromium content, in wt%; [Cr] carbide The chromium content in the carbide is expressed in wt%.

8. The grinding method according to claim 1, characterized in that, In step a), the gradient nano-roll to be ground is pretreated before being placed in the electrolytic cell. The specific pretreatment process includes: The gradient nano roll to be ground is surface cleaned, and then a protective layer is set on the surface of the non-grinding area of ​​the roll, followed by immersion in acid solution for a period of time.

9. The grinding method according to claim 1, characterized in that, In step a), H + The concentration of the acid in the electrolyte is calculated to be 0.02~0.4 mol / L.

10. The grinding method according to claim 1, characterized in that, In step a), the electrolyte further comprises a stabilizer; the stabilizer is thiourea and polyethylene glycol; the concentration of thiourea in the electrolyte is 0~0.2wt%; The concentration of polyethylene glycol in the electrolyte is 0~0.1wt%.

11. The grinding method according to claim 1, characterized in that, In step b), the electrolyte temperature for the electrolytic corrosion is 10~40℃; the current density for the electrolytic corrosion is 100~500A / m. 2 .

12. The grinding method according to claim 1, characterized in that, In step c), the grinding temperature is controlled by a combination of air cooling and emulsion cooling.

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