Roller

Abstract

The present application discloses a rolling roller, which includes a surface oxide film of a steel material formed on the surface of the rolling roller, wherein the surface oxide film of the steel material is made by the following method: applying an activation liquid to the surface of the steel material on which the Fe3O4 oxide film is to be formed, so as to form an activation film on the surface of the steel material; scanning the surface of the steel material on which the Fe3O4 oxide film is to be generated by a laser beam for heating, so that the laser scanning spot on the surface of the steel material is heated to 1450-1500°C, thereby generating the Fe3O4 oxide film at a flash speed.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of oxide films on the surface of steel materials, and in particular to a rolling mill formed by a laser high-temperature flash forming method of oxide films on the surface of steel materials. Background Art

[0002] Most industrial components are made of steel, such as rollers. Rollers are important components of hot rolling production lines. Steel strips are rolled under vertical pressure through a pair of rolling rollers. Their direct material consumption accounts for about 5-15% of the steel rolling production cost.

[0003] During the hot-rolled steel strip production process, the rollers operate under extremely harsh conditions, coming into contact with the rolled material at temperatures reaching 900-1200°C. In addition to the intense friction and wear of the rolled material, the roller surfaces are also subject to high-temperature oxidation, which forms an oxide film on the roller surface. This flaking of the oxide film exacerbates roller failure. Furthermore, the rollers are repeatedly heated by the rolled material and cooled by cooling water during operation, experiencing high-frequency rapid cooling and heating. The fatigue thermal stresses generated by these rapid cooling and heating processes can induce microcracks, which continue to expand under the action of rolling forces, ultimately leading to cracking and even flaking of the roller surface, causing roller failure. Therefore, hot-rolled rollers must possess not only high wear resistance and toughness, but also excellent resistance to oxidation and thermal fatigue.

[0004] High-speed steel has the characteristics of high toughness and high hardness in physical properties, especially high hardness at high temperature. It has the advantages of high wear resistance, good red hardness, good roughness, and good oxide film generation ability. The amount of steel rolled in a single grinding can reach 2 to 4 times that of high-chromium iron material. Therefore, high-speed steel rolls have been widely used in the front section of the finishing rolling stand (F1 to 4), and new high-speed steel rolls have been gradually developed and promoted for application in the roughing rolling stand and the back section of the finishing rolling stand.

[0005] However, high-speed steel is relatively expensive. In practical applications, composite high-speed steel rolls are often used to reduce costs. Composite high-speed steel rolls consist of a core roll with a high-speed steel sleeve, where the core roll can be made of ductile iron or other materials. During hot finish rolling, steel plates are rolled sequentially through 6 to 8 stands. The first four stands operate at high rolling temperatures of approximately 900 to 1200°C, resulting in high reduction and high rolling forces, and therefore typically utilize high-speed steel rolls.

[0006] During the hot rolling process of steel plates, a layer of oxide scale is generated on the surface of the roller due to the contact between the roller surface and the red-hot high-temperature steel billet. This oxide scale has both positive and negative effects.

[0007] Its beneficial effects are: first, it can reduce friction and reduce roll wear; second, it can prevent the red-hot steel billet from sticking to the roll surface; third, the oxide scale has a low thermal conductivity, which can isolate the roll base and the red-hot steel billet, reduce the roll base temperature, reduce thermal shock, and inhibit thermal fatigue cracks on the roll surface.

[0008] The disadvantage of roller scale is that, in conventional rolling techniques, the scale layer formed is primarily composed of loose ferrous oxide (FeO). Therefore, it easily flakes off during the subsequent rolling process. This flakes of iron oxide are pressed into the slab surface and, as rolling progresses, are stretched into chains, damaging the surface quality of the slab and forcing the rolled steel plate to be downgraded or scrapped.

[0009] According to statistics, the scrap rate of hot-rolled high-strength steel plates due to flaking of iron oxide scale is around 20%. For example, on a 6 million ton annual production line, 1.2 million tons of steel is scrapped or downgraded annually. Each downgrade results in a 500 yuan / ton difference in sales price, resulting in an annual loss of 30 million yuan for just one 6 million ton hot-rolling line. The loose iron oxide scale flakes off during the rolling process, causing severe wear on the rolls. To improve surface quality when rolling high-quality steel plates, the rolls often need to be reground after an average of less than three rolls, resulting in significant roll wear. Frequent grinding of the rolls leads to frequent downtime for roll replacement, resulting in losses and unstable quality of the rolled slabs.

[0010] There are three types of iron oxides. One is ferrous oxide (FeO). FeO is a metal-deficient p-type semiconductor with approximately 5% to 16% cation defects. Consequently, the FeO layer has a high concentration of cation vacancies, which results in high mobility of cations and electrons within the FeO layer, leading to a rapid growth rate of the FeO layer. However, FeO is black, has a loose structure, and is easily detached.

[0011] The second type is iron oxide (Fe2O3). Fe2O3 is an oxygen-deficient n-type semiconductor with a relatively high oxygen content. It has numerous internal oxygen ion defects, forming anion vacancies that facilitate the diffusion of oxygen from the outside. Fe2O3 has two crystal structures: at low temperatures, it is a metastable cubic γ-Fe2O3 crystal. Above 400°C, it becomes an oblique hexahedral α-Fe2O3. Fe2O3 is red in color. The main component of reddish-brown rust is iron oxide with n hydrates of water (Fe2O3·nH2O).

[0012] The third type is ferroferric oxide (Fe3O4). Fe3O4 is a p-type semiconductor and its stoichiometry is higher than that of FeO, so it is not conducive to Fe 2+ Diffusion, Fe3O4 consists of a Fe 2+ and two Fe 2+ 、Fe 3+ Composition, belongs to spinel structure, Fe 2+ and Fe 2+ 、Fe 3+Located in the interstices between the tetrahedrons and octahedrons, respectively. Fe3O4 is black, dense, and hard, making it useful as an abrasive and polishing agent, and also provides protection. Therefore, in industry, a blackening or bluing treatment is often used to form an Fe3O4 film on the surface of steel parts to provide corrosion protection. Therefore, if a Fe3O4 film tightly bonded to the substrate could be formed on the roll surface, the roll's high-temperature wear resistance would be greatly enhanced, extending its life and improving the surface quality of the rolled strip.

[0013] like Figure 1 As shown in the iron-oxygen reaction phase diagram, there are two situations in which Fe3O4 can be stably generated. One is low-temperature generation of Fe3O4. When the temperature is below 570°C and the oxygen content is less than 57 at%, iron and oxygen can generate ferroferric oxide. Further, based on the relationship between the Gibbs free energy and temperature in the oxidation reaction, Fe3O4 is the most stable oxidation product of pure iron below 567°C, and its thermodynamic tendency to generate is the greatest. The other is high-temperature generation of Fe3O4. That is, at 1450-1582°C and with an oxygen content greater than 58 at%, iron and oxygen can generate ferroferric oxide. In other situations, a mixture of ferrous oxide, trimer tetroxide, and ferric oxide is generally generated.

[0014] For example, CN114622154A discloses a device and process for laser forming a preformed oxide film on the surface of a hot rolling mill roll. The oxide film is formed at 800°C to 900°C. However, according to the iron-oxide reaction phase diagram, a large amount of fusinite is produced at this temperature, and no matter how long the temperature is maintained, a high proportion of Fe3O4 cannot be obtained.

[0015] In fact, in the existing technology, most of the methods are to generate Fe3O4 oxide film at a temperature below 570°C, and there are generally two ways.

[0016] One method involves high-temperature steam treatment, which involves exposing the steel workpiece to high-temperature steam at 540-570°C. This creates a blue film of ferroferric oxide (Fe₃O₄) on the surface, with a thickness of 4-6 μm. This film is fine-grained and firmly adheres to the metal surface. The process works by decomposing the water vapor on contact with the hot iron, releasing reactive oxygen atoms. These atoms then react with the metallic iron to form Fe₃O₄ nuclei, which grow and precipitate on the workpiece surface. High-temperature steam treatment requires heating the workpiece to approximately 550°C, a process that takes approximately one hour. Combined with the time required to heat the roll from room temperature to 550°C and then cool it back to room temperature after the bluing treatment, the entire process takes approximately three hours for small workpieces. This method inherently suffers from high energy consumption and a long processing time. Using this method for bluing high-speed steel rolls, which are 5.5 meters long, can reach a maximum diameter of 1 meter, and weigh up to 30 tons, presents significant practical challenges. For example, it was difficult to find such a large heating furnace, and the heating cost was too high. Second, heating the 30-ton rolls to 550°C required more than 10 hours. Third, once heated to 550°C, the high-speed steel rolls would soften due to tempering, reducing their hardness and rendering them scrapped. Fourth, during the air cooling process, the high-speed steel rolls were brittle and could crack on the surface. Therefore, the high-temperature bluing method for treating high-speed steel rolls was not feasible.

[0017] The second method for forming an Fe3O4 oxide film is alkali boiling oxidation. Specifically, at around 140°C, steel parts are placed in a mixed solution of NaOH and NaNO2 at a certain concentration. A Fe3O4 oxide film is formed through a chemical reaction. The thickness and density of the film are related to the concentration of NaOH and NaNO2 during oxidation, the temperature, and the treatment time. If the temperature is too low, the nucleation rate and growth rate of Fe3O4 are low, making it difficult for the oxide film to form. If the temperature is too high, the oxide film is easily dissolved. Therefore, the treatment temperature must be strictly controlled between 130 and 150°C. This method itself is highly polluting, and the evaporation of the strong alkali solution leads to a harsh working environment. For high-speed steel with a high alloy content, the cooking time in the alkali solution is much longer than that of ordinary carbon steel, requiring about 80 minutes. Using alkali boiling oxidation to form Fe3O4 oxide films on high-speed steel rolls presents the following challenges: First, the treatment process is long; the alkali boiling alone requires 80 minutes. Furthermore, a 30-ton roll must be heated to 130°C before being placed in a high-temperature alkali bath. Otherwise, the alkali bath temperature decreases. Heating a 5.5-meter-long, 1-meter-diameter, and 30-ton roll to approximately 140°C takes at least three hours. Including surface cleaning after removal from the alkali bath, processing a single roll takes at least six hours. Second, there is significant pollution: volatile alkali contaminates the working environment, and residual alkali on the roll surface requires special treatment. Third, treatment costs are high, requiring a large, high-temperature alkali bath. Fourth, the quality of the oxide film is difficult to guarantee. The thickness and uniformity of the oxide film are significantly affected by the alkali concentration and temperature. Such a large alkali bath, with large fluctuations in concentration and temperature, makes it difficult to ensure consistent oxide film quality across different rolls. Even on the same roll, the oxide film quality can be uneven and inconsistent due to differences in alkali concentration, temperature, and alkali flow rate.

[0018] The reason why the existing technology does not use high temperature (1450-1582°C) to form the Fe3O4 oxide film is that, firstly, the existing technology heats the workpiece as a whole, which consumes too much energy. Moreover, when the workpiece is heated to such a high temperature, the workpiece will soften. During the cooling process, it will crack due to uneven internal and external temperatures, and the material will also undergo phase change. In addition, the processing time is long, the required space is large, the equipment is complex, and a high-concentration oxygen atmosphere (oxygen content greater than 58at%) needs to be formed, which is difficult to implement in terms of performance, cost, and efficiency.

[0019] Second, from Figure 1 The iron-oxygen reaction phase diagram shows that the Fe₃O₄ oxide film forms in a very narrow region under high-temperature conditions, requiring stringent control of the conditions. Temperatures below 1450°C prevent the film from forming, while temperatures above 1500°C cause the steel to melt, necessitating precise temperature control. On the other hand, simply passing air or supplying oxygen, as the oxygen provided by these materials is molecular oxygen, not reactive oxygen atoms, and thus cannot react quickly with the steel to form an oxide film. Summary of the Invention

[0020] One advantage of the present invention is that it provides a laser high-temperature flash formation method for oxide film on the surface of steel materials. This method proposes for the first time a method for flash generation of Fe3O4 oxide film at high temperature (1450-1500°C), which solves the problem that traditional generation of Fe3O4 oxide film can only be carried out slowly at low temperature.

[0021] One advantage of the present invention is that it provides a laser high-temperature flash method for forming an oxide film on the surface of a steel material, wherein the Fe3O4 oxide film generated in situ on the surface of the steel material by the laser high-temperature flash method is tightly bonded to the steel material matrix, thereby solving the problem that traditional oxidation methods easily generate FeO and have low bonding strength.

[0022] One advantage of the present invention is that it provides a laser high-temperature flash method for forming an oxide film on the surface of a steel material, wherein the laser high-temperature flash method for forming an oxide film on the surface of a steel material can form a stable Fe3O4 oxide film on the surface of the steel material, and the operating conditions are simple and the production cost is low, thereby solving the problems of long oxidation time, high temperature and high energy consumption of traditional oxidation methods.

[0023] Another advantage of the present invention is to provide a laser high-temperature flash method for forming an oxide film on the surface of a steel material. The activation liquid is applied to the surface of the steel material to form an activation film, wherein the activation film can absorb light and increase the laser absorption rate. In addition, active Fe can be formed in the activation film in advance or at the same time as the laser is formed at high temperature. 2 + 、Fe 3+ ions, at the same time, the activated film can release active oxygen atoms and active Fe when it is decomposed at high temperature. 2+ 、Fe 3+ Ions and active oxygen atoms can combine quickly to flash-generate a Fe3O4 oxide film, thus solving the problem of high laser reflectivity and low light absorbance on the steel surface, as well as the problem of long oxidation reaction time of traditional steel, making millisecond-level flash oxidation possible.

[0024] Another advantage of the present invention is that it provides a laser high-temperature flash method for forming an oxide film on the surface of a steel material, wherein the laser high-temperature flash method for forming an oxide film on the surface of a steel material can form an Fe3O4 oxide film in an extremely short time (such as 0.01 to 10 milliseconds).

[0025] Another advantage of the present invention is that it provides a laser high-temperature flash method for forming an oxide film on the surface of a steel material. By rapidly scanning the surface of the steel material with a high-energy laser beam used for heating, local high temperature is formed only at a depth of microns at the laser spot on the surface of the steel material, thus solving the problems of traditional methods requiring overall heating, complex equipment, large site, high energy consumption and low efficiency.

[0026] To achieve at least one of the above advantages, the present invention provides a laser high-temperature flash method for forming an oxide film on the surface of a steel material. The laser high-temperature flash method for forming an oxide film on the surface of a steel material comprises:

[0027] Applying an activation liquid on the surface of the steel material on which the Fe3O4 oxide film is to be formed, so as to form an activation film on the surface of the steel material; and

[0028] The surface of the steel material on which the Fe3O4 oxide film is to be formed is scanned with a laser beam for heating, so that the laser scanning spot on the surface of the steel material is heated to 1450-1500° C., thereby generating the Fe3O4 oxide film at a flash speed.

[0029] According to one embodiment of the present invention, the activation film contains Fe 2+ 、Fe 3+ ion.

[0030] According to one embodiment of the present invention, pre-treating the surface of the steel material includes:

[0031] Grinding the surface of steel materials to remove the surface fatigue layer; and / or

[0032] Cleaning the emulsion or oil stains on the surface of the steel material by alkali and then removing the emulsion or oil stains on the surface of the steel material by water washing; and / or

[0033] Wipe the steel surface with alcohol.

[0034] According to an embodiment of the present invention, the activation solution is an activation solution containing oxygen acid ions.

[0035] According to one embodiment of the present invention, the activation solution containing oxygen acid radical ions is an activation solution containing phosphate ions and / or sulfate ions and / or nitrate ions and / or hypochlorite ions.

[0036] According to one embodiment of the present invention, the laser high-temperature flash method for forming an oxide film on the surface of a steel material comprises the following steps:

[0037] Before or simultaneously with the laser beam scanning, a light absorber is coated on the surface of the activated film.

[0038] According to an embodiment of the present invention, the light absorber is a carbon-based light absorber.

[0039] According to an embodiment of the present invention, the steel material is a rolling mill roll.

[0040] According to an embodiment of the present invention, while the surface of the steel material is irradiated with a laser beam for heating, oxygen is sprayed toward the laser spot on the surface of the steel material.

[0041] According to an embodiment of the present invention, the flow rate of the oxygen is 0.1 to 15 L / min.

[0042] According to an embodiment of the present invention, the time for forming the oxide film is 0.01 to 10 milliseconds.

[0043] According to an embodiment of the present invention, the activation film is dark in color.

[0044] According to one embodiment of the present invention, the activation solution is an activation solution free of oxygen-containing acid radical ions, wherein the laser high-temperature flash method for forming an oxide film on the surface of a steel material comprises:

[0045] While the surface of the steel material is irradiated with a laser beam for heating, oxygen is sprayed toward the laser spot on the surface of the steel material.

[0046] According to an embodiment of the present invention, the activation solution is an activation solution containing halogen ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The iron-oxygen reaction phase diagram is shown.

[0048] Figure 2 A flow chart of a method for forming an oxide film on the surface of a steel material at a high temperature by laser flash is shown in one embodiment. DETAILED DESCRIPTION

[0049] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are for illustrative purposes only, and those skilled in the art will readily appreciate other obvious variations. The basic principles of the present invention defined in the following description may be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the present invention.

[0050] Those skilled in the art should understand that, in the disclosure of the present invention, the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like to indicate orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0051] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the elements may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0052] refer to Figure 2 A method for forming an oxide film on the surface of a steel material by laser high-temperature flash according to a preferred embodiment of the present invention will be described in detail below. The method for forming an oxide film on the surface of a steel material by laser high-temperature flash comprises the following steps:

[0053] S1001, the activation liquid is applied to the surface of the steel material where the Fe3O4 oxide film is to be formed, such as the surface of the roll, to form a layer of Fe3O4 oxide film on the surface of the steel material. 2+ 、Fe 3+ Ion-activated membrane.

[0054] In one embodiment, the activation solution is an activation solution containing oxygen acid ions.

[0055] For example, the activation liquid is implemented as sulfuric acid or / and sulfate, and sulfuric acid or / and sulfate is applied to the surface of a steel material such as a roller to pre-activate the roller surface, so that the iron element on the surface of the steel material reacts with sulfate ions, and a layer of FeSO4 or Fe2(SO4)3 activation film is generated according to different sulfate ion concentrations and reaction temperatures. Compared with Fe atoms, Fe 2+ 、Fe 3+ The ions are more active, thereby increasing the activity of the oxidation reaction, so that a layer of Fe3O4 oxide film can be flash-formed on the steel material at high temperature.

[0056] In addition, SO4 2— It decomposes at high temperatures to produce active [O] elements, which are more likely to promote the formation of Fe3O4 oxide film than oxygen.

[0057] By forming a layer containing Fe on the surface of the steel material 2+ 、Fe 3+ ion activation membrane, due to the Fe 2+ 、Fe 3+ The ion activity is high and it can quickly form Fe3O4 oxide film in a high temperature environment.

[0058] For example, in one example, a layer containing Fe is formed on the surface of the steel material by coating sulfuric acid or / and sulfate. 2+ 、Fe 3+Ion activation film. Sulfuric acid or sulfate reacts with iron and steel materials, such as the iron on the surface of a rolling mill roll, to form FeSO4 or Fe2(SO4)3 films. The FeSO4 or Fe2(SO4)3 films are dark colors such as yellow, yellow-brown, brown, or brown-black. The specific color is determined by the duration of the reaction; the longer the reaction time, the darker the color.

[0059] Without this dark activation film, the surface of the roller after grinding will be bright silver, and the reflectivity to the laser will be extremely high. On the one hand, this will lead to low laser efficiency. On the other hand, since the surface of the roller is a circular arc, the reflectivity of the laser on the roller surface is different, that is, the absorbance of the same spot at different positions is different. The different absorbance will lead to different temperatures, which will lead to uneven oxide film, thus causing uneven Fe3O4 oxide film generated later. Therefore, the activation treatment of the roller surface with the activation solution has three effects at the same time. On the one hand, it forms active Fe 2+ 、Fe 3+ ions and active [O] elements promote the rapid formation of Fe3O4 oxide film. Secondly, the dark ferric nitrate film can greatly improve the absorbance. Thirdly, it ensures the uniformity and consistency of the quality of the generated Fe3O4.

[0060] More importantly, since the activated film can release active [O] elements after decomposition at high temperatures, there is no need for additional oxygen to be introduced, and the Fe3O4 oxide film can be quickly formed on the surface of the steel material at high temperatures (1450-1500°C).

[0061] Preferably, in step S1001, when sulfuric acid or / and sulfate are used as the activation solution, the sulfate ions [SO4 2- ] The concentration is 0.5~15mol / L.

[0062] In another embodiment, the oxygen-containing acid radical ion activation solution is implemented as a solution containing nitrate ions (NO3 - ) to form active Fe 2+ 、Fe 3+ It is understood that the nitrate-containing ferrous nitrate and ferric nitrate activation film. - ) activated film can also provide active [O] elements when it forms a high temperature under subsequent laser beam irradiation, thereby promoting the rapid formation of Fe3O4 oxide film. In addition, the generation of nitrate ions (NO3 - ) is used, the surface of the steel material gradually changes from silvery white to a dark color, such as yellow, brown, or brown-black, which can increase the laser absorbency and significantly reduce laser reflection.

[0063] In another embodiment, the oxygen acid radical ion activation solution is implemented as a solution containing hypochlorite ions (ClO - ) to form active Fe 2+ 、Fe 3+ It is understood that the ferrous hypochlorite and ferric chloride containing hypochlorite ions (ClO - ) activated film can provide active [O] elements by decomposition when the laser beam forms a high temperature, thereby promoting the rapid formation of Fe3O4 oxide film. In addition, the generation of chlorine hypochlorite (ClO - ) after the activation film is formed, the surface of the steel material gradually changes from silvery white to dark colors, such as green, yellow-green, and yellow, which increases the laser absorbency and reduces the laser reflection.

[0064] In another embodiment, the oxygen acid ion-containing activation solution is implemented as an iron-based phosphating solution containing phosphate ions.

[0065] Preferably, the main components of the iron phosphating solution are phosphoric acid (H3PO4) and sodium dihydrogen phosphate (NaH2PO4), the oxidant is NaNO3, Fe 2+ 、Fe 3+ It is generated by the reaction between the iron atoms on the surface of the steel material and the phosphating solution.

[0066] It is worth mentioning that, in this embodiment, the iron-based phosphating solution has a phosphate concentration of 10 to 30 g / L and a pH value of 2.0 to 3.0.

[0067] According to the different components of the phosphating solution, phosphating treatment includes zinc-based, manganese-based, zinc-calcium-based and iron-based phosphating. The characteristic of iron-based phosphating is that the phosphating solution contains Fe. 2+ 、Fe 3+ Ions, iron ions can be provided by dissolving on the surface of steel. Compared with zinc, manganese and zinc-calcium systems, iron phosphating has the advantages of thin phosphating film thickness (less than 1μm), high porosity and low density (film weight 0.2~1g / m 2 Due to the characteristics of iron phosphate coatings, the color of the coating is mostly bluish-purple. Depending on the reaction time, film thickness, and the composition of the phosphating solution, it can also appear iridescent or gray. Therefore, dark iron-based phosphating coatings can be used as laser absorbers. Furthermore, their thinness and high porosity allow oxygen to pass through the coating and contact the iron in the steel substrate. Therefore, the present invention uses an iron-based phosphating solution for the surface activation treatment of steel workpieces.

[0068] During the phosphating process, the surface of the steel substrate reacts with the phosphoric acid or hypophosphite in the phosphating solution. The atoms on the outer layer of the steel workpiece react with the anions in the solution, which act as a medium. The soluble phosphates on the surface are continuously converted into insoluble phosphates, ultimately depositing a phosphate conversion film on the surface of the steel workpiece. The main components of the iron-based phosphating film are FePO4, Fe3(PO4)2, and Fe(OH)3.

[0069] In this embodiment, the phosphate (PO4 3- ) concentration range is different from that of ordinary phosphating solution. The phosphate radical (PO4 3- ) concentration is 10-30 g / L, while the concentration of phosphate in ordinary phosphating solution is generally greater than 30 g / L. In the present invention, if the phosphate (PO4 3- ) concentration is less than 10g / L, the film is too thin and the color is too light, which is not conducive to improving the absorbance. 3- When the concentration is greater than 30 g / L, the film thickness is too large, the density increases, and it is not conducive to the subsequent oxygen penetration. For ordinary phosphating solutions, the goal is to obtain a phosphating film with low porosity, high corrosion resistance, and a large thickness. For the present invention, the goal is to obtain a phosphating film with a blue-purple, rainbow-colored, or gray color, a loose and porous structure, and a thin thickness. Therefore, the phosphating process parameter selection ranges for the two are different.

[0070] The phosphate film in this embodiment is characterized by being bluish purple, rainbow or gray in color, having a thin thickness and low corrosion resistance, so as to improve the laser absorption rate.

[0071] The pH of the phosphating solution in this embodiment also differs from that of conventional phosphating solutions. The pH of the phosphating solution in this embodiment is 2.0-3.0, while conventional phosphating solutions generally have a pH of 3.0-4.5. A low pH results in a high amount of hydrogen evolution and a loose and porous film. However, a pH below 2.0 results in rapid localized corrosion, leading to an uneven phosphating film. A pH above 3.0 increases the film density and thickness, hindering oxygen permeation during the subsequent oxygen injection process. Conventional phosphating processes, on the other hand, use a higher pH to produce a dense, thick, and corrosion-resistant phosphating film. In another embodiment, the activation solution can also be an oxyacid ion-free activation solution.

[0072] Preferably, the activation solution containing oxygen-free acid radical ions can be implemented as an activation solution containing halogen ions.

[0073] For example, the oxygen-free acid radical ion activation solution is implemented as a chloride ion (Cl - ) to form active Fe 2+ 、Fe 3+ The active Fe contained in the activated film 2+ 、Fe3+ Ions are beneficial to the rapid formation of Fe3O4 oxide film. However, compared with the activation solution containing oxygen acid radical ions, the chloride ion (Cl - ) is unable to provide active [O] elements when it forms a high temperature under subsequent laser beam irradiation. Therefore, when the laser is irradiating the surface of the steel material, oxygen must be sprayed onto the laser spot on the surface of the material at the same time.

[0074] In one embodiment, the activation solution of the oxygen-free acid radical ion can be implemented as a solution containing chloride ions (Cl - ) activation solution. Contains chloride ions (Cl - ) is used, the surface of the steel material gradually changes from silvery white to a dark color, such as yellow, brown, or brown-black, which can increase the laser absorbency and significantly reduce laser reflection.

[0075] In another embodiment, the oxygen-free acid radical ion activation solution is implemented as a bromide ion (Br - ) to form active Fe 2+ 、Fe 3+ Ionic ferrous bromide and ferric bromide activated membrane. The active Fe contained in the activated membrane 2+ 、Fe 3+ Ions are beneficial to the rapid formation of Fe3O4 oxide film. However, compared with the activation solution containing oxygen acid radical ions, the chloride ion (Cl - ) activated film is unable to provide active [O] elements when it forms a high temperature under subsequent laser beam irradiation. Therefore, when the laser irradiates the surface of the steel material, oxygen must be sprayed to the laser spot on the surface of the material at the same time. In addition, chloride ions (Cl - ) after the activation liquid is used, the surface of the steel material gradually changes from silvery white to a dark color, such as brown, reddish brown, and tan, which can increase the laser absorbency and significantly reduce the laser reflection.

[0076] It will be understood by those skilled in the art that the above-mentioned activation solution is used to form the Fe-containing 2+ 、Fe 3+ The surface of the ion activation film is dark, which is darker and more uniform compared to the steel material without the activation film. This can effectively prevent the reflection of the subsequent laser and maintain the consistency of light absorption, so that the surface of the steel material can be uniformly heated to a high temperature by the laser, thereby ensuring the uniformity of the thickness of the Fe3O4 oxide film formed subsequently.

[0077] The laser high-temperature flash method for forming an oxide film on the surface of a steel material comprises the following steps:

[0078] S1002, heating the surface of the steel material on which the Fe3O4 oxide film is to be formed to 1450-1500°C by using a laser beam for heating, so as to form the Fe3O4 oxide film at a flash speed.

[0079] Specifically, in step S1002, a laser beam directed from a laser head is irradiated onto the surface of a steel material, such as the surface of a rolling mill.

[0080] The roller rotates at a high speed at a rotation speed ω, which is between 50rpm and 500rpm. At the same time, the laser head and the oxygen injection tube make a linear feed motion along the axis of the roller at a speed v. The feed speed v of the roller is 50-500mm / min, the spot area of ​​the laser beam is 0.05-2mm2, the overlap rate is 30-80%, and the laser power is 2000W-6000W.

[0081] While the laser scans the workpiece surface, if the activated film is produced by coating the steel surface with an oxygen-free acid, oxygen is injected through an oxygen injection tube at the laser irradiation spot on the workpiece surface. If the activated film is produced by coating the steel surface with an oxygen-containing acid, oxygen injection can be performed through the oxygen injection tube at the laser irradiation spot, or it can be omitted. The oxygen flow rate is 0.1 to 15 L / min. Under the irradiation of the high-energy laser beam, the temperature of the roller surface at the laser irradiation spot instantly rises to 1450 to 1500°C, and an Fe3O4 oxide film is instantly formed in situ on the roller surface.

[0082] Preferably, the laser high-temperature flash method for forming an oxide film on the surface of a steel material comprises the steps of:

[0083] S1003, pre-treating the surface of the steel material. Those skilled in the art should understand that step S1003 includes:

[0084] S100331, grinding the surface of steel materials to remove the surface fatigue layer.

[0085] More preferably, the step S1003 includes:

[0086] S10032, clean the emulsion or oil stains on the surface of the steel material with alkali, and remove the emulsion or oil stains on the surface of the steel material by washing with water.

[0087] Preferably, after step S10032, pre-treating the surface of the steel material further comprises:

[0088] S10033, wipe the surface of steel materials with alcohol.

[0089] It is particularly worth mentioning that if there is residual emulsion or oil on the surface of the steel material, the uniformity of the activated film in the subsequent pre-activation process cannot be guaranteed.

[0090] Furthermore, in step S1002, the surface of the steel material is irradiated with a high-energy laser beam. Therefore, sufficient heat can be instantly provided to raise the temperature of the roller surface to the required temperature. In order to rapidly raise the temperature of the roller surface to 1450-1500°C, the present invention uses a high-power, small-spot laser to obtain a high energy density. The high-power laser refers to a laser with a power of 2000W to 10000W. If the laser power is less than 2000W, the energy is insufficient, and the spot is too small, which reduces the efficiency of oxide film formation. If the laser power is greater than 10000W, the energy is too high, which may cause over-burning, and the steel material needs to move at a too high speed, making it difficult to match the corresponding motion mechanism. Therefore, the laser power is preferably 2000W to 10000W.

[0091] The spot shape formed by the laser beam can be a small circular, square or rectangular spot, wherein the small spot refers to a spot with an area of ​​0.05 to 10 mm 2 If the laser spot area is less than 0.05mm 2 , it will seriously reduce production efficiency. And the spot area is larger than 10mm 2 , the energy density is insufficient, and the surface temperature of the steel material is difficult to reach 1450-1500°C, so the spot area is 0.05-10mm 2 The spot overlap rate is 30% to 80%. If the spot overlap rate is less than 30%, the laser energy is insufficient due to the virtual light effect at the edge of the laser spot, resulting in the inability to form an Fe3O4 oxide film. If the overlap rate is greater than 80%, the steel material may be melted and the production efficiency will be reduced.

[0092] In one embodiment, the steel material is set as a rolling roller, and the speed range of the rolling roller during the preparation process is ω, which is 50 to 500 rpm. If the laser power is large, the speed can be appropriately increased. If the speed is lower than 50 rpm, the production efficiency is low; if the speed exceeds 500 rpm, since the weight of the rolling roller can reach 30 tons, the speed is too high and will cause production safety hazards. Therefore, the speed should be 50 to 500 rpm.

[0093] Correspondingly, in this embodiment, the linear feed speed v of the laser head along the axial direction of the roller is in the range of 50 to 500 mm / min. If the feed speed is lower than 50 mm / min, firstly, the production efficiency is low, and secondly, the roller surface is melted due to overburning caused by excessive power density; if the feed speed is greater than 500 mm / min, the power density on the roller surface is too low and the Fe3O4 oxide film cannot be generated.

[0094] Furthermore, the second condition for forming an oxide film at high temperature is that the oxygen content is greater than 58at%, while the oxygen content in the atmosphere is only 21at%. If the oxygen content is insufficient, Fe3O4 cannot be generated even if the temperature reaches 1450-1500°C. The activation film in the present invention can be generated by coating an oxygen-containing acid or an oxygen-free acid activation liquid on the surface of the steel material. If the activation film is generated by coating an oxygen-containing acid activation liquid on the surface of the steel material, the activation film can provide a large amount of active oxygen atoms when heated by laser irradiation, meeting the conditions required for forming the Fe3O4 oxide film. If the activation film is generated by coating an oxygen-free acid activation liquid on the surface of the steel material, oxygen needs to be sprayed onto the laser spot on the surface of the steel material.

[0095] Of course, as a preference, the laser high-temperature flash method for forming an oxide film on the surface of a steel material comprises the following steps:

[0096] S1004, while irradiating the surface of the steel material with a laser beam, spraying oxygen toward the laser spot on the surface of the steel material.

[0097] It is worth mentioning that if the activation film is generated by coating the surface of the steel material with an oxygen-containing acid activation liquid, this step is optional. If the activation film is generated by coating the surface of the steel material with an oxygen-free acid activation liquid, this step is necessary.

[0098] It is worth mentioning that the injected oxygen is directed toward the light spot formed on the surface of the steel material by the laser beam.

[0099] The present invention proposes a method of spraying oxygen onto the surface of the roller. For example, oxygen can be sprayed from the air jet pipe onto the laser spot to provide sufficient oxygen elements for the oxidation of the roller surface. The oxygen flow rate is 0.1 to 15 L / min. If the oxygen flow rate is less than 0.1 L / min, the oxygen supply is insufficient. If the oxygen flow rate is greater than 15 L / min, the oxygen supply is excessive.

[0100] Furthermore, the research found that if the surface of the steel material is not coated with activation liquid and no activation film is formed, even if oxygen is sprayed on the surface of the roll, the effect of forming the Fe3O4 oxide film is still not ideal, the oxide film is thin and uneven. The reason is that if the Fe3O4 oxide film is to be formed quickly, Fe 2+ 、Fe 3+ ions. In order to form Fe on the roller surface before laser oxidation 2+ 、Fe 3+ ions, we apply the activation solution containing oxygen-containing acid radical ions and / or oxygen-free acid radical ions on the roller surface, such as sulfate ions [SO4 2- ] activation liquid, so that the iron element on the surface of the roller reacts with sulfate ions to form Fe 2+ 、Fe3+ ions, thereby increasing the activity of the oxidation reaction. On the other hand, at the same time, (SO4 2- ) The activated film decomposes at high temperature to produce active [O] elements. These decomposed [O] elements are highly active and can promote the formation of Fe3O4 oxide film more effectively than oxygen. 2- ) concentration is controlled at 0.5-15 mol / L. If it is lower than 0.5 mol / L, the reaction is too slow. If it is higher than 15 mol / L, the concentration is too high and it will volatilize and cause environmental pollution. Moreover, if the concentration is too high, the surface may be passivated, which is not conducive to the generation of iron ions. Laser oxidation treatment can be carried out 3-60 minutes after the activation solution is applied. If it is lower than 3 minutes, the reaction is incomplete, the degree of activation is low, and the oxide film is thin. If it exceeds 60 minutes, an over-reaction occurs, resulting in uneven thickness and color of the activation film, and uneven Fe3O4 oxide film. Preferably, the laser high-temperature flash method for forming an oxide film on the surface of a steel material comprises the steps of:

[0101] S1005, further coating a light absorber on the surface of the activated film of the steel material to form a light absorption layer on the surface of the steel material to further improve the light absorption rate.

[0102] It is worth mentioning that in a variant embodiment, instead of applying the activation solution to the surface of the steel material, the light absorber can be directly applied to the surface of the steel material. Simultaneously, the laser beam is irradiated onto the surface of the steel material while oxygen is injected into the laser spot on the surface of the steel material. This can also cause the Fe3O4 oxide film to flash form on the surface of the steel material at a high temperature of 1450-1500°C.

[0103] It is understood that the light absorber coated on the steel surface improves the steel's laser absorption efficiency when subsequently irradiated by the laser beam, thereby rapidly heating the steel surface to 1450-1500°C. The melting point of high-speed steel is generally between 1500-1600°C; above this temperature range, the steel melts. Therefore, the laser oxidation temperature should be controlled below 1500°C. Forming the Fe₃O₄ oxide film on the steel surface requires a temperature of 1450-1500°C, which is very close to the melting range of steel. If the laser alone is used to heat the steel, and the steel surface has low light absorption efficiency, the laser absorption rate is difficult to control, potentially causing the steel to melt during heating. In other words, the light absorber effectively stabilizes the laser heating temperature, preventing the steel from melting during heating.

[0104] The light absorber is preferably a carbon-based light absorber. The carbon-based light absorber can be set as a carbon-based micropowder dispersion, in which the carbon-based micropowder is uniformly dispersed in a solvent. For example, the carbon-based micropowder can be a carbon-based powder material such as flake graphite, graphene, carbon nanotubes, etc. with a characteristic size between 10nm and 100μm. The solvent is formed by adding surfactants such as sodium carboxymethyl cellulose, polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), sodium dodecylbenzene sulfonate, etc. to an organic or inorganic solvent such as water, ethanol, ethylene glycol or acetone, and then the carbon-based micropowder can be uniformly dispersed in the solvent through processes such as stirring and ultrasonic vibration.

[0105] When the light absorber is implemented as a carbon-based light absorber, the carbon-based light absorber will cover the surface of the Fe3O4 oxide film with a carbon-based lubricating film. This carbon-based lubricating film can reduce the surface friction of the steel material, thereby reducing the wear of the steel material.

[0106] According to another aspect of the present invention, the present invention also provides a rolling mill having the Fe3O4 oxide film on its surface formed by the above-mentioned laser high-temperature flash method for forming the oxide film on the surface of the steel material.

[0107] Example 1

[0108] On a hot finishing rolling 1780 production line, the F1 rolling mill roll was originally a high-speed steel roll. On the basis of the high-speed steel roll, a layer of Fe3O4 oxide film was prepared. The thickness of the oxide film was 5μm. The average millimeter rolling capacity of the original roll was 4300 tons. After the new Fe3O4 oxide film composite roll was used, the millimeter rolling capacity reached 12360 tons, and the service life was increased by 3 times. The preparation method of the Fe3O4 oxide film consists of three steps. The first step is the pre-treatment of the roll surface. The F1 roll is ground on the grinder after being unloaded from the machine. The surface roughness after grinding is 0.5μm. Alkaline washing is used for degreasing, and finally it is washed with water and dried. The surface of the roll after pre-treatment is bright silver; the second step is surface pre-activation. The activation liquid is a H2SO4 solution with a concentration of 3mol / L. The activation liquid is coated on the roll surface to form a yellow activation film on the roll surface, forming an active Fe 2+ 、Fe 3+ ions, the roller surface after surface pre-activation treatment is yellow-brown; the third step, laser rapid oxidation, laser power 6kw, circular spot, spot diameter 3mm, overlap rate 50%, roller speed 160rpm, laser head axial feed speed 200mm / min, oxygen flow 5L / min, for the roller that has been fully laser oxidized, the roller is covered with a black Fe3O4 oxide film.

[0109] Example 2

[0110] On a hot finishing rolling 1422 production line, the F2 mill rolls were originally high-speed steel rolls. On the basis of these high-speed steel rolls, a layer of black Fe3O4 oxide film was prepared with a thickness of 7μm. The average millimeter rolling capacity of the original rolls was 8,200 tons. After adopting the new Fe3O4 oxide film composite rolls, the millimeter rolling capacity reached 46,300 tons, and the service life was increased by more than 5 times. The preparation method of the Fe3O4 oxide film consists of three steps. The first step is the surface treatment of the roll surface. The F2 rolls are ground on a grinder after being unloaded from the machine. The surface roughness after grinding is 0.3μm. Alkaline washing is used for degreasing, and finally the rolls are washed with water and dried. The second step is surface pre-activation. The activation liquid is a NiSO4 solution with a sulfate ion concentration of 6 mol / L. A yellow-green activation film is formed on the roll surface to form an active Fe 2+ 、Fe 3+ ions; the third step is laser rapid oxidation, laser power 8kw, circular spot, square spot with side length of 2.5mm, overlap rate 30%, roller speed 200rpm, laser head axial feed speed 260mm / min, oxygen flow rate 10L / min.

[0111] Example 3

[0112] On a hot finishing rolling 2250 production line, the F4 mill rolls were originally high-speed steel rolls. On the basis of the high-speed steel rolls, a layer of black Fe3O4 oxide film was prepared with an oxide film thickness of 8μm. The average millimeter rolling capacity of the original rolls was 6500 tons. After the new Fe3O4 oxide film composite rolls were used, the millimeter rolling capacity reached 26370 tons, and the service life was increased by more than 4 times. The preparation method of the Fe3O4 oxide film consists of three steps. The first step is the surface treatment of the roll surface. The F4 rolls are ground on a grinder after being taken off the machine. The surface roughness after grinding is 0.6μm. Alkaline washing is used for degreasing, and finally washed with water and dried. The second step is surface pre-activation. The activation solution is a mixed solution of Cu(NO3)2 and Y(NO3)3 with a nitrate ion concentration of 12mol / L. A brown activation film is formed on the roll surface to form an active Fe 2+ 、Fe 3+ ions; the third step is laser rapid oxidation, the laser power is 10000kw, a rectangular laser spot is used, the spot length is 3mm, the width is 2mm, the overlap rate is 50%, the roller speed is 300rpm, the laser head axial feed speed is 300mm / min, and the oxygen flow rate is 12xL / min.

[0113] Example 4

[0114] On a hot finishing rolling 1780 production line, the F3 rolling mill rolls were originally high-speed steel rolls. On the basis of these high-speed steel rolls, a layer of black Fe3O4 oxide film was prepared with a thickness of 4μm. The average millimeter rolling capacity of the original rolls was 9,100 tons. After adopting the new Fe3O4 oxide film composite rolls, the millimeter rolling capacity reached 27,650 tons, and the service life was increased by more than 3 times. The preparation method of the Fe3O4 oxide film consists of three steps. The first step is the surface treatment of the roll surface. The F3 rolls are ground on a grinder after being unloaded from the machine. The surface roughness after grinding is 0.3μm. Alkaline washing is used for degreasing, and finally the rolls are washed with water and dried. The second step is surface pre-activation. The activation liquid is a FeCl3 mixed solution with a chloride ion concentration of 7 mol / L. A brown-black activation film is formed on the roll surface to form an active Fe 2+ 、Fe 3+ ions; the third step is laser rapid oxidation, the laser power is 6000kw, a rectangular laser spot is used, the spot length is 2mm, the width is 2mm, the overlap rate is 50%, the roller speed is 200rpm, the laser head axial feed speed is 200mm / min, and the oxygen flow rate is 15L / min.

[0115] Those skilled in the art will appreciate that the embodiments of the present invention described above and shown in the accompanying drawings are intended to be illustrative only and are not intended to limit the present invention. The advantages of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and illustrated in the embodiments. Any variations or modifications may be made to the embodiments of the present invention without departing from the principles described.

Claims

1. Roller, characterized in that The roller includes a steel material surface oxide film formed on the surface of the roller, wherein the steel material surface oxide film is made by the following method: Applying an activation liquid on the surface of the steel material on which the Fe3O4 oxide film is to be formed, so as to form an activation film on the surface of the steel material; and Scanning the surface of the steel material on which the Fe3O4 oxide film is to be formed by a laser beam for heating, so that the laser scanning spot on the surface of the steel material is heated to 1450-1500° C., thereby forming the Fe3O4 oxide film at a flash speed; The activation solution is an activation solution containing oxygen acid radical ions or an activation solution containing oxygen-free acid radical ions containing halogen ions.

2. The roller according to claim 1, characterized in that: The activated film contains Fe 2+ 、Fe 3+ ion.

3. The roller according to claim 1, characterized in that: Pre-treating the surface of the steel material, comprising: Grinding the surface of steel materials to remove the surface fatigue layer; and / or Cleaning the emulsion or oil stains on the surface of the steel material by alkali and then removing the emulsion or oil stains on the surface of the steel material by water washing; and / or Wipe the steel surface with alcohol.

4. The roller according to claim 1, characterized in that: The activation solution containing oxygen acid radical ions is an activation solution containing phosphate ions and / or sulfate ions and / or nitrate ions and / or hypochlorite ions.

5. The roller according to claim 4, characterized in that: The activation solution containing phosphate ions is an iron-based phosphating solution, wherein the phosphate concentration is 10-30 g / L and the pH value is 2.0-3.

0.

6. The roller according to any one of claims 1 to 3, characterized in that: The roller comprises the steps of: Before or simultaneously with the laser beam scanning, a light absorber is coated on the surface of the activated film.

7. The roller according to claim 6, characterized in that: The light absorber is a carbon-based light absorber.

8. The roller according to claim 1, characterized in that: While the surface of the steel material is irradiated with a laser beam for heating, oxygen is sprayed toward the laser spot on the surface of the steel material.

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