A method of manufacturing a roll

Abstract

This invention discloses a method for preparing rolling mill rolls, belonging to the fields of rolling mill roll manufacturing and electroslag metallurgy. It employs a dual independent electroslag system, coupled with in-situ electrochemical activity monitoring-pulsed aluminothermic reduction, ultrasonic-electropulsion synergistic solidification, and rare earth slag closed-loop recycling technology. The prepared rolling mill roll includes a roll core and a rare earth modified working layer. This invention solves the problems of lack of dynamic control of rare earth elements, formation of brittle interfacial phases, random carbide precipitation, and waste of rare earth slag in existing technologies. The resulting rolling mill roll exhibits a cross-sectional hardness uniformity of ≤±0.5HRC, overall performance fluctuation of ≤±2%, and a service life more than twice that of traditional processes. It is suitable for preparing high-end rolling mill rolls for extreme working conditions such as aerospace special steel and ultra-high strength steel for new energy vehicles.

Description

Technical Field

[0001] This invention belongs to the field of roll manufacturing and electroslag metallurgy technology, specifically relating to a roll preparation method that obtains high-purity composite rolls through integrated electroslag melting and casting. It is suitable for the large-scale preparation of high-end composite rolls with extreme requirements for cleanliness, microstructure uniformity, interface bonding reliability, wear resistance, and thermal fatigue resistance under extreme working conditions such as aerospace special steel and new energy vehicle ultra-high strength steel. Background Technology

[0002] Rolls are core consumables in steel rolling production, and their performance directly determines the dimensional accuracy, surface quality, and production efficiency of the steel. During service, rolls are subjected to complex stress states, potentially leading to the following failure modes: spalling caused by the propagation of subsurface cracks due to localized overload and temperature rise is the primary form of damage; under long-term cyclic thermal stress, thermal fatigue cracks of varying coarseness and density form on the roll surface; fracture caused by material defects, thermal fatigue crack propagation, or mechanical overload; and wear generated from the contact between the roll surface and the rolled workpiece directly affects the roll's service life and the product's surface quality.

[0003] With the rapid development of high-end manufacturing industries, high-end steel materials such as special steel for aerospace and ultra-high-strength steel for new energy vehicles have put forward stringent requirements for rolling equipment, including "high hardness, high toughness, high wear resistance, high thermal fatigue, long life and high consistency". Composite rolls have become the mainstream development direction of high-end rolls because they combine the performance advantages of "high toughness of the roll core" and "high wear resistance of the working layer".

[0004] Electroslag remelting (ESR) is the core process for preparing high-performance composite rolls. It utilizes the electroslag thermal effect to achieve metal refining and interfacial metallurgical bonding. Through secondary remelting and refining with slag thermal resistance, it can significantly improve the purity, density, and homogeneity of the roll blank, resulting in advantages such as high cleanliness, good bonding strength, and uniform microstructure. However, existing ESR composite roll technology still faces several technical bottlenecks: the thermodynamics of rare earth oxide reduction is mismatched with the physical properties of the slag; the dual ESR system cannot independently control temperature, creating a contradiction between process continuity and interfacial oxidation-free processes; gradient temperature control of the roll core is difficult, making it impossible to achieve precise control of "surface melting and core toughness preservation"; ultra-clean purification and inclusion spheroidization cannot be coordinated, with oxygen content > 50 ppm and sulfur content > 30 ppm; high-alloy carbides are prone to coarse network precipitation, with secondary dendrite spacing > 50 μm and average carbide size > 20 μm; and the interfacial metallurgical bonding is discontinuous, with an element diffusion layer thickness < 5 μm, making it prone to cracking and spalling under heavy load conditions.

[0005] Meanwhile, the following key issues urgently need to be addressed: Lack of dynamic and precise control during rare earth reduction: The use of static pre-mixed slag and one-time aluminum addition cannot respond in real time to the dynamic changes in rare earth oxide activity caused by slag component volatilization, slag shell formation, and steel melt reaction consumption during electroslag remelting. This results in a difference of over 0.02 wt% in rare earth content along the length of the ingot, and performance fluctuations exceeding ±10% along the entire roll length, severely affecting the consistency of mass production; Insufficient toughness and formation of brittle phases at the composite interface: When the aluminum-based reduction protectant on the roll core surface reacts with the working layer molten metal, brittle Fe3Al and FeAl intermetallic compounds (hardness HV > 800, toughness < 5 J / cm) are easily formed at the interface. 2 This leads to a decrease in overall interface toughness of more than 30%. Under heavy-load alternating rolling conditions, it is prone to fracture along the brittle phase at the interface, causing early failure of the roll. The randomness and control precision of high alloy carbide precipitation are insufficient: Carbide precipitation cannot be precisely controlled in time and space by only controlling rare earth elements and cooling rate. There are still 5-10% of the area with coarse carbides (size >10μm) and local network carbides, which leads to a decrease in local wear resistance and impact resistance of the roll and a large dispersion in service life. Waste of rare earth slag resources and environmental pressure: The electroslag after use still contains 10-20wt% rare earth oxides. Current technology directly discards it as industrial waste, causing a serious waste of valuable rare earth resources. At the same time, the random discharge of fluorine-containing waste also brings environmental risks of soil and groundwater pollution.

[0006] It is evident that existing technologies cannot achieve the synergistic goals of precise and controllable rare earth elements, strong and tough interface bonding, refined organization throughout the entire process, green resource recycling, and intelligent and stable production. This severely restricts the independent production and application of high-end rolling mill rolls in my country. Therefore, it is urgent to develop a new rolling mill roll preparation method. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned problems existing in the prior art and provide an integrated electroslag casting preparation method for rolling mill rolls. This method achieves dynamic and precise control of rare earth elements, full dispersion and refinement of carbides, and recycling of rare earth resources. The result is an ultra-clean, highly uniform, highly interfacially bonded, and long-life rolling mill roll, which can meet the requirements of the steel industry for high precision, long life, and high reliability as it transforms towards green, efficient, low-carbon, and environmentally friendly practices, as well as the rapid development of downstream industries such as new energy and automobiles.

[0008] To achieve the above objectives, the present invention provides a method for preparing a rolling mill roll, comprising the following steps:

[0009] (1) Weigh each raw material according to the component ratio, mix them evenly, place them in a medium frequency induction furnace for pre-melting, quench them in water to form slag particles, and dry and sieve them to obtain electroslag.

[0010] (2) The roll core is machined, surface cleaned and pre-reduced. The treated roll core is then assembled into an integrated electroslag casting device as an inner crystallizer. The assembly and debugging of the external water-cooled copper crystallizer, multi-electrode feeding system, molten metal quantitative supply system, rare earth activity online monitoring system, ultrasonic-electric pulse collaborative system and digital twin intelligent control system are completed. The device is equipped with a dual electroslag system with independently powered roll core heating chamber and metal refining chamber. Specifically, the roll core is machined to a surface roughness Ra≤6.3μm, ultrasonically cleaned with alcohol for 15~30min to remove surface oil, and coated with an aluminum-based protective agent (such as 60~70wt% aluminum powder). , The process involves preheating and pre-reducing the roll core at 400~500℃; when the treated roll core is assembled into the integrated electroslag melting and casting device as an inner crystallizer, the coaxiality is ensured to be ≤0.1mm / m and the annular gap is 20~100mm; the digital twin system dynamically calculates the amount of rare earth oxides and aluminum powder to be added based on real-time activity data, and adds them in small amounts and multiple times through a pulse-type automatic feeding system to avoid composition fluctuations and violent splashing caused by a large amount of material added at once. This technology realizes dynamic closed-loop control of the rare earth reduction process, and the fluctuation of rare earth content in steel along the length of the ingot is reduced from ±0.03wt% to ±0.005wt%, and the performance fluctuation of the roll along the entire length is controlled within ±2%.

[0011] (3) Add the electroslag to the two chambers in a ratio of 40~60:40~60 respectively, use graphite electrodes to ignite the arc, and complete the synchronous slag formation of the two chambers through staged electrical regulation, so that the molten slag temperature in the roller core heating chamber is stable at 1750~1800℃ and the molten slag temperature in the metal refining chamber is stable at 1800~1900℃; or use a three-stage electrical regulation to complete the synchronous slag formation of the two chambers: arc ignition stage (45~55V, 800~1200A, 5~10min), slag formation stage (38~45V, 1500~2500A, 15~30min), and slag stabilization stage (32~38V, 2000~3000A, 10~20min).

[0012] (4) The roller core is fed in two stages by 3 to 6 graphite electrodes that are evenly distributed in the circumference and the roller core rotates in the circumference at 0.5 to 5 r / min. If the electrode spacing is 10 to 30 mm and the insertion depth of the molten slag is 50 to 70%, the roller core is heated in two stages. Specifically, the two-stage gradient heating of the roller core surface is as follows: the rapid heating stage (35 to 40 V, 2500 to 3500 A, 10 to 20 s) raises the surface temperature to 1450 to 1550 °C; the heat preservation and shaping stage (30 to 35 V, 1500 to 2000 A, 5 to 15 s) maintains the surface melting state, accurately controls the melting depth to 0.5 to 3 mm, the radial temperature gradient is ≥300 °C / mm, and the core temperature is ≤400 °C.

[0013] (5) Electroslag remelting is performed in the metal refining chamber using a self-consumable electrode with matching composition. At the same time, the activity of La2O3 and Ce2O3 in the slag is monitored in real time by an in-situ electrochemical sensor. When the activity is lower than the set threshold, rare earth oxides and aluminum powder are added by a pulse automatic feeding system. The amount added each time is ≤0.5kg and the interval between additions is ≥5min. The binary basicity of the slag is maintained at ≥25. The reduction is maintained for 10~20min to make the rare earth oxide reduction rate ≥45%. The total rare earth content in the remelted liquid is 0.01~0.05wt%, and the fluctuation along the length of the ingot is ≤±0.005wt%.

[0014] (6) Rare earth modified metal liquid is continuously transported to the composite cavity through the sliding gate, and is synchronously composited with the molten layer on the surface of the roller core in an argon-sealed atmosphere.

[0015] (7) The composite roll billet is subjected to stress-relief annealing, rough machining, quenching and tempering heat treatment and fine machining to obtain the finished rare earth modified high-purity composite roll.

[0016] Preferably, step (1) further includes crushing, magnetically separating and removing impurities from the used waste electroslag, leaching with hydrochloric acid, precipitating with oxalic acid, and roasting at 600~800℃ to recover rare earth oxides. The recovered rare earth oxides are then added to new slag in a certain proportion to obtain recyclable rare earth modified pre-melted electroslag. The chemical composition of the pre-melted electroslag, by mass percentage, is: CaO 20~35%, , , , , The SiO2 content is ≤1%, and the binary basicity CaO / SiO2 is ≥25. The pre-melting is carried out at 1550~1650℃ for 2~4 hours under argon protection.

[0017] As a preferred embodiment, the specific process for rare earth oxide recycling in step (1) is as follows: the waste residue is crushed to ≤1mm, and metallic iron is removed by magnetic separation at a strength of 1000~1500Gs; leaching is performed with 2~3mol / L hydrochloric acid at 80~90℃ for 2~4h, with a solid-liquid ratio of 1:5~1:10; after filtration, oxalic acid solution is added to the leachate until the pH reaches 1.5~2.0 to precipitate rare earth ions; after washing and filtration, the precipitate is calcined at 600~800℃ for 2~3h to obtain mixed rare earth oxides with a purity ≥99%. By removing metallic iron particles from the slag through magnetic separation, leaching rare earth oxides with hydrochloric acid, precipitating rare earth ions with oxalic acid, and finally calcining, mixed rare earth oxides with a purity ≥99% are obtained. The total rare earth recovery rate is ≥85%, and the recovered rare earth oxides can be directly added to new slag for recycling, which not only reduces the cost of rare earth raw materials but also solves the environmental problem of fluorine-containing rare earth waste residue, achieving green production.

[0018] As a preferred embodiment, step (6) of the composite process specifically includes: ① controlling the initial acid-dissolved aluminum content in the molten metal liquid to 0.10~0.15wt% and rare earth content to 0.05~0.08wt%, utilizing the interfacial reaction between the molten layer on the roller core surface and the molten metal liquid in the working layer to generate an in-situ 2~5μm thick Al-RE-Fe face-centered cubic tough transition layer. This transition layer has a single face-centered cubic (FCC) structure with a dense atomic arrangement and multiple slip systems, exhibiting excellent plasticity and toughness, completely replacing the traditional brittle Fe-Al intermetallic compound. The interfacial fracture toughness is increased from the original 12MPa·m 1 / 2 Increased to 17 MPa·m 1 / 2 The above measures improve the interfacial bonding strength from 95% of the matrix strength to over 98%, completely solving the problem of brittle fracture at the interface; ② apply axial ultrasonic vibration of 20~40kHz and 500~2000W to the roller core; ③ apply 10~100Hz and 50~200A / cm between the outer crystallizer and the roller core. 2 A pulsed current of 10–100 μs and axial ultrasonic vibration of 20–40 kHz are transmitted through the roller core to the composite interface. The resulting cavitation and acoustic flow effects can break up the residual micro-oxide film at the interface, promote the interdiffusion of elements such as Fe, Al, and RE, and increase the thickness of the interface element diffusion layer from 10 μm to 20–50 μm. At the same time, ultrasonic vibration can refine the primary austenite grains in the molten pool and reduce dendrite segregation. A pulsed current of 10–100 Hz is applied to the solidification front, and the resulting Joule heating effect can homogenize the temperature field. The electromagnetic force effect can stir the molten pool, inhibit the preferential growth of austenite dendrites, and promote the formation of equiaxed grains. At the same time, the pulsed current can change the nucleation thermodynamics and kinetics of carbides, increase the nucleation rate of carbides, inhibit their growth, and ultimately control the secondary dendrite spacing to within 15 μm, refine the average carbide size to below 3 μm, and completely eliminate network carbides.

[0019] Preferably, the in-situ electrochemical sensor in step (5) uses a ZrO2-based solid electrolyte with an operating temperature of 1600~2000℃; the pulse feeding system can realize independent quantitative feeding of multiple components.

[0020] Preferably, the chemical composition of the Al-RE-Fe tough transition layer in step (6) is as follows, by atomic percentage: Fe 60~70%, Al 20~30%, La+Ce 5~10%, without Fe3Al or FeAl brittle intermetallic compounds; the amplitude of the ultrasonic vibration is 10~50μm.

[0021] Preferably, in step (6), the ratio of the molten metal supply rate to the ingot extraction rate is 1.05~1.15:1, and the ingot extraction rate is 0.8~2.5 mm / min; the inlet temperature of the cooling water in the external crystallizer is 10~20℃, the temperature difference between the inlet and outlet water is 8~15℃, and the cooling water flow rate is ≥2m / s; the entire composite process is protected by argon gas, and the flow rate is 5~15L / min.

[0022] As a preferred option, in step (7), the composite roll billet is subjected to stress-relief annealing at 600~700℃ for 8~12h, and after rough machining, it is subjected to quenching and tempering heat treatment according to the material of the working layer, and finally finished machining to the dimensions shown in the drawing.

[0023] As a preferred option, the heat treatment process in step (7) is determined according to the material: for high-speed steel, annealing at 800~850℃ for 4~8h, quenching and oil cooling at 1150~1200℃, tempering at 540~580℃ 3~5 times, each time for 2~4h; for high-chromium cast iron, annealing at 750~800℃ for 6~10h, quenching and air cooling at 950~1050℃, tempering at 200~300℃ 2~3 times, each time for 4~6h; for alloy tool steel, annealing at 780~820℃ for 4~6h, quenching and oil cooling at 980~1080℃, tempering at 180~220℃ 2~3 times, each time for 2~4h.

[0024] The present invention also provides an electroslag casting apparatus, including an apparatus frame, an external water-cooled copper crystallizer, a roller core clamping and rotating system, a multi-graphite electrode collaborative feeding unit, a consumable electrode remelting unit, a sliding nozzle type molten metal quantitative supply unit, a rare earth activity online monitoring unit, a pulse-type automatic feeding unit, an ultrasonic vibration unit, an electric pulse generation unit, and a digital twin intelligent control system.

[0025] The rare earth activity online monitoring unit includes a ZrO2-based solid electrolyte sensor, a high-temperature resistant signal cable, and a data acquisition and processing module. The sensor is inserted into the molten slag in the metal refining chamber and transmits the activity data of La2O3 and Ce2O3 in real time.

[0026] The pulse-type automatic feeding unit includes an independent rare earth oxide storage tank, an aluminum powder storage tank, and a servo screw feeding mechanism, which are linked with the digital twin system to realize pulse-type quantitative feeding; the ultrasonic vibration unit includes an ultrasonic transducer, an amplitude transformer, and a power amplifier, which are installed on the top of the roller core clamping system to apply axial ultrasonic vibration to the roller core.

[0027] The electrical pulse generating unit includes a high-frequency pulse power supply and a water-cooled electrode connection device, which are electrically connected to the outer crystallizer and the roller core clamping system, respectively, and apply an adjustable pulse current to the solidification region.

[0028] The digital twin intelligent control system is based on a multi-physics coupling model, which simulates and automatically adjusts process parameters in real time to achieve intelligent closed-loop control of the entire process.

[0029] The present invention also provides a rolling mill roll, comprising a roll core and a rare earth modified working layer, which are continuously metallurgically combined;

[0030] The rare earth modified working layer contains ≤12ppm oxygen, ≤8ppm sulfur, and 0.01~0.05wt% total rare earth elements; the carbides are uniformly dispersed in granular form with an average size ≤3μm.

[0031] Preferably, the roller core material is any one of 45# steel, 40Cr, and 42CrMo, and the rare earth modified working layer material is any one of M2 high-speed steel, W6Mo5Cr4V2 high-speed steel, high-chromium cast iron, Cr12MoV alloy tool steel, and H13 hot work die steel.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. By using in-situ electrochemical activity monitoring and pulse feeding technology, closed-loop control of the rare earth reduction process was achieved. The rare earth content in the remelting liquid fluctuated along the ingot length from ±0.03wt% to ±0.005wt%, and the performance fluctuation of the rolls along the entire length was controlled within ±2%. This completely solved the industry problem of poor consistency in batch production and achieved a revolutionary improvement in the precision of rare earth control in electroslag remelting.

[0034] 2. The in-situ generated Al-RE-Fe tough transition layer completely eliminates the brittle phase at the interface. Combined with ultrasonic-assisted element diffusion, the interfacial bonding strength is increased from 95% to over 98%, and the interfacial fracture toughness is increased by over 40%, completely eliminating interfacial fracture failure under heavy load conditions.

[0035] 3. The ultrasonic-electric pulse synergistic solidification technology controls the secondary dendrite spacing to within 15μm, refines the average size of carbides to below 3μm, completely eliminates network and fishbone-like carbides, and significantly improves the impact toughness and wear resistance of the rolls.

[0036] 4. Significant green, low-carbon, and resource recycling benefits: The closed-loop recycling technology for rare earth slag achieves efficient recycling of rare earth resources, with a recovery rate of ≥85%, reducing raw material costs by more than 30% and reducing waste emissions by more than 80%. Product cleanliness and reliability are greatly improved. The synergistic effect of electroslag refining and rare earth inclusion modification results in an oxygen content of ≤12ppm, a sulfur content of ≤8ppm, and an inclusion grade of ≤0.3 in the working layer. This results in rolls with a service life more than twice that of traditional processes, reaching an internationally leading level.

[0037] 5. The intelligent device integrating the digital twin system realizes the automatic simulation, prediction and control of the entire process, increasing the yield from 95% to over 99%, improving production efficiency by 20%, and is suitable for the preparation of high-end rolls of all specifications from φ50 to φ800mm. Detailed Implementation

[0038] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0039] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein. The reagents used herein may be commercially available related products, and performance testing standards refer to industry or national standards.

[0040] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The term “and / or” as used herein includes all or any units and all combinations of one or more associated listed items.

[0041] Example 1

[0042] A rare earth modified M2 high-speed steel composite cold rolling work roll, with a roll core material of 42CrMo and a working layer material of W6Mo5Cr4V2 high-speed steel, the working layer thickness being 15mm.

[0043] The preparation method is as follows: (1) Preparation of pre-melted electroslag: Weigh according to the mass percentage , , , , , , (1) After mixing, the medium frequency induction furnace is pre-melted at 1600℃ for 3 hours, water quenched and granulated, and vacuum dried; (2) Roller core pretreatment: machined to Ra≤6.3μm, ultrasonically cleaned with alcohol for 20 minutes, coated with aluminum-based protective agent, and preheated and pre-reduced at 450℃; (3) Double electroslag slag making: pre-melted electroslag is divided into two chambers in a 50:50 ratio, and slag is made in three stages. The temperature of the roller core heating chamber is 1780℃, and the temperature of the metal refining chamber is 1850℃; (4) Roller core gradient heating: 4 graphite electrodes are fed together, the roller core speed is 2r / min, and the rapid temperature rise is 38V / 3000A. / 15s, heat preservation and shaping 32V / 1800A / 10s, melting depth 1.2mm; (5) Electroslag refining and rare earth control: self-consumable electrode electroslag remelting, ZrO2 sensor real-time monitoring of rare earth activity, pulse addition of rare earth oxides and aluminum powder, total rare earth content in steel 0.030wt%; (6) Composite solidification: metal liquid supply / ingot extraction speed ratio is 1.1:1, ingot extraction speed is 1.5mm / min, Al-RE-Fe transition layer is generated in situ, ultrasonic 30kHz / 1000W, electric pulse 50Hz / 100A / cm is applied. 2 (7) Post-treatment: stress relief annealing at 650℃ for 10h, annealing at 820℃ for 6h, quenching and oil cooling at 1180℃, tempering at 560℃ 4 times, 3h each time, and finishing to the finished product.

[0044] The performance of the roll was tested, and the results are as follows: interfacial bonding strength is 97.8% of the matrix strength, secondary dendrite spacing is 14 μm, average carbide size is 2.8 μm, and impact toughness is 15.8 J / cm². 2 Flexural strength 1880MPa, hardness uniformity across the same cross section ±0.4HRC, hardness fluctuation over the entire length ±1.8%.

[0045] Example 2

[0046] A rare earth-modified high-chromium cast iron composite hot-rolled support roll is disclosed. The roll core is made of 45# steel, and the working layer is made of Cr20 high-chromium cast iron with a thickness of 50 mm. The preparation method is the same as in Example 1 except for the following: In the pre-melting electroslag preparation, recycled rare earth oxides (recovery rate 86%) are added to the new slag, with a total rare earth oxide content of 8%; the melting depth in the roll core gradient heating is 2.5 mm; the total rare earth content in the remelted liquid during electroslag refining and controlled dilution is 0.025 wt%; the ingot drawing speed is 1.0 mm / min; the post-treatment is stress-relief annealing at 620℃ for 12 h, annealing at 780℃ for 8 h, quenching and air cooling at 1000℃, tempering at 250℃ three times for 5 h each time, and finishing to the finished product.

[0047] The performance of the roll was tested, and the results are as follows: interfacial bonding strength 98.2% of matrix strength, secondary dendrite spacing 13 μm, average carbide size 2.8 μm, and impact toughness 16.2 J / cm². 2It has a bending strength of 1900MPa, a hardness uniformity of ±0.5HRC across the same cross section, a hardness fluctuation of ±1.7% over the entire length, and reduces the cost of rare earth raw materials by 32%.

[0048] Example 3

[0049] A rare earth-modified Cr12MoV composite leveling roll has a core material of 40Cr and a working layer material of Cr12MoV alloy tool steel with a working layer thickness of 10mm. The preparation method is the same as in Example 1 except for the following: the core is heated to a gradient melting depth of 0.8mm; the total rare earth content in the remelted liquid is 0.022wt%, fluctuating by ±0.004wt% along the ingot length; the ingot drawing speed is 2.0mm / min; the post-treatment is stress-relief annealing at 630℃ for 9h, annealing at 800℃ for 5h, quenching and oil cooling at 1030℃, tempering twice at 200℃ for 3h each time, and finishing to the finished product.

[0050] The performance of the roll was tested, and the results are as follows: interfacial bonding strength 98.0% of matrix strength, secondary dendrite spacing 13 μm, average carbide size 2.6 μm, and impact toughness 16.0 J / cm². 2 Flexural strength 1890MPa, hardness uniformity across the same cross section ±0.3HRC, hardness fluctuation over the entire length ±1.5%.

[0051] Example 4

[0052] A rare earth-modified M2 high-speed steel composite roll, wherein the slag system adopts a mass percentage of... , , , , , , The binary alkalinity is 25. The remaining preparation methods and process parameters are the same as in Example 1.

[0053] The roll was tested, and the performance results are as follows: interfacial bonding strength 97.5% of matrix strength, secondary dendrite spacing 15 μm, average carbide size 3.0 μm, and impact toughness 15.5 J / cm². 2 Flexural strength 1860MPa.

[0054] Example 5

[0055] A rare earth-modified high-chromium cast iron composite roll, wherein the slag system adopts a slag composition based on a mass percentage of... , , , , , , The binary alkalinity is 35. The remaining preparation methods and process parameters are the same as in Example 2.

[0056] The roll was tested, and the performance results are as follows: interfacial bonding strength 98.1% of matrix strength, secondary dendrite spacing 12 μm, average carbide size 2.7 μm, and impact toughness 16.3 J / cm². 2 Flexural strength 1910MPa.

[0057] Example 6

[0058] A rare earth-modified Cr12MoV composite roll is prepared with a core core gradient heating melting depth of 3 mm, a core temperature of 400℃, and a radial temperature gradient of 300℃ / mm. The remaining preparation methods and process parameters are the same as in Example 3.

[0059] The performance of the roll was tested, and the results are as follows: interfacial bonding strength 97.6% of matrix strength, secondary dendrite spacing 14 μm, average carbide size 2.9 μm, and impact toughness 15.7 J / cm². 2 Flexural strength 1870MPa.

[0060] Example 7

[0061] An ultrasonic-electric pulse synergistic strengthening composite roll for M2 high-speed steel, based on Example 1, optimizes the ultrasonic-electric pulse parameters: ultrasonic frequency 30kHz, power 1000W, amplitude 20μm; pulse current frequency 50Hz, current density 100A / cm². 2 The pulse width is 50 μs and the duty cycle is 30%. All other process parameters are exactly the same as in Example 1.

[0062] The roll was tested, and the performance results are as follows: interfacial bonding strength 98.5% of matrix strength, secondary dendrite spacing 12 μm, average carbide size 2.5 μm, oxygen content in the working layer 10 ppm, sulfur content 7 ppm, and impact toughness 16.5 J / cm². 2 The bending strength is 1920MPa, the hardness uniformity of the same cross section is ±0.4HRC, the hardness fluctuation along the whole length is ±1.5%, the rare earth fluctuation along the ingot length is ±0.004wt%, the wear resistance relative value is 235, and the thermal fatigue life is not less than 12000 cycles.

[0063] Example 8

[0064] A method for preparing high-chromium cast iron composite rolls through rare earth slag recycling is described. Based on Example 2, recovered rare earth oxides (recovery rate 86%) are added to new slag in a specific ratio, while the total content of rare earth oxides remains unchanged at 8%. All other process parameters are identical to those in Example 2.

[0065] The roll was tested, and the performance results are as follows: interfacial bonding strength 98.2% of matrix strength, secondary dendrite spacing 13 μm, average carbide size 2.8 μm, oxygen content in the working layer 11 ppm, sulfur content 8 ppm, and impact toughness 16.2 J / cm². 2 The steel has a bending strength of 1900MPa, a hardness uniformity of ±0.5HRC along the same cross section, a hardness fluctuation of ±1.7% along the entire length, a rare earth fluctuation of ±0.005wt% along the ingot length, a wear resistance relative value of 230, a thermal fatigue life of not less than 11800 cycles, a total rare earth content of 0.024wt% in the steel, a 32% reduction in rare earth raw material costs, and a reduction of more than 80% in waste slag emissions.

[0066] Comparative Example 1

[0067] The traditional centrifugal casting of M2 integral rolls involves no electroslag refining or rare earth modification, and the remaining process parameters are the same as in Example 1.

[0068] The roll was tested, and the performance results are as follows: oxygen content 62 ppm, sulfur content 35 ppm, inclusion grade 3.5, secondary dendrite spacing 55 μm, average carbide size 22 μm, presence of a large number of network carbides, and impact toughness 8.2 J / cm. 2 The bending strength is 1250MPa, and the service life is significantly reduced compared to the example.

[0069] The roll was tested, and its performance results are as follows: interfacial bonding strength 75% of matrix strength, secondary dendrite spacing 55 μm, average carbide size 22 μm, oxygen content in the working layer 62 ppm, sulfur content 35 ppm, inclusion grade 3.5, with a large number of network carbides present, and impact toughness 8.2 J / cm. 2 It has a flexural strength of 1250MPa, a relative wear resistance value of 100, and a thermal fatigue life of only 3000 cycles.

[0070] Comparative Example 2

[0071] Traditional electroslag welded composite rolls, without rare earth modification or dual electroslag system, with other process parameters the same as in Example 1.

[0072] The performance of the roll was tested, and the results are as follows: interfacial bonding strength 75% of matrix strength, interfacial oxide inclusions present, rare earth burn-off >90%, and impact toughness 10.5 J / cm. 2 The bending strength is 1420MPa, and the service life is significantly reduced compared to the example.

[0073] Comparative Example 3

[0074] The low-alkalinity slag-based composite roll has a binary basicity of 20 in the molten slag, and the other process parameters are the same as in Example 1.

[0075] The performance of the roll was tested, and the results are as follows: rare earth oxide reduction rate 28%, rare earth yield 22%, fluctuation along the ingot length ±0.035wt%, interfacial bonding strength 90% of matrix strength, and impact toughness 12.8 J / cm. 2 .

[0076] Comparative Example 4

[0077] The composite roll without rare earth modification does not contain rare earth oxides in the pre-melted electroslag, and the other process parameters are the same as in Example 1.

[0078] The performance of the roll was tested, and the results are as follows: the inclusions are angular, the secondary dendrite spacing is 28 μm, the average carbide size is 12 μm, and there are localized network carbides; the impact toughness is 11.2 J / cm. 2 Flexural strength 1560MPa.

[0079] Comparative Example 5

[0080] The single-electrode heated composite roll uses one graphite electrode to heat the roll core, and the other process parameters are the same as in Example 1.

[0081] The performance of the roll was tested, and the results are as follows: circumferential temperature unevenness of the roll core >100℃, localized lack of fusion at the interface, interfacial bonding strength 82% of matrix strength, and impact toughness 10.8 J / cm². 2 .

[0082] Comparative Example 6

[0083] The single-stage heating composite roll eliminates the heat preservation and shaping stage, and directly and rapidly heats up to the surface melting point. The remaining process parameters are the same as in Example 1.

[0084] The performance of the roll was tested, and the results are as follows: core temperature 620℃, coarse grains, and impact toughness 11.5 J / cm. 2 Flexural strength 1620MPa.

[0085] Comparative Example 7

[0086] Deep molten pool composite roll, with a metal molten pool depth of 100mm, and other process parameters are the same as in Example 1.

[0087] The performance of the roll was tested, and the results are as follows: secondary dendrite spacing 35 μm, severe carbide segregation, and impact toughness 12.1 J / cm. 2 Flexural strength 1680MPa.

[0088] Comparative Example 8

[0089] The composite rolls are manufactured in a stepwise process, with electroslag refining and interface composite processes carried out in separate steps. The interface is exposed to air, and the remaining process parameters are the same as in Example 1.

[0090] The performance of the roll was tested, and the results are as follows: Oxide inclusions are present at the interface; the interfacial bonding strength is 85% of the matrix strength; and the impact toughness is 11.8 J / cm². 2 Interface cracking occurred after 1500 thermal fatigue cycles.

[0091] Comparative Example 9

[0092] The non-ultrasonic assisted composite roll, compared with Example 7, does not apply ultrasonic vibration, but all other process parameters are exactly the same.

[0093] The roll was tested, and the performance results are as follows: the thickness of the interfacial element diffusion layer is 8 μm, the interfacial bonding strength is 92% of the matrix strength, a small number of interfacial microcracks exist, and the impact toughness is 13.2 J / cm. 2 .

[0094] Comparative Example 10

[0095] The non-electric pulse assisted composite roll is identical to Example 7, except that no pulse current is applied and all other process parameters are exactly the same.

[0096] The performance of the roll was tested, and the results are as follows: secondary dendrite spacing 22 μm, average carbide size 6 μm, local network carbide presence, and impact toughness 11.8 J / cm. 2 Compared to Example 7, the wear resistance decreased by 28% and by 18%.

[0097] Comparative Example 11

[0098] The composite roll without an interface transition layer is controlled in the same way as in Example 7, except that the rare earth content is not controlled in the initial stage of composite, while the other process parameters are exactly the same.

[0099] The performance of the roll was tested, and the results are as follows: interfacial bonding strength 85% of matrix strength, secondary dendrite spacing 18 μm, average carbide size 8 μm, formation of a brittle Fe3Al phase with a thickness of approximately 3 μm at the interface, and interfacial fracture toughness 9.5 MPa·m. 1 / 2 The working layer contains 14 ppm oxygen, 9 ppm sulfur, and rare earth elements fluctuate by ±0.03 wt% along the ingot length. The impact toughness is 9.5 J / cm. 2 The relative wear resistance value is 85, and interface cracking occurs after 2000 cycles of thermal fatigue testing.

[0100] The test results above show that the embodiments of the present invention solve the defects in the prior art, such as lack of dynamic control of rare earth elements, formation of brittle phases at the interface, random precipitation of carbides, and waste of rare earth slag. All performance indicators far exceed those of the comparative examples. In particular, Example 7 achieves extreme microstructure refinement through ultrasonic-electric pulse synergistic enhancement, and further improves wear resistance and thermal fatigue life compared with the basic Example 1. Example 8 demonstrates the feasibility of rare earth slag recycling technology, which significantly reduces raw material costs and environmental pressure while ensuring product performance remains unchanged.

[0101] The preferred embodiments of the present invention have been described in detail above, and are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for manufacturing a rolling mill roll, characterized in that, Includes the following steps: (1) Weigh each raw material according to the component ratio, mix them evenly, place them in a medium frequency induction furnace for pre-melting, quench them in water to form slag particles, and dry and sieve them to obtain electroslag. (2) The roll core is machined, surface cleaned and pre-reduced. The treated roll core is then assembled into an integrated electroslag casting device as an inner crystallizer. The assembly and debugging of the external water-cooled copper crystallizer, multi-electrode feeding system, molten metal quantitative supply system, rare earth activity online monitoring system, ultrasonic-electric pulse collaborative system and digital twin intelligent control system are completed. The device is equipped with a dual electroslag system with independently powered roll core heating chamber and metal refining chamber. (3) Add the electroslag to the two chambers in a ratio of 40~60:40~60 respectively, use graphite electrodes to ignite the arc, and complete the synchronous slag making of the two chambers through staged electrical regulation, so that the molten slag temperature of the roller core heating chamber is stable at 1750~1800℃ and the molten slag temperature of the metal refining chamber is stable at 1800~1900℃. (4) The roller core is subjected to two-stage gradient heating by feeding together with 3 to 6 circumferentially evenly distributed graphite electrodes and rotating circumferentially at 0.5 to 5 r / min. (5) Electroslag remelting is performed in the metal refining chamber using a self-consumable electrode with matching composition. At the same time, the activity of La2O3 and Ce2O3 in the slag is monitored in real time by an in-situ electrochemical sensor. When the activity is lower than the set threshold, rare earth oxides and aluminum powder are added by a pulse automatic feeding system. The amount added each time is ≤0.5kg and the interval between additions is ≥5min. The binary basicity of the slag is maintained at ≥25. The reduction is maintained for 10~20min to make the rare earth oxide reduction rate ≥45%. The total rare earth content in the remelted liquid is 0.01~0.05wt%, and the fluctuation along the length of the ingot is ≤±0.005wt%. (6) Rare earth modified metal liquid is continuously transported to the composite cavity through the sliding gate, and is synchronously composited with the molten layer on the surface of the roller core in an argon-sealed atmosphere. (7) The composite roll billet is subjected to stress-relief annealing, rough machining, quenching, tempering heat treatment, and fine machining to obtain the finished roll.

2. The method for preparing a rolling mill roll according to claim 1, characterized in that, Step (1) also includes crushing, magnetically separating and removing impurities from the used waste electroslag, leaching with hydrochloric acid, precipitating with oxalic acid, and roasting at 600~800℃ to recover rare earth oxides. The recovered rare earth oxides are then added to the new slag in a certain proportion to obtain recyclable rare earth modified pre-melted electroslag. The chemical composition of the pre-melted electroslag is as follows by mass percentage: CaO 20~35%, Al2O3 15~25%, CaF2 30~45%, La2O3 2~8%, Ce2O3 1~5%, MgO 1~4%, SiO2≤1%, wherein the binary basicity CaO / SiO2≥25.

3. The method for preparing a rolling mill roll according to claim 1, characterized in that, The two-stage gradient heating in step (4) is as follows: a rapid heating stage of 10~20s, where the surface temperature is raised to 1450~1550℃ at 2500~3500A; and a heat preservation and shaping stage of 5~15s, where the surface is kept in a molten state at 1500~2000A, the melting depth is controlled at 0.5~3mm, the radial temperature gradient is ≥300℃ / mm, and the core temperature is ≤400℃.

4. The method for preparing a rolling mill roll according to claim 1, characterized in that, Step (6) of the composite process specifically includes: ① controlling the initial acid dissolution of aluminum in the liquid metal to 0.10~0.15wt% and rare earth to 0.05~0.08wt% to generate a 2~5μm thick Al-RE-Fe face-centered cubic tough transition layer in situ; ② applying axial ultrasonic vibration of 20~40kHz and 500~2000W to the roller core; ③ applying 10~100Hz and 50~200A / cm between the outer crystallizer and the roller core. 2 A pulse current of 10~100μs.

5. The method for preparing a rolling mill roll according to claim 1, characterized in that, The in-situ electrochemical sensor mentioned in step (5) uses a ZrO2-based solid electrolyte and operates at a temperature of 1600~2000℃; the pulse-type automatic feeding system can realize independent quantitative feeding of multiple components.

6. The method for preparing a rolling mill roll according to claim 4, characterized in that, The chemical composition of the Al-RE-Fe tough transition layer in step (6) is as follows, by atomic percentage: Fe 60~70%, Al 20~30%, La+Ce 5~10%, without Fe3Al or FeAl brittle intermetallic compounds; the amplitude of the ultrasonic vibration is 10~50μm.

7. The method for preparing a rolling mill roll according to claim 1, characterized in that, In step (6), the ratio of the molten metal supply rate to the ingot extraction rate is 1.05~1.15:1, and the ingot extraction rate is 0.8~2.5 mm / min; the inlet temperature of the cooling water in the external crystallizer is 10~20℃, the temperature difference between the inlet and outlet water is 8~15℃, and the cooling water flow rate is ≥2m / s; the entire composite process is protected by argon gas, and the flow rate is 5~15L / min.

8. An electroslag casting apparatus for the preparation method according to any one of claims 1 to 7, characterized in that, It includes a device frame, an external water-cooled copper crystallizer, a roller core clamping and rotating system, a multi-graphite electrode collaborative feeding unit, a consumable electrode remelting unit, a sliding nozzle type molten metal quantitative supply unit, a rare earth activity online monitoring unit, a pulse-type automatic feeding unit, an ultrasonic vibration unit, an electrical pulse generation unit, and a digital twin intelligent control system. The rare earth activity online monitoring unit includes a ZrO2-based solid electrolyte sensor, a high-temperature resistant signal cable, and a data acquisition and processing module. The sensor is inserted into the molten slag in the metal refining chamber and transmits the activity data of La2O3 and Ce2O3 in real time. The pulse-type automatic feeding unit includes an independent rare earth oxide storage tank, an aluminum powder storage tank, and a servo screw feeding mechanism, which are linked with the digital twin system to realize pulse-type quantitative feeding; the ultrasonic vibration unit includes an ultrasonic transducer, an amplitude transformer, and a power amplifier, which are installed on the top of the roller core clamping system to apply axial ultrasonic vibration to the roller core. The electrical pulse generating unit includes a high-frequency pulse power supply and a water-cooled electrode connection device, which are electrically connected to the outer crystallizer and the roller core clamping system, respectively, and apply an adjustable pulse current to the solidification region. The digital twin intelligent control system is based on a multi-physics coupling model, which simulates and automatically adjusts process parameters in real time to achieve intelligent closed-loop control of the entire process.

9. A roll prepared by the preparation method according to any one of claims 1 to 7, characterized in that, It includes a roller core and a rare earth modified working layer, which are combined in a continuous metallurgical manner; The rare earth modified working layer contains ≤12ppm oxygen, ≤8ppm sulfur, and 0.01~0.05wt% total rare earth elements; the carbides are uniformly dispersed in granular form with an average size ≤3μm.

10. The roll according to claim 9, characterized in that, The roller core is made of any one of 45# steel, 40Cr, and 42CrMo, and the rare earth modified working layer is made of any one of M2 high-speed steel, W6Mo5Cr4V2 high-speed steel, high-chromium cast iron, Cr12MoV alloy tool steel, and H13 hot work die steel.