A method for producing thick gauge abrasion resistant steel hot rolled coils on a conventional hot mill line

Abstract

The embodiment of the application provides a production method for producing a thick-specification wear-resistant steel hot-rolled steel coil by a conventional hot continuous rolling line, comprising the following steps: obtaining a wear-resistant steel slab, rough rolling the slab after heating for 6-8 passes to obtain an intermediate slab; performing finish rolling on the intermediate slab to obtain a steel plate to be coiled, wherein the thickness of the steel plate to be coiled is 25-30 mm; performing laminar cooling on the steel plate to be coiled to 670-690 DEG C to perform coiling, thereby obtaining a thick-specification wear-resistant steel hot-rolled steel coil, wherein the pinch roll pressure in the coiling process is 250 KN-290 KN, and the coiler pressure is 490 KN-510 KN. Through optimization of rolling process parameters, equipment functions and cooling control, the embodiment of the application realizes stable production of thick-specification wear-resistant steel by the conventional hot continuous rolling line, and improves product quality and production efficiency.

Description

Technical Field

[0001] This application relates to the field of hot-rolled steel coil production technology, specifically to a production method for producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot continuous rolling line. Background Technology

[0002] Traditional hot strip mills are mainly used to produce medium and thin plates (thickness ≤ 25mm), while the production of thick wear-resistant steel coils (thickness ≥ 25mm) usually relies on medium and heavy plate mills or special rolling processes, resulting in low production efficiency, high energy consumption, and large equipment investment. Existing technologies typically require multiple rolling passes or offline heat treatment to produce thick wear-resistant steel, leading to high energy consumption and low efficiency. Therefore, there is an urgent need for a highly efficient process to directly produce thick wear-resistant steel hot-rolled coils using conventional hot strip mills. Summary of the Invention

[0003] This application provides a production method for producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot rolling line. By optimizing rolling process parameters and cooling regime, it overcomes equipment limitations and achieves efficient and low-cost production.

[0004] This application discloses a method for producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot continuous rolling line. The method includes: a roughing step, obtaining a slab of wear-resistant steel, heating the slab and performing 6-8 passes of roughing to obtain an intermediate slab with a thickness of 58-60 mm; and a finishing step, performing a stand-off treatment on the finishing mill and adjusting the stand load distribution, ensuring the water ratio between the upper and lower sections of the finishing mill's roll gap is within a preset range, and then finishing-rolling the intermediate slab to obtain a thick-gauge steel plate with a thickness of [missing information]. 25~30mm; Cooling step: The thick steel plate is cooled to 670~690℃ in laminar flow to obtain the steel plate to be rolled; Coiling step: The key load-bearing components of the coiler are subjected to force verification calculations, and the coiling process parameters are optimized based on the verification calculation results. The full-process pressing function of the auxiliary coiling roller is activated to coil the steel plate to be rolled, thereby obtaining the thick wear-resistant hot-rolled steel coil; Among them, the verification of the key load-bearing components of the coiler includes the verification of the pinch roller pressure, the verification of the overload coefficient of the pinch roller main motor, and the verification of the load torque of the mandrel motor.

[0005] According to an embodiment of this application, the winding process parameters in the winding step include: pinch roller pressure 250~290KN, winding tension 13~15MPa, and auxiliary winding roller pressure 490~510KN.

[0006] According to the embodiments of this application, the overload coefficient of the pinch roller main motor is controlled at 2.70~2.80, and the overload coefficient of the mandrel main motor is controlled at 3.00~3.10.

[0007] According to an embodiment of this application, the finishing rolling step includes: removing one of the F2 to F4 stands and one of the F5 to F7 stands, and adjusting the water spraying at the roll gap of the working stand so that the water spraying volume at the lower end is greater than that at the upper end.

[0008] According to an embodiment of this application, in the finishing rolling step, F4 and F6 stands are removed, and the water distribution ratio between the upper and lower spray water in the roll gap of F1-F4 stands is optimized so that the lower spray water volume is greater than the upper spray water volume.

[0009] According to an embodiment of this application, in the rough rolling step, the slab is heated to a temperature of 1200°C to 1260°C, and the number of rough rolling passes is 7.

[0010] According to an embodiment of this application, the pinch roller pressure is checked using the following formula: In the formula: The pinch roller pressure is in kN. denoted as b, which is the hot yield strength of the steel plate to be rolled, in MPa; b is the width of the steel plate to be rolled, in mm; h is the thickness of the steel plate to be rolled; and θ is the offset angle of the upper and lower clamping rollers.

[0011] In some embodiments, the overload coefficient of the pinch roller main motor is checked using the following calculation formula: In the formula: The overload coefficient of the main motor of the pinch roller; Main motor transmission efficiency; The reduction ratio of the main motor; The maximum load torque of the upper and lower pinch roller motors is N. m; The rated output torque of the pinch roller motor is N. m.

[0012] In some embodiments, the mandrel motor verification includes calculating the tension torque and bending torque of the steel plate to be coiled. The tension torque calculation formula is as follows: In the formula: The tension torque of the steel sheet to be rolled is N. m; Width of the steel plate to be rolled, in mm; The thickness of the steel plate to be rolled; —Maximum outer diameter of the steel coil, mm; —Unit tension of the steel sheet to be rolled, N mm-2; In the formula: The bending moment of the steel sheet to be rolled, N m; This is the bending moment limit value; This is the maximum diameter for winding the steel sheet to be wound; The Young's modulus of the steel sheet to be rolled; Hot yield strength of the steel sheet to be rolled, MPa The formula for calculating the overload factor of a spindle motor is: ; ; ; in, The maximum load torque of the spindle motor is N. m; The bending moment of the steel sheet to be rolled, N m, The tension torque of the steel sheet to be rolled is N. m; 2 represents the reduction ratio of the spindle motor; The rated output torque of the spindle motor is N. m; Rated power of the motor, in kW; The rated speed of the motor is r / min; This is the overload coefficient of the spindle motor; The rated output torque of the spindle motor is N. m.

[0013] According to an embodiment of this application, the conventional hot strip mill line is a 2250 hot strip mill line.

[0014] Compared with the prior art, the present invention has at least the following beneficial effects: This application achieves stable production of thick-gauge wear-resistant steel on conventional hot strip mill lines by optimizing rolling process parameters, equipment functions, and cooling control, thereby improving product quality and production efficiency. Detailed Implementation

[0015] The embodiments of this application will be described in further detail below with reference to the examples. The detailed description of the following embodiments is used to illustrate the principles of this application, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0016] In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. "Vertical" does not require strict verticality, but may include permissible errors. "Parallel" does not require strict parallelism, but may include permissible errors.

[0017] Currently, the production of thick-gauge wear-resistant steel coils typically relies on medium-thick plate mills or special rolling processes, which suffer from low production efficiency, high energy consumption, and large equipment investment. Conventional hot-rolled lines are mainly used to produce thin-gauge hot-rolled steel coils, and their direct application to the production of thick-gauge wear-resistant steel faces technical bottlenecks such as coiling difficulties. Existing technologies lack optimized production processes for thick-gauge wear-resistant steel hot-rolled coils specifically designed for conventional hot-rolled lines, thus limiting the large-scale production of this type of product.

[0018] In view of this, the inventors of this application, through extensive experimental research, provide a production method for producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot rolling line, for producing thick-gauge wear-resistant hot-rolled steel coils.

[0019] This application provides a method for producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot continuous rolling line, comprising: a roughing step, obtaining a slab of wear-resistant steel, heating the slab and then performing 6-8 passes of roughing to obtain an intermediate slab with a thickness of 58-60 mm; and a finishing step, performing stand-off processing on the finishing mill and adjusting the stand load distribution, ensuring the water ratio between the upper and lower water levels in the roll gap of the finishing mill is within a preset range, and then finishing-rolling the intermediate slab to obtain a thick-gauge steel plate with a thickness of 25 mm. ~30mm; Cooling step: The thick-gauge steel plate is laminar cooled to 670~690℃ to obtain the steel plate to be rolled; Coiling step: Force verification calculations are performed on the key load-bearing components of the coiler. Based on the verification calculation results, the coiling process parameters are optimized, the full-process pressing function of the auxiliary coiling roller is activated, and the steel plate to be rolled is coiled to obtain the thick-gauge wear-resistant hot-rolled steel coil; Among them, the verification of the key load-bearing components of the coiler includes verification of the pinch roller pressure, verification of the overload coefficient of the pinch roller main motor, and verification of the load torque of the mandrel motor.

[0020] This application embodiment relies on a 2250mm conventional hot rolling mill production line for production. This production line is originally designed to produce medium and thin hot-rolled steel coils. This application embodiment overcomes the thickness production bottleneck of conventional hot rolling mill production lines by optimizing the rolling process and matching the equipment's load-bearing capacity, and stably produces 25~30mm thick wear-resistant hot-rolled steel coils, replacing the traditional medium and heavy plate production line production mode, simplifying the production process and reducing production costs. The specific production method includes the following production steps: Rough rolling process: Obtain wear-resistant steel slabs using continuous casting to ensure a dense internal structure free of internal cracks, porosity, and other metallurgical defects. The slabs are then fed into a heating furnace for uniform heating to ensure consistent temperature, eliminate internal segregation, improve high-temperature plasticity, reduce rolling deformation resistance, and prevent cracking defects during the rolling of thicker slabs. After heating and exiting the furnace, the slabs are fed into a roughing mill for multi-pass reciprocating rolling. The number of roughing passes is controlled to 6-8, with a 7-pass rolling system preferred. By gradually compressing the slab thickness through multiple passes with small reductions, the internal grain structure of the metal is improved, ultimately yielding an intermediate slab with a thickness of 58-60 mm. The preferred thickness of the intermediate slab is 58.0-59.0 mm, which matches the reduction capacity of the subsequent finishing mill, avoiding rolling slippage and edge tearing caused by excessive reduction in a single pass, and providing stable slab conditions for finishing rolling.

[0021] Finishing Rolling Step: The prepared high-temperature intermediate billet is fed into the finishing mill for finishing rolling. To address the production challenges of high deformation resistance and high single-stand rolling load for thick steel plates, the finishing mill stands are configured to be partially shut down to accommodate the thick-plate rolling conditions. Simultaneously, the load distribution of each stand is adjusted based on the rolling load distribution pattern to prevent overload damage. During finishing rolling, the water-to-roll ratio of the sprayed water at the roll gap of the front-end finishing mill stands is controlled within a preset range to balance the surface temperature of the steel plate, suppress warping and surface defects, and ensure a stable and continuous rolling process. After finishing rolling, the intermediate billet yields a thick steel plate with a thickness of 25-30 mm.

[0022] In this embodiment, the thickness of the steel plate to be coiled is 25-30 mm. For wear-resistant steel, a certain thickness is fundamental to ensuring its strength and wear resistance. A thickness of 25-30 mm allows the steel plate to have sufficient material volume and mass to meet the mechanical performance requirements of wear-resistant steel in practical applications. Thicker steel plates can withstand greater external forces and friction, maintain better stability in abrasive environments, and extend service life.

[0023] An appropriate thickness helps to form a uniform and dense microstructure during subsequent cooling. Within this thickness range, the grain growth and phase transformation processes inside the steel plate can be better controlled, which is conducive to obtaining an ideal metallographic structure, such as grain refinement, thereby improving the overall performance of the steel plate, including strength, toughness, and wear resistance.

[0024] Cooling Step: The rolled thick steel plate is conveyed to a laminar flow cooling device for uniform cooling. The cooling method and rate are reasonably controlled to cool the steel plate to 670~690℃, resulting in a steel plate with uniform temperature and stable microstructure. This temperature range balances the rigidity and plasticity of the steel plate, weakens the springback characteristics of thick steel plates, and avoids defects such as cracking and deformation during coiling, providing good temperature conditions for subsequent coiling processes. In this embodiment, the steel plate to be coiled is laminarly cooled to 670~690℃ before coiling. During cooling in this temperature range, the austenite structure in the steel gradually transforms into ferrite. Ferrite has a body-centered cubic lattice structure, which, compared to the face-centered cubic lattice structure of austenite, has relatively fewer slip systems. This makes it more prone to plastic deformation under stress, thus reducing the material's yield strength. Simultaneously, within the temperature range of 670-690℃, carbon in steel combines with some alloying elements (such as chromium, molybdenum, and vanadium) to form carbides, which precipitate from the solid solution. The precipitation of these carbides consumes alloying elements and carbon in the solid solution, weakening the solid solution strengthening effect and reducing the strength of the steel sheet to be coiled, especially the yield strength, which is beneficial for the coiling operation.

[0025] In this embodiment, the steel plate to be coiled is cooled to 670~690℃ in a laminar flow before coiling. With the corresponding pinch roll and auxiliary coiling roll parameter settings, a conventional hot continuous rolling line can produce wear-resistant hot-rolled steel coils with a thickness of 25~30mm.

[0026] Coiling Steps: Thick steel plates are inherently thick and rigid, making bending and forming difficult. Conventional coiling processes are prone to forming defects such as slippage, loose coiling, and tapering, and are highly susceptible to overload damage to the load-bearing components of the coiling machine. Therefore, before the coiling operation, force verification calculations are performed on the key load-bearing components of the coiling machine. The verification scope includes verification of the pinch roller pressure, the overload coefficient of the pinch roller main motor, and the load torque of the mandrel motor, accurately determining the equipment's load-bearing limits. Based on the verification calculation results, the coiling process parameters are optimized to ensure the equipment load is suitable for the coiling conditions of thick steel plates. Simultaneously, the auxiliary coiling roller's full-process pressing function is activated, using it to press the steel plate firmly, counteracting the rigid rebound force of the thick steel plate, preventing the steel coil from loosening, and ultimately stably coiling the steel plate to be coiled, resulting in a thick, wear-resistant hot-rolled steel coil with a regular shape and qualified quality.

[0027] In some embodiments, the winding process parameters in the winding step include: pinch roller pressure 250~290KN, winding tension 13~15MPa, and auxiliary winding roller pressure 490~510KN.

[0028] The pinch rolls, operating within this pressure range, provide stable clamping friction for thick steel plates, overcoming slippage and entry deviation issues that are common during thick plate rolling, ensuring a smooth entry of the steel plate into the coiler. Coiling tension control within this range is suitable for the high rigidity and resilience of thick steel plates, preventing edge damage and internal stress concentration caused by excessive tension, while also preventing excessive interlayer gaps and loose coiling defects due to insufficient tension. The auxiliary coiling rolls, operating within this pressure range, continuously apply pressure to the outer ring of the coil, working in conjunction with their full-process pressing function to counteract the springback force of the thick steel plate, suppressing coil rebound, uncoiling, and other poor coil shape issues. These three sets of process parameters work together to maintain the coiler's load within a reasonable and safe range, further improving the coiling quality and production stability of thick wear-resistant steel coils.

[0029] In some embodiments, the following formula is used to verify the equipment capability of the winding machine pinch rolls: In the formula: The pinch roller pressure is in kN. The hot yield strength of the steel sheet to be rolled is given in MPa. b Width of the steel plate to be rolled, in mm; h The thickness of the steel plate to be rolled is in mm; i The offset angle of the upper and lower pinch rollers; The radius of the pinch roller body is in mm.

[0030] Substituting the relevant data, it can be seen that at least 246.7KN is required to complete the hot rolling and coiling process of 30*1560mm wear-resistant steel.

[0031] Increasing the pinch roll pressure to 250-290 kN enhances the gripping force. Thick steel, due to its greater thickness and weight, requires more force to smoothly enter the coiling equipment. Increased pinch roll pressure strengthens the clamping force on the steel plate, resulting in better gripping and ensuring a smooth entry into the coiling process, preventing slippage. Sufficient pinch roll pressure effectively controls the running speed and position of the steel plate, maintaining its straight-line movement during coiling, preventing deviation, ensuring accuracy and stability, improving coiling quality, and resulting in a more regular coil shape. Appropriate pinch roll pressure, in conjunction with tension, provides the necessary reaction force during coiling, helping to adjust the tension distribution of the steel plate, making the tension more uniform in both the width and length directions, and preventing coiling defects caused by uneven tension.

[0032] For thick steel plates to be rolled, excessive tension can easily cause overstretching, leading to excessive internal stress and even potential fracture. Reducing the tension to a suitable 13-15 MPa can prevent quality problems caused by overstretching during the rolling process, ensuring the integrity and mechanical properties of the rolled steel plate.

[0033] Appropriately reducing tension helps the layers of the steel sheet adhere better during winding, reducing interlayer gaps and stress concentration. This results in a tighter and more uniform winding, improving the overall quality and appearance of the coil, and reducing the risk of loosening or collapsing during subsequent storage and transportation. Furthermore, reducing tension lessens the load on the equipment during winding, reducing wear and stress on pinch rolls, auxiliary rolls, and the winding machine itself, extending equipment lifespan, lowering maintenance costs, and minimizing malfunctions and safety hazards caused by equipment overload.

[0034] Increasing the pressure of the coiling roller to 490KN~510KN can better guide the steel plate to be coiled onto the coiler and help the steel plate to be coiled smoothly onto the drum in the initial stage of coiling, forming a good starting state for coiling. This role is particularly important for thick steel plates to be coiled, ensuring a smooth start to the coiling process.

[0035] Higher pressure from the coiling rollers allows the steel sheet to be wound more tightly onto the drum during the coiling process, increasing the coiling density and making the internal structure of the coil more compact. This helps improve the quality and stability of the coil and prevents it from loosening during subsequent processing. By increasing the pressure of the coiling rollers, the coiling shape of the steel sheet can be better controlled, especially for thicker sheets. This effectively avoids undesirable coil shapes such as conical or tapered coils, ensuring a regular shape for the coil and facilitating subsequent storage, transportation, and processing.

[0036] In some embodiments, the overload coefficient of the pinch roller main motor is controlled at 2.70~2.80, and the overload coefficient of the mandrel main motor is controlled at 3.00~3.10.

[0037] The impact load during the coiling of thick-gauge wear-resistant steel is much greater than that of conventional thin-gauge hot-rolled steel sheets. The motor needs to have a certain overload redundancy to adapt to the instantaneous impact load. Maintaining this overload coefficient range on the pinch roll main motor ensures sufficient torque output under high-pressure clamping conditions, overcoming the sliding resistance of the thick steel sheet, avoiding frequent motor overload tripping and machine stalling, and ensuring continuous and stable feeding of the steel sheet. The mandrel main motor bears the dual loads of the tension torque and the bending springback torque of the steel sheet. This overload coefficient range can match the composite load characteristics during the coiling of thick-gauge steel sheets, allowing the mandrel to rotate smoothly under high torque conditions, avoiding problems such as interlayer misalignment and coil shape deviation caused by mandrel jamming and speed fluctuations. All of the above overload coefficient ranges have been verified by equipment force calibration, retaining sufficient equipment safety redundancy while maximizing the utilization of existing conventional hot rolling mill equipment capacity, achieving stable production of ultra-thick wear-resistant steel without modifying the main drive equipment.

[0038] The pinch roller pressure is checked using the following formula: In the formula: The pinch roller pressure is in kN. denoted as θ, where θ is the hot yield strength of the steel plate to be rolled (MPa); b is the width of the steel plate to be rolled (mm); h is the thickness of the steel plate to be rolled (mm); θ is the offset angle of the upper and lower pinch rolls; and r is the radius of the pinch roll body (mm).

[0039] Simultaneously, the overload coefficient of the main motor of the pinch roller is calculated, and the following formula is given: In the formula: The overload coefficient of the main motor of the pinch roller; Main motor transmission efficiency; The reduction ratio of the main motor; The maximum load torque of the upper and lower pinch roller motors is N. m; The rated output torque of the pinch roller motor is N. m.

[0040] Substituting the data, calculations show that when the winding tension is optimized to 14MPa, the overload coefficient of the main motor of the pinch roller is 2.75, which basically enables the production of 30*1560mm wear-resistant steel.

[0041] The load torque of the mandrel during the winding process mainly consists of the tension torque of the steel plate to be wound and the bending torque of the steel plate to be wound. These two items are checked.

[0042] The mandrel motor verification includes calculating the tension torque and bending torque of the steel plate to be coiled. The formula for calculating the tension torque is as follows: In the formula: The tension torque of the steel sheet to be rolled is N. m; Width of the steel plate to be rolled, in mm; The thickness of the steel plate to be rolled; — Maximum outer diameter of steel coil, mm; — Unit tension of the steel sheet to be rolled, N mm -2 ; Formula for calculating the bending moment of steel plate to be rolled: In the formula: The bending moment of the steel sheet to be rolled, N m; This is the bending moment limit value; This is the maximum diameter for winding the steel sheet to be wound; The Young's modulus of the steel sheet to be rolled; The hot yield strength of the steel sheet to be rolled is given in MPa. The formula for calculating the overload factor of a spindle motor is: ; ; ; in, The maximum load torque of the spindle motor is N. m; The bending moment of the steel sheet to be rolled, N m, The tension torque of the steel sheet to be rolled is N. m; 2 represents the reduction ratio of the spindle motor; The rated output torque of the spindle motor is N. m; Rated power of the motor, in kW; The rated speed of the motor is r / min; This is the overload coefficient of the spindle motor; The rated output torque of the spindle motor is N. m.

[0043] Substituting the relevant data, calculations show that the overload coefficient of the spindle motor is 3.07, indicating that it basically has the production capacity for 30*1560mm wear-resistant steel.

[0044] Throughout the entire winding process, the auxiliary winding roller continuously applies uniform pressure to the steel plate to be wound, ensuring that the steel plate is tightly and evenly wound onto the drum. This effectively prevents the steel plate from deviating, becoming loose, or forming a tapered shape during winding, ensuring that the steel coil has a regular shape and neat edges, thus improving the appearance quality of the steel coil.

[0045] Full-process pressing helps increase the adhesion between the layers of the steel sheet to be coiled, making the coil density more uniform and stable, thereby increasing the overall density of the steel coil. This not only reduces the risk of deformation during storage and transportation but also improves the internal quality of the steel coil, providing a better foundation for subsequent processing and use. The full-process pressing of the coiling rollers also helps to flatten and compact the surface of the steel sheet to be coiled to a certain extent, reducing unevenness and wrinkles on the surface, making the surface smoother, thus improving the surface quality of the steel sheet and reducing the impact of surface defects on product performance.

[0046] The full-process pressing function provides stable support and guidance for the steel sheet to be coiled, ensuring that the steel sheet maintains the correct position and posture throughout the coiling process. This reduces coiling interruptions or malfunctions caused by instability in the steel sheet, improving the success rate and continuity of coiling, thereby increasing production efficiency. Because the full-process pressing of the coiling roller effectively controls the coiling process, coiling parameters are more stable, reducing equipment adjustments and downtime required due to poor coil shape, thus increasing the effective operating rate of the equipment and ultimately improving overall production efficiency.

[0047] In some embodiments, the step of precision rolling the intermediate billet to obtain the steel plate to be coiled includes: discarding one of the F2 to F4 stands and one of the F5 to F7 stands, and adjusting the water spraying at the roll gap of the working stand so that the water spraying volume at the lower end is greater than that at the upper end.

[0048] Thick-gauge NM450 wear-resistant steel has a much higher deformation resistance than conventional hot-rolled carbon steel. The F2-F4 stands in the front section of the finishing mill bear the main large reduction deformation, and the load impact is the most concentrated. Skipping over one of the F2-F4 stands can reduce the rolling load on the front stand and reduce problems such as front stand overload alarms, excessive mill bounce, and reduction slippage. The F5-F7 stands in the rear section are mainly responsible for finishing the thickness and shaping of the steel plate. Thick steel plates have high rigidity and obvious springback. Skipping over a single stand in the rear section can reduce the superposition of rolling stress in the finishing stage, avoid the accumulation of residual stress inside the steel plate, and reduce the wear of the rear equipment. Overall, it can reduce the total rolling force of the finishing mill by 15-20%, and improve the operational stability and service life of the equipment.

[0049] Meanwhile, the process in this application adopts a differentiated cooling ratio where the lower spray water volume is greater than the upper spray water volume. Thick-gauge steel plate billets have large thickness and high heat capacity. During rolling, uneven heat dissipation occurs in the roll gap area of ​​the mill stand. The lower surface of the steel plate, in contact with the roll table, experiences greater heat loss and faster temperature drop, while the upper surface is exposed to air, easily leading to a temperature difference between the upper and lower surfaces, causing defects such as steel plate warping and edge wavy patterns. By increasing the lower spray water volume, the temperature loss on the lower surface of the steel plate can be compensated, accurately balancing the temperature field between the upper and lower surfaces, reducing the temperature difference, suppressing steel plate warping deformation, and stably controlling the overall warping degree of the steel plate to ≤3mm / m. Simultaneously, differentiated spray cooling can optimize the formation state of iron oxide scale on the steel plate surface, avoiding defects such as iron oxide scale indentation and surface wrinkles, significantly improving the surface quality and shape accuracy of the finished thick-gauge wear-resistant steel product.

[0050] For example, the F4 and F6 racks are removed.

[0051] Analysis of the load distribution characteristics of the finishing mill shows that F1-F3 are the large reduction deformation stands in the front section of the finishing mill, undertaking the main thinning deformation task of the intermediate billet, and experiencing the largest rolling load. F4 is the transition stand between the front and middle sections, located in the peak rolling load range. The deformation resistance of thick wear-resistant steel is much higher than that of ordinary carbon steel. If the F4 stand participates in rolling, the single-stand reduction load will far exceed the rated load of the equipment, which can easily lead to defects such as excessive mill bounce, rolling slippage, motor overload alarms, and edge tearing of the steel plate. By passing the F4 stand idle, the overall rolling force is evenly distributed to the F1-F3 working stands, achieving uniform load distribution during the large reduction deformation stage, reducing the problem of single-stand load exceeding limits, ensuring a stable rolling process for thick billets, and reducing rolling deformation defects from the source.

[0052] Stands F5 through F7 are the finishing and thickness shaping stands in the final section of the finishing mill. They are primarily responsible for correcting steel plate thickness tolerances, flattening the plate shape, and eliminating residual rolling stress, directly determining the dimensional accuracy and shape quality of the finished steel plate. Among them, stand F6 is the core finishing stand in the final section. Thick steel plates have high rigidity and significant springback effect. Continuous pressing on stand F6 can easily cause the accumulation of residual stress inside the steel plate, leading to problems such as warping, waviness, and uneven internal stress. It also exacerbates the wear of the rolls in the later stages and the fatigue wear of the equipment. Passing through stand F6 can weaken the stress accumulation effect caused by repeated pressing in the later stages, while retaining stands F5 and F7 to complete precise thickness finishing and shape correction. This ensures that the thickness tolerance and shape accuracy of the finished steel plate meet the standards, and effectively reduces the wear and tear of the later stage equipment under long-term high-load operation, extending the service life of the equipment.

[0053] In this embodiment of the application, by adjusting the water supply and drainage, the lower frame can be sprayed with water separately, which can improve the cooling difference between the upper and lower surfaces of the slab, reduce warping deformation, and improve the slab shape accuracy.

[0054] The control method of completely shutting off the spray on the roll gap of the finishing mill stand and retaining only the lower spray cooling can reduce the problem of excessive temperature drop caused by forced cooling of the upper surface, allowing the upper surface of the steel plate to cool down slowly by natural air cooling; at the same time, the lower spray water compensates for the heat loss generated by the contact between the lower surface of the steel plate and the roller table, reduces the temperature difference between the upper and lower surfaces, and achieves uniform temperature matching between the upper and lower temperature fields of thick steel plates.

[0055] In some embodiments, the heating temperature is 1200°C to 1260°C.

[0056] A heating temperature of 1200~1260℃ can balance the degree of austenitization and grain size, avoid high-temperature embrittlement, and provide a good plasticity foundation for subsequent rolling. In the embodiments of this application, by controlling the heating temperature at 1200~1260℃, the slab can be fully austenitized and the grains refined, while avoiding coarsening of the microstructure caused by overheating.

[0057] In some embodiments, the thickness of the slab is 200-250 mm, and the thickness of the intermediate slab is 58-60 mm.

[0058] In this embodiment, the slab thickness is reduced from 200-250mm to 58-60mm through 6-8 passes of rough rolling. The large reduction rate promotes dynamic recrystallization of austenite and refines the grains.

[0059] In some embodiments, the slab is an NM450 slab.

[0060] The production method in this application embodiment is applicable to the production of NM450 wear-resistant steel. The slab can be an NM450 wear-resistant steel slab with a carbon content of 0.25~0.35wt%, and alloying elements such as Cr, Mo, and Ni are added to ensure that the final product has high strength and wear resistance.

[0061] In some embodiments, the conventional hot strip line is a 2250 hot strip line.

[0062] The 2250 hot strip mill is a common, conventional hot strip mill production line. "2250" refers to the length of the mill's work rolls, which is 2250mm. This determines the range of steel plate widths the line can roll, allowing for the production of wider steel plates to meet the needs of various industries. This line features high production efficiency, stable product quality, high automation, and high rolling precision, making it a crucial piece of equipment in steel production for hot-rolled steel plates.

[0063] The main equipment includes: heating furnace, roughing mill, finishing mill, coiler and other auxiliary equipment, including descaling device, cooling system, conveyor rollers, shearing equipment, etc.

[0064] The production method of this application embodiment is applicable to the 2250 hot strip mill production line. It does not require large-scale equipment modification. The production method of producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot strip mill line realizes the production of thick-gauge wear-resistant hot-rolled steel coils and reduces production costs.

[0065] Example 1 This embodiment produces NM450 wear-resistant steel hot-rolled coils with specifications of 30mm × 1560mm. The production steps are as follows: The slab heating temperature is controlled at 1230℃; the roughing mill uses 7 passes to roll the 220mm thick slab into a 58.5mm intermediate slab; the finishing mill runs through stands F4 and F6 without load, adjusts the load distribution of stands F1 to F3, optimizes the spray water ratio at the roll gap of the front stands and adopts a single-opening downward spray water method to finish roll the intermediate slab into a 30mm thick steel plate; after rolling, laminar flow cooling is used to cool the steel plate to 680℃; before coiling, the pressure of the pinch rolls, the overload coefficient of the pinch roll main motor, and the load torque of the mandrel motor are checked; the coiling process parameters are set as follows: pinch roll pressure 280KN, coiling tension 14MPa, and auxiliary coiling roll pressure 500KN, and the auxiliary coiling roll full-process pressing function is put into operation.

[0066] After verification, the minimum required pressure of the pinch roller in this embodiment is 246.7KN, the overload coefficient of the pinch roller main motor is 2.75, the overload coefficient of the mandrel main motor is 3.07, and the equipment load is within a safe and controllable range.

[0067] Production results: There was no slippage or deviation during the rolling process, and the warping of the steel plate was ≤3mm / m; the steel coils were regular in shape, without defects such as towering, loose coils, or interlayer misalignment; the surface quality of the products was excellent, with no iron oxide scale pressed in or wrinkles. 30mm extreme thickness wear-resistant steel coils were successfully and stably produced on a conventional hot continuous rolling production line.

[0068] Example 2 This embodiment produces NM450 wear-resistant steel hot-rolled coils with specifications of 26mm × 1560mm: The slab heating temperature is 1220℃; the roughing rolling adopts 6 passes, and the intermediate slab thickness is 58mm; the finishing rolling passes through F4 and F6 stands without air, and the water ratio of the top and bottom water spray at the roll gap is optimized; the cooling temperature after rolling is 670℃; the coiling parameters are: pinch roll pressure 250KN, coiling tension 13MPa, and auxiliary coiling roll pressure 490KN; the overload coefficient of the pinch roll main motor is controlled at 2.70, the overload coefficient of the mandrel main motor is controlled at 3.00, and the auxiliary coiling roll is activated for full-process pressure.

[0069] Production results: The rolling process was continuous and stable, with no steel piling or slippage; the steel coil layers were tightly bonded, with no loose defects, and the plate shape was good.

[0070] Example 3 This embodiment produces NM450 wear-resistant steel hot-rolled coils with specifications of 29mm × 1560mm: The slab heating temperature is 1240℃; the roughing rolling adopts 8 passes, and the intermediate slab thickness is 60mm; the finishing rolling passes through the F4 and F6 stands without water spraying on the lower stand; the post-rolling cooling temperature is 690℃; the coiling parameters are: pinch roll pressure 290KN, coiling tension 15MPa, and auxiliary coiling roll pressure 510KN; the overload coefficient of the pinch roll main motor is 2.80, and the overload coefficient of the mandrel main motor is 3.10.

[0071] Production results: The rolling process was continuous and stable, with no steel piling or slippage; the steel coil layers were tightly bonded, with no loose defects, and the plate shape was good.

[0072] Example 4 This embodiment produces NM450 wear-resistant steel hot-rolled coils with specifications of 28mm×1560mm; the slab heating temperature is 1200℃, which is at the lower limit of the heating temperature range; the rough rolling adopts 7 passes, and the intermediate slab thickness is 59.0mm; the finish rolling passes through the F4 and F6 stands without water, and the water ratio of the spray water on the F1~F3 stands is optimized; the cooling temperature after rolling is 680℃; the coiling process parameters are: pinch roll pressure 270KN, coiling tension 14MPa, auxiliary coiling roll pressure 500KN, pinch roll main motor overload coefficient 2.72, mandrel main motor overload coefficient 3.03, and the auxiliary coiling roll full-process pressing function is activated.

[0073] Production results: The slab is fully austenitized with no coarse grain defects and moderate resistance to rolling deformation; the oxide scale on the steel plate surface is thin and the surface quality is excellent; there is no slippage or misalignment during the coiling process and the coil shape is regular.

[0074] Example 5 This embodiment produces NM450 wear-resistant steel hot-rolled coils with specifications of 27mm×1560mm; the slab heating temperature is 1250℃; the rough rolling adopts 8 passes, the slab thickness is 240mm, and a 59mm thick intermediate slab is obtained; the finish rolling passes through F4 and F6 stands without air, and the shape is controlled by single-opening downward spray water; the post-rolling cooling temperature is 685℃; the coiling process parameters are: pinch roll pressure 285KN, coiling tension 14.5MPa, auxiliary coiling roll pressure 505KN; the overload coefficient of the pinch roll main motor is 2.78, and the overload coefficient of the mandrel main motor is 3.09.

[0075] Production results: The rolling deformation is uniform, the internal stress of the thick-gauge intermediate billet is fully released, and there is no curling phenomenon; the grain refinement is obvious; the finished steel plate has good mechanical uniformity, the coiling and forming is stable, and the equipment is not subjected to impact load.

[0076] Example 6 This embodiment produces 30mm×1800mm wide NM450 wear-resistant steel hot-rolled coils; the slab heating temperature is 1230℃; the roughing rolling process involves 7 passes, with an intermediate slab thickness of 58.5mm; the finishing rolling process involves passing through F4 and F6 stands without load, with optimized spray water ratio; the laminar flow cooling termination temperature is 680℃; the coiling verification is recalculated based on the width specification, with a pinch roll pressure of 290KN, a coiling tension of 15MPa, and an auxiliary coiling roll pressure of 510KN; the overload coefficient of the pinch roll main motor is 2.80, and the overload coefficient of the mandrel main motor is 3.10.

[0077] Production results: The transverse thickness is uniform during the wide-width thick plate rolling process, with no single-sided deviation; the clamping rolls have strong clamping stability, and the wide steel plate to be rolled has no transverse offset; the steel coil end face is neat, without tower shape or edge wrinkles, proving that this process can be adapted to the production of wide-width extreme thickness wear-resistant steel, and the process has strong versatility.

[0078] Example 7 This embodiment produces NM450 wear-resistant steel hot-rolled coils with specifications of 27mm×1560mm; the slab heating temperature is 1225℃, roughing is performed in 7 passes, and the intermediate slab thickness is 60.0mm; the finishing mill passes through F4 and F6 stands without water, adopting an optimized water supply ratio mode and not using single-opening bottom spraying; the post-rolling cooling temperature is 675℃; the coiling parameters are: pinch roll pressure 265KN, coiling tension 13.5MPa, and auxiliary coiling roll pressure 495KN.

[0079] Production results: The temperature difference between the upper and lower surfaces of the steel plate is controllable, the warpage is ≤3mm / m, and the plate shape is good; compared with the single-pass spraying process, this mode is suitable for medium thickness specifications, the surface cooling is more gentle, and the oxide scale is uniform and dense.

[0080] Comparative Example 1 The conventional 2250 hot continuous rolling process was adopted, with all stands of the finishing mill fully engaged in rolling without any stand-off treatment. The remaining raw materials, heating temperature, cooling temperature, and coil specifications remained consistent with those in Example 1. The spray water ratio was not optimized, and no equipment force check was performed before coiling; conventional coiling pressure and tension were used.

[0081] Production results: The rolling load of the single stand in the finishing mill exceeded the limit, and the rolling force was more than 20% higher; the temperature difference between the upper and lower surfaces of the steel plate was large, and the warping was greater than 8mm / m; during the coiling process, the steel plate to be coiled slipped and deviated, making it impossible to coil stably, resulting in production interruption and the inability to produce qualified thick wear-resistant steel coils.

[0082] Comparative Example 2 The process flow and rolling parameters are the same as in Example 1, except that the coiling tension is increased to 18MPa, which exceeds the tension range of 13~15MPa in this application, without changing the other pressure parameters.

[0083] Production results: Thick steel plates have high rigidity and high tension, which causes extrusion and tearing at the edges of the steel plates, and stress concentration inside the steel plates to be rolled; the inner layers of the steel coils are significantly deformed by extrusion, with excessive compaction between layers and local indentations, resulting in poor mechanical properties of the product and a decrease in yield.

[0084] Comparative Example 3 The process flow is the same as in Example 1, except that the three force checks of the winding machine are cancelled, the full-process pressing function of the auxiliary winding roller is not activated, and conventional intermittent auxiliary winding control is adopted.

[0085] Production results: The thick steel plate had a large springback, and the winding was loose in the initial stage of coiling; the outer ring of the steel coil springback and opened, resulting in tower-shaped and uncoiled defects; the mandrel experienced large instantaneous load fluctuations, the motor load was unstable, and there was a risk of overload tripping, making mass production impossible.

[0086] Comparative Example 4 The production process of NM450 wear-resistant steel hot-rolled coils with specifications of 30mm×1560mm is similar to that of Example 1, except that the reduction amount of the roughing pass is adjusted to control the thickness of the intermediate billet to 55mm.

[0087] Test results: The intermediate billet thickness was too small, the single-pass reduction in finishing rolling was significantly increased, the rolling deformation rate was too fast, the internal grain deformation of the steel plate was uneven, and problems such as local grain coarsening and stress concentration occurred; the finishing rolling load was abnormally high, the rolling force was 18% higher than in Example 1, approaching the equipment overload threshold; slight edge tearing and uneven cooling of the upper and lower surfaces occurred during the steel plate rolling process, and the plate warping reached 7.5 mm / m; the rigidity and springback characteristics of the steel plate to be coiled were abnormal, and slight slippage and deviation frequently occurred during the coiling process. The gap between the layers of the steel coil was uneven, and there was a risk of local loosening of the coil. The shape and internal structure of the finished plate did not meet the standards, and stable mass production could not be achieved.

[0088] Comparative Example 5 This comparative example produces NM450 wear-resistant steel hot-rolled coils with specifications of 30mm×1560mm. The overall process flow is similar to that of Example 1, except that a cooling method with full opening of water spray at the top and bottom of the roller gap of a traditional finishing mill and equal water volume at the top and bottom is adopted.

[0089] Production results: The upper surface of the steel plate experienced limited shrinkage and a sudden increase in rigidity, while the lower surface had excessive plasticity. After rolling, the steel plate exhibited severe upward warping defects, with an overall warping degree reaching 9.2 mm / m. Simultaneously, the rapid cooling of the upper surface of the steel plate caused the iron oxide scale to solidify quickly, adhere, and compact, resulting in large-area iron oxide scale indentation and surface wrinkling defects, leading to substandard surface quality of the finished product.

[0090] A comparison of Examples 1-7 with Comparative Examples 1-5 reveals that this application addresses the technical challenges of producing 25-30mm thick wear-resistant steel on conventional hot continuous rolling lines. These challenges include high rolling load, poor plate shape, coil slippage, springback and uncoiled coils, and motor overload. This is achieved through optimized roughing passes, finishing mill stand and spray water, low-temperature laminar flow cooling, and multi-dimensional force verification of the coiler. Furthermore, it incorporates limited pinch roll pressure, coiling tension, auxiliary coil pressure, and full-process pressing functionality. Compared to existing processes, this application eliminates the need for equipment modifications and medium-thickness plate production lines. It enables stable mass production of ultra-thick wear-resistant steel directly on a 2250 conventional hot continuous rolling line, reducing rolling force by 15-20%, achieving a steel plate warpage ≤3mm / m, and maintaining a coil shape qualification rate close to 100%, while also reducing production costs.

[0091] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A production method for producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot continuous rolling line, characterized in that, include: In the rough rolling step, a slab of wear-resistant steel is obtained. The slab is heated and then subjected to 6 to 8 passes of rough rolling to obtain an intermediate slab with a thickness of 58 to 60 mm. In the finishing rolling step, the finishing mill stand is subjected to stand-off treatment and the stand load distribution is adjusted. The water ratio of the upper and lower water spray at the roll gap of the finishing mill stand is within a preset range. The intermediate billet is finished rolled to obtain a thick steel plate with a thickness of 25~30mm. The cooling step involves laminar cooling of the thick steel plate to 670~690℃ to obtain the steel plate to be rolled. In the winding step, force verification calculations are performed on the key load-bearing components of the winding machine. Based on the results of the verification calculations, the winding process parameters are optimized, the full-process pressing function of the auxiliary winding roller is activated, and the steel plate to be wound is wound to obtain a thick-gauge wear-resistant hot-rolled steel coil. The verification of the key load-bearing components of the winding machine includes verification of the pinch roller pressure, verification of the overload coefficient of the pinch roller main motor, and verification of the load torque of the mandrel motor.

2. The production method for producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot continuous rolling line according to claim 1, characterized in that, In the winding step, the winding process parameters include: pinch roller pressure 250~290KN, winding tension 13~15MPa, and auxiliary winding roller pressure 490~510KN.

3. The production method for producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot continuous rolling line according to claim 1, characterized in that, The overload coefficient of the pinch roller main motor is controlled at 2.70~2.80, and the overload coefficient of the mandrel main motor is controlled at 3.00~3.

10.

4. The production method for producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot rolling line according to claim 1, characterized in that, The finishing rolling process includes: Remove one of the F2-F4 frames and one of the F5-F7 frames, and adjust the water flow of the roller gap spray on the working frame so that the water flow of the lower spray is greater than that of the upper spray.

5. The production method for producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot continuous rolling line according to claim 1, characterized in that, In the finishing rolling process, F4 and F6 stands are removed, and the water distribution ratio between the upper and lower spray water in the roll gap of F1-F4 stands is optimized so that the lower spray water volume is greater than the upper spray water volume.

6. The production method for producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot continuous rolling line according to claim 1, characterized in that, In the rough rolling step, the slab is heated to a temperature of 1200℃~1260℃, and the rough rolling passes are 7.

7. The production method for producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot rolling line according to claim 1, characterized in that, The pinch roller pressure is checked using the following formula: Where: P is the pinch roller pressure, kN; denoted as θ, where θ is the hot yield strength of the steel plate to be rolled (MPa); b is the width of the steel plate to be rolled (mm); h is the thickness of the steel plate to be rolled (mm); θ is the offset angle of the upper and lower pinch rolls; and r is the radius of the pinch roll body (mm).

8. The production method for producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot continuous rolling line according to claim 1, characterized in that, The overload coefficient of the pinch roller main motor is checked using the following calculation formula: In the formula: The overload coefficient of the main motor of the pinch roller; Main motor transmission efficiency; The reduction ratio of the main motor; The maximum load torque of the upper and lower pinch roller motors is N. m; The rated output torque of the pinch roller motor is N. m.

9. The production method for producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot continuous rolling line according to claim 1, characterized in that, The mandrel motor verification includes calculating the tension torque and bending torque of the steel plate to be coiled. The formula for calculating the tension torque of the steel plate to be coiled is as follows: In the formula: The tension torque of the steel sheet to be rolled is N. m; Width of the steel plate to be rolled, in mm; The thickness of the steel plate to be rolled; — Maximum outer diameter of steel coil, mm; — Unit tension of steel sheet to be rolled, N mm -2 ; Formula for calculating the bending moment of steel plate to be rolled: In the formula: The bending moment of the steel sheet to be rolled is N. m; This is the bending moment limit value; This is the maximum diameter for winding the steel sheet to be wound; The Young's modulus of the steel sheet to be rolled; The hot yield strength of the steel sheet to be rolled is given in MPa. The formula for calculating the overload factor of a spindle motor is: ； ； ； in, The maximum load torque of the spindle motor is N. m; The bending moment of the steel sheet to be rolled is N. m, The tension torque of the steel sheet to be rolled is N. m; 2 represents the reduction ratio of the spindle motor; The rated output torque of the spindle motor is N. m; Rated power of the motor, in kW; The rated speed of the motor is r / min; This represents the overload coefficient of the spindle motor; The rated output torque of the spindle motor is N. m.

10. The production method for producing thick-gauge wear-resistant hot-rolled steel coils on a conventional hot continuous rolling line according to claim 1, characterized in that, The standard hot strip rolling line is a 2250 hot strip rolling production line.

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