Rolling process for improving dimensional precision of finished electrode flat steel product

Abstract

The invention discloses a rolling process for improving the dimensional accuracy of an electrode flat steel finished product, and belongs to the technical field of steel rolling. The technology comprises the steps that after a steel billet is heated to 1180-1220 DEG C, horizontal-vertical-vertical-horizontal-horizontal multi-pass cogging is conducted through a two-roller cogging mill, then a combined mode of vertical rolling edge rolling, horizontal rolling angle rolling and universal rolling mill shaping is sequentially adopted in the finish rolling process, and the roll bounce amount is controlled through a dynamic roll gap compensation technology in the rolling process; and finally, carrying out hot straightening and cooling. According to the method, the problems of large width and thickness deviation and insufficient straightness in a traditional process are solved, the consistency and production efficiency of finished products are improved, and the method is suitable for batch production of electrode flat steel of different specifications and has wide application prospects.

Description

Technical Field

[0001] This invention belongs to the field of steel rolling technology, and particularly relates to a rolling process for improving the dimensional accuracy of finished electrode flat steel. Background Technology

[0002] Electrode flat steel, as a crucial material for the cathode conductive rods in electrolytic aluminum production, is characterized by high consumption and stringent requirements for dimensional stability. With the continuous increase in electrolytic aluminum production capacity, various electrolytic aluminum plants have placed higher demands on the dimensional accuracy (including width, thickness, straightness, and corner radius) of the finished electrode flat steel. However, the existing process using a two-roll reversible rolling mill for direct rolling often suffers from insufficient side straightness, asymmetrical corner deformation, and significant width and thickness deviations, resulting in large fluctuations in finished product dimensional accuracy and failing to meet the needs of high-end users. Therefore, there is an urgent need to propose a new process method that can reduce production costs and improve production efficiency while ensuring high dimensional accuracy.

[0003] Application number CN202311239710.5 discloses an ultra-low carbon, low manganese-sulfur ratio electrode flat steel and its rolling forming method. The method includes the following steps: S1, cutting the slab into square steel and heating it into a hot billet in a walking beam furnace; S2, descaling the hot billet with high-pressure water and then starting rolling; S3, after online straightening in the final rolling pass, processing the rolled material into multi-length electrode flat steel using a hot saw; S4, cooling the multi-length electrode flat steel on a cooling bed and then cooling it to room temperature using a stacking cooling method. This invention solves the technical problem of corner cracking in ultra-low carbon steel rolling under low manganese-sulfur ratio conditions by reasonably controlling the cutting quality of ultra-low carbon steel slabs and strictly controlling the heating temperature of the cut square billet, the temperature after water descaling, the rolling temperature, and the stacking temperature, while obtaining electrode flat steel with excellent electrical conductivity. However, it does not solve the problems of large width-to-thickness deviation and insufficient straightness.

[0004] Application number CN202310291944.8 discloses a method for producing electrode flat steel. The method includes: adding active lime and high-carbon ferromanganese to molten steel during the converter tapping process to obtain new molten steel; subjecting the new molten steel to vacuum circulation decarburization treatment to obtain treated molten steel; adding refining slag and aluminum particles to the treated molten steel for refining to obtain refined molten steel; feeding calcium-iron cored wire into the refined molten steel for calcium treatment; and producing electrode flat steel through continuous casting and rolling. This method increases the carbon content at the converter endpoint and reduces the oxygen content in the molten steel at the endpoint, reducing the formation of Al2O3 inclusions from the source and improving the cleanliness of the molten steel. Simultaneously, it fully utilizes the advantages of carbon-oxygen reaction deoxidation during the RH vacuum treatment process, further improving the cleanliness of the molten steel on one hand, and using carbon instead of aluminum for deoxidation on the other hand, significantly reducing production costs, ultimately achieving low-cost, high-quality production of low-carbon, low-silicon electrode flat steel. However, it does not solve the problems of large width-to-thickness deviation and insufficient straightness.

[0005] Application number CN202510692675.5 discloses a method for producing rare earth alloyed electrode flat steel, belonging to the field of materials metallurgy. It includes a steelmaking process flow; a rolling process flow; and optimized steelmaking process parameters and rolling process control parameters. The chemical composition of the electrode flat steel (mass percentage) is: C: ≤0.005%, Si: ≤0.02%, Mn: ≤0.03%, P ≤0.008%, S ≤0.005%, Ti: 0.03%~0.04%, RE: 0.0040%~0.0060%, Al: ≤0.040%, with the remainder being Fe and other trace impurities. This invention, through reasonable chemical composition design and production process control, can effectively improve the strength and conductivity of pure iron for electrolytic aluminum, ensuring a yield strength ≥200MPa, tensile strength ≥280MPa, and room temperature conductivity (20℃) ≤0.12μΩ·mm. However, it does not solve the problems of large width-to-thickness deviation and insufficient flatness. Summary of the Invention

[0006] The purpose of this invention is to provide a rolling process that improves the dimensional accuracy of finished electrode flat steel. By combining "optimized billet opening - multi-pass precision rolling control - universal shaping - dynamic straightening", the dimensional accuracy and stability of the product are significantly improved.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] This invention provides a rolling process for improving the dimensional accuracy of finished electrode flat steel, comprising:

[0009] The steel billet is heated to 1180~1220℃, held for 2.0~2.5 h, and the furnace exit temperature is ≥1150℃;

[0010] A two-roll mill is used for multiple passes of flat-vertical-vertical-flat-flat, with a first pass reduction ratio of 18% to 22% and a pass depth of 30 to 32 mm.

[0011] During the finishing rolling process, vertical rolling edge rolling, flat rolling corner rolling, and universal mill shaping are performed sequentially. The vertical rolling reduction is 5-7 mm, the flat rolling reduction is 2-4 mm, the universal mill horizontal roll reduction is 2-3 mm, and the vertical roll reduction is 1.5-2.0 times that of the horizontal roll. The radius of the vertical rolling edge pass is 20 mm, the radius of the flat rolling corner pass is 16 mm, and the radius of the universal mill horizontal roll is 2 mm.

[0012] Dynamic roll gap compensation is used during the rolling process, with the vertical roll bounce controlled at 3.0–4.0 mm and the horizontal roll bounce at approximately 2.0 mm.

[0013] The exit temperature of the finishing mill is controlled at 850-880 ℃, followed by hot straightening with a straightening force of 3.0-3.5 MN, and finally natural cooling or slow cooling.

[0014] The width and thickness deviations of the finished products are controlled within ±1.0 mm and ±0.5 mm, respectively; after the hot straightening process, the side flatness is stabilized at 88% to 90%; and the first-pass yield of the finished products reaches over 97%.

[0015] Furthermore, the steel billet is a low-alloy steel billet produced by converter smelting—LF refining—continuous casting, with a specification of 240mm×320mm.

[0016] Furthermore, the heating furnace is a walking beam furnace, with the heating rate controlled at 3-5℃ / min to ensure uniform heating of the steel billet.

[0017] Furthermore, it also includes an online measurement and control system, specifically a laser width gauge and an infrared thermometer, used to monitor the width, thickness and temperature of the rolled piece in real time, and linked with the roll servo system.

[0018] Furthermore, the total number of rounding passes is 5 to 7, and the temperature exiting the rounding machine is maintained at 1050 to 1080 ℃.

[0019] Furthermore, during the finishing rolling process, the vertical roll reduction of the universal rolling mill is more than 50% greater than the horizontal roll reduction to ensure the accuracy of the finished product width.

[0020] Furthermore, the straightening angle of the hot straightening machine is controlled between 0.3° and 0.5° to obtain the best straightness.

[0021] Finished product quality: The electrode flat steel produced by the process of this invention has significantly improved dimensional accuracy: side straightness ≥85%, corner radius 13±0.5 mm, width tolerance ±1.0 mm, and thickness tolerance ±0.5 mm, meeting the high-precision requirements of electrolytic aluminum plants.

[0022] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0023] (1) Significantly improved dimensional accuracy: By optimizing the pass design and multi-pass combined rolling, combined with dynamic roll gap compensation, the width and thickness deviations of the finished product are stabilized within ±1.0 mm and ±0.5 mm respectively, which is far superior to traditional processes; (2) Improved flatness and corner radius stability of the finished product: By adopting universal rolling mill shaping and hot straightening processes, the side flatness is stabilized at over 85%, and the corner radius is controlled at 13±0.5 mm. mm, ensuring high stability and consistency of electrode flat steel; (3) Reduced production costs: This invention can be achieved using existing rolling mill equipment. By optimizing process parameters and adding dynamic control measures, rework and scrap caused by non-compliant dimensions are reduced, and the overall production cost is reduced by about 8% to 12%; (4) Stronger adaptability: The process is applicable to electrode flat steel of different specifications. In particular, it can still ensure the precision of finished products in the rolling process of large specifications and high compression ratio, thus broadening the specification range of electrode flat steel production; (5) Improved production efficiency: By reducing the frequency of roll changing and the finished product rework rate, the rolling mill utilization rate is increased by more than 10%, and the first-pass yield of finished products is increased to more than 97%, which meets the growing demand of the electrolytic aluminum industry for high-precision electrode flat steel. Detailed Implementation

[0024] The following is a detailed description of a rolling process for improving the dimensional accuracy of finished electrode flat steel products according to the present invention.

[0025] The present invention proposes a rolling process to improve the dimensional accuracy of finished electrode flat steel. The overall process flow includes the following steps:

[0026] Billet preparation and heating: High-quality low-alloy steel billets, 240 mm × 320 mm in size, are selected from those produced by converter smelting + LF refining + continuous casting. The billets are heated in a walking beam furnace at a temperature controlled between 1180 and 1220℃ for 2.0–2.5 hours to ensure uniform internal temperature. The billet exit temperature is controlled above 1150℃, and the temperature entering the billet mill is not lower than 1100℃ to avoid difficulties in biting and cracking due to excessively low temperatures.

[0027] Forging process: A 750 mm two-roll reversible forging mill is used, with a pass system of "flat-vertical-vertical-flat-flat" combination to ensure gradual and uniform reduction in width and thickness. The first pass reduction is controlled at 18%–22%, the pass depth is approximately 30 mm, and the sidewall slope is ≥10° to ensure smooth entry of the rolled piece head and reduce edge cracking. The total number of forging passes is 5–7, and the exit temperature from the forging mill is maintained at 1050–1080 ℃.

[0028] Finishing rolling process: Finishing rolling adopts a three-pass combination of "vertical rolling for edge rolling - horizontal rolling for corner rolling - universal mill for shaping":

[0029] Vertical rolling edge rolling: the reduction is 5-7 mm, and the rounded corner radius is controlled at 20 mm, mainly to correct the problem of unevenness at the edge of the billet;

[0030] Flat rolling corner: reduction 2-4 mm, corner radius of the die is 16 mm, to ensure uniform corner forming;

[0031] Universal rolling mill design: horizontal roll reduction of 2-3 mm, vertical roll reduction of 1.5-2.0 times that of the horizontal roll, and horizontal roll corner radius of 2 mm to ensure precise control of width and thickness.

[0032] Roll bounce compensation and online monitoring: During the rolling process, a hydraulic servo system compensates for roll bounce, controlling the vertical roll bounce to 3-4 mm and the horizontal roll bounce to approximately 2 mm. An online measurement and control system is equipped to monitor rolling force and workpiece width and thickness in real time, automatically adjusting the roll gap according to the load to ensure the dimensional accuracy of the finished product.

[0033] Straightening and Cooling: The exit temperature of the finishing mill is controlled at 850-880 ℃, and then the product enters the hot straightener. The straightening force is controlled at 3.0-3.5 MN to ensure that the side flatness of the product is ≥85%. After straightening, the rolled piece is sent to the cooling bed for natural cooling to avoid stress concentration and warping caused by water cooling.

[0034] Finished product inspection and performance indicators: The electrode flat steel produced by this process has a width deviation of ≤±1.0 mm, a thickness deviation of ≤±0.5 mm, a corner radius of 13±0.5 mm, and a side straightness of ≥85%. Metallographic inspection shows that the microstructure is uniform and there are no obvious defects such as cracks, folds, or overheating, meeting the requirements of the electrolytic aluminum industry for high-precision electrode flat steel.

[0035] Example 1:

[0036] Process conditions: Select steel billets with specifications of 240 mm × 320 mm, heat to 1200℃, hold for 2.5 h, exit temperature 1180℃, and enter the billet mill temperature 1110℃. Use a 750 mm two-roll billet mill for "flat-vertical-vertical-flat-flat" pass milling, with a first pass reduction ratio of 20% and a pass depth of 30 mm;

[0037] Process control: During finishing rolling, the vertical rolling edge reduction is 6 mm, and the corner radius is 20 mm; the horizontal rolling corner reduction is 3 mm, and the corner radius is 16 mm; the universal mill horizontal roll reduction is 2.5 mm, and the vertical roll reduction is 4.0 mm, with a vertical roll to horizontal roll reduction ratio of approximately 1.6. Vertical roll bounce is controlled at 3.2 mm, and horizontal roll bounce is 2.0 mm. The online monitoring and control system adjusts the roll gap in real time. The finishing mill exit temperature is controlled at 860 ℃, the straightening force is 3.2 MN, and natural cooling is achieved on the cooling bed.

[0038] Results data: Finished product size 96×198 mm, width deviation ±0.9 mm, thickness deviation ±0.4 mm, corner radius 13.1 mm, side flatness 88%, uniform microstructure, and pass rate 97.5%.

[0039] Example 2:

[0040] Process conditions: Select steel billets of the same specifications, heat to 1185 ℃, hold for 2.0 h, furnace exit temperature 1160 ℃, and mill entry temperature 1105 ℃. Use the same pass system for billet preparation, with a first pass reduction ratio of 22% and a pass depth of 32 mm;

[0041] Process control: In the finishing mill, the vertical roll edge reduction is 5 mm, and the corner radius is 20 mm; in the flat mill, the corner reduction is 2 mm, and the corner radius is 16 mm; in the universal mill, the horizontal roll reduction is 3 mm, and the vertical roll reduction is 4.5 mm, with a vertical roll to horizontal roll reduction ratio of 1.5. Online dynamic compensation: vertical roll bounce is 3.5 mm, and horizontal roll bounce is 2.0 mm. The finishing mill exit temperature is 870 ℃, the straightening force is 3.4 MN, and the cooling bed is used for natural cooling.

[0042] Results data: Finished product size 120×198 mm, width deviation ±0.8 mm, thickness deviation ±0.5 mm, corner radius 13.0 mm, side flatness 90%, finished product qualification rate 98%, significantly better than traditional process.

[0043] Comparative Example 1 (Traditional Two-Roll Process):

[0044] Process conditions: The steel billet is heated to 1200 ℃ and directly rolled into shape using a two-roll reversible rolling mill, without a universal rolling mill for shaping;

[0045] Results data: finished product width deviation ±2.5 mm, thickness deviation ±1.2 mm, corner radius deviation more than 1.5 mm, side straightness only 65%, obvious bending.

[0046] Comparative Example 2 (without dynamic compensation):

[0047] Process conditions: Similar to Example 1, but no roll bounce compensation was performed during the finishing rolling process, and the results were based solely on the following data: width deviation ±1.8 mm, thickness deviation ±1.0 mm, corner radius deviation ±1.2 mm, side flatness 74%, and large dimensional fluctuations.

[0048] Comparative Example 3 (without straightening process):

[0049] Process conditions: A universal rolling mill was used for shaping, but the mill was directly cooled on a cooling bed after finishing and no hot straightening was performed;

[0050] Results: Width and thickness deviations were generally controlled within ±1.2 mm, but the side flatness was only 72%, with obvious warping, and the product yield was less than 85%.

[0051] Table 1. Process Comparison between Examples and Comparative Examples

[0052] Example Heating temperature (°C) roughing process Finishing rolling method Dynamic compensation Straightening process Outlet temperature (°C) Example 1 1200 Flat-Up-Up-Flat-Flat, with a reduction ratio of 20% and a depth of 30 mm. Vertical rolling 6 mm, horizontal rolling 3 mm, universal shaping (horizontal 2.5 mm, vertical 4.0 mm) Vertical 3.2 mm, horizontal 2.0 mm Thermal straightening, 3.2MN 860 Example 2 1185 Flat-Up-Up-Flat-Flat, reduction ratio 22%, depth 32 mm Vertical rolling 5 mm, horizontal rolling 2 mm, universal shaping (horizontal 3.0 mm, vertical 4.5 mm) Vertical 3.5 mm, horizontal 2.0 mm Thermal straightening, 3.4MN 870 Comparative Example 1 1200 Two-roll direct rolling No universal shaping none none 850 Comparative Example 2 1200 Same as Example 1 Same as Example 1 none Thermal straightening, 3.0MN 860 Comparative Example 3 1200 Same as Example 1 Same as Example 1 have none 860

[0053] Table 2 Performance Comparison Table

[0054] Example Finished product specifications (mm) Width deviation (mm) Thickness deviation (mm) Corner radius (mm) Straightness (%) Pass rate (%) Example 1 96×198 ±0.9 ±0.4 13.1 88 97.5 Example 2 120×198 ±0.8 ±0.5 13.0 90 98.0 Comparative Example 1 96×198 ±2.5 ±1.2 Deviation > ±1.5 65 80 Comparative Example 2 96×198 ±1.8 ±1.0 Deviation ±1.2 74 86 Comparative Example 3 96×198 ±1.2 ±1.0 13.2 72 85

[0055] As can be seen from the examples and comparative examples, the present invention has the following advantages: (1) Significantly improved dimensional accuracy: The present invention, through optimized die design, dynamic roll gap compensation and universal mill shaping, controls the deviation of the finished product width and thickness to within ±1.0 mm and ±0.5 mm respectively, which is far superior to the deviation of ±1.8 to ±2.5 mm in the comparative example. (2) Significantly improved flatness of finished product: The side flatness of the examples is stable at 88% to 90% after hot straightening process, which is significantly improved compared with 65% to 74% in the comparative example, and significantly reduces the bending and twisting defects of the finished product. (3) Stable rounded corner forming: In the examples, the rounded corner radius is stable at 13±0.5 mm, which is uniform, while the deviation of ±1.2 mm or more often occurs in the comparative example, which significantly ensures the welding and installation performance of users. (4) Improved yield and economy: The process of the present invention enables the first-pass yield of finished products to reach more than 97%, which is far higher than 80% to 86% in the comparative example, effectively reducing rework and scrap costs, and improving the overall production efficiency by about 10%. (5) Greater adaptability: The process of this invention is not only applicable to 96×198 mm specifications, but also maintains good precision and stability in large-specification products such as 120×198 mm, which broadens the range of product specifications and enhances market competitiveness.

[0056] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A rolling process for improving the dimensional accuracy of finished electrode flat steel, characterized in that, include: The steel billet is heated to 1180~1220℃, held for 2.0~2.5 h, and the furnace exit temperature is ≥1150℃; A two-roll mill is used for multiple passes of flat-vertical-vertical-flat-flat, with a first pass reduction ratio of 18% to 22% and a pass depth of 30 to 32 mm. During the finishing rolling process, vertical rolling edge rolling, flat rolling corner rolling, and universal mill shaping are performed sequentially. The vertical rolling reduction is 5-7 mm, the flat rolling reduction is 2-4 mm, the universal mill horizontal roll reduction is 2-3 mm, and the vertical roll reduction is 1.5-2.0 times that of the horizontal roll. The radius of the edge rolling pass is 20 mm, the radius of the corner rolling pass is 16 mm, and the radius of the horizontal roll is 2 mm. Dynamic roll gap compensation is used during the rolling process, with the vertical roll bounce controlled at 3.0–4.0 mm and the horizontal roll bounce at approximately 2.0 mm. The exit temperature of the finishing mill is controlled at 850-880 ℃, followed by hot straightening with a straightening force of 3.0-3.5 MN, and finally natural cooling or slow cooling. The width and thickness deviations of the finished products are controlled within ±1.0 mm and ±0.5 mm, respectively; after the hot straightening process, the side flatness is stabilized at 88% to 90%; and the first-pass yield of the finished products reaches over 97%.

2. The rolling process for improving the dimensional accuracy of finished electrode flat steel according to claim 1, characterized in that, The steel billet is a low-alloy steel billet produced by converter smelting, LF refining, and continuous casting, with a specification of 240 mm × 320 mm.

3. The rolling process for improving the dimensional accuracy of finished electrode flat steel according to claim 1, characterized in that, The heating furnace is a walking beam furnace, and the heating rate is controlled at 3-5℃ / min to ensure uniform heating of the steel billet.

4. The rolling process for improving the dimensional accuracy of finished electrode flat steel according to claim 1, characterized in that, It also includes an online measurement and control system, specifically a laser width gauge and an infrared thermometer, used to monitor the width, thickness and temperature of the rolled piece in real time, and linked with the roll servo system.

5. The rolling process for improving the dimensional accuracy of finished electrode flat steel according to claim 1, characterized in that, The total number of rounding passes is 5 to 7, and the temperature exiting the rounding machine is maintained at 1050 to 1080 ℃.

6. The rolling process for improving the dimensional accuracy of finished electrode flat steel according to claim 1, characterized in that, During the finishing rolling process, the vertical roll reduction of the universal rolling mill is more than 50% greater than the horizontal roll reduction to ensure the width accuracy of the finished product.

7. The rolling process for improving the dimensional accuracy of finished electrode flat steel according to claim 1, characterized in that, The straightening angle of the hot straightening machine is controlled between 0.3° and 0.5° to obtain the best straightness.