A high-end strip steel quality method based on inclusion press-in control

Abstract

The application discloses a high-end strip steel quality control method based on inclusion press-in control, and belongs to the technical field of metallurgical rolling, and comprises the following steps: S1, molten steel composition and superheat control; S2, slab heating control: controlling the furnace time of the slab and the temperature of the slab heating; S3, pre-precision rolling cooling control: installing an intermediate slab cooling water device at the precision rolling inlet to control the precision rolling inlet temperature; S4, final rolling and coiling temperature control: controlling the final rolling temperature to be 875 DEG C to 900 DEG C, and the coiling temperature to be 580 DEG C to 610 DEG C; S5, roll cooling and grinding control: the roll cooling time after leaving the machine is greater than or equal to 120 min, and the roll surface temperature is lowered to below 40 DEG C before grinding; and S6, precision rolling pass reduction rate distribution: controlling the pass reduction rate of F1 to F3 to be less than or equal to 35%, and the pass reduction rate of F4 to F7 to be less than or equal to 15%. The application can overcome the technical problem of insufficient control of press-in type metal inclusions in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical rolling technology, and in particular relates to a high-end strip steel quality control method based on inclusion pressing control. Background Technology

[0002] With the rapid development of lightweight automobiles, high-end home appliances, and high-efficiency electrical steel, the market has placed extremely stringent demands on the comprehensive indicators of high-end strip steel, such as surface quality, fatigue life, and corrosion resistance. Among the surface defects of strip steel, pitting and indentations caused by indented metallic inclusions (such as titanium inclusions and composite inclusions) and iron oxide scale are key bottlenecks restricting the improvement of product qualification rate. Existing research focuses on the analysis of the composition, size, and morphological characteristics of the inclusions themselves, while research on the dynamic behavior of inclusions during rolling, their interaction mechanism with the matrix, and their impact on the comprehensive performance of strip steel is significantly insufficient. Traditional inclusion control strategies mainly focus on the static content control of elements such as titanium and nitrogen in molten steel, lacking a systematic control scheme based on the critical conditions for inclusion indentation, making it difficult to achieve precise suppression of indentation defects.

[0003] Furthermore, in actual production, the problem of pitting defects caused by the difficulty in removing iron oxide scale at the beginning and end of the coil due to high temperature has long existed; damage to the oxide film on the rolls during the rolling process is also an important cause of indentation defects on the surface of the strip. Existing technologies lack a systematic solution for maintaining the integrity of the oxide film on the rolls.

[0004] Therefore, there is an urgent need for a precise control method that starts from the inclusion pressing mechanism and covers the entire process of steel composition control, rolling temperature regime, roll management and head and tail control, so as to effectively reduce the surface defect rate of strip steel and improve the quality and market competitiveness of high-end strip steel products. Summary of the Invention

[0005] To address the above-mentioned technical deficiencies, this invention provides a high-end strip steel quality control method based on inclusion press-in control, which overcomes the problem of insufficient control over press-in metal inclusions in the prior art.

[0006] To achieve the above-mentioned technical objectives, the present invention is implemented through the following technical solution: A high-end strip steel quality control method based on inclusion indentation control includes: S1. Steel composition and superheat control: control the N in the molten steel to ≤50ppm, S to ≤0.015%, As to ≤50ppm, Sb to ≤0.01%, and control the Ti content to 0.012%~0.035% according to the target inclusion type. At the same time, control the superheat control accuracy of the tundish temperature to ±5℃. S2. Slab heating control: Control the slab time in the furnace to 150-180 minutes, and the slab heating temperature range is 1200℃~1250℃. S3. Cooling control before finishing milling: Install intermediate billet cooling water device at the entrance of finishing mill to control the temperature at the entrance of finishing mill to 940℃~1000℃; S4. Final rolling and coiling temperature control: Control the final rolling temperature to 875℃~900℃ and the coiling temperature to 580℃~610℃. S5. Roll cooling and grinding control: The cooling time of the rolls after the mill is ≥120min. Grinding is carried out after the surface temperature of the rolls drops to below 40℃. S6. Reduction rate distribution of finishing rolling passes: Control the reduction rate of passes F1 to F3 to be ≤35%, and the reduction rate of passes F4 to F7 to be ≤15%.

[0007] Preferably, the control of the superheat of the intermediate ladle temperature is achieved through closed-loop control via an online temperature measurement and automatic cooling material addition system.

[0008] Preferably, the method for controlling the composition of molten steel involves controlling the As and Sb content in molten iron and scrap steel from the source, using LF refining and deep desulfurization treatment, and controlling the argon blowing time and flow rate. The molten steel composition is: N≤50ppm, S≤0.015%, As≤50ppm, Sb≤0.01%, and the Ti content is controlled to be 0.012%~0.035% according to the target inclusion type. Fine and controllable inclusions are generated by using a reasonable ratio of Ti to N.

[0009] Preferably, the superheat control specifically includes achieving closed-loop control of the ladle temperature superheat with an accuracy of ±5℃ through an online temperature measurement and automatic cooling material addition system.

[0010] Preferably, in S2, the slab is heated to 1200°C or 1250°C to generate iron oxide scale at high temperature, thereby eliminating defects in thin-layer castings.

[0011] Preferably, in S2: the time the slab is in the furnace is controlled to be 150 min or 180 min.

[0012] Preferably, in S4, the final rolling temperature is 875°C, or 880°C, or 885°C, or 890°C, or 895°C, or 900°C.

[0013] Preferably, in S4, the winding temperature is 580°C, 585°C, 590°C, 595°C, 600°C, 605°C, or 610°C.

[0014] Preferably, in S5, the cooling time of the unrolled roll is 120 minutes.

[0015] The term "high-end strip steel" refers to strip steel products used in the fields of automotive lightweighting and high-end home appliances, which have stringent requirements for comprehensive indicators such as surface quality, fatigue life, and corrosion resistance.

[0016] The advantages and technical effects of this invention are: This invention significantly reduces surface defects caused by press-in metal inclusions and iron oxide scale by coordinating the entire process from the source of inclusion formation (steel composition, superheat) to the rolling process (temperature regime, reduction rate, roll management).

[0017] This invention improves the temperature uniformity at the beginning and end of the furnace by controlling the time the slab spends in the furnace, thereby reducing pitting defects at the beginning and end.

[0018] This invention optimizes the cooling and grinding conditions of the rolls to ensure the integrity of the oxide film on the rolls, extend the roll life, and improve the surface uniformity of the strip steel. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A first flowchart of a preferred embodiment of the present invention is shown; Figure 2 A second flowchart of a preferred embodiment of the present invention is shown. Detailed Implementation

[0021] To make the above-mentioned objectives, control system design, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0022] Please see Figure 1 He Tu, a high-end strip steel quality method based on inclusion indentation control, includes: S1. Steel composition and superheat control: control the N in the molten steel to ≤50ppm, S to ≤0.015%, As to ≤50ppm, Sb to ≤0.01%, and control the Ti content to 0.012%~0.035% according to the target inclusion type. At the same time, control the superheat control accuracy of the tundish temperature to ±5℃. In the process of controlling the composition and superheat of molten steel, precise control of key elements in the molten steel is necessary to ensure the quality of high-end strip steel. Specifically, the nitrogen content in the molten steel should be controlled to no more than 50 ppm, the sulfur content no more than 0.015%, the arsenic content no more than 50 ppm, and the antimony content no more than 0.01%. Meanwhile, depending on the type of target inclusions, the titanium content must be strictly maintained within the range of 0.012% to 0.035%. Furthermore, the superheat control accuracy of the tundish temperature must be within ±5℃ to optimize casting performance and reduce defect generation.

[0023] S2. Slab Heating Control: To ensure efficient and uniform slab heating, the slab time in the furnace must be strictly controlled to 150-180 minutes to prevent overheating or energy waste. Simultaneously, the slab heating temperature range should be 1200℃~1250℃ to utilize the high temperature to generate iron oxide scale, eliminating thin-layer casting defects. Furthermore, the furnace temperature and slab position should be monitored regularly to ensure stable heating parameters and avoid quality fluctuations.

[0024] S3. Pre-finishing cooling control: A cooling water device for the intermediate billet is installed at the finish mill inlet. By intelligently adjusting the flow rate and spray pattern of the cooling water, precise management of the intermediate billet temperature is achieved, ensuring that the finish mill inlet temperature remains stable within the ideal range of 940℃~1000℃. This control step optimizes the material microstructure and properties, improves the mechanical properties and surface finish of the final product, and effectively prevents the negative impact of temperature fluctuations on roll life and production efficiency.

[0025] S4. Final rolling and coiling temperature control: Control the final rolling temperature to 875℃~900℃ and the coiling temperature to 580℃~610℃. In the high-end strip steel rolling process, final rolling and coiling temperature control are critical process steps. The final rolling temperature needs to be strictly controlled between 875℃ and 900℃ to refine the supercooled austenite grains and improve the strength and toughness of the material. The coiling temperature should be maintained within the range of 580℃ to 610℃ to ensure the stability of the phase transformation process and avoid excessive hardening or softening, thereby optimizing the formability of the product. Through automated heating systems and dynamic cooling regulation, precise management of temperature parameters can be achieved, ensuring that the final sheet material meets the requirements for microstructure uniformity and mechanical properties.

[0026] S5. Roll Cooling and Grinding Control: To ensure roll quality and safety, rolls must be fully cooled after removal from the mill. The cooling time should be no less than 120 minutes to ensure uniform release of internal thermal stress. During the cooling process, the roll surface temperature should be monitored periodically using an infrared thermometer. Grinding can only proceed once the temperature has stabilized below 40°C. Before grinding, operators must also check the roll surface for cracks or damage and confirm that the grinding equipment parameters meet the process requirements. The entire process must strictly adhere to safety procedures, and cooling time and temperature data must be recorded for quality traceability and optimization.

[0027] S6. Reduction rate distribution of finishing rolling passes: Control the reduction rate of passes F1 to F3 to be ≤35%, and the reduction rate of passes F4 to F7 to be ≤15%.

[0028] To better understand the technical solution of this invention, the following is a non-limiting description: The control of the superheat of the tundish temperature is achieved by continuously monitoring temperature data in real time through an online temperature measurement system, and by automatically adjusting the amount of cold material added based on the temperature feedback signal through an automatic cold material addition system. This creates an efficient closed-loop control mechanism to ensure that the temperature is accurately maintained within the set superheat range, thereby improving the stability of the tundish temperature.

[0029] The control of the molten steel composition specifically includes: By controlling the As and Sb content in molten iron and scrap steel at the source, LF refining and deep desulfurization treatment, and controlling the argon blowing time and flow rate, the steel composition is: N≤50ppm, S≤0.015%, As≤50ppm, Sb≤0.01%, and the Ti content is controlled at 0.012%~0.035% according to the target inclusion type. The reasonable ratio of Ti to N is used to generate fine and controllable inclusions.

[0030] The superheat control specifically includes achieving closed-loop control of the ladle temperature superheat with an accuracy of ±5℃ through an online temperature measurement and automatic cooling material addition system.

[0031] In S2, the slab is heated to a temperature of 1200℃ or 1250℃.

[0032] In S2: control the slab time in the furnace to be 150 min or 180 min.

[0033] In S4: the final rolling temperature is 875℃, or 880℃, or 885℃, or 890℃, or 895℃, or 900℃.

[0034] In S4: the winding temperature is 580℃, or 585℃, or 590℃, or 595℃, or 600℃, or 605℃, or 610℃.

[0035] In S5: The cooling time for the rolls after rolling is 120 minutes.

[0036] The term "high-end strip steel" refers to strip steel products used in the fields of automotive lightweighting and high-end home appliances, which have stringent requirements for comprehensive indicators such as surface quality, fatigue life, and corrosion resistance.

[0037] Specific application examples: 1. The photovoltaic bracket uses TS450, and the finished product specifications are 3.5*1500 mm.

[0038] S1 chemical composition: C: 0.16~0.19%, Si: 0.15~0.25%, Mn: 0.90~1.00%, P≤0.015%, S≤0.010%, N≤50ppm, As≤35ppm, Sb≤0.008%, Ti0.015~0.025%.

[0039] S2 heating regime: furnace time 150-180 min, soaking zone heating temperature 1200-1220℃; The entry temperature of the S3 finishing mill is controlled at 940-960℃, the finishing rolling temperature is 900℃, and the coiling temperature is 610℃. S4 finishing mill reduction rates for each pass: F1–F3: 35%, 32%, 30%; F4–F7: 15%, 13%, 11%, 8%. Key improvement: The surface defect rate of the strip steel was reduced from 0.8% to 0.09%.

[0040] 2. Cold-rolled material SPHC-B for pickling and direct plating, finished product specifications 3.0*1265 mm.

[0041] S1 chemical composition: C: 0.03~0.106%, Si: 0.01~0.03%, Mn: 0.15~0.25%, P≤0.015%, S≤0.010%, N≤40ppm, As≤35ppm, Sb≤0.008%, Ti: 0.015~0.025%, B: 0.008-0.030%.

[0042] S2 heating regime: furnace time 150-180 min, soaking zone heating temperature 1220-1250℃; The entry temperature of the S3 finishing mill is controlled at 940-960℃, the finishing rolling temperature is 880℃, and the coiling temperature is 600℃. S4 finishing mill reduction rates for each pass: F1–F3: 35%, 32%, 30%; F4–F7: 15%, 14%, 12%, 10%. Key improvement: The pitting defect rate at the beginning and end of the strip was reduced from 0.55% to 0.12%.

[0043] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the quality of high-end strip steel based on inclusion pressing control, characterized in that, include: S1. Steel composition and superheat control: control the N in the molten steel to ≤50ppm, S to ≤0.015%, As to ≤50ppm, Sb to ≤0.01%, and control the Ti content to 0.012%~0.035% according to the target inclusion type. At the same time, control the superheat control accuracy of the tundish temperature to ±5℃. S2. Slab heating control: Control the slab time in the furnace to 150-180 min, and the slab heating temperature range is 1200℃~1250℃; S3. Cooling control before finishing milling: Install intermediate billet cooling water device at the entrance of finishing mill to control the temperature at the entrance of finishing mill to 940℃~1000℃; S4. Final rolling and coiling temperature control: Control the final rolling temperature to 875℃~900℃ and the coiling temperature to 580℃~610℃. S5. Roll cooling and grinding control: The cooling time of the rolls after the mill is ≥120min. Grinding is carried out after the surface temperature of the rolls drops to below 40℃. S6. Reduction rate distribution of finishing rolling passes: Control the reduction rate of passes F1 to F3 to be ≤35%, and the reduction rate of passes F4 to F7 to be ≤15%.

2. The high-end strip steel quality method based on inclusion pressing control according to claim 1, characterized in that, The control of the superheat of the intermediate ladle temperature is achieved through closed-loop control via online temperature measurement and automatic cooling material addition system.

3. The high-end strip steel quality method based on inclusion pressing control according to claim 1, characterized in that, The control of the molten steel composition specifically includes: N≤50ppm, S≤0.015%, As≤50ppm, Sb≤0.01%, and the Ti content is controlled at 0.012%~0.035% according to the target inclusion type, so as to generate fine and controllable inclusions by using a reasonable ratio of Ti to N.

4. The high-end strip steel quality method based on inclusion pressing control according to claim 1, characterized in that, The superheat control specifically includes closed-loop control through an online temperature measurement and automatic cooling material addition system, with the superheat control accuracy of the tundish temperature being ±5℃.

5. The high-end strip steel quality method based on inclusion pressing control according to claim 1, characterized in that, In S2, the slab is heated to a temperature of 1200℃ or 1250℃.

6. The high-end strip steel quality method based on inclusion pressing control according to claim 1, characterized in that, In S2: control the slab time in the furnace to be 150 min or 180 min.

7. The high-end strip steel quality method based on inclusion pressing control according to claim 1, characterized in that, In S4: the final rolling temperature is 875℃, or 880℃, or 885℃, or 890℃, or 895℃, or 900℃.

8. The high-end strip steel quality method based on inclusion pressing control according to claim 1, characterized in that: In S4: the winding temperature is 580℃, or 585℃, or 590℃, or 595℃, or 600℃, or 605℃, or 610℃.

9. The high-end strip steel quality method based on inclusion pressing control according to claim 1, characterized in that, In S5: The cooling time for the rolls after rolling is 120 minutes.

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