Preparation method of ultra-thin grinding-free super duplex stainless steel coil

Abstract

The invention relates to the technical field of duplex stainless steel, in particular to a preparation method of an ultrathin grinding-free super duplex stainless steel coil. S2, continuous casting; s3, hot rolling; and S4, follow-up treatment is carried out, the casting temperature is controlled, a double-slag technology is used, casting powder components are designed, grinding-free direct hot feeding rolling is achieved, and the production cost and time consumption are reduced. And meanwhile, through alloy formula design, such as controlling the proportion of elements such as sulfur, nickel, molybdenum and nitrogen, precipitation of a sigma phase is effectively inhibited, precipitation sensitivity of the sigma phase is reduced, safe rolling can be carried out within the interval of 800-950 DEG C, and therefore rolling of the ultra-thin specification of 3 mm or below is achieved, and the surface quality, the size precision and the production efficiency of a product are improved.

Description

Technical Field

[0001] The invention relates to the technical field of duplex stainless steel, and in particular to a method for preparing an ultra-thin grinding-free super duplex stainless steel coil. Background Art

[0002] Super duplex stainless steel has high strength and high corrosion resistance and is used in harsh environments. Due to the characteristics of the product, it is difficult to manufacture. The surface quality of the continuous casting billet is poor, and there are often defects such as cracks and scars. The billet needs to be peeled and ground before hot rolling. In addition, the thickness of hot rolling is usually more than 3mm, and rolling of ultra-thin steel coils below 3mm has not been achieved.

[0003] In the prior art, a duplex stainless steel coil and its manufacturing method with publication number "CN113210420A" has a production process of the coil as follows: electric furnace → converter → refining furnace → continuous casting → billet grinding → hot rolling → intermediate billet → billet grinding → hot rolling. The billet needs to be ground before hot rolling, and it needs to be hot rolled twice and ground twice, which wastes a lot of cost and time. The finished thickness of the coil is "3.0-10.0mm", which means that the hot rolling thickness range is limited, and ultra-thin material rolling below 3mm cannot be achieved.

[0004] In the prior art, a method for reducing hot rolling cracks of super duplex stainless steel with the publication number "CN115874017A" mentions that the surface defects of the super duplex stainless steel ingot are first ground before hot rolling, indicating that the need for grinding the steel billet is a major problem that restricts production. The super duplex stainless steel ingot is hot rolled to obtain super duplex stainless steel plates or bars, indicating that it is suitable for steel plates and bars, but not for steel coils. Because steel coils need to be coiled, coiling has large stress and is prone to problems such as strip breakage and brittle fracture, so the process of a method for reducing hot rolling cracks of super duplex stainless steel is not suitable for steel coils.

[0005] In order to solve these problems, a method for preparing ultra-thin grinding-free super duplex stainless steel coil is proposed. The invention solves the problem of steel billet defects by optimizing the continuous casting process, and can achieve grinding-free direct hot rolling. Secondly, the precipitation of σ is suppressed by alloy formula design, and the ultra-thin rolling technology is realized, which effectively reduces the cost and improves the production efficiency. The ultra-thin rolling is realized, and the effect of hot rolling replacing cold-rolled steel coil can be achieved, and its production cost is more competitive. Summary of the invention

[0006] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for preparing an ultra-thin grinding-free super duplex stainless steel coil.

[0007] To achieve the above object, the present invention provides the following technical solutions: A method for preparing an ultra-thin grinding-free super duplex stainless steel coil comprises the following preparation steps: S1. Steelmaking: The alloy is smelted using an electric arc furnace (EAF) and argon oxygen decarburization (AOD). Trace elements are added using the LF process outside the furnace. Then, 1.8-2.2 m / t of silicon-calcium wire is slowly and evenly fed into the molten steel through a wire feeder. Refining is continued for 5-10 minutes. Magnesium particles are evenly sprayed into the molten steel through a blowing device using argon as a carrier. The blowing pressure is controlled at 0.3-0.4 MPa. The outlet temperature of the molten steel is controlled at 1500-1600°C. The molten steel is sent to the continuous casting platform and allowed to stand for 18-20 minutes before pouring. S2. Continuous casting: It is carried out in a straight arc slab continuous casting machine, and the billet pulling speed is controlled at 1.4-1.5m / min, the secondary cooling water ratio is 0.3-0.4L / kg, the pouring temperature is controlled at 1540-1560℃, and the temperature fluctuation of the tundish is ±5℃; the double slag technology is used to control the centering deviation of the immersion nozzle to be less than 3mm, and the insertion depth is 80-120mm; the protective slag composition is designed, the cooling water flow and temperature of the crystallizer are adjusted, the taper of the narrow copper plate is controlled, and a non-sinusoidal vibration curve is used; the number and gap of the foot rollers are set; electromagnetic stirring devices are set in the continuous casting crystallizer and the solidification end, and the stirring frequencies are 2-10Hz and 0.5-5Hz respectively, to obtain the billet after continuous casting; S3. Hot rolling: Cut the continuous casting billet and send it to the hot rolling heating furnace, and control the furnace time at 100-150min; control the billet extraction temperature at 1210-1220℃; carry out high-pressure water dephosphorization after the billet is extracted, and control the start rolling temperature of rough rolling and finishing rolling; implement multiple rolling to achieve the target thickness; use small-diameter work rolls to finish rolling and coiling to obtain hot-rolled coils, and each rack of finishing rolling adopts a mineral oil lubricating oil system; set the roll shifting amount of each rack; control the strip threading speed and strip cooling to obtain the strip after coiling; S4. Subsequent processing: The coiled strip is water-cooled to room temperature and sent to the annealing and pickling production line; after annealing and pickling, the white coil has no surface defects, no cracks on the edges, and no broken strips; the surface roughness of the strip is controlled to 0.1-0.4um, and finally an ultra-thin grinding-free super duplex stainless steel coil is obtained; Among them, the raw material composition of ultra-thin grinding-free super duplex stainless steel coil includes alloy components and trace elements. In terms of mass percentage, the alloy components include: C≤0.03%; Si≤0.8%; Mn≤1.2%; P≤0.035%; S≤0.02%; Ni: 14.5%-20.5%; Cr: 66.7%-72.7%; Mo: 9-12.8%; Cu≤0.5%, N: 0.24%-0.32%; Trace elements include: B: 0.0005%-0.0010%; Zr: 0.002%-0.005%; Nb: 0.003%-0.01%.

[0008] Preferably, in step S2, the protective slag comprises, by weight percentage, the following components: SiO 2 :29-36%, CaO: 27-34%, MgO: 0.1-2.2%, Al 2 O 3 :4-7%,Fe 2 O 3 <1.4%, MnO 2 :0.8-3.0%,F:7-11%,Na 2 O: 9-13%, Li 2 O: 0.5-2.5%, modified particles: 2.5-10%.

[0009] Preferably, the mass ratio of potassium titanate to lithium carbonate in the modified particles is 1:1.2-3.

[0010] Preferably, in step S2, the parameters of the protective slag during the continuous casting process are: basicity is 0.8-1.5; viscosity is 0.5-1.0; softening point is 980-1070°C; melting point is 1000-1100°C; and flow point is 1070-1190°C.

[0011] Preferably, in step S2, the water flow rate of the narrow side cooling water of the crystallizer is 350L / min, the water flow rate of the wide side is 2500L / min, the water inlet temperature is 20-25°C, the inlet and outlet water temperature difference is controlled at 15-16°C, the taper of the narrow side copper plate of the crystallizer is 10-11, the crystallizer adopts a non-sinusoidal vibration curve, the amplitude is 6.0-6.5mm, the vibration frequency is 165-170HZ, the negative slip time is 0.11-0.13s, and the narrow side foot rollers of the crystallizer are set to 8 foot rollers with a foot roller gap of 1-2mm.

[0012] Preferably, in step S3, the thickness of the steel billet cut is 220 mm and the width is 1000-1600 mm; the rough rolling start temperature of the steel billet high-pressure water dephosphorization is 1190-1210°C, a total of 9 rolling passes are implemented, and the rolling target thickness is 10-20 mm.

[0013] Preferably, in step S3, the billet finishing rolling start temperature is 1000-1080°C, eight stands are used for continuous rolling, the final rolling temperature is 850-950°C, and the billet is rolled to a target thickness of 1.5-2.8mm; the finishing rolling small roll diameter working rolls are F6-F8 rolls with a diameter of 400-450mm.

[0014] Preferably, mineral oil lubricant is used in each rack of steel billet finishing rolling, and the friction coefficient is required to be 0.1-0.2; wherein, mineral lubricant is used in each rack of finishing rolling, and the friction coefficient is required to be 0.1-0.2, wherein, the lubricant flow rate of F1 finishing rolling rack is controlled at 0.16-0.17L / min, the lubricant flow rate of F2 finishing rolling rack is controlled at 0.18-0.19L / min, the lubricant flow rate of F3 finishing rolling rack is controlled at 0.20-0.21L / min, the lubricant flow rate of F4 finishing rolling rack is controlled at 0.21-0.22L / min, and the lubricant flow rate of F5-F8 finishing rolling racks is controlled at 0.16-0.17L / min, the lubricant flow rate of F1 finishing rolling rack is controlled at 0.18-0.19L / min, the lubricant flow rate of F2 finishing rolling rack is controlled at 0.18-0.19L / min, the lubricant flow rate of F3 finishing rolling rack is controlled at 0.20-0.21L / min, the lubricant flow rate of F4 finishing rolling rack is controlled at 0.21-0.22L / min, and the lubricant flow rate of F5-F8 finishing rolling racks is controlled at 0.16-0.17 ... and the lubr The speed of each finishing mill is 0.16-0.17L / min; the roller shifting amount of each finishing mill stand is set as follows: the lateral movement of the F1 finishing mill stand is 41.040mm, the lateral movement of the F2 finishing mill stand is 19.786mm, the lateral movement of the F3 finishing mill stand is 21.880mm, the lateral movement of the F4 finishing mill stand is 26.006mm, the lateral movement of the F5 finishing mill stand is -0.002mm, the lateral movement of the F6 finishing mill stand is 55.181mm, the lateral movement of the F7 finishing mill stand is 28.866mm, and the lateral movement of the F8 finishing mill stand is 32.005mm.

[0015] Preferably, the strip threading speed of the F8 finishing mill is set at 6-12m / s, and the pressure belt fan is started immediately after the strip exits the F8 finishing mill. The fan is behind the F8 finishing mill, with an air volume of 40-50m³ / S and an air pressure of 800-900Pa.

[0016] Preferably, in step S3, the roller spacing at the finishing rolling exit is set to 260-300mm, the finishing rolling exit is a layer cooling zone, and when the strip thickness is 1.5-1.8mm, its head 40-50m is not sprayed with water for cooling, and when the strip thickness is 1.8-2.8, its head 25-30m is not sprayed with water for cooling.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention solves the problem of steel billet defects by optimizing the continuous casting process, and realizes direct hot rolling without grinding, which greatly reduces production costs and time consumption. Through alloy formula design, the precipitation of σ phase is suppressed, and the rolling technology of ultra-thin specifications below 3mm is realized, which broadens the application range of products. The step of steel billet grinding is eliminated, the production process is reduced, the production efficiency is improved, and the cost is reduced. By optimizing the process, the effect of hot rolling replacing cold-rolled steel coils is achieved, and its production cost is more competitive.

[0018] 2. Silicon-calcium wire is added during the refining process. Calcium can combine with impurity elements such as sulfur and oxygen in the molten steel to form stable inclusions such as calcium sulfide (CaS) and calcium oxide (CaO). The morphology and distribution of these inclusions are improved, changing from long strips or chains to spherical or nearly spherical, reducing the cutting effect of inclusions on the steel matrix, thereby improving the plasticity, toughness and fatigue resistance of the steel. At the same time, silicon-calcium wire can also improve the fluidity of the molten steel, which is conducive to the floating removal of inclusions and further improves the purity of the steel. Magnesium particles have the functions of deoxidation, desulfurization and grain refinement in the molten steel. Inclusions such as magnesium oxide (MgO) and magnesium sulfide (MgS) generated by the reaction of magnesium with oxygen and sulfur can serve as heterogeneous nucleation cores, promote the refinement of austenite grains, and improve the strength and toughness of steel. In addition, magnesium can also reduce the surface tension of molten steel, improve the surface quality of the ingot, reduce the generation of defects such as surface cracks and depressions, and help to achieve direct hot rolling without grinding.

[0019] 3. The electromagnetic stirring in the crystallizer of the present invention can make the composition and temperature of the molten steel more uniform, refine the solidification structure of the ingot, reduce defects such as segregation and shrinkage, and further reduce the possibility of cracks and scars on the surface of the ingot, improve the quality of the ingot, and ensure the realization of direct hot rolling without grinding. The electromagnetic stirring at the end of solidification helps to improve the center segregation of the ingot and improve the overall performance of the material.

[0020] 4. By controlling the alloy composition and trace elements, and optimizing the hot rolling process, the surface quality of the hot-rolled coil is significantly improved, with no defects, no cracked edges, and no broken strips, meeting high-standard application requirements. By controlling the sulfur element within 0.001%, the thermoplasticity is improved and the occurrence of hot cracks is reduced. By reasonably controlling the proportions of nickel, molybdenum, nitrogen and other elements, the sensitivity of σ phase precipitation is reduced, allowing safe rolling in the range of 800-950℃, avoiding edge cracks and broken strips.

[0021] 5. The present invention adds modified particles to the protective slag, which can improve the crystallization temperature and crystallization ability of the protective slag, so that the protective slag forms a more stable solid slag film between the crystallizer wall and the surface of the ingot. This solid slag film has good lubrication and heat insulation properties, can effectively reduce the friction between the ingot and the crystallizer wall, reduce the friction heat on the surface of the ingot, and prevent defects such as thermal cracks and scratches on the surface of the ingot. At the same time, the stable slag film can also transfer heat evenly, which is beneficial to the solidification process of the ingot and improves the surface quality and internal quality of the ingot. The modified particles also play a role in reducing the melting point and viscosity. During the continuous casting process, the protective slag with a lower melting point and viscosity can better flow into the gap between the crystallizer and the ingot, forming a continuous and uniform liquid slag film, providing a good lubrication effect, reducing the tensile stress on the surface of the ingot, and preventing cracks. At the same time, the modified particles can also promote the melting and uniform distribution of other components in the protective slag, optimize the overall performance of the protective slag, further improve the surface quality of the ingot, reduce the incidence of surface defects, and provide high-quality billets for subsequent hot rolling processes.

[0022] 6. The present invention uses working rolls with small roll diameters and reasonable roll shifting settings to better control the strip difference and shape, thereby improving the dimensional accuracy of the product. By reasonably distributing the lubricating oil flow, the load of each frame is balanced, the wear and tear of the rolls is reduced, and the surface quality and shape of the product are guaranteed. By setting a reasonable threading speed and air volume and pressure, the flying of ultra-thin materials during the rolling process is prevented, and the generation of scrap steel is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a process flow chart of the preparation of ultra-thin grinding-free super duplex stainless steel coil. DETAILED DESCRIPTION

[0024] The present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] See also Figure 1 , the present invention provides a technical solution: A method for preparing an ultra-thin grinding-free super duplex stainless steel coil. The raw material components of the ultra-thin grinding-free super duplex stainless steel coil include alloy components and trace elements. In terms of mass percentage, the alloy components include: C≤0.03%; Si≤0.8%; Mn≤1.2%; P≤0.035%; S≤0.02%; Ni: 14.5%-20.5%; Cr: 66.7%-72.7%; Mo: 9-12.8%; Cu≤0.5%, N: 0.24%-0.32%; Trace elements include: B: 0.0005%-0.0010%; Zr: 0.002%-0.005%; Nb: 0.003%-0.01%; Among them, S is optimally controlled within 0.02% to improve thermoplasticity, Ni: 14.5%-20.5% to reduce the sensitivity of σ precipitation; Mo: 9-12.8% to reduce the sensitivity of σ precipitation; N: 0.24%-0.32% to reduce the sensitivity of σ precipitation. High N is prone to BN precipitation, which makes the steel billet prone to defects and requires grinding, so N: 0.24%-0.32%, B < 0.0010%; but without adding B, its thermoplasticity is not good and it is easy to produce hot cracks, so B: 0.0005%-0.0010%; Zr: 0.002%-0.005%; Nb: 0.003%-0.01% is used to inhibit the precipitation rate of σ and reduce the precipitation temperature of σ, so as to achieve the production purpose of hot-rolled ultra-thin materials. Example 1 S1. Steelmaking: The alloy is melted using an electric arc furnace (EAF) and argon oxygen decarburization (AOD). Trace elements are added using the LF process outside the furnace. Then, 1.8 m / t of silicon-calcium wire is slowly and evenly fed into the molten steel through a wire feeder. Refining is continued for 5 minutes. Magnesium particles are evenly sprayed into the molten steel through a blowing device using argon as a carrier. The blowing pressure is controlled at 0.3 MPa. The outlet temperature of the molten steel is controlled at 1500°C. The molten steel is sent to the continuous casting platform and allowed to stand for 18 minutes before pouring. S2. Continuous casting: It is carried out in a straight arc slab continuous casting machine, and the billet pulling speed is controlled at 1.4m / min, the secondary cooling water ratio is 0.3L / kg, the pouring temperature is controlled at 1540℃, and the temperature fluctuation of the tundish is ±5℃; the double slag technology is used to control the centering deviation of the immersion nozzle to be less than 3mm, and the insertion depth is 80mm; the protective slag composition is designed, the cooling water flow and temperature of the crystallizer are adjusted, the taper of the narrow copper plate is controlled, and a non-sinusoidal vibration curve is used; the number and gap of the foot rollers are set; electromagnetic stirring devices are set at the continuous casting crystallizer and the solidification end, and the stirring frequencies are 2Hz and 0.5Hz respectively, to obtain the billet after continuous casting; Among them, the protective slag includes the following components by mass percentage: SiO 2 :32%, CaO: 29%, MgO: 1.1%, Al 2 O 3 :5%,Fe 2 O 3 :1.2%, MnO2 :1.8%,F:8%,Na 2 O: 12%, Li 2 O: 1.5%, modified particles: 8.4%, wherein the mass ratio of potassium titanate to lithium carbonate in the modified particles is 1:1.2; The water flow rate of the narrow side of the crystallizer cooling water is 350L / min, the water flow rate of the wide side is 2500L / min, the water inlet temperature is 20℃, the inlet and outlet temperature difference is controlled at 15℃, the taper of the narrow side copper plate of the crystallizer is 10, the crystallizer adopts a non-sinusoidal vibration curve, the amplitude is 6.0mm, the vibration frequency is 165HZ, the negative slip time is 0.11s, and the narrow side foot roller of the crystallizer is set to 8 foot rollers, and the foot roller gap is 1mm; S3. Hot rolling: Cut the continuous casting billet and send it to the hot rolling heating furnace, and control the furnace time at 100 minutes; control the billet extraction temperature at 1210℃; carry out high-pressure water dephosphorization after the billet is extracted, and control the start rolling temperature of rough rolling and finishing rolling; implement multiple rolling to achieve the target thickness; use small-diameter work rolls to finish rolling and coiling to obtain hot-rolled coils, and each rack of finishing rolling adopts a mineral oil lubricating oil system; set the roll shifting amount of each rack; control the strip threading speed and strip cooling to obtain the strip after coiling; The billet was cut to a thickness of 220 mm and a width of 1000 mm. The rough rolling temperature of the billet for high-pressure water dephosphorization was 1190 ° C, with a total of 9 rolling passes, and the target rolling thickness was 10 mm. The billet finishing rolling temperature was 1000 ° C, with eight stands continuously rolled, and the final rolling temperature was 850 ° C, with the target thickness of 1.5 mm. The working rolls of the finishing rolling with small roll diameters were F6 rolls with a diameter of 400 mm. Among them, each frame of steel billet finishing rolling uses mineral oil lubricant, and the friction coefficient is required to be 0.1; Among them, each frame of finishing rolling uses mineral lubricant, and the friction coefficient is required to be 0.1, among which, the lubricating oil flow rate of F1 finishing rolling frame is controlled at 0.16L / min, the lubricating oil flow rate of F2 finishing rolling frame is controlled at 0.18L / min, the lubricating oil flow rate of F3 finishing rolling frame is controlled at 0.20L / min, the lubricating oil flow rate of F4 finishing rolling frame is controlled at 0.21L / min, and the lubricating oil flow rate of F5-F8 finishing rolling frames is controlled at 0.16L / min; The roll shifting amount of each rolling stand is set as follows: the lateral movement of the F1 finishing stand is 41.040mm, the lateral movement of the F2 finishing stand is 19.786mm, the lateral movement of the F3 finishing stand is 21.880mm, the lateral movement of the F4 finishing stand is 26.006mm, the lateral movement of the F5 finishing stand is -0.002mm, the lateral movement of the F6 finishing stand is 55.181mm, the lateral movement of the F7 finishing stand is 28.866mm, and the lateral movement of the F8 finishing stand is 32.005mm; Among them, the strip threading speed of F8 finishing mill is set at 6m / s. The pressure belt fan is started immediately after the strip exits F8 finishing mill. The fan is behind F8 finishing mill, with an air volume of 40m³ / S and an air pressure of 800Pa. Among them, the roller spacing at the finishing exit is set to 260mm, and the finishing exit is a layer cooling zone. When the strip thickness is 1.5mm, the head 40m is not sprayed with water for cooling, and when the strip thickness is 1.8, the head 25m is not sprayed with water for cooling; S4. Subsequent processing: The coiled strip is water-cooled to room temperature and sent to the annealing and pickling production line; after annealing and pickling, the white coil has no surface defects, no cracks on the edges, and no broken strips; the surface roughness of the strip is controlled to 0.1um, and finally an ultra-thin, grinding-free super duplex stainless steel coil is obtained.

[0026] Example 2 S1. Steelmaking: The alloy is melted using an electric arc furnace (EAF) and argon oxygen decarburization (AOD). Trace elements are added using the LF process outside the furnace. Then, 2.2 m / t of silicon-calcium wire is slowly and evenly fed into the molten steel through a wire feeder. Refining is continued for 10 min. Magnesium particles are evenly sprayed into the molten steel through a blowing device using argon as a carrier. The blowing pressure is controlled at 0.4 MPa. The outlet temperature of the molten steel is controlled at 1600°C. The molten steel is sent to the continuous casting platform and allowed to stand for 20 min before pouring. S2. Continuous casting: It is carried out in a straight arc slab continuous casting machine, and the billet pulling speed is controlled at 1.5m / min, the secondary cooling water ratio is 0.4L / kg, the pouring temperature is controlled at 1560℃, and the temperature fluctuation of the tundish is ±5℃; the double slag technology is used to control the centering deviation of the immersion nozzle to be less than 3mm, and the insertion depth is 120mm; the protective slag composition is designed, the cooling water flow and temperature of the crystallizer are adjusted, the taper of the narrow copper plate is controlled, and a non-sinusoidal vibration curve is used; the number and gap of the foot rollers are set; electromagnetic stirring devices are set in the continuous casting crystallizer and the solidification end, and the stirring frequencies are 10Hz and 5Hz respectively, to obtain the billet after continuous casting; Among them, the protective slag includes the following components by mass percentage: SiO 2 :30%, CaO: 30%, MgO: 2.2%, Al 2 O 3 :7%,Fe 2 O 3 :1.4%, MnO 2 :3.0%,F:8%,Na 2 O: 10%, Li 2 O: 2.5%, modified particles: 5.9%, wherein the mass ratio of potassium titanate to lithium carbonate in the modified particles is 1:3; The water flow rate of the narrow side of the crystallizer cooling water is 350L / min, the water flow rate of the wide side is 2500L / min, the water inlet temperature is 25℃, the inlet and outlet temperature difference is controlled at 16℃, the taper of the narrow side copper plate of the crystallizer is 11, the crystallizer adopts a non-sinusoidal vibration curve, the amplitude is 6.5mm, the vibration frequency is 170HZ, the negative slip time is 0.13s, and the narrow side foot roller of the crystallizer is set to 8 foot rollers, and the foot roller gap is 2mm; S3. Hot rolling: Cut the continuous casting billet and send it to the hot rolling heating furnace, and control the furnace time at 150 minutes; control the billet extraction temperature at 1220℃; carry out high-pressure water dephosphorization after the billet is extracted, and control the start rolling temperature of rough rolling and finishing rolling; implement multiple rolling to achieve the target thickness; use small-diameter work rolls to finish rolling and coiling to obtain hot-rolled coils, and each rack of finishing rolling adopts a mineral oil lubricating oil system; set the roll shifting amount of each rack; control the strip threading speed and strip cooling to obtain the strip after coiling; The billet was cut to a thickness of 220 mm and a width of 1600 mm. The rough rolling temperature of the billet for high-pressure water dephosphorization was 1210 ° C, with a total of 9 rolling passes, and the target rolling thickness was 20 mm. The billet finishing rolling temperature was 1080 ° C, with eight stands continuously rolled, and the final rolling temperature was 950 ° C, with the target thickness of 2.8 mm. The working rolls of the finishing rolling with a small roll diameter were F8 rolls with a diameter of 450 mm. Among them, each frame of steel billet finishing rolling uses mineral oil lubricant, and the friction coefficient is required to be 0.2; Among them, each frame of finishing rolling uses mineral lubricant, and the friction coefficient is required to be 0.2, among which, the lubricating oil flow rate of F1 finishing rolling frame is controlled at 0.17L / min, the lubricating oil flow rate of F2 finishing rolling frame is controlled at 0.19L / min, the lubricating oil flow rate of F3 finishing rolling frame is controlled at 0.21L / min, the lubricating oil flow rate of F4 finishing rolling frame is controlled at 0.22L / min, and the lubricating oil flow rate of F5-F8 finishing rolling frames is controlled at 0.17L / min; The roll shifting amount of each rolling stand is set as follows: the lateral movement of the F1 finishing stand is 41.040mm, the lateral movement of the F2 finishing stand is 19.786mm, the lateral movement of the F3 finishing stand is 21.880mm, the lateral movement of the F4 finishing stand is 26.006mm, the lateral movement of the F5 finishing stand is -0.002mm, the lateral movement of the F6 finishing stand is 55.181mm, the lateral movement of the F7 finishing stand is 28.866mm, and the lateral movement of the F8 finishing stand is 32.005mm; Among them, the strip threading speed of F8 finishing mill is set at 12m / s. The pressure belt fan is started immediately after the strip exits F8 finishing mill. The fan is behind F8 finishing mill, with an air volume of 50m³ / S and an air pressure of 900Pa. Among them, the roller spacing at the finishing exit is set to 300mm, and the finishing exit is a layer cooling zone. When the strip thickness is 1.8mm, the head 50m is not sprayed with water for cooling, and when the strip thickness is 2.8, the head 30m is not sprayed with water for cooling; S4. Subsequent processing: The coiled strip is water-cooled to room temperature and sent to the annealing and pickling production line; after annealing and pickling, the white coil has no surface defects, no cracks on the edges, and no broken strips; the surface roughness of the strip is controlled to 0.4um, and finally an ultra-thin, grinding-free super duplex stainless steel coil is obtained.

[0027] Example 3 S1. Steelmaking: The alloy is melted using an electric arc furnace (EAF) and argon oxygen decarburization (AOD). Trace elements are added using the LF process outside the furnace. Then, 2.2 m / t of silicon-calcium wire is slowly and evenly fed into the molten steel through a wire feeder. Refining is continued for 10 min. Magnesium particles are evenly sprayed into the molten steel through a blowing device using argon as a carrier. The blowing pressure is controlled at 0.4 MPa. The outlet temperature of the molten steel is controlled at 1600°C. The molten steel is sent to the continuous casting platform and allowed to stand for 20 min before pouring. S2. Continuous casting: It is carried out in a straight arc slab continuous casting machine, and the billet pulling speed is controlled at 1.5m / min, the secondary cooling water volume is 0.3L / kg, the pouring temperature is controlled at 1550℃, and the temperature fluctuation of the tundish is ±5℃; the double slag technology is used to control the centering deviation of the immersion nozzle to be less than 3mm, and the insertion depth is 90mm; the protective slag composition is designed, the cooling water flow and temperature of the crystallizer are adjusted, the taper of the narrow copper plate is controlled, and a non-sinusoidal vibration curve is used; the number and gap of the foot rollers are set; electromagnetic stirring devices are set at the continuous casting crystallizer and the solidification end, and the stirring frequencies are 5Hz and 2Hz respectively, to obtain the billet after continuous casting; Among them, the protective slag includes the following components by mass percentage: SiO 2 :34%, CaO: 29%, MgO: 1.1%, Al 2 O 3 :6%,Fe 2 O 3 :0.8%, MnO 2 :2.5%,F:9%,Na 2 O: 10.6%, Li 2 O: 1.5%, modified particles: 5.5%, wherein the mass ratio of potassium titanate to lithium carbonate in the modified particles is 1:2; The water flow rate of the narrow side of the crystallizer cooling water is 350L / min, the water flow rate of the wide side is 2500L / min, the water inlet temperature is 22℃, the inlet and outlet temperature difference is controlled at 15℃, the taper of the narrow side copper plate of the crystallizer is 10, the crystallizer adopts a non-sinusoidal vibration curve, the amplitude is 6.2mm, the vibration frequency is 167HZ, the negative slip time is 0.12s, and the narrow side foot roller of the crystallizer is set to 8 foot rollers, and the foot roller gap is 1mm; S3. Hot rolling: Cut the continuous casting billet and send it to the hot rolling heating furnace, and control the furnace time at 120 minutes; control the billet extraction temperature at 1210℃; carry out high-pressure water dephosphorization after the billet is extracted, and control the start rolling temperature of rough rolling and finishing rolling; implement multiple rolling to achieve the target thickness; use small-diameter work rolls to finish rolling and coiling to obtain hot-rolled coils, and each finishing rolling stand adopts a mineral oil lubricating oil system; set the roll shifting amount of each stand; control the strip threading speed and strip cooling to obtain the strip after coiling; The billet was cut to a thickness of 220 mm and a width of 1200 mm. The rough rolling temperature for high-pressure water dephosphorization of the billet was 1200 ° C, with a total of 9 rolling passes, and the target rolling thickness was 14 mm. The billet finishing rolling temperature was 1040 ° C, with eight stands continuously rolled, and the final rolling temperature was 880 ° C, with the target thickness of 2.0 mm. The working rolls with a small diameter of the finishing rolls were F7 rolls with a diameter of 420 mm. Among them, each frame of steel billet finishing rolling uses mineral oil lubricant, and the friction coefficient is required to be 0.1; Among them, each frame of finishing rolling uses mineral lubricant, and the friction coefficient is required to be 0.1, among which, the lubricating oil flow rate of F1 finishing rolling frame is controlled at 0.16L / min, the lubricating oil flow rate of F2 finishing rolling frame is controlled at 0.18L / min, the lubricating oil flow rate of F3 finishing rolling frame is controlled at 0.20L / min, the lubricating oil flow rate of F4 finishing rolling frame is controlled at 0.21L / min, and the lubricating oil flow rate of F5-F8 finishing rolling frames is controlled at 0.16L / min; The roll shifting amount of each rolling stand is set as follows: the lateral movement of the F1 finishing stand is 41.040mm, the lateral movement of the F2 finishing stand is 19.786mm, the lateral movement of the F3 finishing stand is 21.880mm, the lateral movement of the F4 finishing stand is 26.006mm, the lateral movement of the F5 finishing stand is -0.002mm, the lateral movement of the F6 finishing stand is 55.181mm, the lateral movement of the F7 finishing stand is 28.866mm, and the lateral movement of the F8 finishing stand is 32.005mm; Among them, the strip threading speed of F8 finishing mill is set at 8m / s. The pressure belt fan is started immediately after the strip exits F8 finishing mill. The fan is behind F8 finishing mill, with air volume of 44m³ / S and air pressure of 840Pa. Among them, the roller spacing at the finishing exit is set to 270mm, and the finishing exit is a layer cooling zone. When the strip thickness is 1.6mm, the head 44m is not sprayed with water for cooling, and when the strip thickness is 2.2, the head 27m is not sprayed with water for cooling; S4. Subsequent processing: The coiled strip is water-cooled to room temperature and sent to the annealing and pickling production line; after annealing and pickling, the white coil has no surface defects, no cracks on the edges, and no broken strips; the surface roughness of the strip is controlled to 0.2um, and finally an ultra-thin, grinding-free super duplex stainless steel coil is obtained.

[0028] Example 4 S1. Steelmaking: The alloy is melted using an electric arc furnace (EAF) and argon oxygen decarburization (AOD). Trace elements are added using the LF process outside the furnace. Then, 2.1 m / t of silicon-calcium wire is slowly and evenly fed into the molten steel through a wire feeder. Refining is continued for 8 minutes. Magnesium particles are evenly sprayed into the molten steel through a blowing device using argon as a carrier. The blowing pressure is controlled at 0.4 MPa. The outlet temperature of the molten steel is controlled at 1580°C. The molten steel is sent to the continuous casting platform and left to stand for 19 minutes before pouring. S2. Continuous casting: It is carried out in a straight arc slab continuous casting machine, and the billet pulling speed is controlled at 1.5m / min, the secondary cooling water ratio is 0.4L / kg, the pouring temperature is controlled at 1555℃, and the temperature fluctuation of the tundish is ±5℃; the double slag technology is used to control the centering deviation of the immersion nozzle to be less than 3mm, and the insertion depth is 110mm; the protective slag composition is designed, the flow rate and temperature of the crystallizer cooling water are adjusted, the taper of the narrow side copper plate is controlled, and a non-sinusoidal vibration curve is used; the number and gap of the foot rollers are set; electromagnetic stirring devices are set at the continuous casting crystallizer and the solidification end, and the stirring frequencies are 8Hz and 3Hz respectively, to obtain the billet after continuous casting; Among them, the protective slag includes the following components by mass percentage: SiO 2 :31%, CaO: 31%, MgO: 1.8%, Al 2 O 3 :5%,Fe 2 O 3 :1.1%, MnO 2 :2.2%, F:10%, Na 2 O: 10%, Li 2 O: 2.1%, modified particles: 5.8%, wherein the mass ratio of potassium titanate to lithium carbonate in the modified particles is 1:2.5; The water flow rate of the narrow side of the crystallizer cooling water is 350L / min, the water flow rate of the wide side is 2500L / min, the inlet water temperature is 24℃, the inlet and outlet water temperature difference is controlled at 16℃, the taper of the narrow side copper plate of the crystallizer is 11, the crystallizer adopts a non-sinusoidal vibration curve, the amplitude is 6.5mm, the vibration frequency is 169HZ, the negative slip time is 0.12s, and the narrow side foot roller of the crystallizer is set to 8 foot rollers, and the foot roller gap is 2mm; S3. Hot rolling: Cut the continuous casting billet and send it to the hot rolling heating furnace, and control the furnace time at 140 minutes; control the billet extraction temperature at 1220℃; carry out high-pressure water dephosphorization after the billet is extracted, and control the start rolling temperature of rough rolling and finishing rolling; implement multiple rolling to achieve the target thickness; use small-diameter work rolls to finish rolling and coiling to obtain hot-rolled coils, and each rack of finishing rolling adopts a mineral oil lubricating oil system; set the roll shifting amount of each rack; control the strip threading speed and strip cooling to obtain the strip after coiling; The billet was cut to a thickness of 220 mm and a width of 1500 mm. The rough rolling temperature for high-pressure water dephosphorization of the billet was 1200°C, with a total of 9 rolling passes, and the target rolling thickness was 18 mm. The billet finishing rolling temperature was 1070°C, with eight stands continuously rolled, and the final rolling temperature was 930°C, with the target thickness of 2.5 mm. The finishing rolling small-diameter working rolls used were F8 rolls with a diameter of 440 mm. Among them, each frame of steel billet finishing rolling uses mineral oil lubricant, and the friction coefficient is required to be 0.2; Among them, each frame of finishing rolling uses mineral lubricant, and the friction coefficient is required to be 0.2, among which, the lubricating oil flow rate of F1 finishing rolling frame is controlled at 0.17L / min, the lubricating oil flow rate of F2 finishing rolling frame is controlled at 0.19L / min, the lubricating oil flow rate of F3 finishing rolling frame is controlled at 0.21L / min, the lubricating oil flow rate of F4 finishing rolling frame is controlled at 0.22L / min, and the lubricating oil flow rate of F5-F8 finishing rolling frames is controlled at 0.17L / min; The roll shifting amount of each rolling stand is set as follows: the lateral movement of the F1 finishing stand is 41.040mm, the lateral movement of the F2 finishing stand is 19.786mm, the lateral movement of the F3 finishing stand is 21.880mm, the lateral movement of the F4 finishing stand is 26.006mm, the lateral movement of the F5 finishing stand is -0.002mm, the lateral movement of the F6 finishing stand is 55.181mm, the lateral movement of the F7 finishing stand is 28.866mm, and the lateral movement of the F8 finishing stand is 32.005mm; Among them, the strip threading speed of F8 finishing mill is set at 10m / s. The belt fan is started immediately after the strip exits F8 finishing mill. The fan is behind F8 finishing mill, with an air volume of 48m³ / S and an air pressure of 880Pa. The roller spacing at the finishing exit is set to 280mm, and the finishing exit is a layer cooling zone. When the strip thickness is 1.7mm, the head 48m is not cooled by water spraying. When the strip thickness is 2.5mm, the head 28m is not cooled by water spraying. S4. Subsequent processing: The coiled strip is water-cooled to room temperature and sent to the annealing and pickling production line; after annealing and pickling, the white coil has no surface defects, no cracks on the edges, and no broken strips; the surface roughness of the strip is controlled to 0.3um, and finally an ultra-thin, grinding-free super duplex stainless steel coil is obtained.

[0029] Comparative Example 1 Comparative Example 1 is different from Example 1 in that calcium silicon wire is not added in this comparative example.

[0030] Comparative Example 2 Comparative Example 2 is different from Example 1 in that the electromagnetic stirring device provided at the continuous casting crystallizer and the end of solidification is omitted in this comparative example.

[0031] Comparative Example 3 Comparative Example 3 is different from Example 1 in that no modified particles are added in this comparative example.

[0032] The alloys used in Comparative Examples 1-3 are the same as those in Example 1. The chemical compositions of the alloys in Examples 1-4 are shown in Table 1 below: Table 1 Chemical composition of alloys in Examples 1-4 (wt%) Performance Test: According to the national standard GB / T 228.1-2010, the tensile strength, yield strength, elongation and Vickers hardness of the ultra-thin non-grinding super duplex stainless steel coils obtained in Examples 1-4 and Comparative Examples 1-3 were tested, and the results are shown in Table 2 below: Table 2 It can be seen from the data that the mechanical properties of comparative examples 1-3 cannot reach the technical effects of embodiments 1-4. The modified particles have the functions of deoxidation, desulfurization and grain refinement in the molten steel. The inclusions such as magnesium oxide (MgO) and magnesium sulfide (MgS) generated by the reaction of magnesium with oxygen and sulfur can serve as heterogeneous nucleation cores, promote the refinement of austenite grains, and improve the strength and toughness of steel. In addition, magnesium can also reduce the surface tension of the molten steel, improve the surface quality of the ingot, reduce the generation of defects such as surface cracks and depressions, and help to achieve direct hot rolling without grinding. The electromagnetic stirring in the crystallizer can make the composition and temperature of the molten steel more uniform, refine the solidification structure of the ingot, reduce defects such as segregation and shrinkage, thereby further reducing the possibility of problems such as cracks and scars on the surface of the steel billet, improving the quality of the ingot, and ensuring the realization of direct hot rolling without grinding. The electromagnetic stirring at the end of solidification helps to improve the central segregation of the ingot and improve the overall performance of the material. Modified particles can increase the crystallization temperature and crystallization ability of the protective slag, so that the protective slag forms a more stable solid slag film between the crystallizer wall and the surface of the ingot. This solid slag film has good lubrication and heat insulation properties, which can effectively reduce the friction between the ingot and the crystallizer wall, reduce the friction heat on the surface of the ingot, and prevent defects such as thermal cracks and scratches on the surface of the ingot. At the same time, the stable slag film can also transfer heat evenly, which is beneficial to the solidification process of the ingot and improves the surface quality and internal quality of the ingot. The modified particles also play a role in reducing the melting point and viscosity. During the continuous casting process, the protective slag with a lower melting point and viscosity can better flow into the gap between the crystallizer and the ingot, forming a continuous and uniform liquid slag film, providing a good lubrication effect, reducing the tensile stress on the surface of the ingot, and preventing cracks. At the same time, the modified particles can also promote the melting and uniform distribution of other components in the protective slag, optimize the overall performance of the protective slag, further improve the surface quality of the ingot, reduce the incidence of surface defects, and provide high-quality billets for subsequent hot rolling processes.

[0033] In the present invention, step S2 is carried out in a straight arc slab continuous casting machine, the billet pulling speed is controlled at 1.4-1.5m / min, the secondary cooling water ratio is 0.3-0.4L / kg, the cooling under this condition can ensure the best plasticity of the straightening section, avoid stress cracks, avoid billet grinding, the start casting temperature is controlled at 1540-1560℃, and the temperature fluctuation of the tundish is ±5℃; the tundish adopts double slag technology, the top slag is insulated by rice husk, and the bottom slag is covered with a low melting point covering agent; the effect is that the molten steel is well insulated and the inclusion absorption is good; the double slag technology is used, and good molten steel insulation and inclusion absorption are maintained; the centering deviation of the submerged nozzle is controlled to be less than 3mm, and the insertion depth is 80-120mm; the billet grinding caused by molten steel slag can be prevented and avoided; the design of the protective slag solves the defects of billet longitudinal cracking, depression and scarring, and avoids billet grinding.

[0034] Control the stability of the slag layer in the crystallizer; adjust the cooling water flow and temperature of the crystallizer, control the taper of the narrow copper plate, and use a non-sinusoidal vibration curve; set the number and gap of the foot rollers to avoid cracks; the water flow rate of the narrow side of the crystallizer cooling water is 350L / min, and the water flow rate of the wide side is 2500L / min. This range of water can prevent cooling thermal stress cracks; the inlet water temperature is 20-25℃, and the inlet and outlet water temperature difference is controlled at 15-16℃. This range can take away stable heat, achieve uniform cooling, uniform solidification of the shell, and avoid cracks. No billet grinding is required; the taper of the narrow side copper plate of the crystallizer is 10-11, and this range of values ​​is most in line with the solidification shrinkage law of the billet, which can achieve better gap control, ensure stable heat conduction, effectively prevent cracks, and avoid billet grinding; the crystallizer adopts a non-sinusoidal vibration curve with an amplitude of 6.0-6.5mm, a vibration frequency of 165-170HZ, a negative slip time of 0.11-0.13s, and 8 foot rollers are set on the narrow side of the crystallizer, with a foot roller gap of 1-2mm. This range can effectively prevent transverse cracks caused by deep vibration marks and avoid billet grinding.

[0035] The thickness of the steel billet cutting is 220mm and the width is 1000-1600mm; the rough rolling temperature of the steel billet high-pressure water dephosphorization is 1190-1210℃, a total of 9 rolling passes are implemented, and the rolling target thickness is 10-20mm.

[0036] Step S3: hot-send the steel billet to the hot rolling heating furnace after cutting, and control the time in the furnace to be 100-150min; because the steel billet is hot-sent, the heating time of the heating furnace is saved, and the cost of the heating furnace is reduced; the steel billet extraction temperature is controlled at 1210-1220℃; after the steel billet is extracted, high-pressure water dephosphorization is carried out after the furnace, and the start rolling temperature of rough rolling and finishing rolling is controlled; multiple rolling passes are implemented to achieve the target thickness; the hot-rolled coil is obtained after finishing coiling with a working roll with a small roller diameter, and each frame of finishing rolling adopts a mineral oil lubricating oil system; the roll shifting amount of each frame is set to improve the same plate difference and plate shape; the strip threading speed and strip cooling are controlled to avoid material flying; The billet finishing rolling start temperature is 1000-1080℃, eight stands are used for continuous rolling, the final rolling temperature is 850-950℃, and the target thickness is 1.5-2.8mm. Due to the sensitivity of σ precipitation in the range near 900℃, hot rolling usually needs to be completed at above 950℃, but since the heat dissipation and cooling of ultra-thin materials (below 2.0mm) are very fast, it is difficult to control the ultra-thin materials to complete the rolling above 950℃, and they are usually below 950℃, resulting in a large number of edge cracks and broken strips. Therefore, the sensitivity of σ precipitation is reduced by the design of alloy elements, and safe (no edge cracks and no broken strips) rolling in the range of 800-950℃ is achieved; The working rolls of the finishing rolling with small roll diameters are F6-F8 rolls with a diameter of 400-450mm. The small roll diameter design is specially designed for rolling of extremely thin materials, which can better control the strip plate difference and balance the rolling load; Each rack of billet finishing rolling uses mineral oil lubricant, and the friction coefficient is required to be 0.1-0.2; Among them, each rack of finishing rolling uses mineral oil lubricant, and the friction coefficient is required to be 0.1-0.2, among which, the lubricating oil flow rate of F1 finishing rolling rack is controlled at 0.16-0.17L / min, the lubricating oil flow rate of F2 finishing rolling rack is controlled at 0.18-0.19L / min, the lubricating oil flow rate of F3 finishing rolling rack is controlled at 0.20-0.21L / min, the lubricating oil flow rate of F4 finishing rolling rack is controlled at 0.21-0.22L / min, and the lubricating oil flow rate of F5-F8 finishing rolling racks is controlled at 0.16-0.17L / min; Such distribution can balance the load of each rack, better realize thin material rolling, and avoid surface and plate shape problems caused by roller damage and wear due to excessive load; The roller shifting amount of each finishing stand is set as follows: the lateral movement of the F1 finishing stand is 41.040mm, the lateral movement of the F2 finishing stand is 19.786mm, the lateral movement of the F3 finishing stand is 21.880mm, the lateral movement of the F4 finishing stand is 26.006mm, the lateral movement of the F5 finishing stand is -0.002mm, the lateral movement of the F6 finishing stand is 55.181mm, the lateral movement of the F7 finishing stand is 28.866mm, and the lateral movement of the F8 finishing stand is 32.005mm. This setting can improve the problem of thin material same plate difference and local bulge of plate shape; The strip threading speed of F8 finishing mill is set at 6-12m / s. The strip pressure fan is started immediately after the strip exits F8 finishing mill. The fan is behind F8 finishing mill, with air volume of 40-50m³ / S and air pressure of 800-900Pa. The purpose is to press the strip head onto the roller table as soon as it exits the mill to prevent thin material from flying and causing scrap steel. The roller spacing at the finishing exit is set to 260-300mm, and the finishing exit is a layer cooling zone. When the strip thickness is 1.5-1.8mm, the head 40-50m is not sprayed with water for cooling, and when the strip thickness is 1.8-2.8, the head 25-30m is not sprayed with water for cooling. This ensures smooth coiling and improves coil shape.

[0037] The present invention solves the problem of steel billet defects from the source by optimizing the continuous casting process and controlling the ratio of alloy components and trace elements, thereby realizing direct hot rolling without grinding. Through the design of alloy elements, the precipitation of σ phase is effectively suppressed and its precipitation sensitivity is reduced, so that safe rolling can be carried out within a wider temperature range (800-950°C), thereby realizing ultra-thin rolling.

[0038] The present invention significantly improves production efficiency and cost, eliminates the step of steel billet grinding, reduces intermediate links, shortens the production cycle, and reduces labor costs and equipment wear. In addition, the method broadens the application range of the product and can produce ultra-thin stainless steel coils below 3 mm, meeting the needs of more market segments and enhancing the market competitiveness of the product.

[0039] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an ultra-thin grinding-free super duplex stainless steel coil, characterized in that: The method comprises the following preparation steps: S1. Steelmaking: The alloy is smelted using an electric arc furnace (EAF) and argon oxygen decarburization (AOD). Trace elements are added using the LF process outside the furnace. Then, 1.8-2.2 m / t of silicon-calcium wire is slowly and evenly fed into the molten steel through a wire feeder. Refining is continued for 5-10 minutes. Magnesium particles are evenly sprayed into the molten steel through a blowing device using argon as a carrier. The blowing pressure is controlled at 0.3-0.4 MPa. The outlet temperature of the molten steel is controlled at 1500-1600°C. The molten steel is sent to the continuous casting platform and allowed to stand for 18-20 minutes before pouring. S2. Continuous casting: It is carried out in a straight arc slab continuous casting machine, and the billet pulling speed is controlled at 1.4-1.5m / min, the secondary cooling water ratio is 0.3-0.4L / kg, the pouring temperature is controlled at 1540-1560℃, and the temperature fluctuation of the tundish is ±5℃; the double slag technology is used to control the centering deviation of the immersion nozzle to be less than 3mm, and the insertion depth is 80-120mm; the protective slag composition is designed, the cooling water flow and temperature of the crystallizer are adjusted, the taper of the narrow copper plate is controlled, and a non-sinusoidal vibration curve is used; the number and gap of the foot rollers are set; electromagnetic stirring devices are set in the continuous casting crystallizer and the solidification end, and the stirring frequencies are 2-10Hz and 0.5-5Hz respectively, to obtain the billet after continuous casting; S3. Hot rolling: Cut the continuous casting billet and send it to the hot rolling heating furnace, and control the furnace time at 100-150min; control the billet extraction temperature at 1210-1220℃; carry out high-pressure water dephosphorization after the billet is extracted, and control the start rolling temperature of rough rolling and finishing rolling; implement multiple rolling to achieve the target thickness; use small-diameter work rolls to finish rolling and coiling to obtain hot-rolled coils, and each rack of finishing rolling adopts a mineral oil lubricating oil system; set the roll shifting amount of each rack; control the strip threading speed and strip cooling to obtain the strip after coiling; S4. Subsequent processing: The coiled strip is water-cooled to room temperature and sent to the annealing and pickling production line; after annealing and pickling, the white coil has no surface defects, no cracks on the edges, and no broken strips; the surface roughness of the strip is controlled to 0.1-0.4um, and finally an ultra-thin grinding-free super duplex stainless steel coil is obtained; Among them, the raw material composition of ultra-thin grinding-free super duplex stainless steel coil includes alloy components and trace elements. In terms of mass percentage, the alloy components include: C≤0.03%; Si≤0.8%; Mn≤1.2%; P≤0.035%; S≤0.02%; Ni: 14.5%-20.5%; Cr: 66.7%-72.7%; Mo: 9-12.8%; Cu≤0.5%, N: 0.24%-0.32%; Trace elements include: B: 0.0005%-0.0010%; Zr: 0.002%-0.005%; Nb: 0.003%-0.01%.

2. The method for preparing an ultra-thin grinding-free super duplex stainless steel coil according to claim 1, characterized in that: In step S2, the protective slag includes, by mass percentage, the following components: SiO2: 29-36%, CaO: 27-34%, MgO: 0.1-2.2%, Al2O3: 4-7%, Fe2O3 <1.4%, MnO2: 0.8-3.0%, F: 7-11%, Na2O: 9-13%, Li2O: 0.5-2.5%, and modified particles: 2.5-10%.

3. The method for preparing an ultra-thin grinding-free super duplex stainless steel coil according to claim 2, characterized in that: The mass ratio of potassium titanate to lithium carbonate in the modified particles is 1:1.2-3.

4. The method for preparing an ultra-thin grinding-free super duplex stainless steel coil according to claim 1, characterized in that: In step S2, the parameters of the protective slag during the continuous casting process are as follows: basicity is 0.8-1.5; viscosity is 0.5-1.0; softening point is 980-1070°C; melting point is 1000-1100°C; and flow point is 1070-1190°C.

5. The method for preparing an ultra-thin grinding-free super duplex stainless steel coil according to claim 1, characterized in that: In step S2, the water flow rate of the narrow side cooling water of the crystallizer is 350L / min, the water flow rate of the wide side is 2500L / min, the water inlet temperature is 20-25℃, the inlet and outlet water temperature difference is controlled at 15-16℃, the taper of the narrow side copper plate of the crystallizer is 10-11, the crystallizer adopts a non-sinusoidal vibration curve, the amplitude is 6.0-6.5mm, the vibration frequency is 165-170HZ, the negative slip time is 0.11-0.13s, and the narrow side foot rollers of the crystallizer are set to 8 foot rollers with a foot roller gap of 1-2mm.

6. The method for preparing an ultra-thin grinding-free super duplex stainless steel coil according to claim 1, characterized in that: In step S3, the thickness of the steel billet cut is 220 mm and the width is 1000-1600 mm; the rough rolling temperature of the steel billet high-pressure water dephosphorization is 1190-1210°C, and a total of 9 rolling passes are implemented, with a rolling target thickness of 10-20 mm.

7. The method for preparing an ultra-thin grinding-free super duplex stainless steel coil according to claim 1, characterized in that: In step S3, the billet is finished rolled at a starting temperature of 1000-1080°C, eight stands are used for continuous rolling, the final rolling temperature is 850-950°C, and the billet is rolled to a target thickness of 1.5-2.8 mm; the working rolls of the finishing rolling with a small roll diameter are F6-F8 rolls with a diameter of 400-450 mm.

8. The method for preparing an ultra-thin grinding-free super duplex stainless steel coil according to claim 1, characterized in that: Each rack of steel billet finishing rolling uses mineral oil lubricant, and the friction coefficient is required to be 0.1-0.2; among them, each rack of finishing rolling uses mineral oil lubricant, and the friction coefficient is required to be 0.1-0.2, among which, the lubricating oil flow rate of F1 finishing rolling rack is controlled at 0.16-0.17L / min, the lubricating oil flow rate of F2 finishing rolling rack is controlled at 0.18-0.19L / min, the lubricating oil flow rate of F3 finishing rolling rack is controlled at 0.20-0.21L / min, the lubricating oil flow rate of F4 finishing rolling rack is controlled at 0.21-0.22L / min, and the lubricating oil flow rate of F5-F8 finishing rolling racks is controlled at 0. .16-0.17L / min; The roller shifting amount of each finishing mill stand is set as follows: the lateral movement of F1 finishing mill stand is 41.040mm, the lateral movement of F2 finishing mill stand is 19.786mm, the lateral movement of F3 finishing mill stand is 21.880mm, the lateral movement of F4 finishing mill stand is 26.006mm, the lateral movement of F5 finishing mill stand is -0.002mm, the lateral movement of F6 finishing mill stand is 55.181mm, the lateral movement of F7 finishing mill stand is 28.866mm, and the lateral movement of F8 finishing mill stand is 32.005mm.

9. The method for preparing an ultra-thin grinding-free super duplex stainless steel coil according to claim 1, characterized in that: The strip threading speed of F8 finishing mill is set at 6-12m / s. The pressure belt fan is started immediately after the strip leaves F8 finishing mill. The fan is behind F8 finishing mill, with air volume of 40-50m³ / S and air pressure of 800-900Pa.

10. The method for preparing an ultra-thin grinding-free super duplex stainless steel coil according to claim 1, characterized in that: In step S3, the roller spacing at the finishing rolling exit is set to 260-300mm, the finishing rolling exit is a layer cooling zone, when the strip thickness is 1.5-1.8mm, its head 40-50m is not sprayed with water for cooling, and when the strip thickness is 1.8-2.8, its head 25-30m is not sprayed with water for cooling.

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