Continuous casting billet for seawater corrosion resistant steel and production method of continuous casting billet

Abstract

The invention relates to a production method of a continuous casting billet for seawater corrosion resistant steel, and belongs to the technical field of steel. Continuous casting crystallizer casting powder and casting powder layer thickness control are adopted, and the good lubricating effect of the casting powder is guaranteed; according to the section size of a continuous casting machine, surface and internal cracks are prevented from being formed by controlling the continuous casting pulling speed, the superheat degree, the crystallizer water amount, the secondary cooling water amount, the taper, the roll gap shrinkage amount and the like; the center density of the continuous casting billet is improved by controlling the fan-shaped section roll gap shrinkage amount and the soft reduction, the effects of eliminating center shrinkage cavities and looseness and relieving center segregation are achieved, the surface crack occurrence rate of the continuous casting billet for the seawater corrosion resistant steel is smaller than or equal to 0.1%, triangular area cracks are smaller than or equal to 0.5 level, middle cracks are smaller than or equal to 0.5 level, and the center segregation rating is superior to C 1.5 level.

Description

Technical Field

[0001] The invention relates to a continuous casting billet for seawater corrosion resistant steel and a production method thereof, belonging to the technical field of steel materials. Background Art

[0002] Since marine steel structures are exposed to harsh environments such as salt spray, moisture and seawater for a long time, they will be severely electrochemically corroded by the erosion of seawater and marine organisms. The paint film of steel materials is prone to severe saponification and aging, which will corrode the steel structures of marine facilities, not only reducing the mechanical properties of structural materials, but also shortening the service life of marine facilities. At the same time, marine facilities are far away from the mainland coast and cannot be regularly repaired and maintained like ships. Therefore, it is necessary to develop steel plates with better seawater corrosion resistance.

[0003] At present, steel enterprises mainly improve the seawater corrosion resistance of steel plates by increasing the Cr, Mo and Al content in steel. Al can react with O2 in the air to form an Al2O3 protective film. Cr and Mo ions can automatically replenish the gaps formed by the pitting corrosion of steel by seawater Cl ions, forming a dense protective layer to prevent pitting corrosion from developing in depth, further improving the corrosion resistance of steel. The increase in Al content in steel puts higher requirements on the control of the continuous casting process. Therefore, it is necessary to control the continuous casting process parameters to ensure the surface and internal quality of the continuous casting billet.

[0004] The patent application with the patent publication number CN117778682A discloses a production method of 80-120mm thick seawater corrosion resistant steel 10CrMoAl, which uses a water-cooled die-cast steel ingot with a thickness of ≥600mm to protect the slag compression ratio, combined with non-recrystallization zone rolling, controlled cooling and high-temperature tempering to obtain a seawater corrosion resistant steel plate with excellent performance. This method uses die casting production, with low efficiency and yield rate, and high cost.

[0005] The patent application with the patent publication number CN117210766A discloses a marine engineering steel resistant to seawater corrosion and its preparation method. By adopting a low-carbon, low-silicon, medium-chromium cheap chemical composition design, and using Si and Zr-RE composite deoxidation, a fine, dispersed and uniform composite oxysulfide is formed, which greatly reduces the density of corrosion active inclusions and significantly improves the seawater corrosion resistance of steel used in marine environments. This method uses rare earth elements to deoxidize molten steel, which not only has high steelmaking costs, but also is prone to immersion nozzle blockage during continuous casting, resulting in unplanned stoppage of continuous casting.

[0006] The patent application with the patent publication number CN116590619A discloses a method for producing 10CrMoAl seawater corrosion resistant steel. Through composition design and combined with smelting, continuous casting, rolling, heat treatment and other processes, the seawater corrosion resistant steel with stable performance is produced. The method does not introduce parameters such as the drawing speed, secondary cooling water distribution, and fan-shaped segment roll gap control in the continuous casting process. There is a suspicion that it cannot be implemented.

[0007] Based on the above analysis, there is currently no mature process to produce stable seawater corrosion-resistant steel. Summary of the invention

[0008] In order to solve the above problems, the present invention discloses a continuous casting billet for seawater corrosion resistant steel and a production method thereof, and the specific technical scheme thereof is as follows: A method for producing a continuous casting billet for seawater corrosion resistant steel comprises subjecting molten iron to a molten iron pretreatment process, a primary refining furnace process, a refining process and a continuous casting process to obtain a continuous casting billet, specifically comprising the following steps: Step (1) subjecting molten iron to a molten iron pretreatment process, a primary refining furnace process, and a refining process to obtain molten steel with qualified composition and temperature, and hoisting the molten steel to a continuous casting platform for continuous casting protection pouring; Step (2) Continuous casting process: 2.1) Molten steel flows from the tundish through the submerged nozzle into the crystallizer of the continuous casting machine; 2.2) Add protective slag into the crystallizer. The chemical composition of the protective slag is SiO2: 18%-34%, CaO: 31%-42%, MgO: 0-3.5%, Al2O3: 0.5%-3.5%, Na2O: 8%-15%, F: 6%-14%, C: 5%-9%, and the rest are unavoidable impurities; 2.3) The continuous casting machine passes through the continuous casting secondary cooling zone, which includes the foot roll section, the zero section and 14 fan-shaped segments. The foot roll section corresponds to the secondary cooling zone 1, the zero section corresponds to the secondary cooling zones 2, 3 and 4, the 1# and 2# fan-shaped segments correspond to the 5th zone, the 3# and 4# fan-shaped segments correspond to the 6th zone, the 5#-7# fan-shaped segments correspond to the 7th zone, the 8#-10# fan-shaped segments correspond to the 8th zone, and the 11#, 12#, 13# and 14# fan-shaped segments correspond to the 9th zone; 2.4) The ingot leaves the secondary cooling zone of continuous casting and is flame cut to obtain the continuous casting ingot.

[0009] Furthermore, in the continuous casting process, the mass percentage of Al2O3 in the continuous casting mold protection slag is controlled according to the Al content of the steel grade, and the corresponding relationship between the Al content of the steel grade and the mass percentage of Al2O3 in the continuous casting mold protection slag W (Al2O3) is: When the steel grade is such that 0.50% ≤ Al < 0.60%, the mass percentage content of Al2O3 in the mold powder is 0.5% ≤ W(Al2O3) < 1.5%; When the steel grade is such that 0.60% ≤ Al < 0.70%, the mass percentage content of Al2O3 in the mold powder is 1.5% ≤ W(Al2O3) < 2.5%; When the steel grade is such that 0.70% ≤ Al ≤ 0.80%, the mass percentage content of Al2O3 in the mold powder is 2.5% ≤ W(Al2O3) ≤ 3.5%.

[0010] Furthermore, the chemical composition of the mold powder in mass percentage is: SiO2: 22% - 30%, CaO: 34% - 40%, MgO: 1.0% - 2.5%, Al2O3: 0.5% - 3.5%, Na2O: 10% - 13%, F: 8% - 12%, C: 5% - 9%, and the rest are inevitable impurities; The binary basicity CaO / SiO2 of the mold powder is 1.33 - 1.55, the melting point is 1190 - 1250 °C, and the viscosity at 1300 °C is 0.04 - 0.10 Pa·s; The thickness h of the slag layer of the mold powder in the mold is controlled within 90 - 120 mm, and the immersion depth r of the submerged nozzle is 170 - 200 mm.

[0011] Furthermore, the corresponding relationship between the cross - section width l of the continuous caster, the thickness h of the slag layer of the mold powder, and the immersion depth r of the submerged nozzle of the continuous caster is as follows: When the cross - section width of the continuous caster is 1800 mm ≤ l < 2100 mm, the thickness of the slag layer of the mold powder is 110 mm < h ≤ 120 mm, and the immersion depth of the submerged nozzle is 170 mm ≤ r < 180 mm; When the cross - section width of the continuous caster is 2100 mm ≤ l < 2400 mm, the thickness of the slag layer of the mold powder is 100 mm < h ≤ 110 mm, and the immersion depth of the submerged nozzle is 180 mm ≤ r < 190 mm; When the cross - section width of the continuous caster is 2400 mm ≤ l ≤ 2700 mm, the thickness of the slag layer of the mold powder is 90 mm ≤ h ≤ 100 mm, and the immersion depth of the submerged nozzle is 190 mm ≤ r ≤ 200 mm.

[0012] Furthermore, during the continuous casting and protective casting process, the argon flow rate of the long nozzle is 150 - 200 L / min, the argon flow rate of the upper nozzle is 3 - 6 L / min, and the argon flow rate of the slide mechanism is 6 - 10 L / min.

[0013] Furthermore, the casting speed of the continuous caster is 1.1 - 1.3 m / min, the superheat of molten steel in the tundish is 20 - 30 °C, the water flow rate on the wide face of the mold is 3600 - 4000 L / min, the taper of the narrow side of the mold is 1.05% - 1.15%, the water flow rate on the narrow side is 380 - 460 L / min, the liquid level fluctuation of the mold is controlled within ±2 mm, and the specific water consumption in the secondary cooling zone is 0.8 - 1.0 L / kg.

[0014] Furthermore, the proportion of the secondary cooling water volume in Zone 1 - Zone 9 is 8% - 12%, 24% - 28%, 20% - 24%, 8% - 12%, 13% - 17%, 6% - 10%, 1% - 5%, 1% - 5%, 1% - 5% respectively; the water distribution in Zone 1 is divided into the narrow side and the wide face of the continuous casting billet, and the proportion of the water volume is 30% - 40%, 60% - 70% respectively.

[0015] Furthermore, the shrinkage of the roll gap in the soft reduction section and the zero section is 0 - 0.1 mm; the shrinkage of the roll gap in the segment No. 1# - 4# is 0.1 - 0.2 mm; the shrinkage of the roll gap in the segment No. 5# - 8#, 12# - 14# is 0.2 - 0.3 mm; the segment No. 9# - 11# performs soft reduction, the reduction amount is 5 - 7 mm, and the distribution ratio of the reduction amount is 20%, 40%, 40%.

[0016] Furthermore, the chemical composition of the mold powder is as follows in mass percentage: SiO2: 30% - 34%, CaO: 40% - 42%, MgO: 0 - 1.0%, Al2O3: 1.5% - 2.5%, Na2O: 8% - 10%, F: 6% - 8%, C: 5% - 7%, and the rest are inevitable impurities; The binary basicity CaO / SiO2 of the mold powder is 1.24 - 1.33, the melting point is 1160 - 1190 °C, and the viscosity at 1300 °C is 0.10 - 0.15 Pa·s; The thickness h of the slag layer of the mold powder in the mold is controlled within 70 - 90 mm, and the immersion depth r of the submerged nozzle is 150 - 170 mm.

[0017] Furthermore, the corresponding relationship between the section width l of the continuous caster, the thickness h of the slag layer of the mold powder, and the immersion depth r of the submerged nozzle of the continuous casting is as follows: When the section width of the continuous caster 1800 mm ≤ l < 2100 mm, the thickness of the slag layer of the mold powder is 84 mm < h ≤ 90 mm, and the immersion depth of the submerged nozzle is 150 mm ≤ r < 157 mm; When the section width of the continuous caster 2100 mm ≤ l < 2400 mm, the thickness of the slag layer of the mold powder is 77 mm < h ≤ 84 mm, and the immersion depth of the submerged nozzle is 157 mm ≤ r < 164 mm; When the cross-sectional width of the continuous casting machine is 2400mm≤l≤2700mm, the thickness of the mold protective slag layer is 70mm≤h≤77mm, and the insertion depth of the submerged nozzle is 164mm≤r≤170mm.

[0018] Furthermore, during the continuous casting protection casting process, the argon flow rate of the long water inlet is 130-150 L / min, the argon flow rate of the upper water inlet is 2-3 L / min, and the argon flow rate of the slide mechanism is 4-6 L / min.

[0019] Furthermore, the casting speed of the continuous casting machine is 1.0-1.1m / min, the superheat of the molten steel in the tundish is 30-40°C, the water volume on the wide surface of the crystallizer is 3400-3600L / min, the taper of the narrow side of the crystallizer is 1.10%-1.20%, the water volume on the narrow side is 350-380L / min, the crystallizer liquid level fluctuation is controlled to ±1.5mm, and the water volume in the secondary cooling zone is 0.7-0.8L / kg.

[0020] Furthermore, the secondary cooling water volume in zone 1 and zone 9 account for 13%-17%, 26%-30%, 21%-25%, 9%-13%, 12%-16%, 5%-7%, 0-2%, 0-2% and 0-2% respectively; the water distribution in zone 1 is divided into the narrow side and wide side of the continuous casting billet, and the water volume accounts for 20%-30% and 70%-80% respectively.

[0021] Furthermore, the roll gap contraction amount of the foot roll segment and the zero segment is 0.05-0.15mm; the roll gap contraction amount of the fan segments No. 1#-4# is 0.15-0.25mm; the roll gap contraction amount of the fan segments No. 5#-8# and 12#-14# is 0.25-0.35mm; the fan segments No. 9#-11# perform light pressing, the pressing amount is 4-6mm, and the pressing amount distribution ratio is 30%, 60%, and 10%.

[0022] Furthermore, the chemical composition of the protective slag is SiO2: 18%-22%, CaO: 31%-34%, MgO: 2.5%-3.5%, Al2O3: 0.5%-1.5%, Na2O: 13%-15%, F: 12%-14%, C: 9%-12%, and the rest are unavoidable impurities; The protective slag has a binary basicity of CaO / SiO2 of 1.55-1.72, a melting point of 1250-1270°C, and a viscosity of 0.02-0.04 Pa·s at 1300°C; The thickness h of the protective slag layer in the crystallizer is controlled at 120-140 mm, and the insertion depth r of the submerged nozzle is 200-220 mm.

[0023] Furthermore, the corresponding relationships between the cross-sectional width \(l\) of the continuous caster, the thickness \(h\) of the mold powder layer, and the immersion depth \(r\) of the submerged entry nozzle of the continuous caster are as follows: When the cross-sectional width of the continuous caster is \(1800\mathrm{mm}\leq l\lt2100\mathrm{mm}\), the thickness of the mold powder layer is \(134\mathrm{mm}\lt h\leq140\mathrm{mm}\), and the immersion depth of the submerged entry nozzle is \(200\mathrm{mm}\leq r\lt207\mathrm{mm}\); When the cross-sectional width of the continuous caster is \(2100\mathrm{mm}\leq l\lt2400\mathrm{mm}\), the thickness of the mold powder layer is \(127\mathrm{mm}\lt h\leq134\mathrm{mm}\), and the immersion depth of the submerged entry nozzle is \(207\mathrm{mm}\leq r\lt214\mathrm{mm}\); When the cross-sectional width of the continuous caster is \(2400\mathrm{mm}\leq l\leq2700\mathrm{mm}\), the thickness of the mold powder layer is \(120\mathrm{mm}\leq h\leq127\mathrm{mm}\), and the immersion depth of the submerged entry nozzle is \(214\mathrm{mm}\leq r\leq220\mathrm{mm}\).

[0024] Furthermore, during the continuous casting protective casting process, the argon flow rate of the long nozzle is \(200 - 220\mathrm{L / min}\), the argon flow rate of the upper nozzle is \(6 - 7\mathrm{L / min}\), and the argon flow rate of the slide plate mechanism is \(10 - 12\mathrm{L / min}\).

[0025] Furthermore, the casting speed of the continuous caster is \(1.3 - 1.4\mathrm{m / min}\), the superheat of the molten steel in the tundish is \(10 - 20^{\circ}C\), the water flow rate on the wide face of the mold is \(4000 - 4200\mathrm{L / min}\), the taper of the narrow side of the mold is \(1.03\% - 1.10\%\), the water flow rate on the narrow side is \(460 - 490\mathrm{L / min}\), the liquid level fluctuation of the mold is controlled within \(\pm3\mathrm{mm}\), and the specific water consumption in the secondary cooling zone is \(1.0 - 1.1\mathrm{L / kg}\).

[0026] Furthermore, the proportion of the secondary cooling water volume in Zone 1 - Zone 9 is \(6\% - 10\%\), \(19\% - 24\%\), \(17\% - 22\%\), \(7\% - 11\%\), \(15\% - 18\%\), \(8\% - 13\%\), \(3\% - 7\%\), \(3\% - 7\%\), \(3\% - 7\%\) respectively; the water distribution in Zone 1 is divided into the narrow side and the wide face of the continuous casting billet, and the proportion of the water volume is \(40\% - 50\%\), \(50\% - 60\%\) respectively.

[0027] Furthermore, the roll gap shrinkage of the soft reduction segment and the zero segment is \(0 - 0.05\mathrm{mm}\); the roll gap shrinkage of the segment No. 1# - 4# is \(0.05 - 0.15\mathrm{mm}\); the roll gap shrinkage of the segment No. 5# - 8# and 12# - 14# is \(0.15 - 0.25\mathrm{mm}\); the segment No. 9# - 11# performs soft reduction, and the reduction amount is \(7 - 9\mathrm{mm}\), and the distribution ratio of the reduction amount is \(10\%\), \(30\%\), \(60\%\).

[0028] Furthermore, the width length of the full roller segment is 0.52m, with 2 pairs of rollers distributed; the length of the zero segment is 3m, with 10 pairs of rollers distributed; the length of the fan-shaped segments numbered 1#-14# is 2.4m, with 7 pairs of rollers distributed in each fan-shaped segment; the fan-shaped segments numbered 1#-7# are located in the arc section of the continuous casting machine, and the fan-shaped segments 8#-14# are located in the horizontal section of the continuous casting machine.

[0029] Furthermore, the continuous casting machine is a straight arc slab continuous casting machine with a cross section of 220 mm×(1800-2700) mm and an arc radius of 10 m.

[0030] The present invention also applies to protect the continuous casting billet for seawater corrosion resistant steel produced by the above-mentioned production method for the continuous casting billet for seawater corrosion resistant steel.

[0031] The chemical composition of the continuous casting billet for seawater corrosion resistant steel is, in mass percentage, C: 0.05% - 0.15%, Si: 0.25% - 0.45%, Mn: 0.40% - 0.70%, P: ≤ 0.015%, S: ≤ 0.005%, Al: 0.50% - 0.80%, Cr: 0.90% - 1.20%, Mo: 0.15% - 0.25%, and the rest is Fe and unavoidable impurities.

[0032] The principle of the present invention is as follows: In order to solve the quality problem of continuous casting billets for seawater corrosion resistant steel, firstly, high alkalinity, high melting point and low viscosity continuous casting crystallizer protective slag is selected to control the solidification heat transfer rate of molten steel inside the crystallizer, avoid concentrated shrinkage of billet shell caused by too fast heat dissipation, and reduce thermal stress of billet; control the Al2O3 content in the protective slag according to the Al content of steel grade, inhibit the reaction between Al in molten steel and SiO2 in the protective slag; adopt low viscosity design to increase the consumption of protective slag, so that slightly denatured slag is consumed in time to prevent the smooth pouring and the surface quality of continuous casting billet from being affected; control the thickness of protective slag layer and the insertion depth of submerged nozzle according to the cross-sectional width of continuous casting machine, and form a uniform protective slag liquid slag layer at the meniscus position of molten steel under the action of molten steel flow field and temperature field in the crystallizer, so that in the continuous casting production process of seawater corrosion resistant steel, the billet shell in the crystallizer grows evenly and has good lubrication performance, which reduces the thermal stress of billet and the incidence of surface cracks in billet.

[0033] Furthermore, in combination with the cross-sectional dimensions of the continuous casting billet, by controlling the superheat of the molten steel, the drawing speed, the water volume in the secondary cooling zone and the distribution ratio of each zone, it is ensured that when the continuous casting billet is straightened at the positions of the 4, 5 and 6# sectors, the corner temperature of the continuous casting billet is higher than 920°C to prevent the formation of transverse cracks at the corners; by controlling the water volume and the narrow side taper of the crystallizer, the drawing speed, the water volume and distribution ratio of the full roll section and the shrinkage of the sector section roll gap, the bulging amount of the narrow side and wide surface of the continuous casting billet is controlled to prevent the formation of middle cracks and triangular area cracks.

[0034] Secondly, the shrinkage of the sector roll gap and the amount of light reduction can be controlled to improve the center density of the continuous casting billet, thereby eliminating the center shrinkage cavity, looseness and reducing center segregation.

[0035] The beneficial effects of the present invention are: The present invention adopts high-basicity, high-melting-point, low-viscosity continuous casting crystallizer protective slag, and combines the control of the protective slag layer thickness to ensure good lubrication effect of the protective slag and avoid the formation of large thermal stress; according to the cross-sectional size of the continuous casting machine, the continuous casting pulling speed, superheat, the amount of crystallizer and secondary cooling water, the taper and the roller gap shrinkage are controlled to prevent the formation of surface and internal cracks; by controlling the roller gap shrinkage of the fan-shaped segment and the light pressure reduction, the central density of the continuous casting billet is improved, the central shrinkage cavity and looseness are eliminated and the central segregation is reduced, and the surface crack incidence rate of the continuous casting billet for seawater corrosion resistant steel finally obtained is ≤0.1%, the triangular area crack is ≤0.5 level, the middle crack is ≤0.5 level, and the central segregation rating is better than C 1.5 level. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a low-magnification image corresponding to the narrow side and 1 / 4 width position of the continuous casting billet in the casting of Example 1a of the present invention.

[0037] Figure 2 It is a low-magnification image corresponding to the narrow side and the 1 / 4 width position of the continuous casting billet in the 2d pouring of Example 1 of the present invention.

[0038] Figure 3 It is a low-magnification image corresponding to the narrow side and the 1 / 4 width position of the continuous casting billet in the 3g pouring of Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The following examples are provided for a better understanding of the present invention, but are not limited to the embodiments described, and do not limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0040] If no specific experimental steps or conditions are specified in the examples, the experiments can be carried out according to the conventional experimental steps or conditions described in the literature in the art.

[0041] The following specific examples are further explanations of the present invention. The examples cited cannot list all the embodiments of the present invention. Only some of the embodiments are used as examples for explanation. The equipment parameters of the continuous casting machine are as follows: the continuous casting machine is a straight arc slab continuous casting machine with a cross-sectional size of 220 mm × (1800-2700) mm and an arc radius of 10 m. The continuous casting secondary cooling zone includes a full roller segment, a zero segment and 14 fan-shaped segments, wherein the full roller segment corresponds to the secondary cooling zone 1, the zero segment corresponds to the secondary cooling zones 2, 3 and 4, the 1# and 2# fan-shaped segments correspond to the 5th zone, the 3# and 4# correspond to the 6th zone, the 5#-7# fan-shaped segments correspond to the 7th zone, the 8#-10# fan-shaped segments correspond to the 8th zone, the 11#, 12#, 13# and 14# fan-shaped segments correspond to the 9th zone, the full roller segment has a wide surface length of 0.52 m, with 2 pairs of rollers distributed; the zero segment has a length of 3 m, with 10 pairs of rollers distributed; the length of the fan-shaped segments numbered 1#-14# is 2.4 m, each sector is equipped with 7 pairs of rollers; the sector segments No. 1#-7# are located in the arc section of the continuous casting machine, and the sector segments No. 8#-14# are located in the horizontal section of the continuous casting machine. Example

[0042] Example 1

[0043] The present embodiment provides a continuous casting billet for seawater corrosion resistant steel. The chemical composition of the continuous casting billet is C: 0.05%, Si: 0.25%, Mn: 0.70%, Cr: 0.90%, P: 0.012%, S: 0.0020%, Al: 0.75%, Mo: 0.15% in percentage by mass, and the balance is Fe and other inevitable impurities. Three castings are produced, and the cross-sectional dimensions of the continuous casting billet are shown in Table 1.

[0044] Table 1 Cross-sectional dimensions of continuous casting slabs in each pouring

[0045] The specific preparation method is as follows: (1) The molten iron is subjected to the molten iron pretreatment process, the primary refining furnace process, and the refining process to obtain molten steel with qualified composition and temperature. The molten steel is hoisted to the continuous casting platform for protective pouring. The argon flow rates of the long nozzle, upper nozzle, and slide mechanism are shown in Table 2; Table 2 Argon flow rate of long nozzle, upper nozzle and slide mechanism

[0046] (2) The molten steel flows from the tundish into the crystallizer through the submerged nozzle. The continuous casting parameter control (casting speed, superheat of the molten steel in the tundish, insertion depth of the submerged nozzle, taper of the narrow side of the crystallizer, water volume on the wide and narrow sides of the crystallizer, liquid level fluctuation, etc.) is shown in Table 3; Table 3 Continuous casting parameter control

[0047] (3) Adding mold slag into the crystallizer, the chemical composition of the mold slag is expressed in mass percentage, as shown in Table 4, the physical and chemical properties of the mold slag and the thickness of the mold slag layer are shown in Table 5, the continuous casting billet in the crystallizer has a certain shell thickness and enters the secondary cooling zone of the continuous casting machine; Table 4 Composition of mold slag

[0048] Table 5 Physical and chemical properties of mold slag and slag layer thickness

[0049] (4) The specific water volume of the secondary cooling zone of the continuous casting machine and the proportion of the secondary cooling water volume in zones 1-9 are shown in Table 6. The proportion of the water volume on the narrow side and wide side of the continuous casting billet in zone 1 is shown in Table 7. The roll gap of the full roll segment, zero segment, 1#-4#, 5#-8#, and 12#-14# fan-shaped segments are only contracted, and the 9#-11# fan-shaped segments are lightly pressed. The roll gap contraction amount, pressure reduction amount, and pressure reduction distribution ratio of the continuous casting machine are shown in Table 8. Table 6 Continuous casting machine secondary cooling water ratio and secondary cooling water ratio in zones 1-9

[0050] Table 7 Water content ratio of narrow side and wide side of continuous casting billet in zone 1

[0051] Table 8 Roll gap shrinkage, reduction and reduction distribution ratio of continuous casting machine

[0052] (5) The ingot is cut into 14# fan-shaped segments and flame cut to obtain a 10m long continuous casting ingot. A low-magnification sample is taken from the continuous casting ingot, and the surface and cross-section are pickled to observe the surface cracks, triangular cracks, middle cracks and center segregation of the low-magnification sample of the continuous casting ingot.

[0053] Example 2 The present embodiment provides a continuous casting billet for seawater corrosion resistant steel. The chemical composition of the continuous casting billet is, in percentage by mass, C: 0.10%, Si: 0.35%, Mn: 0.55%, Cr: 1.05%, P: 0.011%, S: 0.0015%, Al: 0.65%, Mo: 0.20%, and the remainder is Fe and other inevitable impurities. Three castings are produced, and the cross-sectional dimensions of the continuous casting billet are shown in Table 9.

[0054] Table 9 Cross-sectional dimensions of continuous casting billets at each pouring

[0055] The specific preparation method is as follows: (1) The molten iron is subjected to the molten iron pretreatment process, the primary refining furnace process, and the refining process to obtain molten steel with qualified composition and temperature. The molten steel is hoisted to the continuous casting platform for protective pouring. The argon flow rates of the long nozzle, upper nozzle, and slide mechanism are shown in Table 10; Table 10 Argon flow rate of shroud, upper shroud and slide mechanism

[0056] (2) The molten steel flows from the tundish into the crystallizer through the submerged nozzle. The continuous casting parameter control (casting speed, superheat of the molten steel in the tundish, insertion depth of the submerged nozzle, narrow side taper of the crystallizer, water volume on the wide and narrow sides of the crystallizer, liquid level fluctuation, etc.) is shown in Table 11; Table 11 Continuous casting parameter control

[0057] (3) Adding mold slag into the crystallizer, the chemical composition of the mold slag is expressed in mass percentage, as shown in Table 12, the physical and chemical properties of the mold slag and the thickness of the mold slag layer are shown in Table 13, the continuous casting billet in the crystallizer has a certain billet shell thickness and enters the secondary cooling zone of the continuous casting machine; Table 12 Composition of mold slag

[0058] Table 13 Physical and chemical properties of mold slag and slag layer thickness

[0059] (4) The specific water volume of the secondary cooling zone of the continuous casting machine and the proportion of the secondary cooling water volume in zones 1-9 are shown in Table 14. The proportion of the water volume on the narrow side and wide side of the continuous casting billet in zone 1 is shown in Table 15. The full roll segment, zero segment, 1#-4#, 5#-8#, 12#-14# fan-shaped segments only have roll gap contraction, and the 9#-11# fan-shaped segments perform light reduction. The roll gap contraction amount, reduction amount and reduction amount distribution ratio of the continuous casting machine are shown in Table 16. Table 14 Secondary cooling water ratio of continuous casting machine and secondary cooling water ratio of zones 1-9

[0060] Table 15 Water content ratio of narrow side and wide side of continuous casting slab in zone 1

[0061] Table 16 Roll gap shrinkage, reduction and reduction distribution ratio of continuous casting machine

[0062] (5) The ingot is cut into 14# fan-shaped segments and flame cut to obtain a 10m long continuous casting ingot. A low-magnification sample is taken from the continuous casting ingot, and the surface and cross-section are pickled to observe the surface cracks, triangular cracks, middle cracks and center segregation of the low-magnification sample of the continuous casting ingot.

[0063] Example 3 The present embodiment provides a continuous casting billet for seawater corrosion resistant steel. The chemical composition of the continuous casting billet is, in percentage by mass, C: 0.15%, Si: 0.45%, Mn: 0.40%, Cr: 1.20%, P: 0.010%, S: 0.0010%, Al: 0.55%, Mo: 0.25%, and the remainder is Fe and other inevitable impurities. Three castings are produced, and the cross-sectional dimensions of the continuous casting billet are shown in Table 17.

[0064] Table 17 Cross-sectional dimensions of continuous casting billets at each pouring

[0065] The specific preparation method is as follows: (1) The molten iron is subjected to the molten iron pretreatment process, the primary refining furnace process, and the refining process to obtain molten steel with qualified composition and temperature. The molten steel is hoisted to the continuous casting platform for protective pouring. The argon flow rates of the long nozzle, upper nozzle, and slide mechanism are shown in Table 18; Table 18 Argon flow rate of shroud, upper shroud and slide mechanism

[0066] (2) The molten steel flows from the tundish into the crystallizer through the submerged nozzle. The continuous casting parameter control (casting speed, superheat of the molten steel in the tundish, insertion depth of the submerged nozzle, taper of the narrow side of the crystallizer, water volume on the wide and narrow sides of the crystallizer, liquid level fluctuation, etc.) is shown in Table 19; Table 19 Continuous casting parameter control

[0067] (3) Adding mold slag into the crystallizer, the chemical composition of the mold slag is calculated by mass percentage, as shown in Table 20, the physical and chemical properties of the mold slag and the thickness of the mold slag layer are shown in Table 21, and the continuous casting billet in the crystallizer has a certain billet shell thickness and enters the secondary cooling zone of the continuous casting machine; Table 20 Components of mold slag

[0068] Table 21 Physical and chemical properties of mold slag and slag layer thickness

[0069] (4) The specific water volume of the secondary cooling zone of the continuous casting machine and the proportion of the secondary cooling water volume in zones 1-9 are shown in Table 22. The proportion of the water volume on the narrow side and wide side of the continuous casting billet in zone 1 is shown in Table 23. The full roll segment, zero segment, 1#-4#, 5#-8#, 12#-14# fan-shaped segments only have roll gap contraction, and the 9#-11# fan-shaped segments perform light reduction. The roll gap contraction amount, reduction amount and reduction amount distribution ratio of the continuous casting machine are shown in Table 24. Table 22 Continuous casting machine secondary cooling water ratio and secondary cooling water ratio in zones 1-9

[0070] Table 23 Water content ratio of narrow side and wide side of continuous casting billet in zone 1

[0071] Table 24 Roll gap shrinkage, reduction and reduction distribution ratio of continuous casting machine

[0072] (5) The ingot is cut into 14# fan-shaped segments and flame cut to obtain a 10m long continuous casting ingot. Low-magnification samples are taken from the continuous casting ingot, and the surface and cross-section are pickled to observe the surface cracks, triangular cracks, middle cracks and center segregation of the continuous casting ingot.

[0073] The surface cracks, triangular area cracks, middle cracks and center segregation of the continuous casting billet in each embodiment were statistically analyzed, as shown in Table 25.

[0074] Table 25 Surface cracks, triangular cracks, middle cracks and center segregation of continuous casting billet

[0075] The above embodiments do not limit the present invention in any way, and any technical solutions obtained by equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A method for producing a continuous casting billet for seawater corrosion resistant steel, characterized in that: It includes subjecting hot metal to a hot metal pretreatment process, a primary melting furnace process, a refining process, and a continuous casting process to obtain a continuous casting billet, specifically including the following steps: Step (1): Subject the hot metal to a hot metal pretreatment process, a primary melting furnace process, and a refining process to obtain molten steel with qualified composition and temperature.吊运 the molten steel to the continuous casting platform and conduct continuous casting protective pouring; Step (2): Continuous casting process: 2.1) The molten steel flows from the tundish into the mold of the continuous caster through the submerged entry nozzle; 2.2) Add mold powder into the mold. The chemical composition of the mold powder, by mass percentage, is SiO2: 18% - 22%, CaO: 31% - 34%, MgO: 2.5% - 3.5%, Al2O3: 0.5% - 1.5%, Na2O: 13% - 15%, F: 12% - 14%, C: 9% - 12%, and the rest are inevitable impurities; 2.3) The continuous casting billet passes through the secondary cooling zone of the continuous caster. The secondary cooling zone of the continuous caster includes a dummy bar section, a zero section, and 14 segmental sections. The dummy bar section corresponds to secondary cooling zone 1, the zero section corresponds to secondary cooling zones 2, 3, and 4, the 1st and 2nd segmental sections correspond to zone 5, the 3rd and 4th segmental sections correspond to zone 6, the 5th - 7th segmental sections correspond to zone 7, the 8th - 10th segmental sections correspond to zone 8, and the 11th, 12th, 13th, and 14th segmental sections correspond to zone 9; 2.4) The continuous casting billet exits the secondary cooling zone of the continuous caster and is cut by flame cutting to obtain continuous casting billet blocks.

2. The method for producing a continuous casting billet for seawater corrosion resistant steel according to claim 1, characterized in that: In the continuous casting process, according to the Al content of the steel grade, control the mass percentage of Al2O3 in the continuous casting mold powder. The corresponding relationship between the Al content of the steel grade and the mass percentage of Al2O3, W(Al2O3), in the continuous casting mold powder is: When the steel grade is 0.50% ≤ Al < 0.60%, the mass percentage of Al2O3 in the mold powder is 0.5% ≤ W(Al2O3) < 1.5%; When the steel grade is 0.60% ≤ Al < 0.70%, the mass percentage of Al2O3 in the mold powder is 1.5% ≤ W(Al2O3) < 2.5%; When the steel grade is 0.70% ≤ Al ≤ 0.80%, the mass percentage of Al2O3 in the mold powder is 2.5% ≤ W(Al2O3) ≤ 3.5%.

3. The method for producing a continuous casting billet for seawater corrosion resistant steel according to claim 1, characterized in that: The binary basicity CaO / SiO2 of the mold powder is 1.55 - 1.72, the melting point is 1250 - 1270 °C, and the viscosity at 1300 °C is 0.02 - 0.04 Pa·s; The thickness of the slag layer of the mold powder in the mold is controlled at 120 - 140 mm, and the insertion depth of the submerged entry nozzle is 200 - 220 mm.

4. The method for producing a continuous casting billet for seawater corrosion resistant steel according to claim 3, characterized in that: The corresponding relationship between the width l of the cross - section of the continuous caster, the thickness h of the slag layer of the mold powder, and the insertion depth r of the submerged entry nozzle for continuous casting is: When the width of the cross - section of the continuous caster is 1800 mm ≤ l < 2100 mm, the thickness of the slag layer of the mold powder is 134 mm < h ≤ 140 mm, and the insertion depth of the submerged entry nozzle is 200 mm ≤ r < 207 mm; When the width of the cross - section of the continuous caster is 2100 mm ≤ l < 2400 mm, the thickness of the slag layer of the mold powder is 127 mm < h ≤ 134 mm, and the insertion depth of the submerged entry nozzle is 207 mm ≤ r < 214 mm; When the cross-sectional width of the continuous casting machine is 2400mm≤l≤2700mm, the thickness of the mold protective slag layer is 120mm≤h≤127mm, and the insertion depth of the submerged nozzle is 214mm≤r≤220mm.

5. The method for producing a continuous casting billet for seawater corrosion resistant steel according to claim 3, characterized in that: During the continuous casting protection pouring process, the argon flow rate of the long water inlet is 200-220 L / min, the argon flow rate of the upper water inlet is 6-7 L / min, and the argon flow rate of the slide mechanism is 10-12 L / min.

6. The method for producing a continuous casting billet for seawater corrosion resistant steel according to claim 3, characterized in that: The casting speed of the continuous casting machine is 1.3-1.4m / min, the superheat of the molten steel in the tundish is 10-20°C, the water volume on the wide surface of the crystallizer is 4000-4200L / min, the taper on the narrow side of the crystallizer is 1.03%-1.10%, the water volume on the narrow side is 460-490L / min, the crystallizer liquid level fluctuation is controlled to ±3mm, and the water volume in the secondary cooling zone is 1.0-1.1L / kg.

7. The method for producing a continuous casting billet for seawater corrosion resistant steel according to claim 3, characterized in that: The secondary cooling water volume in zone 1 and zone 9 account for 6%-10%, 19%-24%, 17%-22%, 7%-11%, 15%-18%, 8%-13%, 3%-7%, 3%-7% and 3%-7% respectively; the water distribution in zone 1 is divided into the narrow side and wide side of the continuous casting billet, and the water volume accounts for 40%-50% and 50%-60% respectively.

8. The method for producing a continuous casting billet for seawater corrosion resistant steel according to claim 3, characterized in that: The roll gap contraction amount of the foot roll segment and the zero segment is 0-0.05mm; the roll gap contraction amount of the fan segments No. 1#-4# is 0.05-0.15mm; the roll gap contraction amount of the fan segments No. 5#-8# and 12#-14# is 0.15-0.25mm; the fan segments No. 9#-11# perform light pressing, the pressing amount is 7-9mm, and the pressing amount distribution ratio is 10%, 30%, and 60%.

9. The method for producing a continuous casting billet for seawater corrosion resistant steel according to claim 1, characterized in that: The wide length of the full roller segment is 0.52m, with 2 pairs of rollers distributed; the length of the zero segment is 3m, with 10 pairs of rollers distributed; the length of the fan-shaped segments numbered 1#-14# is 2.4m, with 7 pairs of rollers distributed in each fan-shaped segment; the fan-shaped segments numbered 1#-7# are located in the arc section of the continuous casting machine, and the fan-shaped segments 8#-14# are located in the horizontal section of the continuous casting machine.

10. The continuous casting billet for seawater corrosion resistant steel produced by the method for producing the continuous casting billet for seawater corrosion resistant steel according to any one of claims 1 to 9, characterized in that: Its chemical composition, in mass percentage, is C: 0.05% - 0.15%, Si: 0.25% - 0.45%, Mn: 0.40% - 0.70%, P: ≤ 0.015%, S: ≤ 0.005%, Al: 0.50% - 0.80%, Cr: 0.90% - 1.20%, Mo: 0.15% - 0.25%, and the rest is Fe and unavoidable impurities.

Images