CN117718451A - Control method for surface and submerged bubbles of continuous casting billet for high-carbon steel wire rod - Google Patents
Control method for surface and submerged bubbles of continuous casting billet for high-carbon steel wire rod Download PDFInfo
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Abstract
The invention relates to the technical field of steelmaking continuous casting, in particular to a control method of continuous casting billet surface and submerged bubbles for high-carbon steel wire rods, which comprises the following steps: in the continuous casting process of producing the continuous casting billet for the high-carbon steel wire rod, the total slag layer thickness of the casting powder in the crystallizer is controlled to be 50-60mm, the liquid slag layer thickness of the casting powder in the crystallizer is controlled to be 2-3mm, the electromagnetic induction intensity of the meniscus position of molten steel in the crystallizer is 20-30mT, and the oxygen content in the molten steel is less than or equal to 0.0025%. The method can obviously reduce the defects of CO bubbles formed on the surface and subcutaneous of the high-carbon steel continuous casting blank due to carbon and oxygen of molten steel on the premise of not increasing smelting cost and not influencing the metal yield of the continuous casting blank, and reduce the occurrence rate of the bubbles on the surface and subcutaneous to below 10%, thereby greatly improving the product quality.
Description
Technical Field
The invention relates to the technical field of steelmaking continuous casting, in particular to a control method for continuous casting billet surface and submerged bubbles for high-carbon steel wire rods.
Background
High-carbon steel wire rods with the C content of 0.72-1.00% are widely applied to the technical fields of automobiles, machinery, bridges and the like, and strict requirements are imposed on the surface and subcutaneous quality of continuous casting blanks for producing wire rods due to the special application, however, the surface and subcutaneous of the continuous casting blanks are often accompanied by defects such as slag inclusion, cracks, bubbles and the like. In the solidification process of molten steel, bubbles are generated when partial pressure of CO, H, N and other gases generated by reaction of carbon and oxygen in the steel is larger than the sum of hydrostatic pressure and atmospheric pressure, and if the bubbles are blocked by a solidified surface layer or captured by dendrites, continuous casting billet surface and subcutaneous bubbles are formed. The surface of the continuous casting blank and part of the subcutaneous bubbles cannot be rolled, so that the surface of the wire rod can be subjected to defects such as scab, crack, folding and the like, and the performance of the wire rod is further affected. Therefore, the surface and submerged bubbles of the continuous casting billet for the high-carbon steel wire rod need to be controlled.
Chinese patent document CN102634728A discloses a continuous casting process for small billets of Fe-Mn-C high manganese steel, which mainly adopts a whole-course protection casting mode to prevent secondary oxidation of molten steel by air and a series of defects such as subcutaneous bubbles, slag inclusion and inclusion caused by the secondary oxidation. In addition, through adopting the electromagnetic stirring of the crystallizer, gas and inclusions in the molten steel are promoted to float upwards and be removed, dendrites are broken, and the grains are delayed to be engulfed and grow up. However, the controlled bubble types are bubbles caused by secondary oxidation of molten steel, and the problem of how to reduce the occurrence of CO bubbles formed on the surface and subcutaneously of a high-carbon steel continuous casting blank due to carbon and oxygen of the molten steel and control the occurrence rate within 10 percent, without increasing the smelting cost and affecting the metal yield of the continuous casting blank is still to be solved.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to overcome the defect that the existing continuous casting production process cannot reduce the occurrence of CO bubbles formed on the surface and subcutaneous of a high-carbon steel continuous casting blank due to carbon and oxygen of molten steel under the premise of not increasing smelting cost and not affecting the metal yield of the continuous casting blank, and to control the occurrence rate to be within 10%, so as to provide a control method for the surface and subcutaneous bubbles of the continuous casting blank for the high-carbon steel wire rod.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a control method of continuous casting billet surface and submerged bubbles for high-carbon steel wire rods comprises the following steps: in the continuous casting process of producing the continuous casting billet for the high-carbon steel wire rod, the total slag layer thickness of the casting powder in the crystallizer is controlled to be 50-60mm, the liquid slag layer thickness of the casting powder in the crystallizer is controlled to be 2-3mm, the electromagnetic induction intensity of the meniscus position of molten steel in the crystallizer is 20-30mT, and the oxygen content in the molten steel is less than or equal to 0.0025%.
Preferably, the vibration mark depth of the continuous casting blank is 70-180 mu m;
and/or the depth of a solidification hook of the continuous casting blank is 180-350 mu m;
and/or the thickness of the copper pipe wall covering slag ring at the meniscus position of the molten steel in the crystallizer is less than or equal to 3mm;
and/or the amplitude of the crystallizer is 2-6mm;
and/or the vibration frequency of the crystallizer is 100-160cpm;
and/or, the oxygen content in the molten steel is 0.0015-0.0025%.
Preferably, the vibration mark depth of the continuous casting blank is 80-150 mu m;
and/or the depth of a solidification hook of the continuous casting blank is 200-300 mu m;
and/or the amplitude of the crystallizer is 3-5mm;
and/or the vibration frequency of the crystallizer is 120-140cpm.
Preferably, the electromagnetic stirring current of the electromagnetic stirrer arranged in the crystallizer is 600-800A;
and/or the electromagnetic stirring frequency of the electromagnetic stirrer arranged in the crystallizer is 1-2Hz;
and/or the height of the electromagnetic stirrer arranged in the crystallizer is 500mm;
and/or the lower edge of the built-in electromagnetic stirrer of the crystallizer is 100mm higher than the lower edge of the copper pipe of the crystallizer.
Preferably, the immersed nozzle of the crystallizer is an integral four-hole nozzle;
and/or, the copper pipe corner of the crystallizer is opposite to the steel outflow port;
and/or the immersion nozzle of the crystallizer has an insertion depth of 160-180mm;
and/or the length of the copper pipe of the crystallizer is 900mm;
and/or, the meniscus of molten steel in the crystallizer is 80-120mm below the upper edge of the copper pipe.
Preferably, the covering slag comprises the following components in percentage by mass: 30-34% SiO 2 、20-23％CaO、1.0-2.0％MgO、2.0-4.0％Al 2 O 3 、10-12％Na 2 O、7-9％F、9-11％C、2-3％Fe 2 O 3 The balance of unavoidable impurities;
and/or the binary alkalinity of the covering slag is 0.60-0.70;
and/or, the melting point of the covering slag is 960-990 ℃;
and/or the viscosity of the covering slag at 1300 ℃ is 0.30-0.40 Pa.s;
and/or the melting speed of the mold flux is 10-20s.
Preferably, in the continuous casting process, the superheat degree of the molten steel in the tundish is 10-20 ℃, the continuous casting pulling speed is 0.4-0.8m/min, the cooling water flow of the crystallizer is 2800-3200L/min, and the fluctuation range of the liquid level of the crystallizer is +/-1-3 mm.
Preferably, the continuous casting fracture surface size adopted in the continuous casting process is 300mm multiplied by 390mm to 410mm multiplied by 530mm;
and/or, the C content of the high carbon steel wire rod is 0.72-1.00%;
and/or, the primary refining process and the refining process are sequentially carried out before the continuous casting process.
Preferably, ferrosilicon and a carburant are sequentially added in the primary smelting process in the tapping process for deoxidation, and lime and silicon carbide are added after tapping is finished for slagging and slag surface deoxidation.
Preferably, in the refining process, slag and alloy are added to molten steel treated in the primary refining process, the binary alkalinity of refined final slag is 2-3, the FeO+MnO content in refined final slag is less than or equal to 2wt%, the smelting time is 40-50min, and the soft stirring time is 15-25min.
In the invention, the copper pipe wall casting powder slag ring at the meniscus position of molten steel in the crystallizer is a high temperature gradient of liquid slag in contact with the wall of the crystallizer, and a solid slag ring is formed at the periphery of the crystallizer and is adhered to the wall of the crystallizer. Once forming the slag ring, because of the difference of the wetting degree of liquid slag and molten steel with the copper pipe wall, a vertical downward capillary channel is formed between the meniscus slag ring around the crystallizer and the primary blank shell, and because of the effects of the vibration and capillary phenomenon of the crystallizer, the liquid slag on the meniscus is continuously sucked into the air gap between the blank shell and the copper pipe wall to form a slag film, thereby playing a role of lubrication.
The technical scheme of the invention has the following advantages:
1. a control method of continuous casting billet surface and submerged bubbles for high-carbon steel wire rods comprises the following steps: in the continuous casting process of producing the continuous casting billet for the high-carbon steel wire rod, the total slag layer thickness of the casting powder in the crystallizer is controlled to be 50-60mm, the liquid slag layer thickness of the casting powder in the crystallizer is controlled to be 2-3mm, the electromagnetic induction intensity of the meniscus position of molten steel in the crystallizer is 20-30mT, and the oxygen content in the molten steel is less than or equal to 0.0025%. The invention strictly controls the total slag layer and the thickness of the liquid slag layer of the covering slag in the crystallizer and the electromagnetic induction intensity of the meniscus position of molten steel in the crystallizer in the high-carbon steel production process, thereby avoiding carburetion on the surface of the continuous casting blank, and simultaneously combines with the control of the oxygen content of the molten steel in the refining process, thereby reducing the incidence of CO bubbles formed on the surface and under the skin of the high-carbon steel continuous casting blank due to the carbon and oxygen of the molten steel to below 10 percent on the premise of not increasing the smelting cost and not influencing the metal yield of the continuous casting blank.
2. According to the content of the steel grade C and the section size of the continuous casting machine, the thickness of the casting powder ring in the crystallizer is controlled by controlling the thickness of the casting powder layer in the crystallizer, if the thickness of the casting powder layer is too thick, a thicker slag ring is easily formed on the copper pipe wall at the meniscus position of molten steel in the crystallizer, the liquid slag layer is prevented from flowing into the gap between the copper pipe and the continuous casting blank shell, and the lubricating performance of the casting powder is influenced; if the mold flux layer is too thin, a stable three-layer (powder slag layer, sintered layer and liquid slag layer) structure cannot be formed above the meniscus of molten steel in the crystallizer, the inflow of the mold flux liquid slag layer is insufficient, the lubricating performance is also affected, and carburetion on the surface of a continuous casting blank is easy to occur.
3. The invention controls the high Fe content in the protective slag 2 O 3 The content of the flux is used as a fluxing agent, which is favorable for forming a liquid slag layer, simultaneously controls the insertion depth of a water gap, electromagnetic stirring of a crystallizer and the like, and improves the temperature of meniscus molten steel, so that a stable thickness of the liquid slag layer is formed. Meanwhile, by setting vibration parameters (vibration frequency and vibration amplitude) of the crystallizer and combining continuous casting drawing speed, controlling the depth of vibration marks and the depth of a solidification hook, and reducing microscopic segregation of C element in a molten steel overflow area at the position of the solidification hook; and the fluctuation range of the liquid level of the crystallizer is controlled, so that the damage to the protective slag structure at the meniscus position of molten steel is avoided.
4. According to the invention, by adjusting the installation position of the electromagnetic stirrer of the crystallizer and setting the electromagnetic stirring parameters of the crystallizer, the magnetic induction intensity of the meniscus position is effectively controlled, so that the dendritic crystal structure of the solidification front edge of the continuous casting blank is broken, the capture of bubbles at the solidification interface position is reduced, the bubbles are promoted to float upwards and be removed, and meanwhile, slag coiling caused by excessive disturbance of the molten steel surface is avoided.
5. According to the invention, through the control of parameter conditions of each step, the micro segregation of C element in the molten steel overflow area at the carburetion and solidification hook position of the continuous casting billet is reduced, and the CO bubbles formed on the surface and under the skin of the continuous casting billet for the high-carbon steel wire rod can be completely eliminated by combining the control of the oxygen content of the molten steel in the refining process.
Detailed Description
The following examples are provided for a better understanding of the present invention and are not limited to the preferred embodiments described herein, but are not intended to limit the scope of the invention, any product which is the same or similar to the present invention, whether in light of the present teachings or in combination with other prior art features, falls within the scope of the present invention.
The specific experimental procedures or conditions are not noted in the examples and may be followed by the operations or conditions of conventional experimental procedures described in the literature in this field. The reagents or apparatus used were conventional reagent products commercially available without the manufacturer's knowledge.
Example 1
The embodiment provides a control method of continuous casting billet surface and submerged bubbles for high-carbon steel wire rods, wherein the steel grade is SWRH72A, the C content is 0.72%, the continuous casting section size is 300mm multiplied by 390mm, the height of an electromagnetic stirrer of a crystallizer is 500mm, the lower edge of the electromagnetic stirrer is 100mm higher than the lower edge of a copper pipe of the crystallizer, the length of the copper pipe of the crystallizer is 900mm, and the meniscus of molten steel in the crystallizer is 120mm below the upper edge of the copper pipe;
the method specifically comprises the following steps:
1) The primary smelting process comprises the steps of sequentially adding ferrosilicon, manganese silicon and a carburant for deoxidization in the tapping process, and adding lime and silicon carbide for slagging and deoxidizing a slag surface after tapping; adding slag and alloy into the molten steel treated in the primary refining process in the subsequent refining process, wherein the binary alkalinity of the refined final slag is 2, the FeO+MnO content in the refined final slag is 2%, the smelting time is 40min, the soft stirring time is 15min, and the oxygen content in the molten steel is controlled to be 0.0025%;
2) After refining process smelting is finished, lifting molten steel to a continuous casting platform for protection casting, wherein the superheat degree of the molten steel in a tundish is 20 ℃, the molten steel flows into a crystallizer from the tundish through a submerged nozzle, the submerged nozzle is an integral four-hole nozzle, a steel outflow opening corresponds to the corner of a copper pipe of the crystallizer, the insertion depth of the submerged nozzle of the crystallizer is 160mm, the continuous casting pulling speed is 0.8m/min, the cooling water flow of the crystallizer is 2800L/min, the electromagnetic stirring parameters of the crystallizer are 600A and 1Hz, the electromagnetic induction intensity of the meniscus position of the molten steel in the crystallizer is 20mT, and the fluctuation range of the liquid level of the crystallizer is +/-2 mm;
3) The continuous casting crystallizer adopts casting powder for casting, and the casting powder comprises the following chemical components in percentage by mass: 33% SiO 2 、23％CaO、1.0％MgO、3.0％Al 2 O 3 、11％Na 2 O、8％F、9％C、3％Fe 2 O 3 The balance of unavoidable impurities, and the binary alkalinity of the protecting slag(R) is 0.70, the melting point is 990 ℃, the viscosity at 1300 ℃ is 0.35 Pa.s, and the melting speed is 10s;
4) Adding the protective slag by adopting an automatic slag adding device, wherein the total slag layer thickness of the protective slag is 60mm, the liquid slag layer thickness is 3mm, and the thickness of a protective slag ring is 3mm;
5) The vibration parameter of the crystallizer is amplitude 5mm and vibration frequency 140cpm;
6) And (3) discharging the casting blank from the crystallizer, cooling in a secondary cooling area, and cutting by flame to obtain the continuous casting blank, wherein the vibration mark depth is 150 mu m, and the solidification hook depth is 300 mu m.
Example 2
The embodiment provides a control method of continuous casting billet surface and submerged bubbles for high-carbon steel wire rods, wherein the steel grade is SWRH82A, the C content is 0.82%, the continuous casting section size is 350mm multiplied by 450mm, the height of an electromagnetic stirrer of a crystallizer is 500mm, the lower edge of the electromagnetic stirrer is 100mm higher than the lower edge of a copper pipe of the crystallizer, the length of the copper pipe of the crystallizer is 900mm, and the meniscus of molten steel in the crystallizer is 100mm below the upper edge of the copper pipe;
the method specifically comprises the following steps:
1) The primary smelting process comprises the steps of sequentially adding ferrosilicon, manganese silicon and a carburant for deoxidization in the tapping process, and adding lime and silicon carbide for slagging and deoxidizing a slag surface after tapping; adding slag and alloy into the molten steel treated in the primary refining process in the subsequent refining process, wherein the binary alkalinity of the refined final slag is 2.5, the FeO+MnO content in the refined final slag is 1.5%, the smelting time is 45min, the soft stirring time is 20min, and the oxygen content in the molten steel is controlled to be 0.0020%;
2) After refining process smelting is finished, molten steel is lifted to a continuous casting platform for protection casting, the superheat degree of the molten steel in a tundish is 15 ℃, the molten steel flows into a crystallizer from the tundish through a submerged nozzle, the submerged nozzle is an integral four-hole nozzle, a steel outflow opening corresponds to the corner of a copper pipe of the crystallizer, the insertion depth of the submerged nozzle of the crystallizer is 170mm, the continuous casting pulling speed is 0.6m/min, the cooling water flow of the crystallizer is 3000L/min, the electromagnetic stirring parameters of the crystallizer are 700A and 1.5Hz, the electromagnetic induction intensity of the meniscus position of the molten steel in the crystallizer is 25mT, and the fluctuation range of the liquid level of the crystallizer is +/-1.5 mm.
3) The continuous casting crystallizer adopts casting powder for casting, and the casting powder comprises the following chemical components in percentage by mass: 30% SiO 2 、22％CaO、1.5％MgO、4.0％Al 2 O 3 、12％Na 2 O、7％F、11％C、2.5％Fe 2 O 3 The balance of unavoidable impurities, wherein the binary basicity (R) of the covering slag is 0.65, the melting point is 975 ℃, the viscosity at 1300 ℃ is 0.40 Pa.s, and the melting speed is 15s.
4) And adding the covering slag by adopting an automatic slag adding device, wherein the total slag layer thickness of the covering slag is 55mm, the liquid slag layer thickness is 2mm, and the covering slag ring thickness is 2mm.
5) The vibration parameter of the crystallizer is amplitude 4mm and vibration frequency 130cpm.
6) And (3) the casting blank is discharged from the crystallizer, cooled in a secondary cooling area and cut by flame, so that the continuous casting blank is obtained, the vibration mark depth is 100 mu m, and the depth of a solidification hook is 240 mu m.
Example 3
The embodiment provides a control method of continuous casting billet surface and submerged bubbles for high-carbon steel wire rods, wherein the steel grade is SWRH92A, the C content is 0.92%, the continuous casting section size is 410mm multiplied by 530mm, the height of an electromagnetic stirrer of a crystallizer is 500mm, the lower edge of the electromagnetic stirrer is 100mm higher than the lower edge of a copper pipe of the crystallizer, the length of the copper pipe of the crystallizer is 900mm, and the meniscus of molten steel in the crystallizer is 80mm below the upper edge of the copper pipe;
the method specifically comprises the following steps:
1) The primary smelting process comprises the steps of sequentially adding ferrosilicon, manganese silicon and a carburant for deoxidization in the tapping process, and adding lime and silicon carbide for slagging and deoxidizing a slag surface after tapping; adding slag and alloy into the molten steel treated in the primary refining process in the subsequent refining process, wherein the binary alkalinity of the refined final slag is 3, the FeO+MnO content in the refined final slag is 1%, the smelting time is 50min, the soft stirring time is 20min, and the oxygen content in the molten steel is controlled to be 0.0015%;
2) After refining process smelting is finished, lifting molten steel to a continuous casting platform for protection casting, wherein the superheat degree of the molten steel in a tundish is 10 ℃, the molten steel flows into a crystallizer from the tundish through a submerged nozzle, the submerged nozzle is an integral four-hole nozzle, a steel outflow opening corresponds to the corner of a copper pipe of the crystallizer, the insertion depth of the submerged nozzle of the crystallizer is 180mm, the continuous casting pulling speed is 0.4m/min, the cooling water flow of the crystallizer is 3200L/min, the electromagnetic stirring parameters of the crystallizer are 800A and 2.0Hz, the electromagnetic induction intensity of the meniscus position of the molten steel in the crystallizer is 30mT, and the fluctuation range of the liquid level of the crystallizer is +/-1 mm;
3) The continuous casting crystallizer adopts casting powder for casting, and the casting powder comprises the following chemical components in percentage by mass: 34% SiO 2 、21％CaO、2.0％MgO、2.0％Al 2 O 3 、10％Na 2 O、9％F、10％C、2％Fe 2 O 3 The balance of unavoidable impurities, wherein the binary basicity (R) of the covering slag is 0.62, the melting point is 963 ℃, the viscosity at 1300 ℃ is 0.31 Pa.s, and the melting speed is 19s;
4) Adding the protective slag by adopting an automatic slag adding device, wherein the total slag layer thickness of the protective slag is 60mm, the liquid slag layer thickness is 3mm, and the thickness of a protective slag ring is 3mm;
5) The vibration parameter of the crystallizer is amplitude 3mm, and the vibration frequency is 120cpm;
6) And (3) discharging the casting blank from the crystallizer, cooling in a secondary cooling area, and cutting by flame to obtain the continuous casting blank, wherein the vibration mark depth is 80 mu m, and the solidification hook depth is 200 mu m.
Example 4
The difference between this example and example 1 is that the vibration parameter of the mold was 2mm in amplitude and 100cpm in vibration frequency, and the other conditions were the same as those of example 1, and the cast slab was taken out of the mold, cooled in a secondary cooling zone and flame cut to obtain a continuous cast slab having a vibration mark depth of 70 μm and a solidification hook depth of 180 μm.
Example 5
The difference between this example and example 1 is that the vibration parameter of the mold was 6mm in amplitude, 160cpm in vibration frequency, and the other conditions were the same as those of example 1, and the cast slab was taken out of the mold, cooled in a secondary cooling zone and flame cut to obtain a continuous cast slab with a vibration mark depth of 180 μm and a solidification hook depth of 350 μm.
Comparative example 1
The comparative example provides a control method of continuous casting billet surface and submerged bubbles for high-carbon steel wire rods, wherein the steel grade is SWRH72A, the C content is 0.72%, the continuous casting section size is 300mm multiplied by 390mm, the height of an electromagnetic stirrer of a crystallizer is 500mm, the lower edge of the electromagnetic stirrer is 100mm with the lower edge of a copper pipe of the crystallizer, the length of the copper pipe of the crystallizer is 900mm, and the meniscus of molten steel in the crystallizer is 120mm below the upper edge of the copper pipe;
the method specifically comprises the following steps:
1) The primary smelting process comprises the steps of sequentially adding ferrosilicon, manganese silicon and a carburant for deoxidization in the tapping process, and adding lime and silicon carbide for slagging and deoxidizing a slag surface after tapping; adding slag and alloy into the molten steel treated in the primary refining process in the subsequent refining process, wherein the binary alkalinity of the refined final slag is 2, the FeO+MnO content in the refined final slag is 2%, the smelting time is 40min, the soft stirring time is 15min, and the oxygen content in the molten steel is controlled to be 0.0025%;
2) After refining process smelting is finished, lifting molten steel to a continuous casting platform for protection casting, wherein the superheat degree of the molten steel in a tundish is 20 ℃, the molten steel flows into a crystallizer from the tundish through a submerged nozzle, the submerged nozzle is an integral four-hole nozzle, a steel outflow opening corresponds to the corner of a copper pipe of the crystallizer, the insertion depth of the submerged nozzle of the crystallizer is 160mm, the continuous casting pulling speed is 0.8m/min, the cooling water flow of the crystallizer is 2800L/min, the electromagnetic stirring parameters of the crystallizer are 600A and 1Hz, the electromagnetic induction intensity of the meniscus position of the molten steel in the crystallizer is 20mT, and the fluctuation range of the liquid level of the crystallizer is +/-2 mm;
3) The continuous casting crystallizer adopts casting powder for casting, and the casting powder comprises the following chemical components in percentage by mass: 33% SiO 2 、23％CaO、1.0％MgO、3.0％Al 2 O 3 、11％Na 2 O、8％F、9％C、3％Fe 2 O 3 The balance of unavoidable impurities, wherein the binary basicity (R) of the covering slag is 0.70, the melting point is 990 ℃, the viscosity at 1300 ℃ is 0.35 Pa.s, and the melting speed is 10s;
4) Adding the protective slag by adopting an automatic slag adding device, wherein the total slag layer thickness of the protective slag is 30mm, the liquid slag layer thickness is 1mm, and the thickness of a protective slag ring is 1mm;
5) The vibration parameter of the crystallizer is amplitude 5mm and vibration frequency 140cpm;
6) And (3) discharging the casting blank from the crystallizer, cooling in a secondary cooling area, and cutting by flame to obtain the continuous casting blank, wherein the vibration mark depth is 150 mu m, and the solidification hook depth is 300 mu m.
Comparative example 2
The comparative example provides a control method of continuous casting billet surface and submerged bubbles for high-carbon steel wire rods, wherein the steel grade is SWRH72A, the C content is 0.72%, the continuous casting section size is 300mm multiplied by 390mm, the height of an electromagnetic stirrer of a crystallizer is 500mm, the lower edge of the electromagnetic stirrer is 100mm higher than the lower edge of a copper pipe of the crystallizer, the length of the copper pipe of the crystallizer is 900mm, and the meniscus of molten steel in the crystallizer is 120mm below the upper edge of the copper pipe;
the method specifically comprises the following steps:
1) The primary smelting process comprises the steps of sequentially adding ferrosilicon, manganese silicon and a carburant for deoxidization in the tapping process, and adding lime and silicon carbide for slagging and deoxidizing a slag surface after tapping; adding slag and alloy into the molten steel treated in the primary refining process in the subsequent refining process, wherein the binary alkalinity of the refined final slag is 2, the FeO+MnO content in the refined final slag is 2%, the smelting time is 40min, the soft stirring time is 15min, and the oxygen content in the molten steel is controlled to be 0.0025%;
2) After refining process smelting is finished, lifting molten steel to a continuous casting platform for protection casting, wherein the superheat degree of the molten steel in a tundish is 20 ℃, the molten steel flows into a crystallizer from the tundish through a submerged nozzle, the submerged nozzle is an integral four-hole nozzle, a steel outflow opening corresponds to the corner of a copper pipe of the crystallizer, the insertion depth of the submerged nozzle of the crystallizer is 160mm, the continuous casting pulling speed is 0.8m/min, the cooling water flow of the crystallizer is 2800L/min, the electromagnetic stirring parameters of the crystallizer are 600A and 1Hz, the electromagnetic induction intensity of the meniscus position of the molten steel in the crystallizer is 20mT, and the fluctuation range of the liquid level of the crystallizer is +/-2 mm;
3) The continuous casting crystallizer adopts casting powder for casting, and the casting powder comprises the following chemical components in percentage by mass: 33% SiO 2 、23％CaO、1.0％MgO、3.0％Al 2 O 3 、11％Na 2 O、8％F、9％C、3％Fe 2 O 3 The balance of unavoidable impurities, wherein the binary alkalinity (R) is 0.70, the melting point is 990 ℃, the viscosity at 1300 ℃ is 0.35 Pa.s, and the melting speed is 10s;
4) Adding the protective slag by adopting an automatic slag adding device, wherein the total slag layer thickness of the protective slag is 80mm, the liquid slag layer thickness is 5mm, and the thickness of a protective slag ring is 6mm;
5) The vibration parameter of the crystallizer is amplitude 5mm and vibration frequency 140cpm;
6) And (3) discharging the casting blank from the crystallizer, cooling in a secondary cooling area, and cutting by flame to obtain the continuous casting blank, wherein the vibration mark depth is 150 mu m, and the solidification hook depth is 300 mu m.
Comparative example 3
The comparative example was different from example 1 in that the electromagnetic induction intensity at the meniscus position of molten steel in the mold was 0mT, and the other conditions were the same as in example 1.
Comparative example 4
This comparative example is different from example 1 in that the oxygen content in molten steel was controlled to 0.0040% and the other conditions were the same as in example 1.
Test example 1
The surface metallographic structures of the continuous casting billets prepared in examples 1 to 5 and comparative examples 1 to 4 were analyzed and counted, and the statistical method is as follows: counting the surface and subsurface air bubble conditions of 500 continuous casting billets generated by the corresponding scheme, wherein the results are shown in the following table 1; wherein, the occurrence rate of surface and subcutaneous air bubbles (%) = number of continuous casting billets with surface and subcutaneous air bubbles/500×100%.
TABLE 1
| Surface and subsurface bubble incidence (%) | |
| Example 1 | 0.0 |
| Example 2 | 0.0 |
| Example 3 | 0.0 |
| Example 4 | 0.5 |
| Example 5 | 7.5 |
| Comparative example 1 | 50.7 |
| Comparative example 2 | 43.1 |
| Comparative example 3 | 21.2 |
| Comparative example 4 | 14.9 |
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.
Claims (10)
1. The control method of the surface and submerged bubbles of the continuous casting billet for the high-carbon steel wire rod is characterized by comprising the following steps: in the continuous casting process of producing the continuous casting billet for the high-carbon steel wire rod, the total slag layer thickness of the casting powder in the crystallizer is controlled to be 50-60mm, the liquid slag layer thickness of the casting powder in the crystallizer is controlled to be 2-3mm, the electromagnetic induction intensity of the meniscus position of molten steel in the crystallizer is 20-30mT, and the oxygen content in the molten steel is less than or equal to 0.0025%.
2. The control method according to claim 1, wherein the strand has a trace depth of 70 to 180 μm;
and/or the depth of a solidification hook of the continuous casting blank is 180-350 mu m;
and/or the thickness of the copper pipe wall covering slag ring at the meniscus position of the molten steel in the crystallizer is less than or equal to 3mm;
and/or the amplitude of the crystallizer is 2-6mm;
and/or the vibration frequency of the crystallizer is 100-160cpm;
and/or, the oxygen content in the molten steel is 0.0015-0.0025%.
3. The control method according to claim 2, wherein the strand has a trace depth of 80 to 150 μm;
and/or the depth of a solidification hook of the continuous casting blank is 200-300 mu m;
and/or the amplitude of the crystallizer is 3-5mm;
and/or the vibration frequency of the crystallizer is 120-140cpm.
4. A control method according to any one of claims 1 to 3, wherein the electromagnetic stirring current of the electromagnetic stirrer built in the crystallizer is 600 to 800A;
and/or the electromagnetic stirring frequency of the electromagnetic stirrer arranged in the crystallizer is 1-2Hz;
and/or the height of the electromagnetic stirrer arranged in the crystallizer is 500mm;
and/or the lower edge of the built-in electromagnetic stirrer of the crystallizer is 100mm higher than the lower edge of the copper pipe of the crystallizer.
5. The control method according to any one of claims 1 to 4, characterized in that the submerged nozzle of the mould is a monolithic four-hole nozzle;
and/or, the copper pipe corner of the crystallizer is opposite to the steel outflow port;
and/or the immersion nozzle of the crystallizer has an insertion depth of 160-180mm;
and/or the length of the copper pipe of the crystallizer is 900mm;
and/or, the meniscus of molten steel in the crystallizer is 80-120mm below the upper edge of the copper pipe.
6. The control method according to any one of claims 1 to 5, characterized in that the mold flux comprises the following components in mass percent: 30-34% SiO 2 、20-23％CaO、1.0-2.0％MgO、2.0-4.0％Al 2 O 3 、10-12％Na 2 O、7-9％F、9-11％C、2-3％Fe 2 O 3 The balance of unavoidable impurities;
and/or the binary alkalinity of the covering slag is 0.60-0.70;
and/or, the melting point of the covering slag is 960-990 ℃;
and/or the viscosity of the covering slag at 1300 ℃ is 0.30-0.40 Pa.s;
and/or the melting speed of the mold flux is 10-20s.
7. The control method according to any one of claims 1 to 6, wherein in the continuous casting process, the superheat degree of the molten steel in the tundish is 10 to 20 ℃, the continuous casting drawing speed is 0.4 to 0.8m/min, the cooling water flow rate of the crystallizer is 2800 to 3200L/min, and the fluctuation range of the liquid level of the crystallizer is +/-1 to 3mm.
8. The control method according to any one of claims 1 to 7, wherein the continuous casting machine section used in the continuous casting process has a cross-sectional dimension of 300mm x 390mm to 410mm x 530mm;
and/or, the C content of the high carbon steel wire rod is 0.72-1.00%;
and/or, the primary refining process and the refining process are sequentially carried out before the continuous casting process.
9. The control method according to claim 8, wherein the primary smelting step is performed by sequentially adding ferrosilicon, and a carburettor for deoxidation during tapping, and lime and silicon carbide for slagging and slag surface deoxidation after tapping is completed.
10. The control method according to claim 8 or 9, wherein in the refining step, slag and alloy are added to the molten steel treated in the primary refining step, the binary basicity of the refined slag is 2-3, the FeO+MnO content in the refined slag is less than or equal to 2wt%, the smelting time is 40-50min, and the soft stirring time is 15-25min.
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