A method for controlling nitrogen and calcium in the smelting of welding wire steel

Abstract

This invention belongs to the field of metallurgy and steelmaking technology, specifically relating to a smelting method for controlling nitrogen (N) and calcium (Ca) content in welding wire steel. This invention employs optimized alloy blending, combined with LF submerged arc refining and continuous casting with protective casting, replacing VD vacuum denitrification to achieve stable control of N content in the steel. Simultaneously, in the LF refining process, the contradiction between submerged arc heating, deoxidation, and Ca control is resolved through early-stage high-basicity deoxidation followed by slag-induced basicity reduction in the later stage of refining. Combined with full-process protective casting in continuous casting, this further reduces nitrogen accumulation in the ladle. This invention achieves both low production costs and simultaneous control of N and Ca content in welding wire steel. Currently, this method has achieved stable control of N ≤ 40 ppm and Ca ≤ 10 ppm in welding wire steel, demonstrating substantial technical effectiveness and broad market application prospects.

Description

Technical Field

[0001] This invention belongs to the field of metallurgy and steelmaking technology, and specifically relates to a smelting method for controlling N and Ca in welding wire steel. Background Technology

[0002] Nitrogen is a typical "interstitial harmful element" in welding steel. Its hazard stems from rapid dissolution during welding and non-equilibrium precipitation during cooling. It also interacts with other elements in the steel, ultimately affecting welding process stability and joint quality. Ca (Ca) has a negative impact on spatter in solid welding wire: it affects molten pool surface tension, arc ionization characteristics, and inclusion morphology. Especially in gas-shielded welding wire, the Ca content in solid welding wire must be strictly controlled to reduce spatter. Therefore, welding wire steel products have stringent requirements for controlling the N and Ca content. Controlling the N content using conventional vacuum treatment significantly increases production costs. Controlling the Ca content requires low slag basicity, but excessively low slag basicity conflicts with the deoxidation requirements of the welding wire and the need for low-C submerged arc welding. These issues have become challenges in the production control of welding wire steel. Therefore, controlling N and Ca in the smelting technology of welding wire steel has become a critical problem that urgently needs to be solved in my country's steel industry. Summary of the Invention

[0003] The purpose of this invention is to overcome the technical defects existing in the prior art, and thereby provide a method for controlling the N and Ca content in welding wire steel. This method employs alloy optimization, combined with LF submerged arc refining and continuous casting with protective casting, to replace VD vacuum denitrification, achieving stable control of the N content in the steel. Simultaneously, in the LF refining process, the contradiction between submerged arc heating, deoxidation, and Ca control is resolved through early-stage high-basicity heating and deoxidation followed by slag transformation and basicity reduction in the later stage of refining. This method achieves stable control of N and Ca content in welding wire steel at a low level while maintaining production costs. Currently, this method has achieved stable control of N ≤ 40 ppm and Ca ≤ 10 ppm in welding wire steel, yielding substantial technical results.

[0004] To achieve the above objectives, the present invention includes the following steps:

[0005] This invention first provides a welding wire steel, which is composed of the following components by weight percentage:

[0006] C: 0.06%~0.10%, Si: 0.50%~0.70%, Mn: 1.70%~1.95%, P: ≤0.017%, S: 0.004~0.010%, Cr: ≤0.15%, Mo: 0.22~0.30%, Ni: ≤0.15%, V: ≤0.030%, Al: ≤0.02%, N: ≤40ppm, Ca≤10ppm, balance Fe and unavoidable impurities.

[0007] Preferably, it consists of the following components by weight percentage:

[0008] C: 0.06%~0.09%, Si: 0.50%~0.60%, Mn: 1.75%~1.85%, P: ≤0.015%, S: 0.004~0.010%, Cr: ≤0.10%, Mo: 0.22~0.30%, Ni: ≤0.10%, V: ≤0.020%, Al: ≤0.010%, N: ≤40ppm, Ca≤10ppm, with the balance being Fe and unavoidable impurities.

[0009] This invention also provides a method for smelting welding wire steel with controlled nitrogen and calcium content, comprising the following steps:

[0010] I. Converter process:

[0011] (1) Deoxidation and alloying in converter smelting: Steel composition control requirements: C: ≤0.04%, P ≤0.012%, steel tapping temperature ≥1600℃;

[0012] (2) Deoxidation and alloying are carried out during tapping. The operation is as follows: alloys are added after 1 / 3 of the steel is tapped. The alloys include high-silicon ferromanganese and low-carbon ferromanganese. After 2 / 3 of the steel is tapped, lime and fluorite slag-forming materials are added at once to form ladle top slag (refining primary slag).

[0013] (3) After tapping, immediately adjust the argon gas to a weak blowing state, that is, the argon gas flow rate is 10~30NL / min, in order to reduce the absorption of gas and nitrogen by the molten steel;

[0014] Preferably, in step (2) of step one, the amount of high-silicon manganese added is 20~25 kg / t, the amount of low-carbon ferromanganese added is 5~8 kg / t, the amount of lime added is 8~9 kg / t, and the amount of fluorite added is 2~3 kg / t.

[0015] II. Refining Process:

[0016] (1) After the slag is brought into the station, the slag is adjusted according to the slag condition and the slag discharge situation, so that the slag has good fluidity and meets the control target of binary basicity R of 3~4 (which is conducive to deoxidation and top slag foaming to improve the steel protection effect and prevent nitrogen and carbon increase).

[0017] Preferably, in step two (1), the refining slag is adjusted by adding lime and fluorite; wherein the amount of lime added is 0~2Kg / t and the amount of fluorite added is 0~1Kg / t.

[0018] (2) After the submerged arc stabilizes for 3-5 minutes, calcium carbide and ferrosilicon powder are mixed and deoxidized on the slag surface. The mixture is added in batches and evenly sprinkled on the slag surface. The total amount of calcium carbide and ferrosilicon powder is not less than 2 kg / t. Under the condition of ensuring slag surface deoxidation, the temperature is increased for 15-20 minutes at a time. The temperature target is 80°C above the liquidus line (close to the target outlet temperature). By increasing the submerged arc heating and molten steel protection, nitrogen and carbon increase are prevented.

[0019] Preferably, in step (2), the mass ratio of calcium carbide to ferrosilicon powder is 1:2; the target temperature is 80°C above the liquidus line, corresponding to a temperature range of 1605°C to 1618°C.

[0020] (3) Control the dust removal opening during the refining process to maintain a slightly positive pressure atmosphere in the furnace, with a pressure of 10Pa~40Pa (a small amount of flue gas overflows from the water-cooled furnace cover); control the argon stirring intensity during the heating process to 80~120NL / min, and the exposed surface of the target molten steel to be 20~30cm bright ring, so as to ensure the reaction of steel slag, increase the protection of molten steel during the refining process, and reduce the amount of N added during the refining heating process;

[0021] (4) Based on the detected composition, high-silicon ferromanganese, low-carbon ferromanganese, high-purity ferrosilicon and ferromolybdenum are used to adjust the alloy composition. Sulfur wire or ferrosulfite alloy is used to control sulfur. 15 min before the end of refining, it is confirmed that the white slag smelting time is ≥20 min and the temperature meets the casting superheat of 15~30℃. Quartz sand is added to change the slag, so as to achieve the control target of binary basicity of 1.8~2.5, thereby controlling the Ca content in the steel.

[0022] Preferably, in step two (4), the amount of high-silicon ferromanganese added is 0~2Kg / t, the amount of low-carbon ferromanganese added is 1.6~2.8Kg / t, the amount of high-purity ferrosilicon added is 0~1.6Kg / t, the amount of ferromolybdenum added is 3.5~4.5Kg / t, the amount of quartz sand added is 1~2Kg / t, the white slag smelting time is 25~32min, and the temperature meets the requirement of 1608℃~1636℃.

[0023] (5) Soft blowing (based on slight fluctuations in the liquid surface) is maintained for ≥20 min; the outlet temperature is 1565℃~1580℃, and the superheat target is 20~35℃;

[0024] III. Continuous casting process:

[0025] (1) The tundish uses an integral stopper rod. Before casting, the impact zone of the tundish and the intervals between each flow are purged with argon gas. Then, the ladle slide is started to start casting. The target superheat start-up temperature is 30~40℃, the continuous casting temperature is 20~35℃, and the casting speed is controlled at 2.0~2.3m / min. Combined with the electromagnetic stirring of the crystallizer, the crystallizer water flow rate is 2010~2050L / min. The casting process is protected throughout the casting process.

[0026] Preferably, in step three (1), the electromagnetic stirring parameters of the crystallizer are 250A current and 2Hz frequency, and the electromagnetic stirring parameters of the end are 250A current and 10Hz frequency.

[0027] (2) The remaining casting weight in the tundish is ≥3.5t;

[0028] This enabled the controlled smelting of welding wire steel with N ≤ 40 ppm and Ca ≤ 10 ppm.

[0029] Beneficial effects:

[0030] (1) By using alloy optimization, the converter steel is alloyed with high silicon manganese and low carbon ferromanganese. Combined with the operation of adjusting the argon gas to weak blowing immediately after steel tapping, the nitrogen content of the steel tapping can be effectively controlled at a relatively low level (13~25ppm).

[0031] (2) The present invention achieves the goal of controlling high alkalinity in the early stage of refining by adding initial slag-forming material, which is beneficial to refining deoxidation and heating and submerging arc, and solves the problems of refining deoxidation and heating and carbon increase.

[0032] (3) The present invention uses calcium carbide in combination with ferrosilicon powder for deoxidation, submerged arc, combined with dust removal control of a slightly positive pressure atmosphere, and LF bottom blowing weak argon gas stirring to improve the protection effect of top slag on molten steel, thereby controlling the nitrogen increase in the refining process to within 10ppm.

[0033] (4) The present invention further reduces the activity of CaO in the slag by the slag-changing operation in the later stage of refining, which can effectively reduce the Ca content in steel and ensure that Ca≤10 ppm.

[0034] (5) The continuous casting process of the present invention is protected and casting, which helps to reduce nitrogen increase in the tundish. Currently, the nitrogen increase in the tundish can be ≤5ppm.

[0035] (6) Based on the above scheme, alloy optimization and LF submerged arc refining + continuous casting protection casting are adopted to replace VD vacuum denitrification and achieve stable control of N content in steel. At the same time, in the LF refining process, the contradiction between submerged arc heating, deoxidation and Ca control is solved by high basicity heating deoxidation in the early stage and slag transformation and basicity reduction in the later stage of refining. While keeping the production cost at a low level, the development and application of production control technology for N and Ca content in welding wire steel are realized. At present, the stable control of N≤40ppm and Ca≤10ppm in welding wire steel has been achieved through this method, and substantial technical effects have been achieved. Detailed Implementation

[0036] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary. Example 1:

[0039] A welding wire steel (SJA10) is composed of the following components by weight percentage: C: 0.067%, Si: 0.54%, Mn: 1.78%, P: 0.013%, S: 0.006%, Cr: 0.05%, Mo: 0.22%, Ni: 0.014%, V: 0.006%, Al: 0.004%, N: ≤40ppm, Ca ≤10 ppm, with the balance being Fe and unavoidable impurities.

[0040] The smelting method for controlled nitrogen and calcium content in welding wire steel (SJA10) includes the following steps (steel output: 50 tons):

[0041] I. Converter process:

[0042] 1. Converter smelting endpoint control: C: 0.04%, P: 0.0116%, tapping temperature: 1603℃;

[0043] 2. Deoxidation and alloying are carried out during steel tapping. The order and weight of alloying are as follows: start adding after 1 / 3 of the steel has been tapped, adding 1040KG of high-silicon ferromanganese and 258Kg of low-carbon ferromanganese; after 2 / 3 of the steel has been tapped, add 404Kg of lime and 105Kg of fluorite slag-forming material at once to form ladle top slag (refining primary slag).

[0044] 3. After tapping, immediately adjust the argon gas flow rate to 30 NL / min to reduce nitrogen absorption by the molten steel;

[0045] II. Refining Process:

[0046] 1. After the slag enters the station, adjust the refining slag according to the slag condition and the slag discharge situation (30 kg of lime, 0 kg of fluorite) to make the slag have good fluidity and meet the control target of binary basicity R of 3 (which is conducive to deoxidation and top slag foaming to improve the steel protection effect and prevent nitrogen and carbon increase).

[0047] 2. After the submerged arc stabilizes after 3 minutes of heating, calcium carbide and ferrosilicon powder are mixed at a mass ratio of 1:2 for slag surface deoxidation. The mixture is applied evenly to the slag surface in small batches, with a total dosage of 120 kg. This process ensures slag surface deoxidation while enhancing the submerged arc heating effect and the molten steel protection effect (preventing nitrogen and carbon increase). The heating process is carried out for 15 minutes at a temperature of 1605℃.

[0048] 3. During the refining process, the dust removal opening is controlled, and a slight amount of flue gas overflows from the water-cooled furnace cover to maintain a slightly positive pressure atmosphere inside the furnace at a pressure of 30 Pa. During the heating process, the argon stirring intensity is reasonably controlled (100 NL / min), and the target exposed surface of the molten steel is a bright ring of 30 cm. This ensures the reaction of the steel slag while increasing the protection of the molten steel during the refining process and reducing the amount of nitrogen added during the refining heating process.

[0049] 4. Based on the tested components, 120 kg of low-carbon ferromanganese, 39 kg of high-purity ferrosilicon, and 198 kg of ferromolybdenum were used to adjust the alloy composition. Sulfur was controlled using a 20 m sulfur line. 15 min before the end of refining, it was confirmed that the white slag smelting time was 25 min and the temperature met the production requirements (1636℃). 100 kg of quartz sand was added to transform the slag, achieving the control target of binary basicity of 1.8, thereby controlling the Ca content in the steel.

[0050] 5. Soft blowing is based on the standard of slight ripples in the liquid surface, and the holding time is 27 minutes; the outlet temperature is 1570℃;

[0051] III. Continuous casting process:

[0052] 1. The continuous casting uses an integral stopper rod tundish. Before casting, the impact zone of the tundish and the spaces between each flow are purged with argon gas. Then, the ladle slide is started to begin casting. The superheat is 43°C at start-up. The casting speed is controlled at 2.0 m / min. The crystallizer water flow rate is 2050 L / min. The crystallizer electromagnetic stirring parameters are 250 A current and 2 Hz frequency. The end electromagnetic stirring parameters are 250 A current and 10 Hz frequency. The casting process is protected throughout.

[0053] 2. The remaining amount of casting in the intermediate ladle is ≥3.5t. Example 2:

[0054] A welding wire steel (SJA10) is composed of the following components by weight percentage: C: 0.075%, Si: 0.53%, Mn: 1.77%, P: 0.009%, S: 0.006%, Cr: 0.038%, Mo: 0.22%, Ni: 0.010%, V: 0.005%, Al: 0.006%, N: ≤40 ppm, Ca ≤10 ppm, with the balance being Fe and unavoidable impurities.

[0055] The smelting method for controlled nitrogen and calcium content in welding wire steel (SJA10) includes the following steps (50 tons of steel produced):

[0056] I. Converter process:

[0057] 1. Converter smelting endpoint control: C: 0.033%, P: 0.006%, tapping temperature: 1608℃;

[0058] 2. Deoxidation and alloying are carried out during steel tapping. The order and weight of alloying are as follows: start adding after 1 / 3 of the steel has been tapped, with alloying consisting of 1100 kg of high-silicon ferromanganese and 311 kg of low-carbon ferromanganese; after 2 / 3 of the steel has been tapped, add 408 kg of lime and 110 kg of fluorite slag-forming material at once to form ladle top slag (refining primary slag).

[0059] 3. After tapping, immediately adjust the argon gas flow rate to 20 NL / min to reduce nitrogen absorption by the molten steel;

[0060] II. Refining Process:

[0061] 1. After the slag enters the station, adjust the refining slag according to the slag condition and the slag discharge situation (47 kg of lime, 0 kg of fluorite) to make the slag have good fluidity and meet the control target of binary basicity R of 3 (which is conducive to deoxidation and top slag foaming to improve the steel protection effect and prevent nitrogen and carbon increase).

[0062] 2. After stabilizing the submerged arc for 3 minutes, deoxidize the slag surface by mixing calcium carbide and ferrosilicon powder at a mass ratio of 1:2. Apply the mixture evenly to the slag surface in small batches, with a total dosage of 130 kg. This process ensures slag surface deoxidation while enhancing the submerged arc heating effect and protecting the molten steel (preventing nitrogen and carbon accumulation). The heating process is repeated for 15 minutes at a temperature of 1615℃.

[0063] 3. During the refining process, the dust removal opening was controlled, and slight smoke leakage occurred at the water-cooled furnace cover. The argon stirring intensity (110 NL / min) was reasonably controlled during the heating process, with a target 28 cm bright ring on the exposed surface of the molten steel. This was done to ensure the reaction of the steel slag while increasing the protection of the molten steel during the refining process and reducing the amount of nitrogen added during the refining heating process.

[0064] 4. Based on the tested components, adjust the alloy composition using 140 kg of low-carbon ferromanganese, 80 kg of high-purity ferrosilicon, and 201 kg of ferromolybdenum. Control sulfur content using a 30 m sulfur line. 15 minutes before the end of refining, confirm that the white slag smelting time is 32 minutes and the temperature meets the production requirements (1608℃). Add 100 kg of quartz sand to transform the slag, achieving the control target of binary basicity of 1.8, and control the Ca content in the steel.

[0065] 5. Soft blowing is based on the standard of slight ripples in the liquid surface, and the holding time is 26 minutes; the outlet temperature is 1573℃;

[0066] III. Continuous casting process:

[0067] 1. The continuous casting uses an integral stopper rod tundish. Before casting, the impact zone of the tundish and the intervals between each flow are purged with argon gas. Then, the ladle slide is started to begin casting. The superheat is 35°C. The casting speed is controlled at 2.0 m / min. The crystallizer water flow rate is 2050 L / min. The crystallizer electromagnetic stirring parameters are 250 A current and 2 Hz frequency. The end electromagnetic stirring parameters are 250 A current and 10 Hz frequency. The casting process is protected throughout.

[0068] 2. The remaining amount of casting in the intermediate ladle is ≥3.5t. Example 3:

[0069] A welding wire steel (SJA10) is composed of the following components by weight percentage: C: 0.067%, Si: 0.52%, Mn: 1.76%, P: 0.010%, S: 0.008%, Cr: 0.037%, Mo: 0.22%, Ni: 0.011%, V: 0.006%, Al: 0.005%, N: ≤40 ppm, Ca ≤10 ppm, with the balance being Fe and unavoidable impurities.

[0070] The smelting method for controlled nitrogen and calcium content in welding wire steel (SJA10) includes the following steps (50 tons of steel produced):

[0071] I. Converter process:

[0072] 1. Converter smelting endpoint control: C: 0.036%, P: 0.008%, tapping temperature: 1611℃;

[0073] 2. Deoxidation and alloying are carried out during steel tapping. The order and weight of alloying are as follows: start adding after 1 / 3 of the steel has been tapped, with alloying consisting of 1080 kg of high-silicon ferromanganese and 192 kg of low-carbon ferromanganese; after 2 / 3 of the steel has been tapped, add 412 kg of lime and 123 kg of fluorite slag-forming material at once to form ladle top slag (refining primary slag).

[0074] 3. After tapping, immediately adjust the argon gas flow rate to 25 NL / min to reduce nitrogen absorption by the molten steel;

[0075] II. Refining Process:

[0076] 1. After the slag enters the station, adjust the refining slag according to the slag condition and the slag discharge situation (53 kg of lime, 0 kg of fluorite) to make the slag have good fluidity and meet the control target of binary basicity R:3 (which is conducive to deoxidation and top slag foaming to improve the steel protection effect and prevent nitrogen and carbon increase).

[0077] 2. After stabilizing the submerged arc for 3 minutes, deoxidize the slag surface by mixing calcium carbide and ferrosilicon powder at a mass ratio of 1:2. Apply the mixture evenly to the slag surface in small batches, ensuring a total dosage of no less than 120 kg. This process enhances the submerged arc heating effect and the protection of the molten steel (preventing nitrogen and carbon buildup) while ensuring slag surface deoxidation. A single heating cycle of 15 minutes is performed, reaching a temperature of 1618℃.

[0078] 3. During the refining process, the dust removal opening was controlled, and slight smoke leakage occurred at the water-cooled furnace cover. The argon stirring intensity (105 NL / min) was reasonably controlled during the heating process, and a bright ring of 25 cm was achieved on the exposed surface of the target molten steel. This was done to ensure the reaction of the steel slag while increasing the protection of the molten steel during the refining process and reducing the amount of nitrogen added during the refining heating process.

[0079] 4. Based on the tested components, adjust the alloy composition using 80 kg of low-carbon ferromanganese, 0 kg of high-purity ferrosilicon, and 199 kg of ferromolybdenum. Control sulfur content using a 20 m sulfur line. 15 minutes before the end of refining, confirm that the white slag smelting time is 28 minutes and the temperature meets the production requirements (16-15℃). Add 100 kg of quartz sand to transform the slag, achieving the control target of binary basicity of 1.8, and control the Ca content in the steel.

[0080] 5. Soft blowing is based on the standard of slight ripples in the liquid surface, and the holding time is 28 minutes; the outlet temperature is 1575℃;

[0081] III. Continuous casting process:

[0082] 1. The continuous casting uses an integral stopper rod tundish. Before casting, the impact zone of the tundish and the spaces between each flow are purged with argon gas. Then, the ladle slide is started to begin casting. The superheat is 33℃, the casting speed is controlled at 2.0m / min, the crystallizer water flow rate is 2050L / min, the crystallizer electromagnetic stirring parameters are 250A current and 2Hz frequency, and the end electromagnetic stirring parameters are 250A current and 10Hz frequency. The casting process is protected throughout the entire casting process.

[0083] 2. The remaining amount of casting in the intermediate ladle is ≥3.5t.

[0084] Table 1: Control effects of Examples 1-3

[0085]

[0086] As shown in Table 1, the welding wire steel in Example 1 contains 37 ppm N and 4 ppm Ca; the welding wire steel in Example 2 contains 32 ppm N and 6 ppm Ca; and the welding wire steel in Example 3 contains 28 ppm N and 3 ppm Ca.

[0087] This invention demonstrates that by employing optimized alloy composition and combining LF submerged arc refining with continuous casting protection, it replaces VD vacuum denitrification to achieve stable control of N content in steel. Simultaneously, in the LF refining process, the contradiction between submerged arc heating, deoxidation, and Ca control is resolved through early-stage high-basicity deoxidation followed by slag-induced basicity reduction in the later stages of refining. This approach achieves stable control of N and Ca content in welding wire steel while keeping production costs low, demonstrating substantial technical effectiveness. Currently, this method has been used to achieve stable control of N ≤ 40 ppm and Ca ≤ 10 ppm in welding wire steel.

[0088] Although this specification has described the invention in detail with reference to the various embodiments described above, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the invention; and all technical solutions and improvements that do not depart from the spirit and scope of the invention should be covered within the scope of the claims of the invention.

Claims

1. A method for controlling the nitrogen and calcium content in welding wire steel, characterized in that, Welding wire steel is composed of the following components by weight percentage: C: 0.06%~0.10%, Si: 0.50%~0.70%, Mn: 1.70%~1.95%, P: ≤0.017%, S: 0.004~0.010%, Cr: ≤0.15%, Mo: 0.22~0.30%, Ni: ≤0.15%, V: ≤0.030%, Al: ≤0.02%, N: ≤40ppm, Ca≤10ppm, balance Fe and unavoidable impurities; The steps are as follows: I. Converter process: (1) Deoxidation and alloying in converter smelting: Steel composition control requirements: C: ≤0.04%, P ≤0.012%, steel tapping temperature ≥1600℃; (2) Deoxidation and alloying are carried out during tapping. The operation is as follows: alloys are added after 1 / 3 of the steel has been tapped. The alloys include high-silicon ferromanganese and low-carbon ferromanganese. After 2 / 3 of the steel has been tapped, lime and fluorite slag-forming materials are added at once to form the top slag of the ladle. (3) After tapping, immediately adjust the argon gas to a weak blowing state, that is, the argon gas flow rate is 10~30NL / min, in order to reduce the absorption of gas and nitrogen by the molten steel; II. Refining Process: (1) After the slag enters the station, the slag is adjusted according to the slag condition and the slag discharge situation after steel tapping, so that the slag has good fluidity and meets the control target of binary basicity R of 3~4; (2) After the submerged arc stabilizes after heating for 3-5 minutes, calcium carbide and ferrosilicon powder are mixed and deoxidized on the slag surface. The mixture is added in batches and evenly sprinkled on the slag surface. The total amount of calcium carbide and ferrosilicon powder is not less than 2 kg / t. Under the condition of ensuring slag surface deoxidation, the temperature is increased for 15-20 minutes at a time. The temperature target is 80°C above the liquidus line. (3) Control the dust removal opening during the refining process to maintain a slightly positive pressure atmosphere in the furnace, with a pressure of 10Pa~40Pa; control the argon stirring intensity during the heating process to 80~120NL / min, and the exposed surface of the target molten steel to 20~30cm bright ring, so as to ensure the reaction of steel slag, increase the protection of molten steel during the refining process, and reduce the amount of N added during the refining heating process. (4) Based on the detected composition, high-silicon ferromanganese, low-carbon ferromanganese, high-purity ferrosilicon and ferromolybdenum are used to adjust the alloy composition. Sulfur wire or ferrosulfite alloy is used to control sulfur. 15 min before the end of refining, it is confirmed that the white slag smelting time is ≥20 min and the temperature meets the casting superheat of 15~30℃. Quartz sand is added to change the slag, so as to achieve the control target of binary basicity of 1.8~2.5, thereby controlling the Ca content in the steel. (5) Soft blowing holding time ≥20min; outlet temperature 1565℃~1580℃, superheat target 20~35℃; III. Continuous casting process: (1) The tundish uses an integral stopper rod. Before casting, the impact zone of the tundish and the intervals between each flow are purged with argon gas. Then, the ladle slide is started to start casting. The target superheat start-up temperature is 30~40℃, the continuous casting temperature is 20~35℃, and the casting speed is controlled at 2.0~2.3m / min. Combined with the electromagnetic stirring of the crystallizer, the crystallizer water flow rate is 2010~2050L / min. The casting process is protected throughout the casting process. (2) The remaining casting weight in the tundish is ≥3.5t; This enabled the controlled smelting of welding wire steel with N ≤ 40 ppm and Ca ≤ 10 ppm.

2. The smelting method for controlling N and Ca in welding wire steel according to claim 1, characterized in that: The chemical composition consists of the following components by weight percentage: C: 0.06%~0.09%, Si: 0.50%~0.60%, Mn: 1.75%~1.85%, P: ≤0.015%, S: 0.004~0.010%, Cr: ≤0.10%, Mo: 0.22~0.30%, Ni: ≤0.10%, V: ≤0.020%, Al: ≤0.010%, N: ≤40ppm, Ca≤10ppm, with the balance being Fe and unavoidable impurities.

3. The smelting method for controlled N and Ca content in welding wire steel according to claim 1, characterized in that: In step one (2), the amount of high-silicon manganese added is 20~25kg / t, low-carbon ferromanganese is 5~8kg / t, lime is 8~9kg / t, and fluorite is 2~3kg / t.

4. The smelting method for controlling N and Ca in welding wire steel according to claim 1, characterized in that: In step two (1), the refining slag is adjusted by adding lime and fluorite; the amount of lime added is 0~2Kg / t, and the amount of fluorite added is 0~1Kg / t.

5. The smelting method for controlled N and Ca content in welding wire steel according to claim 1, characterized in that: In step 2 (2), the mass ratio of calcium carbide to ferrosilicon powder is 1:2; the target temperature is 80°C above the liquidus line, corresponding to a temperature range of 1605°C to 1618°C.

6. The smelting method for controlling N and Ca in welding wire steel according to claim 1, characterized in that: In step two (4), the amount of high-silicon ferromanganese added is 0~2Kg / t, the amount of low-carbon ferromanganese added is 1.6~2.8Kg / t, the amount of high-purity ferrosilicon added is 0~1.6Kg / t, the amount of ferromolybdenum added is 3.5~4.5Kg / t, and the amount of quartz sand added is 1~2Kg / t.

7. The smelting method for controlling N and Ca in welding wire steel according to claim 1, characterized in that: In step 2 (4), the smelting time for white slag is 25~32 min; the temperature is 1608℃~1636℃.

8. The smelting method for controlling N and Ca in welding wire steel according to claim 1, characterized in that: In step 3 (1), the electromagnetic stirring parameters of the crystallizer are 250A current and 2Hz frequency, and the electromagnetic stirring parameters of the end are 250A current and 10Hz frequency.

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