A high-purity nickel-based steel and a method for producing the same

Abstract

The present application relates to the technical field of steel metallurgy, and particularly relates to a high-purity nickel system steel and a production method thereof, chemical components and mass percentages are as follows: C: 0.030%-0.055%, Si: 0.10%-0.30%, Mn: 0.50%-0.80%, P: <=0.005%, S: <=0.002%, Cr: <=0.30%, Mo: <=0.30%, Ni: 0.50%-1.0%, Cu: <=0.05, Al: 0.020%-0.050%, N: <=0.0045%, H: <=0.0002%, the balance is Fe and inevitable impurities, including steps of splashing slag and leaving slag operation, converter blowing control, deoxidation and alloying, refining treatment and continuous casting, through optimization of a refining process in a smelting process, the technology of rapid desulfurization and rapid alloying is solved, and a high-vacuum treatment method is adopted, so that the influence of harmful gases such as oxygen, nitrogen and hydrogen is effectively removed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel metallurgy, in particular to a high-purity nickel-based steel and a production method thereof. BACKGROUND

[0002] With the continuous development of China's economy, the technology of various industries has made great progress, especially the progress of steel metallurgy technology, which is particularly obvious in international industry competition advantage. According to the enterprise advantage, Nanjing Steel has developed the advantage varieties, among which the nickel-based steel has achieved great success in the development of the enterprise. Various kinds of nickel-based steel such as 0.5 nickel, 3 nickel, 5 nickel, 7 nickel and 9 nickel have been developed. The refining process of nickel-based steel is particularly important. With the continuous increase of production, how to improve the purity and production efficiency of the product in the production process to improve the market competitiveness is the main problem to be solved at present. SUMMARY

[0003] The present application overcomes the shortcomings of the prior art and provides a high-purity nickel-based steel and a production method thereof. Through optimization and in-depth research of the refining process in the smelting process, the technologies of rapid desulfurization and rapid alloying are solved. At the same time, the high vacuum treatment method is adopted to effectively eliminate the influence of harmful gases such as oxygen, nitrogen and hydrogen, so that the product quality is greatly improved. At the same time, the double LF smelting technology is adopted to effectively improve the smelting efficiency, greatly improve the continuous casting furnace times and improve the production efficiency and market competitiveness.

[0004] In a first aspect, the present application provides a high-purity nickel-based steel, the chemical composition and mass percentage of which are as follows: C: 0.030%-0.055%, Si: 0.10%-0.30%, Mn: 0.50%-0.80%, P≤0.005%, S≤0.002%, Cr:≤0.30%, Mo≤0.30%, Ni: 0.50%-1.0%, Cu:≤0.05, Al: 0.020%-0.050%, N≤0.0045%, H≤0.0002%, and the balance being Fe and unavoidable impurities.

[0005] In a second aspect, the present application provides a production method of the high-purity nickel-based steel in the first aspect, which comprises the following steps:

[0006] S1, slag splashing and slag retaining operation: after the tapping of the last furnace is completed, first perform the furnace shaking and slag pouring operation, the slag pouring angle is controlled within 112°, the amount of retained slag is controlled to 500-2000 kg, the furnace is lifted when the slag surface reaches the vicinity of the front surface, after the slag pouring is completed, the amount of splashed slag is 150-300 kg, the splashing time is within 150 s, 800-1200 kg of lime is added as a bottom pad before the end of splashing, which is included in the total amount of lime, and after the lance is lifted, the furnace is shaken by 40° to wait for the entry of scrap iron into the furnace;

[0007] S2, converter blowing control: first, large flow blowing, appropriate to reduce the oxygen intensity in the middle to help slag, the middle gun position is kept at 1700mm gun position, blowing to 6000Nm 3 When the oxygen supply is around, slowly lower the gun position to 1400mm and increase the oxygen supply intensity to start the early preparation of the end carbon, the target process temperature and carbon content is 1560±10℃ and w[C]%=0.10±0.05%, the target end temperature and carbon content is 1605±5℃ and w[C]%=0.02%;

[0008] S3, deoxidation and alloying: during tapping process, large mouth slagging is strictly prohibited to cause slag into ladle to increase phosphorus, alloy adding time can be delayed as far as possible, at the end of tapping, the molten steel is collected and the slide is closed, and slagging is strictly prohibited to cause back phosphorus;

[0009] S4, refining treatment: LF / RH process is used for refining treatment; aluminum wire and aluminum wire double deoxidizer are used for diffusion deoxidization in LF furnace, and double furnace smelting mode is used for treatment, the smelting time of molten steel and the removal period of inclusions are increased, and the RH furnace is treated by vacuum degassing, wherein the converter blowing control is 50-55 minutes, the LF furnace control is 50-55 minutes, and the RH furnace control is 65-68 minutes; because the RH vacuum time is long, the LF adopts double furnace smelting, which meets the process production requirements through alternating furnace production, and realizes the purpose of continuous casting of multiple furnaces;

[0010] S5, continuous casting.

[0011] The second aspect of the application is further limited by the technical scheme:

[0012] Further, the LF furnace smelting is batched according to the total oxygen content, and the final oxygen content is controlled to be less than 10ppm, and the final carbon content is controlled to be less than or equal to 0.05%.

[0013] Further, the LF furnace adopts aluminum wire and aluminum wire double deoxidizer for diffusion deoxidization, which specifically includes: 2 minutes of slagging at the beginning of tapping→ adding slagging material→ melting 2 minutes adding 30-50kg aluminum wire→ melting 2 minutes continuously adding 20-30kg aluminum wire→ 7-8 minutes sampling analysis of molten steel composition→ alloying according to element composition ratio→ simultaneously proportioning aluminum wire and aluminum wire→ continuing to melt for 3 minutes→ sampling analysis again→ alloying according to element composition ratio→ simultaneously proportioning aluminum wire and aluminum wire→ final alloy composition ratio is in place, after the molten steel reaches the treatment position, the ladle bottom blowing flow is adjusted to 400-600NL / min, 2-3min after power supply slagging, 2kg / ton of steel of lime and 0.2kg / ton of steel of aluminum wire are added, sampling analysis is carried out, and the electrode is raised.

[0014] Further, the converter blowing process adds lime and pre-melted refining slag to the ladle top slag, the pre-melted refining slag addition is 3-5 Kg per ton of steel, and the lime addition is 12-15 Kg per ton of steel.

[0015] Further, the chemical composition and percentage of the pre-melted refining slag are as follows:

[0016] CaO 45.0%~60.0%, Al203 22.0%~35.0%, SiO2≤5.0%, MgO≤6.0-8.0%, Fe2O3≤1.5%, H2O≤0.5%.

[0017] Further, in the LF refining process, the LF furnace is in full-flow micro-positive pressure to ensure that the furnace is full of gas, preventing external air from entering and ensuring a positive pressure state. The ladle flow is observed, and when the flow is ≥400 NL / min, bypass is prohibited to reduce the bare leakage of molten steel. At the same time, the slag layer thickness is observed according to the total amount of slag, and the buried arc effect is ensured by measuring the slag layer thickness. The slag layer thickness is required to be 30-50 cm to reduce the increase of nitrogen elements caused by arc ionization.

[0018] Further, in the RH refining process, the RH performs vacuum degassing treatment, the vacuum degree is not greater than 80 Pa, and the holding time is greater than 30 min. The gas content in the molten steel is reduced during the whole RH process, which takes 2-3.5 minutes from atmospheric pressure to 3.0 mbar. The molten steel circulation frequency is 30 times / min, and the molten steel circulation state is quickly reached. Through the circulation of waste gas, the degassing effect of the molten steel is achieved. After high vacuum, the hydrogen content of the molten steel is ≤1.5 ppm, and the nitrogen content of the molten steel is ≤40 ppm.

[0019] Further, after high vacuum, calcium treatment is carried out for inclusion removal treatment. The calcium wire feeding amount is adjusted according to the oxygen content in the molten steel, and the precise calcium-aluminum reaction ratio is achieved to convert inclusions into low-melting-point inclusions, so as to quickly float and remove them in the subsequent soft blowing process. The soft blowing time after calcium treatment is ≥25 min, and the soft blowing process prevents secondary oxidation of the molten steel. The low blowing flow is controlled at 30-80 NL / min.

[0020] The beneficial effects of the present application are:

[0021] (1) The present application adopts the splashing slag and slag leaving method, improves the first smelting hit rate of the converter, and the converter adopts different stage oxygen pressure control method, ensures that the carbon content of the converter tapping is not higher than 0.03%, the phosphorus content is not higher than 0.005%, stabilizes the production rhythm, and realizes the possibility of multi-ladle continuous casting;

[0022] (2) According to the smelting time of the converter, LF and RH manufacturing process, the present application adopts a double LF furnace manufacturing process, solves the problem of matching the converter, refining and continuous casting process, and realizes the problem of multi-ladle continuous casting.

[0023] (3) The present application solves the problem of phosphorus return in the converter by using process control technology, realizes fast decarburization and dephosphorization, avoids carbon increase in LF smelting, stabilizes the composition of finished products, avoids pollution of harmful gases in the process through process control of LF, effectively improves the purity of molten steel, and meets the performance requirements of products. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The flow chart of the production method of the high-purity nickel-based steel of the present application. DETAILED DESCRIPTION Example 1

[0025] The present embodiment provides a high-purity nickel-based steel, the chemical composition and mass percentage of which are as follows: C: 0.034%, Si: 0.17%, Mn: 0.65%, P: 0.003%, S: 0.001%, Cr: 0.02%, Mo: 0.03%, Ni: 8.86%, Cu: 0.02%, Al: 0.035%, N: 0.0031%, H: 0.0001%, and the balance is Fe and unavoidable impurities. The production method of the high-purity nickel-based steel is as follows, specifically including:

[0026] S1, splashing slag and leaving slag operation: after the tapping of the previous furnace is completed, first perform the shaking and slagging operation, the slagging angle is controlled at 110°, the amount of left slag is 800 kg, the furnace is lifted when the slag surface reaches the vicinity of the front surface, after the slagging is completed, the amount of splashing slag is about 220 kg, the splashing slag time is 130 s, 900 kg of lime is added as a bottom pad before the lance is lifted, and the total amount of lime is calculated, and then the furnace is shaken by 40° to wait for the entry of scrap iron and molten steel;

[0027] S2, converter blowing control: first, large flow blowing is started, the oxygen supply intensity is appropriately reduced in the middle period to help slag melting, the lance position is kept at 1700 mm in the middle period, and the blowing is performed to about 6000 Nm 3 around 3, the lance position is slowly lowered to 1400 mm and the oxygen supply intensity is increased to start the early preparation of the end carbon, the target process temperature and carbon content are 1568℃ and w[C]% is 0.15%, and the target end temperature and carbon content are 1605℃ and w[C]%=0.02;

[0028] S3, deoxidation and alloying: during the tapping process, large mouth slagging is strictly prohibited to prevent the entry of slag into the ladle and increase phosphorus, the alloying time can be delayed as much as possible, the molten steel is collected at the end of the tapping, and the slide is closed, and the slagging is strictly prohibited to prevent the return of phosphorus;

[0029] S4, refining treatment: LF / RH process is used for refining treatment; LF furnace uses aluminum wire and aluminum wire double deoxidizer for diffusion deoxidation, and double furnace smelting mode is used for treatment, which increases the molten steel smelting time and inclusion removal period, and RH furnace is treated by vacuum degassing, wherein the converter blowing control is 53 minutes, the LF furnace control is 54 minutes, and the RH furnace control is 67 minutes; because the RH vacuum time is longer, the LF adopts double furnace smelting, which meets the process production requirements through alternating furnace production, and realizes the purpose of continuous casting of multiple furnaces;

[0030] S5, continuous casting.

[0031] In this embodiment, the LF furnace smelting is batched according to the total oxygen content, and the final oxygen content is controlled to be 8 ppm, and the final carbon content is controlled to be below 0.04%.

[0032] In this embodiment, the LF furnace uses aluminum wire and aluminum wire double deoxidizer for diffusion deoxidation, which specifically includes: slagging 2 minutes after tapping starts → adding slagging material → melting 2 minutes adding 40 kg of aluminum wire → melting 2 minutes continuously adding 23 kg of aluminum wire → sampling and analyzing the composition of molten steel for 7 minutes → proportioning alloy according to element composition → simultaneously proportioning aluminum wire and aluminum wire → continuing to melt for 3 minutes → sampling and analyzing again → proportioning alloy according to element composition → simultaneously proportioning aluminum wire and aluminum wire → final alloy composition proportioning is in place, after the molten steel reaches the treatment station, the ladle bottom blowing flow is adjusted to 450 NL / min, 2 min after power supply slagging, 2 kg / ton of steel of lime and 0.2 kg / ton of steel of aluminum wire are added, sampling and analysis, and the electrode is raised.

[0033] In this embodiment, lime and premelted refining slag are added to the ladle top slag during the converter blowing and tapping process, the premelted refining slag addition is 4 Kg per ton of steel, and the lime addition is 13 Kg per ton of steel. The chemical composition and percentage of the premelted refining slag are as follows:

[0034] CaO 55.0%, Al203 29.0%, SiO2: 3.0%, MgO: 7.0%, Fe2O3: 1.3%, H2O: 0.2%.

[0035] In this embodiment, when the LF process is used for refining treatment, the LF furnace uses micro-positive pressure in the whole process to ensure that the furnace is full of gas, to prevent external air from entering, and to ensure the positive pressure state. The ladle flow is observed, and the buried arc effect is ensured by measuring the slag layer thickness, which is required to be 35 cm, to reduce the increase of nitrogen element caused by arc ionization.

[0036] In the present embodiment, the RH process is used for refining treatment. The RH performs vacuum degassing treatment, the vacuum degree is 60 Pa, the holding time is 33 min, the gas content in the molten steel is reduced during the whole RH process, it takes 3 min to reduce the gas content from atmospheric pressure to 3.0 mbar, the molten steel circulation frequency is 30 times / min, the molten steel circulation state is quickly reached, the degassing effect of the molten steel is achieved through the circulation of waste gas, the hydrogen content in the molten steel is 0.9 ppm after the high vacuum ends, the nitrogen content in the molten steel is 26 ppm after the high vacuum ends, calcium treatment is performed after the high vacuum ends, inclusion removal treatment is performed, the calcium wire feeding amount is adjusted according to the oxygen content in the molten steel, the calcium-aluminum reaction ratio is accurate, the inclusions are converted into low-melting-point inclusions, so as to quickly float and remove in the subsequent soft blowing process, the soft blowing time after calcium treatment is 26 min, the molten steel is prevented from being re-oxidized during the soft blowing process, and the low blowing flow is controlled to be 40 NL / min. Example 2

[0037] The present embodiment provides a high-purity nickel-based steel, the chemical composition and mass percentage of which are as follows: C: 0.043%, Si: 0.23%, Mn: 0.75%, P: 0.003%, S: 0.001%, Cr: 0.03%, Mo: 0.02%, Ni: 9.1%, Cu: 0.03%, Al: 0.041%, N: 0.0043%, H: 0.0001%, and the balance being Fe and unavoidable impurities. The following is a production method of the high-purity nickel-based steel, which specifically comprises:

[0038] S1, splashing and slagging operation: after the tapping of the previous furnace is completed, first perform the furnace shaking and slag dumping operation, the dumping angle is controlled to be 105°, the amount of slag left is controlled to be 1000 kg, the furnace is lifted when the slag surface reaches the vicinity of the front surface, after the slag dumping is completed, the splashing material is added in an amount of about 180 kg, the splashing time is 130 s, 1000 kg of lime is added as a bottom pad before the end of the splashing, and the total lime addition amount is calculated, and after the lance is lifted, the furnace is shaken by 40° to wait for the molten steel of scrap steel to be charged;

[0039] S2, converter blowing control: first, blow at a large flow rate, appropriately reduce the oxygen supply intensity in the middle period to help slag melting, the lance position is maintained at 1700 mm in the middle period, the blowing is performed to 6000 Nm 3 about 3.0 mbar, the molten steel circulation frequency is 30 times / min, the molten steel circulation state is quickly reached, the degassing effect of the molten steel is achieved through the circulation of waste gas, the hydrogen content in the molten steel is 0.9 ppm after the high vacuum ends, the nitrogen content in the molten steel is 26 ppm after the high vacuum ends, calcium treatment is performed after the high vacuum ends, inclusion removal treatment is performed, the calcium wire feeding amount is adjusted according to the oxygen content in the molten steel, the calcium-aluminum reaction ratio is accurate, the inclusions are converted into low-melting-point inclusions, so as to quickly float and remove in the subsequent soft blowing process, the soft blowing time after calcium treatment is 26 min, the molten steel is prevented from being re-oxidized during the soft blowing process, and the low blowing flow is controlled to be 40 NL / min.

[0040] S3, deoxidation and alloying: during the tapping process, large mouth slagging is strictly prohibited to prevent the slag from entering the ladle and increasing phosphorus, the alloy addition time can be delayed as much as possible, the molten steel is collected at the end of the tapping to close the slide, and slagging is strictly prohibited to cause back phosphorus;

[0041] S4, refining treatment: LF / RH process is used for refining treatment; LF furnace uses aluminum wire and aluminum wire double deoxidizer for diffusion deoxidation, and double furnace smelting mode is used for treatment, which increases the molten steel smelting time and inclusion removal period, and RH furnace is treated by vacuum degassing; the converter blowing is 54 minutes, the LF furnace is 53 minutes, and the RH furnace is 66 minutes; LF adopts double furnace smelting, which realizes the purpose of continuous casting of multiple furnaces;

[0042] S5, continuous casting.

[0043] In this embodiment, the LF furnace smelting is divided into batches according to the total oxygen content, and the final oxygen content is controlled to be 6ppm, and the final carbon content is 0.03%.

[0044] In this embodiment, the LF furnace uses aluminum wire and aluminum wire double deoxidizer for diffusion deoxidation, which specifically includes: slagging for 2 minutes after tapping, adding slagging material, melting for 2 minutes, adding 50kg of aluminum wire, melting for 2 minutes, continuously adding 22kg of aluminum wire, sampling and analyzing the composition of molten steel for 7.5 minutes, according to the element composition ratio of alloy, while the aluminum wire and aluminum wire are proportioned, continue to melt for 3 minutes, sample and analyze again, according to the element composition ratio of alloy, while the aluminum wire and aluminum wire are proportioned, and finally the alloy composition ratio is in place. After the molten steel reaches the treatment position, adjust the ladle bottom blowing flow to 500NL / min, supply power to slag for 2.6min, then add lime 2kg / ton of steel, aluminum wire 0.2kg / ton of steel, sample and analyze, and lower the electrode temperature.

[0045] In this embodiment, lime and premelted refining slag are added to the ladle top slag during the converter blowing and tapping process, the premelted refining slag addition is 5kg per ton of steel, and the lime addition is 13kg per ton of steel. The chemical composition and percentage of the premelted refining slag are as follows:

[0046] CaO 56%, Al20333%, SiO2:2.0%, MgO:6.8%, Fe2O3:1.0%, H2O:0.2%.

[0047] In this embodiment, when the LF process is used for refining treatment, the LF furnace is in full flow micro-positive pressure, which ensures that the furnace gas fills the furnace chamber, prevents external air from entering, and ensures the positive pressure state. Observe the ladle flow, measure the slag layer thickness to ensure the buried arc effect, the slag layer thickness is required to be 40cm, and the increase of nitrogen element caused by arc ionization is reduced.

[0048] In the present embodiment, when the RH process is used for refining treatment, the RH performs vacuum degassing treatment, the vacuum degree is 60 Pa, the holding time is 40 min, the gas content in the molten steel is reduced during the whole RH process, from atmospheric pressure to 3.0 mbar in 2.5 min, the molten steel circulation frequency is 30 times / min, the molten steel circulation state is rapidly reached, the degassing effect of the molten steel is completed through the circulation of exhaust gas, the hydrogen content in the molten steel is 1.1 ppm after the high vacuum ends, the nitrogen content in the molten steel is 20 ppm, calcium treatment is performed after the high vacuum ends, inclusion removal treatment is performed, the calcium wire feeding amount is adjusted according to the oxygen content in the molten steel, the calcium-aluminum reaction ratio is accurate, the inclusions are converted into low-melting-point inclusions, so as to be quickly removed in the subsequent soft blowing process, the soft blowing time after calcium treatment is 26 min, the molten steel is prevented from being re-oxidized during the soft blowing process, and the low blowing flow is controlled at 60 NL / min.

[0049] In addition to the above embodiments, the present application can also have other implementation manners. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present application.

Claims

1. A high-purity nickel-based steel, characterized in that, The chemical composition and mass percentage are as follows: C: 0.030%-0.055%, Si: 0.10%-0.30%, Mn: 0.50%-0.80%, P≤0.005%, S≤0.002%, Cr:≤0.30%, Mo≤0.30%, Ni: 0.50%-1.0%, Cu:≤0.05%, Al: 0.020%-0.050%, N≤0.0045%, H≤0.0002%, the balance being Fe and inevitable impurities; The production method of the high-purity nickel series steel comprises the following steps: S1, slag splashing and slag retaining operation: after the tapping of the previous furnace is completed, the furnace is first shaken and the slag is poured, the pouring angle is controlled within 112°, the amount of retained slag is controlled to 500-2000 kg, the furnace is lifted when the slag surface reaches the vicinity of the front surface, after the slag pouring is completed, the amount of splashed slag is 150-300 kg, the splashing time is within 150 s, 800-1200 kg of lime is added as a bottom pad before the lance is lifted, and the total amount of lime is calculated, and the furnace is shaken by 40° after the lance is lifted to wait for the molten iron to be poured into the furnace; S2, converter blowing control: first open blowing, large flow blowing, appropriate to reduce the oxygen supply intensity to help slag in the middle, the middle gun position is kept at 1700mm gun position, blowing to 6000Nm 3 the oxygen supply, slowly lower the gun position to 1400mm and increase the oxygen supply intensity to start the early preparation of the end of carbon, the target process temperature and carbon content is 1560±10℃ and w[C]%=0.10±0.05%, the target end temperature and carbon content is 1605±5℃ and w[C]%=0.02%; S3, deoxidation and alloying: during the tapping process, large mouth slagging is strictly prohibited to prevent the slag from entering the ladle and increasing phosphorus, the alloying time can be delayed as much as possible, the molten steel is collected at the end of the tapping process, and the slide is closed, and slagging is strictly prohibited to cause back phosphorus; S4, refining treatment: LF / RH process is used for refining treatment; the LF furnace uses aluminum wire and aluminum wire double deoxidizers for diffusion deoxidation, and a double-furnace smelting mode is used for treatment, the molten steel smelting time and inclusion removal period are increased, and the RH furnace is subjected to vacuum degassing treatment, wherein the converter blowing control is 50-55 minutes, the LF furnace control is 50-55 minutes, and the RH furnace control is 65-68 minutes; due to the long RH vacuum time, the LF adopts double-furnace smelting, which meets the process production requirements through alternating furnace production, and realizes the purpose of continuous casting of multiple furnaces; S5, continuous casting; The lime and pre-melted refining slag are added to the ladle top slag during the converter blowing and tapping process, the pre-melted refining slag is added at 3-5 kg per ton of steel, and the lime is added at 12-15 kg per ton of steel; The chemical composition and percentage of the pre-melted refining slag are as follows: CaO 45.0%-60.0%, Al203 22.0%-35.0%, SiO2≤5.0%, MgO≤6.0-8.0%, Fe2O3≤1.5%, H2O≤0.5%.

2. Steel for high purity nickel systems according to claim 1, characterized in that, The deoxidizer is added in batches according to the total oxygen content in the LF furnace smelting, the final oxygen content is controlled to be less than 10 ppm, and the final carbon content is controlled to be less than or equal to 0.05%.

3. Steel for high purity nickel systems according to claim 1, characterized in that, The LF furnace adopts aluminum wire and aluminum wire double deoxidizer for diffusion deoxidation, which specifically includes: slagging 2 minutes after tapping starts → adding slagging material → melting 2 minutes adding 30-50 kg of aluminum wire → melting 2 minutes continuously adding 20-30 kg of aluminum wire → sampling and analyzing the composition of molten steel for 7-8 minutes → proportioning alloy according to element composition → simultaneously proportioning aluminum wire and aluminum wire → continuing to melt for 3 minutes → sampling and analyzing again → proportioning alloy according to element composition → simultaneously proportioning aluminum wire and aluminum wire → final alloy composition proportioning is in place, after the molten steel reaches the treatment station, adjusting the ladle bottom blowing flow to 400-600 NL / min, supplying power for 2-3 min, then adding 2 kg / ton of steel of lime and 0.2 kg / ton of steel of aluminum wire, sampling and analyzing, and raising the temperature of the electrode.

4. Steel for high purity nickel systems according to claim 1, characterized in that, In the LF process for refining treatment, the LF furnace has full-flow micro-positive pressure, which ensures that the gas in the furnace fills the hearth, isolates the outside air from entering, and ensures the positive pressure state. The ladle flow is observed, and the flow is ≥400 NL / min to prevent the use of bypass and reduce the bare leakage of molten steel. At the same time, the thickness of the slag layer is observed according to the total amount of slag, and the buried arc effect is ensured by measuring the thickness of the slag layer. The thickness of the slag layer is required to be 30-50 cm to reduce the increase of nitrogen elements caused by arc ionization.

5. Steel for high purity nickel systems according to claim 1, characterized in that, In the RH process for refining treatment, RH performs vacuum degassing treatment, the vacuum degree is not greater than 80 Pa, and the holding time is greater than 30 min. The gas content in the molten steel is reduced during the whole RH process, which takes 2-3.5 minutes from atmospheric pressure to 3.0 mbar. The molten steel circulation frequency is 30 times / min, which quickly reaches the molten steel circulation state. Through the circulation of waste gas, the degassing effect of the molten steel is achieved. After high vacuum, the hydrogen content of the molten steel is ≤1.5 ppm, and the nitrogen content of the molten steel is ≤40 ppm.

6. Steel for high purity nickel series according to claim 5, characterized in that, After high vacuum, calcium treatment is carried out for inclusion removal treatment. The calcium wire feeding amount is adjusted according to the oxygen content in the molten steel, and the calcium-aluminum reaction ratio is accurate, so that the inclusions are converted into low-melting-point inclusions, which can quickly float and remove in the subsequent soft blowing process. The soft blowing time after calcium treatment is ≥25 min, and the soft blowing process prevents secondary oxidation of the molten steel. The low blowing flow is controlled at 30-80 NL / min.

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