CN117701980A - Manufacturing method of ultralow-nitrogen ferrite stainless steel ingot - Google Patents
Manufacturing method of ultralow-nitrogen ferrite stainless steel ingot Download PDFInfo
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 183
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 107
- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 98
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 59
- 239000010935 stainless steel Substances 0.000 title claims abstract description 24
- 229910000859 α-Fe Inorganic materials 0.000 title claims abstract description 15
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 128
- 239000010959 steel Substances 0.000 claims abstract description 128
- 238000005266 casting Methods 0.000 claims abstract description 64
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 56
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 55
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims abstract description 38
- 238000010079 rubber tapping Methods 0.000 claims abstract description 38
- 238000000034 method Methods 0.000 claims abstract description 26
- 238000009849 vacuum degassing Methods 0.000 claims abstract description 26
- 239000002893 slag Substances 0.000 claims abstract description 22
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 21
- 239000001301 oxygen Substances 0.000 claims abstract description 21
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 21
- 229910052786 argon Inorganic materials 0.000 claims abstract description 19
- 238000007670 refining Methods 0.000 claims abstract description 17
- 239000000126 substance Substances 0.000 claims abstract description 12
- 239000000203 mixture Substances 0.000 claims abstract description 11
- 238000005261 decarburization Methods 0.000 claims abstract description 10
- 238000002844 melting Methods 0.000 claims abstract description 9
- 230000008018 melting Effects 0.000 claims abstract description 9
- 230000001105 regulatory effect Effects 0.000 claims abstract description 6
- 230000001603 reducing effect Effects 0.000 claims abstract description 5
- 238000001816 cooling Methods 0.000 claims abstract description 4
- 238000009740 moulding (composite fabrication) Methods 0.000 claims abstract description 4
- 230000001590 oxidative effect Effects 0.000 claims abstract description 3
- 230000004907 flux Effects 0.000 claims description 2
- 238000003723 Smelting Methods 0.000 abstract description 12
- 238000010521 absorption reaction Methods 0.000 abstract description 10
- 230000001276 controlling effect Effects 0.000 abstract description 4
- 238000005260 corrosion Methods 0.000 description 10
- 230000007797 corrosion Effects 0.000 description 10
- 239000011651 chromium Substances 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 9
- 238000007664 blowing Methods 0.000 description 7
- 229910052804 chromium Inorganic materials 0.000 description 7
- 229910001026 inconel Inorganic materials 0.000 description 5
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 229910000963 austenitic stainless steel Inorganic materials 0.000 description 4
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 3
- 235000011941 Tilia x europaea Nutrition 0.000 description 3
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 239000010436 fluorite Substances 0.000 description 3
- 239000004571 lime Substances 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 230000001681 protective effect Effects 0.000 description 3
- 229910001566 austenite Inorganic materials 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 229910000604 Ferrochrome Inorganic materials 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- RGKMZNDDOBAZGW-UHFFFAOYSA-N aluminum calcium Chemical compound [Al].[Ca] RGKMZNDDOBAZGW-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000007405 data analysis Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000010891 electric arc Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- CSJDCSCTVDEHRN-UHFFFAOYSA-N methane;molecular oxygen Chemical compound C.O=O CSJDCSCTVDEHRN-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 239000011241 protective layer Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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Abstract
The application relates to the technical field of stainless steel manufacturing, and particularly discloses a manufacturing method of an ultralow-nitrogen ferrite stainless steel ingot. The manufacturing method of the ultra-low nitrogen ferrite stainless steel ingot comprises the following steps: firstly, regulating the mass fraction of carbon in a furnace burden which is proportioned according to the chemical composition requirements of the ultra-low nitrogen ferritic stainless steel ingot, then adding a slag former after melting, oxidizing and reducing, and tapping to obtain crude molten steel, wherein the mass fraction of carbon in the crude molten steel is 0.80-1.20%; drawing slag, receiving steel, vacuum oxygen decarburization, vacuum carbon deoxidation and vacuum degassing of the crude molten steel, and tapping to obtain refined molten steel; and adding covering slag into the refined molten steel, adopting argon protection for casting, and cooling and forming to obtain the ultralow-nitrogen ferrite stainless steel ingot. According to the method, the nitrogen absorption amount of molten steel is reduced and the nitrogen removal rate of the finally obtained ferritic stainless steel is improved by controlling the process steps and the process parameters of rough smelting, refining and casting.
Description
Technical Field
The application relates to the technical field of stainless steel manufacturing, in particular to a manufacturing method of an ultralow-nitrogen ferrite stainless steel ingot.
Background
The ferritic stainless steel is a type of stainless steel having a Cr content of 11% -30%, a body-centered cubic crystal structure, and a ferrite structure in a use state. Ferritic stainless steel is broadly classified into three types of 11% -15% Cr (low chromium), 16% -20% Cr (medium chromium), 21% -30% Cr (high chromium) according to the content of Cr therein.
Ferritic stainless steel is an important stainless steel class of five major classes of stainless steel, with yields and consumption inferior to inconel austenitic stainless steel. The ferrite stainless steel has good stainless property and comprehensive corrosion resistance, and also has good chloride stress corrosion resistance, pitting corrosion resistance and crevice corrosion resistance. Meanwhile, the strength of the ferrite stainless steel is high, and the heat conductivity coefficient is 130-150% of that of the austenite stainless steel. Ferritic stainless steel is a type of nickel-free or nickel-saving stainless steel that contains no nickel or only a small amount of nickel as compared to inconel austenitic stainless steel. Ferritic stainless steels are therefore of extremely high commercial value.
However, ferritic stainless steels have limited utility compared to inconel austenitic stainless steels. Since the atmosphere contains high nitrogen (78% of nitrogen), and the raw materials for steelmaking (ferrochrome and scrap) also contain nitrogen, nitrogen in ferritic stainless steel is difficult to remove. Although nitrogen is a strong austenite forming element in the inconel austenitic stainless steel, the toughness and corrosion resistance of the inconel austenitic stainless steel can be improved. However, nitrogen element forms and precipitates nitride in the ferritic stainless steel, and then adversely affects the properties of the ferritic stainless steel such as general corrosion resistance, intergranular corrosion resistance, stress corrosion resistance, pitting corrosion resistance, crevice corrosion resistance, and the like.
Disclosure of Invention
In order to improve the nitrogen removal rate in the ferritic stainless steel, the application provides a manufacturing method of an ultralow-nitrogen ferritic stainless steel ingot.
In a first aspect, the present application provides a method for manufacturing an ultralow-nitrogen ferritic stainless steel ingot, which adopts the following technical scheme:
a method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot, comprising the steps of:
s1, rough refining: firstly, regulating the mass fraction of carbon in a furnace burden which is prepared according to the chemical composition requirements of the ultra-low nitrogen ferritic stainless steel ingot to be more than or equal to 1.2%, then adding a slag former after melting, oxidizing and reducing, and tapping to obtain crude molten steel;
during tapping, the mass fraction of carbon in the crude molten steel is 0.80-1.20%;
s2 refining: drawing slag, receiving steel, vacuum oxygen decarburization, vacuum carbon deoxidation and vacuum degassing of the crude molten steel, and tapping to obtain refined molten steel;
when the vacuum carbon is deoxidized, the vacuum degree is 0.1-0.5 kPa;
when the vacuum degassing is carried out, the vacuum degree is 0.05 to 0.1kPa;
s3, casting: and adding covering slag into the refined molten steel, adopting argon protection for casting, and cooling and forming to obtain the ultralow-nitrogen ferrite stainless steel ingot.
By adopting the technical scheme, on the one hand, in S1 rough smelting, the resistance of the furnace burden is improved due to the fact that the mass fraction of carbon in the furnace burden is increased, so that the mass fraction of carbon in molten steel during tapping is in the range of 0.80-1.20%. Therefore, when the furnace burden is smelted in the electric furnace, more heat can be generated, the furnace burden melting time is shortened, the furnace burden can be quickly melted to obtain molten steel, and the dissolution of nitrogen in the molten steel is reduced.
On the other hand, in S2 refining, the principle that carbon and oxygen react preferentially under vacuum condition to generate gas is utilized, and the carbon and oxygen reaction can be activated by controlling the vacuum degree during vacuum carbon deoxidation and vacuum degassing, so that the carbon and residual oxygen in molten steel are promoted to react, and the decarburization deoxidation and denitrification effects of the molten steel are further improved.
Therefore, in the manufacturing method of the ultralow-nitrogen ferritic stainless steel ingot, the nitrogen absorption amount of molten steel is reduced and the nitrogen removal rate of the finally obtained ferritic stainless steel is improved by controlling the process steps and the process parameters of S1 rough smelting and S2 refining.
Preferably, in the S1 refining, the tapping temperature of the refined molten steel is 1630+/-10 ℃ and the tapping time is 4-6 min.
In the related technology, the tapping temperature of molten steel is 1650-1680 ℃, and the tapping time is 6-8 min. By adopting the technical scheme, the tapping temperature of molten steel is reduced, the tapping time of the molten steel is shortened, and the contact between the molten steel and air is reduced, so that the nitrogen absorption amount of the molten steel is reduced, and the nitrogen removal rate of the finally obtained ferritic stainless steel is improved.
Preferably, in the S2 refining, the oxygen flow is 450-750 m during vacuum oxygen blowing decarburization 3 And/h, the argon flow is 5-12 m 3 /h。
By adopting the technical scheme, the oxygen flow is increased, so that the heat loss of the molten steel can be reduced, the rapid reaction of carbon and oxygen in the molten steel is promoted, the oxidation of chromium in the molten steel is reduced, and the decarburization rate in the molten steel is further improved.
Preferably, in the S2 refining, the time for vacuum carbon deoxidation is 8 to 12min, and the time for vacuum degassing is 10 to 15min.
By adopting the technical scheme, the time of vacuum carbon deoxidation and vacuum degassing is prolonged, carbon-oxygen reaction can be promoted, a large number of carbon monoxide bubbles are generated to carry molten steel for denitrification, and the nitrogen content in the molten steel is reduced.
Preferably, in the S2 refiningWhen tapping, the temperature is 1640+/-10 ℃ and the argon flow is 0.4-0.6 m 3 /h。
The tapping temperature in the related art is 1660+/-10 ℃, and by adopting the technical scheme, the tapping temperature is properly reduced, argon with smaller flow is introduced, the molten steel can be slightly stirred, the exposure of the molten steel is reduced, the nitrogen absorption amount of the molten steel is reduced, and the nitrogen content in the finally obtained ferritic stainless steel is reduced.
Preferably, in the S3 casting, the casting temperature is 1540±5 ℃.
By adopting the technical scheme, the low-temperature casting is adopted, so that the gas absorption content in molten steel is reduced, and the nitrogen removal rate in the ferritic stainless steel is further improved.
Preferably, in the step S3 casting, the ingot body casting speed of the ultralow-nitrogen ferritic stainless steel ingot is 1.5-2.0 t/min, and the riser casting speed of the ultralow-nitrogen ferritic stainless steel ingot is 0.4-0.6 t/min.
By adopting the technical scheme, the low-temperature rapid casting is carried out according to the casting process conditions, so that the exposure time of molten steel can be effectively reduced, and the nitrogen absorption amount of the molten steel can be further reduced.
Preferably, in the S3 casting, the amount of the mold flux is 1.5-2.0 kg/t Steel and method for producing same 。
By adopting the technical scheme, the covering slag is added into the molten steel according to the dosage, so that a protective layer can be rapidly formed on the surface of the molten steel, the molten steel is isolated from air, the nitrogen absorption amount of the molten steel is reduced, and the nitrogen removal rate of the finally obtained ferritic stainless steel is improved.
In summary, the present application has the following beneficial effects:
1. in the manufacturing method of the ultralow-nitrogen ferritic stainless steel ingot, the carbon content of the furnace burden during rough smelting is increased, the reaction time during vacuum carbon deoxidation and vacuum degassing is controlled, the casting powder is added, and the low-temperature rapid casting is performed in an argon environment, so that the exposure time of molten steel in the air is shortened, the nitrogen absorption amount of the molten steel is reduced, and the nitrogen removal rate of the finally obtained ferritic stainless steel is improved;
2. according to the method, the steel tapping time during rough smelting is shortened, so that contact between molten steel and air can be effectively reduced, the nitrogen absorption amount of the molten steel is reduced, and the nitrogen removal rate of the finally obtained ferritic stainless steel is improved;
3. according to the method, through reducing the tapping temperature and the argon flow during refining, the exposure of molten steel in the air can be reduced, the nitrogen absorption of the molten steel is further reduced, and the nitrogen removal rate of the finally obtained ferritic stainless steel is improved.
Detailed Description
The present application is described in further detail below with reference to examples.
The materials and equipment used in the examples herein are commercially available except as specifically described below.
EAF arc furnace, capacity 15 tons;
VOD converter, capacity 15 tons.
Examples
Example 1
An ultralow-nitrogen ferritic stainless steel ingot consists of the following chemical components in percentage by mass:
the manufacturing method of the ultralow-nitrogen ferritic stainless steel ingot comprises the following steps:
s1, rough refining:
s11, proportioning and melting: adding molten steel which is proportioned according to the chemical composition requirements of the ultra-low nitrogen ferrite stainless steel ingot into an electric arc furnace, melting, and then adjusting the mass percentage content of carbon to be 1.2 percent to obtain molten steel after the proportioned melting.
S12, oxidation: blowing oxygen into molten steel after the batch is melted, and adding 25-30 kg/t Steel and method for producing same Is (in the embodiment of the application, 25 kg/t) Steel and method for producing same ，t Steel and method for producing same Meaning when the total weight of molten steel is smelted in the heat) is treated for 35min to obtain oxidized molten steel.
In the embodiment of the application, the slag former is formed by mixing lime and fluorite according to a weight ratio of 4:1.
S13, reduction: adding 1.5 to oxidized molten steel～2.0kg/t Steel and method for producing same Aluminum calcium deoxidizer (1.5 kg/t in this application) Steel and method for producing same ) Treating for 15-20 min (15 min in the embodiment of the application) to obtain the reduced molten steel.
S14, tapping: the reduced molten steel was tapped at a temperature of 1630.+ -. 10 ℃ (1635 ℃ in the present example) for 4 to 6min (5 min in the present example), and 15kg/t was added during tapping Steel and method for producing same -18kg/t Steel and method for producing same Is 15kg/t in the embodiment of the present application Steel and method for producing same ) Obtaining crude molten steel.
In the embodiment of the application, the slag former is formed by mixing lime and fluorite according to a weight ratio of 4:1.
The mass percentage of carbon in the crude molten steel is 1.15%.
S2 refining:
s21, slag pulling: pulling slag from the crude molten steel to obtain slag quantity less than 2kg/t Steel and method for producing same Is a molten steel of (2);
s22, steel: firstly, the slag quantity is smaller than 2kg/t Steel and method for producing same Adding the molten steel of (2) into a VOD converter, and adding 15kg/t Steel and method for producing same -18kg/t Steel and method for producing same Is 15kg/t in the embodiment of the present application Steel and method for producing same ) Stirring by blowing argon at the bottom of furnace at 1650-1750 ℃ (1650 ℃ in the embodiment of the application), wherein the flow rate of the argon is 3m 3 /h～6m 3 /h (5 m in the example of the application) 3 And/h) obtaining molten steel subjected to steel.
In the embodiment of the application, the slag former is formed by mixing lime and fluorite according to a weight ratio of 4.3:1.
S23, vacuum oxygen blowing decarburization: under the condition that the temperature of molten steel of the steel is 1550-1600 ℃ (1580 ℃ in the embodiment of the application), argon is firstly adopted to adjust the vacuum degree of the molten steel of the steel to be 40kPa, then an oxygen lance is adopted to blow oxygen into the vacuum degree of the molten steel of the steel to be 8-12 kPa (10 kPa in the embodiment of the application), pressure maintaining and decarburization are carried out for 0.6-1.0 h (1.0 h in the embodiment of the application), then oxygen and argon are continuously blown into the vacuum degree of the molten steel of the steel to be 2kPa, and oxygen blowing is stopped, so that the molten steel of vacuum oxygen blowing decarburization is obtained.
In the embodiment of the application, the oxygen flow is 450-750 m 3 /h (in the embodiment of the application, 750m 3 /h); argon flow is 5-12 m 3 /h (5 m in the example of the application) 3 H, and gradually increasing); the distance from the lance to the bath is 800-1000 mm (800 mm in the example of the present application).
S24, vacuum carbon deoxidization: vacuum blowing oxygen to decarbonize molten steel at vacuum degree of 0.25kPa and argon flow of 8-15m 3 /h (10 m in the embodiment of the application) 3 And/h) smelting for 12min at 1650-1750 ℃ (1650 ℃ in the embodiment of the application) to obtain the vacuum carbon deoxidized molten steel.
S25, vacuum degassing: according to the chemical composition requirements of ultra-low nitrogen ferrite stainless steel ingot, regulating chemical composition in molten steel subjected to vacuum carbon deoxidation, and then controlling the vacuum degree to be 0.06kPa and argon flow to be 8-15m 3 /h (8 m in the example of the application) 3 And/h) smelting for 15min at 1700-1750 ℃ (1730 ℃ in the embodiment of the application) to obtain vacuum degassed molten steel.
S26, tapping: according to the chemical composition requirements of ultra-low nitrogen ferrite stainless steel ingot, regulating chemical composition in vacuum degassed molten steel, then at 1643 ℃ and argon flow of 0.4-0.6 m 3 /h (0.5 m in the example of the application) 3 And/h) under the condition of slag remaining and tapping to obtain refined molten steel.
S3, casting: according to the chemical composition requirements of the ultralow-nitrogen ferritic stainless steel ingot, regulating chemical compositions in refined molten steel, adding covering slag into the refined molten steel, adopting argon protection casting, and cooling and forming to obtain the ultralow-nitrogen ferritic stainless steel ingot.
In the embodiment of the application, the casting temperature is 1540 ℃, the calm time is 4min, and the temperature is reduced by 5 ℃/min;
the casting speed of the ingot body is 1.6t/min, and the casting speed of the riser is 0.6t/min;
the protective slag is low-carbon protective slag, and the consumption of the protective slag is 1.5kg/t Steel and method for producing same ～2.0kg/t Steel and method for producing same (example 1.5 kg/t) Steel and method for producing same )。
Example 2
A method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot, which is different from example 1 in that the mass percentage of carbon in the crude molten steel is 0.8% when S14 is tapped; s24, when the vacuum carbon is deoxidized, the vacuum degree is 0.1kPa; in the vacuum degassing of S25, the vacuum degree was 0.05kPa.
Example 3
A method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot, which is different from example 1 in that the mass percentage of carbon in the crude molten steel is 1.2% when S14 is tapped; s24, when the vacuum carbon is deoxidized, the vacuum degree is 0.5kPa; in the vacuum degassing of S25, the vacuum degree was 0.1kPa.
Example 4
A method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot, which is different from example 1 in that the melting time is 10min when S24 is vacuum carbon deoxidized; and S25, vacuum degassing, wherein the vacuum degree is 0.06kPa, and the smelting time is 12min.
Example 5
A manufacturing method of an ultra-low nitrogen ferritic stainless steel ingot, which is different from example 1 in that the vacuum degree is 0.45kPa and the melting time is 8min when S24 is vacuum carbon deoxidized; and S25, vacuum degassing, wherein the vacuum degree is 0.08kPa, and the smelting time is 10min.
Example 6
A method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot, which is different from example 1 in that the mass percentage of carbon in the crude molten steel is 1.13% when S14 is tapped; s24, when the vacuum carbon is deoxidized, the vacuum degree is 0.26kPa; s25, vacuum degassing, wherein the vacuum degree is 0.063kPa; and S3, during casting, the casting temperature is 1545 ℃, the casting speed of the ingot body is 2.0t/min, and the casting speed of the riser is 0.5t/min.
Example 7
A method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot, which is different from example 1 in that the mass percentage of carbon in the crude molten steel is 1.09% when S14 is tapped; s24, when the vacuum carbon is deoxidized, the vacuum degree is 0.29kPa; s25, when vacuum degassing is carried out, the vacuum degree is 0.062kPa; and S3, during casting, the casting temperature is 1544 ℃, the casting speed of the ingot body is 1.5t/min, and the casting speed of the riser is 0.4t/min.
Example 8
A method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot, which is different from example 1 in that the mass percentage of carbon in the crude molten steel is 1.13% when S14 is tapped; s24, when the vacuum carbon is deoxidized, the vacuum degree is 0.26kPa; s25, vacuum degassing, wherein the vacuum degree is 0.063kPa; and S3, during casting, the casting temperature is 1560 ℃, the casting speed of the ingot body is 1.6t/min, and the casting speed of the riser is 0.5t/min.
Example 8
A method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot, which is different from example 1 in that the mass percentage of carbon in the crude molten steel is 1.09% when S14 is tapped; s24, when the vacuum carbon is deoxidized, the vacuum degree is 0.29kPa; s25, when vacuum degassing is carried out, the vacuum degree is 0.062kPa; and S3, during casting, the casting temperature is 1544 ℃, the casting speed of the ingot body is 1.2t/min, and the casting speed of the riser is 0.4t/min.
Comparative example
Comparative example 1
A manufacturing method of a ferritic stainless steel ingot, which is different from example 1 in that, when S14 is tapped, the mass percentage of carbon in the rough molten steel is 0.6%; s24, when the vacuum carbon is deoxidized, the vacuum degree is 0.21kPa; s25, vacuum degassing, wherein the vacuum degree is 0.0612kPa; and S3, during casting, the casting speed of the ingot body is 1.8t/min, and the casting speed of the riser is 0.5t/min.
Comparative example 2
A method for manufacturing a ferritic stainless steel ingot, which is different from example 1 in that the mass percentage of carbon in the rough molten steel is 1.12% when S14 is tapped; s24, when the vacuum carbon is deoxidized, the vacuum degree is 0.28kPa; s25, vacuum degassing, wherein the vacuum degree is 0.13kPa; and S3, during casting, the casting temperature is 1541 ℃, the casting speed of the ingot body is 1.7t/min, and the casting speed of the riser is 0.5t/min.
Comparative example 3
A manufacturing method of a ferritic stainless steel ingot, which is different from example 1 in that the mass percentage of carbon in the rough molten steel is 1.08% when S14 is tapped; s24, when the vacuum carbon is deoxidized, the vacuum degree is 0.7kPa; s25, vacuum degassing, wherein the vacuum degree is 0.058kPa; and S3, during casting, the casting temperature is 1538 ℃, the casting speed of the ingot body is 1.5t/min, and the casting speed of the riser is 0.5t/min.
Performance detection
In the manufacturing methods of the ultralow-nitrogen ferritic stainless steel ingots of examples 1 to 9 and the manufacturing methods of the ferritic stainless steel ingots of comparative examples 1 to 3, nitrogen content detection was performed on the S14 tapped molten steel, the S22 steel-receiving molten steel, the S25 vacuum-degassed molten steel, and the stainless steel ingots (the ultralow-nitrogen ferritic stainless steel ingots prepared in examples and the ferritic stainless steel ingots prepared in comparative examples), and the nitrogen removal rate of the stainless steel ingots relative to the S22 steel-receiving molten steel was calculated, with the calculation formula of nitrogen removal rate= (nitrogen content in the S22 steel-receiving molten steel—nitrogen content in the stainless steel ingot)/nitrogen content in the S22 steel-receiving molten steel ×100%, and the detection results are shown in the following table.
As can be seen from the data analysis of the above table, the nitrogen removal rates of examples 1 to 3 of the present application were as high as 78 to 79%. Meanwhile, the nitrogen removal rate of example 1 was increased by 26.6% compared to comparative example 1; the nitrogen removal rate of example 1 was increased by 21.5% relative to comparative example 2; the nitrogen removal rate was increased by 19.0% for example 1 compared to comparative example 3. Therefore, in the manufacturing method of the ultralow-nitrogen ferritic stainless steel ingot, when S14 is tapped, the mass percentage of carbon in the crude molten steel is 0.80-1.20%; s24, when the vacuum carbon is deoxidized, the vacuum degree is 0.1 to 0.5kPa; when S25 is vacuum deaerated, the vacuum degree is 0.05-0.1 kPa, and the nitrogen content in the ultralow-nitrogen ferrite stainless steel ingot can be reduced.
Further analysis of the above table shows that the nitrogen removal rates of examples 1, 4 and 5 of the present application were as high as 73 to 79%. However, the nitrogen removal rate was reduced by 1.3% for example 4 and 7.6% for example 5 compared to example 1. From the results, in the manufacturing method of the ultra-low nitrogen ferritic stainless steel ingot, although S24 is vacuum carbon deoxidized, the smelting time is 8-12 min; and S25, when vacuum degassing is carried out, the smelting time is 10-15 min, and the obtained ultralow-nitrogen ferritic stainless steel ingot has lower content. However, by reducing the vacuum degree at the time of S24 vacuum carbon deoxidation and S25 vacuum degassing and prolonging the smelting time of S24 vacuum carbon deoxidation and S25 vacuum degassing, the nitrogen removal rate in the ultra-low nitrogen ferritic stainless steel ingot is improved.
The nitrogen removal rates of examples 1, 6 and 7 are as high as 77-79%, and the nitrogen removal rates of examples 8 and 9 are as low as 68-71%. The nitrogen removal rates were higher for examples 1, 6, and 7 than for examples 8 and 9. Therefore, in the manufacturing method of the ultralow-nitrogen ferritic stainless steel ingot, when S3 is cast, the casting temperature is 1540+/-5 ℃, the casting speed of the ingot body is 1.5-2.0 t/min, the casting speed of the riser is 0.4-0.6 t/min, and the obtained ultralow-nitrogen ferritic stainless steel ingot has low content. Meanwhile, the nitrogen removal rates of examples 6 and 7 were relatively lower than that of example 1. Therefore, in the manufacturing method of the ultralow-nitrogen ferritic stainless steel ingot, the low-temperature rapid casting is adopted during S3 casting, so that the nitrogen removal rate of the ultralow-nitrogen ferritic stainless steel ingot can be improved.
The present application will be briefly described with reference to the preparation of an ultralow-nitrogen ferritic stainless steel ingot (trade mark 008Cr7 Mo) having the above chemical composition, but the application of the manufacturing method of the ultralow-nitrogen ferritic stainless steel ingot of the present application in the preparation of other ferritic stainless steel ingots is not affected.
In the manufacturing method of the ultralow-nitrogen ferritic stainless steel ingot, when S14 tapping is performed, the tapping temperature of the crude molten steel is 1630+/-10 ℃, and the tapping time is 4-6 min; when S26 is tapped, the temperature is 1640+/-10 ℃, and the obtained ultralow-nitrogen ferritic stainless steel ingot has lower nitrogen content. Meanwhile, compared with the control of the carbon content of S14 rough molten steel, the S24 vacuum carbon deoxidation, the vacuum degree of S25 vacuum degassing, the casting temperature and the casting speed of S3 casting, and the tapping temperature of S14 and S26 have less influence on the denitrification rate of the ultralow nitrogen ferritic stainless steel ingot. Further, since the temperature of the refined molten steel obtained in S14 needs to be raised when the refining in the next step S2 is performed, the temperature of the refined molten steel obtained in S26 needs to be lowered when the casting in S3 is performed. Therefore, if the tapping temperature of S14 is lowered and the tapping temperature of S26 is increased, the process cost of the present application for manufacturing the ultra-low nitrogen ferritic stainless steel ingot is increased. Therefore, in the embodiment of the present application, when tapping with S14 alone, the tapping temperature of the rough molten steel is 1635 ℃ and the tapping time is 5min; the steel tapping at S26 is briefly described with the temperature of 1643 ℃ as an example, but the application of other steel tapping temperatures in the application is not affected.
The present embodiment is merely illustrative of the present application and is not intended to be limiting, and those skilled in the art, after having read the present specification, may make modifications to the present embodiment without creative contribution as required, but is protected by patent laws within the scope of the claims of the present application.
Claims (8)
1. A method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot, comprising the steps of:
s1, rough refining: firstly, regulating the mass fraction of carbon in a furnace burden which is prepared according to the chemical composition requirements of the ultra-low nitrogen ferritic stainless steel ingot to be more than or equal to 1.2%, then adding a slag former after melting, oxidizing and reducing, and tapping to obtain crude molten steel;
during tapping, the mass fraction of carbon in the crude molten steel is 0.80-1.20%;
s2 refining: drawing slag, receiving steel, vacuum oxygen decarburization, vacuum carbon deoxidation and vacuum degassing of the crude molten steel, and tapping to obtain refined molten steel;
when the vacuum carbon is deoxidized, the vacuum degree is 0.1-0.5 kPa;
when the vacuum degassing is carried out, the vacuum degree is 0.05 to 0.1kPa;
s3, casting: and adding covering slag into the refined molten steel, adopting argon protection for casting, and cooling and forming to obtain the ultralow-nitrogen ferrite stainless steel ingot.
2. The method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot according to claim 1, wherein in the S1 roughing, the tapping temperature of the roughing molten steel is 1630±10 ℃ and the tapping time is 4 to 6min.
3. The method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot according to claim 1, wherein the oxygen flow rate is 450-750 m at the time of vacuum oxygen decarburization in the S2 refining 3 And/h, the argon flow is 5-12 m 3/ h。
4. The method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot according to claim 1, wherein in the S2 refining, the time for vacuum carbon deoxidation is 8 to 12min and the time for vacuum degassing is 10 to 15min.
5. The method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot according to claim 1, wherein the temperature is 1640±10 ℃ and the argon flow is 0.4 to 0.6m during tapping in the S2 refining 3 /h。
6. The method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot according to claim 1, wherein in the S3 casting, the casting temperature is 1540±5 ℃.
7. The method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot according to claim 1, wherein in the S3 casting, the ingot body casting speed of the ultra-low nitrogen ferritic stainless steel ingot is 1.5 to 2.0t/min, and the riser casting speed of the ultra-low nitrogen ferritic stainless steel ingot is 0.4 to 0.6t/min.
8. The method for manufacturing an ultra-low nitrogen ferritic stainless steel ingot according to claim 1, wherein the amount of mold flux used in the S3 casting is 1.5 to 2.0kg/t Steel and method for producing same 。
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