CN114774635A - Decarbonizing smelting method for RH vacuum furnace - Google Patents
Decarbonizing smelting method for RH vacuum furnace Download PDFInfo
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- CN114774635A CN114774635A CN202210387942.4A CN202210387942A CN114774635A CN 114774635 A CN114774635 A CN 114774635A CN 202210387942 A CN202210387942 A CN 202210387942A CN 114774635 A CN114774635 A CN 114774635A
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- 238000000034 method Methods 0.000 title claims abstract description 22
- 238000003723 Smelting Methods 0.000 title claims abstract description 18
- 239000010959 steel Substances 0.000 claims abstract description 112
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 111
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 77
- 238000005261 decarburization Methods 0.000 claims abstract description 69
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims abstract description 62
- 239000007789 gas Substances 0.000 claims abstract description 54
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 47
- 239000000956 alloy Substances 0.000 claims abstract description 47
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 34
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 34
- 229910052786 argon Inorganic materials 0.000 claims abstract description 31
- 239000001257 hydrogen Substances 0.000 claims abstract description 13
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 13
- 238000007664 blowing Methods 0.000 claims abstract description 12
- 238000004891 communication Methods 0.000 claims abstract description 12
- 230000000630 rising effect Effects 0.000 claims abstract description 7
- 238000005520 cutting process Methods 0.000 claims abstract description 3
- 230000001174 ascending effect Effects 0.000 claims description 13
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 10
- 239000001301 oxygen Substances 0.000 claims description 10
- 229910052760 oxygen Inorganic materials 0.000 claims description 10
- 239000011819 refractory material Substances 0.000 claims description 8
- 230000008569 process Effects 0.000 claims description 5
- 125000004435 hydrogen atom Chemical class [H]* 0.000 claims 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 abstract description 10
- 238000005275 alloying Methods 0.000 abstract description 8
- 230000009467 reduction Effects 0.000 abstract description 5
- 238000006243 chemical reaction Methods 0.000 description 12
- 238000000605 extraction Methods 0.000 description 11
- 230000006872 improvement Effects 0.000 description 9
- 238000005086 pumping Methods 0.000 description 9
- 238000004519 manufacturing process Methods 0.000 description 8
- CSJDCSCTVDEHRN-UHFFFAOYSA-N methane;molecular oxygen Chemical compound C.O=O CSJDCSCTVDEHRN-UHFFFAOYSA-N 0.000 description 6
- 239000000843 powder Substances 0.000 description 5
- 238000009489 vacuum treatment Methods 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 4
- AYJRCSIUFZENHW-UHFFFAOYSA-L barium carbonate Chemical compound [Ba+2].[O-]C([O-])=O AYJRCSIUFZENHW-UHFFFAOYSA-L 0.000 description 4
- 238000009749 continuous casting Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000010079 rubber tapping Methods 0.000 description 3
- 238000009628 steelmaking Methods 0.000 description 3
- 238000005303 weighing Methods 0.000 description 3
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- 238000007598 dipping method Methods 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000001095 magnesium carbonate Substances 0.000 description 2
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 2
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Substances [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 229910000976 Electrical steel Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 238000006356 dehydrogenation reaction Methods 0.000 description 1
- 238000009851 ferrous metallurgy Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/068—Decarburising
-
- 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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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
The invention provides a decarburization smelting method of an RH vacuum furnace, which comprises the steps of respectively cutting off the communication of a vacuum chamber with a vacuum alloy bin and a vacuum system pipeline before vacuumizing, sequentially opening a first-stage water circulating pump and a second-stage water circulating pump, adjusting working current according to the rising speed of a steel ladle, and pre-vacuumizing the vacuum system pipeline to ensure that the pressure of the vacuum system pipeline is reduced to 300-450mbar when the steel ladle rises to a treatment station; and then increasing the current of the second-stage water circulating pump, opening a vacuum main valve, blowing lifting gas into the vacuum chamber, opening a steam pump step by step according to the reduction of the pressure of the vacuum chamber, and gradually increasing the flow of the lifting gas. And when the RH decarburization is carried out for 7-9min, the lifting gas is changed into 60-70% argon and 30-40% hydrogen until the RH decarburization is finished, the lifting gas is switched into full argon after the decarburization is finished, the vacuum chamber is communicated with the vacuum alloy bin, the alloy in the vacuum alloy bin is added into molten steel for deoxidation and alloying, and then the treatment is carried out in a clean circulation manner, and the vacuum chamber is broken and steel is tapped. By using the method provided by the invention, the carbon content of the molten steel can be reduced to below 12ppm within 13 min.
Description
Technical Field
The invention relates to the technical field of ferrous metallurgy manufacturing, in particular to a decarburization smelting method of an RH vacuum furnace.
Background
The RH vacuum furnace has a series of functions of decarburization, degassing, deoxidation, inclusion removal, molten steel temperature regulation, chemical composition regulation and the like, has a series of advantages of short treatment period, high production capacity, good inclusion removal effect and the like, is widely applied to steelmaking production, and particularly shows remarkable superiority in the aspect of producing ultra-low carbon steel and high-quality pure steel.
With the market requirement that the carbon content in ultra-low carbon steel is lower and lower, the requirement on RH vacuum deep decarburization capability is higher and higher, for example, the carbon content of high-grade silicon steel and IF steel to finished products is within 15ppm or even within 10 ppm.
In order to obtain ultra-low carbon steel, it is common practice to blow a gas such as nitrogen, argon, carbon dioxide or carbon monoxide into molten steel or to add CaCO into molten steel during RH vacuum treatment3、BaCO3、MgCO3、Na2CO3Or Ca (OH)2One or more than one powder in the steel liquid can promote decarburization reaction and further reduce the carbon content in the steel liquid. However, blowing nitrogen, argon, carbon dioxide or carbon monoxide and other gases into molten steel can cause slow reduction of the vacuum degree of the vacuum chamber, and influence the decarburization rate; adding CaCO to molten steel3、BaCO3、MgCO3、Na2CO3Or Ca (OH)2One or more than one powder in the powder spraying device is easy to cause larger temperature drop of molten steel, and the powder spraying device is easy to be welded or blocked when directly contacting the molten steel, so that the decarburization efficiency is reduced, the temperature drop of the molten steel is larger, and the production cost is increased.
Disclosure of Invention
The invention aims to provide a decarburization smelting method of an RH vacuum furnace, which can obtain molten steel with ultra-low carbon content in a short time and solve the problem that the production cost is easily increased by blowing gas or adding powder which can be decomposed to generate gas into the molten steel in the prior art.
In order to achieve the above object, an embodiment of the present invention provides a decarburization smelting method in an RH vacuum furnace, including the steps of:
s1: respectively cutting off the communication between the vacuum chamber and the vacuum alloy bin and the vacuum system pipeline;
s2: opening a first-stage water circulating pump connected with a vacuum system pipeline, setting the working current of the first-stage water circulating pump to be 300-350A, starting to pre-vacuumize the vacuum system pipeline, and when the working current of the first-stage water circulating pump is set, starting to lift a steel ladle containing molten steel, and keeping the lifting speed of the steel ladle at 6-10 m/min; when the ladle reaches 40-60% of the ascending stroke of the ladle, the working current of the first-stage water circulating pump is adjusted to 380-350A, a second-stage water circulating pump connected with a vacuum system pipeline is started, and the working current of the second-stage water circulating pump is set to 300-350A; when the steel ladle reaches the processing station, the overall pressure of the vacuum system pipeline is 300-450 mbar;
s3: opening a vacuum main valve between a vacuum chamber and a vacuum system pipeline, adjusting the working current of the second-stage water circulation pump to be 380-420A, starting a first-stage steam pump connected with the vacuum system pipeline, blowing lifting gas to the vacuum chamber from a rising pipe in a dip pipe of the vacuum chamber, and setting the flow rate of the lifting gas to be 50-80 NL/min; when the pressure of the vacuum chamber is reduced to 100mbar, 20mbar and 5mbar, the second-stage steam pump, the third-stage steam pump and the fourth-stage steam pump which are connected with the vacuum system through pipelines are respectively started, after the second-stage steam pump is started, the lift gas flow is adjusted to be 150-200NL/min, and decarburization is finished after the first-stage water circulating pump is started for 10-13 min.
As a further improvement of one embodiment of the invention, after the first-stage water circulating pump is opened for 7-9min, the lifting gas is adjusted to be a mixed gas until the decarburization is finished, the mixed gas consists of 60-70% of argon and 30-40% of hydrogen, and the lifting gas is switched to be full argon after the decarburization is finished.
As a further improvement of an embodiment of the present invention, in step S2, when the ladle arrives at the processing station, the oxygen content of the molten steel is 0.050 to 0.075%, the carbon content is 0.02 to 0.05%, and the temperature is not less than 1610 ℃.
As a further improvement of an embodiment of the invention, the carbon content of the refractory materials in the steel ladle, the dip pipe of the RH vacuum furnace and the vacuum chamber is less than or equal to 0.05%.
As a further improvement of the embodiment of the invention, in step S2, when the operating current of the first-stage water circulation pump is set to 300-350A, the pumping rate is 15-30 mbar/S.
As a further improvement of the embodiment of the present invention, in step S2, after the operating current of the first stage water circulation pump is adjusted to 380-.
As a further improvement of the embodiment of the invention, in step S2, after the operating current of the second stage water circulation pump is adjusted to 380-420A, the total pumping rate is 70-80 mbar/S.
As a further improvement of an embodiment of the present invention, before the lift gas is adjusted to the mixed gas, the lift gas is argon gas.
As a further improvement of an embodiment of the invention, after the communication between the vacuum chamber and the vacuum alloy bin is cut off, the alloy is added into the vacuum alloy bin from a high-level bin; and opening a vent valve between the vacuum system pipelines to communicate the vacuum system pipelines.
As a further improvement of one embodiment of the invention, the carbon content of the molten steel is reduced to below 12ppm within 13min after the first-stage water circulating pump is turned on.
One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:
according to the embodiment of the invention, by controlling the air extraction rate and the steel ladle ascending speed during the vacuum extraction, the pressure of the vacuum system pipeline reaches the expected pressure when the steel ladle reaches the treatment station, the vacuum extraction time after the vacuum main valve is opened is shortened, the carbon-oxygen reaction starting time is advanced, the decarburization reaction time is shortened, the reduction of the molten steel temperature is reduced, and the steel-making production cost is reduced. Meanwhile, in the later stage of decarburization, the proportion of lifting gas is adjusted, the characteristic that the specific surface area of hydrogen bubbles is large is utilized, the decarburization reaction in the middle and later stages is accelerated, deep decarburization treatment is realized in a short time, and the molten steel can reach the molten steel with ultra-low carbon content in a short time.
Drawings
FIG. 1 is a schematic view showing the structure of an RH vacuum furnace in the embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific embodiments, but these embodiments do not limit the present invention, and the changes of reaction conditions, reactants or raw materials used by those skilled in the art according to these embodiments are included in the protection scope of the present invention.
Also, it should be understood that although the terms first level, second level, etc. may be used herein to describe various apparatus, these described objects should not be limited by these terms. These terms are only used to distinguish these descriptive objects from one another. For example, the first stage water circulation pump may be referred to as a second stage water circulation pump, and similarly the second stage water circulation pump may also be referred to as a first stage water circulation pump, without departing from the scope of the present application.
The embodiment of the invention provides a decarburization smelting method for an RH vacuum furnace, which comprises the following steps:
s1: the communication between the vacuum chamber and the vacuum alloy bin and the communication between the vacuum chamber and the vacuum system pipeline are respectively cut off.
S2: opening a first-stage water circulating pump connected with a vacuum system pipeline, setting the working current of the first-stage water circulating pump to be 300-350A, starting to pre-vacuumize the vacuum system pipeline, and when the working current of the first-stage water circulating pump is set, starting to lift a steel ladle containing molten steel, and keeping the lifting speed of the steel ladle at 6-10 m/min; when the ladle reaches 40-60% of the ascending stroke of the ladle, the working current of the first-stage water circulating pump is adjusted to 380-350A, a second-stage water circulating pump connected with a vacuum system pipeline is started, and the working current of the second-stage water circulating pump is set to 300-350A; when the ladle arrives at the treatment station, the overall pressure of the vacuum system pipeline is 300-450 mbar.
After the communication between the vacuum chamber and the vacuum system pipeline is cut off, a water circulating pump positioned on one side of the vacuum system pipeline is opened for pre-vacuumizing, and air in the vacuum system pipeline is discharged, so that the vacuumizing time during subsequent decarburization is shortened, and the carbon-oxygen reaction starting time is advanced; meanwhile, the air extraction rate is controlled by controlling the working current of the first-stage water circulating pump and the second-stage water circulating pump, so that the air extraction rate is matched with the rising speed of the steel ladle, when the steel ladle reaches a treatment station (when a dip pipe of the RH vacuum furnace is immersed in molten steel, the steel ladle reaches the treatment station), the overall pressure of a vacuum system pipeline reaches 300-450mbar, if the pressure is pre-extracted to be too low, when a vacuum main valve is opened, the pressure of a vacuum chamber at one side of the molten steel is high, the molten steel is greatly splashed, the chilled steel in the vacuum chamber is serious, and meanwhile, the production safety is influenced; if the pre-pumping pressure is too high, the effect of shortening the vacuum-pumping time and advancing the carbon-oxygen reaction starting time is not achieved.
S3: opening a vacuum main valve between a vacuum chamber and a vacuum system pipeline, adjusting the working current of the second-stage water circulating pump to be 380-; when the pressure of the vacuum chamber is reduced to 100mbar, 20mbar and 5mbar, the second-stage steam pump, the third-stage steam pump and the fourth-stage steam pump which are connected with the vacuum system through pipelines are respectively started, after the second-stage steam pump is started, the lift gas flow is adjusted to be 150-200NL/min, and decarburization is finished after the first-stage water circulating pump is started for 10-13 min.
After the vacuum main valve is opened, the gas in the vacuum chamber enters one side of the vacuum system pipeline, so that the pressure on one side of the vacuum system pipeline is increased, and therefore when the vacuum main valve is opened, the working current of the second-stage water circulating pump is immediately adjusted to be maximum, and the vacuum degree is quickly reduced by quickly pumping. A device for blowing lifting gas to the vacuum chamber is communicated in an ascending pipe of a dipping pipe of the vacuum chamber, after the dipping pipe is immersed in molten steel, the molten steel in a steel ladle is sucked into the vacuum chamber through the ascending pipe under the combined action of the lifting gas and the gas pressure difference, a vacuum main valve is opened to perform carbon-oxygen reaction decarburization in a vacuum environment, and then the molten steel flows back to the steel ladle through a descending pipe, and the aim of decarburization is fulfilled repeatedly in such a way. According to the reduction of the vacuum degree, the steam pump is gradually started, the whole decarburization period is matched with the water circulating pump, the steam pump is started and the change of gas is promoted, and the high decarburization rate is kept.
Further, after the first-stage water circulating pump is opened for 7-9min, the lifting gas is adjusted to be mixed gas until decarburization is finished, the mixed gas consists of 60-70% of argon and 30-40% of hydrogen, and the lifting gas is switched to be full argon after decarburization is finished.
In the middle and later stages of decarburization, the carbon content of molten steel is greatly reduced, hydrogen is added into the lifting gas, and carbon is promoted to perform carbon-oxygen reaction on the surface of bubbles by utilizing the characteristic of large specific surface area of hydrogen bubbles, so that decarburization is promoted. However, the hydrogen is added in the middle and later stages of decarburization, the addition amount is relatively small, the vacuum pressure is integrally low at the moment, the decarburization is promoted, meanwhile, a large amount of hydrogen elements cannot be remained, and the dehydrogenation of prolonging the deep vacuum time in the later stage is avoided.
Further, in step S2, when the steel ladle reaches the processing station, the oxygen content of the molten steel is 0.050-0.075%, the carbon content is 0.02-0.05%, and the temperature is more than or equal to 1610 ℃; when the steel ladle reaches the processing station, the lower limit value of the carbon content can reach 0.03 percent, namely the carbon content is 0.03 to 0.05 percent when the steel ladle reaches the processing station, and the aim of quick decarburization can be achieved; even when the steel ladle reaches the treatment station, the purpose of quick decarburization can be realized when the carbon content is 0.04-0.05%.
When the RH vacuum furnace is used for smelting ultra-low carbon steel, firstly, the RH incoming molten steel (when a dip pipe of the RH vacuum furnace is immersed in the molten steel) needs to have oxygen content higher than carbon content, so that frequent operations of oxygen blowing decarburization, oxygen blowing temperature rise and the like in the treatment process are avoided, and the decarburization speed is slowed down because the oxygen blowing process can slow down the vacuum pumping speed or raise the pressure of a vacuum chamber.
Furthermore, the carbon content of the refractory materials in the steel ladle, the dip pipe of the RH vacuum furnace and the vacuum chamber is less than or equal to 0.05 percent. During the decarburization process of the molten steel, the high-temperature molten steel can erode the refractory materials of a steel ladle, an immersion pipe, the inner wall of a vacuum chamber and the like which are contacted with the molten steel, so that the refractory materials of the steel ladle, the immersion pipe and the inner wall of the vacuum chamber are partially melted in the molten steel, therefore, the refractory materials need to contain very low carbon content, and the excessive carbon generated in the decarburization process of the molten steel is avoided.
Further, in step S2, when the working current of the first-stage water circulation pump is set to 300-350A, the air extraction rate is 15-30 mbar/S; in step S2, adjusting the working current of the first-stage water circulation pump to 380-; in step S2, after the working current of the second-stage water circulation pump is adjusted to 380-420A, the total pumping rate is 70-80 mbar/S. The embodiment of the invention controls the air extraction rate by controlling the current of the water circulating pump, so that the air extraction rate is matched with the ascending rate of the steel ladle, and the aim that the pipeline pressure of a vacuum system reaches the expected pressure when the steel ladle reaches a treatment station is fulfilled.
Further, before the lifting gas is adjusted to be the mixed gas, the lifting gas is full argon, and the inert gas is added, so that the environment in the vacuum chamber is more stable, and redundant reaction cannot occur.
Further, after the communication between the vacuum chamber and the vacuum alloy bin is cut off, adding the alloy into the vacuum alloy bin from a high-level bin; and opening a vent valve between the vacuum system pipelines to communicate the vacuum system pipelines. The high-level storage bin is used for storing alloy required in deoxidation alloying, the alloy is placed into the vacuum alloy bin for standby before vacuum pumping, a valve between the vacuum chamber and the vacuum alloy bin is quickly opened after decarburization is completed to enable the vacuum chamber and the vacuum alloy bin to be communicated, the alloy in the vacuum alloy bin is added into molten steel for deoxidation alloying, and then clean circulation treatment is carried out to break the space and tap steel.
Furthermore, the carbon content of the molten steel is reduced to be below 12ppm within 13min after the first-stage water circulating pump is started, and efficient decarburization is realized.
According to the embodiment of the invention, by controlling the air extraction rate and the steel ladle ascending speed during the vacuum extraction, the pressure of the vacuum system pipeline reaches the expected pressure when the steel ladle reaches the treatment station, the vacuum extraction time after the vacuum main valve is opened is shortened, the carbon-oxygen reaction starting time is advanced, the decarburization reaction time is shortened, the reduction of the molten steel temperature is reduced, and the steel-making production cost is reduced. Meanwhile, in the later stage of decarburization, the proportion of lifting gas is adjusted, the characteristic that the specific surface area of hydrogen bubbles is large is utilized, the decarburization reaction in the middle and later stages is accelerated, deep decarburization treatment is realized in a short time, and the molten steel can reach the molten steel with ultra-low carbon content in a short time.
The technical solution of the present application is further described below with reference to some specific examples.
Example 1
S1: before vacuumizing, closing a connecting pipeline between a vacuum chamber and a vacuum alloy bin, weighing the alloy to be added when the steel grade to be smelted is subjected to deoxidation alloying, and adding the alloy into the vacuum alloy bin from a high-level bin; opening a vent valve between vacuum system pipelines at one side of a vacuum main valve, which is far away from the vacuum chamber; and after the RH molten steel ladle is finished, closing a vacuum main valve of the RH vacuum furnace to cut off the communication between the vacuum chamber and a vacuum system pipeline.
S2: opening a first-stage water circulating pump to start vacuumizing, setting the working current of the first-stage water circulating pump to be 300A, keeping the air suction speed at 15mbar/s, and when the working current of the first-stage water circulating pump is set, starting to rise a steel ladle filled with molten steel, and keeping the rising speed of the steel ladle at 6 m/min; when the steel ladle rises to 60% of the lifting stroke of the steel ladle, the working current of the first-stage water circulating pump is adjusted to 380A, the second-stage water circulating pump is started, the working current is set to 300A, and the air suction speed is kept at 40 mbar/s; when the steel ladle rises to a treatment station, the oxygen content is 0.05 percent, the carbon content is 0.02 percent, the molten steel temperature is 1610 ℃, and the integral pressure of a vacuum system pipeline is 450 mbar.
S3: opening a vacuum main valve, adjusting the working current of a second-stage water circulating pump to 380A, starting a first-stage steam pump, and blowing argon into the vacuum chamber from the ascending pipe, wherein the flow of the argon is set to be 80 NL/min; when the pressure of the vacuum chamber is reduced to 100mbar, 20mbar and 5mbar, the second-stage steam pump, the third-stage steam pump and the fourth-stage steam pump are respectively started, and after the second-stage steam pump is started, the argon flow is adjusted to 150 NL/min; after the first-stage water circulating pump is opened for 9min, adjusting argon serving as lifting gas into mixed gas consisting of 60% of argon and 40% of hydrogen until RH decarburization is finished, and adjusting the mixed gas into full argon after decarburization is finished; and after vacuumizing for 13min, finishing decarburization, opening a valve between the vacuum chamber and the vacuum alloy bin to enable the vacuum chamber and the vacuum alloy bin to be communicated, adding molten steel into the alloy in the vacuum alloy bin for deoxidation alloying, then carrying out clean circulation treatment and blank breaking tapping, and transporting to continuous casting and pouring.
The refractory carbon content in the heat ladle, the RH dip pipe and the vacuum chamber is 0.05 percent; the carbon content of the molten steel is reduced to 5ppm within 13min of RH vacuum treatment.
Example 2
S1: before vacuumizing, closing a connecting pipeline between a vacuum chamber and a vacuum alloy bin, weighing the alloy to be added when the steel grade to be smelted is deoxidized and alloyed, and adding the alloy into the vacuum alloy bin from a high-level bin; opening a vent valve between vacuum system pipelines on one side of a vacuum main valve, which is far away from the vacuum chamber; and after the RH molten steel ladle is finished, closing a vacuum main valve of the RH vacuum furnace to cut off the communication between the vacuum chamber and a vacuum system pipeline.
S2: opening a first-stage water circulating pump to start vacuumizing, setting the working current of the first-stage water circulating pump to be 350A, keeping the air exhaust speed at 30mbar/s, and when the working current of the first-stage water circulating pump is set, starting to ascend a steel ladle filled with molten steel, and keeping the ascending speed of the steel ladle at 10 m/min; when the steel ladle rises to 40% of the rising stroke of the steel ladle, the working current of the first-stage water circulating pump is adjusted to 420A, the second-stage water circulating pump is started, the working current is set to 350A, and the air suction speed is kept at 60 mbar/s; when the steel ladle rises to a treatment station, the oxygen content is 0.075 percent, the carbon content is 0.05 percent, the molten steel temperature is 1615 ℃, and the integral pressure of a vacuum system pipeline is 300 mbar.
S3: opening a vacuum main valve, adjusting the working current of a second-stage water circulating pump to 420A, starting a first-stage steam pump, and blowing argon into the vacuum chamber from the ascending pipe, wherein the flow of the argon is set to be 50 NL/min; when the pressure of the vacuum chamber is reduced to 100mbar, 20mbar and 5mbar, respectively starting a second-stage steam pump, a third-stage steam pump and a fourth-stage steam pump, and after the second-stage steam pump is started, adjusting the argon flow to 200 NL/min; after the first-stage water circulating pump is opened for 7min, adjusting argon serving as lifting gas into mixed gas consisting of 70% of argon and 30% of hydrogen until RH decarburization is finished, and adjusting the mixed gas into full argon after decarburization is finished; and after vacuumizing for 10min, finishing decarburization, opening a valve between the vacuum chamber and the vacuum alloy bin to enable the vacuum chamber and the vacuum alloy bin to be communicated, adding molten steel into the alloy in the vacuum alloy bin for deoxidation alloying, then carrying out clean circulation treatment and blank breaking tapping, and transporting to continuous casting and pouring.
The refractory material carbon content in the heat ladle, the RH dip pipe and the vacuum chamber is 0.05 percent; the carbon content of the molten steel is reduced to 12ppm within 10min of RH vacuum treatment.
Example 3
S1: before vacuumizing, closing a connecting pipeline between a vacuum chamber and a vacuum alloy bin, weighing the alloy to be added when the steel grade to be smelted is subjected to deoxidation alloying, and adding the alloy into the vacuum alloy bin from a high-level bin; opening a vent valve between vacuum system pipelines at one side of a vacuum main valve, which is far away from the vacuum chamber; and after the RH molten steel ladle is finished, closing a vacuum main valve of the RH vacuum furnace to cut off the communication between the vacuum chamber and a vacuum system pipeline.
S2: opening a first-stage water circulating pump to start vacuumizing, setting the working current of the first-stage water circulating pump to be 320A, keeping the air exhaust speed at 24mbar/s, and when the working current of the first-stage water circulating pump is set, starting to ascend a steel ladle filled with molten steel, and keeping the ascending speed of the steel ladle at 8 m/min; when the steel ladle rises to 50% of the lifting stroke of the steel ladle, the working current of the first-stage water circulating pump is adjusted to 400A, the second-stage water circulating pump is started, the working current is set to 320A, and the air suction speed is kept at 50 mbar/s; when the steel ladle rises to a treatment station, the oxygen content is 0.065%, the carbon content is 0.032%, the molten steel temperature is 1621 ℃, and the integral pressure of the vacuum system pipeline is 380 mbar.
S3: opening a vacuum main valve, adjusting the working current of a second-stage water circulating pump to 400A, starting a first-stage steam pump, and blowing argon into the vacuum chamber from the ascending tube, wherein the flow of the argon is set to be 70 NL/min; when the pressure of the vacuum chamber is reduced to 100mbar, 20mbar and 5mbar, the second-stage steam pump, the third-stage steam pump and the fourth-stage steam pump are respectively started, and after the second-stage steam pump is started, the argon flow is adjusted to 180 NL/min; opening the first-stage water circulating pump for 8min, adjusting argon serving as lifting gas into mixed gas consisting of 65% of argon and 35% of hydrogen until RH decarburization is finished, and adjusting the mixed gas into full argon after decarburization is finished; and after vacuumizing for 12min, finishing decarburization, opening a valve between the vacuum chamber and the vacuum alloy bin to enable the vacuum chamber and the vacuum alloy bin to be communicated, adding molten steel into the alloy in the vacuum alloy bin for deoxidation alloying, then carrying out clean circulation treatment and blank breaking tapping, and transporting to continuous casting and pouring.
The refractory material carbon content in the heat ladle, the RH dip pipe and the vacuum chamber is 0.05 percent; the carbon content of the molten steel is removed to 8ppm within 12min of RH vacuum treatment.
The above embodiment can be seen that the current of the first-stage water circulation pump and the second-stage water circulation pump is controlled to achieve the control of the pumping rate, so that the overall pressure of the vacuum main valve far away from one side of the vacuum chamber is 450mbar in cooperation with the rising speed of the ladle when the ladle reaches the treatment station, the pressure does not cause molten steel splashing, the decarburization reaction can be advanced to shorten the decarburization time, and the carbon content can be reduced to be below 12ppm within 13min of RH vacuum treatment.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should it be exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (10)
1. The decarburization smelting method of the RH vacuum furnace is characterized by comprising the following steps:
s1: respectively cutting off the communication between the vacuum chamber and the vacuum alloy bin and the vacuum system pipeline;
s2: opening a first-stage water circulation pump connected with a vacuum system pipeline, setting the working current of the first-stage water circulation pump to be 300-350A, starting to pre-vacuumize the vacuum system pipeline, and when the working current of the first-stage water circulation pump is set, starting to lift a steel ladle containing molten steel, and keeping the lifting speed of the steel ladle to be 6-10 m/min; when the ladle reaches 40-60% of the ascending stroke of the ladle, the working current of the first-stage water circulating pump is adjusted to be 380-350A, a second-stage water circulating pump connected with a vacuum system pipeline is started, and the working current of the second-stage water circulating pump is set to be 300-350A; when the steel ladle reaches the processing station, the overall pressure of the vacuum system pipeline is 300-450 mbar;
s3: opening a vacuum main valve between a vacuum chamber and a vacuum system pipeline, adjusting the working current of the second-stage water circulation pump to be 380-420A, starting a first-stage steam pump connected with the vacuum system pipeline, blowing lifting gas to the vacuum chamber from a rising pipe in a dip pipe of the vacuum chamber, and setting the flow rate of the lifting gas to be 50-80 NL/min; when the pressure of the vacuum chamber is reduced to 100mbar, 20mbar and 5mbar, the second-stage steam pump, the third-stage steam pump and the fourth-stage steam pump which are connected with the vacuum system pipeline are respectively started, after the second-stage steam pump is started, the flow rate of the lifting gas is adjusted to be 150-200NL/min, and the decarburization is finished after the first-stage water circulating pump is started for 10-13 min.
2. The decarburization smelting method for the RH vacuum furnace according to claim 1, wherein after the first-stage water circulation pump is turned on for 7-9min, the lift gas is adjusted to be a mixed gas until decarburization is finished, the mixed gas is composed of 60-70% argon and 30-40% hydrogen, and the lift gas is switched to be full argon after decarburization is finished.
3. The decarburization smelting method for an RH vacuum furnace according to claim 1, wherein in step S2, when the ladle reaches the treatment station, the oxygen content of the molten steel is 0.050-0.075%, the carbon content is 0.02-0.05%, and the temperature is not less than 1610 ℃.
4. The decarburization smelting method of an RH vacuum furnace as claimed in claim 1, wherein the carbon content of the refractory materials in the ladle, the dip pipe of the RH vacuum furnace and the vacuum chamber is less than or equal to 0.05%.
5. The decarburization smelting method for an RH vacuum furnace as recited in claim 1, wherein in the step S2, when the operating current of the primary water circulation pump is set to 300-350A, the evacuation rate is 15-30 mbar/S.
6. The decarburization smelting method for an RH vacuum furnace as recited in claim 5, wherein in the step S2, the working current of the first stage water circulation pump is adjusted to 380-420A, and after the second stage water circulation pump is turned on and the working current of the second stage water circulation pump is set to 300-350A, the total evacuation rate is 40-60 mbar/S.
7. The decarburization smelting method for an RH vacuum furnace as claimed in claim 6, wherein in step S2, after the operating current of the second stage water circulation pump is adjusted to 380-420A, the total evacuation rate is 70-80 mbar/S.
8. The decarburization smelting method for an RH vacuum furnace according to claim 1, wherein after the communication between the vacuum chamber and the vacuum alloy bin is cut off, the alloy is added into the vacuum alloy bin from a high-level bin; and opening a vent valve between the vacuum system pipelines to communicate the vacuum system pipelines.
9. The decarburization smelting process for an RH vacuum furnace according to claim 2, wherein the lift gas is argon before the mixed gas is adjusted to the mixed gas.
10. The RH vacuum furnace decarburization smelting method according to any one of claims 1 to 9, wherein the carbon content of molten steel is reduced to 12ppm or less within 13min after the first-stage water circulation pump is turned on.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH0610029A (en) * | 1992-06-25 | 1994-01-18 | Nkk Corp | Production of ultralow carbon steel |
| CN102816894A (en) * | 2012-08-22 | 2012-12-12 | 河北钢铁股份有限公司邯郸分公司 | Control method for enhancing RH vacuum circulation decarburization rate |
| CN109576447A (en) * | 2018-12-29 | 2019-04-05 | 钢铁研究总院 | A kind of RH purifier and method promoting the decarburization of molten steel depth |
| CN109628705A (en) * | 2019-02-26 | 2019-04-16 | 太原科技大学 | A kind of RH method of refining of low carbon stainless steel |
| CN112609044A (en) * | 2020-12-11 | 2021-04-06 | 北京首钢股份有限公司 | RH pre-vacuumizing device and method |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0610029A (en) * | 1992-06-25 | 1994-01-18 | Nkk Corp | Production of ultralow carbon steel |
| CN102816894A (en) * | 2012-08-22 | 2012-12-12 | 河北钢铁股份有限公司邯郸分公司 | Control method for enhancing RH vacuum circulation decarburization rate |
| CN109576447A (en) * | 2018-12-29 | 2019-04-05 | 钢铁研究总院 | A kind of RH purifier and method promoting the decarburization of molten steel depth |
| CN109628705A (en) * | 2019-02-26 | 2019-04-16 | 太原科技大学 | A kind of RH method of refining of low carbon stainless steel |
| CN112609044A (en) * | 2020-12-11 | 2021-04-06 | 北京首钢股份有限公司 | RH pre-vacuumizing device and method |
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