CN110976787B - Tundish protection casting method for ultra-low carbon steel - Google Patents
Tundish protection casting method for ultra-low carbon steel Download PDFInfo
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- CN110976787B CN110976787B CN201911298444.7A CN201911298444A CN110976787B CN 110976787 B CN110976787 B CN 110976787B CN 201911298444 A CN201911298444 A CN 201911298444A CN 110976787 B CN110976787 B CN 110976787B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
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Abstract
The invention discloses a tundish protection casting method of ultra-low carbon steel, which comprises the following steps: s1, casting ultra-low carbon steel, wherein during casting, a mixed gas of carbon dioxide and argon is blown out by a tundish cover blowing device; s2, when the pouring is started for 0-5min, the gas flow of the carbon dioxide gas is 1500-; s3, casting time is 5min, and then casting is finished, the volume fraction of carbon dioxide gas is 5% -15%, and the gas flow is 200-1500 Nl/min. According to the method, 5% -30% of carbon dioxide gas is mixed into argon serving as protective gas of a tundish cover, the carbon dioxide gas enters molten steel to react, and carbon monoxide bubbles float upwards in the molten steel and are discharged. The carbon dioxide gas can consume carbon in steel under the condition of casting temperature, and the generated carbon monoxide gas has extremely low concentration, is fully burnt when being released from a tundish and does not cause safety problem.
Description
Technical Field
The invention relates to the technical field of tundish protection casting of ultra-low carbon steel, in particular to a tundish protection casting method of ultra-low carbon steel.
Background
When the tundish is baked and before casting, a large amount of air enters the tundish, and molten steel is cast under the condition, so that the molten steel is oxidized. Therefore, the tundish cover argon blowing device is additionally arranged. Opening an argon blowing pipeline after baking of the tundish is finished, increasing argon pressure, fully purging the tundish by a high-speed argon blowing method, completely discharging all air in the tundish to form an argon protective layer in the tundish, fully covering the tundish with a covering agent until the tonnage of the tundish rises to a certain height, and then reducing gas flow to ensure that high-temperature molten steel is in an argon micro-positive pressure state in the casting process, so that the molten steel is prevented from directly contacting with air, secondary oxidation and N increase of molten steel in primary casting are reduced, and the production quality of steel products is improved.
In the process of casting the ultra-low carbon steel, in addition to preventing the secondary oxidation of the molten steel, the problem to be solved is the recarburization of the molten steel. Because carbon plays a skeleton supporting role in the refractory material, a water gap, a stopper rod, a covering agent and the like in the tundish have certain carbon content which is difficult to avoid, and the carbon content in the refractory material corresponding to the positions of a stopper rod slag line, a water gap slag line and the like is as high as about 30 percent at most. When the ultra-low carbon molten steel contacts with the ultra-low carbon molten steel, mass transfer from refractory and covering agent to the molten steel can occur to carbon element, and for the ultra-low carbon steel, after casting for 10-30min, the carbon content is different from a few to more than ten ppm, and in order to ensure that the components of the molten steel reach the standard, the carbon content in the molten steel before casting needs to be considered, so the requirement on the carbon content in the molten steel before casting is stricter, and the cost and difficulty of smelting in the early stage are increased.
Disclosure of Invention
In view of the above problems, the present invention has been made to provide a method of tundish protection casting of ultra low carbon steel which overcomes or at least partially solves the above problems.
The embodiment of the invention provides a tundish protection casting method of ultra-low carbon steel, which comprises the following steps:
s1, casting ultra-low carbon steel, wherein during casting, a mixed gas of carbon dioxide and argon is blown out by a tundish cover blowing device;
s2, when the pouring is started for 0-5min, the gas flow of the carbon dioxide gas is 1500-2500NL/min in the mixed gas of the carbon dioxide and the argon blown out by the tundish cover blowing device;
s3, casting time is 5min, and then casting is finished, the volume fraction of carbon dioxide gas is 5% -15%, and the gas flow is 200-1500 NL/min.
Preferably, in S1, the ultra-low carbon steel has a steel grade C element mass fraction of 0 to 0.01%.
Preferably, in S2, the flow rate of the mixed gas of the carbon dioxide and the argon is changed in a step mode along with the casting tonnage in the tundish, and the flow rate is 200-.
Preferably, the gas flow rate increase caused by two units of CO gas generated per unit volume of carbon dioxide gas is also considered on the basis of the flow rate of the total argon gas shroud shield gas.
Preferably, the volume fraction of carbon dioxide in the protective gas of the tundish cover is 10-30% within 5min before casting in flood S2.
Preferably, at the casting temperature T in S1, according to the formula:
C+CO2(g)→2CO(g)，ΔG＝144700-1295T
wherein C is the carbon content in the ultra-low carbon steel, CO2Δ G is constant-2.18X 10 for the mass of carbon dioxide6；
When the casting temperature T is 1600-1635 ℃, the reaction delta G is-2.18 multiplied by 106And the reaction can proceed to the right continuously with the exclusion of product CO.
Preferably, the CO gas is detected once by a CO detector at intervals of 5-10 minutes, and the rising trend of the CO gas concentration is judged by recording and comparing.
One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:
according to the method for casting the ultra-low carbon steel in the tundish protection manner, the carbon dioxide gas is mixed into argon gas serving as the protective gas of the tundish cover in a proportion of 5-30%, the carbon dioxide gas enters molten steel to react, and carbon monoxide bubbles float upwards and are discharged from the molten steel. The carbon dioxide gas can consume carbon in steel under the condition of casting temperature, and the generated carbon monoxide gas has extremely low concentration, is fully burnt when being released from a tundish and does not cause safety problem. The method can easily obtain a carbon dioxide gas source in a steel mill, realizes the mixing of carbon dioxide and argon, reduces the smelting difficulty in the early stage of casting, does not generate new increased cost, and is a convenient and cheap method for inhibiting the recarburization of the ultra-low carbon molten steel. The method can effectively reduce the recarburization caused by the reaction of the molten steel with refractory materials, covering agents and the like in the casting process of the ultra-low carbon steel, thereby effectively reducing the decarbonization pressure of the smelting process before casting and reducing the smelting cost and period.
Detailed Description
The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
The practical parameters and the practical effect comparison table are shown in table 1:
TABLE 1
Example 1
A method for casting ultra-low carbon steel by protecting a tundish comprises the following steps:
s1, casting ultra-low carbon steel, wherein during casting, a mixed gas of carbon dioxide and argon is blown out by a tundish cover blowing device; the mass fraction of the element C in the steel grade of the ultra-low carbon steel is 0.01 percent; on the basis of the flow rate of the protective gas for the all-argon tundish cover, the gas flow rate increase caused by two units of CO gas generated per unit volume of carbon dioxide gas needs to be considered. And detecting the CO gas once at intervals of 5 minutes by a CO detector, and recording the rising trend of the concentration of the CO gas for comparison and judgment.
At the casting temperature T, according to the formula:
C+CO2(g)→2CO(g)，ΔG＝144700-1295T
wherein C is the carbon content in the ultra-low carbon steel, CO2Δ G is constant-2.18X 10 for the mass of carbon dioxide6；
When the casting temperature was 1600 ℃, the reaction Δ G ═ 2.18 × 106And the reaction can be continuously carried out rightwards along with the discharge of the product CO, and the reaction is continuously carried out rightwards in the pouring process according to the melting point and pouring temperature control habit of the ultra-low carbon steel.
In practice, CO2The conversion rate of → CO is not 100%, which depends on many factors such as the installation distribution of the gas shield device, the temperature of the molten steel to be cast, the tundish structure, and the like. Through a large number of theoretical calculations, numerical simulation and industrial tests, the method obtains the result by groping that CO in the protective gas of the tundish cover is contained in the tundish cover within 5min before casting2The volume fraction is slightly higher and is 10 percent, the carbon content of the molten steel can be effectively reduced, and then CO is added to the molten steel until the casting is finished2The volume fraction is 5%, the flow of the mixed gas of carbon dioxide and argon is changed along with the casting tonnage step change in the tundish, and the flow is 200 NL/min;
s2, in the mixed gas of carbon dioxide and argon gas blown out by the tundish cover blowing device, the volume fraction of the carbon dioxide gas is along with the casting, when the casting is started for 1min, the volume fraction of the carbon dioxide is 10% in the mixed gas of the carbon dioxide and argon gas blown out by the tundish cover blowing device, and the flow rate of the carbon dioxide gas is 1500 NL/min; the flow of the mixed gas of the carbon dioxide and the argon is changed along with the casting tonnage step change in the tundish, and the flow is 200 NL/min;
s3, casting time is 5min, and then casting is finished, wherein the volume fraction of carbon dioxide gas is 5%, and the gas flow is 200 NL/min.
Example 2
A method for casting ultra-low carbon steel by protecting a tundish comprises the following steps:
s1, casting ultra-low carbon steel, wherein during casting, a mixed gas of carbon dioxide and argon is blown out by a tundish cover blowing device; the mass fraction of the element C in the steel grade of the ultra-low carbon steel is 0.001 percent; on the basis of the flow rate of the protective gas for the all-argon tundish cover, the gas flow rate increase caused by two units of CO gas generated per unit volume of carbon dioxide gas needs to be considered. The CO gas is detected once at intervals of 10 minutes by a CO detector, and the rising trend of the CO gas concentration is judged by recording and comparing.
At the casting temperature T, according to the formula:
C+CO2(g)→2CO(g)，ΔG＝144700-1295T
wherein C is the carbon content in the ultra-low carbon steel, CO2Δ G is constant-2.18X 10 for the mass of carbon dioxide6；
When the casting temperature was 1635 ℃, the reaction Δ G ═ 2.18 × 106The reaction can be continuously carried out rightwards along with the discharge of CO products, and the reaction is continuously carried out rightwards in the pouring process according to the melting point and pouring temperature control habit of the ultra-low carbon steel;
in practice, CO2The conversion rate of → CO is not 100%, which depends on many factors such as the installation distribution of the gas shield device, the temperature of the molten steel to be cast, the tundish structure, and the like. Through a large number of theoretical calculations, numerical simulation and industrial tests, the method obtains the result by groping that CO in the protective gas of the tundish cover is contained in the tundish cover within 5min before casting2The volume fraction is slightly higher and is 10-30 percent, the carbon content of the molten steel can be effectively reduced, and then CO is added to the molten steel until the casting is finished2The volume fraction is 15%, the flow of the mixed gas of the carbon dioxide and the argon is changed along with the casting tonnage step change in the tundish, and the flow is 200-2500 NL/min;
s2, in the mixed gas of carbon dioxide and argon gas blown out by the tundish cover blowing device, the volume fraction of the carbon dioxide gas is along with the casting, when the casting is started for 5min, the volume fraction of the carbon dioxide is 30% in the mixed gas of the carbon dioxide and argon gas blown out by the tundish cover blowing device, and the flow rate of the carbon dioxide gas is 2500 NL/min; the flow of the mixed gas of the carbon dioxide and the argon is changed along with the casting tonnage step change in the tundish, and the flow is 2500 NL/min;
s3, casting for 5min till the end of casting, wherein the volume fraction of carbon dioxide gas is 15%, and the gas flow is 1500 NL/min.
Example 3
A method for casting ultra-low carbon steel by protecting a tundish comprises the following steps:
s1, casting ultra-low carbon steel, wherein during casting, a mixed gas of carbon dioxide and argon is blown out by a tundish cover blowing device; the mass fraction of the C element in the steel grade of the ultra-low carbon steel is 0.002 percent; on the basis of the flow rate of the protective gas for the all-argon tundish cover, the gas flow rate increase caused by two units of CO gas generated per unit volume of carbon dioxide gas needs to be considered. The CO gas is detected once at intervals of 6 minutes by a CO detector, and the rising trend of the CO gas concentration is judged by recording and comparing.
At the casting temperature T, according to the formula:
C+CO2(g)→2CO(g)，ΔG＝144700-1295T
wherein C is the carbon content in the ultra-low carbon steel, CO2Δ G is constant-2.18X 10 for the mass of carbon dioxide6；
When the casting temperature was 1630 ℃, the reaction Δ G ═ 2.18 × 106The reaction can be continuously carried out rightwards along with the discharge of CO products, and the reaction is continuously carried out rightwards in the pouring process according to the melting point and pouring temperature control habit of the ultra-low carbon steel;
in practice, CO2The conversion rate of → CO is not 100%, which depends on many factors such as the installation distribution of the gas shield device, the temperature of the molten steel to be cast, the tundish structure, and the like. Through a large number of theoretical calculations, numerical simulation and industrial tests, the method is obtained by groping in the protective gas of the tundish cover within 5min before castingCO2The volume fraction is slightly higher and is 11 percent, the carbon content of the molten steel can be effectively reduced, and then CO is added to the molten steel until the casting is finished2The volume fraction is 6%, the flow of the mixed gas of carbon dioxide and argon is changed along with the casting tonnage step change in the tundish, and the flow is 200 NL/min;
s2, in the mixed gas of carbon dioxide and argon gas blown out by the tundish cover blowing device, the volume fraction of the carbon dioxide gas is along with the progress of casting, when the casting is started for 3min, the volume fraction of the carbon dioxide is 13% in the mixed gas of the carbon dioxide and argon gas blown out by the tundish cover blowing device, and the flow rate of the carbon dioxide gas is 1503 NL/min; the flow of the mixed gas of carbon dioxide and argon is changed along with the casting tonnage step change in the tundish, and the flow is 202 NL/min;
s3, after the casting time is 5min until the casting is finished, the volume fraction of the carbon dioxide gas is 5% -15%, and the gas flow is 205 NL/min.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (3)
1. A method for casting ultra-low carbon steel by protecting a tundish is characterized by comprising the following steps: the method comprises the following steps:
s1, casting ultra-low carbon steel, wherein during casting, a mixed gas of carbon dioxide and argon is blown out by a tundish cover blowing device, and the mass fraction of the element C in the steel grade of the ultra-low carbon steel is 0.001-0.01%;
s2, when casting is started for 0-5min, the flow of the carbon dioxide gas is 1500-2500NL/min in the mixed gas of the carbon dioxide and the argon blown out by the tundish cover blowing device, the flow of the mixed gas of the carbon dioxide and the argon is 200-2500NL/min along with the step change of casting tonnage in a tundish, and the volume fraction of the carbon dioxide in the tundish cover protective gas is 10-30% in 5min before casting is started;
s3, casting time is 5min, and then casting is finished, the volume fraction of carbon dioxide gas is 5% -15%, and the gas flow is 200-1500 NL/min.
2. The tundish protection casting method of ultra-low carbon steel according to claim 1, characterized in that: on the basis of the flow rate of the protective gas for the all-argon tundish cover, the gas flow rate increase caused by two units of CO gas generated per unit volume of carbon dioxide gas needs to be considered.
3. The tundish protection casting method of ultra-low carbon steel according to claim 2, characterized in that: and detecting the CO gas once at intervals of 5-10 minutes by a CO detector, and recording and comparing to judge the rising trend of the CO gas concentration.
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