A method for detecting a tundish molten steel level

Abstract

This invention discloses a method for detecting the molten steel level in a tundish, comprising the following steps: S1, calculating the outlet flow rate of molten steel in the crystallizer during casting; S2, calculating the inlet flow rate of molten steel in the crystallizer during casting; S3, calculating the opening degree and passage area of ​​the stopper rod; S4, deriving the relationship between the opening degree of the stopper rod and the height of the tundish based on the consecutive equations in steps S1 and S2, and substituting this relationship into the equation in step S3. This invention not only directly detects the molten steel level in the tundish, achieving high accuracy, but also features low installation and maintenance costs, reusability, and precise detection of the molten steel level even when the tundish covering agent has formed a crust.

Description

Technical Field

[0001] This invention relates to continuous casting technology, and more specifically, to a method for detecting the level of molten steel in a tundish. Background Technology

[0002] The tundish is the final step in the process of molten steel entering the crystallizer. The tundish primarily serves several metallurgical functions: flow diversion, pressure stabilization, prevention of secondary oxidation, and inclusion removal. Among these, the pressure stabilization function involves providing a stable molten steel level to maintain static pressure. Therefore, accurate detection and control of the molten steel level in the tundish are crucial.

[0003] Currently, the main methods for detecting molten steel level include weighing method, electromagnetic eddy current method, and radar method.

[0004] Weighing method: The total weight of the container is measured by a sensor placed on the base of the molten steel container to calculate the molten steel level. The main method for detecting the molten steel level in the tundish is the weighing method. For example, Chinese Patent 201420005211.X discloses a weighing device for a high-temperature continuous casting tundish. However, this method is an indirect method for detecting the liquid level, and the accuracy of the liquid level detection is low. The cost and maintenance cost of placing multiple sensor devices are relatively high.

[0005] Electromagnetic eddy current method: For example, Chinese patent 200510113914.X discloses a steel liquid level detection device using an electromagnetic coil. It mainly uses the electromagnetic field generated by the electromagnetic coil to detect the height of the molten steel liquid level. The electromagnetic eddy current method has high accuracy in detecting liquid level, but this method has a limited range, generally only 200mm, so it is generally only used for liquid level detection in crystallizers.

[0006] Radar method: For example, Chinese patent 200620096300.5 discloses a radar molten steel level detection system, which mainly uses radar waves to detect the molten steel level. The radar method has high detection accuracy, but the probe is relatively sensitive to obstruction and ambient temperature.

[0007] Research on existing molten steel level detection technologies has revealed that the current technical challenges in tundish molten steel level detection lie in:

[0008] (1) The large package is located above the intermediate package. The space above the intermediate package is relatively small, so the installation space for testing equipment is limited.

[0009] (2) The tundish is covered with a tundish cover. The liquid level detection device can only detect the liquid level of molten steel in the tundish through the opening on the cover. The temperature above the tundish cover opening is very high, reaching over 500 degrees Celsius, which is generally unbearable for liquid level gauge probes.

[0010] (3) Sometimes the coating on the molten steel in the tundish will form a crust during the pouring process. Under the condition of crusting of the coating agent, ordinary liquid level detection devices cannot accurately detect the height of the molten steel level. Summary of the Invention

[0011] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for detecting the molten steel level in a tundish. This method can not only directly detect the molten steel level in the tundish, but also achieve high accuracy in molten steel level detection. Furthermore, this molten steel level detection technology has low installation and maintenance costs, is reusable, and can accurately detect the molten steel level in the tundish even when the tundish covering agent has formed a crust.

[0012] To achieve the above objectives, the present invention adopts the following technical solution:

[0013] A method for detecting the level of molten steel in a tundish includes the following steps:

[0014] S1. Calculate the flow rate of molten steel at the outlet of the crystallizer during the casting process;

[0015] S2. Calculate the inlet flow rate of molten steel in the crystallizer during the casting process;

[0016] S3. Calculate the opening degree and the area of ​​the through rod;

[0017] S4. Based on the equations obtained from steps S1 and S2, derive the relationship between the opening of the stopper rod and the height of the intermediate package, and substitute it into the relationship from step S3.

[0018] Preferably, the outlet molten steel flow rate of the crystallizer in step S1 is calculated as follows:

[0019]

[0020] In the formula, Q m ρ is the outlet flow rate of molten steel from the crystallizer, in kg / s. s For the density of the steel billet, take (7850*0.1+7200*0.9) kg / m³. 3 a and b are the cross-sectional dimensions of the cast billet, in meters; V c The pulling speed is expressed in m / min.

[0021] Preferably, the inlet flow rate of the molten steel in the crystallizer in step S2 is calculated as follows:

[0022]

[0023] In the formula, Q k ρ is the inlet flow rate of molten steel in the crystallizer, in kg / s. L For the density of molten steel, take 7200 kg / m³. 3h represents the depth of molten steel in the tundish, in meters; S(x) represents the opening area under the flow control effect of the stopper rod, in square meters. 2 C(x) is the correction coefficient; x is the position of the stopper rod. When the stopper rod and the submerged nozzle are completely in contact, blocking the flow of molten steel, the value of x is 0. The height that the stopper rod travels upwards based on this is the opening distance, in meters.

[0024] Preferably, the opening degree of the stopper rod in step S3 is calculated as follows:

[0025]

[0026] In the formula, L(x) is the opening line of the stopper rod, in meters; m is the distance from the center line of the stopper rod to the center point of the arc surface of the bowl, in meters; n is the distance in the numerical direction between the centers of the two arc surfaces when the stopper rod is closed, in meters; r1 is the radius of the arc surface of the stopper rod, in meters; r2 is the radius of the arc surface of the bowl, in meters; x is the position of the stopper rod. When the stopper rod and the submerged nozzle are completely in contact, blocking the outflow of molten steel, the value of x is 0. The height that the stopper rod travels upwards from this position is the opening distance, in meters.

[0027] The area of ​​the steel structure is calculated as follows:

[0028]

[0029] Substituting formula (3) into formula (4) yields:

[0030]

[0031] In the formula, S(x) is the area of ​​the steel passage between the stopper rod and the bowl, in meters. 2 L(x) is the minimum distance between the stopper rod and the bowl opening, in meters; m is the distance from the centerline of the stopper rod to the center point of the arc surface of the bowl opening, in meters; n is the distance in the numerical direction between the centers of the two arc surfaces when the stopper rod is closed, in meters; r1 is the radius of the arc surface of the stopper rod, in meters; r2 is the radius of the arc surface of the bowl opening, in meters; x is the position of the stopper rod. When the stopper rod and the submerged nozzle are completely in contact, blocking the outflow of molten steel, the value of x is 0. The height that the stopper rod travels upwards from this position is the opening distance, in meters.

[0032] Preferably, the relationship substituted into the equation from step S3 in step S4 is as follows:

[0033] Q m =Q K (6)

[0034]

[0035]

[0036] Substituting formula (5) into formula (8) yields:

[0037]

[0038] In the formula, h is the depth of molten steel in the tundish, in meters; m is the distance from the centerline of the stopper rod to the center point of the arc surface of the bowl, in meters; n is the distance in the numerical direction between the centers of the two arc surfaces when the stopper rod is closed, in meters; r1 is the radius of the arc surface of the stopper rod, in meters; r2 is the radius of the arc surface of the bowl, in meters; ρ s For the density of the steel billet, take (7850*0.1+7200*0.9) kg / m³. 3 ;ρ L For the density of molten steel, take 7200 kg / m³. 3 a and b are the cross-sectional dimensions of the cast billet, in meters; V c The value is the casting speed, in m / min; C(x) is the correction coefficient, ranging from 0.6 to 0.9; x is the position of the stopper rod. When the stopper rod and the submerged nozzle are completely in contact, blocking the flow of molten steel, the value of x is 0. The height of the upward movement based on this is the opening distance, in m.

[0039] The method for detecting the molten steel level in a tundish provided by this invention has the following advantages:

[0040] 1) A relationship between the intermediate drum liquid level and the stopper position was established, and the intermediate drum liquid level was monitored in real time by detecting the stopper position value;

[0041] 2) The detection method of the present invention can directly detect the molten steel level in the tundish, and the detection accuracy of the molten steel level is high, achieving the accuracy of online control;

[0042] 3) The detection method of this invention has low maintenance costs and can be reused;

[0043] 4) The detection method of the present invention can accurately detect the liquid level of molten steel in the tundish even when the tundish covering agent is in a crusting state. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the parameters in the detection method of the present invention;

[0045] 1-stopper, 2-bowl opening

[0046] Figure 2 This is a schematic diagram showing the relationship between the stopper opening and the intermediate batch liquid level in an embodiment of the detection method of the present invention. Detailed Implementation

[0047] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0048] The present invention provides a method for detecting the level of molten steel in a tundish, comprising the following steps:

[0049] S1. Calculate the flow rate of molten steel at the outlet of the crystallizer during the casting process:

[0050]

[0051] In the formula, Q m ρ is the outlet flow rate of molten steel from the crystallizer, in kg / s. s For the density of the steel billet, take (7850*0.1+7200*0.9) kg / m³. 3 a and b are the cross-sectional dimensions of the cast billet, in meters; V c The pulling speed is expressed in m / min.

[0052] S2. Calculate the inlet flow rate of molten steel in the crystallizer during the casting process:

[0053] In continuous casting, the opening degree of the tundish nozzle is controlled by a stopper rod to regulate the flow rate of molten steel from the tundish into the crystallizer, thereby maintaining a stable molten steel level. According to formula (1), under the flow control effect of the stopper rod, the mass of molten steel flowing into the upper opening of the crystallizer is mainly calculated from the tundish liquid level height and the stopper rod opening degree, with the flow rate Q... k for:

[0054]

[0055] In the formula, Q k ρ is the inlet flow rate of molten steel in the crystallizer, in kg / s. L For the density of molten steel, take 7200 kg / m³. 3 h represents the depth of molten steel in the tundish, in meters; S(x) represents the opening area under the flow control effect of the stopper rod, in square meters. 2 C(x) is the correction coefficient; x is the position of the stopper rod. When the stopper rod and the submerged nozzle are completely in contact, blocking the flow of molten steel, the value of x is 0. The height that the stopper rod travels upwards based on this is the opening distance, in meters.

[0056] S3. Calculate the opening degree and the area of ​​the steel passage of the stopper rod:

[0057] The stopper rod opening line L(x): The minimum geometric distance (in mm) between the stopper rod and the submersible nozzle when the stopper rod opening position is x. Figure 1 The geometric relationships shown can be used to calculate the expression for the opening line.

[0058]

[0059] In the formula, L(x) is the opening line of stopper rod 1, in meters; m is the distance from the center line of stopper rod 1 to the center point of the arc surface of bowl 2, in meters; n is the distance in the numerical direction between the centers of the two arc surfaces when stopper rod 1 is closed, in meters; r1 is the radius of the arc surface of stopper rod 1, in meters; r2 is the radius of the arc surface of bowl 2, in meters; x is the position of stopper rod 1. When stopper rod 1 and submersible nozzle are completely in contact, blocking the outflow of molten steel, the value of x is 0. The height that it travels upwards based on this is the opening distance, in meters.

[0060] Area S(x) of the stopper rod: The area of ​​the surface formed by rotating the opening line along the center line of the stopper rod when the opening distance of stopper rod 1 is x (unit: mm). 2 The calculation is as follows:

[0061]

[0062] Substituting formula (3) into formula (4) yields:

[0063]

[0064] In the formula, S(x) is the area of ​​the steel passage between stopper rod 1 and bowl 2, in meters. 2 L(x) is the minimum distance between stopper rod 1 and bowl 2, in meters; m is the distance from the centerline of stopper rod 1 to the center point of the arc surface of bowl 2, in meters; n is the distance in the numerical direction between the centers of the two arc surfaces when stopper rod 1 is closed, in meters; r1 is the radius of the arc surface of stopper rod 1, in meters; r2 is the radius of the arc surface of bowl 2, in meters; x is the position of stopper rod. When stopper rod 1 and submerged nozzle are completely in contact, blocking the outflow of molten steel, the value of x is 0. The height of upward movement based on this is the opening distance, in meters.

[0065] S4. The mass of the molten steel flowing into the top of the crystallizer and the mass of the billet exiting the bottom of the crystallizer are equal. Using this equation, derive the relationship between the stopper rod opening and the liquid level in the tundish, and substitute this into the relationship between the stopper rod opening and the steel passage area:

[0066] Q m =Q K (6)

[0067]

[0068]

[0069] Substituting formula (5) into formula (8) yields:

[0070]

[0071] In the formula, h is the depth of molten steel in the tundish, in meters; m is the distance from the centerline of the stopper rod to the center point of the arc surface of the bowl, in meters; n is the distance in the numerical direction between the centers of the two arc surfaces when the stopper rod is closed, in meters; r1 is the radius of the arc surface of the stopper rod, in meters; r2 is the radius of the arc surface of the bowl, in meters; ρ s For the density of the steel billet, take (7850*0.1+7200*0.9) kg / m³. 3 ;ρ L For the density of molten steel, take 7200 kg / m³. 3 a and b are the cross-sectional dimensions of the cast billet, in meters; V c The drawing speed is expressed in m / min; C(x) is a correction factor; x is the position of the stopper rod. When the stopper rod and the submerged nozzle are completely in contact, blocking the flow of molten steel, the value of x is 0. The height that the rod travels upwards from this position is the opening distance, expressed in m.

[0072] During the casting process, since other parameters remain unstable, only the tundish liquid level and stopper position change over time, thus establishing the relationship between the tundish liquid level h and the stopper position x.

[0073] The accurate value of the intermediate drum liquid level height h can be directly obtained by using the stopper position x, and then the intermediate drum liquid level height h can be monitored in real time by detecting the stopper position value.

[0074] Example

[0075] The casting process parameters for a certain casting machine are shown in the table below:

[0076] Process parameters numerical values Crystallizer cross-sectional thickness a 0.25m Crystallizer cross-sectional width b 1.5m <![CDATA[Drawing speed V c > 1.5m / min <![CDATA[Radius r1 of the stopper arc surface]]> 0.054m <![CDATA[Radius r2 of the arc surface at the bowl mouth]]> 0.05m The distance from the centerline of the stopper rod to the center point of the curved surface of the bowl is m 0.092m The vertical distance n between the centers of the two arc surfaces when the stopper is closed. 0.0485m

[0077] During the casting process, the molten steel level in the mold remains stable, so the mass of the molten steel flowing into the mold from the top and the mass of the billet exiting the mold from the bottom are equal. The mass of the billet exiting the bottom of the mold can be calculated from the casting speed and cross-sectional dimensions, while the mass of the molten steel flowing into the top of the mold is mainly calculated from the tundish level and the stopper rod opening. Therefore, an equation can be established between the stopper rod opening and the tundish level, and the tundish level can be calculated using the stopper rod opening. The specific calculation parameters and process are as follows:

[0078] (1) Flow rate of molten steel at the outlet of the crystallizer during the casting process:

[0079] a = 0.25m, b = 1.5m, V c =1.5m / min, ρ s =7265kg / m 3

[0080]

[0081] (2) Flow rate of molten steel at the inlet of the crystallizer during the casting process:

[0082] In continuous casting, the opening degree of the tundish nozzle is controlled by a stopper rod to regulate the flow rate of molten steel from the tundish into the mold, thereby maintaining a stable molten steel level. Based on the above formula, under the flow control effect of the stopper rod, the mass of molten steel flowing into the upper opening of the mold is mainly calculated from the tundish liquid level height and the stopper rod opening degree, with the flow rate Q being... k for:

[0083]

[0084] (3) Formulas for calculating stopper rod opening and steel passage area

[0085] Based on the dimensions of the stopper rod and sprue at the site, the following calculations were performed:

[0086] r1=0.054m, r2=0.050m, m=42.5mm+50mm=0.0925m, n=0.0485m

[0087] Substituting into formula (3), we get:

[0088] Substituting into formula (4), we get:

[0089] (4) The mass of the molten steel flowing into the upper opening of the crystallizer and the mass of the billet exiting the lower opening of the crystallizer are equal. Using the same equation, we can derive the relationship between the stopper opening and the liquid level in the tundish, and substitute this relationship with the steel passage area:

[0090] Q m =Q K (14)

[0091]

[0092]

[0093] Q m =68.1kg / s, ρ L =7200kg / m 3 C(x) = 0.82, g = 9.8, and formula (13) are substituted into

[0094]

[0095] This embodiment accurately detects the tundish liquid level height by detecting the stopper rod opening position and the molten steel flow rate. The data of the tundish liquid level height detected in this embodiment are as follows: Figure 2 As shown.

[0096] In summary, the tundish molten steel level detection method of the present invention establishes an equation relating the stopper opening and the tundish molten steel level, calculating the tundish molten steel level height using the stopper opening. It allows for direct detection of the tundish molten steel level with high accuracy, achieving the precision required for online control. The method accurately detects the tundish molten steel level and is reusable. Furthermore, the tundish molten steel level detection device can accurately detect the molten steel level even when the tundish covering agent has formed a crust.

[0097] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A method of detecting a tundish liquid level, characterized by, It comprises the following steps: S1, calculating the outlet molten steel flow rate of the crystallizer in the pouring process; S2, calculating the inlet molten steel flow rate of the crystallizer in the pouring process; S3, calculating the opening degree of the stopper and the steel passing area; S4, according to the equal simultaneous equations of step S1 and step S2, deriving the relationship between the opening degree of the stopper and the height of the tundish, and substituting the relationship of step S3, In the step S1, the outlet molten steel flow rate of the crystallizer is calculated as follows: In the formula, Q m is the outlet liquid steel flow of the crystallizer, in kg / s; ρ s ρ is the density of the billet, in kg / m 3 ; a and b are the cross-sectional dimensions of the casting blank, in units of m; V c for the speed, in m / min, In the step S2, the inlet molten steel flow rate of the crystallizer is calculated as follows: In the formula, Q k is the inlet liquid steel flow of the crystallizer, in kg / s; p L p is the density of the steel, in kg / m3 3 ; h is the molten steel depth of the tundish, in units of m; C(x) is the correction coefficient; x is the stopper position, when the stopper and the submerged entry nozzle completely fit and block the outflow of the molten steel, the value of x is 0, and the height of the upward walking based on this is the opening distance, in units of m, In the step S3, the opening degree of the stopper is calculated as follows: The steel passing area is calculated as follows: Substituting formula (3) into formula (4) can obtain: In the formula, S(x) is the cross-sectional area of the steel passing between the stopper and the bowl, in m2 2 ; L(x) is the minimum distance between the stopper and the bowl mouth, in units of m; m is the distance from the center line of the stopper to the arc center point of the bowl mouth, in units of m; n is the vertical distance between the two arc centers of the stopper and the bowl mouth when the stopper is closed, in units of m; r1 is the radius of the arc surface of the stopper, in units of m; r2 is the radius of the arc surface of the bowl mouth, in units of m; x is the stopper position, when the stopper and the submerged entry nozzle completely fit and block the outflow of the molten steel, the value of x is 0, and the height of the upward walking based on this is the opening distance, in units of m.

2. The method of tundish level detection according to claim 1, characterized in that, In the step S4, the equal simultaneous equations of step S1 and step S2 are specifically as follows: Q m = Q K (6) Substituting formula (5) into formula (8) can obtain: In the formula, h is the molten steel depth of the tundish, in units of m; m is the distance from the center line of the stopper to the arc center point of the bowl mouth, in units of m; n is the vertical distance between the two arc centers of the stopper and the bowl mouth when the stopper is closed, in units of m; r1 is the radius of the arc surface of the stopper, in units of m; r2 is the radius of the arc surface of the bowl mouth, in units of m; p s p is the density of the billet, in kg / m 3 ; p L p is the density of the steel, in kg / m3 3 ; a and b are the cross-sectional dimensions of the casting blank, in units of m; V c for the pulling speed, in m / min; C(x) is the correction coefficient; x is the stopper position, when the stopper and the submerged entry nozzle completely fit and block the outflow of the molten steel, the value of x is 0, and the height of the upward walking based on this is the opening distance, in units of m.

3. The tundish molten steel level detection method according to claim 2, characterized in that, In formula (1), formula (2), and formula (9), ρ s Take (7850*0.1+7200*0.9) kg / m 3 , ρ L Take 7200 kg / m 3 .

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