Real-time quantitative analysis method for blocking of continuous casting tundish stopper rod head based on steel flow

Abstract

The invention relates to a real-time quantitative analysis method for stopper rod head blockage of a continuous casting tundish based on steel flow, which comprises the following steps of: 1, determining a linear relation between the depth of a stopper rod and a theoretical sectional area, 2, determining the theoretical sectional area, 3, determining the actual volume flow rate of tundish molten steel entering a crystallizer, 4, determining the actual flow rate of stopper rod head steel flow, and 5, determining the actual flow rate of the stopper rod head steel flow. 5, the actual sectional area is determined; 6, the blocking rate of the stopper rod head is determined; according to the scheme, the blocking degree of the tundish stopper rod is provided online in real time, the blocking degree of the tundish stopper rod is quantitatively described, and the blocking rate of the tundish stopper rod head can be obtained through simple operation based on field real-time production data.

Description

Technical Field

[0001] The invention relates to an analysis method, in particular to a real-time quantitative analysis method for continuous casting tundish plug rod head blockage based on steel flow, and belongs to the technical field of steelmaking and refining processes. Background Art

[0002] The stopper mechanism is the most common flow control device in the continuous casting process, and is also a liquid level control device for the continuous casting mold. Figure 1 As shown in the figure, the principle of the stopper rod flow control device is to change the cross-sectional area between the stopper rod head and the upper water inlet by the stopper rod height to control the steel flow rate from the tundish into the crystallizer. However, during the pouring process, non-metallic inclusions in the steel are easy to adhere to the stopper rod head, resulting in a decrease in the cross-sectional area between the stopper rod head and the upper water inlet. This destroys the corresponding relationship between the stopper rod height and the cross-sectional area, resulting in a decrease in the stopper rod flow control accuracy. The degree of blockage of the stopper rod head determines the degree of decrease in the stopper rod flow control accuracy. In addition, as the blockage degree at the stopper rod head increases, the stopper rod curve continues to rise. However, under the action of molten steel flushing, the non-metallic inclusions adhered to the stopper rod head fall off, resulting in an instantaneous increase in the cross-sectional area between the stopper rod head and the upper water inlet. This causes the crystallizer liquid level to suddenly surge. At this time, the billet is very likely to have surface longitudinal cracks. Therefore, excessive liquid level fluctuations are one of the important factors that deteriorate the surface quality of the billet. However, the prerequisite for controlling the blockage of the stopper rod head is that the blockage degree of the stopper rod head can be quantitatively analyzed. At present, the stopper rod head is only qualitatively judged based on the stopper rod curve to determine whether it is blocked. Therefore, an analytical method based on field production data to quantitatively describe the degree of blockage of the continuous casting tundish plug rod head in real time is very important.

[0003] After searching, the Chinese patent "CN 116237484 B" discloses a method for judging the nodule and steel liquid deviation of the submerged nozzle of the crystallizer. The method uses the wavelet energy analysis method to analyze the liquid level fluctuation data of the narrow surface area of ​​the crystallizer to obtain a qualitative description of the nodule and steel liquid deviation of the submerged nozzle. The Chinese patent "CN 114012053 A" discloses a method for judging the abnormal state of nodule blockage of the submerged nozzle of the crystallizer. The method obtains the isotherm diagram according to the temperature value of the crystallizer temperature measuring point, determines the liquid level position of the molten steel in the crystallizer, detects the fluctuation of the liquid level, and determines the nodule position and blockage degree of the crystallizer. The Chinese patent "CN 113426974 B" discloses a method for analyzing the nodule of the continuous casting nozzle. The method constructs a corresponding steel liquid continuous casting model. The model simulates the nodule process through ferromagnetic particles to determine the relationship between the nodule behavior data and the liquid level fluctuation. Chinese patent "CN 110883332 A" discloses a method and system for online detection of nozzle blockage, which qualitatively determines nozzle blockage by the height of the stopper rod at different times. Chinese patent "CN 109759573 A" discloses a method for suppressing nodules on the inner wall of an immersed nozzle by using pulse current, which constructs a method for suppressing nodules on the inner wall of the nozzle and protecting the immersed nozzle by using pulse current. Chinese patent "CN 109579902 A" discloses a device and method for evaluating the blockage of a crystallizer nozzle, which designs a device for evaluating the blockage of a crystallizer nozzle, through which the degree of nozzle blockage can be quantitatively described offline. Chinese patent "CN 114850465A" discloses a system and method for predicting the castability of molten steel, which constructs a model for predicting the thickness of molten steel casting nodules and evaluating the castability of molten steel, which is composed of modules such as inclusion physical property data, boundary layer velocity distribution law, and molten steel property data.

[0004] The above 7 patents were found by searching patents with the two keywords of nodule blockage and analysis. It can be seen from the above patents that, firstly, the patents on nodule blockage are mainly about the blockage of submerged nozzles; secondly, the above related patents are mostly qualitative interpretations of the occurrence of blockage; thirdly, the 6th and 7th patents are offline quantitative descriptions of submerged nozzles and prediction models of blockage, respectively. However, there is still no report on the quantitative analysis of the blockage degree of the stopper rod, especially the real-time quantitative analysis method based on production data. Summary of the invention

[0005] The present invention aims at the problems existing in the prior art and provides a real-time quantitative analysis method for continuous casting tundish plug rod head blockage based on steel flow. The method can directly give the quantitative analysis result of the degree of continuous casting tundish plug rod head blockage based on on-site real-time production data.

[0006] In order to achieve the above-mentioned purpose, the technical solution of the present invention is as follows: the prerequisite for the quantitative analysis of the degree of stopper rod blockage is the mathematical description of the problem. First, when there is no blockage, there is a one-to-one linear relationship between the depth of the stopper rod inserted into the tundish and the cross-sectional area between the stopper rod and the upper water inlet. At the same time, as mentioned above, the most intuitive manifestation of the blockage of the stopper rod head is the reduction of the cross-sectional area between the stopper rod head and the upper water inlet. In order to ensure the flow of molten steel entering the crystallizer from the tundish, the control system automatically reduces the insertion depth of the stopper rod to increase the cross-sectional area. It can be seen that the blockage of the stopper rod head causes a difference between the theoretical cross-sectional area and the actual cross-sectional area at a certain stopper rod depth. Accordingly, the present invention defines the blockage rate of the stopper rod head of the continuous casting tundish as:

[0007]

[0008] Where, η is the plugging rate of the tundish plug; S A is the actual cross-sectional area; S T It is the size of the theoretical cross-sectional area. If the actual cross-sectional area at a certain depth is equal to the theoretical cross-sectional area, the plugging rate of the tundish plug rod head is 0, indicating that the plug rod head is not blocked at this time; if the actual cross-sectional area at a certain depth is 0, the plugging rate of the tundish plug rod head is 1, indicating that the plug rod head is completely blocked at this time.

[0009] According to formula (1), the plugging rate of the stopper can be obtained by simply obtaining the theoretical cross-sectional area and the actual cross-sectional area at a certain stopper rod depth. As mentioned above, there is a one-to-one linear relationship between the theoretical cross-sectional area and the stopper rod depth, and this linear relationship is only related to the size of the stopper rod and the upper water inlet. At the same time, the actual volume flow rate of the tundish steel liquid entering the crystallizer during pouring is the product of the steel flow rate at the stopper rod and the actual cross-sectional area, as shown in formula (2).

[0010] Q A =S A ·v (2)

[0011] In the formula, Q A is the actual volume flow rate entering the crystallizer, m 3 / min; v is the steel flow velocity passing through the plug head, m / min.

[0012] As mentioned above, by determining the actual volume flow rate of molten steel entering the crystallizer and the steel flow rate through the stopper rod head, the actual cross-sectional area of ​​a certain stopper rod depth can be obtained. The theoretical cross-sectional area corresponding to the stopper rod depth can be obtained by determining the stopper rod depth. According to formula (1), the degree of blockage of the stopper rod head can be quantitatively described based on the theoretical cross-sectional area and the actual cross-sectional area. In order to achieve the above purpose, a quantitative analysis method for the blockage of the stopper rod head of the continuous casting tundish based on the steel flow rate is provided, and the method comprises the following steps:

[0013] Step 1: Determine the linear relationship between stopper rod depth and theoretical cross-sectional area. The linear relationship between stopper rod depth and theoretical cross-sectional area is given based on the qualitative dimensions of the stopper rod head and the upper nozzle.

[0014] Step 2: Determine the theoretical cross-sectional area. As mentioned above, the theoretical cross-sectional area during the pouring process depends on the stopper rod depth. The theoretical cross-sectional area can be obtained by simply determining the actual stopper rod depth. To this end, based on the L1 real-time stopper rod depth and the aforementioned linear relationship between the stopper rod depth and the theoretical cross-sectional area, the theoretical cross-sectional area between the stopper rod head and the upper water inlet at the stopper rod depth is determined.

[0015] Step 3: Determine the actual volume flow rate of the molten steel from the tundish into the crystallizer. After the pouring state stabilizes, the molten steel satisfies the continuity equation throughout the continuous casting machine. In other words, the volume flow rate of the molten steel at the stopper head is equal to the volume flow rate of the molten steel in the crystallizer. The volume flow rate of the molten steel in the crystallizer is the product of the cross-sectional dimensions of the crystallizer and the continuous casting speed. Therefore, the volume flow rate of the molten steel at the stopper head can be expressed as:

[0016] Q A =S s v s (3)

[0017] In the formula, S s is the cross-sectional area of ​​the crystallizer, m 2 ;v s is the continuous casting speed, m / min. Therefore, based on the L1 real-time crystallizer cross-sectional dimensions and the continuous casting speed, the actual volume flow rate of the tundish molten steel entering the crystallizer is determined according to formula (3).

[0018] Step 4: Determine the actual flow rate of the stopper head. Assume that the flow rate of the molten steel in the vertical direction of the tundish surface is 0m / s, and take the stopper head as the calculation reference surface. At the same time, the energy change of the molten steel in the tundish entering the crystallizer is the conversion of potential energy into kinetic energy and pressure loss.

[0019]

[0020] Where H is the depth of the tundish liquid level, m; g is the acceleration of gravity, m / s 2 ξ is the steel flow resistance coefficient. After reorganization, the actual flow velocity of the plug head steel flow can be expressed as:

[0021]

[0022] Based on the real-time tundish liquid level depth L1, the actual flow rate of the stopper head steel flow is determined according to formula (5).

[0023] Step 5: Determine the actual cross-sectional area. As mentioned above, according to formula (2), at a certain stopper rod depth, the actual cross-sectional area can be expressed as the ratio of the actual volume flow rate of the molten steel to the real-time flow rate of the molten steel at the stopper rod.

[0024]

[0025] Based on the actual volume flow rate of the tundish molten steel entering the crystallizer in step 3 and the actual flow rate of the stopper head steel flow in step 4, the actual cross-sectional area is determined according to formula (6).

[0026] Step 6: Determine the plugging rate of the plugging rod head. Based on the theoretical cross-sectional area in step 2 and the actual cross-sectional area in step 5, determine the real-time plugging rate of the plugging rod head according to formula (1).

[0027] Compared with the prior art, the present invention has the following advantages: (1) providing the degree of tundish plug rod blockage in real time online; (2) quantitatively describing the degree of tundish plug rod blockage; (3) obtaining the tundish plug rod head blockage rate through simple calculation based on on-site real-time production data; (4) according to the present invention, based on L1 real-time production data, the parameters for real-time monitoring of tundish blockage are calculated to provide a basis for tundish replacement operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of flow control principle of stopper flow control device;

[0029] Figure 2 Linear relationship between stopper rod depth and cross-sectional area of ​​the current stopper rod flow control structure. DETAILED DESCRIPTION

[0030] In order to deepen the understanding of the present invention, a detailed description is given below in conjunction with embodiments.

[0031] Example 1: A quantitative analysis method for tundish plug rod head blockage based on steel flow rate continuous casting, the method comprising the following steps:

[0032] Step 1: Determine the linear relationship between stopper rod depth and theoretical cross-sectional area. The linear relationship between stopper rod depth and theoretical cross-sectional area is given based on the qualitative dimensions of the stopper rod head and the upper nozzle.

[0033] Step 2: Determine the theoretical cross-sectional area. As mentioned above, the theoretical cross-sectional area during the pouring process depends on the stopper rod depth. The theoretical cross-sectional area can be obtained by simply determining the actual stopper rod depth. To this end, based on the L1 real-time stopper rod depth and the aforementioned linear relationship between the stopper rod depth and the theoretical cross-sectional area, the theoretical cross-sectional area between the stopper rod head and the upper water inlet at the stopper rod depth is determined.

[0034] Step 3: Determine the actual volume flow rate of the molten steel from the tundish into the crystallizer. After the pouring state stabilizes, the molten steel satisfies the continuity equation throughout the continuous casting machine. In other words, the volume flow rate of the molten steel at the stopper head is equal to the volume flow rate of the molten steel in the crystallizer. The volume flow rate of the molten steel in the crystallizer is the product of the cross-sectional dimensions of the crystallizer and the continuous casting speed. Therefore, the volume flow rate of the molten steel at the stopper head can be expressed as:

[0035] Q A =S s v s (3)

[0036] In the formula, S s is the cross-sectional area of ​​the crystallizer, m 2 ;v s is the continuous casting speed, m / min. Therefore, based on the L1 real-time crystallizer cross-sectional dimensions and the continuous casting speed, the actual volume flow rate of the tundish molten steel entering the crystallizer is determined according to formula (3).

[0037] Step 4: Determine the actual flow rate of the stopper head. Assume that the flow rate of the molten steel in the vertical direction of the tundish surface is 0m / s, and take the stopper head as the calculation reference surface. At the same time, the energy change of the molten steel in the tundish entering the crystallizer is the conversion of potential energy into kinetic energy and pressure loss.

[0038]

[0039] Where H is the depth of the tundish liquid level, m; g is the acceleration of gravity, m / s 2 ξ is the steel flow resistance coefficient. After reorganization, the actual flow velocity of the plug head steel flow can be expressed as:

[0040]

[0041] Based on the real-time tundish liquid level depth L1, the actual flow rate of the stopper head steel flow is determined according to formula (5).

[0042] Step 5: Determine the actual cross-sectional area. As mentioned above, according to formula (2), at a certain stopper rod depth, the actual cross-sectional area can be expressed as the ratio of the actual volume flow rate of the molten steel to the real-time flow rate of the molten steel at the stopper rod.

[0043]

[0044] Based on the actual volume flow rate of the tundish molten steel entering the crystallizer in step 3 and the actual flow rate of the stopper head steel flow in step 4, the actual cross-sectional area is determined according to formula (6).

[0045] Step 6: Determine the plugging rate of the plugging rod head. Based on the theoretical cross-sectional area in step 2 and the actual cross-sectional area in step 5, determine the real-time plugging rate of the plugging rod head according to formula (1).

[0046] Example 2: A quantitative analysis method for tundish plug rod head blockage based on steel flow rate continuous casting, the method comprising the following steps:

[0047] Step 1: Determine the linear relationship between stopper rod depth and theoretical cross-sectional area. Based on the qualitative dimensions of the stopper rod head and the upper nozzle, the linear relationship between the stopper rod depth and theoretical cross-sectional area is given, such as Figure 2 shown.

[0048] Step 2: Determine the theoretical cross-sectional area. L1 shows that the real-time height of the plug is 17 mm. Figure 2It can be seen that the theoretical cross-sectional area between the plug head and the upper water inlet at this plug height is 3.95×10 -3 m 2 .

[0049] Step 3: Determine the real-time volume flow rate of the tundish steel liquid entering the crystallizer. L1 shows that the real-time width of the crystallizer is 1.537m, the thickness is 0.25m, and the continuous casting speed is 1.4m / min. According to formula (3), the real-time volume flow rate of the tundish steel liquid entering the crystallizer is 0.538m 3 / min.

[0050] Step 4: Determine the actual flow rate of the steel flow at the stopper head. L1 shows that the real-time liquid level of the tundish is 1.208m, and ξ in formula (5) is 4. According to formula (5), the actual flow rate of the steel flow at the stopper head is 3.44m / s.

[0051] Step 5: Determine the actual cross-sectional area. Substituting the actual volume flow rate in step 3 and the actual flow rate in step 4 into equation (6), the actual cross-sectional area when the stopper rod height is 17 mm is calculated to be 3.69×10 -3 m 2 .

[0052] Step 6: Determine the plugging rate of the plugging rod head. Substituting the theoretical cross-sectional area of ​​step 2 and the actual cross-sectional area of ​​step 5 into equation (1), the real-time plugging rate of the plugging rod head is calculated to be 6.58%.

[0053] It should be noted that the above embodiments are not intended to limit the protection scope of the present invention, and equivalent changes or substitutions made on the basis of the above technical solutions all fall within the protection scope of the claims of the present invention.

Claims

1. A real-time quantitative analysis method for continuous casting tundish plug rod head blockage based on steel flow, characterized in that: The method comprises the following steps: Step 1: Determine the linear relationship between the stopper rod depth and the theoretical cross-sectional area. The linear relationship between the stopper rod depth and the theoretical cross-sectional area is given based on the qualitative dimensions of the stopper rod head and the upper nozzle. Step 2: Determine the theoretical cross-sectional area. During the pouring process, the theoretical cross-sectional area depends on the stopper rod depth. The theoretical cross-sectional area can be obtained by simply determining the actual stopper rod depth. To this end, based on the L1 real-time stopper rod depth and the aforementioned linear relationship between the stopper rod depth and the theoretical cross-sectional area, the theoretical cross-sectional area between the stopper rod head and the upper water inlet at the stopper rod depth is determined. Step 3: Determine the actual volume flow rate of the molten steel from the tundish into the crystallizer. After the pouring state is stable, the molten steel satisfies the continuity equation on the entire continuous casting machine. The volume flow rate of the molten steel in the crystallizer is the product of the cross-sectional size of the crystallizer and the continuous casting speed. Therefore, the volume flow rate of the molten steel at the stopper head can be expressed as: Q A =S s v s (3) In the formula, S s is the cross-sectional area of ​​the crystallizer, m 2 ;v s is the continuous casting speed, m / min. Therefore, based on the L1 real-time mold cross-sectional dimensions and the continuous casting speed, the actual volume flow rate of the tundish molten steel entering the crystallizer is determined according to formula (3): Step 4: Determine the actual flow rate of the stopper head steel flow, assuming that the flow rate of the molten steel in the vertical direction of the tundish surface is 0m / s, and take the stopper head as the calculation reference surface. At the same time, the energy change in the process of the molten steel in the tundish entering the crystallizer is the conversion of potential energy into kinetic energy and pressure loss. Where H is the depth of the tundish liquid level, m; g is the acceleration of gravity, m / s 2 ξ is the steel flow resistance coefficient. After moving the items, the actual flow velocity of the plug head steel flow can be expressed as: Based on the real-time tundish liquid level depth L1, the actual flow rate of the stopper head steel flow is determined according to formula (5): Step 5: Determine the actual cross-sectional area. As mentioned above, according to formula (2), at a certain stopper rod depth, the actual cross-sectional area can be expressed as the ratio of the actual volume flow rate of the molten steel to the actual flow rate of the molten steel at the stopper rod, Based on the actual volume flow rate of the tundish steel liquid entering the crystallizer in step 3 and the actual flow rate of the stopper head steel flow in step 4, the actual cross-sectional area is determined according to formula (3): Step 6: Determine the plugging rate of the plugging rod head. Based on the theoretical cross-sectional area of ​​step 2 and the actual cross-sectional area of ​​step 5, determine the real-time plugging rate of the plugging rod head according to formula (1).

2. The real-time quantitative analysis method for tundish plug rod head blockage based on steel flow rate continuous casting according to claim 1 is characterized in that: In the method, The plugging of the stopper head causes a difference between the theoretical cross-sectional area and the actual cross-sectional area at a certain stopper depth. The plugging rate of the stopper head of the continuous casting tundish is defined as: Where, η is the plugging rate of the tundish plug; S A is the actual cross-sectional area; S T It is the size of the theoretical cross-sectional area. If the actual cross-sectional area at a certain depth is equal to the theoretical cross-sectional area, the plugging rate of the tundish plug rod head is 0, indicating that the plug rod head is not blocked at this time; if the actual cross-sectional area at a certain depth is 0, the plugging rate of the tundish plug rod head is 1, indicating that the plug rod head is completely blocked at this time; According to formula (1), the plugging rate of the stopper rod can be obtained by simply obtaining the theoretical cross-sectional area and the actual cross-sectional area at a certain stopper rod depth. There is a one-to-one linear relationship between the theoretical cross-sectional area and the stopper rod depth, and this linear relationship is only related to the size of the stopper rod and the upper water inlet. At the same time, the actual volume flow rate of the molten steel from the tundish entering the crystallizer during pouring is the product of the steel flow rate at the stopper rod and the actual cross-sectional area, as shown in formula (2). Q A =S A ·v (2) In the formula, Q A is the actual volume flow rate entering the crystallizer, m 3 / min; v is the steel flow velocity passing through the plug head, m / min.

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