Intelligent slag line replacing method for submersed nozzle

Abstract

The invention relates to a method for intelligently replacing a slag line of a submersed nozzle, which comprises the following steps of: driving the height of a molten steel casting powder liquid slag layer of a crystallizer to generate non-sine curve change through the non-sine curve change of the molten steel liquid level height of the crystallizer, and replacing the submersed nozzle when the actual value of the molten steel liquid level height of the crystallizer enters a back vibration state. According to the method, the non-sine curve change of the molten steel covering slag layer height of the crystallizer is controlled by controlling the non-sine curve change of the molten steel liquid level height of the crystallizer, the molten steel liquid level of the crystallizer is very stable when the submersed nozzle slag line is replaced, and the service life of the submersed nozzle is prolonged; and automatic, intelligent and unmanned operation of the whole slag line replacement process is realized.

Description

Technical Field

[0001] The invention relates to the technical field of steelmaking, and in particular to a method for intelligently replacing a slag line of an immersed nozzle. Background Art

[0002] The submerged nozzle is a refractory sleeve for casting that is installed at the bottom of the intermediate tank in the continuous steel casting equipment and inserted below the molten steel level of the crystallizer. The outlet of the submerged nozzle is immersed in the molten steel in the crystallizer, which prevents the secondary oxidation of the molten steel, controls the flow rate of the molten steel when it enters the crystallizer, is conducive to the floating of inclusions in the molten steel, and can effectively prevent the occurrence of slag rolling, etc., ensuring the stable operation of the continuous casting process.

[0003] The submerged nozzle is a key refractory material in the process of continuous casting steel pouring process control. It is one of the very important refractory materials for smooth production, cost reduction, efficiency improvement and stable quality control of the continuous casting process in steel mills in the metallurgical industry.

[0004] In order to improve the service life of the submerged nozzle, the zirconia layer of the slag line of the submerged nozzle must be fully utilized. In order to make the best use of the zirconia layer of the slag line of the submerged nozzle, it is generally achieved by changing the position of the slag line several times during the casting process. Under normal circumstances, each steel plant uses the method of manually adjusting the crystallizer liquid level at regular intervals or lifting the tundish car to change the slag line position of the submerged nozzle. However, in the process of manually adjusting the crystallizer liquid level or lifting the tundish car, it is inevitable that the crystallizer liquid level will fluctuate greatly. When the crystallizer liquid level fluctuates greatly, the protective slag in the crystallizer will be drawn into the molten steel, forming slag inclusions or inclusion defects in the ingot. When the ingot is rolled through the hot rolling and cold rolling processes, inclusions or slag inclusions will appear on the hot rolled or cold rolled plate (coil) products, affecting the performance of the end user. In severe cases, it may cause product degradation or even scrapping, ultimately affecting the company's product image and economic benefits.

[0005] CN 101229576 B discloses a continuous casting crystallizer slag line control method. On the basis of the existing continuous casting crystallizer liquid level automatic control system, the slag layer position is adjusted by continuously and automatically changing the system setting value in a slight amount over time, so that the submerged nozzle can be more continuously, smoothly and evenly flushed in the expected form, extending the service life of the submerged nozzle, and solving a series of problems caused by uneven flushing caused by manual setting and slag strip processing. The prior art slag layer moves along the set curve with different slopes to change the form of the submerged nozzle flushing, but the thinnest part of the submerged nozzle needs to be increased.

[0006] Based on this, there is room for improvement in mold level control. Summary of the invention

[0007] In view of this, an object of the present invention is to provide a method for intelligently replacing the slag line of an submerged nozzle, so as to solve the technical problem of slag inclusion or inclusion defects in the casting billet caused by large fluctuations in the liquid level of the crystallizer during the replacement of the slag line of the submerged nozzle.

[0008] In order to achieve the above object, the technical solution provided by the present invention is: A method for intelligently replacing a slag line for an immersed nozzle drives a non-sinusoidal change in the height of a molten steel protective slag layer in the crystallizer through a non-sinusoidal change in the height of a molten steel liquid level in the crystallizer, and replaces the immersed nozzle when the actual value of the molten steel liquid level in the crystallizer enters a re-oscillation state.

[0009] In some embodiments, the method for intelligent slag replacement line of submerged nozzle includes the following steps: Step 1: Set the reference point for the height control of the molten steel level in the crystallizer; Step 2: Detect the height of the molten steel level in the crystallizer, and dynamically adjust the height of the molten steel level in the crystallizer in a non-sinusoidal curve manner with the reference point of the molten steel level control height in the crystallizer as the starting point; Step 3: When the actual value of the crystallizer molten steel level enters a re-vibration state, replace the submerged nozzle; Step 4: After replacing the new immersion nozzle, repeat steps 1 to 3.

[0010] In some embodiments, the method for an intelligent slag changing line for an immersed nozzle includes establishing an intelligent control model of a crystallizer liquid level, in which a reference point for controlling the crystallizer molten steel level is set, non-sinusoidal curve model parameters are set, and PLC model parameters are set.

[0011] In some embodiments, the non-sinusoidal curve model parameters include the non-sinusoidal function corresponding to the non-sinusoidal curve and the dependent variable and causal value of the non-sinusoidal function. The dependent variable of the non-sinusoidal function is the immersion nozzle casting time, and the causal value is the crystallizer molten steel level control height value.

[0012] In some embodiments, the non-sinusoidal function is: y=30sin(X)-110, where y is the controlled height value of the molten steel level in the crystallizer, y ranges from -110mm to -80mm, and X is the degree associated with the immersion nozzle casting time, and X ranges from 0° to 90°.

[0013] In some embodiments, X=360×(m / S), where m is the timely time value of the immersion nozzle casting time, the value range of m is 0 to the immersion nozzle casting time, S is the period of the non-sinusoidal function, and the value of S is four times the immersion nozzle casting time.

[0014] In some embodiments, the reference point of the controlled height of the molten steel level in the crystallizer corresponds to the causal value corresponding to the zero point of the non-sinusoidal function.

[0015] In some embodiments, the non-sinusoidal curve model parameters include the amplitude and period of the non-sinusoidal function corresponding to the non-sinusoidal curve. The amplitude of the non-sinusoidal function is set to the difference between the actual value of the crystallizer molten steel level height corresponding to the reference point of the crystallizer molten steel level control height and the actual value of the crystallizer molten steel level height corresponding to the maximum value of the crystallizer molten steel level control height. The period of the non-sinusoidal function corresponds to the amplitude period of an up and down reciprocating cyclic vibration of the non-sinusoidal curve.

[0016] In some embodiments, the PLC model parameters include height parameters set in the PLC for controlling the change in the height of the molten steel level in the crystallizer.

[0017] In some embodiments, the PLC model parameters include non-sinusoidal setting parameters, which are combined with non-sinusoidal functions of non-sinusoidal curve model parameters and cooperate with height parameters to control the crystallizer molten steel level to change in a non-sinusoidal manner.

[0018] The beneficial effects of the present invention are: The method for intelligently replacing the slag line of an immersed nozzle of the present invention controls the non-sinusoidal change of the height of the molten steel protective slag liquid slag layer of the crystallizer by controlling the non-sinusoidal change of the liquid level height of the molten steel in the crystallizer. When the slag line of the immersed nozzle is replaced, the molten steel level of the crystallizer is very stable, which not only improves the service life of the immersed nozzle, but also ensures the product quality. At the same time, no manual intervention is required, which not only reduces the intensity of manual labor, but also realizes the automation, intelligence and unmanned operation of the entire slag line replacement process. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with specific embodiments.

[0020] It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are for distinguishing two non-identical entities with the same name or non-identical parameters. It can be seen that "first" and "second" are only for the convenience of expression and should not be understood as limitations on the embodiments of the present invention. The subsequent embodiments will not explain this one by one.

[0021] The slag line refers to the part of the submerged nozzle that contacts the protective slag layer in the crystallizer. In fact, the slag line is the position of the protective slag layer in the crystallizer, and the position of the protective slag layer changes with the height of the molten steel level in the crystallizer.

[0022] The method for intelligently replacing slag lines for submerged nozzles of the present invention drives the height of the molten steel protection slag layer of the crystallizer to change in a non-sinusoidal curve through the non-sinusoidal curve change of the crystallizer molten steel liquid level, and replaces the submerged nozzle when the actual value of the crystallizer molten steel liquid level enters a re-vibration state. The method comprises the following steps: Step 1: Set the reference point for the height control of the molten steel level in the crystallizer; Step 2: Detect the height of the molten steel level in the crystallizer, and dynamically, continuously and smoothly adjust the height of the molten steel level in the crystallizer in a non-sinusoidal curve manner with the reference point of the molten steel level control height as the starting point; Step 3: When the actual value of the crystallizer molten steel level enters a re-vibration state, replace the submerged nozzle; Step 4: After replacing the new immersion nozzle, repeat steps 1 to 3.

[0023] According to the method for intelligently replacing the slag line of an immersed nozzle of the present invention, during the adjustment process of the liquid level of molten steel in the crystallizer, the liquid level of molten steel in the crystallizer can be raised or lowered continuously, smoothly and seamlessly, and the actual erosion of the position of the slag line of the immersed nozzle by the crystallizer protective slag will also synchronously present a trend of continuous, smooth and seamless connection, thereby reducing the fluctuation amplitude of the molten steel level in the crystallizer and preventing the problem of molten steel slag rolling.

[0024] Compared with the prior art, the method of intelligent slag line replacement of submerged nozzles of the present invention controls the change of the height of the molten steel level in the crystallizer in a non-sinusoidal manner and replaces the submerged nozzle when the actual value of the molten steel level in the crystallizer is about to reach the maximum height. During the entire submerged nozzle slag line replacement process, the molten steel level in the crystallizer is very stable, effectively avoiding the problem of large fluctuations in the molten steel level in the crystallizer caused by the sudden change of the step-by-step height used in the manual slag replacement line, causing molten steel slag rolling, and ultimately affecting product quality.

[0025] In some embodiments, the method for intelligent slag changing line of submerged nozzle includes establishing a crystallizer liquid level intelligent control model. In the crystallizer liquid level intelligent control model, a reference point of the crystallizer molten steel level control height is set, a non-sinusoidal curve model parameter is set, and a PLC model parameter is set.

[0026] In some embodiments, the reference point for controlling the height of the molten steel level in the crystallizer is the height of the molten steel level in the crystallizer corresponding to the lowest position of the slag line of the submerged nozzle.

[0027] Since the non-sinusoidal curve has an up and down reciprocating cyclic amplitude cycle, in order to avoid repeated back-and-forth erosion of the middle part of the submerged nozzle corresponding to the up and down reciprocating highest point and lowest point of the molten steel level in the crystallizer, the amplitude cycle of the non-sinusoidal curve is set to four times the casting time of an submerged nozzle in the crystallizer liquid level intelligent control model.

[0028] In some embodiments, the actual value of the crystallizer molten steel level height entering the re-oscillation state refers to the state when the actual value of the crystallizer molten steel level height reaches the maximum value of the crystallizer molten steel level control height and the crystallizer molten steel level begins to drop back. When the crystallizer molten steel level drops back, the submerged nozzle may be repeatedly eroded. In order to evenly erode the slag line of an submerged nozzle once to increase the life of the entire submerged nozzle, when the actual value of the crystallizer molten steel level height reaches the maximum value of the crystallizer molten steel level control height, a new submerged nozzle needs to be replaced. The actual value of the crystallizer molten steel level height equal to the maximum value of the crystallizer molten steel level control height can be used as a basis for judging whether the actual value of the crystallizer molten steel level height enters the re-oscillation state.

[0029] In some embodiments, the non-sinusoidal curve model parameters include the non-sinusoidal function corresponding to the non-sinusoidal curve and the dependent variable and causal value of the non-sinusoidal function, the dependent variable of the non-sinusoidal function is the immersion nozzle casting time t, the causal value is the crystallizer molten steel level control height value y, and the immersion nozzle casting time t is one quarter of the period of the non-sinusoidal function. The non-sinusoidal curve method can avoid the erosion time of the lower part of the immersion nozzle being too long.

[0030] In some embodiments, the immersion nozzle casting time t is controlled to be 360 ​​min to 380 min, and the crystallizer molten steel liquid level control height value y is controlled to be -110 mm to -80 mm.

[0031] In some embodiments, the non-sinusoidal function is: y=30sin(X)-110, where y is the controlled height value of the molten steel level in the crystallizer, y ranges from -110mm to -80mm, and X is the degree associated with the immersion nozzle casting time t, and X ranges from 0° to 90°.

[0032] In some embodiments, X=360×(m / S), where m is the appropriate time value of the immersion nozzle casting time t, the value range of m is 0 to the immersion nozzle casting time t, and S is the period of the non-sinusoidal function, and the value of S is 4t. That is, the period S of the non-sinusoidal function is set to four times the immersion nozzle casting time t.

[0033] In some embodiments, the reference point of the controlled height of the molten steel level in the crystallizer corresponds to the causal value corresponding to the zero point of the non-sinusoidal function.

[0034] In some embodiments, the non-sinusoidal curve model parameters include the amplitude and period S of the non-sinusoidal function corresponding to the non-sinusoidal curve, and the amplitude of the non-sinusoidal function is set as the difference between the actual value of the crystallizer molten steel liquid level corresponding to the reference point of the crystallizer molten steel liquid level control height and the actual value of the crystallizer molten steel liquid level corresponding to the maximum value of the crystallizer molten steel liquid level control height. The period S of the non-sinusoidal function corresponds to the amplitude period of an up and down reciprocating cycle of the non-sinusoidal curve.

[0035] In some embodiments, the PLC model parameters include height parameters set in a PLC (Programmable Logic Controller) for controlling the height change of the molten steel level in the crystallizer.

[0036] In some embodiments, the actual value of the molten steel level in the crystallizer is the actual value of the molten steel level in the crystallizer detected by a sensor, and the actual value of the molten steel level in the crystallizer is transmitted to the PLC through the sensor and automatically analyzed in the PLC.

[0037] In some embodiments, the sensor is an electromagnetic sensor, and the electromagnetic sensor is installed on the crystallizer.

[0038] In some embodiments, the reference point of the crystallizer molten steel level control height is -110 mm. The height is taken as the zero point by the height position of the sensor installed on the crystallizer to detect the molten steel level height, downward is negative, and upward is positive.

[0039] In some embodiments, the PLC model parameters include non-sinusoidal setting parameters, which are combined with non-sinusoidal functions of non-sinusoidal curve model parameters and cooperate with height parameters to control the crystallizer molten steel level to change in a non-sinusoidal manner.

[0040] In some embodiments, the height of the molten steel level in the crystallizer is dynamically, continuously and smoothly adjusted in a non-sinusoidal manner with the reference point of the crystallizer molten steel level control height as the starting point, including: based on the actual value of the molten steel level in the crystallizer, the molten steel level in the crystallizer is controlled by PLC according to the PLC model parameters to change according to the non-sinusoidal model parameters. The change in the molten steel level in the crystallizer drives the change in the height position of the protective slag layer of the steel surface in the crystallizer, so as to change the position of the slag line of the submerged nozzle. The change in the molten steel level in the crystallizer is controlled by PLC according to the non-sinusoidal model parameters to achieve the purpose of intelligently replacing the slag line of the submerged nozzle.

[0041] The intelligent slag line replacement method for the submerged nozzle of the present invention is that the submerged nozzle slag line replacement is automatically carried out in a non-sinusoidal curve manner during the whole process from the start of pouring in the tundish to the end of casting, and no manual intervention is required. The slag line replacement process is smooth, and the molten steel level in the crystallizer is very stable, which not only eliminates the problem of molten steel slag rolling, but also improves product quality. The method has high practicality and promotion value in the technical control of continuous casting process in metallurgical systems.

[0042] Example 1 The submerged nozzle intelligent slag line replacement method is adopted on the 1930 continuous casting machine of the steelmaking plant of Xichang Steel and Vanadium Company of Panzhihua Iron and Steel Group. The 1930 continuous casting machine is a two-machine two-stream straight arc large slab continuous casting machine with a cross-section of 230×(1300~1930)mm, a billet length of 9000mm~11000mm, and a normal casting pulling speed of 0.8m / min~1.6m / min. The main casting steel types include: ultra-low carbon automotive steel series, oil pipeline steel, weather-resistant and acid-resistant steel, electrical steel, high-strength low-alloy steel, automotive structure steel, welding bottle steel, hot-formed steel, etc. First, the intelligent control model of the crystallizer liquid level is established, the reference point of the crystallizer molten steel level control height is set to -110mm, and the non-sinusoidal function is set to: y=30sin(X)-110, X=360×(m / S), where S is four times the immersion nozzle casting time t, and the immersion nozzle casting time t is set to 360min~380min according to the characteristics of the cast steel type, user quality requirements, production plan quantity, drawing speed, cross-section size, etc. The period S of the non-sinusoidal function is set to 1440min~1520min. Secondly, when the molten steel level of the new tundish is stable, the crystallizer molten steel level is positioned at -110mm, and then the crystallizer molten steel level control mode is set to automatic mode, and the crystallizer molten steel level is controlled by PLC to change in a non-sinusoidal curve. The non-sinusoidal curve method is used to control the height of the molten steel liquid level in the crystallizer, and the casting time t of the submerged nozzle is controlled to be one quarter of the period S of the non-sinusoidal function. When the actual value of the molten steel liquid level in the crystallizer reaches the maximum value of the controlled height of the molten steel liquid level in the crystallizer, the submerged nozzle is replaced, and the above process is repeated after replacing the new submerged nozzle. The surface erosion of the slag line of the replaced submerged nozzle is uniform and smooth. The molten steel liquid level in the crystallizer is very stable during the entire casting process, and no adverse phenomena such as fluctuation slag rolls occur.

[0043] Example 2 The submerged nozzle intelligent slag line replacement method is adopted on the 1650 continuous casting machine of the steelmaking plant of Xichang Steel and Vanadium Company of Panzhihua Iron and Steel Group. The 1650 continuous casting machine is a two-machine two-stream straight arc large slab continuous casting machine with a cross-section of 230×(950~1650)mm, a billet length of 9000mm~11000mm, and a normal casting pulling speed of 0.8m / min~1.6m / min. The main casting steel types include: ultra-low carbon automotive steel series, oil pipeline steel, weather-resistant and acid-resistant steel, electrical steel, high-strength low-alloy steel, automotive structure steel, welding bottle steel, hot-formed steel, etc. First, the intelligent control model of the crystallizer liquid level is established, the reference point of the crystallizer molten steel level control height is set to -110mm, and the non-sinusoidal function is set to: y=30sin(X)-110, X=360×(m / S), where S is four times the immersion nozzle casting time t, and the immersion nozzle casting time t is set to 360min~380min according to the characteristics of the cast steel type, user quality requirements, production plan quantity, drawing speed, cross-section size, etc. The period S of the non-sinusoidal function is set to 1440min~1520min. Secondly, when the molten steel level of the new tundish is stable, the crystallizer molten steel level is positioned at -110mm, and then the crystallizer molten steel level control mode is set to automatic mode, and the crystallizer molten steel level is controlled by PLC to change in a non-sinusoidal curve. The non-sinusoidal curve method is used to control the height of the molten steel liquid level in the crystallizer, and the casting time t of the submerged nozzle is controlled to be one quarter of the period S of the non-sinusoidal function. When the actual value of the molten steel liquid level in the crystallizer reaches the maximum value of the controlled height of the molten steel liquid level in the crystallizer, the submerged nozzle is replaced, and the above process is repeated after replacing the new submerged nozzle. The surface erosion of the slag line of the replaced submerged nozzle is uniform and smooth. The molten steel liquid level in the crystallizer is very stable during the entire casting process, and no adverse phenomena such as fluctuation slag rolls occur.

[0044] The intelligent slag line replacement method for the submerged nozzle extends the casting time of a single submerged nozzle from the original 240 minutes to 360 minutes to 380 minutes; it reduces the fluctuation of the molten steel level in the crystallizer caused by manual replacement of the slag line of the submerged nozzle; since the fluctuation of the molten steel level in the crystallizer is reduced, the protective slag in the crystallizer is prevented from being drawn into the molten steel, thereby improving the quality of the final product and reducing the economic loss of the product being downgraded and re-judged due to inclusion defects; it achieves that there will be no large fluctuation of the crystallizer liquid level during the replacement of the slag line of the submerged nozzle, which not only increases the service life of the submerged nozzle, but also ensures product quality; it realizes automated, unmanned and intelligent replacement of the submerged nozzle operation, reducing the labor intensity of the operator.

[0045] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0046] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for intelligently changing slag lines of submerged nozzles, characterized in that: The non-sinusoidal change of the crystallizer molten steel liquid level height drives the crystallizer molten steel protective slag liquid slag layer height to change non-sinusoidally, and the submerged nozzle is replaced when the actual value of the crystallizer molten steel liquid level height enters a re-vibration state.

2. The method for intelligent slag replacement line of submerged nozzle according to claim 1 is characterized in that: The following steps are involved: Step 1: Set the reference point for the height control of the molten steel level in the crystallizer; Step 2: Detecting the height of the molten steel liquid level in the crystallizer, and dynamically adjusting the height of the molten steel liquid level in the crystallizer in a non-sinusoidal curve manner with the reference point of the molten steel liquid level control height as the starting point; Step 3: When the actual value of the crystallizer molten steel level enters a re-vibration state, replace the submerged nozzle; Step 4: After replacing the new immersion nozzle, repeat steps 1 to 3.

3. The method for intelligent slag replacement line of submerged nozzle according to claim 2 is characterized in that: The invention comprises establishing a crystallizer liquid level intelligent control model, in which a reference point of the crystallizer molten steel liquid level control height is set, non-sinusoidal curve model parameters are set, and PLC model parameters are set.

4. The method for intelligent slag replacement line of submerged nozzle according to claim 3 is characterized in that: The non-sinusoidal curve model parameters include a non-sinusoidal function corresponding to the non-sinusoidal curve and a dependent variable and a causal value of the non-sinusoidal function. The dependent variable of the non-sinusoidal function is the immersion nozzle casting time, and the causal value is the crystallizer molten steel liquid level control height value.

5. The method for intelligent slag replacement line of submerged nozzle according to claim 4 is characterized in that: The non-sinusoidal function is: y=30sin(X)-110, wherein y is the controlled height value of the molten steel level in the crystallizer, and y ranges from -110mm to -80mm; X is the degree associated with the casting time of the immersion nozzle, and X ranges from 0° to 90°.

6. The method for intelligent slag replacement line of submerged nozzle according to claim 5, characterized in that: X=360×(m / S), where m is the timely time value of the immersion nozzle casting time, the value range of m is 0 to the immersion nozzle casting time, S is the period of the non-sinusoidal function, and the value of S is four times the immersion nozzle casting time.

7. The method for intelligent slag replacement line of submerged nozzle according to claim 5, characterized in that: The reference point of the crystallizer molten steel level control height corresponds to the causal value corresponding to the zero point of the non-sinusoidal function.

8. The method for intelligent slag replacement line of submerged nozzle according to claim 4, characterized in that: The non-sinusoidal curve model parameters include the amplitude and period of the non-sinusoidal function corresponding to the non-sinusoidal curve. The amplitude of the non-sinusoidal function is set to the difference between the actual value of the crystallizer molten steel level height corresponding to the reference point of the crystallizer molten steel level control height and the actual value of the crystallizer molten steel level height corresponding to the maximum value of the crystallizer molten steel level control height. The period of the non-sinusoidal function corresponds to the amplitude period of an up and down reciprocating cyclic vibration of the non-sinusoidal curve.

9. The method for intelligent slag replacement line of submerged nozzle according to claim 4, characterized in that: The PLC model parameters include height parameters set in the PLC for controlling the height change of the molten steel level in the crystallizer.

10. The method for intelligent slag replacement line of submerged nozzle according to claim 9, characterized in that: The PLC model parameters include non-sinusoidal setting parameters, which are combined with the non-sinusoidal functions of the non-sinusoidal curve model parameters and cooperate with the height parameters to control the height of the molten steel level in the crystallizer to change in a non-sinusoidal curve manner.