Component prediction method and device for continuous casting mixed pouring molten steel

Abstract

The invention discloses a component prediction method and device for continuous casting mixed pouring molten steel, and the method specifically comprises the following steps: (1) collecting the mass concentration CA of a target element in molten steel of a first steel grade and the mass concentration CB of the target element in molten steel of a second steel grade, and producing the first steel grade before the second steel grade; and (2) the inflow weight rate V < inflow > or outflow weight rate V < outflow > of the tundish in the continuous casting steady state and the weight S of molten steel in the tundish are determined, and the mass concentration of the target element in the continuous casting mixed casting molten steel in the tundish at different casting time is predicted. By constructing the relation model of the target components in the continuous casting mixed casting molten steel and the mixed casting time, the components of the target elements in the continuous casting mixed casting molten steel at any time in the mixed casting process of any steel grade can be determined on line on the basis of molten steel parameters of steel grades produced in advance and later and continuous casting steady-state parameters of a tundish, and sample cutting and component testing are not needed.

Description

Technical Field

[0001] The present invention belongs to the technical field of continuous casting, and more specifically, to a composition prediction method and device for continuous casting mixed casting molten steel. Background Art

[0002] At present, there is an oversupply of steel production capacity, and the industry competition is increasingly fierce. The demands of downstream processing enterprises are becoming more and more diversified, showing the characteristics of small quantity and many specifications. In order to adapt to the market situation, steel enterprises often adopt the method of continuous mixed casting of different steel grades for production, so as to accelerate energy conservation and cost reduction and improve quality and efficiency.

[0003] There are two ways to continuously mix different steel grades: 1. Direct continuous pouring for steel grades with little difference in composition; 2. Low liquid level continuous pouring for steel grades with certain difference in composition. After mixed pouring, the mixed casting part of the ingot is in a non-steady state, and its chemical composition changes dynamically. Therefore, how to determine the composition of the mixed casting part corresponding to the ingot is a difficult problem.

[0004] The current effective method is to cut samples for component testing after the mixed ingot has finished slow cooling off the production line, and only after confirming that it meets the standards can rolling be arranged. The above method will affect the rhythm of steel rolling production and cause inventory turnover pressure on ingots. Summary of the invention

[0005] The present invention provides a composition prediction method for continuous casting mixed pouring molten steel, aiming to improve the above-mentioned problem.

[0006] The present invention is achieved by providing a method for predicting the composition of continuous casting mixed steel liquid, the method being specifically as follows:

[0007] (1) Collect the mass concentration C of the target element in the first steel grade molten steel A , mass concentration C in the second steel grade molten steel B , the first steel grade is produced before the second steel grade;

[0008] (2) Determine the inflow weight rate V of the tundish during the continuous casting steady state 流入 Or outflow weight rate V 流出 , and the weight of molten steel in the tundish S, predict the mass concentration of the target element in the continuous casting mixed-casting molten steel in the tundish at different pouring times.

[0009] Furthermore, the prediction model of the mass concentration of the target element in the mixed steel liquid in the tundish under different pouring times is as follows:

[0010]

[0011] Among them, N and M are constants, t is the mixing time, C Bis the mass concentration of the target element in the molten steel corresponding to the later produced steel grade, C is the mass concentration of the target element in the continuous casting mixed steel in the tundish; S is the weight of the molten steel in the tundish during the continuous casting steady state, V 流入 is the weight rate of molten steel flowing into the tundish, V 流出 It is the weight rate of molten steel flowing into the tundish.

[0012] Furthermore, in the direct mixing mode, the constant N = C A -C B .

[0013] Furthermore, under the condition of falling liquid level mixing, the constant Wherein, H is the height of the tundish and h is the height of the liquid level after the liquid level drops.

[0014] The present invention is achieved by providing a composition prediction device for continuous casting mixed pouring molten steel, the device comprising:

[0015] An input unit, a processing unit and an output unit connected in sequence, wherein the processor is integrated with a composition prediction model of continuous casting mixed casting molten steel in a lowering liquid level mixed casting mode and a direct mixed casting mode;

[0016] The input unit is used to input relevant parameters in the lowering liquid level mixing mode or the direct mixing mode and transmit them to the processor. The processor calculates the mass concentration of the target element in the continuous casting mixed casting steel liquid in the tundish at the same pouring time and outputs it through the output unit.

[0017] Furthermore, the composition prediction model of the continuous casting mixed casting molten steel in the direct mixed casting mode is as follows:

[0018]

[0019] Among them, N and M are constants, and N=C A -C B , t is the mixing time, C B is the mass concentration of the target element in the molten steel corresponding to the second steel grade, and C is the mass concentration of the target element in the continuous casting mixed steel in the tundish;

[0020]

[0021] Among them, S is the weight of molten steel in the tundish during continuous casting steady state, V 流入 is the weight rate of molten steel flowing into the tundish, V 流出 The weight rate of molten steel flowing into the tundish, the first steel grade is produced before the second steel grade.

[0022] Furthermore, in the direct mixing mode, the relevant parameters entered by the input unit include: the mass concentration C of the first steel grade in the molten steel A , mass concentration C in the second steel grade molten steelB , the inflow weight rate V of the tundish during the continuous casting steady state 流入 Or outflow weight rate V 流出 , and the weight S of molten steel in the ladle.

[0023] Furthermore, the composition prediction model of the continuous casting mixed pouring molten steel in the falling liquid level mixed pouring mode is as follows:

[0024]

[0025] Among them, N and M are constants. t is the mixing time, C B is the mass concentration of the target element in the molten steel corresponding to the second steel grade, and C is the mass concentration of the target element in the continuous casting mixed steel in the tundish;

[0026]

[0027] Among them, S is the weight of molten steel in the tundish during continuous casting steady state, V 流入 is the weight rate of molten steel flowing into the tundish, V 流出 It is the weight rate of molten steel flowing into the tundish.

[0028] Furthermore, in the mixed pouring mode with falling liquid level, the relevant parameters entered by the input unit include: the mass concentration C of the target element in the first steel grade molten steel A , mass concentration C in the second steel grade molten steel B , the inflow weight rate V of the tundish during the continuous casting steady state 流入 Or outflow weight rate V 流出 , the weight S of the molten steel in the tundish and the liquid level h after the liquid level is lowered.

[0029] The present invention constructs a relationship model between the target composition in the continuous casting mixed casting molten steel and the mixing time. Based on the molten steel parameters of the previously produced and subsequently produced steel grades and the continuous casting steady-state parameters of the tundish, the composition of the target elements in the continuous casting mixed casting molten steel at any time during the mixing casting process of any steel grade can be determined online without cutting samples for composition testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of inflow and outflow of the tundish in the steady state of continuous casting proposed by the present invention;

[0031] Figure 2 A schematic structural diagram of a composition prediction device for continuous casting mixed pouring molten steel provided in an embodiment of the present invention. Implementation

[0033] The specific implementation modes of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0034] The high-temperature molten steel coming out of the steelmaking furnace (such as converter or electric furnace) first flows into the ladle, and the flow is controlled by the sliding nozzle or stopper rod of the ladle, and the molten steel is injected into the tundish. The main function of the ladle is to store molten steel and control the flow and pressure of the molten steel by sliding nozzle or stopper rod to ensure the stability of the continuous casting process. The continuous casting tundish is a transitional equipment connecting the ladle and the crystallizer, which distributes the molten steel from the ladle to the crystallizer.

[0035] The present invention constructs a relationship model between the target component and the mixing time in the continuous casting mixed steel liquid, and based on the molten steel parameters of the first and second steel grades produced and the continuous casting steady-state parameters of the tundish, can online determine the composition of the target element in the continuous casting mixed steel liquid at any time during the mixing process of any steel grade. Figure 1 The construction process of the composition prediction model for continuous casting mixed steel liquid is explained:

[0036] The weight of molten steel flowing from the ladle to the tundish during continuous casting is ΔS 流入 At the same time, the weight of molten steel flowing from the tundish to the crystallizer is ΔS 流出 When the two types of molten steel are mixed, the mass concentration of the target element in the ladle is C B , the mass concentration of the target element in the tundish is C, and C is a function of the mixing time t. In order to simplify the model, the following assumptions are made: after the molten steel flows from the large ladle into the medium ladle, it immediately undergoes sufficient convection and diffusion, and the inflowing molten steel is evenly mixed with the molten steel in the tundish. Secondly, the molten steel in the tundish can be fully mixed at any time, that is, the composition of the molten steel in the tundish is uniform at the same time.

[0037] First produce the first steel grade, and then produce the second steel grade by continuous mixing. The target element mass concentration in the molten steel corresponding to the first steel grade is C A The target element mass concentration in the molten steel corresponding to the second steel grade is C B According to the law of conservation of matter, the instantaneous increment ΔC of the mass concentration C of the target element in the tundish satisfies:

[0038] ΔC*S=C B *V 流入 *Δt-C*V 流出 *Δt (1)

[0039] Among them, S is the weight of molten steel in the tundish during continuous casting steady state, C B is the mass concentration of the target element in the molten steel corresponding to the later produced steel grade (second steel grade), V 流入is the weight rate of molten steel flowing into the tundish, C is the mass concentration of the target element in the tundish during mixed pouring, V 流出 is the weight rate of molten steel flowing into the tundish, and Δt is the time differential.

[0040] After differentiating formula (1), we get:

[0041] dC*S=C B *V 流入 *dt-C*V 流出 *dt (2)

[0042] The differential equation is:

[0043]

[0044] In the steady state of continuous casting, S, V 流入 、V 流出 , C B They are all fixed values, regarded as constants, let:

[0045]

[0046] Then the general solution of the equation is:

[0047]

[0048] Among them, N is a constant, t is the mixing time, and the constant N is calculated through the initial state.

[0049] For the first case: the concentration of components in the previous and next steel grades is not much different. After the continuous casting of the previous steel grade is completed, the molten steel of the next steel grade is directly input into the tundish for continuous casting of the next steel grade. This is called direct mixed casting. For the case of direct mixed casting, the composition prediction method of the continuous casting mixed casting billet is as follows:

[0050] (1) Collect the mass concentration C of the target element in the first steel grade molten steel A , mass concentration C in the second steel grade molten steel B ;

[0051] (2) Determine the inflow weight rate V of the tundish during the continuous casting steady state 流入 Or outflow weight rate V 流出 , and the weight of molten steel in the tundish S, based on formula (4) and formula (5), the mass concentration of the target element in the continuous casting mixed casting molten steel in the tundish at different pouring times is predicted.

[0052] The initial state refers to the moment when the molten steel of the later produced steel grade enters the tundish. The initial state corresponds to the mixing time t = 0. At this time, the mass concentration of the target element in the tundish is C 0 , C 0 =C B+N, at this time, the molten steel of the later produced steel grade entering the tundish is not mixed with the molten steel in the tundish, and the target element mass concentration of the molten steel in the tundish is the target element mass concentration C in the molten steel of the previous produced steel grade A , therefore, N = C A -C B .

[0053] Direct mixing: The mass concentration of the target element Si in the first steel grade is 0.25%, i.e. C A =0.25%; the mass concentration of the target element Si in the second steel grade: 1.752%, i.e. C B =1.752%;

[0054] Initial parameter setting: continuous casting section: radius r = 150mm, continuous casting speed V 拉速 =0.75m / min, molten steel density ρ = 7.8t / m 3 ; Number of continuous casting strands in tundish L = 6 strands; Tundish load S = 26t, when continuous casting is in steady state:

[0055] V 流入 =V 流出 =Lπr 2 ρV 拉速 ≈2.5t / min;

[0056]

[0057] When t = 0, N = C A -C B =0.25%-1.752%=-1.502%;

[0058] The calculation model of the mass concentration of the target element in the mixed steel liquid in the tundish under different pouring times is as follows:

[0059]

[0060] According to the sample composition, the above model is verified and the overall error of the model is less than 5%, which is small, as shown in Table 1.

[0061] Table 1 Error comparison between cut sample composition and model predicted composition in direct mixing mode

[0062]

[0063]

[0064] For the second case: there is a certain difference in the concentration of components in the previous and next steel grades. After the continuous casting of the previous steel grade is completed, the liquid level of the tundish is first lowered, and then the molten steel of the next steel grade is directly input into the tundish to fill it up, and then the next steel grade is continuously cast. This is called lowering the liquid level and mixing. For the case of lowering the liquid level and mixing, the composition prediction method of the continuous casting mixed casting billet is as follows:

[0065] (1) Collect the mass concentration C of the target element in the first steel grade molten steel A , mass concentration C in the second steel grade molten steel B ;

[0066] (2) Determine the inflow weight rate V of the tundish during the continuous casting steady state 流入 Or outflow weight rate V 流出 , the weight of molten steel in the tundish S and the height of the liquid level after the liquid level is lowered h, based on formula (4) and formula (5), the mass concentration of the target element in the continuous casting mixed casting steel liquid in the tundish at different pouring times is predicted.

[0067] The mixing time corresponding to the initial state is t = 0, ignoring the process from lowering the liquid level to filling the tundish in the initial stage. The mass concentration of the target element in the tundish is C 0 , Wherein, H is the height of the tundish.

[0068] Mixed pouring with lowered liquid level: given that the tundish height H = 900 mm, the liquid level height after lowering the liquid level h = 460 mm; ignoring the process of filling the tundish with molten steel in the initial stage of mixed pouring with lowered liquid level. The mass concentration of the target element Si in the first steel grade is 0.25%, i.e. C A =0.25%; the mass concentration of the target element Si in the second steel grade: 1.752%, i.e. C B =1.752%;

[0069] Initial parameter setting: continuous casting section: radius r = 150mm, continuous casting speed V 拉速 =0.75m / min, molten steel density ρ = 7.8t / m 3 ; Number of continuous casting strands in tundish L = 6 strands; Tundish load S = 26t, when continuous casting is in steady state:

[0070] V 流入 =V 流出 =Lπr 2 ρV 拉速 ≈2.5t / min;

[0071]

[0072] When t = 0, It can be seen that C 0=0.984%, N=-0.768%;

[0073] The calculation model of the mass concentration of the target element in the mixed steel liquid in the tundish under different pouring times is as follows:

[0074]

[0075] According to the sample composition, the model proposed by the present invention is verified, and the overall error of the model is less than 5%, which is relatively small, as shown in Table 2.

[0076] Table 2 Error comparison between the cut sample composition and the model predicted composition under the lowering liquid level mixing mode

[0077]

[0078]

[0079]

[0080] Figure 2 The schematic diagram of the structure of the composition prediction device for continuous casting mixed pouring molten steel provided by the embodiment of the present invention only shows the part related to the embodiment of the present invention for the convenience of explanation. The device comprises:

[0081] An input unit, a processing unit and an output unit connected in sequence, wherein the processor is integrated with a composition prediction model of continuous casting mixed casting molten steel in a lowering liquid level mixed casting mode and a direct mixed casting mode;

[0082] The input unit is used to input relevant parameters in the lowering liquid level mixing mode or the direct mixing mode and transmit them to the processor. The processor calculates the mass concentration of the target element in the continuous casting mixed casting steel liquid in the tundish at the same pouring time and outputs it through the output unit.

[0083] In the direct mixing mode, the relevant parameters entered by the input unit include: the mass concentration C of the first steel grade in molten steel; A , mass concentration C in the second steel grade molten steel B , the inflow weight rate V of the tundish during the continuous casting steady state 流入 Or outflow weight rate V 流出 , and the weight of molten steel in the ladle S, the composition prediction model of continuous casting mixed casting molten steel in direct mixed casting mode is as follows:

[0084]

[0085] Among them, N and M are constants, and N=C A -C B , t is the mixing time, C Bis the mass concentration of the target element in the molten steel corresponding to the later produced steel grade (the second steel grade), and C is the mass concentration of the target element in the continuous casting mixed steel liquid in the tundish;

[0086]

[0087] Among them, S is the weight of molten steel in the tundish during continuous casting steady state, V 流入 is the weight rate of molten steel flowing into the tundish, V 流出 It is the weight rate of molten steel flowing into the tundish.

[0088] In the embodiment of the present invention, the relevant parameters entered through the input unit in the falling liquid level mixed pouring mode include: the mass concentration C of the target element in the first steel grade molten steel; A , mass concentration C in the second steel grade molten steel B , the inflow weight rate V of the tundish during the continuous casting steady state 流入 Or outflow weight rate V 流出 , the weight of molten steel in the tundish S and the liquid level h after the liquid level is lowered, the composition prediction model of the continuous casting mixed pouring molten steel in the mixed pouring mode of lowering the liquid level is as follows:

[0089]

[0090] Among them, N and M are constants. t is the mixing time, C B is the mass concentration of the target element in the molten steel corresponding to the later produced steel grade (the second steel grade), and C is the mass concentration of the target element in the continuous casting mixed steel liquid in the tundish;

[0091]

[0092] Among them, S is the weight of molten steel in the tundish during continuous casting steady state, V 流入 is the weight rate of molten steel flowing into the tundish, V 流出 It is the weight rate of molten steel flowing into the tundish.

[0093] By constructing a relationship model between the target composition in the continuous casting mixed casting molten steel and the mixing time, based on the molten steel parameters of the first and second produced steel grades and the continuous casting steady-state parameters of the tundish, the composition of the target elements in the continuous casting mixed casting molten steel at any time during the mixing process of any steel grade can be determined online.

[0094] The present invention has been described exemplarily. Obviously, the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for predicting the composition of continuous casting mixed steel liquid, characterized in that: The method is specifically as follows: (1) Collect the mass concentration C of the target element in the first steel grade molten steel A , mass concentration C in the second steel grade molten steel B , the first steel grade is produced before the second steel grade; (2) Determine the inflow weight rate V of the tundish during the steady state of continuous casting 流入 Or outflow weight rate V 流出 , and the weight of molten steel in the tundish S, predict the mass concentration of the target element in the continuous casting mixed-casting molten steel in the tundish at different pouring times.

2. The composition prediction method of continuous casting mixed pouring molten steel according to claim 1, characterized in that: The prediction model of the mass concentration of target elements in the mixed steel liquid in the tundish under different pouring times is as follows: Among them, N and M are constants, t is the mixing time, C B is the mass concentration of the target element in the molten steel corresponding to the later produced steel grade, C is the mass concentration of the target element in the continuous casting mixed steel in the tundish; S is the weight of the molten steel in the tundish during the continuous casting steady state, V 流入 is the weight rate of molten steel flowing into the tundish, V 流出 It is the weight rate of molten steel flowing into the tundish.

3. The composition prediction method of continuous casting mixed pouring molten steel according to claim 2, characterized in that: In direct mixing mode, the constant N = C A -C B .

4. The composition prediction method of continuous casting mixed pouring molten steel according to claim 2, characterized in that: Under the condition of falling liquid level mixing, constant Wherein, H is the height of the tundish and h is the height of the liquid level after the liquid level drops.

5. A composition prediction device for continuous casting mixed pouring molten steel, characterized in that: The device comprises: An input unit, a processing unit and an output unit connected in sequence, wherein the processor is integrated with a composition prediction model of continuous casting mixed casting molten steel in a lowering liquid level mixed casting mode and a direct mixed casting mode; The input unit is used to input relevant parameters in the lowering liquid level mixing mode or the direct mixing mode and transmit them to the processor. The processor calculates the mass concentration of the target element in the continuous casting mixed casting steel liquid in the tundish at the same pouring time and outputs it through the output unit.

6. The composition prediction device for continuous casting mixed pouring molten steel according to claim 5, characterized in that: The composition prediction model of continuous casting mixed casting molten steel in direct mixed casting mode is as follows: Among them, N and M are constants, and N=C A -C B , t is the mixing time, C B is the mass concentration of the target element in the molten steel corresponding to the second steel grade, and C is the mass concentration of the target element in the continuous casting mixed steel in the tundish; Among them, S is the weight of molten steel in the tundish during continuous casting steady state, V 流入 is the weight rate of molten steel flowing into the tundish, V 流出 The weight rate of molten steel flowing into the tundish, the first steel grade is produced before the second steel grade.

7. The composition prediction device for continuous casting mixed pouring molten steel according to claim 6, characterized in that: In the direct mixing mode, the relevant parameters entered by the input unit include: the mass concentration of the first steel grade in molten steel C A , mass concentration C in the second steel grade molten steel B , the inflow weight rate V of the tundish during the continuous casting steady state 流入 Or outflow weight rate V 流出 , and the weight S of the molten steel in the ladle.

8. The composition prediction device for continuous casting mixed pouring molten steel according to claim 5, characterized in that: The composition prediction model of continuous casting mixed pouring molten steel in the falling liquid level mixed pouring mode is as follows: Among them, N and M are constants. t is the mixing time, C B is the mass concentration of the target element in the molten steel corresponding to the second steel grade, and C is the mass concentration of the target element in the continuous casting mixed steel in the tundish; Among them, S is the weight of molten steel in the tundish during continuous casting steady state, V 流入 is the weight rate of molten steel flowing into the tundish, V 流出 It is the weight rate of molten steel flowing into the tundish.

9. The composition prediction device for continuous casting mixed pouring molten steel according to claim 8, characterized in that: In the falling liquid level mixed pouring mode, the relevant parameters entered by the input unit include: the mass concentration of the target element in the first steel grade molten steel C A , mass concentration C in the second steel grade molten steel B , the inflow weight rate V of the tundish during the continuous casting steady state 流入 Or outflow weight rate V 流出 , the weight S of the molten steel in the tundish and the liquid level h after the liquid level is lowered.

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