JPH01258857A - Method for deciding length of component mixture in continuous casting - Google Patents

Abstract

PURPOSE:To grasp with a favourable accuracy the behavior of component mixture in a cast slab by simulating the components mixture based on molten metal wt. in an intermediate vessel, drawing speed of the cast slab and component values in ladles at previous and the successive heats, etc. CONSTITUTION:At the time of supplying the molten metal in the successive heat having different component into the intermediate vessel 2 remaining the molten metal in the previous heat, the signals of the intermediate vessel wt. measuring instrument 3 and the cast slab drawing control device 7 are transmitted with the lapse of time to a process computer 11 and pouring speed into the intermediate vessel 2 and pouring speed into a mold 4 from the intermediate vessel 2 are continuously calculated. These results, the molten metal wt. in the intermediate vessel, the cast slab drawing speed, and the pre-given data are transmitted into a microcomputer 12 and the simulation of the component mixture is executed in accordance with the component mixing model. The length at position, where the component values in the cast slab is out of the component ranges in the molten metals at the previous and the successive heats, is decided to the component mixing length. This mixing length is transmitted to cast slab cutting device 8. By this method, the part of out of the component can be cut and separated from the good cast slab at the right length.

Description

[Detailed Description of the Invention] <Industrial Field of Application> The present invention relates to a method for determining the length of a cast slab that loses its composition when successively casting ladles of different molten metal compositions in continuous casting of molten metal. be.

<Conventional technology> When continuous casting is carried out with successive batches of different molten metal compositions, from the viewpoint of quality assurance of slabs and improvement of casting yield,
It is important to accurately determine the length of the slab that has lost its components and to minimize the length of the slab that is cut and separated from the good slab.

<Problems to be Solved by the Invention> In contrast, conventional methods uniformly cut and separate slabs of a certain length from good slabs at the ladle joint, regardless of the above-mentioned composition range or operating conditions. It was mainstream. In this case, it does not match the actual component mixing behavior, and there is a problem that components are removed in good slabs due to insufficient cutting separation length, and yield loss occurs due to excess cutting separation length.

For this reason, Japanese Patent Publication No. 61-16222 proposes a method of grasping the mixing length of the components from the weight of the molten metal in the intermediate vessel and the rate of withdrawal of the slab, but this method requires that the influence of mixing is determined in advance. The problem was that it was only considered as a constant, and furthermore, it did not take into account the one-dollar component difference before and after, so it could not be said to be accurate enough as a model to estimate the actual component mixing length. .

The present invention improves quality by accurately grasping the component mixing behavior of slabs and reliably cutting and separating areas where the components are out of proportion from good slabs when successively casting ladles with different compositions in continuous casting operations for molten metal. Our objective is to provide a method for determining the length of cut and separated slabs to improve yield by minimizing the length required for management and operational management.

Means for Solving the Problems〉 The present invention provides for the following:
When continuously casting post-charged molten metal with different compositions to the intermediate container, the weight of the molten metal in the intermediate container and the slab withdrawal speed are continuously measured and input into the process computer, and the input and the process computer are provided in advance. The injection speed from the ladle to the intermediate container and the injection speed from the intermediate container to the mold are continuously calculated based on the slab size and the injection speed from the intermediate container to the mold. Input the allowable range of components into a computer, perform a component mixing simulation based on the component mixing model using the computer, and calculate the length of the part where the slab component value in the simulation result deviates from the molten metal component range of the front and rear charges as the component mixing length. This is a method for determining a component mixing length in continuous casting, which is characterized by:

An example of the equipment arrangement used in the component mixing model according to the present invention is shown in FIG. In the figure, 1 is a dollar, 2 is an intermediate container, 3 is an intermediate container weight measuring device, 4 is a mold, 5 is a slab drawing roll, 6 is a driving motor for the drawing roll,
7 is a slab drawing motor control device, 8 is a slab cutting device, 9 is a molten metal, 10 is a slab, 11 is a process computer (hereinafter abbreviated as a pro-computer), and 12 is a microcomputer (hereinafter abbreviated as a microcomputer). be.

In the present invention, the injection speed from the ladle 1 to the intermediate container 2 and the injection speed from the intermediate container 2 to the mold 4 are continuously controlled in the program controller 11 by sequentially transmitting signals from the intermediate container weight measuring device 3 and the slab drawing motor control device 7. The microcomputer 1 calculates the results, the weight of the molten metal in the intermediate vessel, the slab withdrawal speed, and the operational data given in advance in the program controller (slab size, molten metal composition within one dollar before and after, and its component tolerance range).
2, a component mixing simulation is carried out in the microcomputer 12 according to a component mixing model to be described later, and the length of the portion where the slab component value is out of the molten metal component range of the front and rear charges is determined as the component mixing length. Finally, this mixing length is again transmitted to the slab cutting device 8 via the processor 11, and the portions where the components are removed are cut and separated from the good slabs in an amount equal to or less than the actual component mixing length.

As a component mixing model, for example, as shown in Fig. 2, there is a model in which the interior of the intermediate vessel 2 and mold 4 is represented by a complete mixing tank row model, and the molten metal component C4 flowing out from the final row tank is the slab component. It will be done.

However, 0 plate 2 mass flow rate (kg/5ec) WI: Weight of molten metal in tank (kg) CI: Molten metal component (stomach tk) (i-1 to 4) The calculation flow of the component mixing model will be explained with reference to Fig. 343.

As mentioned above, the casting conditions (slab size,
molten metal composition in the front and rear ladles and its allowable range), operational data (molten metal weight in the intermediate vessel, slab withdrawal speed, and injection rate calculated from this from one dollar to the intermediate vessel 2 and from the intermediate vessel 2 to the mold 4) ) Based on the information, the microcomputer 12 performs a component mixing simulation, but first of all, the component range is made dimensionless using the following equation (1).

However, C': Non-dimensional component range C": Component range C: Component value subscript a: Last dollar b: First dollar Next, it is necessary to judge the most severe mixing neck element in the dimensionless component range. There is.For the previous one dollar component range,
In formula (1), the component range C" is replaced by the component range C"
The element for which the value of the front dollar dimensionless component range C''b obtained by substituting ``b'' is the smallest becomes the mixing neck element. On the other hand, for the subsequent one-dollar component range, the subsequent one-dollar dimensionless component range C'' is obtained, and the element with the largest value of C''1 becomes the mixing neck element. The component range C″bz C″1 of the mixed neck element obtained in this manner is defined as the component range 13.14 at the ladle exchange section.

Next, initial conditions are set. According to equation (1), the non-dimensional components of the previous ladle molten metal remaining in the mold 4 and the intermediate container 2 are set as C, xQ, and the non-dimensional components of the ladle molten metal are Let C,=1. Roughly speaking, initial conditions are set according to signals such as the amount of hot water remaining in the initial intermediate container 2 inputted from the processor 11.

Once the initial conditions have been set, the casting length after a certain period of time is determined. Next, the intermediate container 2 is modeled as three complete mixing tanks of equal capacity in series, and the stepwise change in composition from the front ladle component to the rear ladle component is handled. The transient response at the outlet side of the intermediate container 2 is calculated sequentially using the following equations (2) and (3).

However, t: time (sec) Since W,, C, in the intermediate container 2 have been determined at i = 1 to 3 or more, in the next step, w4. in the mold 4 is determined. E.

is calculated using equations (4), (5), and (6) as a complete mixture model.

W4-ρW j:h (T-2T,)dh...
・・・・・・・・・・・・ (4) R system for T and -...
...System...Town... (5) However, ρ: Molten metal density (k
g/m') W: Slab width (jaw) h
: Depth from the mold surface (1) H: Penetration depth of the molten metal jet from the immersion nozzle (■) T: Slab thickness (m) T,: Mold shell thickness (II) t': Time after corporation
(sec) With this, the component change inside the mold 4 can be calculated.

These equations (2), (3), (4), and (6) are solved every minute time (1 second) using the simultaneous forward difference method, and the joint slab cutting position is determined when the condition C4-c' is satisfied.

However, by mixing the 1 dollar molten metal in the front and the 1 dollar molten metal in the back, the state in which the components gradually change from the front ladle component to the rear ladle component can be accurately calculated using the mixing model simulation described above. The microcomputer 12 determines the length of the slab from the casting position outside the front ladle component range to the first casting position within the rear ladle component range as the component mixing length. Then, the determined component mixing length is sent to the pro-controller 11, and from the pro-controller 11 to the slab cutting device 8.
Command the cutting position to accurately cut and remove the component mixture length.

<Example> Medium carbon steel A (previously 1 dollar) and high carbon t14B with the following components
(rear ladle) intermediate container capacity 40Ton, T = 25
Using a mold of 0ma + w = 1200mm,
Continuous casting of different steel types was carried out by increasing and decreasing the slab drawing speed in the range of 0.25 to 1.0 m/+In.

In this example, the mixing of carbon components is the cause of the components coming off the splice piece.

The casting pattern is shown in Fig. 4b, and the amount of molten metal in the intermediate container, indicated by 30 in the figure, is increased by 3 from 407 on at the end of the previous ladle.
This is an example in which the molten metal in the rear ladle is started to be poured into the intermediate container after the metal has been squeezed to 1000 ml. At this time, the casting speed indicated by 31 in the figure varies from 1 m/lll1n to 0.25 m/rr.
Drop to r i n, then 1 dollar after starting molten metal injection 15
Raised at a pitch of 0.25m/ll1in per second,
．． The speed is increased to On+/sin. These casting conditions are continuously input as signals to the intermediate container weight measuring device 3 and slab drawing motor control device 7 shown in FIG. Based on the calculation flow shown in FIG. 3, component mixing simulations were performed at 1 second intervals, and the results are shown in FIG. 4a. In the figure, 13 and 14 indicate the carbon content acceptance range of the front and rear ladle molten metal, respectively, 15 indicates the carbon simulation value at the center of the thickness of the slab, and 16 indicates the carbon simulation value at the surface layer of the slab. The results are in good agreement with the actual analysis values of the central part of the plate thickness and the surface layer, respectively, which are indicated by black circles 17 and white circles 18. Based on this simulation result, the casting length (19+20 in the figure) between the front one dollar component deviation position 22 and the rear one dollar component deviation position 23 is determined as the component mixing length, and a command is given to the slab cutting device 8. It was cut and separated.

Figure 5 shows a comparison between the length of cut and separated slabs and the actual mixing length of components outside the front and rear ladle component range determined by component analysis of slabs, by applying the component mixing length determination method according to the present invention to a continuous steel slab casting machine. This is an example of a diagram. Conventionally, slabs were cut and separated at a constant length, so the cut area was expressed as a horizontal line, and there were cases where the cut slab length was insufficient and components of good slabs were removed,
On the contrary, it shows that there were cases where the length of the cut slab was longer than necessary, deteriorating the casting yield. On the other hand, when cutting and separation is performed using the component mixing length determination method according to the present invention, this is represented by a solid line rising to the right in the figure, and it is clear that the slab length can be cut at approximately the same length without falling short of the actual component mixing length. Ta.

<Effects of the Invention> As described above, according to the present invention, in continuous casting of different steel types, it is possible to accurately determine the portion of a slab that fails the one-dollar component, that is, the component mixing length, so that cutting and separation of the component-mixed slab is possible. It became possible to cut slabs with approximately the same length without the slab length becoming less than or exceeding the actual component mixing length. As a result, it is possible to completely eliminate component deviations in good slabs adjacent to component-mixed slabs, and also to eliminate the risk of unnecessary cutting of good slabs, which has an excellent effect on improving slab yield and quality. It is.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an example of the equipment arrangement used for component mixing slab determination according to the present invention, Fig. 2 is an explanatory diagram showing an example of component mixing simulation modeling in the present invention, and Fig. 3 is an explanatory diagram showing an example of component mixing simulation modeling according to the present invention. Figure 4b is a graph showing the formation conditions, and Figure 5 is a graph comparing the accuracy of component mixed crystal determination by the method of the present invention and the conventional method. DESCRIPTION OF SYMBOLS 1... Shi-dol, 2... Intermediate container, 3... Intermediate container weight measuring device, 4... Mold, 5... Slab drawing roll, 6... Motor, frame... Slab drawing motor control device, 8... Slab cutting device, 9... Molten metal, 10... 9 pieces, 11... Process computer, 12... Microcomputer-113... Preface 1 Dollar component range, 14...Following dollar component range, 1
5... Simulation results of central component of slab, 16...
- Slab surface layer component simulation results, 17... Slab center analysis value, 18... Slab surface layer analysis value, 19... Front ladle side component mixing length, 20... Back ladle side component mixing length, 21... Actual seam equivalent position, 22... Front one dollar component deviation position, 23... Back one dollar component deviation position, 30... Molten metal in intermediate container, 31... Casting speed agent Patent Attorney Aki Sawa Masa Hikaru and 1 other name Juru 3 Zutsu Σ ding / 2 Ku Men cho // (3-Attack purple C mut and umbrella door t' 5 Zutsu 8 minutes shi Kongocho

Claims (1)

[Claims] When continuous casting is performed by continuously supplying the post-charge molten metal with different composition to the intermediate container while leaving the pre-charge molten metal in the intermediate container, the weight of the molten metal in the intermediate container and the slab withdrawal speed are continuously measured and the process is carried out. The injection speed from the ladle to the intermediate container and the injection speed from the intermediate container to the mold are continuously calculated based on the input and the casting dimensions given in advance to the process computer, and the measured values and the calculated values are Input the slab size, front and rear ladle component values, and component tolerance into a computer, and use the computer to perform a component mixing simulation based on the component mixing model. A method for determining a component mixing length in continuous casting, characterized in that the length of the part that comes off is taken as the component mixing length.