EP1272299A1

EP1272299A1 - Automatic start method and device for continuous casting systems

Info

Publication number: EP1272299A1
Application number: EP01927838A
Authority: EP
Inventors: Fritz-Peter Pleschiutschnigg; Dieter Alfermann; Tilmann BÖCHER; Erwin Wosch; Stephan Feldhaus; Dieter Stalleicken; Michael Vonderbank
Original assignee: SMS Demag AG
Current assignee: SMS Siemag AG
Priority date: 2000-03-29
Filing date: 2001-03-29
Publication date: 2003-01-08
Also published as: CA2404331A1; JP2003528730A; CN1420808A; AU2001254758A1; MXPA02009508A; WO2001072451A1

Abstract

The invention relates to an automatic start method for continuous casting systems, preferably for strand thicknesses of 10 -150 mm and widths of up to 3.500 mm by regulating the casting level and by means of a closure system consisting of a slider system or a stopper system. In order to automatically start the continuous casting system, the following process data is detected: the temperature of the steel at the end of the treatment thereof in the secondary metallurgic range, T.LF (11); the heating-up time of the distributor before casting begins, t.T0,5 (5.1); the inner distributor temperature after the distributor has been pre-heated, W.T (14), T.T (4); the weight of the steel in the distributor at the moment when the distributor is opened for casting to begin; the time required to fill the permanent mold, the time between the moment the permanent mold is opened and the strand (15) is removed; formation of a functional context for the product of T.LF (11), t.T0,5 (5.1), W.T (14), for example; formation of the functional relationship between filling time (15) and the product from ((11) (5.1) (14)); establishment of the desired filling time (15) for all successive castings and determination of the weight of the steel in the distributor equivalent to the desired filling time when the temperature of the steel T.LF (11) is set in an uncontrolled manner; pre-heating time of the distributor t.T (5) and distributor temperature T.T (4) directly before the kettle is opened in order to fill the distributor.

Description

Method and device for automatically starting continuous casting plants

The invention relates to a method and a device for the automatic casting of continuous casting plants, preferably for casting strand thicknesses between 10 and 150 mm and widths up to 3,500 mm using a mold level control and a closure system, consisting of a slide system or preferably a plug system. In the past few years, continuous casting plants with an oscillating mold have developed into high-performance plants that are designed for casting speeds of up to 10 m / min. The thin slab plants with a casting thickness in the mold of 40 - 150 mm and a width of 800 - 3,500 mm are particularly worth mentioning here.

These systems make an automatic start more and more necessary, since the line must have a reproducible and minimized starting piece, which is usually devalued. In addition, due to the direct connection of the continuous casting plant with the rolling process - here the CSP plant (Compact Strip Production) is mentioned as an example - the strand quality must be maximized and the material to be depreciated minimized, since the process compound is cleaned in one heat 'which does not make slabs possible.

In addition, a funnel mold (patent DE 3400220) makes it necessary that even the filling of the mold from the opening of the distributor to the departure of the slab from the mold with the subsequent reproducible start-up strategy up to the target speed of e.g. B. 6 m / min reproducible.

When pouring thin slabs with and without (parallel broad side walls) funnels in the mold, the start-up process (opening the distributor until

BESTATIGUNGSKOPIE travel of the mold bottom with the start-up strand or the slab) should be between 10 - 20 seconds.

In order to meet this time window, which is predetermined by metallurgical conditions in the mold, with a starting strategy that is based on the measurement of the mold level position using a mold level control (10) during the filling of the mold (FIG. 1), the heat balance of the To detect steel in the pan (1) on its journey from the pan furnace (2) to the continuous casting distributor (3) and in the distributor (3) itself from a kinetic and not only from a thermodynamic point of view.

The heat balance in the distributor (3) essentially depends on the distributor temperature TT and the residence time tT (5). Is the preheating temperature TT (4.1) z. B. 1200 ° C instead of 300 ° C (4.2), the pre-solidification (9) on the inner distributor wall (6.1), which consists of refractory bricks and is carried by the steel jacket (6.2), is greater during the casting process. This pre-solidification effect also occurs at the stopper (7) and stopper seat (8.1), which forms the inlet of the immersion spout (8), and leads to the disturbance of a uniform steel flow according to the valve characteristic curve, which is determined by the stopper position and the stopper seat.

Figure 2 shows a better insight into the pouring disturbance at the stopper seat (8.1). The pre-solidification (9) on the plug seat and on the plug (7) itself is shown here. When the plug opens, the pre-solidification (9) blocks the uniform steel flow according to the mass flow characteristic of the valve seat, consisting of the plug (7) and the plug seat (8.1) of the immersion spout (8).

In addition, FIG. 2 also makes it clear that the material of the immersion spout (8) and the stopper (7) has a higher thermal conductivity of approx. 10 W / K • m than that of the normal refractory material (6.1) of the distributor with one Has a conductivity of approx. 3 W / mK, which means that the pre-solidification at the plug seat is more pronounced than that in the distributor.

A further intensifying influence on the pre-solidification (9) and thus on the disruption of the start-up process occurs with a shorter preheating time tT (5), since the temperature gradient in the distributor wall at the time of sprinkling between hot face (6.1.2) and cold , face (6.2.1) of the steel armor (6.2) with a shorter preheating time and vice versa.

In addition to these influences on the pre-solidification on the stopper (7) and on the stopper seat (8.1), the steel temperature in the pan also increases, for example determined by the temperature at which the steel is discharged, TLF (11) at the end of the ladle metallurgical treatment, e.g. B. on the pan oven (2), influence.

In addition, the shape of the distributor and the distributor volume, ie both the ratio of the distributor surface to the distributor volume and the ladle pouring capacity, are important for the strength of the pre-solidification at the plug seat. However, these influencing variables are to be regarded as constant plant data and are not of direct influence for optimal process control 'online'.

This disruption of the casting start due to the uncontrolled pre-solidification, which is essentially of

^* the steel temperature at the end of the ladle metallurgical treatment,

* the preheating time of the distributor and

* the preheating temperature of the distributor

depends, often leads to malfunctions and thus to the termination of the casting process, often accompanied by a mold overflow with subsequent breakthrough of the strand shell. The invention has for its object to provide a method and an apparatus that a desired casting time in the window of z. B. 10 - 20 sec using a mold level control (10), a sprue strategy (10.1), the strand drives (10.2) and the stopper or slide valve position (10.3).

An unexpected solution to the problem, which is not a matter of course for a person skilled in the art, is described in the patent claims and is described in more detail by way of example with the aid of FIGS. 1 to 4.

Figure 1 shows the influencing variables on the heat balance of the steel, for example, between the ladle furnace and the casting start in a predetermined time window of 10-20 seconds.

FIG. 2 shows the pre-solidification, for example at the stopper of an immersion nozzle, without (a) and with (b) molding the pre-solidification.

FIG. 3 shows the functional relationship, for example in the form of a mathematical product, between the filling time of the coconut and process-technical influencing variables for different internal manifold wall temperatures.

FIG. 4 shows, by way of example for a planned filling time and for a predetermined steel temperature in the pan and a distributor preheating time, the desired distributor weight, at which the stopper is to be opened, for different distributor skin temperatures.

Figure 1 shows the influencing variables between the ladle furnace (2) and the plug seat (8.1) on the pre-solidification and thus on the casting process in the continuous casting mold (13). Have a reinforcing influence on the pre-solidification (9) on the stopper (7) and stopper seat (8.1) of the immersion nozzle (8)

^* a lower steel temperature, TLF (11) on the ladle furnace (2),

^* a lower manifold temperature inside (4.1) on the refractory skin (6.1.2) or outside on the manifold shell (6.2) than skin temperature (cold face) (6.2.1) at the end of the manifold preheating time tT (5) in the manifold heating station (5.2) and

* shorter manifold heating times tT (5) at the manifold heating station (8.2) using a burner (8.2.1) or an oven (8.2.2).

The distributor steel weight WT (14), on the other hand, is a process parameter that breaks through the pre-solidification when the distributor is opened and flushes the valve position between the plug (7) and the plug seat (8.1). The larger the pre-solidification (9), the higher the pressure (14.1) or the distribution steel weight (14) when opening the stopper while maintaining the valve opening and the same filling time.

In Figure 2, partial solidification (9) is shown schematically in partial image a), which represents an uncontrolled mass around the stopper. Sub-picture b) shows the situation after the pre-solidification (9.1) has been molded in, for example by quickly opening and closing the plug at least once before starting the start-up strategy. As a result of this measure, the uncontrolled pre-solidification, consisting of crystals and melt (steel sponge filled with melt), is molded into a temporary valve seat, which leads to a more uniform steel flow during casting and makes the casting process safer.

FIG. 3 shows the functional relationship between the filling time (15) and, for example, the product * the temperature at which the steel is delivered to the ladle furnace T • LF (11),

* the root of the heating up time of the distributor t • T (5.1) and

* the steel weight in the distributor W • T (14) at the time the distributor was opened

for different distribution skin temperatures T • T (4.1) and (4.2).

This function is essentially valid for the following boundary conditions such as

* a constant time between the delivery of the steel to the ladle furnace (2) and the opening of the ladle,

^* a constant time between the end of preheating at the preheating station (5.2) and the opening of the distributor,

^* constant pouring performance of the pan when filling the distributor,

* a constant and defined distributor lining as well

* a given distribution form and capacity.

FIG. 4 represents a table which ultimately makes the level of the invention clear. The examples clearly show that for a given steel temperature T • LF (11) and distributor preheating time t • T (5) immediately before opening the pan for a desired filling time t • M (15) of, for example, 14 or 10 seconds, the corresponding degree of filling is expressed can be determined as distribution steel weight (14) or ferro-static pressure (14.1), 'online' using a mathematical function to ensure the desired filling time.

The table makes it clear that at a distributor skin temperature of 1200 ° C (4.1) a pouring time t • M or filling time (15) of ^* 14 sec at 18.2 t and

* 10 sec at 19.6 t

or from 1,300 ° C (4.2) a filling time (15) of

* 14 sec at 13.8 t and

* 10 sec at 15.5 t

established.

This depicted relationship now makes it possible, independently of the steel temperature (11) and the heating-up time of the distributor (5), which are subject to fluctuations in operation, to control the casting process by determining the corresponding distributor steel weight and thus to fully automate it.

In addition to these influencing variables mentioned, other energetically relevant influencing variables (21), for example the residual moisture or residual volatile (open water) after preheating in the wear lining (6.1.1), which is applied to the permanent lining (6.1) in the form of spray compound, for example , Water of crystallization and / or organic volatiles), also influence the pre-solidification (9) quantitatively.

Claims

claims

1. A method for the automatic casting of continuous casting plants, preferably for casting strand thicknesses between 10 and 150 mm and widths up to 3,500 mm using a mold level control and a closure system, consisting of a slide system or preferably plug system, characterized in that the automatic start the detection of the following process data:

* Steel temperature at the end of steel treatment in the secondary metallurgical area, T • LF (11)

* Heating time of the distributor before the start of casting, t • T ^0.5 (5.1)

* internal manifold wall temperature after preheating the manifold, W • T (14), T. T (4)

* Steel weight in the manifold at the time the manifold is opened to start casting

* Filling time of the mold, time between opening the mold and running off the strand (15)

* Forming a functional relationship, for example, of the product from T • LF (11), t • T ⁰ ' ⁵ (5.1), W • T (14)

* Form the function between the fill time (15) and the product from ((11) (5.1) (14))

* Determination of the desired filling time (15) for all subsequent castings and determination of the distributor steel weight equivalent to the desired filling time with an uncontrolled setting of the steel temperature T • LF (11), distributor preheating time t • T (5) and distributor temperature T • T (4) is used immediately before opening the pan to fill the distributor.

2. The method according to claim 1, characterized in that casting is carried out with an oscillating mold.

3. The method according to claim 1 or 2, characterized in that the pre-solidification is formed by at least one quick opening and closing in the area of the plug seat.

4. The method according to any one of claims 1 to 3, characterized in that continuous casting is carried out on a thin slab system with a casting speed of max. 12 m / min.

5. The method according to any one of claims 1 to 4, characterized in that the transport times of the pan from the delivery pan oven (2) to the opening of the pan and the distributor between the heating level and the opening of the distributor are taken into account to determine the function.

6. The method according to any one of claims 1 to 5, characterized in that the outer skin temperature of the distributor (6.2.1) is determined and taken into account when determining the function.

7. The method according to any one of claims 1 to 6, characterized in that when calculating the fill time function (15) in addition to the process parameters ladle steel temperature (11), manifold heating time (5), manifold internal temperature (4) and manifold steel weight TW (14), there are also other energetically relevant influencing variables (21) such as those after preheating in the refractory wall (6.1) and the spray mass (6.1.1) remaining residual water content and / or the content of residual volatiles introduced via the distributor spray mass (6.1.1) can be recorded in the online computer (20) via the mathematical resolution.

8. Device for producing slabs between 10 and 150 mm thick and up to 3.5 m wide using a casting level control (10) connected to the strand drive (10.2) and the flow valve, preferably a plug (10.3), in particular for carrying out the method according to claim 1, characterized in that a temperature measuring device is arranged at the end of the steel treatment (11.1) and a measuring system for time recording the distributor heating process (5.3), a measuring system for determining the weight of the distributor steel during the filling process of the distributor (14.2) Measuring system for time recording from the start of the filling process of the mold (13) to the withdrawal of the strand (15.1) from the mold and a computer system (20) for online determination of the distributor weight (14) to ensure the casting time (15) taking into account at least the The distributor temperature (11) and the distributor heating time (5) at the latest immediately before opening of the distributor are provided and are linked to one another in terms of signal technology.

9. The device according to claim 8, characterized in that the mold broad side walls (13.1) have a concave shape (13.1.1).

10. The device according to claim 8 or 9, characterized in that the continuous casting system is equipped with continuous drives (10.2) which allow a casting speed of max.12 m / min.

11. Device according to one of claims 8 to 10, characterized by a measuring device for determining the outer skin temperature (6.2.1).