JPH01170569A - Method for controlling automatic casting in continuous casting - Google Patents

Abstract

PURPOSE:To restrain the development of deterioration in a cast slab by regulating casting velocity according to steel kind and cross sectional size of the cast slab at the time of completing or interrupting the continuous casting operation and also continuously lowering the casting velocity in accordance with the molten metal quantity in a tundish. CONSTITUTION:The molten metal level gage 20 is arranged in a mold 14 and the molten metal weigher 17 is arranged in the tundish 11. A casting arithmetic and control unit 23 controls a tundish nozzle 19 through level signal of the leveller 20. At the time of completing and interrupting the continuous casting operation, and the weigher 17 operates and inputs the molten metal quantity from the whole weight of the tundish, and the arithmetic and control unit 23 operated the casting velocity based on the casting condition. Then, the casting velocity is regulated in accordance with the steel kind and the cross sectional size of the cast slab and also the casting velocity is continuously lowered in accordance with the molten metal quantity in the tundish 11. As the completion and the interruption of the operation can be automatized, the development of deterioration of the cast slab is prevented.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an automatic pouring control method for continuous casting, and particularly to an automatic pouring control method for continuous casting that is suitable for use when terminating or interrupting a continuous casting operation in continuous casting equipment for molten metal.

[Conventional technology]

In continuous casting operations for molten metal (hereinafter referred to as molten metal), the bath surface of the molten metal in a water-cooled mold is maintained at a constant level according to the supply of molten metal to the mold and the withdrawal of slabs from the mold. As far as automatic control of so-called steady-state operations, such as continuing operations that meet predetermined conditions, is concerned, accurate methods have already been achieved. Further, regarding start-up control for safely and appropriately starting or restarting the operation after interruption and smoothly transitioning to the steady operation, Japanese Patent Application Laid-Open No. 58-84652 describes A method has been disclosed in which the fluctuation of the molten metal bath surface in the mold is controlled during the start of drawing and its acceleration, thereby making it possible to accurately and easily make a smooth transition to steady control of continuous casting. However, no accurate method has yet been developed for termination control for safely and appropriately terminating or interrupting continuous casting operations. Therefore, conventionally, an operator would manually or automatically adjust the injection of molten metal from the tundish into the mold, and manually control the speed of slab withdrawal while monitoring the amount of molten metal remaining in the tundish. Add 4 parts of w, and when the predetermined residual melt II in the tundish is reached, the nozzle opening of the tundish is fully opened by manual operation to finish pouring the molten metal into the mold. Generally, the bath level of the internal molten metal is adjusted manually so that it is at a predetermined position, and when the process is finished, the slab is pulled out from the mold. Exceptionally, such as the ``Chiba Third Continuous Casting Completely Automatic Casting Control System'' announced at the 79th Measurement Subcommittee of the Japan Iron and Steel Institute Joint Study Group held on November 16th and 17th, 1981. , automation of the slab withdrawal speed at the end of casting has been carried out using a method as shown in FIG. This is because, by detecting the remaining molten metal fi W + in the tundish, the slab withdrawal speed is decreased from Vl to V2 (<Vl) over (t2t1) minutes, and then the remaining molten metal IW 2 (<W + ) in the tundish is reduced. With the detection of The speed is lowered by the relationship between the slab drawing speed and the slab drawing speed.

[Problems to be solved by the invention]

However, the method shown in FIG. 6 has the following problems. ■In the case of two strands, it is difficult to use automatic control of the slab drawing speed for one strand alone. For example, if another strand manually adjusts the slab withdrawal speed and pulls out the slab at a value greater than the memorized slab withdrawal speed when used under automatic control, the automatically controlled strand In this case, the amount of remaining molten metal in the tundish runs out before the final time. Therefore, the tundish slag that should originally remain in the tundish is also poured into the mold. ■If for some reason the slab withdrawal speed deviates from the memorized slab withdrawal speed when using automatic control (for example, the tundish nozzle is a bit clogged, you can manually adjust the slab withdrawal speed). )
, it is difficult to return to automatic control and use it.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned conventional problems, and is when the slab drawing speed is manually adjusted in other strands, or when using automatic control where the slab drawing speed is stored in memory. An automatic casting system for continuous casting that can safely and appropriately control the end of continuous casting even when the slab withdrawal speed deviates from the actual slab drawing speed. The purpose is to provide a control method.

[Means to solve the problem]

The present invention enables the molten metal in the tundish to reach its lower limit value in accordance with the molten tooth in the tundish, while regulating the pouring speed depending on the steel type and the cross-sectional size of the slab when the continuous casting operation is terminated or interrupted. The above objective was achieved by continuously lowering the casting speed until then.

[Effect]

As a result of various experiments conducted by the inventors, it was found that: (a) the casting speed (injection of molten metal from the tundish into the mold or the speed at which slabs are withdrawn) is regulated by the amount of molten metal remaining in the tundish; It was found that by regulating the casting speed and by regulating the casting speed according to the cross-sectional size of the C1 slab, it was possible to significantly suppress the occurrence of quality defects in the slab. The present invention was made based on such experimental results, and when the continuous casting operation is terminated or interrupted, the casting speed is regulated according to the steel type and the cross-sectional size of the slab, and the casting speed is controlled according to the tundish solid solution 1ffi. The pouring speed is continuously lowered until the amount of solid molten metal reaches its lower limit. Therefore, the continuous casting operation can be terminated or interrupted safely and appropriately, and the occurrence of quality defects in slabs can be significantly suppressed.

【Example】

FIG. 2 shows an embodiment of a control system for continuous casting equipment to which the present invention is applied. In this system, molten metal supplied from a converter etc.
It is injected from the ladle 10 into the tundish 11, and then from the tundish 11 to the sliding nozzle 1.
2 and a dip tube 13, and is injected into a mold 14, and while it solidifies within the mold 14, it is pulled out as a slab 15 by a drawing pinch roll 16 from below. In the figure, 17 is, for example, a load cell 17A,
18 is a tundish nozzle opening degree gauge for detecting the opening degree of the sliding nozzle 12; 19 is also the sliding nozzle 1;
2 is a tundish nozzle opening degree control device for controlling the opening degree; 20 is an in-mold molten metal level meter for detecting the molten metal label in the mold 14; 21 is a speed of the drawing pinch roll 16; a drawing pinch roll (PR) speed control device for controlling the drawing speed;
22 is a drawing speed meter for detecting the drawing speed from the rotational speed of the pinch roll 16 for drawing, and 23 is a drawing speed meter for detecting the drawing speed based on the rotational speed of the drawing pinch roll 16; According to the invention, this is a casting calculation control device that provides set values to the tundish nozzle opening degree control device 19 and the drawing pinch roll speed control device 21. The casting calculation control device 23 performs the following two types of calculation control. One is to input the molten metal level signal momentarily from the in-mold molten metal level meter 20, and output the result of proportional integral derivative (PID) control calculation to the tundish nozzle opening degree control device 19 as an opening degree setting value. This is the so-called in-mold molten metal level control. The other is load cell 1 for measuring the weight of Tanditshu.
Depending on the total weight of Tanditsh 11 measured at 7A,
A molten metal suspension signal is inputted every moment from the tundish molten metal weight scale 17 that outputs the molten metal weight in the tundish (6) W, and the casting specifications (mold size, slab width, descending speed pattern, maximum pouring rate for each steel type) stored in advance are input. Based on the speed regulation value, minimum casting speed regulation value depending on slab width, etc.), the casting speed is calculated as shown in Fig. 1, and the casting speed (slab drawing speed) is set in the drawing pinch roll speed control device 21 This is the casting speed control according to the present invention, which outputs values every moment. Specifically, based on the molten metal weight W (tons) in the tundish that is input from the tundish molten metal weight scale 17 from time to time, the injection ffi (ton/min) is calculated according to the continuous speed decreasing pattern shown in FIG. 1, for example. seek. Next, mold width (Ill), mold thickness (Ill)
) and the specific gravity (ton/m') of the molten metal, the casting speed V (m/min) corresponding to the injection amount is determined. Furthermore, if the obtained pouring speed V is less than the maximum pouring speed regulation value Vmax < I11/min) set in advance for each steel type, this pouring speed ■ is selected; If it is larger than the regulation value, the steel type maximum casting speed regulation value VIIlax is selected. Next, based on the selected value, determine the minimum pouring speed regulation value ■min determined from the width of the slab currently being cast (cross-sectional size of the slab).
(Ill/min), and if it is greater than or equal to this regulation value, select the previously selected value as is, and if it is smaller than this regulation value, select this minimum pouring speed regulation value V min, and then The final calculated value of the arithmetic and control device 23 is outputted to the pulling pinch roll speed control device 21 every moment. The pouring speed calculation control device 23 further performs the following operations when the molten metal ff1W in the tundish detected by the molten metal weight meter 17 reaches a preset lower limit value Wm1n (point B in FIGS. 3 and 4). A sliding nozzle 1 is installed in the tundish nozzle opening control device 29.
2, the pulling pinch roll speed control device 21 has a casting speed setting value V' when the molten metal amount in the tundish is the lower limit value Wm1n, as shown in FIGS. 3 and 4. Output min. When the operation is interrupted, the pouring speed V'si is set at the lower limit value Wntn of the amount of molten metal in the tundish so that the molten metal level in the mold reaches the desired position as shown in FIG.
After outputting this casting speed ■'mtn for a predetermined positioning time T1 for positioning the slab 15 in the mold 14, which is determined in advance from n, the casting speed is set to zero (0 points). On the other hand, when terminating the operation, as shown in Fig. 4, after maintaining the casting speed V' 1n when the amount of molten metal in the tundish is the lower limit value W1n for a predetermined head solidification time T2 (0 point), The speed is increased to the speed VE for pulling out from the continuous casting machine (point E). The operation of the embodiment will be described below with reference to FIGS. 3 and 4. FIG. 3 shows the inner layer 1ffi of the tundish according to the invention, the molten metal level in the mold (B), and the casting process according to the casting process, respectively, when the operation is interrupted and FIG. 4 is when the operation is ended. An example of the speed (slab drawing speed) (C) is shown. As shown in FIGS. 3 and 4 (A) and (B), when the tundish inner layer 1ffi decreases, the casting calculation control device 23 performs the calculation shown in FIG. 1 to adjust the casting speed. The settings are output to the pinch roll speed control device 21 for drawing. When the tundish inner layer Wit decreases and reaches the lower limit value WIIlin at point B, the casting calculation control device 23 controls the tundish nozzle opening degree control device 19.
Set and output the nozzle fully closed. When the operation is to be interrupted, as shown in FIG. 3, the casting speed is maintained at ■'min for a predetermined positioning time T1, and then the casting speed is made zero (0 point).゛On the other hand, when terminating the operation, as shown in Fig. 4, the casting speed ■'min is maintained for the head compaction time T2, and then the speed is increased to the speed ■ε for pulling out the slab from the continuous casting machine. do(
point D to point E). Short side inner rectangle 260 vil, long side inner rectangle 1060 vil, height 9
Molten steel at a temperature of 1550°C (Co, 1%, Mn: 0.8%, Si: 011
%, A! Q: 0.02%), the speed reduction pattern shown in Figure 5, the maximum pouring speed regulation value Vmax for each steel type.
-1,7 (m7 min), Minimum pouring speed regulation value VIlin = 0.3 (ra/min) according to slab width, Tundish inner layer boundary lower limit W when the tundish nozzle is fully open
m1n -4 (ton), positioning time at the time of interruption of casting T1 = 1.5 (minutes), head consolidation time at the end of casting T2 = 1
．． 5 (minutes), after head consolidation at the end of casting V' win =
4 from 0.3 (m7 min) to VE=1.5 (1/min)
When operating under conditions where the speed increases in 1 minute, casting was interrupted approximately 15 minutes after the start of deceleration from the steady speed, and
Casting was completed in 0 minutes, and the speed could be safely and appropriately increased to a speed of VE-1.5 (m7 minutes) at which the slab was pulled out from the continuous casting machine. Further, in the above embodiment, the amount of molten metal inside the tundish was detected by the molten metal weighing scale 17 including a load cell, but the configuration for detecting molten metal is not limited to this, for example, the molten metal level in the tundish was detected, It is also possible to know the amount of molten metal from this.

【Effect of the invention】

As explained above, according to the present invention, even if the slab withdrawal speed is manually adjusted in other strands or when the slab withdrawal speed deviates from the automatic control setting value, the tundish slab will not be rolled up. The continuous casting operation can be automatically terminated or interrupted safely and appropriately without causing problems such as the like, and the occurrence of quality defects in slabs can be significantly suppressed. In particular, by combining the casting start control and conventional casting control in steady operation disclosed in JP-A-58-84652 with the casting end control according to the present invention, casting automation can be achieved from the start of operation to the end of operation. All of these can be achieved, and it has excellent effects such as greatly reducing the burden on operators.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a casting speed calculation and control device used in an embodiment of a control system for continuous casting equipment in which the present invention is implemented, and FIG. 2 shows the overall configuration of the above embodiment. FIG. 3 is a diagram showing an example of the relationship between the amount of molten metal in the tundish, the molten metal level in the mold, and the pouring speed at the time of interruption of casting in the embodiment, and FIG. 4 is a sectional view including a partial block diagram. Similarly, FIG. 5 is a diagram showing an example of the relationship between the 1 m inner groove of the tundish, the molten metal level in the mold, and the pouring speed at the end of casting. FIG. 6 is a diagram showing an example of the relationship between the amount of molten metal remaining in the tundish and the slab withdrawal speed in conventional casting completion control. DESCRIPTION OF SYMBOLS 11... Tundish, 14... Mold, 15... Slab, 16... Pinch roll for drawing, 17... Molten metal weight scale in tundish, 17A...
Load cell, W...Tandish inner layer flow, Wm1n...Tandish inner layer lower limit value, 21.
... Drawing pinch roll (PR) speed control device, 22... Drawing speed meter, ■... Slab drawing speed, V max... Maximum pouring speed regulation value by steel type, Vmi
n...Minimum pouring speed regulation value depending on slab width, V's
in...W Minimum pouring speed regulation value at 1n, 23.
...Casting calculation control device.

Claims (1)

[Claims] (1) When the continuous casting operation is terminated or interrupted, the pouring speed is controlled depending on the steel type and the cross-sectional size of the slab, and the pouring is continued according to the amount of molten metal in the tundish until the amount of molten metal in the tundish reaches its lower limit. An automatic casting control method for continuous casting, characterized by continuously lowering the speed.