JPH02182360A - Method for cutting continuous cast slab - Google Patents

Abstract

PURPOSE:To prevent impossibility of allocation to the required specification and to improve the yield of cutting for a cast slab by retrieving position satisfying the required specification over the plural heats hereafter based on casting hysteresis of a strand drawing from a mold. CONSTITUTION:In each operation per heat, the required specification to each cast slab is preset. On the other hand, the casting hyteresis of the strand continuously drawn from the mold during operation is stored in order. Based on this casting hysteresis, the quality at each position of the strand is discriminated. By this discriminated result, the required specification as possible to satisfy among the above setting specification is selected, and by this, the strand is cut at the prescribed position to obtain the cast slab with desired specification. Then, in the case the position as impossible to select is detected, by the above discriminating result at the position, the required specification as possible to satisfy is retrieved over the plural heats after present. By using this retrieved result, the above setting content is reconstructed.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a continuous casting method for cutting a strand that is continuously drawn from a continuous casting mold in order to obtain a product slab that will be a material for subsequent processes. Regarding the cutting method.

[Prior art]

In the continuous casting method, molten steel in a tundish is injected into a mold with an opening at the bottom, and a strand covered with a solidified shell on the outside is continuously pulled out from the bottom of the mold, solidifying until it reaches the inside. In this method, the strands are cut at the time when the process is completed, and slabs having a desired length are continuously produced. The molten steel produced in the steelmaking furnace is stored in a ladle and supplied to the tundish, and the operation of the continuous casting equipment is as follows. This is done as one unit (one charge).

Now, the cutting length of the slab is limited to a predetermined range based on the dimensions of the final product in a subsequent process using the slab as a raw material. In addition, the quality required of the slab differs depending on the post-process that uses the slab as a raw material. While high-quality products with no surface defects are required, relatively poor quality slabs may be used as raw materials for the pipe rolling process for low-grade pipes such as gas pipes. In other words, product slabs in continuous casting must be manufactured to meet different required specifications, including dimensions, quality, etc., depending on the post-processing process in which they are used as raw materials. In operation, it is rare to manufacture slabs that all meet the same required specifications;
It is common to sequentially manufacture slabs each having different specifications. Therefore, when cutting the strand, it is determined whether the cut portion satisfies the quality standards in the required specifications, and if it does, the cut portion is cut in accordance with the dimensional standards of the required specifications. Accordingly, a product slab that satisfies desired specifications can be obtained.

In addition, the quality of the strand is determined by the casting conditions until the strand is sent out from the mold, such as the molten steel temperature and oxygen concentration in the tundish, the changing conditions inside the mold, and the drawing speed (casting speed) of the strand. ■Determined. That is, the quality of each part of the strand can be recognized from the casting history of the strand before cutting.

Therefore, cutting of slabs in conventional continuous casting equipment is performed as follows. That is, before the start of operation of a charge, the host computer that manages the overall manufacturing plan estimates the total length of the strand obtained from the amount of T8 steel in the charge, and based on this estimation result, the production casting in the charge is Determine the type of piece and bottle. This determination is given as a manufacturing order in which required specifications such as required quality standards and length dimensions are attached to each slab to be manufactured. Also, during operation, the casting condition of the strand is detected by the casting condition detector installed in each part of the continuous casting facility (II3), and these are aggregated for each unit length of the strand and the casting history of the strand is recorded. Then, when cutting the strand, the casting history and manufacturing instructions are compared, and the required specifications that can meet the quality standards with the resulting product slab are selected from the manufacturing instructions. For example, the cutting is performed according to the required specification with the highest priority.

Then, all required specifications in the manufacturing instruction are selected,
The cutting is done according to the respective specifications and the operation of the l-charge is completed. The cut slabs are sent out with labels for identifying them according to the required specifications that each slab satisfies, and are distributed to the respective post-processes according to the labels.

[Problem to be solved by the invention]

However, when implementing such a cutting method, for example,
While the manufacturing instructions are mainly composed of required specifications with relatively high quality standards, due to fluctuations in casting conditions, some of the strands contain low-quality parts, and the cutting process includes these parts. When cutting a strand, for example, when cutting a strand, there are parts near the cutting site that do not meet all of the required specifications, and as a result, it is impossible to select the required specifications and the cutting length cannot be determined. This may occur. In actual operations, this inability to select occurs with a frequency that cannot be ignored, and in such cases, in order to improve the yield of continuous casting equipment, the resulting slab is cut to a predetermined size. The slab is kept on standby as a slab without the above-mentioned mark, and is reused if satisfactory required specifications are given during subsequent operations.

However, the temperature of the slab that has been left on standby decreases during this time, so if it is to be reused, it must be heated again, which leads to a waste of heating energy.
The above-mentioned diversion has to be carried out ignoring the length dimension in the required specifications to some extent, and therefore, when processing this diverted slab in the subsequent process, it is necessary to cut off unnecessary parts, which increases the yield. There was a problem in that it was inevitable that the liquid would be wasted.

The present invention has been made in view of such circumstances, and aims to prevent as much as possible the occurrence of slabs that cannot be assigned to required specifications.
It is an object of the present invention to provide a method for cutting continuously cast slabs that can further improve the yield.

[Means to solve the problem]

The continuous casting slab cutting method according to the present invention is characterized in that different required specifications for each slab to be obtained are set in advance for each charge operation, while the strands are continuously pulled out from the mold during the operation. When the strand is cut at a predetermined part to obtain a product slab, the quality of the part is judged based on the casting history, and the required specifications that can be satisfied are determined based on the judgment result. , in the method of cutting continuous cast slabs in which the setting contents are selected from the settings and the cutting is performed according to the selected specifications, if there is a part where the selection is not possible, the determination result for the part is satisfactory. The present invention is characterized in that the required specifications are searched for over 1M charges to be performed after the current time, and the setting contents are reconfigured using the search results.

[Effect]

In the present invention, when cutting the strand, if a satisfactory specification cannot be selected from among the preset required specifications, the required specifications that can be satisfied near the cutting site are set in subsequent charges. Search among the required specifications to be performed, and reconfigure the settings of the current charge to implement the searched requirement specifications in the current charge.
The cutting is performed based on the retrieved required specifications.

〔Example〕

The present invention will be described in detail below with reference to the drawings showing embodiments thereof. FIG. 1 is a schematic diagram showing an embodiment of the method for cutting continuously cast slabs according to the present invention (hereinafter referred to as the method of the present invention). First, the configuration of continuous casting equipment to which the method of the present invention is applied will be briefly explained.

In the figure, 1 is a ladle, and the molten steel MS produced in a steel-making furnace (not shown) is stored in this ladle l.
It is transported to the upper part of the tundish 2 of the continuous casting facility and supplied into the tundish 2.

A cylindrical mold 3 having openings at the top and bottom is arranged below the tundish 2, and the molten steel supplied to the tundish 2 is stored inside the tundish 2 for 10 minutes before opening at the bottom. Molten metal is poured into the mold 3 through a pouring nozzle 4. The mold 3 has a water-cooling structure (not shown), and the molten steel injected into the mold 3 is cooled by contact with the inner wall of the mold 3 and becomes a strand 5 whose outer side is IWed with a solidified shell. It is continuously delivered vertically downward from the lower opening. A large number of cooling water nozzles (not shown) are arranged below the mold 3, and the strand 5 is further cooled by the cooling water jetted by these cooling water nozzles. Guided by a large number of guide rolls 6° 6..., it changes direction by about 90'' and travels in a substantially horizontal direction. In the figure, 7, 7... are pinch rolls; These are arranged so that they do not come into contact with the strand 5 after solidification has been completed to the inside, and are rotated while applying a predetermined pressure to the strand 5 to correct the bending and move it from the mold 3. These pinch rolls apply a pulling force of 7.7...
A cutting a8 is provided further downstream of the cutting machine 8, and the strand 5 is cut by the operation of the cutting machine 8 to form a slab 9.
and is sent to each subsequent process.

For example, the cutting R8 includes a fusing torch 8a facing the strand 5 and a drive section 8b that moves the torch in the direction of movement of the strand 5. A known structure is used in which the strand 5 is fused and cut by the arc emitted by the torch 8a while being moved synchronously.

After the ``S'' in the ladle 1 is temporarily retained in the tundish 12, it is injected into the mold 3 while the injection amount is adjusted by a sliding gate (not shown) provided in the middle of the pouring nozzle 4. , is cooled by contact with the mold 3, becomes a strand 5, and pinch rolls 7.7
It is pulled out from the mold 3 by the rotation of ..., and after solidification is completed until it solidifies inside, it is cut by a cutting machine 8, and slabs 9, 9, etc., which will be the material for the subsequent process, are manufactured. .

In the operation of such a continuous casting facility (Ifil), the cutting operation of the cutting machine 8 is controlled according to the method of the present invention in order to obtain the desired slab 9.9 that satisfies the required specifications in the subsequent process without waste. The control system is the manufacturing instruction creation unit lO1.
It includes an arithmetic control section 11, a casting state monitoring section 12, a criterion storage section 13, and a cutting machine control section 14.

The manufacturing instruction creation unit 10 manages the overall manufacturing plan, and the manufacturing plan for slabs is input to this,
Good news about the am, weight, etc. of the molten IIMs stored and supplied in the ladle 1 is given when molten steel MS is supplied to each dollar 1 in a steel making furnace (not shown). Then, the manufacturing instruction creation unit 10 transports the ladle l to the upper part of the dishwasher 2,
Before starting the operation of one charge using this charge, compare the above information regarding the molten steel MS recognized corresponding to this production plan with the above manufacturing plan, and determine the amount of slab to be obtained in the corresponding charge. Determine the type and m. The decision is made by sending the crystal standards, required specifications such as length, and labels identifying each slab to the arithmetic control unit 11 as manufacturing instructions attached to each slab. Given.

As will be described later, the arithmetic control section 11 operates the cutting machine control section 14 to execute the manufacturing instruction from the manufacturing instruction creation section 10 using information from the casting condition monitoring section 12, the judgment criterion storage section 13, etc. At the same time as issuing a command, if the manufacturing instruction cannot be executed, this is fed back to the manufacturing instruction generation unit IO to reconfigure the manufacturing instruction, and the latter operation is a feature of the method of the present invention. It becomes. This arithmetic control unit 11 stores the rotational speed of a measuring roll 25 that contacts the strand 5 just before the cutting machine 8 and rotates according to the progress of the strand 5.
The rotation speed detector 26 mounted on the rotating shaft of No. 5 is used manually. This input signal is integrally processed and used to determine the cutting timing of each slab 9, specifically, the generation timing of the operation command, as well as to determine the actual casting length and the strand 5. Used to recognize the occurrence of surplus or shortage at the end of

Now, the quality of the strand 5 produced as described above is approximately determined by the casting condition up to the point of coughing at the time it is sent out from the mold 3.

Akira I from Sri Land 5! It: The state quantities that influence are the oxygen concentration inside the tundish 2, the melt 14 inside the tundish 2? There are n degrees, a scene level in the mold 3, a drawing speed from the mold 3 (casting speed), etc. The casting state monitoring unit 12 monitors these state quantities, aggregates the monitoring results for each unit length of the strand 5, and outputs the aggregated results to the arithmetic control unit 11 as the casting history of the strand 5. . The oxygen concentration is measured by an oxygen concentration detector 21 attached to the tundish 2, and the molten steel temperature is measured by a molten steel temperature detector 22 using a thermocouple inserted into the molten fiMs inside the tundish 2. The scene level is determined, for example, by an eddy current level meter 23 placed facing the scene, and the casting speed is determined, for example, by speed detection, as the rotational speed of the pinch roll 7, mounted on the dirt drive motor 7ii. The casting condition monitoring unit 12
The casting condition is monitored using these output signals.

Further, in the judgment criterion storage section 13, the allowable ranges of the respective state quantities that govern the quality of the casting state and affect the quality are classified and stored for each quality criterion. The unit 13 operates to output predetermined stored contents to the arithmetic control unit 11 in response to future requests. Therefore, in the arithmetic control section 11, °ζ is determined by the casting condition monitoring section 1.
2, the casting history of each part of the strand 5 is obtained, and this is paired with the stored contents of the judgment criterion storage section 13 (by doing so, the quality of the part is determined to be within the required specifications. It can be determined whether the quality standards can be met.

Further, the cutting machine control unit 14 is given an operation command from the arithmetic control unit 11 and an output signal of the speed detector 24 corresponding to the advancing speed of the strand 5. starts operation in response to the operation command,
The drive section 8b of the cutter 8 is driven in synchronization with the input signal from the speed detector 24, while an arc is generated from the fusing torch 8a. As a result, the cutter 8 moves in synchronization with the advancement of the strand 5, and the strand 5 is fused and cut by the arc.

The operation of the control system constructed as described above will now be described. In the manufacturing instruction generation section 10, a manufacturing instruction is configured in units of operation of one charge, and this is given to the arithmetic control section 11 before operation. After the start of operation, the casting history of the strand 5 is given to the arithmetic control section 11 from the casting state monitoring section 12. As mentioned above, the quality of the strand 5 is determined by 6′α at the stage when it is sent out from the mold 3.
The casting state monitoring unit 12 aggregates the state quantities obtained corresponding to a suitable part of the strand 5 from the mold 3 at the time when the part is sent out from the mold 3, and sends it to the arithmetic control unit as a casting history corresponding to the part. Give to 11. Then, when this casting history is given, the arithmetic control unit 11 compares it with the stored contents of the judgment criteria storage unit 13 and determines the required specifications that have a quality standard that can be satisfied in the part of the strand 5. Select from commands.

The logic for this selection is, but is not limited to, given the casting history of the appropriate part of strand 5, it is selected from the remaining manufacturing orders that require the highest quality standards. It is preferable to compare the requirements in order and select the first requirement specification that is determined to be satisfactory.

The calculation side '4'J11 section 1' stores the required specifications selected in this way in i2f order, and from the time when the tip of the strand 5 reaches the cutting position, cuts the stored contents in order to execute them in the order in which they are stored. An operation command is issued to the device control unit 14.

That is, after the tip of the strand 5 reaches the cutting position, the calculation control unit 11 monitors the traveling distance of the strand 5 from the input signal from the rotation speed detector 26, and determines whether this is within the first required specification. At the time when the included length criteria are satisfied, the operation command is issued, and after the output of this operation command, the traveling distance is fully monitored, and this satisfies the length criterion r1y in the second required specification. At this point, the next operation command is issued. As a result, 112 pieces 9, 9... that satisfy both quality standards and length dimensions are sequentially obtained, and these are sent out with labels attached to each required specification. It is sent to a predetermined subsequent process.

Now, in the above operation of the arithmetic and control unit 11, if the casting M history at an appropriate part of the strand 5 cannot satisfy all the required specifications in the remaining manufacturing instructions, that is,
If it is not possible to select the required specifications for the part,
The arithmetic control unit 11 uses this 81? A quality standard that can be satisfied based on the manufacturing history is selected from the contents stored in the judgment criteria storage section 13, and the selection result is provided to the manufacturing instruction creation section 10.

The manufacturing instruction generation unit 10 selects a manufacturing plan after the next charge which is kept on standby within the manufacturing instruction creation unit 10, and selects one having required specifications that match the selected contents, and sends it to the arithmetic control unit U. In the arithmetic control 1 glSl that receives this, firstly, this required specification is assigned to the part, and at the same time, for example, a required specification having a length condition close to this required specification is selected from among the remaining manufacturing instructions, and this The contents are sent to the manufacturing instruction creation section 10, and the manufacturing instruction is reconfigured by excluding this required specification. In the manufacturing instruction creation unit IO, the required specifications given in this way are
It is stored for use during manufacturing instructions after the next charge.

In this way, in the method of the present invention, even if a required specification that can be satisfied by the quality of a predetermined portion of the strand 5 cannot be selected in the manufacturing instruction for the corresponding charge, the next specification already set in the manufacturing instruction creation section 10 is selected. Selection is made in a wider range of manufacturing instructions after charging, and the occurrence of slabs 9 for which the selection is not possible and which does not support the required specifications is greatly reduced.

Now, the above-mentioned operation of the arithmetic control section 11 is carried out after executing all the manufacturing instructions preset inside it or the manufacturing instructions for one charge made as described above. The process ends when the length measurement results of the part and the quality standards of the part are sent to the manufacturing instruction creation unit 10. If it is determined that it may be required in the near future, it will be placed on standby at a predetermined location.Furthermore, if the casting length is shorter than initially expected and it is not possible to execute all of the manufacturing instructions, Arithmetic control unit 1
1 sends the unexecutable surplus specifications to the manufacturing instruction creation unit 10, and ends the operation. This surplus specification will be used as a reference when creating manufacturing orders after the next Nayage.

The method of the present invention as described above is applied to a width of 700 to 1900 mm,
I! V210~b When implemented in the operation of casting equipment, the incidence of slabs that do not meet the required specifications was reduced by an average of 1.2%, and the yield rate was improved by reducing heating energy in post-processes and cutting off unnecessary parts. It was found that the deterioration of the symptoms was improved.

〔effect〕

As detailed above, in the method of the present invention, when cutting a strand, if there is no required specification that can be satisfied near the cutting site among the required specifications set in advance, the method waits to be set after the next charge. Since the required specifications that can be satisfied are searched from among the required specifications and the settings are changed using this, the incidence of slabs that do not have support for the required specifications is reduced, and such slabs are Reduction of energy required for reheating when reusing, and reduction in yield due to cutting off unnecessary parts! ! (e.g. the generation of waste is realized, etc.)
The present invention has excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the method of the present invention. l...Ladle 2...Tandate dish 3...
Mold 5... Strand 7... Pinch roll... Cutting machine 9... Slab 10... Manufacturing instruction creation section If... Arithmetic control section 12... Casting state monitoring section 13... Judgment criteria storage unit 14
...cutting machine control section

Claims (1)

[Claims] 1. Required specifications for each slab to be obtained, 1.
While the setting is made in advance for each charge operation, the casting history of the strand that is continuously pulled out from the mold is stored sequentially during operation, and when the strand is cut at a predetermined location to obtain a product slab, the The quality is determined based on the casting history, and the required specifications that can be satisfied by this determination result are determined.
In the method of cutting continuous cast slabs in which the setting contents are selected from the settings and the cutting is performed according to the selected specification, if there is a part where the selection is not possible, the required specifications that can be satisfied by the judgment result of the part are determined. A method for cutting continuously cast slabs, characterized in that the search results are searched over a plurality of charges performed after the current time, and the settings are reconfigured using the search results.