JP2013224463A - Method for controlling slab conveying in continuous heating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling slab conveying in a continuous heating furnace, which can prevent a decrease in productivity by performing slab conveying in the heating furnace as efficiently as possible when slab feed on the feed side is delayed to thereby prevent the distance between slabs in the furnace from becoming extremely long.SOLUTION: There is provided a method for controlling slab conveying in a continuous heating furnace where slabs are heated while they are pitch-conveyed from the feed end of the heating furnace to the extraction end by means of a walking beam apparatus. In the method, slab conveying in the heating furnace is continued in accordance with the extraction pitch when the feed of a slab to be fed is behind the set timing, and before the slab to be fed reaches a feed table, when the distance between the immediate preceding fed slab and the slab to be fed reaches the limit distance at which extraction delay does not occur when the slab to be fed is extracted, the convey of the slab by means of the walking beam apparatus is stopped and the arrival of the slab to be fed is waited.

Description

  The present invention relates to a method for controlling conveyance of a slab that is a material in a walking beam conveyance type continuous heating furnace.

  As shown in FIG. 4, the walking beam conveyance type continuous heating furnace is a repetitive rectangular motion of ascending, advancing, descending, and retreating with respect to the fixed skid 1 that supports the bottom surface of the slab S and the slab S on the fixed skid 1. And a heating beam furnace having a moving skid 2 for moving the slab S to heat the slab S charged from the charging table 11 while conveying it at a constant pitch from the charging end to the extraction end. 10. In the figure, 3 is a skid frame, 4 is a main burner, and 5 is a side burner.

  In general, in the walking beam apparatus, since all slabs in the heating furnace are transported at the same pitch in the furnace length direction, the slab interval that is vacant on the charging side is transported while being held up to the extraction side.

  As a slab conveyance control method in a heating furnace equipped with such a walking beam device, there are extraction priority control and charging priority control.

  In the extraction priority control, the slab in the heating furnace is transferred at a predetermined transfer pitch so that the slab can be extracted in accordance with the rolling pitch of the rolling process on the heating furnace extraction side, and the next extraction slab to the heating furnace extraction end is transferred. This is a transport control method that prioritizes supply. On the other hand, the charging priority control is carried out after conveying the slab in the furnace so as to secure a space for charging the slab at the heating furnace charging end so that the interval between the slabs charged in the heating furnace becomes a specified interval. This is a method in which the conveyance is not performed until charging is performed. Usually, charging priority control is often adopted so as not to leave an extra space between the slabs in the heating furnace.

  In the former extraction priority control, as shown in FIG. 5, the slab at the extraction end of the heating furnace is extracted (step S200), and the WB (walking beam device) is operated to advance the slab in the furnace (step S200). S210), thereby securing a charging space at the charging end (step S220). Next, the presence or absence of a charging material (slab) on the charging table is detected (step S230). If there is a charging material, the charging material is charged into the heating furnace (step S240). After charging, the WB is advanced to transport the slab in the heating furnace. If there is no charge, the WB is advanced to prioritize slab extraction at the extraction end (step S250). Next, the extraction end slab is moved to the extraction position (step S260). When the extraction timing comes, extraction of the slab at the heating furnace extraction end is executed (return to step S200). In this extraction priority control, the slab is continuously extracted at a predetermined extraction pitch. Therefore, when there is no slab to be charged in the charging table due to a delay in supply, the slab of the heating furnace is conveyed to the extraction side without charging the slab. As a result, the slab-free area expands in the furnace. Since the occupation area of the slab, which is the material to be heated, with respect to the hearth of the heating furnace is reduced, the amount of fuel consumed per slab increases, and the fuel cost increases. Furthermore, the area where no slab is present is expanded, so that the distance between the slab charged on the charging side (charging slab) and the previous slab (front slab) becomes wider. After the slab is extracted, it takes too much time to transport the charging slab to the extraction end, and the charging slab cannot be extracted at a predetermined extraction timing. This phenomenon is called “conveying neck”.

  On the other hand, in the latter charging priority control, as shown in FIG. 6, the extraction slab at the extraction end of the heating furnace is extracted (step S300), and the WB (walking beam device) is operated to advance the slab in the furnace. (Step S310), thereby securing a charging space at the charging end (Step S320). Next, the presence or absence of a charging material (slab) on the charging table is detected (step S330), and if there is a slab, the slab is charged (step S340). If there is no slab, the WB is not operated and the next slab is awaited (step S350). Following step S340, the extraction end slab is moved to the extraction position (step S360). When the extraction timing comes, extraction of the slab at the extraction end of the heating furnace is executed (return to step S300). In this charging priority control, when there is no slab to be charged into the charging table due to a delay in supply or the like, the slab that has been charged in the heating furnace is in a standby state without being conveyed. Even at the timing, the slab to be extracted has not reached the extraction end, the extraction is delayed, and the productivity of the rolling process is lowered. In addition, since the slab is heated in the furnace for a long time until the next slab is charged, there is a problem that the fuel cost increases. This is called “charging neck”.

  This "charging neck" is, for example, when the charging (feed) pitch of the charging material is slower than the pitch of the extracting material, for example, depending on the billing order of the billet crane that transfers the slab to the charging side on the heating furnace charging side. This occurs when the case where the slab on the extraction side of the heating furnace is wide and short pitch and the slab on the charging side is narrow is continued.

In terms of a mathematical expression, when charging width / charging pitch ≦ extraction width / extracting pitch, it becomes a charging neck.
For example, when considering extraction from a heating furnace at a 2-minute pitch as an extraction-end slab width of 2 m and a charging-end slab of 1 m, the charging-side slab does not supply the slab within 1-minute pitch. It becomes. However, since the supply of the slab to the charging side of the heating furnace usually includes a transfer step performed from the billet yard using a billet crane, it is difficult to predict the supply pitch.

  In order to solve such a problem, Patent Document 1 includes a selection signal indicating whether charging priority control or extraction priority control is adopted, and a signal that detects a slab position in the furnace and a slab interval in the furnace. Is used to calculate the slab charging pitch in the charging section and control the supply of the slab to the charging device in accordance with the charging pitch.

JP-A-2-258914

  However, in actual operation, since the slab position and the slab interval in the furnace change in a complicated manner from moment to moment, even if the method disclosed in the above-mentioned Patent Document 1 is used, the operation of the billet crane in the billet yard is performed. It is very difficult to predict the slab charging pitch including the situation, and even if it can be calculated, it will contain many errors.

  Therefore, the present invention performs as efficiently as possible the conveyance of the slab in the heating furnace when the supply of the slab on the charging side is delayed, prevents the slab interval in the furnace from becoming extremely wide, and increases the productivity. It aims at providing the slab conveyance control method in the continuous heating furnace which can suppress the fall of this.

  In order to solve the above-mentioned problems, a first configuration of the present invention is a slab conveyance control method in a continuous heating furnace in which a slab is heated by pitch walking from a charging furnace's charging end to an extraction end by a walking beam device. When the supply of the slab to be charged is delayed from the set timing, the slab in the heating furnace continues to be conveyed in accordance with the extraction pitch, and before the scheduled slab arrives at the charging table, one If the distance between the previous charged slab and the slab when the planned slab is loaded is the limit distance that does not cause extraction delay when extracting the planned slab, the walking beam The conveyance by the apparatus is stopped, and the arrival of the scheduled slab is waited for.

  In this first configuration, when the supply of the slab scheduled to be loaded is delayed from the set timing, the distance between the previous loaded slab and the slab when the planned slab is loaded is When the planned slab is extracted, the slab in the heating furnace is transported by the walking beam device until it reaches the limit distance that does not cause extraction delay, and after reaching the limit distance, the transport by the walking beam device is stopped and charged. We will wait for the arrival of the planned slab. Thereby, it can suppress that the distance between the slabs in a heating furnace becomes extremely wide, and can suppress the fall of productivity.

The second configuration of the present invention is characterized in that the limit distance that does not cause the extraction delay is calculated by the following equation.
Limit distance = walking beam device transport speed x (extraction scheduled time interval between previous charging slab and next charging slab)-width of previous charging slab By performing this calculation, the limit distance can be preset. it can.

  According to the present invention, fuel loss due to an extremely wide distance between slabs in a heating furnace can be prevented, and an extraction delay at the extraction end can be suppressed to reduce production loss.

It is a flowchart which shows the procedure of the slab conveyance control method in the continuous heating furnace which concerns on embodiment of this invention. It is explanatory drawing which shows the difference of operation | movement with this invention and the extraction priority control method, (a-1)-(a-3) is this invention, (b-1)-(b-3) is extraction priority control. Show the case. It is a graph which shows the production loss reduction effect by the Example of this invention. The structural example of the continuous heating furnace provided with the walking beam apparatus is shown, (a) is a side view, (b) is sectional drawing. It is a flowchart which shows the extraction priority control method. It is a flowchart which shows the charging priority control method.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
The slab conveyance control method in the continuous heating furnace according to the embodiment of the present invention will be described based on the flowchart of FIG.

Step S100: Extract the slab at the extraction end of the heating furnace.
Step S110: WB (walking beam device) is operated to advance the slab in the heating furnace.
Step S120: WB is stopped when a charging space is secured at the charging end or when the slab reaches the extraction end.
Step S130: When the charging space is secured and the WB is stopped, the process proceeds to Step S140, and when the slab reaches the extraction end and the WB is stopped, the process returns to Step S100.
Step S140: The presence or absence of a charging material (slab) on the charging table is detected.
Step S150: If there is a slab, insert the slab and return to step S110.
Step S160: If there is no slab, the WB is operated and the slab in the furnace is advanced.
Step S170: WB is stopped depending on whether the slab has reached the limit distance, the slab has arrived at the charging table, or has reached the extraction end.
Step S180: If the limit distance has been reached, the process proceeds to step S190. If the slab arrives at the charging table, the process proceeds to step S150. If the slab has reached the extraction end, the process proceeds to step S195. If the slab has arrived at the charging table, the process proceeds to step S150.
Step S190: Waiting for the arrival of the slab at the charging table with the in-furnace slab stopped, the process proceeds to step S150 when the slab arrives.
Step 195: Extraction end slab is extracted. The process returns to step S160.
here,
Limit distance = walking beam device transport speed × (scheduled extraction time interval between the previous charging slab and the next charging slab) −the width of the previous charging slab.

The difference between the slab conveyance control method of the present invention and the extraction priority control method will be described with reference to FIG. Both methods show examples in which the WB is operated to advance the slab in the furnace when there is no slab on the charging table.
In the extraction priority control, as shown in FIGS. 2 (b-1) and 2 (b-2), there is no charging material (slab) on the charging side of the heating furnace 10 after the previous charging of the slab Sa. Even when the slab is transported in accordance with the extraction timing, the rear end of the slab Sa loaded last time and the front end of the slab Sb loaded next time depending on the time until the next slab is loaded The slab is conveyed to the extraction end while the interval between the slabs is empty and the interval is maintained. If the interval is too large, as shown in FIG. 2 (b-3), the slab Sb does not reach the extraction end at the extraction timing, causing an extraction delay.

  On the other hand, in the slab conveyance control method of the present invention, when there is no charge (slab) on the charging side of the heating furnace 10, as shown in FIGS. 2 (a-1) and 2 (a-2). The slab Sa is transported by WB by the distance that does not cause the extraction delay at the extraction end, that is, the limit distance shown by the equation (1), and when it reaches the limit distance, it waits there. When the slab arrives at the loading table, the slab Sb is loaded, but the distance between the rear end of the previously loaded slab Sa and the front end of the next loaded slab Sb is a limit distance that does not cause an extraction delay. The slab is conveyed to the extraction end while maintaining the interval. Then, as shown in FIG. 2 (a-3), after extracting the slab Sa, the slab Sb reaches the extraction end by the extraction timing, and no extraction delay occurs.

The space at the time of the loading neck does not become a transport neck at the extraction end because the upper limit is the limit distance calculated by the following formula that embodies the above formula (1).
Limit distance = conveying speed × (scheduled extraction time interval from slab Sa to slab Sb) −slab width of slab Sa For example, conveying speed is 16.7 mm / second (1 m / min), extraction scheduled time interval is 3 minutes, slab If the width of Sa is 1 m, the limit distance = 2 m.

  FIG. 3 shows the accumulated time (referred to as production loss time) in which rolling in the rolling process is delayed within one month in each of the conventional charging priority control and the control according to the present invention. . In the first period and the second period when the charging priority control was applied, the production loss time was 5.0 hours and 3.2 hours, but the third period and the fourth period when the present invention was applied. Then, it was confirmed that the production loss time was reduced to 0.4 hours and 1.3 hours, and the effect was remarkable.

  As described above, in the present embodiment, when the supply of the slab to be charged is delayed from the set timing, the slab in the heating furnace is continuously conveyed in accordance with the extraction pitch, and the slab to be charged is heated in the heating furnace. Before arriving at the charging end of the slab, the distance between the previous slab and the slab when the planned slab is loaded does not cause an extraction delay when extracting the planned slab. When the limit distance is reached, the conveyance by the walking beam device is stopped and the arrival of the scheduled slab is waited for, thereby preventing an extreme extraction delay at the extraction end and reducing the production loss.

S, Sa, Sb Slab 1 Fixed skid 2 Moving skid 3 Skid frame 4 Main burner 5 Side burner 10 Heating furnace 11 Loading table

Claims (2)

A slab transport control method in a continuous heating furnace that heats a slab while pitch transporting from the charging end to the extraction end of the heating furnace by a walking beam device,
When the supply of the slab to be charged is delayed from the set timing, the slab in the heating furnace continues to be transported according to the extraction pitch, and before the scheduled slab arrives at the charging table, If the distance between the charged slab and the slab when the planned slab is loaded is a limit distance that does not cause extraction delay when extracting the planned slab, the walking beam device The slab conveyance control method in a continuous heating furnace characterized in that the conveyance by the slab is stopped and the arrival of the slab scheduled to be charged is awaited. The slab transfer control method in a continuous heating furnace according to claim 1, wherein a limit distance that does not cause the extraction delay is calculated by the following equation.
Limit distance = walking beam device transport speed x (scheduled extraction time interval between previous charging slab and next charging slab)-width of previous charging slab