JP2003096519A - Charge control method for continuous heating furnace - Google Patents

Abstract

(57) [Summary] [Problem] To provide a method for controlling the charging of steel slabs to a continuous heating furnace capable of supplying steel slabs with small scale loss and small deviation in heat quality. A means for calculating a setup change time associated with a change of a tool and / or a change of a condition setting in a lower process required for a change of a hot working schedule is provided, and a stage having a maximum of the setup change time is provided. After the charging of the billet into the continuous heating furnace is stopped using the replacement time as the charging stop time, the billet after the hot working schedule is changed is charged.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a steel plate (also called a billet or slab) to be hot worked in a thick plate mill, a hot slip mill, a seamless steel tube rolling mill, etc. The present invention relates to a method of controlling the timing of charging the battery.

[0002]

2. Description of the Related Art When manufacturing a steel product, a heat treatment is applied to a steel piece to be processed prior to hot working. This heat treatment is carried out for the purpose of uniformly raising the temperature of the billets to a temperature suitable for rolling. It is often carried out in a continuous heating furnace in which the material is charged into the furnace and soaked.

The quality of the heat-treated steel slab is affected by the heating temperature, heating time (heating time, holding time, etc.), furnace type (continuous heating furnace or batch furnace), atmosphere and the like. In particular, in heat treatment using a continuous heating furnace, it is possible to prevent uneven heating of the steel billet by transporting it at a constant pitch and maintaining a steady state without stopping the steel billet in the heating furnace. The quality of the piece can be secured.

Even if the heat treatment is performed under optimized conditions for quality assurance, the heat treatment may be hindered by external factors. In other words, at present, in order to improve production efficiency, in many cases, a production line that integrates each process of steelmaking, continuous casting, heat treatment, and hot working is configured, and the degree of coupling between each process is also close. Sudden accidents and so-called disturbances in each process (for example, replacement of rolling schedule)
When occurs, it often happens that the extraction of the steel billet from the continuous heating furnace is once stopped and the billet being heated is made to stand by in the furnace.

On the other hand, with the diversification of customer needs, a production system capable of producing a large amount of various kinds in small quantities is required. As a result, in the hot working step, which is a lower step of the heat treatment step, the number of rolling lines, kinds, etc. Depending on the situation, process changes such as tool changes such as rolls in the rolling line, temperature changes in the heat treatment furnace in the finishing line, and blade changes in the cutting machine (hereinafter referred to as "toggle" below) will occur frequently. It became so.

Therefore, it is necessary to appropriately adjust the difference in processing speed in each process of the production line according to a sudden accident, disturbance, or process change. As a method for adjusting the difference, there are many methods of controlling the steel slab in the continuous heating furnace. It is disclosed.

Japanese Unexamined Patent Publication (Kokai) No. 2-269556 discloses a method of controlling the timing of extracting a billet from a continuous heating furnace in accordance with the cutting condition of a billet cutting step performed after heat treatment.

Further, Japanese Patent No. 3105377 discloses that
A method for predicting the timing of extracting a steel slab from a continuous heating furnace is disclosed by utilizing the work know-how of a skilled worker and considering the rolling capacity and heating furnace capacity of the slab and the occurrence status of the work down time. There is.

Further, in Japanese Patent Application Laid-Open No. 61-213318, when the rolling equipment, which is the lower step of the continuous heating furnace, is stopped, the removal of the steel pieces from the heating furnace is stopped while the upper step of the heating furnace is set. The charging control which can charge a billet from the continuous casting equipment is disclosed. That is, the extraction pitch from the heating furnace and the conveyance pitch of multiple walking beams are controlled in advance so that no material remains on the charging-side walking beam at the start of the suspension, and the extraction from the continuous heating furnace at the suspension. The present invention relates to a method for transporting a steel slab to a continuous heating furnace, in which the slab is stopped and only the walking beam on the charging side is driven to load the steel slab into the heating furnace.

[0010]

[Patent Document 1] Japanese Patent Application Laid-Open No. 2-26955
In the invention disclosed in Japanese Patent Publication No. 6, the timing of taking out the steel billet from the heating furnace is controlled in accordance with the lower step of the continuous heating furnace, so that the extraction of the steel billet from the continuous heating furnace is appropriately stopped. Become. As a result, there is a problem that the scale loss of the billet increases with the prolongation of the in-furnace time of the billet and the yield is deteriorated.

Further, in the invention disclosed in Japanese Patent No. 3105377, unnecessary stop can be prevented. However, as in the invention disclosed in Japanese Patent Application Laid-Open No. 2-269556, a steel slab is removed from a continuous heating furnace. Since the extraction is stopped, an increase in scale loss is unavoidable in this case as well.

Further, even in the invention disclosed in Japanese Patent Laid-Open No. 61-213318, since the extraction of the steel billet from the continuous heating furnace is stopped when the rolling equipment is stopped, an increase in scale loss can be avoided. Absent. Furthermore, since a plurality of walking beams are installed in the continuous heating furnace and the conveying speed is controlled for each walking beam, it is necessary to divide the walking beams, which not only increases the equipment cost but also performs complicated charging control. There is a need.

In each of the inventions disclosed in these publications, the extraction of the steel slab from the continuous heating furnace is temporarily stopped, so that the steel slab radiates heat to the hearth, the walking beam, etc., resulting in uneven heat distribution. The unbalanced heat is promoted as the time when the conveyance is stopped becomes longer, and if the unbalanced heat is large, it is not possible to stabilize the quality of the product after hot working, and it may cause trouble during hot working. .

An object of the present invention is to calculate a time required for a tool change in a lower process required for changing a hot working schedule and / or a setup change accompanying a change in condition setting (hereinafter referred to as a setup change time). Then, by loading the steel slab into the continuous heating furnace at an appropriate timing based on the setup change time, the in-furnace time of the steel slab in the continuous heating furnace and the transfer stop time are minimized,
It is an object of the present invention to provide a charging control method for a continuous heating furnace capable of supplying a steel slab having a minimal quality loss and a stable quality with minimal scale loss.

[0015]

The present inventor has optimized the charging control method for a continuous heating furnace in order to minimize the time during which the steel piece remains in the continuous heating furnace and the time during which the transportation of the steel piece is stopped. To reduce the quality loss due to scale loss and uneven heat.

A major cause of temporarily stopping the steel billet in the continuous heating furnace is the occurrence of setup change in the hot working step which is the lower step of the heat treatment step. The setup change is performed for each manufacturing lot due to the change of the hot working schedule, or when the tools used in the hot working process are consumed. Work required for setup change (hereinafter referred to as setup change work)
Is different for each production lot or when a consumed tool is replaced, it differs depending on the type of the tool, and thus the setup change time differs depending on the setup change work. Here, the production lot indicates a processing unit in the hot working step.

When the steel billet is continuously charged into the continuous heating furnace, when the setup change occurs, the time for stopping the extraction of the billet is the setup change time of the setup change work for the steel billet. It depends on the maximum setup change time. Therefore, if the charging of the steel slab into the continuous heating furnace is delayed by this time, the in-furnace time will not be unnecessarily lengthened, so no extra scale loss will occur and uneven heating will be suppressed. You can

The present invention has been completed based on the above findings, and the gist thereof is a charging control method for a continuous heating furnace characterized by the following (1) and (2).

(1) A method for controlling the charging of a continuous heating furnace in which a steel piece to be hot-worked is subjected to heat treatment, which comprises tool replacement and / or condition setting in the lower step necessary for changing the hot-working schedule. A means for calculating the setup change time accompanying the change is provided, and after the setup setup time that is the maximum of the setup setup time is set as the charging stop time, after stopping the charging of the steel slab into the continuous heating furnace, A charging control method for a continuous heating furnace, which comprises charging a steel slab after a hot working schedule is changed (hereinafter, referred to as a first invention).

(2) A charging control method for a continuous heating furnace in which a steel piece to be hot worked after being stored in a buffer provided in the upper step is subjected to a heat treatment, which is used for changing a hot working schedule. Means for calculating a setup change time required for a tool change and / or condition setting change in a necessary lower step, means for predicting a filling rate of the buffer and calculating a time until filling, and the setup The maximum setup change time among the change times,
A means for comparing the time until the buffer is filled is provided, and among the compared times, the short time is set as the charging stop time, and after the charging of the steel slab into the continuous heating furnace is stopped, the hot working schedule is set. A charging control method for a continuous heating furnace, which comprises charging a changed steel slab (hereinafter referred to as a second invention).

At this time, in the charging control method for the continuous heating furnace according to the above (1) or (2), the set-up change time set value is corrected using the actual time for the set-up change in the lower step, and a new set-up time is set. It is preferable to calculate the setup change time based on the set-up change time set value.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is an invention relating to a charging control method for a continuous heating furnace, and the first invention takes into consideration the relationship between a heat treatment step and its lower step (hot working step). The second invention considers the relationship between the upper step (buffer) in addition to the lower step.

The buffer provided in the upper step is provided in order to absorb the difference in production efficiency between the upper step and the lower step, and the billet supply capacity in the continuous casting step becomes the billet consumption capacity in the heat treatment step. If exceeded, it acts as a buffering step.
The buffer is supplied with more billet than it has,
It is called buffer overflow that it becomes impossible to physically store the billets.However, if the buffer overflow occurs, the buffer function of the buffer cannot be fulfilled and the billet production in the continuous casting process will be hindered. Therefore, overflowing the buffer is not preferable. The second invention considers prevention of such buffer overflow.

Although there is such a difference between the first invention and the second invention, the basic concept of the invention is the same. The present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a production line and a data flow relating to the present invention along with the production line.

The production line comprises a steel making process (not shown), a continuous casting process 7, a buffer 8, a heat treatment process 9 and a hot working process (rolling line 10, refinement line 1) in order from the above process.
It consists of 1). The molten steel obtained in the steelmaking process becomes a steel piece cast in the continuous casting process 7, temporarily stored in the buffer 8, and then heat-treated in a continuous heating furnace to obtain a steel product through the rolling line 10 and the conditioning line 11. To be By consistently performing line control of these processes, it becomes possible to efficiently manufacture steel products.

As a general rule, the host computer 1 has, in advance, for each manufacturing lot, the rolling finish dimension, the number of rolling strips, required tool dimensions,
A hot working schedule such as heat treatment conditions is stored. However, if it is necessary to replace the tool due to wear of the tool in the hot working process during hot working of the manufacturing lot, one manufacturing lot is divided into multiple parts and the hot working schedule is stored. In some cases. That is, the hot working schedule is stored in the host computer 1 for each manufacturing lot or each divided manufacturing lot.

The host computer 1 in which the hot working schedule is stored for each manufacturing lot is instructed to change the tool setting and condition setting to the rolling line 10 and the adjusting line 11 according to the hot working schedule, The processing schedule is given to the external storage device 2 as a data file.

This hot working schedule data file (hot working schedule file) is a setup change detecting means.
It is read by 3 and it is judged whether or not the setup change is necessary when the production lot is switched. At this time, if it is determined that the setup change is necessary, the heating furnace charging timing changing means
A command to that effect is sent to 4.

Next, the heating furnace charging timing changing means 4 searches the heating furnace interval setting file 5 for the time required for each setup change work (setup change time set value), and performs the setup change in the lower process. Calculate time. At this time, a plurality of setup change times are calculated, but in the first invention, the maximum setup change time among these setup change times is adopted as the charging stop time. Here, the maximum setup change time is adopted as the charging stop time, and when a plurality of setup change works are performed at the same time, the setup change must be completed within this maximum setup change time. Because you can.

The heating furnace interval setting file 5 is constantly corrected by the actual time learning means 6, that is, in the lower process (rolling line 10 and adjusting line 11 in FIG. 1) required for switching production lots. Correct the setup change time set value using the actual time of setup change, and based on the new setup change time set value,
It is preferable that the heating furnace interval setting file 5 is constantly modified by calculating the setup change time.

This makes it possible to calculate the setup change time with higher accuracy based on the actual time. For example, the actual time on the rolling line 10 and the actual time on the conditioning line 11 are collected, and a new setup change time set value is calculated by the exponential smoothing learning formula represented by the following formula 1, and heating is performed. The furnace interval setting file 5 should be modified.

[0033] _{t at = t b + α (} t a -t b) ... Formula 1 It should be noted, α is exponential smoothing gain (0 ≦ α ≦ 1), t a is the actual time, _{t b} is Sundedan replacement time set value , _Tat are setup change times (new setup change time set values) stored in the heating furnace interval setting file 5.

FIG. 2 is a diagram showing setup change time and actual time for piercing roll exchange as an example of calculating a new setup change time set value by exponential smoothing learning. As can be seen from Fig. 2, the actual time of piercing roll exchange is 40 to 60 minutes, which is quite variable, but by modifying Equation 1 above, a new setup change time setting value of around 50 minutes can be obtained. To be Thereby, the difference between the setup change time and the actual time can be minimized.

Next, the heating furnace charging timing changing means 4 stops the charging of the continuous heating furnace 9 for a charging stop time, the charging of the steel slab into the continuous heating furnace, and then continuously heats the continuous heating furnace 9. A command is sent to load the first billet of the production lot after changing the machining schedule. That is, in the continuous heating furnace 9, after the charging of the last billet of the production lot before the hot working schedule change was completed, the charging of the first billet of the next production lot for which the charging stop time was calculated Is stopped, and after the charging stop time has elapsed, the billet is charged into the continuous heating furnace.

By delaying the charging timing of the steel slab in this way, an empty furnace location where no steel slab exists is generated in the continuous heating furnace. However, by providing this empty furnace, the steel slab in the continuous heating furnace is provided. It is possible to minimize the in-furnace time and transfer stop time.

The above-mentioned charging control method relates to the first invention in which only the relationship between the continuous heating furnace and its lower step (hot working step 9) is taken into consideration. The first invention is when the work efficiency of the upper step (continuous casting step 7) is always lower than that of the lower step (hot working step 9), or when the work is not consistently performed from the upper step to the lower step, for example, offline. It can be applied to the case where a steel slab is supplied from.

Further, when controlling the charging of the steel slab including the relation of the above process, it is necessary to consider the buffer. In the steel making process and the continuous casting process 7, it is necessary to continuously manufacture the material, and if this is interrupted, the productivity will be hindered. Therefore, it is effective to provide the above-mentioned buffer 8. However, if the buffer capacity is large, it is possible to absorb a large difference in production efficiency between the upper process and the lower process, but an excessive buffer capacity is not appropriate. Therefore, the buffer is designed to have an appropriate capacity capable of absorbing the difference in production efficiency between the upper process and the lower process.

In the present invention, while the billet charging is stopped at the inlet side of the continuous heating furnace, the billet is unilaterally supplied from the continuous casting step 7 to the buffer 8, and the filling rate of the buffer is Rises sharply. As a result, if the charging stoppage time of the steel slab into the continuous heating furnace becomes long, the steel slab flowing in from the continuous casting step 7 may cause buffer overflow. As described above, when the buffer overflow occurs, the original function of the buffer cannot be fulfilled, and the billet production in the continuous casting process is hindered. Therefore, it is necessary to predict the filling rate of the buffer and operate in consideration of the charging stoppage time that does not cause the buffer overflow.

FIG. 3 is a diagram schematically showing the procedure of a method of charging a steel piece in consideration of the filling rate of the buffer. As shown in Fig. 3, in actual operation, to prevent accidents, the upper limit of the physical buffer capacity (buffer capacity when the buffer is physically 100% filled)
On the other hand, it is preferable to set the buffer capacity set to a lower limit as the upper limit and calculate the time until the upper limit is filled as the time until the buffer is filled. Hereinafter, the case where an arbitrary buffer capacity is completely filled is defined as a filling rate of 100% (maximum filling rate η _max ), and a specific example will be described.

At time t1, the manufacturing lot a is being conveyed in the heating furnace, and the manufacturing lot b has arrived at the heating furnace entrance side (FIG. 3 (1)). In the hot working process, when the production lot is switched from the production lot a to the production lot b, setup change work is required. At this time, the setup change time is set by the heating furnace charging timing changing means 4 described above. Δtb is calculated. In this case, even if the charging of the first slab of the production lot b into the continuous heating furnace is stopped during Δtb, the filling rate of the buffer does not reach 100%, so the production lot b passes Δtb. Stop at the entrance of the heating furnace until. During this time, the production lot a is transported in the continuous heating furnace, and an empty furnace b is generated on the inlet side of the continuous heating furnace. The total length of the empty furnace b corresponds to the distance for allowing the time required for the setup change of the production lot b to pass. On the other hand, since the charging of the billet was stopped, the filling rate of the buffer increased (Fig. 3 (2)).

At time t2 (= t1 + Δtb), the first steel slab of the production lot b is charged into the continuous heating furnace, and at the same time, the filling rate of the buffer decreases (FIG. 3 (3)).

Further, at time t3, the charging of the last steel slab of the production lot b is completed, and instead the production lot c is stopped at the heating furnace inlet side (FIG. 3 (4)). Again, in the hot working process,
When changing the production lot from the production lot b to the production lot c, a setup change operation is required, and therefore the heating furnace charging timing changing means 4 calculates the setup change time Δtc.

However, if the charging of the first steel slab of the production lot c is stopped for Δtc, the buffer filling rate exceeds the maximum filling rate η _max at time t3 + Δtc, which causes buffer overflow (see FIG. 3 (5)).

Therefore, before the filling rate reaches 100%, the first steel slab of the production lot c is charged (see FIG. 3).
(6)). At this time, the total length of the empty furnace c generated in the continuous heating furnace is a distance that can be passed for a time shorter than the time required for the setup change of the production lot c, but due to the occurrence of buffer overflow. It is possible to minimize the occurrence of scale loss and uneven heat while preventing the production of billet in the continuous casting process from being hindered, and to stabilize the quality of billet.

The filling rate of the buffer can be predicted by analyzing the amount of the buffer filling rate predicting means 12 which flows into the buffer from the continuous casting process 10 and the amount which flows out from the buffer to the continuous heating furnace. . That is, the temporal change of the steel slab in the buffer is expressed by the following equation: dV (t) / dt = q _i (t) −q _o (t). Here, V (t) is the filling amount of the buffer (book), q _i (t) is the amount flowing into the buffer (book / mi).
n) and q _o (t) are the amount (book / min) flowing out from the buffer
Is. If V _ini is the filling amount (pieces) in the buffer at the time when the charging of the steel slab into the continuous heating furnace is stopped, the formula 2 is: V (t) = V _ini + ∫ {q _i (t) −q _o (T)} dt Equation 3 is obtained.

When V ₀ is the total buffer capacity, the filling rate η (= V (t) / V ₀ ) is defined by the following equation 4.

Η = η ₀ + [∫ {q _i (t) −q _o (t)} dt] / V ₀ Equation 4 Here, η ₀ = V _ini / V ₀ .

On the other hand, under the condition that the charging of the steel billet into the continuous heating furnace is stopped, q _o (t) = 0, and the inflow amount of the k-th production lot flowing into the buffer is q _i (k) ( Book / mi
n) and Δt _k are inflow time (min) of the k-th manufacturing lot,

[0050]

[Equation 1]

Therefore, the filling rate η can be expressed by the following equation 6.

[0052]

[Equation 2]

Therefore, when charging a steel slab into a continuous heating furnace, if η ₀ at that time and the inflow amount and inflow time of the manufacturing lot flowing into the buffer are known, the time until the buffer is filled is calculated. It becomes possible.

Then, the time until the buffer is filled is calculated as described above, and the maximum set-up time (maximum set-up time among the set-up times calculated in the step of calculating the set-up time described above is calculated. The setup change time) is compared with the time until the buffer is filled (buffer filling time).

If (maximum stage change time ≦ buffer filling time), buffer overflow will not occur even if charging of the steel slab into the continuous heating furnace is stopped. On the other hand, if (maximum changeover time> buffer filling time), buffer overflow occurs if charging of the steel slab into the continuous heating furnace is stopped during the maximum changeover time.

Therefore, after the charging of the steel slab into the continuous heating furnace is stopped by using the shorter one of the maximum setup change time and the buffer filling time as the charging stop time, the steel slab is loaded into the continuous heating furnace. If you enter, buffer overflow will not occur.

In the case of (maximum step change time> buffer filling time), the extraction of the billet from the continuous heating furnace is temporarily stopped, so that the generated scale loss and unbalanced heat increase, but the buffer overflow There is no hindrance to the production of billet in the continuous casting process. Since it is possible to delay the charging of the steel billet into the continuous heating furnace to the extent that buffer overflow does not occur, extra scale loss and unbalanced heat generation can be minimized.

[0058]

EXAMPLES The first invention of the present invention was applied to a seamless steel pipe production line. A seamless steel pipe is manufactured by heating a round steel piece to about 1250 ° C in a heating furnace, perforating it with a piercer in the rolling line, rolling it with a stretching mill such as a mandrel mill, and adjusting the outer diameter of the pipe with a sizer or stretch reducer. After piped, it was heat-treated in a conditioning line and cut into dimensions.

Table 1 shows a pipe making schedule (hot working schedule) of the seamless steel pipe made. Table 1 is given by the host computer 1.

[0060]

[Table 1]

As shown in Table 1, the pipe making schedule (separation of round steel pieces, outer diameter, wall thickness, heat treatment temperature, number) of seamless steel pipes differs depending on the production lot. For this reason, in the rolling line, it is necessary to frequently perform set-up operations such as changing the tools of the piercer, mandrel mill, and sizer rolls, piercer plug, and mandrel bar according to the pipe making schedule. Further, in the refining line, setup change work for changing the temperature of the heat treatment furnace frequently occurs. In addition, the round billet classification is a classification of the outer diameter and the wall thickness within a certain range.

Table 2 is a table showing the contents of setup change necessary for the pipe making schedule. The production lot number in Table 2 corresponds to the production lot number in Table 1.

[0063]

[Table 2]

In the case of manufacturing a seamless steel pipe, when the production lot changes, the type of setup change that needs setup change is determined by the changed pipe making schedule. That is, round billet
Change the piercer roll when the classification changes, change the mandrel roll and sizer roll when the pipe outer diameter changes, change the piercer plug and mandrel bar when the pipe inner diameter changes, and change the heat treatment temperature. If so, the temperature of the heat treatment furnace must be changed.

However, if the amount of change in each item of the pipe making schedule is small, it may not be necessary to replace them or change the temperature. For example, when the manufacturing schedule changes from manufacturing lot number 4 to manufacturing lot number 5, the outer diameter increases by 9 mm. However, this change amount is sufficiently small that mandrel roll replacement is not necessary. However, it is necessary to replace the sizer roll with this change in outer diameter.

In the case of producing the steel piece of production lot No. 2,
Since the inner diameter changes as compared with the manufacturing lot number 1 before that, it is necessary to replace the piercer plug and the mandrel bar. Therefore, the setup change time was extracted from the heating furnace interval setting file 5 for these setup change operations.

Table 3 is a table showing the setup change work and the setup change time required therefor. However, since the setup change time in Table 3 is constantly updated by the actual time learning means 6, it shows a reference time.

[0068]

[Table 3]

The setup change time for replacing the piercer plug is 10
This is 5 minutes, and the setup change time required to replace the mandrel bar is 5
Minutes. Of these, the maximum setup change time is 10 minutes. This time is adopted as the charging stop time, and after the charging of the first billet of the manufacturing lot of manufacturing lot No. 2 into the continuous heating furnace is stopped. The steel billet was loaded into a continuous heating furnace.

Table 4 is a table showing the setup change time required for the pipe making schedule. As in Table 2, the manufacturing lot number in Table 4 corresponds to the manufacturing lot number in Table 1.
* In Table 4 is the maximum setup change time among the setup change times,
That is, the charging stop time of the billet is shown. Production lot number 3
To production lot number 14
According to Table 4, similarly to the production lot number 2, after the charging of the steel pieces into the continuous heating furnace was stopped, the steel pieces were sequentially charged into the continuous heating furnace.

[0071]

[Table 4]

On the other hand, in the buffer, by charging the steel slab into the continuous heating furnace, the steel slab flows out and the steel slab flows in from the continuous casting process.

Table 5 is a table showing the outflow amount from the buffer and the inflow amount to the buffer. Also in this case, the production lot number in the buffer outflow corresponds to the production line number in Table 1. The filling rate of the buffer is determined by the balance between the buffer outflow and the buffer inflow.

[0074]

[Table 5]

FIG. 4 is a diagram showing the filling rate of the buffer and the charging suspension time of each manufacturing lot when the steel slab is charged without considering the filling rate of the buffer. In FIG. 4, the horizontal axis represents the time when the time when the production lot of No. 1 was charged into the continuous heating furnace was set to zero, and the broken line represents the filling rate of the buffer.
The dots indicate the charging stop time. The charging stop time is plotted in the time corresponding to the time when the stop of charging the continuous heating furnace is started only for the manufacturing lots of manufacturing lot number 2 and thereafter.

Of the set-up times calculated without considering the filling rate of the buffer, the maximum set-up change time is set as the charging stop time, and when the charging of the billet is stopped, scale loss occurs. A steel slab having a small amount of heat, a small deviation of heat and a stable quality was obtained. However, the filling rate of the buffer exceeded 100% during the suspension of the charging of the billet of the manufacturing lot (manufacturing lot number 11) corresponding to the charging stop time indicated by A in FIG.

In the production of the seamless steel pipe of the present invention to which the first invention is applied, the maximum filling rate η _max is set lower than the upper limit of the physical buffer capacity, so that a formal buffer overflow occurs. No physical buffer overflow occurred. However, to take advantage of the buffer more efficiently, the maximum filling rate limit physical buffer capacity eta _{ma x}
When set as, when the production line is operated as described above, a physical buffer overflow may occur.

Therefore, in the first invention, when the buffer overflow does not occur, that is, when the work efficiency of the upper step (continuous casting step 7) is lower than that of the lower step (hot working step 9) as described above, It can be applied to the case of supplying the billet from offline.

Then, the second invention of the present invention was applied to a seamless steel pipe production line. The pipe making schedule of the test was the same as in the case of the first invention.

FIG. 5 is a diagram showing the filling rate of the buffer and the charging suspension time of each production lot when the steel slab is charged in consideration of the filling rate of the buffer. When the charging of the billet of manufacturing lot number 11 corresponding to the charging stop time indicated by B in FIG. 5 is stopped, the filling rate of the buffer is 10 minutes after the charging is stopped.
Since it was predicted to exceed 0%, for the production lot of production lot No. 11, where the charging of the billet should be stopped for 60 minutes without considering the filling rate of the buffer, the billet charging of the billet should be stopped in 31 minutes. Started.

Therefore, as shown by the polygonal line in FIG. 5, the filling rate of the buffer never exceeded 100%. By doing so, the in-furnace time of the steel slabs becomes longer, so scale loss and the like increase, but the production line does not stop due to buffer overflow, so that the production line can be operated smoothly.

Then, the amount of scale loss that can be reduced when the present invention is used was investigated.

FIG. 6 is a diagram showing the relationship between the in-furnace time and the scale loss. As shown in FIG. 6, in general, the longer the in-furnace time, the larger the scale loss. Since it is difficult to measure the amount of scale loss when the present invention is actually applied and when it is not applied, the time during which the charging of the billet is stopped, that is, the shortened in-furnace time is calculated from the pipe making schedule, and FIG. The amount of scale loss that could be reduced was calculated from the relationship between the in-reactor time and scale loss. In order to facilitate the calculation, the scale loss amount calculated here is the scale loss amount when the first invention is adopted without considering the filling rate of the buffer.

Table 6 is a table showing the amount of scale loss generated by stopping the extraction of the steel slab associated with the setup change work when the seamless steel pipe was manufactured for one month. The total amount of each scale loss amounts to 32.6 tons, and reducing this amount of scale loss has great value in terms of production yield.

[0085]

[Table 6]

[0086]

According to the present invention, the charging of the steel slab into the continuous heating furnace is stopped by using the maximum setting-up time among the setting-up times as the charging stop time. It is possible to minimize the in-furnace time and the transportation stop time, and as a result, it is possible to minimize the scale loss and supply the steel slab with a small deviation and a stable quality.

If the charging stop time is determined in consideration of the filling rate of the buffer in addition to the setup change time, the buffer overflow will not occur, so that the occurrence of scale loss and uneven heat can be suppressed to a low level. In addition, the production of billets in the continuous casting process is not hindered.

[Brief description of drawings]

FIG. 1 is a diagram showing a flow of data about a production line and the present invention accompanying the production line.

FIG. 2 is a diagram showing setup change set values and actual time for piercing roll replacement.

FIG. 3 is a diagram schematically showing a procedure of a method for charging a steel slab in consideration of the filling rate of the buffer.

FIG. 4 is a diagram showing a buffer filling rate and a charging stop time of each manufacturing lot when a steel slab is charged without considering a buffer filling rate.

FIG. 5 is a diagram showing a filling rate of the buffer and a charging suspension time of each manufacturing lot when a steel slab is charged in consideration of the filling rate of the buffer.

FIG. 6 is a diagram showing a relationship between in-reactor time and scale loss.

[Explanation of symbols]

1 High-end computer 2 External storage device (hot machining schedule file) 3 step change detection means 4 Heating furnace charging timing changing means 5 Heating furnace interval setting file 6 Actual time learning means 7 Continuous casting process 8 buffers 9 Heat treatment process (continuous heating furnace) 10 rolling line 11 Adjustment line 12 Buffer filling rate prediction means

Claims (3)

[Claims] 1. A method for controlling the charging of a continuous heating furnace, in which a steel slab to be hot-worked is subjected to heat treatment, which comprises a tool change and / or a condition setting change in a lower step necessary for changing a hot-working schedule. A means for calculating the setup change time associated with the above is provided, and the maximum setup setup time of the setup setup time is set as the charging stop time, and after the charging of the steel slab into the continuous heating furnace is stopped, A method for controlling the charging of a continuous heating furnace, which comprises charging a steel slab after changing the inter-working schedule. 2. A charging control method for a continuous heating furnace which heat-treats a steel slab to be hot-worked after being stored in a buffer provided in the upper step, which is necessary for changing a hot-working schedule. Means for calculating setup change time associated with tool change and / or condition setting change in a lower process, and means for predicting the filling rate of the buffer and calculating the time until filling
A continuous heating furnace is provided with means for comparing the maximum setup change time among the setup change times and the time until the buffer is filled, and the short time of the compared times is set as the charging stop time. A method for controlling the charging of a continuous heating furnace, which comprises charging the steel slab after changing the hot working schedule after stopping the charging of the steel slab into the steel. 3. A set-up change time set value is corrected using the actual time of set-up change in the lower step, and the set-up change time is calculated based on the new set-up change time set value. The charging control method for a continuous heating furnace according to claim 1 or 2, which is characterized in that.