JPH0377851B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for operating a heating furnace in an alternating rolling system.

Prior Art In a technology in which hot slab slabs cast by a continuous casting device are heated in a heating furnace and then rolled by a rolling mill, if the production capacity of hot slab slabs by the continuous casting device is smaller than the rolling capacity of the rolling mill, the rolling mill This results in a decrease in the operating rate. In recent years, to address this issue,
Alternate rolling that aims to improve the operating rate of the rolling mill by heating hot slabs and cold slabs stored in the slab yard in a separate heating furnace and replenishing the shortage of hot slabs. A system has been developed and put into practical use. This system, for example, as schematically shown in FIG. A slab yard (not shown) that stores cold slab slabs (hereinafter referred to as CCR slabs);
A first heating furnace 1 (hereinafter referred to as Furnace No. 1) that heats the DHCR slab, and a second heating furnace 2 (hereinafter referred to as Furnace No. 2) that heats the HCR slab and CCR slab.
, an approach table 3 that loads and conveys each slab supplied from the continuous casting device and the slab yard, and a charger 4 that loads the DHCR slab conveyed by the approach table 3;
A pusher 5 that charges HCR slabs and/or CCR slabs into the No. 2 furnace, a conveyance table 6 that loads and conveys the slabs extracted from the respective furnaces, and rolls the slabs conveyed by the conveyance table 6. The No. 1 furnace consists of a rolling mill 7 and a control device (not shown) that controls the operation of each of the above-mentioned members.
When an empty furnace is created in the furnace in a divided walking beam furnace consisting of a and a second walking beam (hereinafter referred to as WB) 1b (when the interval between slabs is larger than the slab width), The empty furnace is closed to control the appropriate spacing between slabs, and a matching zone is provided on the charging side. And from No. 2 reactor 2
The extraction pitch of the HCR slab and/or CCR slab (hereinafter referred to as the HCR extraction pitch) is set to be a constant ratio to the extraction pitch of the DHCR slab from the No. 1 reactor 1 (hereinafter referred to as the DHCR extraction pitch), Furthermore, the extraction order and extraction time of the slabs charged into each furnace are set based on the extraction ratio of each furnace.

Therefore, the DHCR slab supplied from the continuous casting equipment and the HCR slab supplied from the slab yard,
CCR slabs are approach table 3,
They are charged into the No. 1 furnace 1 and the No. 2 furnace 2 via the charger 4 or the pusher 5, heated in each furnace, extracted in the above order at the above times, and rolled in a rolling mill.

Problems to be Solved by the Invention As mentioned above, in the conventional alternating rolling system, the order of extraction of slabs from the No. 1 and No. 2 furnaces is determined, and the extraction ratio of slabs from each furnace is kept constant. If the charging pitch of the DHCR slab charged into the No. 1 furnace changes due to changes in the length of the charged DHCR slab to a longer or shorter one, the rolling throughput may change due to the rolling capacity. DHCR slabs may accumulate in the matching zone of the No. 1 furnace, resulting in a drop in the temperature of the slabs as they wait to be charged into the heating furnace. As a result, the rolling ratio of the DHCR slab decreased and the fuel consumption rate of the heating furnace increased.

This will be specifically explained based on FIGS. 12 and 13.

Here, the extraction ratio of the slabs alternately extracted from the No. 1 furnace and the No. 2 furnace is set to 2:1.

The example shown in Figure 12 is charged to the No. 1 reactor.
This shows the case where the DHOR slab changed from a small unit weight (12.3t) to a single weight (16.5t).When slabs of single weight were charged into the continuous caster at a pitch of 21 slabs/h, From Furnace 1, 21 slabs with small unit weight are extracted per unit time, and from Furnace 2, since the extraction ratio is set to 2:1, 10.5 slabs with small unit weight are also extracted per unit time. . Therefore, the number of rolls rolled is 31.5 rolls/H, and the rolling throughput is 387 t/H, which is considerably lower than the rolling capacity of 443 t/H for slabs of small unit weight.

As shown in Figure 13, if the slab is switched from single weight to smaller unit weight, the slabs with smaller unit weight will be charged at a pitch of 28 slabs/H. Considering the rolling capacity of 594 t/h for critical slabs, the number of slabs that can be handled is limited to 36/h, so 24/h from No. 1 furnace 1 and 24/h from No. 2 furnace 2.
Only 12 slabs/H can be extracted each, and therefore, 4 DHCR slabs to be charged to Furnace 1 are waiting to be charged or have to be removed from the line per unit time. It will stop happening.

Moreover, since the slabs removed from the line and reset are set in advance to be extracted in the No. 1 furnace, the number of slabs actually extracted decreases accordingly, reducing the operating rate of the rolling mill. Become.

If the extraction ratio of the slabs extracted from each furnace is set to be constant, there is also the disadvantage that alternate rolling of different steel types cannot be performed depending on the steel type. In other words, high carbon steel (HC) and stainless steel (Ni-SUS)
For products with restrictions on in-furnace time, such as, the in-furnace time fluctuates due to fluctuations in the charging pitch as described above.
This is because overheating may cause deterioration or insufficient heating.

Means for Solving the Problems As a result of various studies in order to solve the above problems, the inventors of the present invention came to the conclusion that it is necessary to satisfy the following conditions.

In other words, the DHCR slab charged to the No. 1 reactor may be waiting for charging or may be rejected.
In order to prevent an increase in the fuel consumption rate due to a decrease in the rolling ratio of the DHCR slab, it is necessary to match the extraction pitch of the slab from the No. 1 furnace with the pitch of the slab continuously produced by the continuous casting equipment. It is necessary to prioritize the extraction of slabs from Furnace No. 1.

In order to make the most effective use of the rolling capacity of the rolling mill, it is necessary to calculate the difference between the extraction time required for the required number of slabs extracted from the No. 1 furnace and the time required for rolling the slabs extracted from the No. 2 furnace. It is necessary that the No. 2 furnace is operated for extraction so that the extraction pitch is set based on the available rolling time.

When performing alternate rolling of different steel types, if the type of steel charged to the No. 2 furnace has restrictions on the furnace time, such as high carbon steel (HC) or stainless steel (Ni-SUS), the No. 2 furnace Prioritize the extraction of slabs from the furnace and set the extraction pitch from the No. 1 furnace based on the extraction pitch.

In order to satisfy the above conditions, the extraction pitch from the No. 1 and No. 2 furnaces is not a fixed ratio, but the rolling pitch may vary due to changes in the charging pitch of the No. 1 furnace or the product thickness, or It is necessary that the setting is such that it varies depending on the type of steel being charged. That is, it is necessary that the extraction operation of the first furnace and the second furnace be performed so that the ratio of the number of extracted bottles is variable.

The present invention has been made based on the above matters, and includes a No. 1 furnace that heats hot slab slabs supplied from a continuous casting device, and a No. 1 furnace that heats hot slab slabs and/or cold slabs supplied from a slab yard. In the alternating rolling system, which comprises a No. 1 furnace and which alternately extracts and rolls each of the slabs from each of the heating furnaces, each of the heating furnaces is extracted such that the extraction ratio between the No. 1 furnace and the No. 2 furnace is variable. It is characterized by being operated.

Here, one or more No. 1 furnace and No. 2 furnace may be provided.

Example This example uses the already explained alternating rolling system shown in FIG. 1 to perform calculations according to the alternating rolling/rolling order calculation and extraction time prediction model shown in FIGS. 2 to 9 by a control device (not shown). Based on the calculation results, extraction operations for the No. 1 furnace 1 and the No. 2 furnace 2 are performed.

Below, the method of determining the number of draws, the order of extraction, and the extraction time for the first furnace 1 and the second furnace 2 will be explained based on FIGS. 2 to 9.

Figures 3 to 5 are a series of flowcharts, and as shown in Figure 2, the LD ₁ zone (soaking zone),
Number of slabs extracted in each zone of No. 1 furnace 1, which is divided into multiple zones: LD ₂ zone (third heating zone), LD ₃ zone (second heating zone), and LD ₄ zone (first heating zone) The order and extraction time, the number of slabs to be extracted in each zone of the No. 2 furnace corresponding to each zone of the No. 1 furnace, the extraction order, and the extraction time are sequentially determined.

That is, first, as shown in FIG. 3, the length of each divided zone LDj of the No. 1 furnace is set, and the required extraction time and rolling time of the DHCR slab staying in the LDj zone are determined as follows.

As shown in subroutine A in Fig. 6, the length of the charged slab SLi (m), that is, the length of the DHCR slab cast in the continuous casting machine (CC) and cut to a predetermined length, is determined by the CC drawing speed VCC ( m) That is, divided by the casting speed, the charging pitch of the DHCR slab PCC (sec)
seek. Since the DRCR slabs to be charged vary in length, the charging pitch of the DHCR slabs charged to the No. 1 furnace is expressed as the DHCR slab average charging pitch PD′j, which is the average value of each slab, and is calculated as follows. I ask.

PD′j (in) = _o 〓 ⁱ⁼¹ (WDji/PCCi)/n (m/sec) WDji: Slab width + slab spacing DHCR average charging pitch PDj (in) is normally DHCR
Set as slab average extraction pitch PDj.

In special cases, for example, when rolling is stopped due to rolling roll replacement or rolling mill repair, etc., the matching zone is stopped as shown in Figure 2.
Taking into account the stagnation of the DHCR slab, subroutine B shown in Fig. 7 calculates the extraction pitch up rate ΔPDMj for clearing the matching zone.
Find it according to.

That is, as shown in Figure 2, calculate the moving distance La ₁ of the WBI system when extracting the slab of LD ₁ zone, and based on the calculation result, calculate the matching zone when extracting the slab of LD ₁ zone. Predictively calculate the occupied slab length LM. LM ₁ ,
Extraction pitch up rate ΔPDMj when extracting slabs in each zone compared to LM ₂ and LM ₃ respectively
seek.

The DHCR slab average extraction pitch PDj is newly set as the above-mentioned average charging pitch PD'j (in) plus the extraction pitch up rate ΔPDMj.
If the slab is extracted normally without staying in the matching zone, ΔPDMj is 0.

Next, the predicted baking time tji of the slab is calculated as the shortest baking time based on the actual slab temperature using a well-known heat transfer calculation formula, and the extractable pitch Pyji of each slab is calculated according to subroutine C shown in Fig. 8. Along with that, the average value is the grilled pitch.
Find PDFj.

The baked pitch PDFj and the average extracted pitch PDj
(If slabs remain in the matching zone, add the above-mentioned extraction pitch increase rate ΔPDMj). When the firing is early, the average extraction pitch PDj is equal to PDj, and when the firing is slow, the average extraction pitch is increased to PDj. When there is, it is converted to PDFj.

Number of slabs extracted from the LDj zone of No. 1 furnace
NDj is determined by the following equation since the length of the previously set LDj zone, the slab width of all the slabs staying in the zone, and the spacing between each slab are equal.

LDj= _NDj 〓 ⁱ⁼¹ WDji Further, the extraction time tj is the sum of the times for extracting each slab, and is expressed as follows.

tj= _NDj 〓 ⁱ⁼¹ (WDji/PDj) The time required to roll the extracted slabs, that is, the required rolling time tDRj is the sum of the rolling times of each slab and is expressed as follows.

tDRj= _NDj 〓 ⁱ⁼¹ rDi rDi: Rolling time for one slab As described above, the extraction time tj and rolling time tDRj of the DHCR slab staying in the LDj zone of Furnace 1 are determined, and the latter is larger than the former. If the time difference between the two is small, the second reactor 2 corresponding to the LDj zone
This is the time available for rolling HCR slabs staying in the LCj zone.

That is, as shown in the flowchart of FIG. 4, the rolling time tCRi of the No. 2 furnace 2 is expressed as the difference between the extraction time tj and the rolling time tDRj of the No. 1 furnace 1 as follows.

tCRj=tj−tDRj The number of extracted slabs that can be extracted for rolling using the rolling available time tCRj is determined as follows.

No. 2 furnace 2 within the extraction time tj of No. 1 furnace 1
Number of slabs that can be fired staying in the LCj zone of
Calculate NCFj and the number of rollable slabs NCRj and compare them.

The number of slabs extracted is the number of slabs that can be fired in the former
When NCFj is small, that is, when heating necks occur, the number of slabs that can be fired is set to NCFj, and when the latter number of slabs that can be rolled, NCRj, is small, that is, when heating necks occur, the number of slabs that can be rolled is set to NCFj. If the slab has no restrictions on the time in the furnace, the number of slabs that can be rolled is set to NCRj. FIG. 9 shows the number of slabs extracted in the corresponding LCj zone of the No. 2 furnace when slabs are extracted in the LDj zone of the No. 1 furnace.

The above has described the alternate rolling of ordinary steel, but the slabs extracted from the No. 2 furnace are high carbon steel (HC), stainless steel (Ni-SUS, Cr-SUS), etc., and there are restrictions on their in-furnace time. Yes, if the average extraction pitch PCRj (described later) is below the extraction pitch lower limit K of No. 2 furnace 2, the number of extraction slabs NDj of No. 1 furnace 1
is reduced to NDj×a multiplied by a constant a where a<1, and priority is given to extracting the slab from the No. 2 furnace 2.

Note that the number NCFj of slabs that can be fired and the number NCRj of slabs that can be rolled are determined by the following equations.

tj＝ _NCFj 〓 ⁱ⁼¹ Wcji／PCFj Wcji: Slab width + slab spacing tCRj＝ _NCRj 〓 ⁱ⁼¹ rci rci: Rolling time of one slab Also, the number of slabs that can be fired in Furnace 2 NCFj
The average extraction pitch PCFj for extracting the
This is determined by subroutine C shown in FIG.

Since the number NCRj of slabs that can be rolled in the No. 2 furnace 2 is extracted within the required extraction time tj of the No. 1 furnace 1, its average extraction pitch PCRj is determined by the following formula.

PCRj= _NCRj 〓 ⁱ⁼¹ Wcji/tj From the above, the number of extraction slabs and extraction pitch for Furnace No. 1 and No. 2 Furnace 2 will be determined according to the flowcharts shown in Figures 3 and 4. Therefore, even if the casting pitch of the continuous casting equipment, that is, the charging pitch of the No. 1 furnace 1 changes, and the extraction pitch or the number of extracted slabs of the No. 1 furnace 1 changes, the change in the No. 2 furnace 2 is made to compensate for the fluctuation. Since the extraction pitch or the number of extraction slabs is varied, there is no reduction in rolling capacity, and no slabs are allowed to stay in the matching zone of No. 1 furnace 1, and no slabs are rejected.

The same applies to the case where the time required for rolling the slab extracted from the No. 1 furnace varies.

Next, the extraction order and extraction time of the slabs to be extracted from the No. 1 and No. 2 furnaces are determined as follows according to the flowchart shown in FIG.

The extraction possible interval tD of the Nth slab extracted from the No. 1 furnace is determined by the following formula.

tD = WDj (N) / PDj WDj (N): Slab width of Nth slab + slab interval As a result, the time when the Nth slab can be extracted TD (N) is the extraction time of the (N-1)th slab Letting TD(N-1) be expressed as follows.

TD (N) = TD (N-1) + tD The above formula is for when there is no empty furnace in the No. 1 furnace, but if there is an empty furnace, the time to pack the empty furnace is based on a different calculation formula. ta is determined, and in this case, the extractable time TD(N) is expressed as follows.

TD(N)=TD(N-1)+ta The extractable interval tC of the Nth slab extracted from the No. 2 furnace is similarly determined from the following equation.

tC = Wcj (N) / PDFj Wcj (N): Slab width of Nth slab + slab interval As a result, the time when the Nth slab can be extracted TC (N) is the extraction time of the (N-1)th slab of
When TD(N-1), it is expressed as TC(N)=TD(N-1)+tC.

Compare the time TD (N) at which the slab can be extracted from the No. 1 furnace obtained as above with the time TC (N) at which the slab can be extracted from the No. 2 furnace and find the former time TD (N). is earlier than the latter time TC(N), the slab is extracted from the No. 1 reactor. The extraction time T(N) of the next slab extracted from the No. 1 furnace is
Scheduled extraction time Tx (N) is the extraction possible time TD
(N), the scheduled extraction time Tx(N) is set, and conversely, when the scheduled extraction time Tx(N) is earlier than the available extraction time TD(N), the available extraction time TD(N) is set. Set.

Also, the former time TD(N) is the latter time TC(N)
When the time is later than that, the slab is extracted from the second furnace. Extraction time of next slab extracted from No. 2 furnace
Tx(N) is the scheduled extraction time Tx when the scheduled extraction time Tx(N) is later than the extraction possible time TC(N).
(N), and when it is earlier, the extractable time TC(N) is set.

The scheduled extraction time Tx (N) is calculated as the (N-1) scheduled extraction time T (N-1) plus the interval until the next slab is extracted, and this interval is The number of slabs that can be rolled NCRj is the number of slabs that can be fired NCFj
When the heating net is larger than , it is determined as the extraction average interval t _{C + D} of the slabs extracted from the No. 1 and No. 2 furnaces, and is expressed as follows.

t _C+D = W(N-1)/PDj+PCFj W(N-1): WDj(N-1) or Wcj(N-1) From this, the scheduled extraction time Tx(N) is expressed as follows.

Tx (N) = T (N-1) + t _{C + D} T (N-1): (N-1) scheduled extraction time When the number of slabs that can be rolled NCRj is smaller than the number of slabs that can be fired NCFj,
The scheduled extraction time Tx(N) is expressed as follows.

Tx (N) = T (N-1) + tR (N-1) tR (N-1): (N-1) Time required for main rolling From the No. 1 and No. 2 furnaces obtained as above The extraction times of the slabs are shown in FIGS. 12 and 13. In addition, Fig. 10 shows the case of heating neck.
Figure 11 shows the case of Milnek.

Effects of the Invention As described above, the present invention is made by making the ratio of the number of slabs extracted from the No. 1 and No. 2 furnaces variable. By prioritizing the extraction of slabs from the furnace, problems such as waiting for DHCR slabs to be charged or removal from the line can be resolved.
Therefore, compared to the conventional method where the extraction number ratio is fixed,
The rolling ratio of DHCR slab can be increased,
In addition, the insufficient HCR and CCR slabs are extracted according to the number of DHCR slabs extracted, and the number of slabs with the rolling capacity is always extracted from the No. 1 and No. 2 furnaces, so it is possible to increase the operating rate of the rolling mill. .

According to the present invention, even for steel types for which there are restrictions on furnace time, it is possible to deal with fluctuations in charging pitch and rolling pitch and extract them with priority, so that alternate rolling with different steel types is possible. It became like that.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the heating device used in the method of the present invention, Figure 2 is a schematic diagram of the No. 1 furnace, Figures 3 to 5 are flow diagrams, Figures 6 to 8 are explanatory diagrams, and Figure 9 is Explanatory diagram of slabs extracted from Furnace No. 1 and Furnace No. 2, No. 10
Figure 11 is a graph showing the extraction order during heating neck, Figure 11 is a graph showing the extraction order during rolling neck, and Figure 12 and 13 are graphs showing the extraction order during rolling neck.
The figure shows an explanatory diagram of a conventional example. 1... Furnace No. 1, 2... Furnace No. 2, 4... Charger, 7... Rolling mill.

Claims (1)

[Claims] 1 Equipped with a first heating furnace that heats the hot piece slabs supplied from the continuous casting equipment and a second heating furnace that heats the hot piece slabs and/or cold piece slabs supplied from the slab yard, An alternating rolling system in which extraction is alternately extracted from each heating furnace and rolled, characterized in that the extraction operation of each of the heating furnaces is performed such that the extraction ratio between the first heating furnace and the second heating furnace is variable. How to operate a heating furnace in a rolling system.