JPS596324A - Charging method of hot bloom into reheating furnace - Google Patents

Abstract

PURPOSE:To make the reduction of the temperature drop of cast bloom due to increase of temporary stock amount of cast bloom accompaying the increase of hot bloom amount possible, by a method wherein cast blooms are manufactured by arranging a part of the manufacturing period to lap with another one when cast blooms from plural cast bloom manufacturing units are continuously charged into a specified reheating furnace as hot one. CONSTITUTION:Periods for manufacturing cast bloom of continuous casters A and B are lapped and, for example, blooms are charged into a reheating furnace in sequence of casting unit and rolled so that temporary stock of lapped part may be disposed within the same casting unit. By designating a casting time of one casting unit of caster A (hereinafter) referred to as CC cycle) to be T and by designating the lap time between this cycle and the previous CC cycle of caster B to be L, the lap ratio R is defined as given by a formula. When R=0%, the immediate charge of cast bloom to reheating furnace and the unit power consumption is very high. When R is raised, line efficiency is increased, unit power consumption being decreased, fuel consumption being deteriorated according to the increase of temporary stock amount at the other side and its affect is decreased by reducing CC cycle amount (multiple conti-continuous casting amount). From these connelations, the optimum conditions are selected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous casting equipment or a heating furnace equipment for hot slabs in which slabs such as cast steel slabs manufactured by blooming are charged into a heating furnace of a rolling line in a high temperature state. This relates to the rolling process and aims to reduce energy consumption during rolling by effectively utilizing the heat possessed by slabs.

In order to reduce the unit consumption of heat materials in the heating furnace of a rolling line, continuously cast or bloomed slabs are charged into the heating furnace while still in a high temperature state.

Most of the variable costs on a rolling line are accounted for by the fuel cost for the heating furnace and the electricity cost for the rolling equipment, but each has a corresponding relationship with the line efficiency, and the general trends are shown in Figures 1 and 2. It can be expressed as A hot piece is usually inserted between a cold piece and a cold piece as a hot piece. The relationship between the amount of hot flakes per chance and the energy cost in rolling is as shown in Figure 3. When the amount of hot flakes is small, the preceding cold flakes become a heating furnace constraint within the same furnace, and after the preceding cold flakes are extracted, the succeeding cold flakes become a heating furnace constraint, and the hot flakes become a heating furnace constraint. Material line efficiency is limited by cold strip material.

Therefore, when the amount of hot flakes per chance is increased, the heating furnace constraints on hot flakes are relaxed as shown in Figure 2, which makes it possible to improve line efficiency and contributes to lower unit power consumption. As a result, the sum of fuel cost and electric power cost (hereinafter referred to as energy cost) is reduced. For this reason, efforts are being made to increase the amount of hot flakes per chance in order to efficiently operate hot flake charging. However, as the speed of heating sheet materials increases, the combustion capacity of the heating furnace becomes a constraint, and the line efficiency comes to be limited by the heating furnace.

On the other hand, as the amount of hot slabs per chance increases, as shown in Figure 4, the amount of temporary storage before loading into the heating furnace increases, and accordingly, the temporary storage time becomes longer, and the temperature of the slab increases. As the charging temperature decreases, the fuel consumption rate rises and the energy cost also increases (in the figure, numeral 1 indicates slabs). In order to improve this technology, improvements have been made to heat retention methods that exclusively reduce the drop in temperature of the slab during temporary storage. However, it has always been difficult to achieve complete heat insulation, and the trend shown in Figure 3 cannot be changed, so there is a limit to the effective use of thermal strip charging.

This invention was made in consideration of the above-mentioned problems, and uses a plurality of pieces of slab manufacturing equipment and operates them so that the pieces of slab are manufactured by partially overlapping each other. Thus, the heating furnace charging method for hot slabs is characterized in that the slabs manufactured by each of the plurality of slab manufacturing facilities are continuously charged into a specific heating furnace. has.

This invention will be explained in detail below.

A first feature of the present invention is to use a plurality of slab manufacturing facilities and to operate them so that the slabs are manufactured so as to partially overlap each other.

In conventional hot flake charging, as shown in Figure 4, the amount of hot flakes per chance is increased without paying attention to the chronological relationship between the slab manufacturing process and the rolling process. It's here. The present invention was made by paying attention to this chronological relationship in order to carry out the most efficient hot plate charging. Although the present invention is based on a plurality of pieces of slab manufacturing equipment, in the following description, two lines of continuous casting equipment A will be used for explanation purposes.

Think about B. In the present invention, as shown in FIG. 5, the production times of continuous casting equipment A and continuous casting equipment B are made to overlap, and the slabs are charged into a heating furnace in the order of casting units, for example, and the temporary placement of the lap portions is performed at the same time.
Rolling is performed to eliminate the problem within the casting unit. By providing this condition, which was not considered in the past, it is possible to assemble a large amount of heat flakes per chance with a small amount of temporary storage. This made it possible to reduce the temperature drop of the slab due to the increase in the amount of temporary hot slab storage.

The effect of this wrap will be explained in more detail.

As shown in Fig. 6, the casting time of one casting unit (temporarily referred to as CC cycle) is T time, and the corresponding CC cycle and (
(depending on other equipment) @Parallel casting (lap) time with CC cycle is L hours, and wrap rate R is defined as R=L/T x 100. When the wrap ratio is -0%, it means that the cast billet is immediately charged into the heating furnace.By doing this, no temporary storage occurs, so if you look only at the fuel consumption rate, it is the most efficient. This is a good method for charging hot pieces. However, the continuous casting equipment capacity is usually extremely low compared to the rolling line capacity, and when the wrap ratio is 0%, the casting efficiency immediately becomes the line efficiency, so the electric power consumption is extremely high. Therefore, increasing the wrap rate increases line efficiency and produces the effect of reducing power consumption. On the other hand, as the wrap rate increases, the fuel consumption rate worsens because the temporary storage amount increases, but when viewed at the same wrap rate, the effect becomes smaller as the CC cycle amount decreases. The above relationships are shown in Figure 7 α) to (d
). Figure 7 shows the temperature drop characteristics of the slab and the heating furnace characteristics (
(Fig. 2) and rolling power characteristics (Fig. 1) can be easily drawn quantitatively. From Figure 7, we can immediately find the minimum cost point 14.
It is necessary to consider the efficiency limit due to production capacity and the limit that can be wrapped in multiple slab manufacturing equipment cycles. C.C.
A larger cycle amount (i.e., multiple casting amount) is more effective in terms of efficient operation of continuous casting equipment, but from Figure 7, a smaller one is better, and it should be determined by considering both benefits. can. Once the CC cycle amount is determined, the optimal wrap rate will also be determined.

Note that under conditions where the scale loss generated during temporary placement cannot be ignored, it is also possible to find optimal conditions in addition to the cost evaluation item.

The line efficiency for carrying out the present invention can be basically considered as follows. In order to prevent the temporary storage amount from being accumulated, line efficiency is set to eliminate the temporary storage amount at the time of lapping in the corresponding CC cycle. That is, as shown in FIG. 8, if the line efficiency N is high, it will not affect the next CC cycle.

However, in actual operation, some of the planned CC cycles are rejected and the rolling line is stopped, so the actual C
If efficiency is set by determining the C cycle amount W, CC cycle casting time T, lapping time, and line progress adjustment time α, there will be no accumulation of temporary storage amount and slabs can be charged continuously. can.

The lap rate can also be set by, for example, for sizes where there is a limit to the efficiency in rolling, the limit rate is set to N, and the wrap rate is determined by N - N c R'' - (Nc: casting efficiency). This function can be used to adjust the efficiency balance of the rolling line.

The effects of the present invention are shown in FIG. 9 in comparison with the conventional method.

It is considered that the method of the present invention shown in FIG. 9 was carried out with an appropriate CC cycle amount and wrap rate. In the present invention, as shown in FIG. 5, the CC cycle is simply wrapped and repeated, so even if the amount of heat flakes is increased, the charging temperature is maintained constant. Furthermore, since the material is charged into the heating furnace at a high temperature, the line efficiency, which is a constraint on the heating furnace, becomes higher than in the past, and as a result, a large reduction in energy costs can be expected as shown in FIG. The method of the present invention does not require much capital investment, and can easily achieve optimal hot-piece charging by simply analyzing the optimal lapping conditions in advance and incorporating the lapping ratio when creating casting plans and rolling plans.

A second feature of the present invention is that the slabs manufactured by each of the plurality of slab manufacturing facilities are continuously charged as hot slabs into a specific heating furnace.

Hot rolling lines generally reheat and roll slabs, and for this reason, the line has a heating furnace, but there are restrictions in the furnace design and the type of repair between the rolling mill and heating furnace. difference,
Alternatively, in order to enable furnace operation according to productivity, several furnaces are designed to correspond to the rolling capacity.

Therefore, in a hot rolling line with several continuous heating furnaces, since the total heating capacity of the number of furnaces used corresponds to the hot rolling functional capacity, The slabs are sequentially and alternately charged into multiple heating furnaces, and
They are extracted and rolled in that order.

The present invention relates to a method of charging hot pieces by wrapping the casting periods of a plurality of continuous casting equipment, which has a large energy-saving effect. This was done to prevent this.

The present invention was obtained from understanding the characteristics of a heating furnace by charging high-temperature cast slabs. The basic unit of fertilizer in a heating furnace is related to the efficiency of the heating furnace, as shown in FIG. That is, the higher the temperature of the charged slab, the lower the fuel consumption rate becomes, and the minimum unit consumption point and the heating furnace efficiency limit move toward the higher efficiency side.

This is because the heat capacity provided by the heating furnace decreases as the temperature of the charged slab increases. A general example of charging temperature and heating furnace efficiency limit is shown in FIG. When charging high-temperature hot flakes, it is clear that the number of heating furnaces can be reduced compared to when heating cold flakes. Since charging is usually carried out at a temperature of 600° C. or higher, it is possible to reduce the number of furnaces by half.

In the present invention, the heating furnaces are divided into two groups, and one CC cycle is charged to each furnace group consecutively (if there are two or more furnace groups, alternately within the furnace group). The following explanation assumes that two heating furnaces are operated. In the comparative method, as shown in Fig. 12, in order to maintain the rolling order in the casting order, the material is temporarily stored in the yard, and after the previous CC cycle material has been completely discharged, the subsequent CC cycle material is discharged and the conveyance order is changed. They need to be arranged in order. In the present invention, pretreatment such as cutting is not performed, and the casting is carried out in the order of X. Therefore, when wrapped and cast, the previous CC cycle material and the subsequent CC cycle material are
The items are transported in a mess. In the comparative method, the hot pieces transported in this state are charged alternately into the heating furnace, but in the present invention, for example, the preceding CC cycle (A-CC') is charged into the (A) furnace, and the subsequent cycle (B-CC) is charged into the heating furnace. (b) Continuously charging one CC cycle f:1 furnace while separating the furnaces. This is explained in detail as shown in FIG. 13. (a) Once each slab of the previous CC cycle begins to be charged into the furnace, it is then charged into the heating furnace while the hot slabs are being conveyed (first
Figure 3(a)). If the casting efficiency is Nc, the heating furnace efficiency N at this time is N=Nc. When the final slab X of the previous CC cycle is (a) charged into the furnace, (b)
In the furnace, while the hot pieces are being conveyed, charging for the subsequent CC cycle is carried out, resulting in a state as shown in Fig. 13, etc.). After this, (b) the slab is transferred into the furnace while being charged at N = Nc, while (b) the slab is extracted and rolled in the furnace, and the slab X is extracted. When the final slab Y of the subsequent CC pusile reaches the extraction end of the furnace (b), it is possible to maintain the rolling order in the casting order and to continue rolling. This means that the available amount in the reactor is WtOn, CC
If the cycle amount is cton and the lap rate is R (R = L (casting amount at casting lap) / C), then from the state shown in Figure 13 (b), (a) the furnace will be operated at an efficiency of It becomes executable. Note that such conveyance of slabs within the furnace is fully possible if a walking beam is employed in the continuous heating furnace.

According to the above-mentioned charging method of the present invention, the rolling order of the slabs does not need to be changed, and as shown in the comparative method in Figure 12, multiple slabs can be rolled without temporarily placing the slabs and adjusting the charging order. It becomes possible to roll slabs that have been lapped and cast from series in the order of casting. Moreover, the method of the present invention not only prevents the heat loss of high-temperature slabs due to temporary storage, but also doubles the heating furnace efficiency per furnace when high-temperature charging is performed, as shown in Figure 14. Yes, the fuel consumption rate will further decrease.

[Example 1] The test was carried out at a hot rolling mill connected to two lines of continuous casting equipment.

Prior to implementation, we analyzed the temperature drop characteristics, heating furnace characteristics, and rolling power characteristics of the cast steel slab, and found that the CC cycle amount was 20.
At 00t, pattern (c) in Figure 7 is formed, and below that, it is a turn in Figure 7 (a) (b) -'', making it clear that taking as long as possible will reduce energy costs. became.

Since the CC cycle amount was determined to be 1000 t due to the effects of continuous casting and constraints on rolling section execution, the maximum lag ratio under this condition was 35%.

The implementation results are shown in Table 1. Looking at this, it can be seen that in the conventional method, the effect of increasing the amount of heat particles per chance appears up to 6000, but the effect is lost when it reaches 5000. On the other hand, in the present invention, the energy cost is significantly reduced compared to the conventional method under the so-oo-t condition, and, as originally expected, it achieves a remarkable effect under the maximum lap condition.

[Example 2] This was carried out by charging hot steel billets into a two-line continuous casting facility and a hot strip mill having two furnaces. In implementation, I
The CCCC cycle amount was set at 000 tons, and 4CC cycles were wrapped at three levels: 5%, 15%, and 25% under the same conditions as the comparative method (see FIG. 12) and the method of the present invention.

The implementation results are shown in Table 2. In the method of the present invention, there is no need to handle the slab in the temporary storage pool, there is no temperature drop in the slab due to temporary storage, and due to the characteristics of the heating furnace,
] The fuel consumption rate has been reduced. In the comparative method, the higher the wrap rate, the longer the temporary storage time, which worsened the fuel consumption, but in the method of the present invention, it was further reduced due to its high efficiency.

Although the present invention is based on the premise of casting using a plurality of continuous casting equipment, it is of course possible to include blooming equipment. In addition, although the present invention has been described as hot billet charging, even if the billet is produced at a high temperature to the point where heating is not required, efficiency can be increased by lapping and casting multiple continuous casting equipment. Therefore, even if the heating furnace is charged using the method of the present invention and combustion in the heating furnace is stopped, the effects of the present invention can be obtained.

As explained above, in the present invention, the heat possessed by the slab can be effectively used, and the energy consumption during rolling can be reduced.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the power characteristics of rolling, Figure 2 is a diagram showing the temperature drop characteristics of slabs and heating furnace characteristics, and Figures 3 and 9 are diagrams showing the relationship between the amount of hot slabs and energy costs, etc. Figure shown, 4th
Fig. 5 and Fig. 5 are diagrams showing the relationship between slabs obtained from two continuous casting facilities and the temporary placement amount, Fig. 6 is an explanatory diagram of the lag ratio, and Fig. 7 (a) to (d) are A diagram showing the relationship between CC cycle amount and wrap rate, Figure 8 is an explanatory diagram of line efficiency, Figure 10
Figure 11 shows the relationship between heating furnace efficiency and fuel consumption rate.
The figure shows the relationship between the heating furnace charging temperature and the heating furnace efficiency limit, Figure 12 is a diagram for explaining the heating furnace charging mode, etc. of the comparative method and the present invention method, and Figure 13 (a) (b) is a diagram illustrating the heating furnace charging timing, and FIG. 14 is a diagram showing the heating furnace efficiency per furnace. Applicant Nippon Steel Tube Co., Ltd. Agent Keitabe Tsutsumi and 1 other person (b) Y Figure 14 Procedural amendment (method) % formula % 1. Indication of case Patent application No. 111434 1977 2. Name of invention Method of charging pieces into a heating furnace 3, relationship with the case of the person making the amendment Patent applicant address: 1-2 Marunouchi-chome, Chiyoda-ku, Tokyo, Japan) Nippon Kokan Co., Ltd. Representative: Minoru Kaneo 4, Agent 7. Contents of amendment We will submit a detailed description as shown in the attached sheet.

Claims (1)

[Scope of Claims] A plurality of slab production facilities are used and operated in such a manner that slabs are produced partially overlapping each other, and thus each of the plurality of slab production facilities The manufactured slab is heated to a specific heating furnace. A method for charging hot pieces into a heating furnace characterized by continuous charging.