JPH07241610A - Operating method for synchronizing continuous casting with hot rolling stage - Google Patents

Abstract

PURPOSE:To provide an operating method for synchronizing a continuous casting with a hot rolling stage by which the slab of an undecided result of analysis of molten steel is smoothly rolled. CONSTITUTION:When the result of analysis of the molten steel at the time of casting in continuous casting is undecided until the completion of slab heating, rolling is executed based on a rolling command that is prepared by using the target constituent value of the slab 4, thereafter, the progress of process is reserved and, when the result of analysis of the molten steel is decided, the rolling command is again prepared and a rolling temp. command value is determined. Acceptance decision is executed by the difference from the rolling temp. command value in rolling command by the target constituent value. By progressing the process to the next stage at the time of being suitable, and continuing the reservation of the progress of process at the time of being unsuitable, operation highly synchronized with the continuous casting and the hot rolling stage is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of synchronizing continuous casting and hot rolling.

[0002]

2. Description of the Related Art In recent years, hot rolling mills have adopted so-called direct rolling, in which a slab produced by continuous casting is charged into a heating furnace in a hot state for the purpose of energy saving and cost reduction due to shortening of processes. The continuous casting and hot rolling process are being synchronized. That is, as shown in FIG. 4, in continuous casting, molten steel from a ladle 1 is cast by a continuous casting machine 2 and then cut into a slab 4 of a predetermined length by a cutting torch 3. This slab 4 is a carrier truck 5 having a heat retaining function.
It is carried to a hot rolling plant by a heating furnace 6, charged into a heating furnace 6, heated to a predetermined temperature in the heating furnace 6, and then rolled into a strip having a predetermined size in a hot rolling line 7 including a rough rolling machine and a finishing rolling machine. It is taken up by coiler 8.

In most cases, such process control of the slab 4 is almost automatically performed by a computer, and in particular, the rolling instruction to the hot rolling line 7 depends on the chemical composition and the casting condition determined at the time of continuous casting. Generally, the slab is created by the time the slab reaches the front of the heating furnace, and the slab is output according to the contents of the assembly. Conventionally, such a synchronized operation is disclosed in, for example, Japanese Patent Laid-Open No. 3-29853.
The gazette proposes how to cut slabs,
There is no technology disclosed about the above-mentioned method of advanced synchronization in which the steel components are added.

In particular, the chemical composition value of the continuous cast slab is an important control item for quality control, and not only is it used to determine the conformity of the slab, but its actual value is also used to determine the temperature condition of the rolling instruction. There is. Therefore, in the conventional slab for hot rolling, it is general to suspend the execution of rolling until the analysis actual value is known. Usually, the molten steel analysis value in continuous casting is obtained by analyzing a sample taken at the time when approximately 50% of the molten steel in the ladle 1 is cast. This analysis value is
It is usually found when the slab is cut by the cutting torch 3.

However, when a high speed continuous casting machine or a narrow slab is cast, for example, the analysis value may be determined after cutting with the cutting torch 3. In such a case, since the rolling instruction to the normal hot rolling process is premised on that the molten steel analysis is known, the slab for which the molten steel analysis is not known is suspended for rolling. The reason for this is that the continuous casting-hot rolling was originally allowed to be caused by a temporal discontinuity that is unavoidable in terms of process.

[0006]

However, for the purpose of further energy saving, for example, slab transfer between the continuous casting machine 2 and the heating furnace 6 is carried out in 5 to 25 minutes (on average within 15 minutes). In response to a request for a highly synchronized operation mode for speeding up the trolley 5, if the slab is removed from the rolling schedule because the molten steel analysis is unknown, the rolling cycle is not established and synchronization is achieved. It is a problem because it is a fatal obstacle to maintaining the operation.

The present invention has been made to solve the problems of the prior art as described above, and synchronization between continuous casting and hot rolling process capable of smoothly rolling even a slab whose molten steel analysis is unknown. The purpose is to provide a method of operation.

[0008]

According to the present invention, a slab cast by continuous casting is conveyed in a hot state and directly heated in a heating furnace, and then a slab having a predetermined size is hot-rolled according to a rolling instruction. In the method of operating by synchronizing the continuous casting and hot rolling step of rolling into strip, when the analysis result of molten steel at the time of casting in continuous casting by the end of heating of the slab is unknown, the target composition of the slab Rolling is performed based on the rolling command created using the value, then the process progress is suspended, and when the analysis result of the molten steel is found, the rolling command is recreated to obtain the rolling temperature command value, and the target component The continuous casting and hot rolling are characterized by making a pass / fail judgment based on the difference between the rolling temperature command value and the rolling temperature command value, and advancing to the next process when it conforms, and continuing the process progress suspension when it does not conform. This is an operation method that is synchronized with the process.

[0009]

[Operation] The procedure of the present invention will be described below with reference to the flowchart of FIG. If the composition analysis value of molten steel is unclear at the time of making the rolling command when the slab reaches the front of the heating furnace, the target value (target at the time of issuing command for molten steel) Component) is used to create a rolling instruction, and rolling is executed based on this rolling instruction. After the rolling is completed, the progress of the next process of the product coil is suspended and the process is waited until the analysis value is determined. When the molten steel analysis value is known, the compatibility of the chemical composition of the slab is judged. Create a rolling command again based on the actual components. The difference between the individual rolling temperature conditions (finishing rolling temperature and winding temperature) of the re-rolling instruction with the actual component and the rolling instruction with the target component is compared. As a result of the comparison, when it is determined that the product coil is conforming, the product coil is automatically released from the hold, and the process is advanced to the next step, and the product coil which is determined to be non-conformant changes the state to "clear hold" and outputs the message .

By performing these series of processes by using a computer system, a highly synchronized operation between the continuous casting and the hot rolling process can be performed. In addition, the slab is loaded into the heating furnace in an undetermined state,
If the analytical value is found during the residence in the furnace (usually 30 to 200 minutes), the conformity determination at the above step and the re-creation of the rolling instruction of the step are performed at that time, and the instruction temperature of the step is corrected. You can do this. In the case of a slab determined to be non-conforming at this point, a matching order is immediately searched, and if a matching order is found, the allocation destination is changed.

[0011]

EXAMPLES An example of the present invention will be described below. For example, when it is desired to obtain a certain mechanical property as in the case of structural hot-rolled ordinary steel, the setting values of the finish rolling temperature and the winding temperature in the hot rolling process are determined by the actual component values of the slab to be rolled. For example, the winding temperature of Nb-containing low alloy steel is determined by the actual Nb content, and the winding temperature of strength-guaranteed ordinary steel is determined by the so-called carbon equivalent.

FIG. 2 shows a structure of the hot-rolled ordinary steel for the structure according to the present invention (as components, C: 0.02 to 0.08%, Mn; 0.15 to 0.90%, Si;
0.20% or less, P; 0.030% or less) is a frequency distribution of the winding temperature difference. That is,
This figure shows the distribution of the difference between the coiling temperature using the target component values and the coiling temperature using the actual analysis values after the analysis results are known because the molten steel analysis is unknown. It can be seen that, for most product coils, the difference in the command value for the coiling temperature is within ± 20 ° C.

FIG. 3 shows an example of the degree of influence of tensile strength, which is one of the mechanical properties of the chemical composition of hot-rolled ordinary steel and the rolling temperature conditions (finishing rolling temperature and winding temperature). However, the evaluation function of the tensile strength F (kgf / mm ² ) at that time is as in the following equation, and the average value γ = 0.965 and the standard deviation σ = 1.005. F = 42.2 + 0.54C + 0.23Si + 0.07Mn- 0.008T F -0.01
T _C Here, T _F is the finishing temperature (° C.), and T _C is the winding temperature (° C.).

The degree of influence of the hot rolling conditions on the tensile strength is about 0.2 kgf / mm ² at a winding temperature difference of 20 ° C., which is practically acceptable. It is empirically expressed by the following function. Further, in the figure, the tensile strength is strongly influenced by the chemical components (C, Si, Mn), but the target value and the actual value of these components are almost the same.

[0015]

As described above, according to the present invention,
Even if the chemical composition of the slab is unknown, rolling can be carried out, so it is possible to operate in a highly synchronized process between continuous casting and hot rolling, which saves energy. It is possible to contribute not only to improvement but also to increase in productivity.

[Brief description of drawings]

FIG. 1 is a flow chart showing the procedure of the present invention.

FIG. 2 is a characteristic diagram showing a winding temperature difference when the present invention is applied to a structural hot rolled carbon steel.

FIG. 3 is a characteristic diagram showing an example of the degree of influence of chemical components and rolling temperature conditions on tensile strength.

FIG. 4 is a side view illustrating a synchronized operation of continuous casting and a hot rolling process.

[Explanation of symbols]

 1 ladle 2 continuous casting machine 3 cutting torch 4 slab 5 carrier 6 heating furnace 7 hot rolling line 8 coiler

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B21B 1/46 B

Claims (2)

[Claims] 1. A continuous casting and heat treatment in which a slab cast by continuous casting is conveyed in a hot state and directly heated in a heating furnace, and then rolled into a strip of a predetermined size in a hot rolling line based on a rolling instruction. In the method of operating in synchronization with the rolling process, if the analysis result of molten steel at the time of casting in continuous casting is not known by the end of heating the slab, the rolling instruction created using the target component value of the slab Rolling is performed based on the above, and then the process progress is suspended, and when the analysis result of the molten steel is found, the rolling command is recreated to obtain the rolling temperature command value,
A continuous casting characterized by performing a pass / fail judgment based on a difference between the rolling temperature command value in the rolling command at the target component value and advancing to the next process when conforming, and continuing the process progress suspension when not conforming. And the method of synchronizing the hot rolling process. 2. When the analysis result of the molten steel is known before the heating of the slab is completed, the rolling command is re-created based on the analysis value, and the rolling command temperature is corrected. A method for synchronizing the continuous casting and the hot rolling process described.