JPH05263153A - Method for controlling extraction in rotary hearth type heating furnace - Google Patents

Abstract

(57) [Abstract] [Purpose] When extracting billets from a rotary hearth furnace, the fuzzy theory is used to determine the extraction pitch, so that extraction is possible even under unsteady conditions. An object of the present invention is to provide an extraction control method of a rotary hearth type heating furnace that can be controlled and can stabilize the quality of steel pipes. [Structure] The billet 1 is heated in the rotary hearth heating furnace 2, and the billet 1 after heating is extracted from the rotary hearth heating furnace 2 and rolled by the rolling mills 3, 4, 5, 6, 7. When manufacturing a seamless steel pipe by the method, the heating temperature error, which is the difference between the calculated value and the target value when the billet 1 is heated from the rotary hearth type heating furnace 2, and the rolling pitch fluctuation in the rolling process are The extraction pitch is calculated using the fuzzy theory which is used as the condition variable, and the rotary hearth heating furnace 2 is used according to the calculated extraction pitch.
The extraction timing of the billet 1 from is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to an extraction control method for a rotary hearth type heating furnace which is a heating step in a seamless steel pipe manufacturing process.

[0002]

2. Description of the Related Art FIG. 1 is a schematic view showing a manufacturing process of a seamless steel pipe. Reference numeral 1 shown in FIG. 1 (a) indicates a billet as a material for a seamless steel pipe. First, the billet 1 is heated by a heating furnace 2 as shown in FIG. 1 (b).
After being heated up to a predetermined temperature by means of, it is extracted to the outside of the heating furnace 2, pierced and rolled by the piercer 3 as shown in FIG. 1 (c), and shown below in FIG. 1 (d). Elongator 4, plug mill 5 shown in Figure 1 (e), reeler 6 shown in Figure 1 (f), sizer 7 shown in Figure 1 (g) The finished product is a seamless steel pipe.

The rotary hearth type heating furnace 2 is a disk type furnace,
The purpose is to heat the charged billet 1 while gradually rotating it and bake it to a predetermined heating temperature before the billet 1 reaches the extraction port.

In recent years, computer control is generally used for heating control in the rotary hearth type heating furnace 2. The computer used to control the heating of the rotary hearth type heating furnace 2 calculates the temperature set value of each part in the furnace based on various actual values such as billet size, charging method, heating target temperature, extraction actual pitch, etc. According to this result, heating control of the rotary hearth type heating furnace 2 is performed.

On the other hand, with respect to the extraction of the billet 1 from the rotary hearth type heating furnace 2, the site worker is in various situations, for example, the situation of the rolling line, which is schematically shown in FIG. Comprehensively judge the degree of baking, etc., and perform the extraction work according to the manual based on the judgment result.

[0006]

Since various troubles occur in the rolling line as described above, the timing for extracting the billet from the heating furnace is determined by the site worker in various situations as described above, for example, in the rolling line situation. Therefore, the extraction pitch from the rotary hearth type heating furnace is determined by comprehensively judging the degree of baking of the billet, etc., based on experience and intuition.
Therefore, even with billets of the same size, the extraction pitch varies depending on the operator depending on the line condition at that time, and this value may not be appropriate. The quality of the steel pipe is determined by various factors, but the temperature during rolling is also a major factor, and if the extraction pitch is inappropriate, the temperature during rolling becomes unstable and the inner and outer surfaces of the steel pipe are flawed. It will cause the like.

The present invention has been made in view of the above circumstances, and when a billet is extracted in a rotary hearth type heating furnace, a fuzzy theory is used to obtain an extraction pitch to obtain an unsteady state. It is an object of the present invention to provide an extraction control method for a rotary hearth-type heating furnace, which enables extraction control to be adapted to each situation even if there is any, and which can stabilize the quality of steel pipes.

[0008]

A method for controlling extraction of a rotary hearth type heating furnace according to the present invention comprises heating a tube material in a rotary hearth type heating furnace and heating the tube material from the rotary hearth type heating furnace. When manufacturing a seamless steel pipe by extracting and rolling in a rolling process, the heating temperature error and rolling that are the difference between the calculated value and the target value of the heating temperature of the pipe material at the time of extraction from the rotary hearth furnace It is characterized in that the extraction pitch is obtained by using a fuzzy theory in which the rolling pitch fluctuation in the process is used as the antecedent variable, and the extraction timing of the pipe material from the rotary hearth heating furnace is controlled according to the obtained extraction pitch.

[0009]

In the extraction control method of the rotary hearth type heating furnace of the present invention, the extraction timing of the billet from the rotary hearth type heating furnace is determined by using the fuzzy theory. Even in the unsteady state, it is possible to obtain the output instruction of the extraction pitch from the rotary hearth type heating furnace of the billet that suits the state at each time point. By extracting and supplying the billet to the next rolling step, it becomes possible to improve the quality of the steel pipe as the final product.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments thereof.

FIG. 1 is a schematic view showing a manufacturing process of a seamless steel pipe to which the extraction control method for a rotary hearth type heating furnace according to the present invention is applied.

Reference numeral 1 shown in FIG. 1 (a) indicates a billet as a material of a seamless steel pipe. As shown in FIG. 1 (b), the billet 1 is first heated to a predetermined temperature by the heating furnace 2 and then extracted to the outside of the heating furnace 2 as shown in FIG. 1 (c). Like piercer 3
Piercing and rolling by means of the following, elongator 4 shown in FIG. 1 (d), plug mill 5 shown in FIG. 1 (e),
The reeler 6 shown in FIG. 1 (f) and the sizer 7 shown in FIG. 1 (g) are finished to predetermined dimensions by the respective rolling mills to complete the product as a seamless steel pipe.

The rotary hearth type heating furnace 2 is a disk type furnace,
The purpose is to heat the charged billet 1 while gradually rotating it and bake it to a predetermined heating temperature before the billet 1 reaches the extraction port. For this purpose, in the method of the present invention, a rotary hearth type heating furnace 2 is used by a computer.
The temperature is controlled based on the grasp of the position of the billet 1 inside.

In addition, the computer controls the heating temperature error of the billet 1 reaching the extraction port of the rotary hearth type heating furnace 2 (deviation from the target temperature) and the rolling control of each mill. An appropriate extraction timing is calculated based on the rolling pitch information, and the extraction of the billet 1 from the rotary hearth heating furnace 2 is controlled according to the detection result. In the present invention, the fuzzy theory is applied when calculating the extraction timing of the billet 1 from the rotary hearth type heating furnace 2 by this computer.

FIG. 2 is a functional block diagram of a computer used for controlling the rotary hearth type heating furnace 2. In FIG. 2, reference numeral 10 is a computer for controlling the heating of the rotary hearth type heating furnace 2 and the extraction of the billet 1 from it (hereinafter referred to as the heat extraction computer 10), and the reference numeral 20 is shown in FIG. It is a computer that controls each rolling mill 3, 4, 5, 6, 7 (hereinafter referred to as rolling line computer).

The heat extraction computer 10 is provided with functional blocks such as a rolling pitch calculator 11, a heating control calculator 12, and an extraction timing calculator 13.

Each of the rolling mills 3, 4, 5, 6, 7 sent from the rolling line computer 20 is sent to the rolling pitch calculation unit 11.
Control information is input, and the rolling line pitch is calculated based on these pieces of information. The heating control calculation unit 12 heats the billet 1 to a predetermined target temperature on the basis of the rolling line pitch calculated by the rolling pitch calculation unit 11 and the billet material specifications and various actual values in the furnace which are input in advance. The temperature control of the rotary hearth type heating furnace 2 is performed as described above, and the heating temperature error which is the difference between the actual temperature and the target temperature of the billet 1 extracted from the rotary hearth type heating furnace 2 is extracted. Output to 13. As described above, the extraction timing calculation unit 13 inputs the rolling line pitch from the rolling pitch calculation unit 11 and the heating temperature error of the billet 1 extracted from the rotary hearth heating furnace 2 from the heating control calculation unit 12. So
The fuzzy control rule is applied to these pieces of information to calculate the optimum extraction pitch output value after heating, and the extraction pitch command value is output to the extractor of the rotary hearth heating furnace 2.

The calculation of the optimum extraction pitch output value by the extraction timing calculator 13 will be described below.

The extraction timing calculation unit 13 calculates the extraction pitch output value by the extractor of the rotary hearth type heating furnace 2 based on the following equation (1).

P = Pc + α (Pc−Pa) + β (Tc−T) (1) where P: current extraction pitch Pc: standard extraction pitch of extraction target material Pa: rolling pitch actual value Tc of rolling line : Target extraction heating temperature T: Extraction billet calculated heating temperature

When ΔP = Pc-Pa and Δt = Tc-T in the equation (1), the above equation (1) becomes the following equation (2). P = Pc + α · ΔP + β · Δt (2) where α, β: Coefficients determined by applying fuzzy control rule The extraction timing calculation unit 13 determines the optimum extraction pitch output value based on the above formula (2). Is calculated.

The fuzzy control rule is generally expressed by the following equation (3). R _K : if x ₁ is A _K1 and x ₂ is A _K2 then y ₁ is B _K1 and y ₂ is B _K2 ... (3) where K: control rule number (K = 1, 2, 3 ... ) x _1, x _2: antecedent variables y _1, y _2: consequent variables _{A K1, A K2, B K1} , B K2: consequent variables

In the present invention, the extraction pitch change ΔP,
The heating temperature change Δt is defined as the antecedent variables x _{1 and} x ₂ , and the coefficient α,
Let β be the consequent variables y _{1 and} y ₂ . Therefore, the control rule Rα ^K for the Kth coefficient α and the control rule Rβ ^K for the Kth coefficient β are expressed by the following equations (4) and (5).

Rα ^K : if ΔP is A _K1 and Δt is A _K2 then α is B _K1・ ・ (4) Rβ ^K : if ΔP is A _K1 and Δt is A _K2 then β is B _K2・ ・ (5)

The consequent variables A _K1 , A _K2 , B _K1 and B _K2 are expressed using seven states used in the usual fuzzy theory. Table 1 below shows the seven states.

[0026]

[Table 1]

The states of the consequent variables A _K1 , A _K2 , B _K1 and B _K2 can of course be subdivided into seven or more ways shown in Table 1 above, or conversely they can be coarse. It is possible.

Next, Table 2 below shows the control rules for α, and represents B _K1 when the states shown in Table 1 are substituted for A _K1 and A _{K2 in} equation (4). .. The control rule for β is the same as the control rule for α shown in Table 2.

[0029]

[Table 2]

In Table 2 above, NB is negative and large (Neg
Native, NM is Negative Medium, NS is Negative Small, ZO is Zero, PB is Positive and Large, and PM is Positive. Medium
, PS represents positive small.

In the embodiment of the present invention, the control rule for α and the control rule for β are the same, but it goes without saying that different control rules may be used.

FIG. 3 is a graph showing the membership functions in the above-mentioned seven states. In this graph, the normalization is [1-1].

FIG. 4 is a schematic diagram showing a process of obtaining α. The membership function of ΔP is obtained from the value of ΔP normalized [1 −1] for the first control rule Rα ¹ for α, and Δt is calculated from the value of Δt normalized [1 −1].
The membership function of is derived, and the membership function of α is derived from these membership functions. Then, the same processing is repeated for all control rules regarding α, and α
Then, the union of the membership functions of is obtained, and α is obtained from this union using the centroid method. Similarly, β is obtained, and the output pitch P is obtained by substituting the obtained α and β into the equation (2).

As described above, since the output pitch P of the extractor is properly obtained by the present invention, this result is output from the heating and extraction computer 10 to the extractor of the rotary hearth type heating furnace 2 and the appropriate extraction is performed. The billet 1 is extracted from the rotary hearth type heating furnace 2 at a pitch.

[0035]

As described above in detail, according to the extraction control method of the rotary hearth type heating furnace according to the present invention, the optimum fuzzy theory is used when the billet is extracted from the rotary hearth type heating furnace. The extraction pitch is calculated, and the extractor of the rotary hearth heating furnace is controlled accordingly to extract the billet from the rotary hearth heating furnace.Therefore, even when the rolling line is in an unsteady state, the conventional method is used. Instead of relying on the experience and intuition of the site workers, in other words, the output value of the billet extraction pitch that has been appropriately corrected without human error is required, so it was suitable for the actual state. The billet can be extracted from the rotary hearth type heating furnace. As a result,
The method of the present invention has excellent effects such as an improvement in the quality of the steel pipe and an improvement in the yield.

[Brief description of drawings]

FIG. 1 is a schematic view showing a manufacturing process of a seamless steel pipe.

FIG. 2 is a functional block diagram of a computer used for controlling the rotary hearth type heating furnace by the extraction control method for the rotary hearth type heating furnace of the present invention.

FIG. 3 is a graph showing membership functions in seven states used in the extraction control method of the rotary hearth heating furnace of the present invention.

FIG. 4 is a coefficient α determined by applying a fuzzy control rule.
It is a schematic diagram which shows the process of calculating | requiring.

[Explanation of symbols]

 1 Billet 2 Rotary hearth type heating furnace 3, 4, 5, 6, 7 Rolling mill

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location C21D 9/08 C G05B 13/02 N 9131-3H

Claims (1)

[Claims] 1. When manufacturing a seamless steel pipe by heating a pipe material in a rotary hearth type heating furnace, extracting the heated pipe material from the rotary hearth type heating furnace and rolling it in a rolling step, The rotary hearth type heating furnace for the pipe material based on the heating temperature error which is the difference between the calculated value and the target value when the heating temperature of the pipe material is extracted from the rotary hearth type heating furnace and the rolling pitch fluctuation in the rolling process. In the extraction control method of the rotary hearth type heating furnace to control the extraction pitch from, the extraction pitch is obtained using the fuzzy theory with the heating temperature error and the rolling pitch fluctuation as the antecedent variables, and according to the obtained extraction pitch A method for controlling extraction of a rotary hearth type heating furnace, characterized in that the extraction timing of the pipe material from the rotary hearth type heating furnace is controlled.