JPS6345454B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a line speed control method for continuous annealing equipment for metal strip, particularly steel strip.
We propose an effective method that can prevent strip meandering, heat buckling, etc. that occur when continuously annealing strips of various types and sizes, and that can operate at maximum production volume (capacity).

(Conventional technology) In recent years, with the diversification of products, it has been desired to develop continuous annealing technology to produce strips of various types and sizes at low cost and with high yield. Equipment has become available that has a wide control range and can arbitrarily change operating conditions for heating, soaking, cooling, etc. according to material constraints.

However, when continuously annealing strips of various types and sizes, it is necessary to perform annealing under optimal conditions for each strip and at the maximum capacity of the equipment in terms of production cost and production yield. Therefore, judgments regarding operating conditions, constraints, etc. for a predetermined strip, calculation of line speed for maximum production volume, etc. are complicated, and there is a problem that operation is difficult with conventional control methods.

In other words, in order to continuously anneal strips of each steel type and size to the desired uniform quality, the optimum one is selected from a variety of heat patterns, the soaking temperature and cooling rate, etc. are calculated for each strip, and then these It is necessary to calculate the line speed and operate the continuous annealing equipment in order to maximize the production of strips after calculating the amount of strip.
Particularly in the case of strips, etc., which have large restrictions on materials, etc., operation cannot be performed by an operator.

Various improvement methods have already been proposed to address these problems of the prior art, including one proposed in Japanese Patent Publication No. 59-52937.

(Problems to be Solved by the Invention) However, the conventional method described above has the drawback that it does not take into consideration the meandering of the strip or heat buckles, etc., which are essential for stable operation in a continuous annealing furnace. This left a problem that needed to be resolved, namely that it was not possible to produce at the capacity line speed.

In short, the purpose of the present invention is to estimate the thermal crown amount or roll crown amount of the roll when calculating the line speed and correct the control line speed to a line speed that allows stable operation. An object of the present invention is to provide a line speed control method for continuous annealing equipment that can control the line speed to suit each optimum condition.

(Means for Solving the Problems) In order to solve the problems described above, the present invention aims to improve the heating, soaking, and cooling capacities (capacities) of the heating zone, soaking zone, and cooling zone in continuous annealing equipment. ,
The relational expressions between the annealing conditions such as furnace temperature, strip characteristics such as strip width, thickness, and temperature, and the maximum capacity line speed are determined in advance, and then calculated for each given strip from these relational expressions. Calculate the maximum capacity line speed for each of the above bands, find the minimum value of these maximum capacity line speeds, use this as the control target, and perform appropriate line speed control. Calculate the original thermal crown amount or roll crown amount of the hearth roll, compare and determine whether the calculated value is within the target thermal crown amount or roll crown amount, and determine the thermal crown amount or roll crown amount within the control range. In this case, the minimum value of the above maximum capacity line speeds shall be the set line speed, and if the thermal crown amount or roll crown amount is outside the control range, the line speed shall be within the specified range below the minimum value of the maximum capacity line speeds of each band. We propose a method in which the upper limit value of the line speed that results in the thermal crown amount or roll crown amount is determined, and the line speed is controlled using the upper limit value as a set value.

(Example) A preferred embodiment of the method of the present invention, that is, a specific method for achieving stable running (no meandering or heat buckling) will be described below with reference to the drawings.

As shown in Fig. 2, the strips 1 of various types and sizes include a heating zone 2 and a soaking zone 3 for heating and maintaining uniform heat using a radiant tube, an electric heater, etc., a cooling tube, a plenum chamber,
A primary cooling zone 4 that is kept cooled by an electric heater or the like;
Continuous annealing is performed through the secondary cooling zone 5 and the tertiary cooling zone 6 in sequence. In this continuous annealing, various heat patterns (X ₁ ,...Xi...
By selecting the optimum one for each strip from Xn), calculating the soaking temperature, cooling rate, etc., and operating according to the heat pattern, continuous annealing of various types and sizes of strips is possible.

In the present invention, a process computer automatically selects a heat pattern for each strip, calculates the soaking temperature, cooling rate, etc., and calculates the optimum line speed for effectively using the continuous annealing equipment.

First, to obtain the heat pattern Xi shown in Figure 3, various strip data (standards, steel type, chemical composition, material, plate size, coil weight, etc.) managed by the host computer are transmitted to the process computer. This calculator calculates the heat pattern based on the standard, steel type, etc. Once the heat pattern is determined, the soaking temperature Ts and cooling rate CR of the strip are calculated from the chemical composition and material.

Thus the heat pattern for a given strip
Once the annealing conditions such as Xi, soaking temperature Ts, and cooling rate CR are calculated, the maximum capacity line speed for each section of the continuous annealing equipment is determined.

The maximum capacity line speed LS _1MAX of heating zone 2 is calculated from equation (1).

LS _1MAX f ₁ (Q ₁ , W, D, T ₁ , Tz ₁ ) ...(1) Q ₁ : Heating capacity of radiant tube or electric heater, etc. W : Strip width D : Strip thickness T ₁ : Heating zone exit side Strip temperature Tz ₁ : Furnace temperature of heating zone Maximum capacity line speed LS _2MAX of heating zone 3 is as follows.
Calculated from equation (2).

LS _2MAX = f ₂ (Q ₂ , W, D, T ₁ , T ₂ , Tz ₂ ,
t) ...(2) Q ₂ : Heating, soaking capacity of radiant tube or electric heater, etc. W: Strip width D: Strip thickness T ₁ : Strip temperature on soaking zone input side T ₂ : Strip temperature on soaking zone exit side Tz ₂ : Furnace temperature in the soaking zone t : Soaking time The maximum capacity line speed LS _3MAX to LS _5MAX in each of the primary to tertiary cooling zones 4 to 6 is calculated from the following equations (3) to (5).

LS _3MAX = f ₃ (Q ₃ , W, D, T ₂ , T ₃ , Tz ₃ , CR,
t) ...(3) LS _4MAX = f ₄ (Q ₄ , W, D, T ₃ , T ₄ , Tz ₄ , CR,
t) ...(4) LS _5MAX = f ₅ (Q ₅ , W, D, T ₄ , T ₅ , Tz ₅ , CR,
t) ...(5) Q ₃ , Q ₄ , Q ₅ Cooling and heat retention capacity for cooling tubes, plenum chambers, electric heaters, etc. W: Strip width D: Strip thickness T ₂ , T ₃ , T ₄ , T ₅ : Inlet and outlet strip temperature of each cooling zone CR: Cooling rate t: Holding time Therefore, the maximum capacity line speed of each zone (section) calculated above is LS _1MAX ~ LS _5MAX and the maximum capacity of the equipment which is restricted by the mechanical and electrical system. line speed
The maximum capacity line speed LS in a specific strip can be calculated from _LSM using the following equation (6).

LS=MIN(LS _1MAX , LS _2MAX , LS _3MAX , LS _4MAX , LS _5
MAX , LS _M )...(6) In addition, (1) to calculate the maximum capacity line speed.
Equation (5) can be obtained theoretically by heat transfer calculations, empirically from experimental data, or by a combination of both.

The LS calculated by the above equation (6) becomes the capacity limit value of the annealing furnace, but in the present invention, the amount of thermal crown of the hearth roll in the furnace when calculating the LS obtained by the equation (6) is calculated by the following equation (7). It is calculated in advance from the strip temperature TS at each hearth roll position and the furnace temperature.

ΔT _Ri = f (Ls, W, D, Tsi, Tzi) ...(7) ΔT _Ri : Temperature difference between the center and edge of the i-th roll T _sq : Strip temperature at the i-th roll position ( If the temperature deviation ΔT _Ri of the hearth roll calculated by formula 7) is within the specified temperature deviation (±30℃),
Control is performed by directly using the LS obtained by equation (6) as the set value for the line speed.

On the other hand, ΔT _Ri calculated using equation (7) is within the predetermined temperature deviation ±
When it is higher than 30℃, correct LS to below the minimum value (LS = α × LS) (α < 1) and recalculate using formula (7),
LS is determined so that ΔT _Ri is within a predetermined temperature deviation, and this LS is controlled as the set value of the line speed.

The control flow during this period is shown in FIG.

In the above embodiment, the LS is determined by determining the amount of thermal crown of the roll, but the amount of roll crown may be calculated and determined based on the amount of thermal crown.

(Effects of the Invention) As explained above, according to the method of the present invention, by calculating the maximum line speed of each strip and simultaneously calculating and controlling the amount of thermal crown of each hearth roll, the meandering of the strip can be controlled. Since the line speed is controlled at a line speed that does not cause heat buckling or heat buckling, it is possible to control the operation of continuous annealing equipment of various types and sizes under optimal conditions (stable and maximum production).

[Brief explanation of drawings]

FIG. 1 is a flowchart of a line speed control method in an embodiment of the present invention, FIG. 2 is an explanatory diagram of continuous annealing equipment, and FIG. 3 is an explanatory diagram showing a heat pattern in continuous annealing equipment. 1... Strip, 2... Heating zone, 3... Soaking zone, 4-6... Primary or tertiary cooling zone.

Claims (1)

[Claims] 1. Heating and soaking of continuous annealing equipment determined in advance;
From the relational expression between the annealing conditions and strip characteristics in each cooling zone and the maximum capacity line speed, calculate the maximum capacity line speed for each of the above bands corresponding to the strip characteristics, and calculate the minimum capacity line speed among these maximum capacity line speeds. In the method of controlling the line speed based on the above control line speed, calculate the thermal crown amount or roll crown amount of the hearth roll under the above control line speed, and check whether the calculated value is within the target thermal crown amount or roll crown amount. If the thermal crown amount or roll crown amount is within the control range, set the minimum value of the maximum capacity line speeds as the set line speed,
When the thermal crown amount or roll crown amount is outside the control range, find the upper limit of the line speed that will bring the thermal crown amount or roll crown amount within a predetermined range below the minimum value of the maximum capacity line speed of each band, and calculate the upper limit. A line speed control method for continuous annealing equipment, characterized in that the line speed is controlled using a value as a set value.