JPH02225626A - Method for controlling transfer speed of continuous annealing furnace - Google Patents

Abstract

PURPOSE:To improve the annealing of a succeeding material by controlling an in-furnace transfer speed in such a manner that the temp. of the succeeding material in the outlet of a heating furnace attains the target temp. in a target response time at the time of welding the preceding material and succeeding material of steel strips of different sizes, materials, annealing temp., etc., and subjecting the materials to continuous annealing in the same heating furnace. CONSTITUTION:The conditions, such as thicknesses, materials and annealing temp., of the preceding material and the succeeding material vary and, therefore, the in-furnace transfer speed is previously so controlled that the temp. in the outlet of the heating furnace attains the target temp. at the time of welding the rear end of the preceding steel strip and the front end of the succeeding steel strip and subjecting the steel strips to the continuous annealing in the same heating furnace. The preceding material is once controlled to a high speed and is thereafter controlled to the target transfer speed if the transfer speed of the succeeding material is higher than the transfer speed of the preceding material in this case. The succeeding material is once set at a low speed and is thereafter controlled to the target transfer speed if the transfer speed of the succeeding material is lower than the transfer speed of the preceding material. The generation amt. of the defective material parts failing to be subjected to the annealing by the target temp. near the weld zones is thereby decreased and the annealing efficiency of the succeeding material is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling the transport speed of a strip material for controlling the temperature of the strip material in a continuous annealing furnace.

[Prior art and problems to be solved by the invention] In a continuous annealing furnace for steel plates, a continuous heating furnace is used as the heating zone, and a specific heat cycle determined from the mechanical properties of the steel plate is ensured. We are currently heat treating steel plates. In such a continuous annealing furnace, in order to heat-treat the steel plate continuously, the rear end of the steel plate being threaded is joined by welding to the tip of the steel plate being threaded next on the entrance side of the furnace. . When steel plates are joined in this way, if the size target plate temperature and material of each steel plate are different before and after the joint, the transfer speed, which is a manipulated variable, should be adjusted so that the outlet plate temperature of the heating furnace becomes the target plate temperature. Heat treatment is performed by changing the furnace temperature.

A method of controlling the outlet plate temperature using the transfer speed as a manipulated variable will be explained.

FIG. 5 is a time chart showing a conventional line speed control method for a continuous annealing furnace. This is because, as shown in (a), the thickness H1 of the preceding material is smaller than the thickness 11□ of the succeeding material (II
I<I+□), as shown in (b), the target plate temperature T1 of the preceding material is smaller than the target plate temperature T of the subsequent material (Ti<Tz
), in order to achieve the target plate temperature T, with a constant furnace temperature as shown in (d), the transfer speed shown in (C) is set from V to v.
This shows an example of reducing the number to 2.

In this case, due to the reduction in the transfer speed, the internal firing time of the steel material becomes longer, and the plate temperature at the exit of the heating furnace shown in (e) increases. However, a certain amount of time is required until the plate temperature at the exit of the heating furnace stabilizes at the target plate temperature T2 (as shown in the plate temperature deviation part e).

Since the steel material heated during this period of time does not satisfy the predetermined heat treatment conditions, there is a problem in that the steel material cannot obtain predetermined mechanical properties.

The present invention has been made in view of the above circumstances, and provides a transfer speed control for a continuous annealing furnace in which the transfer speed is changed so that the plate temperature at the exit of the heating furnace is stabilized at the target plate temperature within a predetermined target response time. The purpose is to provide a method.

[Means for Solving the Problems] The method for controlling the transfer speed of a continuous annealing furnace according to the present invention has the following advantages:
In order to control the temperature of the strip material made by joining the preceding material and the succeeding material, which differ in at least one of the target temperature and material, the dimensions,
In a method for controlling the transfer speed of a continuous annealing furnace, in which the transfer speed of the next material is determined in advance based on the target temperature and material, and the transfer speed of the next material is controlled to reach the set transfer speed, the transfer speed of the next material is set to be the same as that of the preceding material. If the transfer speed is faster than the transfer speed, the next material is temporarily held at a speed higher than the transfer speed, and then controlled to reach the transfer speed.On the other hand, if the transfer speed of the next material is slower than the transfer speed of the preceding material , the next row material is once held at a speed lower than the transport speed, and then the next row material is controlled to be at the transport speed of the next row material.

[Effect]

If the predetermined transfer speed of the next material is faster than the transfer speed of the preceding material, once the next material is held at a faster speed than the predetermined transfer speed before controlling the next material to the predetermined transfer speed, the strip material Since the rate of change of temperature increases, the temperature reaches its target value in a short time. Similarly, if the predetermined transfer speed of the next material is slower than the transfer speed of the preceding material, once the next material is held at a slower speed than the predetermined transfer speed before controlling the next material to the predetermined transfer speed. , since the rate of change in temperature of the strip increases, the temperature reaches the target value in a short time.

[Example] Hereinafter, a method for controlling the transfer speed of a continuous annealing furnace according to the present invention will be described based on drawings showing examples thereof.

FIG. 1 is a schematic diagram showing the heating position and transfer speed control system of a continuous annealing furnace used when carrying out the method of the present invention.

In the figure, l denotes a heating furnace which is a continuous annealing furnace heating zone equipped with a plurality of hearth rolls 2.2 for transferring the strip-shaped steel plate H, and is a heating furnace in the transfer line of the steel plate H. A pair of upper and lower priddle rolls 3 driven by a drive motor M are disposed on the output side of the roller 1, and the speed of the drive motor M is controlled by a motor speed control device 4.

Reference numeral 6 is a transfer speed setting device that sets the transfer speed of the transfer line according to the dimensions, target plate temperature, and material of the steel plate H, and 7 is a transfer speed setting device that sets the plate temperature at the outlet of the heating furnace to the target plate temperature when changing the plate temperature. A target response time setting device 8 sets a target response time 1p until the heating zone temperature reaches 1, and a time constant setting device 8 sets a time constant T of the response of the plate temperature at the outlet of the heating belt.

Said transfer speed setting device6. The output signals of the target response time setter 7 and the time constant setter 8 are input to the transfer speed controller 5, respectively. In the transfer speed controller 5, the preceding material transfer speed setting value Vl is inputted from the transfer speed setting device 6.

Next material transfer speed setting value v! , the target response time Lp2 input from the target response time setter 7, the time constant T inputted from the time constant setter 8, determines a transfer speed control pattern to be described later, and in order to realize this, the motor speed control device 4
A transfer speed control signal is input to. The motor speed control device 4 controls the drive motor M based on the transfer speed control signal to control the transfer speed of the steel plate H on the transfer line.

Next, the principle of the transfer speed control method of the present invention will be explained.

FIG. 2 is a time chart showing the response of the plate temperature at the outlet of the heating furnace to changes in the transfer speed, and FIG. 3 is a time chart of the transfer speed control used in the method of the present invention.

For example, as shown in FIG. 2, when changing the transfer speed from the preceding material transfer speed set value v1 to the next material transfer speed set value ν in order to lower the plate temperature at the heating furnace outlet (vl<ν,), the heating furnace In order to stabilize the outlet temperature at the target response time 1p, as shown in FIG. 0
At , the transfer speed is increased stepwise from the preceding material transfer speed setting value V to the plate speed setting value V, which will be described later, and this is timed.

After holding it up to the next material transfer speed setting value v2, it is sufficient to decrease it in a stepwise manner.

Before carrying out such control, first, the response waveform at the heating furnace outlet plate point when the transfer speed 2 is changed stepwise from vl to 'Jt as shown in Fig. 2, under the condition of a constant furnace temperature. The response waveforms obtained by collecting a large number of steel plates of the same size and the same material and taking the average of these are used as the change in plate temperature ΔT3 from the initial value of the plate temperature at the outlet of the heating furnace, and the first-order lag system as shown in equation (1) below is used. Approximate by

However, θT, /θV: Influence coefficient of transfer speed change on heating furnace exit plate temperature change ('C/mp stiffness) T: Time constant of response of heating furnace outlet plate temperature S Nira plus operator Reverse the above equation (1) By Laplace transform, the following (2
), the plate temperature change ΔT is converted into a time function (t≧0
)...(2) However, L: A method for determining the plate speed set value V based on the time when the transfer speed is changed will be explained.

The amount of change ΔT in the heating furnace outlet plate temperature from time O to target response time 1p in FIG. 3 is the same as the equation (2) above... (3
) In order to settle the heating furnace outlet plate temperature to the target value at the target response time Ll, the target response time LP is obtained when the transfer speed is changed from the preceding material transfer speed setting value V to the plate speed setting value V. The amount of change in plate temperature at the heating furnace outlet and the transfer speed are determined by the preceding material transfer speed setting value V and the next material transfer speed setting value V.
Steady value θ of the amount of change in heating furnace outlet plate temperature when changing to 2
It is sufficient to match T, /θ■·(ν2−ν,).

That is, it is sufficient if the following formula (4) holds true.

From the above equation (4), at time 0, the transfer speed change amount V,
-V, if the transfer speed is changed three times and this is maintained until the target response time jp, the furnace outlet plate temperature will reach the target value at the target response time L2. Then, if the transfer speed is changed stepwise to the next material transfer speed setting value v2 during the target response time, the heating furnace outlet plate temperature is stably controlled to the target value.

Furthermore, the above-mentioned control is applied similarly when changing the transfer speed from the preceding material transfer speed setting value V, to the next material transfer speed setting value V, (V, > ν2) in order to increase the plate temperature at the outlet of the heating furnace. Applicable.

A method of controlling the transfer speed using the transfer speed control system based on the principle as described above will be explained.

When heat-treating a steel plate H obtained by welding a preceding material and a subsequent material having different conditions such as dimensions, target plate temperature, material quality, etc. at a constant furnace temperature, the transfer speed setting device 6. The respective set values are manually entered into the target response time setter 71 and the time constant setter 8 in advance. In the transfer speed controller 5 into which information on these setting values is input,
Based on these set values, the plate speed setting value V is calculated using the formula (4) above, and when changing the transfer speed from the preceding material to the next material, the transfer speed is changed in steps from the preceding material transfer speed setting value v1 to the plate speed. The motor speed control device controls the transfer speed to be changed to the set value V, hold the transfer speed until the target response time 1p, and change the transfer speed stepwise to the next transfer speed set value ν2 at the target response time t. A transfer speed control signal is output to 4. The motor speed control door device 4 controls the drive motor M based on the transfer speed control signal to control the transfer speed of the steel plate 11.

Using the method of controlling the transfer rate of a continuous annealing furnace according to the present invention and the conventional control method, the transfer rate was actually controlled under the conditions shown in Table 1 below. The results are shown in the time chart of FIG.

Table 1 and FIG. 4 are time charts showing the results of the transfer speed control. In each of the signals shown in (a) to (e), the solid line indicates the method of the present invention, and the dashed line indicates the conventional method. As is clear from this figure, according to the method of the present invention, the plate temperature at the exit of the heating belt is shorter than that of the conventional method, and the settling time, which was required for the conventional method from 6 minutes, was shortened to 2 minutes.

(Effects of the Invention) As detailed above, in the method for controlling the transfer speed of a continuous annealing furnace according to the present invention, when changing the transfer speed in order to control the plate temperature at the outlet of the heating furnace, the predetermined target response time is The present invention has excellent effects such as controlling the transfer speed so that the plate temperature at the outlet of the heating furnace is stabilized at the target plate temperature, so that the plate temperature at the outlet of the heating furnace can follow the target value in a short time. play.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the heating device and transfer rate control system of a continuous annealing furnace used when carrying out the method of the present invention, and Figure 2 is a time diagram showing the response of the plate temperature at the outlet of the heating furnace to changes in the transfer rate. 3 is a time chart of transfer speed control used in the present invention, FIG. 4 is a time chart showing the method of the present invention, and FIG. 5 is a time chart of conventional transfer speed control. 5... Transfer speed controller 7... Target response time setting device 6... Transfer speed setting device 8... Time constant setting device patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono Funeral map Funeral map Funeral map Funeral map

Claims (1)

[Scope of Claims] 1. In order to control the temperature of a strip material made by joining a preceding material and a succeeding material that differ in at least one of dimensions, target temperature, and material, the next material is determined in advance according to the dimensions, target temperature, and material. In a continuous annealing furnace transfer speed control method that determines the transfer speed of a material and controls the transfer speed of the next material to achieve this transfer speed, when the transfer speed of the next material is faster than the transfer speed of the preceding material, Once the next material is held at a speed higher than the transfer speed, it is controlled to reach the transfer speed; on the other hand, if the transfer speed of the next material is slower than the transfer speed of the preceding material,
After once holding the next material at a speed lower than the transfer speed,
A method for controlling the transfer speed of a continuous annealing furnace, characterized by controlling the transfer speed of the next material.