JPS5826414B2 - Method for controlling heating temperature of strip in heating furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a method for controlling the heating temperature of a strip in a heating furnace used in a continuous pipe production line for forge-welded steel pipes.

Generally, the temperature of the strip applied to the heating furnace is controlled by using a thermometer such as a thermocouple or radiation thermometer as a sensor and controlling the target value of a fuel flow rate regulator using a temperature regulator. Alternatively, where speed control is performed by increasing or decreasing the transport speed of the strip, the thickness distribution curve in the longitudinal direction of the strip almost qualitatively shows a pattern as shown in FIG.

The temperature distribution in the longitudinal direction of the strip has a correlation with the thickness of the strip, so the heating temperature in the heating furnace must be controlled in accordance with the thickness distribution of the strip.

However, in a continuous pipe manufacturing line, a large number of strip coils are sequentially joined and flowed continuously, so the thickness distribution of some strips may differ depending on the condition of the reduction roll of the rolling mill, etc. Therefore, each time the strip coil changes, the thickness distribution curve changes, and the rate of temperature rise and fall must be adjusted to suit the strip.

The thermometer that measures the final temperature of the strip coil is located just outside the heating furnace, and temperature changes with short fluctuation cycles cannot be corrected by feedback from the thermometer, so temperature control that accurately corresponds to the thickness distribution curve is required. It is often difficult to do.

Particularly in the case of forge-welded pipe manufacturing lines, one strip coil is cut in the radial direction and divided into multiple strip coils, and the strips of the divided coils are successively joined to make them continuous. Currently, the company is manufacturing pipes.

Therefore, the longitudinal thickness distribution curve of the strip coil before cutting, that is, the longitudinal temperature distribution curve, has almost the same pattern in the width direction, and even if it is cut and divided into multiple pieces, the distribution curve will not be large. It doesn't change.

This invention was devised in view of the above circumstances, and when each strip of the divided strip coil is joined and heated, the temperature distribution of only the first strip is measured, and the measured value is stored in a storage device. By controlling the temperature of the other remaining strips based on the memorized pattern of measured values, it is possible to predict and control the temperature in the heating furnace in advance, improving quality and inspection yield, and saving labor. This paper proposes a temperature control method that makes it possible.

The present invention will be explained below with reference to illustrated embodiments.

Figure 1 shows an overview of a typical forge-welded pipe manufacturing line.

That is, the material strip coil 1 conveyed from IJ- is attached to the uncoiler reel 2, and the strip 1
are successively joined to the ends of the preceding and succeeding strip plates using a welding machine 3, and then passed through a heating furnace 4 to be heated, and then formed into a tubular shape of a predetermined size using a tube mill 5 and forge-welded. .

Next, the pipe is cut into a predetermined length using a rotary cutter 6, and the outer diameter is finished using a sizer roll 7 to continuously produce a forge-welded steel pipe.

In the forge-welded pipe manufacturing line described above, the strip heating temperature control device for heating the heating furnace 4 is as shown in FIG.
a speedometer 10 consisting of a thermometer 8 provided on the exit side of the heater for detecting the temperature of the heated strip, a touch roller 9 button for detecting the transport speed of the strip, and a pulse generator PG connected thereto; A storage device 11 that stores the measured value of the thermometer 8; a control device 12 that receives signals from the output button and the speedometer 10 and outputs a control signal; A gas flow rate regulator 14 that adjusts the gas supplied to a large number of gas burner groups 13 provided on the outlet side, and a speed regulator that adjusts the tube manufacturing speed of the tube mill in response to commands from the control device 12. 15.

Based on the above configuration, first, the strip coil 1 carried in from the IJ- is cut in the radial direction at predetermined intervals in the width direction into a plurality of strip coils 1a to 1d. To divide.

Here, the thickness distribution in the longitudinal direction of the strip approximately shows a curve A as shown in FIG. 3, although it varies somewhat depending on the condition of the reduction roll that is buttoned during rolling of the strip.

Therefore, when one strip coil 1 is divided into multiple parts,
The thickness distribution in the strip length direction of each strip coil 1a to 1d is the same as curve A.

Next, the strip coil 1a is attached to the uncoiler reel 2 in order, and the following strip coils lb and 1c are attached.

They are joined by a welding machine 3 in the order of 1d and heated by passing through a heating furnace 4 continuously.

At this time, the temperature distribution in the longitudinal direction of the strip plate 1a located at the beginning is measured by the thermometer 8, and the measured value is stored in the storage device 11.

Next, after the strip plate 1a has passed, the strip plate 1b passes through the furnace 4.
The temperature of the strip 1b is controlled based on the temperature distribution curve stored in the storage device 11.

Thereafter, in the same manner, the temperature of the remaining strip coils among the coils divided from one strip coil 1 is controlled based on the stored temperature distribution curve.

By the way, as mentioned before, the temperature distribution curve has a correlation with the longitudinal thickness distribution of the strip, and the temperature distribution curve B
is approximated by drawing the thickness distribution curve A and the pattern, and this is shown in FIG.

In temperature control of the strips after strip 1b, as shown in FIG. 4, temperature distribution curve B is set to mean temperature level distribution 1M,
This level B7 is divided into two elements: a temperature variation amount Bm based on the level B7.

Temperature control based on the average temperature level distribution B7 is performed by controlling the line speed of the pipe manufacturing line, that is, the conveyance speed of the strip, and temperature control based on the temperature variation Bm is performed by controlling the large number of gas burner groups 13 provided in the heating furnace 4. This is done by controlling the flow rate of the supplied gas.

That is, referring to FIG. 51 and FIG. 6, after the first strip 1a has passed, the temperature distribution curve stored from the control device 12 is simultaneously carried in as the following strips 1b and subsequent strips are carried in. B, that is, a control command signal corresponding to the average temperature level distribution BA is sent to the speed regulator 15, and a control command signal corresponding to the temperature variation Bm is sent to the gas flow regulator 14, and the strip plate 1b... The heating temperature of ... is automatically controlled.

Next, the strips 1c and 1d are controlled in the same manner.

Furthermore, the other material strip coil is divided into multiple parts, the temperature distribution of the first strip among the divided strips is memorized, and the remaining split strip coils are set in the same pattern based on the memorized temperature distribution. The temperature is controlled and the process is continued in the same manner.

The gas flow rate regulator 14 includes a thermometer 16 such as a thermocouple or radiation thermometer that detects the temperature inside the heating furnace 4, a primary regulator 17, a secondary regulator 18, and a flow rate regulator that detects fluctuations in the gas flow rate. This is a so-called cascade control system consisting of an oscillator 19 and a gas flow rate control valve 20, which improves the response speed and the influence of disturbances by %.

Further, reference numeral 21 in FIG. 6 is an air supply device, which supplies air to the gas burner group 13 in conjunction with the gas flow rate regulator 14.

That is, the secondary regulator 18 includes a gas regulator 18A, an air regulator 18B, and a ratio setter 18C, and the air supply device 21 further includes an air intake port 22, an air control valve 23, and a blower 24. It consists of a heat exchanger 25 attached to the exhaust gas outlet provided at the top of the heating furnace 4, and an air flow rate detector 26, which supplies air by following fluctuations in the gas flow rate and detects the exhaust gas. The heat retained in the fuel is used to raise the supply air, improving the combustion efficiency of the combustion gas.

By the way, the method of determining the strip passing through the heating furnace 4 is based on a preset method in which the welding points of the preceding strip and the following strip by the welding machine 3 are used as tracking points, and a stored temperature distribution curve is used. We are trying to match B with the strip that actually flows.

That is, the heating furnace 4 is provided with a brisset calantara, the expected calculated length of the material strip coil 1 is converted into a pulse and set on this preset counter, and the button is pressed to flow the strip 1 into the pipe manufacturing line. Subtract the feed rate of strip 1 from the preset counter value - When the counter value becomes zero, continuous strips are joined in sequence, such as strips 1a and 1b or 1b and 10, in the heating furnace. It is determined that the welding point exists or has entered the heating furnace 4, and the output is output at that time.

First, input that output into a subtracter.

The subtracter subtracts the number of divisions M of the material strip coil 1 and the number N of zero outputs of the preset counter value, that is, (M-N
), and when it becomes M-N-o, a reset signal is output to erase the stored information in the storage device 11.

In this state, the expected length of the next material coil is set in the preset counter, and on the other hand, the temperature distribution of the leading strip of the strip divided from that material coil is stored in the storage device, and the remaining divided strip is The temperature of the board is controlled based on stored information.

Thereafter, the temperature of the divided strips 1a to 1d is controlled in the same way, and the stored information is replaced by tracking control of the strips 1a to 1d.

However, the preset counter is installed in the computer by software or hardware.

Previously, the applicant had applied for a tracking method that uses welding points as tracking points (Japanese Patent Application No. 51-093799 Welding Point Detection Method). In addition, a preset counter is installed in each zone, and the expected length determined from the weight of the material before welding is set in the preset counter, and continuous long materials that are sequentially joined by welding are flowed onto the line and the speed is adjusted accordingly. Subtract each preset counter value corresponding to the actual feed rate of the long material, press the button at the position where the counter value becomes zero to determine that a welding point exists, and place a welding point detector at a predetermined position on the line. and the preset counter value is corrected based on the welding point detection signal detected by the detector, and the welding point detector measures the thickness of the long material and applies the thickness signal to detect an abnormal position as a welding point. This is an X-ray thickness gauge designed to detect welding points, and the tracking of the present invention can be easily performed by applying the above-mentioned tracking method, making it easy to identify the strip passing through the heating furnace 4. You can go to

As described above, according to the present invention, it is possible to perform temperature control corresponding to the thickness distribution of the strip, and furthermore, the temperature distribution of any one of the plurality of strips divided from one strip coil can be controlled. is stored and the temperature of the remaining strips is controlled based on the stored information, which is extremely rational and saves labor in temperature control.

In addition, the control output can be used as a timing control output for adjusting the speed of the pipe-making line or adjusting the reduction amount of the pipe-making line, and centrally controlling the pipe-making line is also possible.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the pipe manufacturing line, Figure 2 is a perspective view showing how the material strip coil is divided, Figure 3 is a schematic diagram showing the longitudinal thickness distribution curve button and temperature distribution curve of the strip. Figure 4 is a partially enlarged schematic diagram showing details of the temperature distribution curve, Figures 5 and 6.
The figure is a schematic diagram showing the configuration of the temperature control device. 1... Material strip coil, 1a to 1d... Curved strip plate, 2... Uncoiler reel, 3...
Welding machine, 4...Heating furnace, 5...Pipe mill, 6...Rotary cutter, 7...
...Sizer roll, 8...Thermometer, 9...
...Touch roller, 10...Speedometer, 11.
... Storage device, 12 ... Control device, 13
...Gas burner group, 14...Gas flow rate regulator, 15...Speed regulator, 16...
・Thermometer, 17...Primary regulator, 18...
...Secondary regulator, 19...Flow rate oscillator, 20.
... Gas flow control valve, 21 ... Air supply device, 22 ... Air intake port, 23 ... Air control valve, 24 ... Blower, 25...
Heat exchanger.

Claims (1)

[Claims] 1. A strip coil is cut in the radial direction, divided into a plurality of strip coils, the divided strip coils are stretched, the strips are sequentially joined, and the strips are poured into a heating furnace, and the first strip coil is separated into a plurality of strip coils. Measuring the temperature distribution in the longitudinal direction of the plate, storing the measured value in a storage device, and controlling the heating temperature of other strips other than the first measured strip based on the stored temperature distribution pattern. A method for controlling the heating temperature of a strip that is buttoned in a heating furnace, characterized by: 2. The heating temperature control method for a strip plate to be buttoned in a heating furnace according to claim 1, wherein the strip plate is heated by combustion gas. 3. The heating temperature of the strip in the heating furnace according to claim 1, wherein the temperature of the strip is controlled by adjusting the conveyance speed of the strip passing through the heating furnace. Control method. 4. The method of controlling the heating temperature of a strip in a heating furnace according to claim 2, wherein the temperature of the strip is controlled by adjusting the flow rate of combustion gas. 5. The heating furnace according to claim 2, wherein the temperature of the strip is controlled by using a button for adjusting the conveyance speed of the strip passing through the heating furnace and a flow rate adjustment of the combustion gas. −
Method for controlling heating temperature of strips. 6. The longitudinal temperature distribution of the strip is measured by dividing it into two temperature patterns: an average temperature level distribution and a temperature minute fluctuation distribution based on this distribution. A method of controlling the heating temperature of a strip that is heated in a heating furnace. 7. The heating furnace according to claim 6, wherein the heating temperature of the strip is controlled by adjusting the conveying speed of the strip passing through the heating furnace based on the average temperature level distribution pattern. A heating temperature control method for heating strips. 8. A heating temperature control method for a strip to be buttoned in a heating furnace according to claim 6, wherein the heating temperature of the strip is controlled by adjusting the flow rate of combustion gas based on the distribution of small temperature fluctuations. . 9. Claims 1 and 2, characterized in that the strips of the plurality of divided strip coils are joined by welding.
A method for controlling the heating temperature of a strip in a heating furnace according to item 1, 3, 4, 5, 6, 7 or 8.