JPS602634A - Continuous heating method of steel strip - Google Patents

Abstract

PURPOSE:To shorten the soaking zone of a continuous heat treating installation for a steel strip and to reduce energy consumption by combining an induction heating furnace having a small time constant with said installation. CONSTITUTION:An induction heating furnace 2 is provided on the inlet side of the heating zone 11 of a heat treating installation 1 in which the heating zone 11, soaking zone 12 and cooling zone 13 are successively arranged. A thickness gauge 3 and a speedometer 4 are provided on the inlet side of the furnace 2 and the thickness detection signal and actually measured speed value of the steel strip therefrom and further the temp. detection signals from thermometers (a), (b) at the intermediate point and outlet side of the zone 11 are inputted to a calculator 5. The calculator 5 takes these detection signals and set values (e.g., the ordered thickness of the steel strip, the ultimate temp. of heating, etc.) therein and outputs a control signal for the supply of electric power to a switching circuit 6. The circuit 6 controls the supply of the electric power according to said signal and supplies the electric power from a power source circuit 7 to the furnace 2. The purpose of measuring the thickness distribution of the steel strip lies in quick control of the electric energy to be supplied to the furnace 2 in response with the deviation in said thickness and the purpose of detecting the steel strip speed lies in control of the timing to supply the electric power in response with the change in said speed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuously heating a copper strip. Continuous heat treatment equipment for copper strips is generally a heating zone.

It consists of a soaking zone and a cooling zone, and the fuel for the heating zone and soaking zone is inexpensive C gas.

Natural gas and light/heavy oil are generally used. However, when these combustible fuels are used in continuous heat treatment equipment, the time constant (the time it takes for the temperature to change from one temperature to the next) Because of the large diameter, it was impossible to control the furnace temperature in seconds.

Generally, the thickness of the copper strip passed through continuous heat treatment equipment is
There are large fluctuations around 100 m at the leading and trailing ends of the copper strip, and as a result, the thickness deviation of the copper strip appears as a temperature deviation of the steel strip in the heating zone, and as a result, the material properties (
Variations occur in yield point strength, tensile strength, etc.).

Figure 1 shows the relationship between the heating temperature of the copper strip and its tensile strength. In FIG. 1, the horizontal axis (x) represents the material temperature at the exit side of the heating zone, and the linear axis (y) represents the tensile strength.

These correlations are expressed by the empirical formula y=94.0-0.077
I get hit by an X.

From the above general formula, it can be seen that by keeping the heating temperature of the copper strip constant, it is possible to suppress variations in characteristics.

Therefore, generally, a soaking zone is provided for a sufficiently long time after the heating zone, and the unsteady portion of the copper strip is heated until the heating temperature reaches a predetermined temperature, thereby absorbing temperature variations and making the characteristics uniform.

However, in the conventional method of absorbing temperature variations in a soaking zone, the amount of heat transferred in the soaking zone is small, so the length of the furnace must be sufficiently long, which has the disadvantage of increasing equipment costs and equipment space.

On the other hand, induction heating furnaces have a small time constant, but in terms of energy cost, they are about three times more expensive than the above-mentioned combustion heating equipment, and when heating steel strips from room temperature to high temperatures of 800°C, it is difficult to use a single unit. It has drawbacks that make it difficult to use as a furnace.

The present invention has been made by focusing on the relationship between the heating temperature of copper strip and tensile strength, and the relationship between time constant and energy cost. By combining an induction heating furnace with a small time constant, it is possible to absorb temperature variations in the copper strip, shorten the soaking zone, and reduce installation space, equipment costs, and energy.

That is, the continuous heating method for copper strips of the present invention is a continuous heat treatment equipment for copper strips in which a heating zone, a soaking zone, and a cooling zone are sequentially arranged. arranging at least one induction heating furnace; measuring the thickness distribution of the steel strip at the entrance side of the induction heating furnace;
controlling the heating temperature of the induction heating furnace based on the measured thickness distribution of the copper strip; measuring the line speed of the steel strip at the entry side of the induction heating furnace; the line speed of the copper strip; The invention is characterized in that the timing of power supply to the induction heating furnace is adjusted based on the timing.

Next, an embodiment of the present invention will be described with reference to FIG. In this embodiment, the heating zone is 11 degrees, the soaking zone is 12 degrees. First heating zone 110 of heat treatment equipment arranged in sequence with cooling zone 13
An induction heating furnace 2 is provided on the entry side, and a thickness gauge 3 and a speed meter 4 are provided on the entry side of the induction heating furnace 20. The thickness detection signal from the thickness gauge and the actual steel strip speed value from the speedometer are input into the computer 5.

Furthermore, a thermometer 4 provided at the midpoint and outlet side of the heating zone 11
The temperature is detected from the nine ports, and the temperature detection signal is also input to the computer 5.

The calculator 5 incorporates these detection signals and set values (for example, the ordered thickness of the copper strip, the heating temperature reached, the required tensile strength, etc.) and outputs a power supply control signal to the switching circuit 6. The control method in this case may be any control method such as on-off control or proportional control as long as it meets the purpose. The switching circuit 6 performs power supply control based on the control signal, and supplies power from the power supply circuit 7 to the induction heating furnace 2.
The thickness of the copper strip is approximately 0.5 mm, and the temperature difference is approximately 100 mm.
℃, and the overall efficiency is approximately 80 cm, approximately 3001 cv
becomes. Here, as the speedometer 4, a commonly used rotating roll speedometer can be used.

Further, as the continuous thickness gauge 3, a conventional X-ray, β-ray, or γ-ray thickness gauge, a flying micrometer, or the like can be used.

As the switching circuit 6, a conventional thyristor impark can be used.

As the thermometers 11 , 12 , 41 , conventional thermocouple thermometers, radiation thermometers, etc. can be used.

In the present invention, the thickness distribution of the copper strip is measured by:
This is to quickly control the amount of power supplied to the induction heating furnace 2 in response to the thickness deviation of the copper strip.
The purpose of detecting the speed change is to control the power supply timing in response to changes in the line speed of the copper strip.

In addition, the material temperature inside the furnace is detected and used as a foot check signal in order to detect various fluctuation factors in real time and quickly control the power supply to the induction heating furnace.

Next, the results of implementing the method of the present invention will be explained. FIG. 3 shows the results of implementing the present invention on a copper strip having a thickness of 0.48.0.50.0.5'2+11111. FIG. 4 shows a comparative example using the conventional method. In each figure, the heating results for copper strip thicknesses of 0.48, 0.50, and 0.52 are expressed in ASBSC.

As can be seen from these results, in the conventional method, a temperature difference occurs as the heating progresses due to the difference in the thickness of the copper strip, but in the method of the present invention, the temperature is controlled at the initial stage of heating.
As heating progresses, the temperature difference gradually decreases, and by the end of heating, the temperatures are almost the same. In the method of the present invention, the heating zone (11
) or temperature control in the soaking zone (12) 0

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the heating temperature reached and the tensile strength. FIG. 2 is a schematic explanatory diagram showing the method of the present invention. FIG. 3 is a graph showing the temperature change of the material heated by the heating method of the present invention. FIG. 4 is a graph showing the temperature change of a material heated by a conventional heating method. ■...Heat treatment equipment 2...Induction heating furnace 3...Continuous thickness gauge 4...Speed meter 11...Heating zone 12...Soaking zone 13...Cooling zone 49 ports...Temperature Total (β)〃1 item

Claims (1)

[Claims] In a continuous heat treatment facility for steel strips in which a heating zone, a soaking zone, and a cooling zone are sequentially arranged, a small number of (all one) induction heating furnaces may be arranged between the input side of the heating zone and the exit side of the soaking zone. , measuring the thickness distribution of the steel strip at the entrance side of the induction heating furnace; controlling the heating temperature of the induction heating furnace based on the measured value of the thickness distribution of the copper strip; at the entrance side of the induction heating furnace. Measuring the line speed of the steel strip;
A continuous heating method for a copper strip, characterized in that the timing of power supply to the induction heating furnace is adjusted based on the line speed of the steel strip.