JPH03193824A - Method for executing continuous annealing and descaling - Google Patents

Abstract

PURPOSE:To prevent the development of slack and meandering of a strip in a furnace by controlling velocity of bridle rolls arranged at inlet side and outlet side of the annealing furnace and maintaining a specific extension ratio of the strip in the furnace. CONSTITUTION:After cooling the strip 10 annealed in the annealing furnace 1 with cooling devices 2, 2', this is passed through an electrolyte descaling device 6 providing a neutral salt bath vessel 7 and acidic liquid bath vessel 7' to remove scale on the surface layer generated in the annealing. In the above continuous annealing and descaling devices, the bridle rolls 3, 4 are set at the inlet side and the outlet side of annealing furnace 1. At the time of passing the strip 10, the velocity of the above bridle rolls 3, 4 is controlled so that a specific extension ratio of strip 10 in the annealing furnace 1 is kept. By this method, extension rate in the longitudinal direction and shrinkage rate in the width direction of strip 10 are fixed and the slack and meandering of strip 10 in the furnace is not developed. Further, the strip having high degree of flatness is obtd. and by narrowing interval of the electrodes 8, 8' in the bath vessels 7, 7' the electrolytic power can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a continuous annealing and descaling method for strips of iron, stainless steel, etc.

[Prior Art] Conventionally, after annealing a strip of iron, stainless steel, stainless steel, etc. in an annealing furnace, the scale (oxide film) formed on the surface of the strip during annealing is electrolyzed in an acid or neutral salt bath. In so-called continuous annealing/descaling equipment, which descales by a method, the strip is usually heated at 800°C to 800°C in an annealing furnace.
Because the strip stretches and meanderes when heated to about 1150°C, bridle rolls are installed on the entrance and exit sides of the annealing furnace to keep the catenary (sagging) of the strip constant in the annealing furnace. The tension of the bridle rolls is controlled so that a constant tension is always applied to the strip between the rolls.

[Problems to be Solved by the Invention] Conventionally, the tension of the strip in an annealing furnace is controlled by bridle rolls provided at the entrance and exit sides of the furnace so that the tension is constant, but if the set tension is small, The elongation caused by heating cannot be completely absorbed, causing the strip to sag or meander in the furnace, which may impede the annealing process.In addition, the shape of the strip after annealing may be poor and the spacing between the electrodes of the subsequent electrolytic descaling device may be affected. If the strip is not wide enough, the strip cannot pass through the descaling device smoothly, so the capacity of the power supply device must be increased, and there are problems such as increased power consumption.

On the other hand, if the set tension is increased to solve the above problem, the plastic elongation due to the creep phenomenon that occurs in the annealing furnace will cause the strip to shrink in the width direction, making the strip width uneven, so that it is difficult to obtain the desired strip width. In order to achieve this, it is necessary to feed a strip with a considerable width margin to the annealing furnace, resulting in a lot of wasted material and poor product yield, so that in any case, fully satisfactory results have not been obtained.

[Means for Solving the Problems] According to the present invention, in a continuous annealing/descaling apparatus having an annealing furnace and an electrolytic descaling device provided at the rear stage of the annealing furnace, By providing a bridle roll for each and controlling the speed of the inlet bridle roll and the outlet bridle roll so that the elongation rate of the strip in the annealing furnace is constant, the elongation rate in the longitudinal direction and the amount of shrinkage in the width direction of the strip can be controlled. Continuous annealing with a constant temperature and no sagging or meandering of the strip in the annealing furnace.
A descaling method is obtained.

[Example] An embodiment of the present invention will be described below.

The figure schematically shows a continuous annealing/descaling apparatus in which the present invention is implemented.

In the figure, 1 is an annealing furnace, 2 and 2' are cooling devices, 3 is an entry bridle roll provided on the entry side of the annealing furnace 1, and 4 is an exit bridle provided on the exit side of the annealing furnace (cooling device) 1. It's a roll.

Reference numeral 6.6' denotes a descaling device, and in this embodiment, two sets of a neutral salt electrolyzer 6 and an acidic liquid electrolyzer 6' are provided in series downstream of the annealing furnace 1.

These descaling devices 6, 6' are constructed by filling a bath 7, 7' with an electrolytic solution such as a neutral salt or acid solution, and installing electrodes 8, 8' facing each other so as to be immersed in the electrolytic solution. During the annealing, a strip 10 of iron or stainless steel annealed in the annealing furnace 1 is continuously inserted.
The scale (oxide film) formed on the surface is separated by electrolysis.

11.11', 12.12' are entrance guide rolls, 13
．． 13' 14. 14' is an exit guide roll.

Reference numerals 15 and 15' denote brush roll units installed on the outlet side of the descaling devices 6 and 6', respectively.
This is to remove scale on the surface of the strip 10 treated in step 6'.

Note that the descaling device 6.6' is the same as the 2 shown in the embodiment.
It goes without saying that the number of sets is not limited, and one composition may be provided with three or more sets as necessary.

Reference numeral 16 denotes a pickling device for chemically finishing the surface of the strip 10 treated by the descaling device 6.6' using a nitric-hydrofluoric acid solution or the like.

It goes without saying that this pickling device 16 does not necessarily need to be provided if treatment by a descaling device is sufficient.

The present invention provides bridle rolls 3 provided at the entrance and exit sides of the annealing furnace 1 of the continuous annealing/descaling apparatus configured as described above.
．． By controlling the relative speed of the bridle rolls 3 and 4, a preset constant elongation rate is imparted to the strip 10 between the bridle rolls 3 and 4, that is, in the annealing furnace 1.

That is, the number of rotations (peripheral speed) of the entry side bridle roll 3 is nl
, when the rotational speed (peripheral speed) of the exit bridle roll 4 is na, the elongation rate ε is controlled to be the optimum elongation rate according to the material of the strip 10 derived from the following equation.

This elongation rate is a value (
0.2 to 1.0%).

In addition, when controlling the speed of the bridle roll, either one of the entry side bridle roll 3 or the exit side bridle roll 4 is adjusted to a speed standard of the annealing furnace 1 and the descaling device 6, 6', and the other is set faster than that. control to speed up or slow down.

In this way, by controlling the elongation rate (longitudinal direction) of the strip 10 to be constant, the shrinkage amount εC of the strip in the width direction is calculated as follows: where the input side width is bo + the output side width is bl. 1-()r+1 1-ε.

(However, r = Lankford value) It is derived by the formula.

Therefore, if the elongation rate of the strip 10 in the longitudinal direction is determined in advance, the corresponding amount of shrinkage in the width direction can also be determined. There will be no waste.

Further, the annealed strip 10 is given plastic elongation and high flatness is obtained by so-called tensile straightening.
Even if the electrode spacing of the electrolytic descaling device 6°6' is narrowed, the strip 10 can be inserted smoothly.

Therefore, the electrode spacing and the resistance voltage EC when energized are proportional as shown by the following equation.

Therefore, by narrowing the distance between the electrodes, the electrolytic voltage is reduced, and when the current necessary for descaling is passed, power consumption can also be reduced.

[Effects of the Invention] According to the present invention, by controlling the elongation rate in the longitudinal direction of the strip to be constant when annealing the strip, it is possible to keep the amount of shrinkage of the strip constant in the width direction. Therefore, by selecting the material strip width in advance by anticipating the amount of shrinkage in the width direction of the strip, the yield of the product can be improved, and the optimum elongation rate can be arbitrarily given to the material. Since high flatness can be obtained by applying sufficient plastic elongation and tensile straightening, it becomes possible to narrow the distance between the electrodes of the electrolytic descaling device, and it has effects such as saving energy in electrolytic power.

[Brief explanation of drawings]

The figure is a schematic diagram of a continuous annealing/descaling apparatus in which the present invention is implemented. 1... Annealing furnace 3... Entry side bridle roll 4
...Output bridle roll 6.6'...Electrolytic descaling device

Claims (1)

[Claims] 1) In a continuous annealing/descaling device that has an annealing furnace and an electrolytic descaling device installed at the rear stage of the furnace, bridle rolls are provided on the entrance and exit sides of the annealing furnace, and the entrance bridle roll and the exit side A continuous annealing/descaling method characterized by controlling the speed of a bridle roll in an annealing furnace so that the elongation rate of the strip is constant.