JPH01255628A - Continuous bright annealing method for wide thin band steel and wide band foil and horizontal continuous bright annealing furnace - Google Patents

Abstract

PURPOSE:To bright-anneal a band steel wider and thinner than before with excellent flatness by holding a wide thin band steel in a first annealing zone at a specified temp. at the of brightannealing the steel band, etc., in a horizontal continuous annealing furnace having the heating zone, first annealing zone and a second annealing zone. CONSTITUTION:The horizontal continuous annealing furnace consisting of a heating zone 2 having a heater 7, the first annealing zone 3, a connection zone 4, and the second annealing zone 5 is used, when a wide thin band steel or a wide band foil 1 is bright-annealed. A support roll 10 having 200-600mm outer diameter identical to the outer diameter of a hearth roll 12 in the second annealing zone 5 is arranged at the outlet from the heating zone 2 and at the inlet to the first annealing zone 3, the first annealing zone 3 has the same structure as that of the heating zone 2, a furnace temp. controller 6 is provided in both zones 2 and 3 to prevent the supercooling of the band steel 1 leaving the heating zone 2 in the first annealing zone 3, and the thermal compressive stress exerted on the band steel 1 is controlled. The band steel 1 is then annealed with an atmospheric gas in the second annealing zone 5, and the deformation of the band steel in the cooling process is prevented.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention provides a method for producing a bright annealed material with good shapes of a wide m steel strip and a wide foil strip in a horizontal continuous bright annealing facility, and a horizontal continuous bright annealing equipment. Regarding an annealing furnace.

<Prior art> As shown in FIG. 2, a typical horizontal continuous bright annealing equipment for steel strips has a bright annealing furnace 13 for the steel strip l in the center, and a priddle roll 14 and a steel strip installed in front of the bright annealing furnace 13. It consists of a tension roll 15 for applying tension in the furnace to the furnace 1, and a prydle roll 16 installed at the rear.

As shown in FIG. 3, the -1'G bright annealing furnace 13 includes a heating zone 6, a joint zone 17, a cooling tube type first lehr 18, and a convection type second lehr 5 using atmospheric gas. Reference numeral 19 in Fig. 0 is a cooling tube disposed in the first slow cooling zone. Also, a hearth roll 11 of a heating zone 2 that supports and conveys the steel strip 1 and a convection type second slow cooling zone 1 are provided.
The minimum number of hearth rolls 12 of No. 8 are arranged at a constant pitch so that the catenary depth of the steel strip l does not become large, and these rolls have an outer diameter of about 150 mm. 7 is a heater for heating.

<Problems to be Solved by the Invention> However, the copper strip processed in such a horizontal continuous bright annealing furnace is limited to a width of less than 700 mm, a thickness of 0.1 mm or more, and a width of 700 W or more, Until now, there has been no report on industrial processing of wide steel strips or wide foil strips with a thickness of less than 0.1 mm. Although there are reports that steel strips with a thickness of 0.05 aa were treated in a vertical continuous light annealing furnace, there have been no reports of bright annealing of wide steel strips with a width of 700 mm or more (for example, Special Public Service 53-35
848. (See Publication No. 54-36887).

As described above, the reason why wide FJ steel strips and wide foil strips cannot be processed in a horizontal continuous bright annealing furnace is because bright annealing causes shape defects in the treated material, and the following two are the main reasons for this. be.

■ The first factor is that compressive thermal stress is generated in the copper strip during the cooling process of the steel strip during bright annealing.

Since this compressive thermal stress is determined by the plate temperature gradient in the longitudinal direction of the plate, it becomes maximum at the early stage of cooling when the heating zone shifts to the cooling zone. For this reason, during the early stage of cooling, the copper strip tends to undergo bending deformation (canoeing) in the sheet width direction, as well as local bending and buckling (if this degree is large, permanent deformation remains and may result in poor shape). In particular, wide thin steel strips and wide foil strips have low rigidity in the width direction, so it is essential to suppress compressive thermal stress during the early stage of cooling.However, conventional technology has not been able to sufficiently achieve this. As a result, continuous bright annealing of wide thin steel strips and wide foil strips could not be performed.

This situation will be explained in detail below.

In the horizontal continuous bright annealing furnace, the above-mentioned initial stage of cooling corresponds to cooling in the first slow cooling zone, but the structure of the first slow cooling zone uses the cooling tube 19 as described above,
Air is caused to flow through the cooling tube 19, and cooling is performed by radiation between the surface of the cooling tube 19 and the steel strip 1, and the cooling temperature of the steel strip 1 is controlled by the cooling tube 1.
This was done by controlling the surface temperature of the cooling tube 19 by changing the amount and temperature of air flowing through the cooling tube 9.

However, the forced cooling method using the cooling tube 19 described above has poor stability at high temperatures.
The soaking temperature of wide thin steel strips and wide foil strips is 1000 to 110.
Because the temperature was as high as 0°C, stable slow cooling could not be performed and overcooling occurred, resulting in defective shapes.

■ The second factor is that bending stress is generated in the copper strip by the rolls in the furnace.

At high temperatures in the initial stage of cooling, the yield stress of the steel strip is extremely low; however, if the steel strip is bent along a roll with a small curvature during this process, the bending stress generated in the thickness direction will cause the steel strip to yield. When the stress is exceeded, plastic strain occurs in the steel strip in the thickness direction, and the plate may remain plastically deformed. In this way, at high temperatures in the initial stage of cooling, the relationship between the plate thickness and the roll diameter is an important factor in the shape defects of the processed material, but in conventional technology, the roll diameter is not determined with this in mind, resulting in shape defects. was occurring.

The present invention aims to solve these problems.

<Means for Solving the Problems> The continuous annealing method for wide thin steel strips and wide foil strips according to the first invention is a horizontal type having a heating zone, a first slow cooling zone, and a second slow cooling zone sequentially arranged in series. In the bright annealing method for wide thin steel strips and wide foil strips using a continuous bright annealing furnace, the steel strip is slowly cooled in the first slow cooling zone only by radiant heat transfer from the steel strip without using forced cooling means. , and the furnace temperature of the first slow cooling zone is set to a temperature at which the steel strip is not supercooled.

Further, the continuous annealing apparatus for wide thin steel strips and wide foil strips of the second invention is a horizontal continuous bright annealing furnace equipped with a heating zone, a first slow cooling zone, and a second slow cooling zone in series in sequence. The slow cooling zone is constructed using the same heat insulating material as the heating zone and has the same furnace body structure as the heating zone, and the first slow cooling zone has the same furnace temperature control device and furnace temperature control method as the heating zone. That's what happens.

Effect> The steel strip is slowly cooled in the first slow cooling zone that transitions from the heating zone to the cooling zone by only transferring radiant heat from the copper strip without using forced cooling means, and Since the furnace temperature of the cold zone is set to a temperature at which the copper strip does not overcool, the slow cooling of wide thin steel strips and wide foil strips at high temperatures can be performed stably and without overcooling. It is possible to suppress the compressive thermal stress that occurs in

In addition, the first slow cooling zone is constructed using the same heat insulating material and the same furnace structure as the heating zone, and the furnace temperature control device and furnace temperature control method of the first slow cooling zone are the same as those of the heating zone. Since the furnace is equipped with the following equipment, it is possible to accurately and stably control the furnace temperature of the first slow cooling zone in accordance with the furnace temperature control of the heating zone.

<Example> One embodiment of the present invention will be described based on FIG.

FIG. 1 is a cross-sectional view of the horizontal continuous bright annealing furnace of the present invention in the furnace length direction.

In the figure, 2 is a heating zone that heats the steel strip 1 to the annealing temperature, 3 is a first slow cooling zone provided continuously to the heating zone 2, 4 is a joint zone, and 5 is a convection-type second slow cooling zone using atmospheric gas. It is a cold zone.

The first slow cooling zone 3 is constructed using the same heat insulating material and has the same furnace body structure as the heating zone 2 for convenient furnace temperature control.
The furnace temperature control device 6 is also equipped with the same equipment as the heating zone 2 and is controlled by the same control method, that is, the heater 7 of the furnace temperature control device 6
, the furnace mtP4 moderator 8, the furnace temperature control device 9, etc. are the same as those installed in the heating zone 2, and are controlled by the same control method.

As a result, since the furnace body conditions of the first lehr-cooling zone 3 and the heating zone 2 are the same, it is possible to accurately and stably control the furnace temperature of the first lehr-cooling zone 3 following the furnace temperature control of the heating zone 2. It becomes possible.

Thus, the high-temperature steel strip 1 conveyed from the heating zone 2 to the first slow cooling zone 3 is gradually cooled by radiant heat transfer to the inner wall of the first slow cooling zone 3, but during slow cooling, In order to prevent overcooling of the steel strip 1, the furnace temperature of the first slow cooling zone 3 is set to a temperature that does not cause overcooling.

For example, if the furnace temperature of the heating zone 2 is 1100°C and the furnace temperature of the first slow cooling zone 3 is 1050°C, the steel strip 1 is 1 in the first slow cooling zone 3.
It is never cooled below 050°C. In this way, overcooling in the initial stage of cooling can be prevented, the steel strip can be slowly cooled stably, and compressive thermal stress acting on the steel strip can be suppressed.

Next, even if the copper strip is slowly cooled using the above-mentioned slow cooling means, if the slow cooling rate is too low, the length of the first slow cooling zone 3 will become excessive, which is not desirable in terms of equipment. The progress of oxidation on the surface of the steel strip during the cooling process also causes quality defects due to a decrease in brightness.

Therefore, it is necessary to set the annealing rate as high as possible without causing supercooling, but since wide thin steel strips and wide foil strips have low rigidity in the width direction, in addition to the annealing method described above, annealing is started. A support roll 10 is placed near the point. The support rolls 10 are preferably arranged at short pitches at the outlet of the heating furnace 2 and the inlet of the first slow cooling zone 3, as shown in FIG.

By doing so, the apparent rigidity of the copper strip in the upper board width direction can be increased, deformation in the board width direction can be suppressed, and occurrence of shape defects can be prevented. In addition, in a horizontal furnace, the steel strip is always subjected to its own weight in a downward direction, so the steel strip does not usually deform upward in the width direction, but instead deforms upward in a concave manner. Therefore, there is no need to press the upper part of the steel strip with a roll, and it is sufficient to simply install a support roll IO that supports the lower surface of the steel strip. In addition, the support roll 10 does not actively support the copper band,
Place the steel strip along the catenary in the furnace. Note that the catenary of the steel strip in the furnace is formed by hearth rolls 11 and 12.

Next, the outer diameters of the support roll 10 and the hearth roll 12 of the second convection cooling zone are determined as follows.

-a, the bending stress in the plate thickness direction caused by bending the steel strip along the roll outer diameter needs to be suppressed to a value that does not cause plastic strain. That is, since the strain ε generated in the steel strip is expressed as ε-t/D when the bending radius is larger than the plate thickness t, the bending stress σ of the outer skin of the steel strip is expressed as σ-E-t/ D (E is Young's modulus of the steel strip), and the roll outer diameter must be determined so that σ is a value smaller than the yield stress of the steel strip.

As a result of various experiments based on this idea, the present inventors found that
Plate width 700-1250In+1, plate thickness 0.02-0.2
For wide width 'III steel strips and wide foil strips of wa, the outer diameter of the support roll 10 and the hearth roll 12 of the convection type second annealing zone must be 200 or more, and 600 m is sufficient. I found it.

Furthermore, specific examples of the present invention will be described. 1st
In the annealing furnace of the present invention shown in the figure, the plate width is 1000 mm and the plate thickness is 0.0 mm.
Bright annealing of a 5ma+ stainless steel wide thin steel strip, heating temperature of the steel strip to 1100°C1 Furnace temperature of the first slow cooling zone to 1050°C
'C, and the support roll and the hearth roll of the second slow cooling zone had an outer diameter of 350 mm.The flatness of the steel strip was measured, and the average was 0.5aIffl.
Met.

On the other hand, in the conventional horizontal continuous bright annealing furnace, the plate width is 500.
III11 After bright annealing a 0.05mm thick stainless steel narrow width 'gi steel strip, the flatness was similarly measured and found to be 5mm on average. As described above, the flatness of the present invention was significantly improved compared to the conventional boiling technique, and it was possible to prevent shape defects.

<Effects of the Invention> According to the present invention, it is possible to extremely effectively suppress the occurrence of shape defects that occur during the cooling process after annealing in continuous bright annealing of wide thin steel strips and wide foil strips, so that flatness can be improved. It is possible to stably and mass produce bright annealed materials of wide thin steel strips and wide foil strips with excellent properties.

[Brief explanation of the drawing]

Fig. 1 is a sectional view in the furnace length direction showing one embodiment of the horizontal continuous bright annealing furnace of the present invention, Fig. 2 is a schematic explanatory diagram of a general horizontal continuous bright annealing equipment, and Fig. 3 is a conventional horizontal bright annealing furnace. FIG. 4 is a sectional view in the furnace length direction of a typical horizontal continuous bright annealing furnace, and FIG. 4 is a sectional view taken along the line 1-1 in FIG. 3. 1... Steel band, 2... Heating zone, 3...
1st slow cooling zone, 4... Joint zone, 5... Second slow cooling zone, 6... Furnace temperature control device, 10... Support roll, 11, 12... Hearth roll. Patent applicant: Kawasaki Steel Corporation

Claims (4)

[Claims] (1) In a bright annealing method for wide thin steel strips and wide foil strips using a horizontal continuous bright annealing furnace equipped with a heating zone, a first slow cooling zone, and a second slow cooling zone in series, in the first slow cooling zone, The steel strip is slowly cooled only by radiant heat transfer from the steel strip without using forced cooling means, and the furnace temperature of the first slow cooling zone is set to a temperature at which the steel strip is not supercooled. Continuous bright annealing method for wide thin steel strips and wide foil strips. (2) In a horizontal continuous bright annealing furnace equipped with a heating zone, a first slow cooling zone, and a second slow cooling zone in series, the first slow cooling zone is connected to the heating zone by using the same heat insulating material as the heating zone. A horizontal wide thin steel strip and a wide foil strip constructed in the same furnace body structure and characterized in that the first slow cooling zone has the same furnace temperature control device and furnace temperature control method as the heating zone. Type continuous bright annealing furnace. (3) The horizontal continuous bright annealing furnace according to claim 2, wherein a support roll is disposed near the annealing start point in the horizontal continuous bright annealing furnace. (4) The horizontal continuous bright annealing furnace according to claim 3, wherein the outer diameter of the support roll and the hearth roll of the second annealing zone is in the range of 200 mm or more and 600 mm or less.