JPS6254034A - Continuous annealing installation for steel strip - Google Patents

Abstract

PURPOSE:To provide a continuous annealing installation which can heat a steel strip in a non-oxidizing state by disposing plural heating burners which can form non-equil. regions having an intermediate reaction product of combustion and having no free O2 in flames to the outlet side region of a direct firing heating zone in particular. CONSTITUTION:The flames of the reduction type heating burners disposed in such a manner that the above-mentioned non-equil. regions can be formed are made to collide against the steel strip S to heat the steel strip S in a reduction state on the outlet side of the direct firing heating zone (a). The steel strip S fed in the non-oxidizing state into a holding zone (b) is held in a reducing atmosphere and is then subjected to quick cooling essentially consisting of liquid cooling in a cooling zone (c). The steel strip S is pickled in an intermediate pickling installation (d) to remove the oxide film formed by the quick cooling in succession of the quick cooling and is then subjected to an overaging or tempering treatment in an overaging treatment zone (e). The steel strip S emitted from the zone (e) is rolled by a temper rolling mill (g) disposed on the outlet side of the final treating zone. Efficient continuous annealing is thus made possible without posing the problem of oxidation of films, etc.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to continuous annealing equipment for steel strip.

[Conventional Technique vPi] As a heating method for a continuous annealing furnace, an indirect heating method using a radiant tube and a direct heating method are known.

Of these, the latter direct-fire heating method has superior heating capacity compared to the indirect heating method, and has the advantage of being able to burn out cold rolling oil, eliminating the need for cleaning equipment, and is widely used in hot-dip galvanizing lines. It is also used in continuous annealing lines for electrical steel sheets.

However, there is a major problem in that the steel strip of the conventional u'j fire heating heating method is severely oxidized, resulting in roll beak-up. In contrast to the conventional direct fire heating method, the so-called non-oxidizing direct fire heating system 11, the h° method, was developed in
No. 8-44133, Japanese Patent Publication No. 59-29651, etc. have proposed continuous annealing equipment for cold-rolled steel strips. This method reduces the air ratio of each combustion control zone (1, 4 end, -0, 6) depending on the strip temperature (Max, 900℃). This method involves heating while suppressing the oxidation of

However, although this method claims to be a non-oxidizing method, it is actually a weak oxidizing method, and the air ratio is low! Since the oxidizing gas GO, , lI20 is contained in the combustion generated gas of less than 0, the oxidized DI2 thickness after heating is 50A° of the original plate.
Therefore, when applying this method to continuous annealing equipment, the water in the soaking zone following the heating zone should be filled with highly concentrated melon (approximately 20% culm). ), or put a treatment zone called strong reduction zone on the first stage of pyrophoric heating and 3), :;, purulent water''; (approximately 5
0% or more (1-)
do not have.

In addition, continuous annealing equipment in Akiuchi tends to be larger in order to reduce manufacturing costs, but in αbi, a direct-fired heating zone like the one described above is used! When configured with buses, the furnace height becomes high, causing flapping of the steel strip and difficulty in controlling the furnace pressure.In an open-fire heating zone with multiple buses, roll pickup occurs from the inside of the heating furnace. As a result, the surface quality of the steel strip becomes ML, .<H+h.

In order to prevent the a-rubbick-up of such furnace rolls, for example, an isolation chamber for accommodating the furnace rolls as shown in Japanese Patent Application Laid-Open No. 53-54100 is provided, and the inside of this isolation chamber is maintained. -> You have to take complicated measures such as putting yourself in a strong environment. Even when such a roll protection method is adopted, it is very difficult to properly move the roll isolation chamber between the inside of the direct-fired furnace and the high-temperature furnace f'1F, such as a direct-fired heating furnace. In order to create a protective atmosphere of -100 liters, it is necessary to supply a huge amount of 8 liters of protective atmosphere gas, which is not practical.

[Steps for Solving the Problem] The present inventor has made repeated studies in view of such conventional problems, and as a result, there is a non-f-equilibrium region in the flame, that is, combustion intermediate products (intermediate ions, radicals, etc.) exist [L
A heating burner that forms a region where no oxygen exists is extremely effective in non-oxidizing heating of the steel strip, and by placing it in the heating zone under specified conditions, the steel strip is heated in a non-oxidizing and reducing state. I found out what I can do. The present invention applies such a reduction type heating burner to a direct-fire heating zone, and further combines such a heating zone with a cooling zone using a specific cooling method, thereby preventing problems such as oxide films from forming on the steel strip. This equipment is designed to efficiently perform continuous combustion and IJ without any problems.

That is, in the first invention of the present application, a direct heating zone, a soaking zone, a liquid cooling zone, a cold H1 zone, an intermediate pickling facility, and an overaging treatment zone are provided in this order from the entry side, and a final treatment zone is provided. A 7'tl rolling mill is arranged on the exit side of 11. The direct-fired heating zone has at least 4F of combustion intermediate reaction products in the outlet region, and a
Its J and C final features include the arrangement of a plurality of heating burners capable of forming a V-equilibrium region in the flame.

Further, the second invention of the present application is characterized in that a t-heat zone is provided in front of the open-fire heating zone L, and the third invention of the present application is characterized in that a t-heat zone is provided in front of the open-fire heating zone. It is characterized by having a tropical region.

[Effect 1] In the direct flame heating zone of the present invention, there is a non-equilibrium region in the flame, that is, a region where combustion intermediate products are present [and where there is no acid release (non-equilibrium region)]. A heating burner is used in which a heating burner can be formed. In such a heating burner, combustion in the flame is almost complete (1, cQ2. II□0. N2゜1
12. The region containing GO, etc., that is, the quasi-Y equilibrium gas, is oxidizing, whereas the non-Y equilibrium region containing intermediate ions, radicals, etc. exhibits reducing properties, and the flame is not oxidized. The steel strip can be heated in a reducing state by impacting the steel strip in the equilibrium region.

In the continuous combustion equipment of the present invention, the steel strip is heated in a refractory heating zone, or in this heating zone, it is reductively heated by a reduction heating burner disposed at least in the outlet area, and the steel strip is kept in a non-oxidized state. Sent out to soaking zone. In this direct flame heating zone, the rolling oil that has adhered to the surface of the steel strip (-1) is burned and removed as it is heated. In the soaking zone that follows, the steel strip is soaked in a reducing atmosphere, but the steel strip is in an almost non-oxidized state during this soaking zone. Moreover, the subsequent intermediate pickling can also remove a new oxide film generated by liquid cooling, so the atmosphere needs to be weakly reducing (H2: 2 to 5%) to maintain a non-oxidizing state. In the subsequent cooling zone, quenching mainly using liquid cooling is performed, and the steel strip is cooled to almost room temperature or to overaging or tempering temperature with hot water, etc. Next, the steel strip is passed through intermediate pickling equipment to remove the oxide film produced by the quenching. The steel strip is removed and then subjected to overaging or tempering treatment in an overaging treatment zone, and the steel strip that leaves the final cooling zone is subjected to Terasuso rolling in a temper rolling mill.

The annealing equipment of the present invention uses a direct-fired heating zone capable of non-oxidizing heating, and although it uses liquid cooling such as rapid hot water or water cooling after heating and soaking, it has excellent surface quality. It is possible to obtain a steel strip. That is, when cooling after heating and equalization is performed by water cooling, the formation of an oxide film on the surface of the steel strip is inevitable. In the combination of a conventional direct-fired heating furnace and liquid cooling system, even if a reduction furnace is installed after the direct-fired heating furnace, it is inevitable that an oxide film will remain.
Since an oxide film is further generated by liquid cooling, the oxide film remains even if oxide film removal equipment such as pickling equipment is installed afterwards.
It was difficult to ensure the surface quality of the product. This tendency is especially true for high-Si materials that produce strong oxide films.
, Mτ−0P.

It is noticeable in Cr, Ti materials, etc. In this regard, in the present invention, since the steel strip is sent to the soaking zone-cooling zone in a non-oxidized state from the direct fire heating zone capable of reductive heating, the oxide film formed by rapid cooling is removed in the intermediate pickling equipment following the cooling zone. This is sufficient, and the oxide film can be reliably removed by pickling. In particular, in the present invention, an intermediate pickling facility is provided in front of the overaging treatment zone instead of a final pickling facility;
The effect of removing the oxide film is enhanced. In other words, in pickling, it is preferable to use a strong acid in order to enhance the oxide film removal effect, but when a strong acid is used, there is a problem that Fc(OH)z, which is 41° harmful to the steel strip surface treatment, is generated. . If pickling is carried out on the final side, that is, on the back side of the over-aged zone, the generated Fc(OH)2 remains on the surface of the steel strip, which causes various problems in the chemical conversion treatment properties of the steel strip. This will cause

In this regard, in the present invention, in which pickling equipment is installed in the front of the intermediate pickling, that is, the overaging treatment zone, even if Fc(OH)2 is generated by pickling, this continues in the overaging treatment zone where the reducing atmosphere in the furnace is removed. Since it is reduced by gas, there is no need to worry about Fe(OH)2 remaining, and therefore pickling with a strong acid has a 1+1 capability. Furthermore, when the steel strip is annealed at a high temperature using a direct reduction fire, a small amount of carbon may be observed on the surface of the steel strip, but such carbon can be appropriately removed by intermediate pickling.

In addition, in the equipment of the present invention, non-oxidative heating in the heating zone is i.
As a result, the H2 concentration in the subsequent soaking zone can be suppressed to a very low level, and in combination with the fact that the heating method is an open flame method, it is possible to expect an energy saving effect compared to the conventional continuous annealing furnace for camphor wood.

In addition, in the second invention of the present application, an r-tropic is provided on the 11η plane of the above-mentioned direct-fired heating zone, and the steel strip is directly heated in this -r-tropic by the exhaust gas introduced from the direct-fired heating furnace. You will be led to a heated zone. In continuous heating annealing, the heating time is short, so the heating time effect is small, and the heating time is less than that in batch annealing.
! The operation is performed by setting the temperature relatively high. In particular, in equipment equipped with a reduction direct-fire heating zone such as the present invention, high-speed annealing is performed as LI-like operation, so the heating temperature is set higher. There is a strong tendency to set it to 1'l. Therefore, by preheating the steel strip in such continuous annealing treatment of the steel strip, the load for heating in the direct heating zone is reduced, and appropriate high-temperature and high-speed annealing becomes possible.

In addition, in the heating zone using the direct heating method, the heating speed is high, so the heating temperature (final heating temperature) tends to be higher [1] than in the indirect heating method, which requires extra energy. By providing a tropical zone and performing r-heating of the steel strip, there is an advantage that the slope of the steel strip temperature can be lowered and the heating temperature does not need to be lowered more than necessary.

In addition, even if the surface of the steel strip is oxidized to some extent due to p-heat, it is equipped with a direct-fired heating zone that can reduce this oxidation, and is also equipped with an intermediate pickling zone, so that it can heat the steel strip to a high temperature of 250 to 600 degrees Celsius in the preheating zone. The rolling oil adhering to the belt surface can be removed by combustion, and in combination with the rolling oil removal in the direct-fire heating zone, good burn-off properties can be achieved.

Furthermore, in a direct-fired heating zone, the zone where the reduction burner is installed must maintain a constant combustion state in order to reductively heat the surface of the steel strip. Although it may be necessary to use methods such as extinguishing the heating burner in other heating zones to control the load, by providing an auxiliary combustion function to it, it is possible to reduce the heat load, especially when heating thin materials. Adjustment becomes possible.

Furthermore, in the third invention of the present application, a cleaning facility for the surface of the steel strip is further provided in front of the tropical zone, and in this cleaning facility, old iron powder "t" attached to the surface of the steel strip is removed. Rolling oil and iron powder (rolling chips, etc.) are usually attached to the surface of the steel strip after cold rolling.As mentioned above, the rolling oil is burned and removed in the direct heating zone or preheating zone.
The iron powder is not removed and accumulates in the furnace, or circulates in the furnace together with the furnace atmosphere gas and gets caught between the roll and the steel strip, causing scratches on the product surface. In the present invention, such iron powder is removed by the cleaning equipment. Also high Si
When continuously annealing steel strips such as , P, Mn, Ti, Cr-, etc., these produce oxide films that are difficult to oxidize.
The air ratio of the combustion gas may be lowered to reduce oxidation caused by heat and direct flame heating (heating before reductive heating). In this case, the burn-off characteristics of the rolling oil on the surface of the steel strip in tropical or direct-fired heating zones will be slightly lower, but the cleaning equipment described above will compensate for this low burn-off characteristic. , an appropriate rolling oil removal effect can be obtained.

[Example] Figures 1 and 2 show an example of the present invention, and in order from the entrance side, there is an open heating zone (a), a soaking zone (b), and a cooling zone (
C), an intermediate pickling facility (d), an overaging treatment zone (e), and a final cooling zone (f) are provided, and an outlet side loopam (h) is interposed on the outlet side of this final cooling zone (f). Tempazal (g) is installed.

In the direct-fired heating zone (a), the reduction type heating burner is provided at least in the outlet region thereof, and the non-reduction type heating burner (-) is provided on the right side of the heating zone on the inlet side. Even if the surface of the steel strip is oxidized by the diffusion burner, it can be reduced and sent to the subsequent soaking furnace in a non-oxidized state. The reduction type heating burner has 1-1. However, this type of burner has less heat damage than conventional non-reducing heating burners, and in order to ensure the necessary rapid heating, it is necessary to install the burner tightly. It needs to be placed in For this reason, it is preferable to arrange the reduction type heating burner within the necessary minimum range.

When the direct-fired heating zone (a) is made up of a plurality of buses as in this embodiment, the reduction type heating burner is installed in the direct heating zone (a) more specifically than in each outlet area of the plurality of buses. In the case of a fire-heating furnace, the oxidation of the steel strip causes the problem of roll pickup in the roll itself in the furnace, and in order to avoid such problems and send the steel strip to the soaking zone (b) in a non-oxidized state. A reduction type heating burner may be arranged in the outlet area of each bus, and the steel strip may be brought into contact with a threading roll in a non-oxidized state and sent out of the silica furnace.

No. 4-1 shows the structure of such an open-fire heating zone. In the figure, (I) is the first pass, (II) is the second pass, (8a) to (8d) are the passing rolls in the furnace, and (S) is the steel strip. In such a configuration, the heating area of the exit side passing roll (8b) and (8b) direct+if of each pass is as follows:
-L A heating burner group (X) including a plurality of reduction type heating burners (9) described above in the line direction is arranged. on the other hand,
A heating burner group (Y) of non-reducing type heating burners, which have been commonly used in the past, is arranged in the residual oil heating region.

Figure 8 shows the first pass (I) in such an open flame heating zone.
The graph shows the transition of oxide film paste and steel strip temperature at It can be seen that in the side region (reduction heating region), the original plate base is reduced to the oxidation 11Q thickness and sent to the subsequent second bus (II) in a substantially non-oxidized state.

FIGS. 6 and 7 show an example of the above-mentioned reduction type burner, and this heating burner has a plurality of combustion airs arranged at intervals in the circumferential direction on the inner wall (6) of a cylindrical burner tile (1). In addition to providing a discharge hole (2), a fuel gas discharge hole (3) is provided in the inner center of the burner, and a combustion air discharge hole (2) is also provided.
) and the fuel gas discharge hole (3) have the following configuration.

b) Add an angle θ of 60° or less to the tangent to the inner circumference of the burner tile in the air supply direction of the air discharge hole (2).

) The burner axial inner path #IN of the fuel gas discharge hole (3) and air discharge hole (2) is indicated by (-) if the fuel gas discharge hole is closer to the burner tile outlet 1 side than the air discharge hole. Reverse (
1), -0.10 to +0.25D (D:
Set to "1 diameter" inside the burner.

c) The distance from the air discharge hole (2) to the burner tile outlet (5) is 0.6D to 3D.

The heating burner configured in this way has an air ratio of 1.0 or more F.
When used in this way, an unbalanced region is formed in a predetermined range within the flame. That is, in such a heating burner, rapid combustion is achieved by the swirling flow of combustion air from the air discharge hole (2) and the fuel scum discharged from the center of the burner, and if ]
Therefore, the combustion intermediate IL: products are mixed with I; [Nami[L] to form a region that does not contain unreacted free oxygen, that is, a non-P-equilibrium region. Figure 1O shows an example of measurement using an ion detection probe in the unbalanced region in the flame formed by such a heating burner.The reason why the current value measured by the probe is high is that the ion intensity is high, and therefore the ion intensity is high, and therefore it is detected in the middle of combustion. Many products: I have an alpha taste of their existence.

According to this, the burner outlet L1 is located in a predetermined range outward (
A non-balanced region is formed, and the outside of this region contains C02. which has almost completed the reaction. ! It is a quasi-γ, equilibrium region containing hO, N2, etc.

Figure 11 shows the reductive heating characteristics of such a heating burner, that is, the limit temperature that can be heated without oxidation (the limit temperature for a thin plate of negative conducting steel), and shows the reduction heating characteristics of such a heating burner.
．． It has been shown that steel strip can be heated up to about 900°C in 95 degrees centigrade.

Further, in the present invention, in addition to the heating burner described above, for example, a 1:17 radiant cup burner can be used. In order to carry out a rapid combustion reaction, this burner rapidly burns a mixture of air and fuel gas using the spherical burner tile, which heats up the inner surface of the burner tile and causes radiant heat transfer. It is heated as L, and has the characteristic that a high heat flux can be obtained in a region where the temperature of the heated object is high. By performing combustion in this burner at an air ratio of 1.0 or more, an unbalanced region is formed in the flame.

However, since this radiant burner uses a mixing method of combustion air and fuel gas, it cannot generate t-heat from the combustion air, and cannot generate e-heat from the air, so non-oxidation heating is limited to about 750℃. However, it has the disadvantage that it cannot be applied in cases where heating in a higher temperature range is required. In this regard, in the heating burner shown in Fig. 6, since r-hot air can be used, oxidation heating is possible up to about 900°C, and by using r-hot air in this way, the flame temperature can be increased. Therefore, compared to a radiant burner, the quaternary action itself due to the intermediate reaction product can be effectively reversed.

In the direct heating zone, the flame of the reduction type heating burner as shown in Fig. 4 impinges on the surface of the steel strip (S) approximately at right angles to the steel strip (S) in its non-equilibrium region. It is arranged like this. In heating burners used in conventional direct-fired heating furnaces, such as NOF, the non-)P-equilibrium region of the burner is not formed in such a manner that it can be clearly distinguished from other regions. Therefore, if a visible flame comes into direct contact with the steel strip, the surface of the steel strip will be significantly oxidized. For this reason, the steel strip is generally arranged so that the flame is formed in the width direction of the steel strip and skewered so that the flame does not directly touch the steel strip. On the other hand, in the present invention, the steel strip is heated by a non-equilibrium region formed in the longitudinal direction of the burner flame. The burners are arranged so that they collide in the non-equilibrium region.

The soaking zone (b) following the direct heating zone (a) uses an indirect heating method using radiant tubes, and is basically the same as the conventional soaking zone. However, in the continuous annealing furnace of the present invention, the direct-fired heating zone (a) has a reducing capacity of 41, the steel strip is sent to the soaking zone (b) in a non-oxidized state, and intermediate pickling is provided subsequent to the IL. In the soaking zone of the tank, the atmosphere is such that it does not oxidize the steel/JIP, that is, H2: 2 to 5%, usually preferably 3.
An atmosphere of ~4% is sufficient.

In the subsequent cooling zone (c), the steel strip (S) is immersed in water to be rapidly cooled. Under water, the steel strip is sprayed with a nozzle to remove the vapor film.

The intermediate pickling equipment (d) is pickling N! ! (10), Rinse Kasu (
11), a dryer (12), etc.
For example, pickling treatment using HCfi 5% for about 40 to 1.5 seconds and rinsing treatment using 80° C. water are performed.

In the overaging treatment zone (e), the steel strip (S) is overaged or tempered in a weakly reducing atmosphere.

In addition, it is preferable that the temper mill (g) uses a hard chrome roll as its work roll. This roll is less likely to cause indentation flaws due to the edges of the steel strip, and therefore the occurrence of flaws on the surface of the steel strip due to roll flaws can be appropriately prevented by IF, thereby making it possible to perform cycle-free continuous annealing of the steel strip width. In other words, in the past, in order to avoid the effects of roll flaws on the steel strip as described above, the steel strips to be processed were sequentially connected in a ring shape. By using hard chrome rolls, it is possible to be freed from such problems, and it becomes possible to perform a continuous annealing operation that connects steel strips regardless of whether they are wide or narrow.

FIG. 2 shows another embodiment of the present invention, in which a preheating zone (i) (two passes) is provided in front of the open heating zone (a). Direct-fired heating zone (a) or soaking zone (b) or its combustion exhaust gas is introduced into this pre-heating zone (i), and the t of the steel strip (S) is
Heat is supposed to be done. According to the studies of the present inventors, the oxidation of the steel strip is governed by the thermal temperature and the air ratio when the combustion exhaust gas used is generated, and the air ratio during combustion is determined depending on the thermal temperature. By using different combustion exhaust gases, it is possible to heat the steel strip with almost no oxidation.Basically, as shown in Figure 9, when preheating the steel strip to a temperature below 280°C, When preheating the steel strip to 280°C or higher using combustion exhaust gas generated at an air ratio of 1.0 F or higher, use combustion exhaust gas generated at an air ratio of less than 1.0 to maintain the preheating temperature of the steel strip. Regardless of the temperature, it has been found that preheating can be carried out efficiently in a non-oxidized state.

In this way, in the tropical zone (i), non-oxidation or heating is possible by regulating the air ratio of the combustion gas, but in the present invention, the reduction effect of the oxide film can be obtained in the subsequent direct flame heating zone (a). Moreover, since it is equipped with intermediate pickling, it is possible to remove the newly formed oxide film due to liquid cooling, so a certain degree of oxidation is allowed in the preheating zone (i), and as a result, the chain line in Figure 9 As shown in (a), it is possible to increase the permissible temperature by about 100°C, which makes it possible to increase the permissible temperature by about 100°C, which allows even an air ratio of about 1.3 to
It is possible to generate r-heat of about 00°C, and it is possible to perform the combustion removal action of the steel strip rolling oil in the tropical tropics (i).

FIG. 3 shows another embodiment of the present invention, in which tropical (i
) is provided with cleaning equipment (j) whose main purpose is to remove iron powder via an inlet looper (k). Since this cleaning equipment (j) is mainly intended for removing iron powder, a simple equipment is sufficient. Figure 5 shows an example of such a cleaning setup, where (13) is an alkali tank, (14) is a scrubber (brush roll), (
15) is its backup roll, (16) is a hot water spray nozzle, (17) is a hot water rinsing tank, and (18) is a dryer.With this level of cleaning equipment, iron powder can be removed in 1 minute.

No. 5 and No. 10 are comparative examples of NOF furnace, reduction furnace, quenching, and pickling. As is clear from the comparison with such comparative examples, according to the continuous annealing equipment of the present invention, the formation of oxide film is significantly suppressed compared to the conventional NOF method, and a product with excellent chemical conversion treatability etc. can be obtained. I understand that.

For liquid cooling in the present invention, an appropriate liquid can be used, and cooling can also be performed by cooling without lowering the temperature to room temperature.

Further, as the temper rolling mill of the present invention, a tension leveler of a temper mill can be used, or a temper mill and a tension leveler can be installed together.

It is also possible to provide a plating device such as galvanizing after cooling.

Next, there are fuel gas nozzles protruding from the heating burner shown in FIGS. 6 and 7, and in this embodiment, fuel gas discharge holes (
3) is formed.

Right on such a heating burner, its air discharge hole (2)
The reason why the air supply angle θ is set at By circulating, combustion is promoted and an appropriate non-V equilibrium region can be formed. By setting the air supply angle θ to a maximum of 60°, preferably from 20 to 40°, a stable swirling property of the airflow can be obtained.

When the burner axial distance N between the fuel gas discharge hole (3) and the air discharge hole (2) is on the (-) side, the gas temperature is high and combustion intermediate products are also highly distributed over a wide range. On the other hand, TLm02<unreacted 02) tends to be distributed long in the axial direction. The present invention [! In order to appropriately form the target non-equilibrium region, it is necessary to minimize the remaining distance of this play 11!02 in the burner axial direction, and its limit is -0, ID.

If N is on the (1) side, a proper non-balanced slope will be formed, but if it is too large, the inner end wall of the burner tile will be heated to 1400°C.
It is not dangerous because it is heated more than that, and the limit is +0.25D in order to protect the SiC on the inner end wall of the burner tile. Figure 12 shows the burner axial distance from the burner outlet [:1 and the burner axial distance in the burner tile when the burner axial distance N between the fuel gas discharge hole (14) and the air discharge hole (13) is -0.25D. The relationship between gas temperature, 02 concentration, and ion strength was investigated, and according to this, when N is on the (-) side, the remaining distance s L o in the axial direction of free m O2 is large. has been shown to exist.

Figure 13 shows the bar ten-axis inner path J of the fuel gas hole and air discharge hole.
This shows the relationship between IIN and the axial remaining distance Lo of free 02 and ρ). According to this, N is 10, which is less than ID (=)
As it increases toward the side, Lo suddenly becomes larger, and therefore, -0, 1D becomes the limit on the (-) side.

On the other hand, FIG. 14 shows the relationship between the burner axial distance from the burner output [1], the 02 concentration, the ion strength, and the gas temperature when N is +0.1D.

According to this Fig. 13 and 'dS14, if 5N is on the (1) side, there is no problem with the 02 concentration, and an appropriate non-gamma balance region is formed at a distance of 0.5DtJl from the burner output L1. has been done.

However, if N is increased to (1) t, the burner tile inner end wall (4) will be heated, so the relationship between the distance N and the temperature Tb of the burner tile inner end wall (4) in Fig. 15 will change. As shown in the graph, Tb is 1400℃ at +0.25D
Therefore, it is preferable to consider that the material of the inner end wall is SiC, and to set it to +0.25D or less, which is the heat resistance limit. From the above, regarding the burner center axis distance @H of the combustion gas discharge hole and air discharge hole, -〇, ID ~ 0
．． It is preferable to set it as the range of 25D.

The distance 1i1L from the air discharge hole (2) to the burner tile outlet 11 (5) is closely related to the formation range of the unbalanced region. In other words, if the height exceeds 3D, the unbalanced area will be formed only in the area immediately after the burner tile exit [1], which is not preferable. On the other hand, if L is less than 0.6D, the flame will become a petal-shaped flame immediately after the burner tile exits, making it impossible to stably obtain an appropriate imbalance region on the burner center axis. Therefore, it is preferable to set L in the range 0.6D to 3.0D.

When continuously heating a thin steel plate, burner tile [1 (5)
The i7b fil of the steel plate and steel plate is set to a certain value [(usually 100...
■If the rod degree is not greater than 1-), there is a risk that the steel plate will come into contact with the burner during threading. Therefore, 41.1.
It is preferable that the − surface area is formed in as wide a range as possible, including the steel strip passing position located at a predetermined distance from the burner outlet [−1 side. Figure 16 shows the relationship between the distance fJtL and the distance L-n from the burner outlet [1 to the end of the unbalanced region (the end on the anti-burner side, for example, point A in Figure 14). . According to this, when L exceeds 3D, the non-equilibrium region is formed only immediately after the exit of the burner tile [1], and is hardly formed on the 111f side. As L becomes smaller, the range of non-equilibrium region formation expands, but in the region (X) where L is less than 0.6D, the flame becomes a petal-shaped radial flame immediately after the burner tile exits [=1], An appropriate unbalanced area cannot be stably formed around the burner 1 mesh. From the above, air discharge hole (2)
The distance from to burner tile output Ll (5) is 0.6D
It is desirable to set it as the range of -3.0D.

In addition, in the structure of the heating burner as described in 1- below, if the swirling flow of the air discharged from the combustion air discharge hole (2) is too strong, the temperature outside 4I of the combustion scum on the burner exit side in the burner radial direction will increase. This results in a stable and wide range of non-uniformity.
There are cases where it becomes difficult to form a V-plane region. In such a case, in order to reduce the swirling air flow and make the temperature distribution uniform, the fuel gas discharge hole (3) should be installed so that the injection direction is not perpendicular to the tangent to the outer circumference of the fuel nozzle, and A structure in which the fuel gas flow from the combustion air discharge hole (2) becomes a swirling flow in the opposite direction to the airflow from the combustion air discharge hole (2), that is, a swirling flow that collides with the air flow from the opposite direction, or , a structure in which the fuel gas discharge hole (3) is configured such that the injection direction thereof is in the direction of the burner axis force or a direction inclined to the burner axis direction, and furthermore, the air discharge hole (2)
It is possible to employ a structure or the like that gives an inclination angle (torsion angle) in the burner opening I-1 force direction with respect to the radial direction of the burner tile or in a combination thereof.

In order to expand the heating area by the earthen burner, at least the combustion air discharge hole J/k part of the burner tile (1) is located between the tips [1 side] on the inner wall, and the burner inner diameter Ll is expanded to the 11 side between the tips. In order to facilitate the formation of the expanded angle structure and the air discharge hole (2), a swirling flow path for combustion air along the direction around the burner is provided within the wall of the cylindrical burner tile. It is also possible to adopt a structure in which a plurality of combustion air discharge holes are provided to communicate the swirling flow path with the inside of the burner.

[Efficacy of invention! ! ! According to the present invention, a steel strip can be heated without oxidation by a direct flame heating method, and troubles caused by oxidation of the steel strip such as roll pickup can be appropriately avoided. In particular, according to the present invention, a steel strip which is acid-free and has an excellent surface quality τ1 can be obtained.

In other words, when cooling after heating and soaking is performed using liquid, the formation of an oxide film on the surface of the steel strip is unavoidable. Even if a primary furnace is installed, it is inevitable that an oxide film will remain, and further oxide film will be formed due to water cooling, so it is necessary to install oxide film removal equipment such as pickling equipment afterwards. However, an oxide film remained on the surface of the product, making it difficult to ensure the surface quality of the product. In contrast, in the present invention, the steel strip is sent in a non-oxidized state from the direct-fired heating zone capable of 11i reductive heating to the soaking zone-cooling zone. It is sufficient to remove the oxide film, and the oxide film can be reliably removed by pickling.

In addition, particularly in the present invention, since an intermediate pickling facility is provided in front of the overaging treatment zone 1 instead of a final pickling facility, treatment with a strong acid is possible, and therefore a high oxide film removal effect can be obtained.

Furthermore, in the present invention, since the non-oxidative heating in the heating zone becomes an IIF function, the H2 concentration in the subsequent soaking zone can be kept to an extremely low level, and fuel can be saved.

In addition to the above-mentioned effects, the second invention of the present application reduces the heating f's load in the direct flame heating zone during high-speed annealing, making it possible to perform appropriate high-temperature and high-speed annealing.

In addition, − [According to the above-mentioned principle 111, 250 ~ in the r tropics
The rolling oil deposited on the surface of the steel strip can be burnt and removed by heating at a high temperature of 600°C, making it possible to burn off the rolling oil that has adhered to the surface of the steel strip.
Good oil spread removal and burn-out properties.

In addition, the heating rate is high in the heating zone using the direct flame heating method.
Therefore, compared to the indirect heating method, the heating temperature (final heating temperature) tends to be +' = ゛: + L - I, which requires more energy or heats up the steel. One advantage of heating the belt is that it lowers the gradient of the sheet temperature and eliminates the need to raise the heating temperature more than necessary.
iI will be beaten. More pM! By providing the furnace with an auxiliary combustion function, it is possible to finely adjust the heat load while ensuring direct flame reduction heating in the heating zone.

In addition to the above-mentioned effects, the third invention of the present application can effectively remove iron powder adhering to the surface of the steel strip, which is not removed by heating and combustion.
Appropriately prevent secondary troubles similar to roll pickup caused by iron powder +1. It also has the effect of reinforcing the rolling oil removal effect in tropical areas and direct fire heating zones.

[Brief explanation of the drawing]

FIGS. 1 to 3 are explanatory diagrams showing embodiments of the present invention, respectively. FIG. 4 is an explanatory diagram showing an example of an open-fire heating zone of the equipment of the present invention. FIG. 5 is an explanatory diagram showing the cleaning equipment of the equipment of the present invention. 6 and 7 show an example of a reduction heating burner used in the equipment of the present invention, and FIG. 6 is a longitudinal sectional view;
FIG. 7 is a sectional view taken along the line ■-■ in FIG. FIG. 8 shows the changes in oxide film thickness and steel strip temperature in the first pass of the direct-fired heating zone shown in FIG. 4. FIG. 9 shows the relationship between the air ratio of combustion exhaust gas and the acid-free preheating limit temperature in the t-tropics. FIG. 10 shows an example of the arrangement between the non-equilibrium region forming boxes in the heating burner shown in FIGS. 6 and 7. FIG. FIG. 11 similarly shows the reduction heating characteristics of the heating burner. Figures 12 to 16 show smaller characteristics of the heating burner shown in Figures 6 and 7; 'Jli ti!l from burner outlet 1, 1 and waste temperature, 0□ when distance N at -0,25D
The relationship between concentration and ion strength, Figure 13 shows the distance N between the fuel gas discharge hole and the air discharge hole in the burner axial direction and the free 02
Burner axial remaining distance. Figure 14 shows the relationship between the distance from the burner outlet L when distance N is +1.0, gas temperature, 02 concentration, and ion strength, and Figure 15 shows the relationship between the gas discharge hole and The relationship between the R+i distance N of the air discharge holes and the burner tile rear wall temperature Tb, Figure 16 shows the distance 1lIL from the air ++1 outlet to the burner outlet 11, the distance 5ml L R to the end of the non-P-equilibrium region, and The relationship between the two is completely different. In 1, (a) is an open heating zone, (b) is a soaking zone, (
e) is a cooling zone, (d) is an intermediate pickling facility, (e) is an overaging treatment zone, (g) is a temper mill, (i) is an r-tropic, (
j) is a cleaning device, (9) is a heating burner, R
vinegar. No. 10 ffl No. 11 飄、 工士しょん 12 fig. 7413 fig.

Claims (3)

[Claims] (1) From the entry side, a direct heating zone, a soaking zone, a cooling zone mainly using liquid cooling, an intermediate pickling facility, and an overaging treatment zone are installed in this order, and a temper rolling mill is installed on the exit side of the final treatment zone. is arranged, and a plurality of heating burners capable of forming a non-equilibrium region in the flame, which has combustion intermediate reaction products and does not have free oxygen, is arranged at least in the exit side region of the direct-fired heating zone. Continuous sintering equipment for steel strips characterized by the following. (2) A pre-heating zone, a direct-fire heating zone, a soaking zone, a cooling zone mainly using liquid cooling, an intermediate pickling facility, and an overaging treatment zone are installed in this order from the entrance side, and a conditioning zone is installed on the exit side of the final treatment zone. A rolling mill is disposed, and the direct-fired heating zone is provided with a plurality of heating burners capable of forming a non-equilibrium region in the flame, which contains combustion intermediate reaction products and is free of free oxygen, at least in the exit region. Continuous annealing equipment for steel strips, characterized in that the following are arranged. (3) Cleaning equipment for the steel strip surface from the entry side, preheating area,
A direct heating zone, a soaking zone, a cooling zone mainly using liquid cooling, an intermediate pickling facility, and an overaging treatment zone are provided in this order, and a temper rolling mill is placed on the exit side of the final treatment zone. A steel characterized in that a plurality of heating burners capable of forming a non-equilibrium region in the flame that contains combustion intermediate reaction products and does not contain free oxygen are arranged in the direct-fired heating zone at least in the outlet region. Continuous annealing equipment for strips.