JPH09256070A - Continuous annealing method and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the development of oxide scale and to execute the efficient heating while restraining consumption of fuel by burning the fuel at low excess air ratio in a heating zone of continuously annealing and burning of sucked exhaust gas from a burner in a preheating zone. SOLUTION: A strip material 1 to be heated is passed through a continuous annealing apparatus and preheated during rising the preheating zone 2 and changed in the direction and heated during lowering the heating zone 3 and annealed. In the heating zone 3, the fuel and the air for combustion are supplied to the burner 9a to form combustion flame 13. The fuel is supplied through a flow rate control valve 21 and a change-over value 16, and the air for combustion is supplied through a flow rate control valve 20 and a change-over valve 17, and the fuel is burnt with an excess air ratio. The exhaust gas with an excess fuel in the heating zone is sucked with a suction blower 25 from the burner 9b through the change-over valve 17 and supplied to the preheating zone 2 as the fuel. Further, the exhaust gas from the other burners is sucked totally with the suction blower 25. The exhaust gas from the suction blower 25 is supplied to a burner 8b in the preheating zone 2 through a change-over valve 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous annealing apparatus for continuously annealing a strip-shaped metal material such as a cold-rolled steel strip, which is efficiently heated while suppressing generation of oxide scale. It is about.

[0002]

2. Description of the Related Art Cold rolled steel strips are annealed by continuous annealing equipment. Further, in the continuous galvanizing equipment, the cold rolling steel strip is annealed and galvanized continuously. In these facilities,
The rewound steel strip is sequentially and continuously passed through the pre-heat zone and the heating zone, heated to a predetermined temperature and annealed. In such a continuous annealing device, in order to suppress the generation of oxide scale during heating or to perform non-oxidative annealing, a reducing flame formed by burning fuel at a low air ratio lower than the theoretical air ratio is used. A direct flame reduction heating method is known in which heating is performed by directly spraying the strip. This method is less expensive than the method of passing through a radiant tube furnace in a reducing atmosphere, and in some cases, it is applied to a heating zone.

As an example of the specific conditions, Japanese Patent Publication No. 63-
In Japanese Patent No. 30973, a burner is used to set the air ratio to 1.0 or less in order to apply a combustion gas in a non-equilibrium state containing no unburned oxygen and having intermediate ions in the middle of the reaction, to the steel strip. And the distance between the burner and the burner diameter 0.5 ~ 4
A direct-fire reduction heating method has been proposed in which heating is performed with double adjustment.

As a non-oxidizing preheating and heating means, Japanese Patent Laid-Open No. 3-150320 discloses a plurality of high-temperature reducing gases produced by burning a fuel in a reducing gas generating furnace at a stoichiometric air ratio or less. In the method of spraying and heating a steel strip through an injection nozzle, the distance between the injection nozzle and the steel strip is 50 to 200 mm, and the reducing gas is heated to a temperature of 800 to 160 mm.
A continuous heating method and apparatus at 0 ° C. and a jet flow velocity of 20 to 80 m / s have been proposed.

By the way, when the direct flame reduction heating method is applied to the heating zone or the high temperature reducing gas spraying method as in the above-mentioned Japanese Patent Laid-Open No. 3-150320 is applied, unburned fuel is contained in the exhaust gas of the heating zone. Included, and the annealing temperature of the steel strip is 75
To heat to 0 ° C., a large amount of fuel and preheated air are used, and a large amount of exhaust gas is generated. Therefore, in order to burn the exhaust gas in the pretropical zone, it is necessary to guide the gas in the heating zone to the pretropical zone.

At that time, as a technique for preventing the flame from being disturbed by the exhaust gas in the heating zone and preventing the contact between the reducing flame and the steel strip, Japanese Utility Model Laid-Open No. 2-140964 discloses a vertical type. A vertical open-air heating furnace has been proposed in which the distance between the steel strip pass line and the furnace wall is constant over the entire length of the furnace and the furnace width is increased from the lower part of the furnace to the upper part of the furnace.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the technology of Japanese Patent Laid-Open No. 973 and Japanese Patent Laid-Open No. 3-150320, in order to set the steel strip temperature of the heating zone at a low air ratio to a temperature required for annealing, for example, 750 ° C., a large amount of exhaust gas is generated as described above. To do. When the large amount of exhaust gas is burned in the pretropical zone, the temperature of the steel strip in the pretropical zone becomes too high. In order to suppress the generation of oxide scales in the steel strip, the temperature of the steel strip at the pre-tropical outlet needs to be 500 ° C. or lower, but this temperature may be exceeded. Further, the vertical open-air heating furnace disclosed in Japanese Utility Model Laid-Open No. 2-140964 is inefficient because the furnace body is large.

The present invention is a continuous annealing apparatus for continuously annealing a strip-shaped metal material such as a cold-rolled steel strip to anneal it by direct flame reduction heating to suppress the generation of oxide scale and to reduce the amount of fuel used. It is an object of the present invention to provide an efficient heating method and apparatus that does not disturb the combustion flame without increasing the size of the furnace body.

[0009]

The first invention method of the present invention for achieving the above object is a continuous annealing method in which a belt-shaped material to be heated is annealed by continuously passing it through a preheat zone and a heating zone. The continuous annealing method is characterized in that a heat storage combustion switching type burner is used to burn at a low air ratio in a heating zone, and suction exhaust gas from the burner is burned in a heating zone in a preheating zone.

The second invention method is a continuous annealing method in which a strip-shaped material to be heated is annealed by continuously passing it through the preheat zone and the heating zone. In the heating zone, the heat storage combustion switching type burner is used to burn at a low air ratio. The continuous annealing method is characterized in that high-temperature air is dispersedly supplied to the vicinity of the surface of the material to be heated and burned, and in the pre-tropical zone, the exhaust gas of the burner in the heating zone is burned.

Further, the first invention apparatus of the present invention for achieving the above object is a continuous annealing apparatus for continuously annealing a strip-shaped material to be heated through a preheating zone and a heating zone. A heat storage combustion switching type burner is provided, which has a control system for making combustion by the burner in the heating zone a low air ratio, and a piping system for introducing suction exhaust gas of the burner in the heating zone as pre-tropical fuel. It is a continuous annealing device.

The second invention apparatus is a continuous annealing apparatus in which a belt-shaped material to be heated is annealed by continuously passing it through the pre-heat zone and the heating zone. In the heating zone, a heat storage combustion switching type burner is arranged, and the heating zone is heated. A control system for making the combustion by the burner have a low air ratio, a hot air dispersion supply system having a supply port near the surface of the material to be heated in the heating zone, and the exhaust gas sucked by the burner in the heating zone is introduced as pre-tropical fuel. A continuous annealing apparatus having a piping system.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first invention method will be described with reference to FIGS. 1 and 3. FIG. FIG. 1 is a longitudinal sectional view of a first invention device example as shown in FIG. 3, in which a part of each of the fuel, air and exhaust gas pipes and a control system are drawn. In FIG.
A strip-shaped material to be heated 1 such as a steel strip is continuously passed through a continuous annealing device in a direction of an arrow, preheated while rising in a preheat zone 2, and is turned in a top roll chamber 4 by top rolls 5 and 6, While the heating zone 3 is descending, it is heated to a predetermined temperature and annealed.

The preheat zone 2 and the heating zone 3 of FIG. 3 are provided with heat storage combustion switching type side burners. In this example, the preheat zone 2 has eight pairs of left and right burners 8 in the heating zone 3. Is provided with eight pairs of left and right burners 9, respectively. In this example, the burner 8 in the pretropical zone may be a normal type instead of the heat storage combustion switching type.

In FIG. 1, the pretropical zone 2 and the heating zone 3 are longitudinal sectional views. Although the two are shown separated for convenience, they are actually continuous with the top roll chamber 4 interposed therebetween, and
Indicates the heating zone 3 from the bottom to the top in the pretropical zone 2 as indicated by the arrow.
Then, the plate is continuously passed from the upper side to the lower side. In this example, both the pre-tropical zone 2 and the heating zone 3 employ a heat storage combustion switching type burner, and the burners arranged above and below alternately perform combustion and heat storage to form a combustion flame 13. That is, in the first burner 9 of the pre-tropical zone 2, the left side (9a) stores heat, the right side (9b) burns, the next burner burns on the left side, the right side stores heat, and the final burner 10 of the heating zone 3 left side. (10a) is for combustion, the right side (10b) is for heat storage, and the burner before that is for left side heat storage and right side combustion.

The first invention method is a continuous annealing method in which the pre-heat zone 2 and the heating zone 3 are successively passed through the plate to heat them, and the heating zone 3 is burned at a low air ratio by a regenerative combustion switching type burner 9, In the tropical zone 2, the exhaust gas of the burner 9 in the heating zone 3 is burned. In the example of FIG. 1, fuel and combustion air are supplied to the burner 9 a of the heating zone 3 to form the combustion flame 13. The fuel is supplied via the flow rate adjusting valve 21 and the switching valve 16, and the combustion air is supplied via the flow rate adjusting valve 20 and the switching valve 17 to burn at a low air ratio. Although not shown, fuel and air are also supplied to the other burners of the heating zone 3 in FIG.

Exhaust gas in excess of fuel in the heating zone 3 is
It is sucked from the burner 9b through the switching valve 17 by the suction blower 25 and is supplied to the preheat zone 2 as fuel. Further, the exhaust gas from the other burners is also sucked together by the suction blower 25. In this example, since the heat storage combustion switching type burner is also used in the preheat zone 2, the exhaust gas from the suction blower 25 is supplied as fuel to the burner 8b in the preheat zone 2 via the switching valve 18.

Combustion air is supplied to the burner 8b of the preheat zone 2 through the flow rate adjusting valve 23 and the switching valve 19 for complete combustion. When the amount of heat input is insufficient, fuel is supplied through the flow rate adjusting valve 22. Exhaust gas from the preheat zone 2 is exhausted by being sucked from the burner 8a through the switching valve 19 by the suction blower 26. Although not shown, the other burners in the pre-heat zone 2 are also supplied with fuel and air, and the exhaust gas is sucked and exhausted by the suction blower 26.

During this period, the burners 8a and 9b store heat by the exhaust gas, and the switching valves 16, 17, 1
After switching 8 and 19, the combustion air is preheated by the heat and burned. In addition, heat storage and combustion are alternately performed for the other burners through the same piping system. The switching valves 16, 17, 18, 19 and the flow rate adjusting valves 20, 21, 22, 23 operate according to an instruction from the controller 15.

At this time, in each burner 9 of the heating zone 3, the flow rate adjusting valves 20 and 21 are controlled so that the combustion air becomes insufficient, and combustion is performed at a low air ratio of 0.5 to 0.6. In each of the burners 8 of the preheat zone 2, the flow rate adjusting valve 23 is controlled to completely burn the air at an air ratio of 1.0 to 1.05. When a normal burner is used in the pre-heat zone 2, the switching valves 18 and 19 are not necessary, and fuel is added to the exhaust gas from the suction blower 25 to each burner 9 as needed, and the burner 9 is supplied together with the combustion air to complete supply. To burn.

In the heating zone 3, the amount of suction gas by the heat storage combustion switching type burner 9 is such that the exhaust gas temperature after heat storage by the burner is below the heat resistant temperature of the suction blower 25 and the piping. For example, the furnace temperature of the heating zone 3 is 1300
In the case of ˜1400 ° C., η = (amount of suction gas from the furnace) /
If the (gas amount after combustion reaction of the discharge gas into the furnace) is 1.0, the gas temperature after the heat accumulator becomes 1000 ° C., which exceeds the heat resistant temperature of the suction blower 25 and the pipe.
Let η <1.

A material 1 to be heated such as a steel strip is continuously passed through the preheat zone 2 and the heating zone 3 to be heated to a predetermined temperature and annealed. In Pre-Tropical Zone 2, complete combustion with an air ratio of 1.0 to 1.05 creates an oxidizing atmosphere, but since the material temperature is low, almost no scale is generated. In the heating zone 3, the material temperature finally reaches about 750 ° C. in the case of the ordinary steel strip, but the scale is reduced because of the reducing atmosphere with the air ratio of 0.5 to 0.6. .

Therefore, according to the method of the first aspect of the present invention, it is possible to perform heating while suppressing scale formation. Also, heating zone 3
In the above, since the heat storage combustion switching type burner is adopted, the combustion air is preheated to a high temperature, so that it is possible to burn at a low air ratio of 0.5 to 0.6 without making the fuel supply amount excessive. . Then, the sensible heat of the exhaust gas is stored in the regenerator of the burner 9 in the heating zone to be used for high-temperature preheating of the combustion air, and the exhaust gas having excess fuel is used as the fuel for the preheating zone 2 for efficient combustion. it can. Furthermore, most of the exhaust gas of the heating zone 3 is introduced into the burner 8 of the pre-tropical zone 2 without passing through the inside of the heating zone 3, so that each burner 9 of the heating zone 3 is reduced even if the furnace body does not have a special structure. The sexual flame is not disturbed by the exhaust gas.

Next, the second invention method will be described with reference to the examples of FIGS. FIG. 2 is a longitudinal sectional view of an example of the second invention device as shown in FIG. 4, in which a part of each pipe for fuel, air and exhaust gas and a control system are written. In FIG. 4, a strip-shaped material 1 to be heated, such as a steel strip, is continuously passed through a continuous annealing device in the direction of the arrow, preheated while rising in a preheat zone 2, and is heated in a top roll chamber 4 by top rolls 5 and 6. The direction is changed, and while heating zone 3 is descending, it is heated to a predetermined temperature and annealed.

In this example, the difference from the first invention of FIG. 3 is that the heating zone 3 is provided with a partition wall 7, and the partition wall 7 is provided with a dispersion supply pipe 14. Others are the same as those of the first invention example shown in FIG. Also in the second invention method, the burner 8 of the pre-tropical zone 2 may be a normal type instead of the heat storage combustion switching type.

In FIG. 2, as in FIG. 1, the pre-tropical zone 2 and the heating zone 3 are longitudinal sectional views and are shown separated for convenience, but in reality they are continuous with the top roll chamber 4 interposed therebetween. As shown by the arrow, the material to be heated 1 is continuously threaded from the lower side to the upper side in the pretropical zone 2 and from the upper side to the lower side in the heating zone 3. What is different from the first invention example of FIG.
Supply pipe 14 having a high-temperature air supply port near the surface of the
And a flow rate adjusting valve 24 for supplying high-temperature air to the supply pipe 14 is provided. Others are the first shown in FIG.
This is the same as the invention example.

The second invention method is a continuous annealing method in which the pre-tropical zone 2 and the heating zone 3 are successively passed through and heated, in which the heating zone 3 is burned at a low air ratio by the regenerative combustion switching type burner 9. By the dispersion supply pipe 14, high-temperature air is dispersedly supplied to the vicinity of the surface of the material to be heated 1 and burned, and in the preheat zone 2, the exhaust gas of the burner 9 in the heating zone 3 is burned. In the example of FIGS. 2 and 4, the dispersion supply pipes 14 are provided in nine rows on both left and right sides of the material to be heated 1.

In each burner 9 of the heating zone 3, the controller 15 controls the flow rate adjusting valve 2 so that the combustion air becomes insufficient.
0 and 21 are controlled to burn at a low air ratio of 0.5 to 0.7, and in the vicinity of the surface of the material to be heated 1, hot air supplied from the dispersion supply pipe 14 reduces the air ratio to 0. More than 7 and 0.9. The amount of hot air supplied from the distributed supply pipe 14 is adjusted by the flow rate adjusting valve 24 according to a command from the controller 15.

Also in the second invention method, the material to be heated 1 such as steel material is continuously passed through the preheat zone 2 and the heating zone 3 and annealed at a predetermined temperature, and in the preheat zone 2, the air ratio is 1.0 to 1. .0
The complete combustion of No. 5 produces an oxidizing atmosphere, but since the material temperature is low, almost no scale is generated. In the heating zone 3, the material temperature finally reaches about 750 ° C. in the case of the ordinary steel strip, and on the surface of the material to be heated 1, the air ratio exceeds 0.7 to 0 due to the distributed supply of high temperature air. It becomes the atmosphere of 9. This air ratio is normally oxidative, but active gas having a reducing property is generated in the process of burning unburned fuel by the air supplied in a dispersed manner, so that the scale is reduced without growing.

Therefore, even in the second invention method, it is possible to carry out heating while suppressing scale formation. Also, heating zone 3
Since the heat storage combustion switching type burner is adopted in (1), the combustion air is preheated to a high temperature, so that combustion can be performed at a low air ratio of 0.5 to 0.7 without making the fuel supply amount excessive. Then, the sensible heat of the exhaust gas is stored in the regenerator of the burner 9 in the heating zone to be used for high-temperature preheating of the combustion air, and the exhaust gas having excess fuel is used as the fuel for the pre-heat zone 2.
Efficient combustion can be performed.

Further, most of the exhaust gas from the heating zone 3 is introduced into the burner 8 in the pre-tropical zone 2 without passing through the heating zone 3,
Each burner 9 of the heating zone 3 can be manufactured without specially constructing the furnace body.
The reducing flame of is not disturbed by the exhaust gas. Others are the same as those of the first invention example of FIG.

In the first and second invention methods, in order to create a reducing atmosphere in the furnace of the heating zone 3, the air ratio should be 1.0 depending on the components of the material to be heated 1 and the material temperature. Set a proper value less than. That is, for various materials or elements, the proper range is selected from the relationship diagram between temperature and oxidation rate, the oxidation-reduction region diagram in the combustion gas atmosphere,
It can be determined by experiments, etc. Regarding the latter figure, for example, Gasworme Band 13 Nr.10, Oktober 1964
The literature of P.387-396 shows the oxidation-reduction range of Fe in COG combustion gas with H ₂ O / H ₂ and CO ₂ / CO and temperature as parameters.

Next, as shown in FIGS. 1 and 3, the first invention apparatus is provided with a pre-heat zone 2 and a heating zone 3 in order, and a heat storage combustion switching type burner 9 is disposed in the heating zone 3. It has a control system for making the combustion by the burner 9 a low air ratio, and a piping system for introducing the exhaust gas sucked by the burner 9 as a fuel for the pre-heat zone 2.

In the example of FIG. 1, the control system comprises a controller 15, an air flow rate adjusting valve 20, and a fuel flow rate adjusting valve 21. In the example of FIG. 1, the piping system includes a controller 15, a suction blower 25 that sucks the exhaust gas from the heating zones 3 and 4, and a switching valve 18 that supplies fuel to the burner 8 in the preheat zone 2. The operation of the first invention device is as described in the first invention method.

As shown in FIGS. 2 and 4, the apparatus of the second aspect of the present invention comprises a preheating zone 2 and a heating zone 3 which are installed in that order, and a heat storage combustion switching type burner 9 is arranged in the heating zone 3 and the burner 9 is provided. Control system for making the combustion by 9 a low air ratio, a hot air dispersion supply system having a supply port near the surface of the heated material 1 in the heating zone 3, and a pipe for introducing the exhaust gas sucked by the burner 9 as a fuel for the preheat zone 2. Have a system.

In the example of FIG. 2, the control system comprises a controller 15, an air flow rate adjusting valve 20, and a fuel flow rate adjusting valve 21. In the example of FIG. 2, the piping system includes a controller 15, a suction blower 25 that sucks the exhaust gas from the heating zones 3 and 4, and a switching valve 18 that supplies fuel to the burner 8 in the preheat zone 2.

Further, as the above high temperature air dispersion supply system,
In the example of FIG. 2, the controller 15 and the hot air flow rate adjusting valve 2
4 and the dispersion supply pipe 14. The distributed supply pipes 14 are arranged side by side in the furnace width direction as shown in FIG. Further, as shown in FIG. 4, a partition wall 7 may be provided between the burners 9 and the partition wall 7 may be mounted on the partition wall 7, or may be directly mounted on the furnace wall. The operation of the second invention device is as described in the second invention method.

In the method and apparatus of the invention, the material to be heated 1 may be a steel strip such as ordinary steel, stainless steel or electromagnetic steel, or a strip material such as aluminum or copper. The heating furnace may be a horizontal catenary furnace in addition to the vertical type as shown in FIGS. 3 and 4.

[0039]

【Example】

(1) Inventive Example 1: Using a first inventing apparatus of the present invention as shown in FIGS. 1 and 3, COG (coke oven gas) was used as a fuel to heat a normal steel strip having a plate thickness of 0.8 mm to 750 ° C. Heated and annealed. Air ratio is 1.0 for pre-tropics 2 and heating zone 3
Was set to 0.5 to 0.6. FIG. 5 shows changes in the gas temperature in the furnace and the steel strip temperature. The furnace gas temperature is 140 in heating zone 3.
0 ° C, the temperature of the steel strip is 400 to 500 ° C at the preheater 2 outlet,
The temperature was 750 ° C. near the outlet of the heating zone 3. The exhaust gas temperature at the heat storage outlets of the burners 8 and 9 was about 500 ° C. as shown in FIG.

When the change in the scale thickness of the steel strip is estimated based on the experimental result, it is at a low level in the preheating zone 2 because the temperature of the steel strip is low as shown in FIG. Since the scale is not generated in the place where it does not hit the combustion flame 13 and the scale is reduced in the place where it hits the combustion flame 13, the scale generated in the pre-heat zone 2 is slightly reduced. In addition, in FIG. 5 and FIGS. 6 and 7 below, the plot on the broken line showing the scale thickness is based on the actual measurement value.

(2) Inventive Example 2: Using a second inventive apparatus of the present invention as shown in FIGS. 2 and 4, COG is used as a fuel to heat a 0.8 mm thick ordinary steel steel strip to 750 ° C. Annealed. The air ratio is 1.0 for the pretropical zone 2 and 0 for the heating zone 3.
It was set to 5 to 0.7. Then, in the heating zone 3, high temperature air is supplied from the dispersion supply pipe 14 so that the air ratio on the surface of the steel strip is 0.
It was set to over 7 to 0.9. FIG. 6 shows changes in the gas temperature and the steel strip temperature in the furnace. The gas temperature is 1400 ° C in the heating zone 3, the steel strip temperature is 400 to 500 ° C at the preheater 2 outlet, and the heating zone 3
It was 750 ° C. near the outlet. The exhaust gas temperature at the heat storage outlets of the burners 8 and 9 was about 500 ° C. as shown in FIG.

When the change in the scale thickness of the steel strip was estimated based on the experimental results, it was at a low level in the pre-tropical zone 2 because the temperature of the steel strip was low, as shown in FIG. Then, in the heating zone 3, scale is not generated in a place not hit by the combustion flame 13 of the burner 9, scale is reduced in a place hit by the combustion flame 13, and unburned by the high temperature air supplied from the dispersion supply pipe 14. During the process in which the fuel burns on the surface of the steel strip, a reducing active gas is produced, so that the scale produced in Pretropical Zone 2 almost disappeared.

(3) Conventional Example: A normal side burner that is not of the heat storage combustion switching type, that is, a type of burner that simultaneously supplies fuel and air to the burners on both sides facing each other in FIG. With the adopted continuous annealing device, the same steel strip as in the above-mentioned example of the present invention was heated to 750 ° C and annealed. The air ratio is set to 0.8 to 0.9 in the heating zone 3, and the exhaust gas of the heating zone 3 is introduced from the upper portion (inlet side) of the heating zone 3 to the upper portion (outlet side) of the pre-tropical zone 2 to Then 1.0
Was set to 1.1.

FIG. 7 shows changes in the gas temperature and the steel strip temperature in the furnace.
Shown in The gas temperature in the furnace was 1400 ° C. in the heating zone 3, and a large amount of exhaust gas containing unburned fuel burned in the vicinity of the outlet of the pretropical zone 2, and the temperature became high at 1000 to 1200 ° C. Therefore, the temperature of the steel strip is 500 to 600 ° C at the pre-tropical 2 outlet.
And the temperature at the outlet of heating zone 3 was 750 ° C.

When the change in the scale thickness of the steel strip is estimated based on the experimental result, as shown in FIG.
Since the temperature was high near the outlet, a thicker scale was produced than in the present invention. Then, in the heating zone 3, the scale is reduced at the place where it hits the combustion flame 13 of the burner 9 because it is reducible, but the scale is generated at the place that does not hit the combustion flame 13 because it is oxidative and scale is generated. Has increased.

Each of the above examples was carried out in a pilot line of a continuous galvanizing facility, and after the above annealing, a soaking reduction treatment was carried out at a temperature of 750 ° C. for 30 seconds in a soaking zone in a hydrogen-added atmosphere, followed by immersion in molten zinc. It was plated. Table 1 shows the results of determining the adhesion of the plating by changing the hydrogen concentration in the soaking zone and the fuel consumption ratio. In the column of adhesion of plating, ∘ mark indicates good adhesion on the entire surface, Δ mark indicates that there are few places where no adhesion occurs, and X mark indicates that no adhesion occurs due to the presence of scale.
Further, the fuel consumption ratio is shown as a ratio with the consumption of the conventional example being 1.0.

The example of the present invention has H _{2 of} a soaking zone as compared with the conventional example.
It was proved that the plating adhesion was good even when the concentration was low, and the scale thickness during annealing was thin. Particularly, in Example 2 of the present invention utilizing the generation of reducing active gas, the effect is excellent. Further, in the example of the present invention, the amount of fuel used was small, and efficient annealing could be performed.

[0048]

[Table 1]

[0049]

According to the present invention, in a continuous annealing device for continuously annealing a strip-shaped metal material such as a cold rolled steel strip in a heating zone, since the combustion air is preheated to a high temperature by a heat storage combustion switching type burner, It is possible to burn at a low air ratio of 0.5 to 0.7 without making the fuel supply amount excessive. Therefore, heating and annealing can be performed by direct flame reduction heating that suppresses scale formation, and the sensible heat of the exhaust gas is stored in the regenerator of the burner in the heating zone and used for high-temperature preheating of the combustion air, and the exhaust gas of excess fuel It is possible to carry out efficient combustion by using as a pretropical fuel. In addition, since the exhaust gas from the heating zone is sucked through the heating zone burner and introduced into the pre-tropical zone, efficient combustion is possible without disturbing the reducing combustion flame, even if the furnace body does not have a special structure. You can

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a first method and apparatus of the present invention.

FIG. 2 is an explanatory view showing an example of a second invention method and apparatus of the present invention.

FIG. 3 is a sectional view showing an example of a first invention device of the present invention.

FIG. 4 is a sectional view showing an example of a second invention device of the present invention.

FIG. 5 is a graph showing changes in temperature and scale thickness in an example of the present invention.

FIG. 6 is a graph showing changes in temperature and scale thickness in another example of the present invention.

FIG. 7 is a graph showing changes in temperature and scale thickness in a conventional example.

[Explanation of symbols]

 1 ... Heated material 2 ... Pre-tropical zone 3 ... Heating zone 4 ... Top roll chamber 5, 6 ... Top roll 7 ... Partition wall 8, 9 ... Burner 13 ... Combustion flame 14 ... Dispersion supply pipe 15 ... Controller 16, 17, 18, 19 ... Switching valve 20, 21, 22, 23, 24 ... Flow rate adjusting valve 25, 26 ... Suction blower

Claims (4)

[Claims] 1. A continuous annealing method in which a belt-shaped material to be heated is annealed by continuously passing it through the preheating zone and the heating zone. In the heating zone, a heat storage combustion switching burner is used to burn at a low air ratio, and heating is performed in the preheating zone. A continuous annealing method, which comprises burning the suctioned exhaust gas of the burner in the tropics. 2. A continuous annealing method in which a strip-shaped material to be heated is annealed by continuously passing through the preheating zone and the heating zone, and in the heating zone, the material to be heated is burned at a low air ratio by a regenerative combustion switching type burner. A continuous annealing method, characterized in that hot air is dispersedly supplied to the vicinity of the surface of the burner and burned, and the exhaust gas of the burner in the heating zone is burned in the pre-tropical zone. 3. A continuous annealing apparatus for continuously annealing a strip-shaped material to be heated through a preheat zone and a heating zone, wherein a heat storage combustion switching type burner is arranged in the heating zone, and the burner of the heating zone is used. A continuous annealing device comprising a control system for making combustion a low air ratio and a piping system for introducing exhaust gas of the burner in the heating zone as a pre-tropical fuel. 4. A continuous annealing device for continuously annealing a strip-shaped material to be heated through a preheating zone and a heating zone, wherein a heat storage combustion switching type burner is arranged in the heating zone, and the burner of the heating zone is used. It has a control system that makes combustion a low air ratio, a high temperature air dispersion supply system that has a supply port near the surface of the material to be heated in the heating zone, and a piping system that introduces the exhaust gas from the burner in the heating zone as pre-tropical fuel. A continuous annealing device characterized in that