JP5064251B2 - Dry baking apparatus and dry baking method for painted steel strip - Google Patents

Description

  The present invention relates to a dry baking apparatus and a dry baking method for a coated steel band comprising a hot air heating furnace and an induction heating furnace, which are arranged adjacent to the downstream of an apparatus (for example, a roll coater) for continuously coating the steel band with a water-based paint. It is about.

  The steel strip is coated by continuously applying a water-based paint to the steel strip and then drying and baking it. First, a coating device is formed by coating a steel strip with a water-based paint on an apparatus (for example, a roll coater) that continuously coats the steel strip, followed by a dry baking apparatus comprising a hot air heating furnace and an induction heating furnace adjacent thereto. Thus, the coating film is dried and baked.

  Regarding a drying and baking apparatus comprising a hot air heating furnace and an induction heating furnace, Patent Document 1 discloses that the coating film is primarily dried in a preceding hot air heating furnace and the coating film is finally dried and baked in a subsequent induction heating furnace. A method is disclosed.

  In the function sharing as described in Patent Document 1, since the coating film is finally dried and baked in the induction heating furnace, steam is generated in the induction heating furnace. In the induction heating furnace, an induction heating coil is disposed so as to surround a traveling steel strip. Since the induction heating coil is cooled by the cooling water circulating inside, the water vapor generated in the induction heating furnace condenses on the induction heating coil, and the condensed water droplets eventually drop and adhere to the coated steel strip surface. The quality of the coated steel strip was impaired.

  On the other hand, in Patent Document 2, a coating film made of a water-based paint painted on a steel strip with a roll coater is also dried and baked only in an induction heating furnace, preventing condensation on the induction heating coil, In order to prevent the quality deterioration of the coated steel strip, the outer periphery of the induction coil in the induction heating furnace is surrounded by a shielding plate made of a breathable porous material at least at the part facing the painted steel plate with a required gap. Then, when air of 150 to 250 ° C. is pumped into the gap between the shielding plate and the induction coil, the air is ejected from the breathable porous material, and the coated steel strip is dried and baked by an induction heating furnace, An induction heating type drying baking furnace having a water vapor condensation prevention mechanism that completely shields water vapor generated from a coating film with air is disclosed.

  In a drying baking apparatus including a hot air heating furnace for primary drying of a coating film made of a water-based paint and an induction heating furnace for final drying and baking disclosed in Patent Document 1, Patent Document 2 discloses an induction heating furnace. By adding a water vapor condensation prevention mechanism, it is possible to prevent deterioration of the quality of the coated steel strip, but it requires modification in the induction heating furnace, and the gap between the induction heating coil and the steel strip is made of a breathable porous material. There is a problem that the thickness of the shielding plate is increased and the heating efficiency is lowered.

Japanese Unexamined Patent Publication No. 63-190681 Japanese Patent Publication No. 63-007670

  The present invention relates to a dry-baking apparatus and dry-baking of a coated steel strip, in which a coating film of a steel strip coated with a water-based paint is dried and baked in a hot-air heating furnace and an induction heating furnace that is adjacent to the hot-water heating furnace. In the method, without accompanied by remodeling in the induction heating furnace where the induction heating efficiency is reduced, steam condensation on the induction heating coil of the induction heating furnace can be prevented, and the quality of the coated steel band can be prevented. A dry baking apparatus and a dry baking method are provided.

  The present inventors, in a dry-baking apparatus for a coated steel strip that dries and bakes a steel strip coating coated with a water-based paint continuously in a hot air heating furnace and an induction heating furnace that is adjacent to the hot-water heating furnace, If the coating film made of water-based paint is completely dried in the hot air heating furnace and only baking is performed without generating water vapor from the coating film in the induction heating furnace, water vapor condensation on the induction heating coil can be prevented. However, it was not possible to prevent quality deterioration due to condensation or dripping on the induction heating coil. As a result of diligent investigation and investigation of this cause, it was found that water vapor generated in the hot air heating furnace penetrates into the induction heating furnace along with the steel strip and condenses on the heating coil.

The present invention has been made based on the above findings, and the features of the present invention are as described in the claims.
(1) In a dry-baking device for a coated steel strip that continuously dries and bakes a coating on a steel strip coated with a water-based paint continuously in a hot-air heating furnace and an induction heating furnace that follows it. ,
The hot-air heating furnace can finish the drying of the coating film on the steel strip within the furnace length to finish the evaporation of the coating film moisture, or can also perform primary baking after the drying of the coating film is completed. The induction heating furnace is capable of completing the baking of the coating of the steel strip without residual moisture in the furnace length,
Drying the steel strip end outside coating steel strip, characterized in that a air spouting dipped means spraying the air so as to intersect with the steel strip traveling direction between the induction heating furnace and the hot-air heating furnace Baking device .
(2 ) The dry-baking apparatus for a coated steel strip according to (1) , wherein the air blowing means is an axial fan or a slit nozzle.
( 3 ) In a dry baking method of a coated steel strip, in which a coating film of a steel strip coated with a water-based paint is continuously dried and baked in a hot air heating furnace and an induction heating furnace that is adjacent to the hot steel heating furnace. ,
In the hot air heating furnace, the drying of the coating film on the steel strip is completed within the furnace length to complete the evaporation of the coating film moisture, or the primary baking is also performed after the drying of the coating film is completed. Then, baking of the coating film of the steel strip having no residual moisture within the furnace length is completed, and from the outer side of the steel strip side end portion between the hot air heating furnace and the induction heating furnace, the steel strip crossing direction is intersected. when that sprayed the air as,
The composite vector that combines the velocity vector of the air at the air jet part of the air to be blown and the velocity vector of the steel strip is the value obtained by dividing the steel strip traveling direction component of the composite vector by the steel strip traveling direction component. Injecting the opening width in the steel strip width direction of the heating furnace so as to satisfy the relationship larger than the value obtained by dividing the opening width by the distance between the hot air heating furnace and the induction heating furnace, A method for drying and baking a coated steel strip characterized by preventing penetration into the steel strip .

  According to the present invention, a coating of a steel strip coated with a water-based paint is continuously dried and baked in a hot air heating furnace and an induction heating furnace that is adjacent to the hot steel heating furnace. In the baking apparatus and method, the quality deterioration of the coated steel strip due to water vapor condensation can be effectively prevented without remodeling in the induction heating furnace in which the induction heating efficiency decreases.

  Hereinafter, the present invention will be described with reference to the drawings.

  1, 2, and 3 are a side view, a plan view, and a front view of a dry-baking apparatus for a coated steel strip according to the present invention. The coated steel strip drying and baking apparatus 1 includes a hot air heating furnace 2 having a furnace length L2 and an induction heating furnace 3 having a furnace length L3 which is adjacent to the hot air heating furnace 2 with an interval ΔL. The opening 11 at the steel strip outlet of the hot-air heating furnace 2 has an opening width B2 in the steel strip width direction and an opening height H2 in the steel strip thickness direction, and the opening 12 at the steel strip inlet of the induction heating furnace 3 has a steel strip width. The opening width B3 in the direction and the opening height H3 in the steel strip thickness direction.

  The steel strip 4 continuously coated with a water-based paint by an apparatus (for example, roll coater) (not shown) for continuously coating the steel strip is subsequently fed into the hot air heating furnace 2 continuously. A hot air blowing header 8 is provided in the hot air heating furnace 2, and the hot air blowing header 8 has a plurality of nozzles 7 provided across a pass line of a steel strip 4 coated with a water-based paint, and an air supply duct (not shown) ) From the nozzle 7 to heat the coated steel strip 4.

  The steel strip that has passed through the hot air heating furnace 2 is sent out from the opening 11, and then sent into the induction heating furnace 3 through the opening 12. The induction heating furnace 3 includes an internal water-cooled induction heating coil 6 to heat the coated steel strip 4 passing through the induction heating coil.

In the dry baking apparatus 1 for a coated steel strip comprising a hot air heating furnace and an induction heating furnace, the amount of residual moisture in the coating film can be calculated by computer simulation for each position in the dry baking apparatus. Further, by adjusting the amount of heat input in the hot air heating furnace and the plate passing speed of the steel sheet, it is possible to make the residual moisture in the coating film zero when the steel sheet reaches the outlet of the hot air heating furnace. FIG. 4 shows the distance from the entry side of the hot air heating furnace 2 (the furnace length L2 of the hot air heating furnace 2, the interval ΔL between the hot air heating furnace 2 and the induction heating furnace 3, the furnace length L3 of the induction heating furnace) and the coated steel strip 4 A computer simulation result is shown for the relationship between the temperature of the film (left axis) and the residual moisture content of the coating film on the coated steel strip 4 (right axis). In the example shown in FIG. 4, the drying of the steel strip coating is completed within the furnace length L <b> 2 of the hot-air heating furnace 2, i.e., the coating film drying furnace finishes the evaporation of the coating film moisture. At the entrance, the residual moisture in the coating film is 0 g / m ² , and the induction heating furnace 3 is a coating film baking furnace that completes the baking of the coating film of the steel strip having no residual moisture amount in the furnace length L3. is there.

  In the conventional method, even if the residual component in the coating film is zero at the entrance of the induction heating furnace 3 as described above, it has not been possible to prevent quality deterioration due to condensation or dripping on the induction heating coil. As described above, the steam generated by evaporation from the coating film in the hot-air heating furnace 2 does not stay in the hot-air heating furnace 2, but the steam enters the induction heating furnace along with the steel strip and the heating coil. It was found that there was condensation.

  Therefore, in the present invention, as shown in FIGS. 1 to 3, air is sprayed from the outside of the steel strip side end portion between the hot air heating furnace 2 and the induction heating furnace 3 so as to intersect the steel strip traveling direction 9. Air spraying means 5 is provided, spraying air 10 is sprayed across the steel strip traveling direction 9, and water vapor generated from the coating film in the hot air heating furnace 2 and accompanying the steel strip 4 is generated in the induction heating furnace 3. It is designed not to enter inside. Here, “crossing the steel strip traveling direction 9” means a right angle to the steel strip traveling direction 9 or an angle close to a right angle. Thereby, the water vapor flowing out of the hot air heating furnace 2 along with the steel strip 4 is blown off by the blast air 10 intersecting the steel strip traveling direction 9, and the steel strip side end portion provided with the air blasting means 5 is blown off. It is discharged from the opposite end and does not enter the induction heating furnace.

  In general, the crossing angle between the air blowing direction and the steel strip traveling direction is preferably a right angle as shown in FIG. The angle that swings from a right angle depends on the selection of the distance ΔL between the hot air heating furnace 2 and the induction heating furnace 3, the opening width B3 of the induction heating furnace, the line speed LS of the steel strip, etc. It is preferable that the blast air 10 from the means 5 has an angle in a range that does not enter the interior of each furnace from the opening 11 of the hot air heating furnace 2 and the opening 12 of the induction heating furnace. FIG. 2 (b) shows a situation in which the blast air 10 from the air blasting means 5 does not enter the inside of the furnace through the opening 11 of the hot air heating furnace 2, and FIG. 2 (c) shows the air blasting means 5. This shows a state where the blast air 10 from the inside does not enter the inside of the furnace through the opening 12 of the induction heating furnace 3.

  As described above, from the outside of the steel strip side end between the hot air heating furnace and the induction heating furnace, drying of the coated steel strip of the present invention is provided with air blowing means for spraying air so as to intersect the steel strip traveling direction. In the baking apparatus, it is assumed that the residual moisture in the coating film is zero at the entrance of the induction heating furnace 3. That is, in the dry baking apparatus for the coated steel strip of the present invention, the hot-air heating furnace 2 can finish the drying of the coating film on the steel strip within the length of the furnace and finish the evaporation of the coating film moisture. The induction heating furnace 3 can complete the baking of the coating film of the steel strip having no residual moisture within the length of the furnace. Here, in order to end the evaporation of the coating film moisture in the hot air heating furnace 2, it can be realized by appropriately combining the heat input amount of the hot air heating furnace 2, the furnace length, and the traveling speed (line speed) of the steel strip. Moreover, in order to complete the baking of the coating film in the induction heating furnace 3, it can be realized by appropriately combining the heat input amount of the induction heating furnace 3, the furnace length, and the traveling speed (line speed) of the steel strip. The residual moisture content of the coating film and the steel plate temperature are calculated by computer simulation as shown in FIG. 4, the residual moisture becomes zero at the outlet of the hot air heating furnace 2, and the steel plate temperature is the temperature necessary for baking at the outlet of the induction heating furnace 3. It may be adjusted so that The hot-air heating furnace 2 is a coating film drying primary baking furnace that also performs primary baking after drying the coating film as described above, and the induction heating furnace 3 is used to complete the baking of the steel film coating film without residual moisture. It can also be set as a coating film baking furnace.

  It is preferable to use an axial fan or a slit nozzle as the air blowing means 5 for blowing air so as to intersect the steel strip traveling direction 9. An axial fan is a fan that blows air in the suction axial direction from the axial direction of the fan. The slit nozzle is a nozzle having a long and narrow nozzle opening, long in the traveling direction of the steel strip, and thin in the thickness direction of the steel strip, and ejects air from the slit nozzle. Both the axial flow fan and the slit nozzle are suitable because the straightness of the jetted air is good and the wind does not diffuse relatively.

  As is clear from the above description, in the dry baking method of the coated steel strip of the present invention, the drying of the coating on the steel strip is completed in the furnace length in the hot air heating furnace 2 to evaporate the coating film moisture. Or after the drying of the coating film is completed, primary baking is also performed, and the induction heating furnace 3 completes the baking of the coating film of the steel strip having no residual moisture in the furnace length, and the hot air heating furnace 2 To prevent intrusion of gas accompanying the steel strip into the induction heating furnace 3 by spraying air from the outside of the steel strip side end portion with the induction heating furnace 3 so as to intersect the traveling direction of the steel strip. It is characterized by.

A preferable relationship between the flow velocity V of the blowing air 10 from the air blowing means 5 and the blowing direction will be described with reference to FIG. The vector display is indicated by a subscript ( ^~ ) in this specification, and is indicated by an overline in FIG. Velocity vector V ^~ and jetted put air 10 in the air ejection portion of the air sprayed from the air jetted put means, composite vector VT ^- obtained by combining the line speed vector LS ^- and the steel strip, the composite vector VT strip progression ^- The value obtained by dividing the perpendicular direction component VT _W by the steel strip traveling direction component VT _L is larger than the value obtained by dividing the opening width B3 in the steel strip width direction of the induction heating furnace by the interval ΔL between the hot air heating furnace and the induction heating furnace. And preferred. Thereby, the water vapor | steam which moves at a speed | rate LS accompanying a steel strip can be prevented from being blown away by the blowing air 10 and entering from the opening of the induction heating furnace.

  When the blowing direction of the blowing air 10 is perpendicular to the steel strip traveling direction 9, the required air velocity V (m / s) at the air blowing portion of the air blowing means 5 is as shown in FIG. In addition, the steam that is accompanied by the steel strip 4 traveling at the line speed LS (m / s) and flows at substantially the same speed LS (m / s) as the steel strip 4 is induced to become the steel strip inlet of the induction heating furnace 3. V (m / s) is the wind speed required to drive the outside of the opening width B3 (mm) line in the steel strip width direction of the heating furnace, and V ≧ (LS × B3) / ΔL. Adopt one that meets the requirements.

  As a result, water vapor condensation on the internal water-cooled induction heating coil of the induction heating furnace 3 is prevented, and deterioration of the quality of the coated steel strip can be prevented. In the example shown in FIG. 1, the axial center height of the axial fan that is the air blowing means 5 is provided in accordance with the traveling height of the steel strip, and the upper and lower surfaces of the steel strip are introduced into the induction heating furnace with steam accompanied. Intrusion of water vapor is prevented by one axial fan, but a pair of axial fans are provided above and below the running height of the steel strip, and the water vapor intrudes into the induction heating furnace with steam accompanying the upper and lower surfaces of the steel strip, respectively. Can also be prevented.

  Note that, as described above, the steam generated from the coating film in the hot-air heating furnace 2 provided between the hot-air heating furnace 2 and the induction heating furnace 3 is prevented from entering the induction heating furnace 3 along with the steel strip 4. As a means, instead of an axial fan, a slit nozzle is provided, air is blown across the steel strip traveling direction 9, steam generated from the coating film in the hot air heating furnace 2, and water vapor accompanying the steel strip 4 is generated. , It can be prevented from entering the induction heating furnace 3.

  Further, the opening width B2 in the steel strip width direction of the opening 11 serving as the steel strip outlet of the hot air heating furnace 2, the opening height H2 in the steel strip thickness direction, and the steel strip of the opening 12 serving as the steel strip inlet of the induction heating furnace 3 It is preferable to make the opening width B3 in the width direction and the opening height H3 in the steel strip thickness direction as small as possible within a range that does not hinder the steel strip passing plate.

  The present invention was applied to a dry baking apparatus 1 for a coated steel strip composed of a hot air heating furnace 2 and an induction heating furnace 3 shown in FIGS. The steel strip 4 continuously coated with a water-based paint by a roll coater (not shown) is continuously fed into the hot air heating furnace 2, and the steel strip 4 that has passed through the hot air heating furnace 2 is subsequently fed into the induction heating furnace 3. .

  The length L2 of the hot air heating furnace 2 is 6.1 m, the length L3 of the induction heating furnace 3 is 4.8 m, the distance ΔL between the hot air heating furnace 2 and the induction heating furnace 3 is 450 mm, and the steel strip of the hot air heating furnace 2 The opening width B2 in the steel strip width direction of the opening 11 serving as the outlet is 2 m, the opening height H2 in the steel strip thickness direction is 200 mm, and the opening width B3 in the steel strip width direction of the opening 12 serving as the steel strip inlet of the induction heating furnace 3 Is a dry baking apparatus 1 for a coated steel strip having an opening height H3 in the thickness direction of 250 mm.

The steel strip 4 has a plate thickness of 0.8 mm, a plate width of 1200 mm, and travels at a line speed of 200 mpm (3.3 m / sec). A water-based paint is applied to the surface of the steel strip at 14.3 g / m ² (per one side), and is dried and baked by the dry baking apparatus 1.

As shown in FIG. 4, the amount of heat input to the hot air heating furnace 2 was determined so that the drying of the coating film on the steel strip was completed within the furnace length L2 of the hot air heating furnace 2 and the evaporation of the coating film moisture was completed. At the same time, the heat input amount of the induction heating furnace 3 was determined so as to complete the baking of the coating film of the steel strip having a residual water content of 0 g / m ² in the furnace length L3 of the induction heating furnace 3. A computer simulation was performed, and it was confirmed that the amount of residual moisture was zero at the outlet of the hot air heating furnace 2 and that the steel strip temperature was a temperature at which baking was completed at the outlet of the induction heating furnace.

  First, as a conventional example, when the coated steel strip was dried and baked without using air spraying means, water vapor was condensed and condensed on the induction heating coil of the internal water cooling system of the induction heating furnace, and the coating was performed by dripping onto the steel strip. Degradation of steel strip quality (spotted pattern) occurred. In the hot air heating furnace 2 as shown in FIG. 4, the drying of the steel strip coating is completed in the furnace length L2, the evaporation of the coating film moisture is completed, and the induction heating furnace 3 is set in the furnace length L3. Only with the function sharing of the coating film baking furnace that completes the baking of the coating film on the steel strip with a residual moisture content of 0 g / m2, quality deterioration of the coated steel strip due to dripping onto the steel strip can be prevented. There wasn't.

  Next, in the example of the present invention, an axial fan was adopted as the air blasting means 5 and air was sprayed at a wind speed of 14.8 m / sec perpendicular to the steel strip traveling direction 9 to dry-bak the coated steel strip. However, there was no deterioration in the quality of the steel strip due to water vapor condensation, agglomeration, or dripping onto the steel strip of the internal water-cooling induction heating coil of the induction heating furnace 3.

  The present invention relates to dry baking of a coated steel strip that can effectively prevent deterioration of the quality of the coated steel strip due to water vapor condensation when continuously coating and drying a steel strip coated with various water-based paints. It can be used as an apparatus and dry baking method.

It is a side view of the dry baking apparatus of the coated steel strip of this invention. It is a top view of the dry-baking apparatus of the coated steel strip of this invention, (a) is a figure which shows the case where a blasting air is made into right angle to the steel strip advancing direction, and (b) and (C) are a little inclined from a right angle It is. It is a front view of the drying baking apparatus of the coated steel strip of this invention. It is explanatory drawing of the dry-baking function share of the hot-air heating furnace of the dry-baking apparatus of the coated steel strip of this invention, and an induction heating furnace. It is explanatory drawing of the required wind speed of an air blasting means, (a) is a figure which shows the case where (a) is general and (b) makes the air blasting direction a right angle to the steel strip advancing direction.

Explanation of symbols

1: Dry baking apparatus for coated steel strip 2: Hot air heating furnace 3: Induction heating furnace 4: Painted steel strip 5: Air blowing means L2: Furnace length L3 of hot air heating furnace 2: Furnace length ΔL of induction heating furnace 3: Spacing B2 between the hot air heating furnace 2 and the induction heating furnace 3: Opening width in the steel strip width direction of the opening serving as the steel strip outlet of the hot air heating furnace 2: Steel strip width of the opening serving as the steel strip inlet of the induction heating furnace 3 Opening width H2 in the direction: opening height in the steel strip thickness direction of the opening serving as the steel strip outlet of the hot-air heating furnace 2 H3: opening height in the steel strip thickness direction of the opening serving as the steel strip inlet of the induction heating furnace 6 6: Internal water-cooled induction heating coil 7: Nozzle 8: Hot air blowing header having nozzle 7 9: Steel strip traveling direction 10: Blowing air 11: Opening 12: Opening

Claims (3)

In the dry-baking equipment of the coated steel strip, which continuously dries and bakes the coating on the steel strip coated with water-based paint continuously in the hot air heating furnace and the induction heating furnace that follows it.
The hot-air heating furnace can finish the drying of the coating film on the steel strip within the furnace length to finish the evaporation of the coating film moisture, or can also perform primary baking after the drying of the coating film is completed. The induction heating furnace is capable of completing the baking of the coating of the steel strip without residual moisture in the furnace length,
Drying the steel strip end outside coating steel strip, characterized in that a air spouting dipped means spraying the air so as to intersect with the steel strip traveling direction between the induction heating furnace and the hot-air heating furnace Baking device. The dry-baking device for a coated steel strip according to claim 1 , wherein the air spraying means is an axial fan or a slit nozzle. In the dry-baking method of the coated steel strip, the coating film of the steel strip coated with a water-based paint continuously is dried and baked continuously in a hot air heating furnace and an induction heating furnace that is adjacent thereto.
In the hot air heating furnace, the drying of the coating film on the steel strip is completed within the furnace length to complete the evaporation of the coating film moisture, or the primary baking is also performed after the drying of the coating film is completed. Then, baking of the coating film of the steel strip having no residual moisture within the furnace length is completed, and from the outer side of the steel strip side end portion between the hot air heating furnace and the induction heating furnace, the steel strip crossing direction is intersected. when that sprayed the air as,
The composite vector that combines the velocity vector of the air at the air jet part of the air to be blown and the velocity vector of the steel strip is the value obtained by dividing the steel strip traveling direction component of the composite vector by the steel strip traveling direction component. Injecting the opening width in the steel strip width direction of the heating furnace so as to satisfy the relationship larger than the value obtained by dividing the opening width by the distance between the hot air heating furnace and the induction heating furnace, A method for drying and baking a coated steel strip characterized by preventing penetration into the steel strip.

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