KR20140081258A - Method for coating a metal tube with enamel and Equipment for carrying out the method - Google Patents

Abstract

The present invention relates to a method for coating a metal tube with enamel and an enamel coating apparatus used for the same. The a method for coating a metal tube with enamel includes the steps of: (a) pre-treating the surface of the metal tube after feeding the metal tube, which is rotated by an in-feed conveyer and proceeds, into a pretreatment chamber; (b) coating the surface of the metal tube with a enamel glazing solution, supplied from a supplying nozzle of the enamel glazing solution; and (c) firing the metal tube at 750-1000°C after feeding the metal tube, coated in the step (c), into a firing chamber. In the step of (c), the firing chamber includes a firing chamber conveyor including two or more rollers in the shape of an hourglass. The firing chamber conveyor supports a lower side of the metal tube, heated by the rollers in the shape of an hour glass, and performs a process of transferring the metal tube to an output conveyor.

Description

(4) Method for coating a metal tube with enamel and equipment for carrying out the method

The present invention relates to an enamel coating method for metal tubes and an enamel coating apparatus used therefor. In particular, the present invention relates to an enamel coating method and a enamel coating apparatus for a fin tube in which heat conductive fins are formed on the surface of a metal tube.

 Because metal tubes are often used in humid environments, various types of coatings are applied to the surface to improve durability. One of the enamel coatings is characterized by high heat resistance and acid resistance. However, since the coating process is required to be performed at a high temperature (750 to 1000 ° C), it is not widely used.

In particular, since a high-temperature firing process is required, it is difficult to provide a large-scale firing chamber in order to coat an object coated with an enamel glaze with a long length or a bulky size. Therefore, enamel coating on a long or bulky coated object is regarded as a near impossible task.

However, when heat exchange is performed in a harsh environment (such as a fin tube used as a generator heat exchanger for a generator), the gas is cooled while the gas is cooled, and the tube surface and the heat transfer fins are exposed to the acid dew point, Is inconvenient because it is required to periodically replace the corroded metal tube when it is coated with a general coating composition, resulting in a large cost. In order to solve this problem, a metal tube having a stainless steel or titanium material is used, but the cost is high and the replacement period of the fin tube is increased, which is not a fundamental solution to acid corrosion. Teflon coating is also applied to the fin tube. Teflon material has a problem in terms of heat resistance. Therefore, it may be desirable to apply enamel coatings to metal tubes used in harsh environments, such as environments where heat resistance and acid resistance are required.

For reasons that it is difficult to coat the surface of the metal tube with enamel,

First, as mentioned above, there is a reason why a high-temperature plasticizing chamber is required. In particular, when the length of the metal tube is long, since a high-temperature plasticizing chamber having a large size is required, it is more difficult.

Second, there is a fear that the shape of the metal tube may warp or twist during coating while being subjected to a high-temperature sintering process. At this time, the longer the length of the metal tube, the higher the frequency of occurrence of such a problem. Therefore, a method of preventing the deformation of such a metal tube when coating the metal tube needs to be devised.

Third, the oil components on the surface of the metal tube in the pretreatment process must be removed before the enamel coating because it interferes with the bonding of the enamel glaze to the surface of the metal tube. However, it can be said that the conventional pretreatment methods are difficult to efficiently remove the oil flow components.

That is, the blast process during the pretreatment process is not effective in removing the oil flow components, and when the wet process is introduced, the pretreatment becomes complicated and the coating efficiency is lowered. Therefore, there is a need to develop a method for removing the oil flow components that are buried on the surface of the metal tube by a simple method.

Fourth, it is not easy to remove bubbles formed in the coating film after coating the enamel glaze. Removing the bubbles formed in the coating film is very important in the coating process as it affects the quality of the coating. Particularly, it is difficult to remove air bubbles formed on the surface of the tube and the surface of the heat transfer fin, in which a plurality of heat transfer fins are formed on the surface of the metal tube. The air bubbles must be removed to improve the durability A fin tube can be manufactured. Conventionally, a method of removing air bubbles by tapping a metal tube has been used, but it is difficult and less effective to use such a method when a long metal tube is coated.

Therefore, in order to utilize the excellent physical properties of the enamel coating by applying the enamel coating to the metal tube, it is necessary to solve the above-mentioned problems.

According to the present invention,

And an object of the present invention is to provide an enamel coating method and an enamel coating apparatus which can prevent warpage or warping of a metal tube having a long length in a high temperature firing process.

It is another object of the present invention to provide an enamel coating method and an enamel coating apparatus which can simplify a coating process of a metal tube and simplify facilities.

According to the present invention,

(a) pre-treating a surface of a metal tube by feeding a metal tube advancing and rotating by an in-feed conveyor into a pretreatment chamber;

(b) coating the surface of the metal tube with an enamel glaze supplied from an enamel glaze supply nozzle installed inside the coating chamber by feeding the metal tube, which has been pretreated in the step, into a coating chamber; And

(c) firing the coated metal tube into the firing chamber and firing at 750 to 1000 ° C in the step (a);

In the step (c), the firing chamber includes a firing chamber conveyor including two or more elongated rollers, and the firing chamber conveyor conveys the metal tube heated by the elongated roller to the output conveyor while supporting the metal tube downward And a method of coating an enamel of a metal tube.

Further, according to the present invention,

A pretreatment chamber for pretreating the surface of the metal tube to be fed while rotating from an in-feed conveyor; A coating chamber for coating the surface of the metal tube with an enamel glaze supplied from an enamel glaze supply nozzle installed therein when the pre-processed metal tube is fed; And a firing chamber for performing firing at a temperature of 750 to 1000 ° C when the coated metal tube is fed,

Wherein the firing chamber is provided with a firing chamber conveyor for conveying the heated metal tube to an output conveyor while supporting the fired metal tube, and the firing chamber conveyor includes two or more elongated rollers. to provide.

According to the enamel coating method of the present invention,

It is possible to provide an enamel coated metal tube having excellent quality because bending or twisting that often occurs in a metal tube having a long length is prevented in a high temperature firing process.

Unlike the conventional method in which the rear end portion of the metal tube is connected to another metal tube before being fed into the pretreatment chamber by using the firing chamber conveyor and firing is performed in this state, the firing process is performed without connecting the metal tubes to each other The coating process is simplified and the production efficiency of the enamel coated metal tube is improved.

In addition, in the case of using the elongated roller instead of the pair of rotating rollers, the facility of the coating apparatus can be simplified.

1 is an illustration of an enamel coating apparatus used in the enamel coating method of the present invention.
Fig. 2 shows a configuration (b) of a motor and a roller included in an in-feed conveyor (a) and an in-feed conveyor among enamel coating apparatuses used in the enamel coating method of the present invention. It is.
FIG. 3 is a simplified view of the coating section of the enamel coating apparatus used in the enamel coating method of the present invention.
Fig. 4 schematically shows the structure of an induction heater used in the enamel coating method of the present invention.
5 is a photograph of a manufacturing process of an induction heater used in the enamel coating method of the present invention.
6 is a photograph of a metal tube heated by an induction heater used in the enamel coating method of the present invention.
7 is a schematic view of a coating chamber (a general tube coating) included in a coating portion of an enamel coating apparatus used in the enamel coating method of the present invention.
FIG. 8 is a schematic view of a coating chamber (fin tube coating) included in the coating portion of the enamel coating apparatus used in the enamel coating method of the present invention.
9 schematically shows the air injection direction of the air injection nozzle used in the enamel coating method of the present invention.
10 is a photograph of a fin tube coated by the enamel coating method of the present invention.
11 schematically shows an enamel coating apparatus employing an elongated roller used in the enamel coating method of the present invention.
12 schematically shows a pretreatment chamber conveyor 400, a coating chamber conveyor 500, and a firing chamber conveyor 600 among the enamel coating apparatuses used in the enamel coating method of the present invention.
13 is a perspective view showing an elongated roller used in the enamel coating apparatus of the present invention.
14 is a perspective view showing an elongated roller having a passage 271 for circulating cooling solvent used in the enamel coating apparatus of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would unnecessarily obscure the gist of the present invention.

The enamel coating method of the present invention, as shown in Figs. 1 to 14,

(a) pre-treating the surface of the metal tube 10 by feeding the metal tube 10 advancing and rotating by the in-feed conveyor 200 to the pretreatment chamber 110;

(b) In the above step, the pre-treated metal tube 10 is fed into the coating chamber 120, and the surface of the metal tube 10 is coated with the enamel glaze supplied from the enamel glaze supply nozzle 121 installed in the coating chamber. Coating; And

(c) firing the coated metal tube (10) to the firing chamber (130) and firing the metal tube at 750 to 1000 ° C in the step (a);

In the step (c), the firing chamber 130 includes a firing chamber conveyor 600 including two or more elongated rollers 270, and the firing chamber conveyor 600 is provided with the long roller 270 To the output conveyor (300) while supporting the metal tube (10) heated by the metal tube (10).

In the enamel coating method of the present invention, the elongated rollers 270 form an angle of 5 ° to 35 ° in a clockwise or counterclockwise direction with respect to a transverse line perpendicular to the longitudinal direction of the firing chamber conveyor 600 In this case, the firing chamber conveyor 600 rotates and advances the metal tube heated by the elongated roller 270 while supporting the metal tube downward, and transfers the metal tube to the output conveyor 300 Can be performed.

The enamel coating method of the present invention is characterized in that the firing chamber 130 has a firing chamber conveyor 600 including two or more elongated rollers 270 as shown in Fig. 12, and the firing chamber conveyor 600 The metal tube 10 is conveyed to the output conveyor 300 while supporting the metal tube 10 heated by the elongated roller 270 downward.

That is, in the step (c), the firing process of the metal tube is performed at a high temperature of 750 to 1000 ° C. Therefore, if the metal tubes 10 are connected to each other and the front end and the rear end of the metal tube are not supported to each other, bending or distortion may occur in a portion that is not supported while passing through the firing chamber 130. Therefore, in the related art, the pretreatment process, the coating process, and the sintering process have been performed by connecting the rear end of the metal tube 10 to the other metal tube 10 before being fed into the pretreatment chamber 110.

However, when the rear end of the metal tube 10 is connected to the distal end of the other metal tube 10 as described above, there is a disadvantage that a work force capable of processing the end is required. Further, even when the metal tubes are connected to each other and are supported by each other as described above, when heated by the high temperature (750 to 1000 ° C) in the firing chamber 130, the metal tube is often bent or twisted. Accordingly, the present invention has been made to solve such a problem.

The enamel coating method of the present invention can be applied to a high temperature metal tube 10 passing through a firing chamber 130 in order to more completely prevent bending and twisting of the metal tube 10 in a firing process, And a conveying chamber 600 for supporting and moving the metal tube 10 so that the metal tube 10 can be prevented from being deformed.

12, the firing chamber conveyor 600 is rotated in a clockwise or counterclockwise direction by 5 to 35 degrees with respect to a transverse line perpendicular to the longitudinal direction of the firing chamber conveyor 600, And may include two or more elongated rollers 270 mounted on a shaft forming an angle of 10 [deg.] To 30 [deg.].

As shown in Figs. 13 and 14, the elongated rollers 270 have a shape similar to that of the elongated rollers 270, and the elongated rollers 270 can be rotated in a clockwise or counterclockwise direction with respect to a transverse line perpendicular to the longitudinal direction of the conveyor. A function of rotating and advancing the metal tube 10 placed on the roller when it is rotated by the power supplied directly or indirectly is provided on the axis which forms an angle of 5 ° to 30 ° in the clockwise direction . In this case, the angle of rotation of the shaft of the elongated roller 270 serves to determine the rotation speed of the metal tube 30. In the enamel coating method of the present invention, the rotating speed of the metal tube is preferably 2 to 10 times, preferably 5 to 9 times per minute, and the angle of rotation of the elongated roller 270 axis can be adjusted have.

The configuration of the conveyor other than the elongated roller 270 in the firing chamber conveyor 600 may be a configuration conventionally used in this field. The transmission of power to the elongated rollers 270 can be accomplished by a method commonly used in the art.

The long roller 270 may be made of any material as long as it can withstand high temperatures (750 to 1000 ° C), and may be preferably made of a metal material.

As described above, when the firing chamber conveyor 600 is provided in the firing chamber 130, the metal tubes do not warp or warp during the firing process even when they are not connected to each other, The same effect can be achieved even when the connecting members 10 are connected to each other.

The connection of the metal tubes 10 may be performed automatically or manually using various connecting members known in the art.

Since the firing process of the metal tube 10 is performed at a high temperature, the firing chamber conveyor 600 provided in the firing chamber 130 should have excellent heat resistance. In particular, in the case of the elongated roller 270, heat resistance is required since the metal roller is directly contacted with the metal tube heated at a high temperature. However, since materials having heat resistance capable of withstanding 750 to 1000 占 폚 are not common and expensive, the enamel coating method of the present invention has developed a method of cooling the elongated rollers 270 with a cooling solvent.

That is, in the enamel coating method of the present invention, the elongated roller 270 included in the conveyor 600 for the firing chamber may have a cooling solution circulation passage 271 passing through the rotation shaft as illustrated in FIG. When the cooling solution such as cooling water is circulated through the cooling solution circulation passage 271 provided as described above, the elongated roller 270 functions even at the firing temperature (750 to 1000 ° C) of the metal tube 10 The problem does not occur.

In the enamel coating method of the present invention, the continuous rotation and advancement of the metal tube 10 may be accomplished by using an in-feed conveyor 200 and / or out -feed) may be formed by a motor 220 installed in the conveyor 300 and a plurality of pairs of rotating rollers 230 receiving a power from the motor and forming a corner angle so that the metal tube can be rotated while being rotated.

11 and 12, a motor (not shown) installed in an in-feed conveyor 200 and / or an out-feed conveyor 300 and a motor And an elongated roller 270 capable of advancing while rotating the metal tube.

As shown in FIGS. 11 and 12, the elongated rollers 270 rotate in a clockwise or counterclockwise direction with respect to the transverse direction at right angles to the longitudinal direction of the conveyor by 5 ° to 35 °, more preferably 10 ° Lt; RTI ID = 0.0 > 30 degrees. ≪ / RTI > As shown in Figs. 13 and 14, the elongated rollers 270 have a shape similar to that of the elongated rollers 270, and the elongated rollers 270 can be rotated in a clockwise or counterclockwise direction with respect to a transverse line perpendicular to the longitudinal direction of the conveyor. A function of rotating and advancing the metal tube 10 placed on the roller when it is rotated by the power supplied directly or indirectly is provided on the axis which forms an angle of 5 ° to 30 ° in the clockwise direction . In this case, the angle of rotation of the shaft of the elongated roller 270 serves to determine the rotation speed of the metal tube 30.

When the above-described elongated roller 270 is used in a conveyor, the roller is simplified, thereby simplifying the entire apparatus.

In the enamel coating method of the present invention, the rotation speed of the metal tube is preferably 2 to 10 times, preferably 5 to 9 times per minute, and the rotation speed of the metal tube is controlled by the rotation roller , Or by adjusting the angle of rotation of the shaft of the elongated roller (Figs. 11 and 270).

In the enamel coating method of the present invention, an in-feed conveyor 200 and an out-feed conveyor 300 are used as shown in FIGS. 1 and 2, and a metal tube 10 When a pretreatment process, a coating process, and a sintering process are performed by connecting the rear end portion to another metal tube 10 before being fed into the pretreatment chamber 110, a separate pretreatment chamber conveyor 400 and a coating chamber conveyor 500 are required I can not. That is, as in the present invention, the coating portion 100 including the pretreatment chamber 110, the coating chamber 120, and the firing chamber 130 is compact so that its length is very short compared to the length of the metal tube to be coated An in-feed conveyor 200 and an out-feed conveyor 300 provided before and after the pretreatment chamber 110 and the coating chamber 120 without using a separate conveyor, The continuous rotation and advancement of the metal tube 10 can be performed.

The metal tube 10 is connected to the other metal tube 10 before the metal tube 10 is fed to the pretreatment chamber 110 so that the metal tube 10 can be separately A coating chamber conveyor 500 and a conveyor 600 for the firing chamber in order to allow the individual metal tubes 10 to rotate and advance in the pre-treatment process, the coating process, and the firing process, May be required.

The pretreatment process of the metal tube in the step (a) may be performed by a method commonly used in the art, such as shot blast, sand blast, or grit blast.

It is also possible to pre-treat the metal tube by a wet pretreatment commonly used in the pretreatment of a metal, or to generate ultrasonic waves in the pretreatment solution during wet pretreatment to remove foreign substances on the surface of the metal tube more efficiently Do.

However, the oil flow components are not easily removed by the blast process, and when the wet process is introduced, the equipment is increased and the pretreatment process becomes complicated and the coating efficiency is lowered.

Therefore, in the enamel coating method of the present invention, the heating means 111 is introduced into the pretreatment chamber 110 to heat the metal tube 10 to a high temperature, so that oil components buried on the surface are burned and removed in a short time .

The high-temperature heating process may be performed by heating means 111 which is commonly used. That is, examples of the heating means include an electric furnace, a plasma heat treatment furnace, a heavy oil furnace, a light oil furnace, a gas furnace, a hydrogen annealing furnace, and an induction heating furnace.

In the enamel coating method of the present invention, in particular, the induction heater 111 may be preferably used as the induction heating furnace as illustrated in Figs. Among the induction heaters, a high-frequency induction heater using a high-frequency current can be preferably used.

In the enamel coating method of the present invention, since the metal tube 10 is infiltrated while rotating, the shape of the induction heater 111 is not a problem. That is, since the metal tube 10 can be heated evenly regardless of the shape of the induction heater 111, all shapes known in the art can be used.

As shown in FIGS. 3 to 5, the induction heater 111 may be a cylindrical or arcuate induction heater (not shown) having a radius of curvature of 5 mm to 150 mm larger than the outer diameter of the metal tube 10 111) can be preferably used. The induction heater may be provided in the moving direction of the metal tube 10 such that the outer surface of the moving molten metal tube 10 and the inner curved surface of the cylindrical shape maintain a constant distance.

The high-temperature heat treatment in the pre-treatment step is preferably performed at a temperature of 300 to 600 ° C, more preferably 400 to 500 ° C for 10 seconds to 4 minutes, and further preferably 10 seconds to 2 minutes.

If the high-temperature heat treatment is carried out at a temperature lower than 300 캜, it takes a long time to remove oil components, and when the heat treatment is performed at a temperature higher than 500 캜, economical efficiency is lowered. If it is less than 10 seconds, it is difficult to reach the required high temperature, and if it takes more than 5 minutes, the productivity may be lowered.

When the high temperature heat treatment is performed using the induction heater 111, it is possible to heat the metal tube 10 at the heat treatment temperature (300 to 600 ° C.) within approximately one minute, so that the pretreatment chamber 110 can be made compact And the cost of the preprocessing can be greatly reduced.

In addition, the induction heater 111 has a feature of being energy efficient because it is easy to make the induction heater 111 small in size to fit the metal tube 10 having a small diameter as compared with the conventional heating means, and is heated at a close distance.

4, the induction heater 111 may include a heating coil 112 forming a shape of a circular tunnel and an alternating-current power supply (FIG. 5, 114) supplying current to the heating coil. In addition, an insulating cover 113 may be optionally provided on the outer surface of the heating coil 112.

As shown in FIG. 4, if a metal tube 10 is inserted into a circular tunnel formed by the heating coil 112 and an alternating current is supplied, an electrical resistance due to an eddy current occurs on the surface of the metal tube, Heat is generated on the surface.

Fig. 5 is an image of the manufacturing process of the induction heater 111. Fig. As shown in FIG. 5, the induction heater 111 is configured in such a manner that the heating coil 112 is formed in a circular tunnel shape to supply the AC power source 114.

FIG. 6 is a photograph of the state of the metal tube 10 heated by the induction heater 111 manufactured in FIG. From FIG. 6, it can be seen that the entire tube is heated in red.

5 and 6, the surface temperature of the metal tube 10 reached 400 DEG C after 18 seconds from the start of heating and reached 680 DEG C in 56 seconds. Therefore, according to the induction heater 111, the high temperature pre-treatment of the metal tube 10 can be completed within about one minute.

7 to 8, in the coating process of the metal tube in the step (b), the metal tube 10, which rotates and advances, is fed to the coating chamber 120 and is supplied to the enamel glaze supply nozzle The surface of the metal tube 10 is coated with the enamel glaze supplied from the metal tube 121; The coating brush 122 provided behind the enamel glaze supply nozzle 121 is brought into contact with the surface of the advancing metal tube to remove the excess enamel glaze coated on the surface of the metal tube 10 And at the same time removing bubbles formed inside the coating film.

In addition, the air injector 123 is provided behind the enamel glaze supply nozzle 121, and the surface of the metal tube that advances while rotating is 0.05 m / s to 3 m / s, more preferably 0.1 m / s to 1.5 m / s to remove the excess enamel glaze applied to the surface of the metal tube 10 and to remove bubbles formed inside the coating film.

If the air jetting speed is less than 0.05 m / s, the effect of air injection is difficult to be expected. If the air jetting speed is more than 3 m / s, the applied enamel glaze may be removed more than necessary.

When the air injection process is performed by the enamel glaze supply nozzle 121 as described above, extra enamel glaze can be easily removed from the surface of the metal tube, bubbles formed in the coating film can be efficiently removed In addition, by drying the enamel glaze applied to the surface of the metal tube in the previous stage of firing, it is possible to prevent the enamel glaze from hardening due to falling in the gravitational direction during the firing process to form a non-smooth coating surface.

In addition, it is possible to efficiently remove the bubbles formed on the surface of the metal tube during the coating process of the enamel glaze, thereby forming a uniform and firm coating film. Particularly, it is possible to very easily remove bubbles which are formed in corners when coating a metal tube (for example, a metal fin tube) on which rough irregularities are formed on the surface, which is difficult to remove by conventional methods.

The air injected from the air injection nozzle 123 may be more preferably in the case of hot air at 30 to 200 ° C. As described above, when hot air is sprayed, it is possible to obtain a better effect in removing air bubbles, and it is also possible to provide a better effect in drying the coated enamel glaze before the metal tube 10 enters the firing chamber 13 have.

In addition, the air injection nozzle 123 may be installed at a rear portion of the coating brush 122 disposed behind the enamel glaze supply nozzle 121. In this case, the enamel glaze is uniformly applied to the surface of the metal tube, and the bubble removal can be made more completely.

7, the enamel glaze supply nozzle 121 may be installed in a necessary number along the direction of the coating tube in the upward direction of the coating tube 10 to be fed. However, this is only one embodiment, and the enamel glaze supply nozzle 121 can be freely installed in various places in various places. When enamel glaze is supplied or discharged from the enamel glaze supply nozzle 121 installed as described above, enamel glaze is uniformly applied to the metal tube 11 which advances while rotating.

The coating brush 122 may be installed at a position rearward of the enamel glaze supply nozzle 121 with respect to the traveling direction of the metal tube 10 and may be provided with an extra enamel glaze applied to the metal tube 10 Any type of brush can be applied as long as the bubbles formed inside the coating film can be removed at the same time. If the metal tube 10 is the fin tube 10 having the heat conductive fins 12 formed on the surface of the tube, the bristles may be coated with the staple fibers constituting the brush so that the enamel glaze can be uniformly coated at every corner of the heat conductive fins It shall have appropriate strength and thickness.

The air injection nozzle 123 is installed at a position behind the enamel glaze supply nozzle 121 with respect to the traveling direction of the metal tube 10 and is not restricted by the extra enamel glaze It is possible to apply any type of nozzle as long as it can remove bubbles formed inside the coating film while removing the bubbles.

9, it is preferable that the air injection nozzle 123 injects air in a direction opposite to the rotating direction of the metal tube 10, and the air to be sprayed is sprayed to the lowermost end of the metal tube 10 It is preferable to be installed so as to be able to be reached.

As described above, when the injected air is allowed to reach the lowermost end of the advancing metal tube 10, the excess enamel glaze applied to the surface of the metal tube can easily reach the lower end of the tube And can be easily removed and easily removed by the action of gravity. Also, in the case of spraying the air in the direction opposite to the rotating direction of the metal tube 10, it is preferable that the above-mentioned object can be achieved more efficiently as compared with the spraying in the forward direction.

Since the enamel coating method of the present invention has the construction of the coating brush 122 and / or the air injection nozzle 123 as described above, the fin tube 10 for the heat exchanger, in which the heat transfer fin 12 is formed on the surface of the tube, 10), it is possible to provide excellent effects even when coating a metal tube having a complex surface shape.

In the step (c), the high-temperature firing process of the metal tube is performed at 750 to 1000 ° C, more preferably 750 to 870 ° C. Accordingly, the firing chamber 130 is provided with a heating means. As the heating means, any of those commonly used in this field can be used without limitation. For example, an electric furnace, a plasma annealing furnace, a heavy oil furnace, a light oil furnace, a gas furnace, a hydrogen annealing furnace, and an induction heating furnace can be used.

In the present invention, in particular, an induction furnace can be preferably used as the heating means. As the induction heating furnace, an induction heater 131 as shown in FIG. 3 may be preferably used. The induction heater 131 is easy to manufacture in a small size in accordance with the metal tube 10 having a small diameter as compared with the conventional heating means, and has an energy efficiency because it is heated at a close distance.

Particularly, since the metal tube 10 is heated by the induction heating method, heat is generated only on the surface of the metal tube as a conductor, so that the metal tube is first heated and the enamel glaze applied to the surface of the metal tube is heated by the heat, Is more uniformly and firmly bonded to the surface of the metal tube. In addition, coating defects are minimized.

On the other hand, in the case of the conventional heating means, since the heat is transferred to the metal tube through the enamel glaze applied to the outer surface of the metal tube, the enamel glaze is heated first and flows in the gravity direction before the metal tube is heated Coating defects are likely to occur, and the robustness of the coating is lower than that of the induction heating method.

In the enamel coating method of the present invention, since the metal tube 10 is infiltrated while rotating, the shape of the induction heater 131 is not a problem. That is, since the metal tube 10 can be heated evenly regardless of the shape of the induction heater 131, all shapes known in the art can be used.

As shown in FIGS. 3 to 5, the induction heater 131 may be a cylindrical or arcuate induction heater (not shown) having a radius of curvature of 5 mm to 150 mm larger than the outer diameter of the metal tube 10 131) can be preferably used. The induction heater may be provided in the moving direction of the metal tube 10 such that the outer surface of the moving molten metal tube 10 and the inner curved surface of the cylindrical shape maintain a constant distance.

The induction heater 131 may include a heating coil 132 forming a shape of a circular tunnel and an alternating current power source (FIG. 5, 134) supplying current to the heating coil. In addition, an insulating cover 133 may be optionally provided on the outside of the heating coil 132.

4, when a metal tube 10 is inserted into a circular tunnel formed by the heating coil 132 and an alternating current is supplied, electrical resistance due to eddy current occurs on the surface of the metal tube, Heat is generated on the surface.

5 is an image of the manufacturing process of the induction heater 131. FIG. As shown in FIG. 5, the induction heater 131 is configured in such a manner that the heating coil 132 is formed in a circular tunnel shape and the AC power source 134 is supplied.

FIG. 6 is a photograph of the state of the metal tube 10 heated by the induction heater 131 manufactured in FIG. From FIG. 6, it can be seen that the entire tube is heated in red.

5 and 6, the surface temperature of the metal tube 10 reached 800 캜 after 1 minute and 11 seconds from the start of the heating. Therefore, it can be confirmed that the firing of the metal tube 10 can be completed within about two minutes by the induction heater 131.

In the enamel coating method of the present invention, a high-frequency induction heater using a high-frequency current may be preferably used as the induction heater 131.

In order to enamel coating a metal tube, conventionally, a firing chamber capable of accommodating a metal tube was required. However, according to the enamel coating apparatus of the present invention, even a long metal tube can be coated with enamel coating in a coating portion including a compacted firing chamber Can be easily performed. Therefore, the enamel coating method of the present invention has a more economical advantage over the conventional technique when the length of the metal tube is 5 m or more. For example, a fin tube for a heat exchanger used in a generator has a length of 18 m. In this case, a coating chamber having a space of 18 m or more is required for coating by a conventional method, which is uneconomical in terms of energy efficiency and space use. The sintering process can be easily and economically performed in a compacted sintering chamber having a total length of 4 m or less.

The present invention also relates to an enamel coating apparatus of a metal tube as shown in Figs.

In the enamel coating apparatus of the present invention,

A pretreatment chamber 110 for pretreating the surface of the metal tube 10 to be fed while rotating from an in-feed conveyor 200; When the pre-processed metal tube is fed, a coating chamber 120 coating the surface of the metal tube with enamel glaze supplied from an enamel glaze supply nozzle 121 installed therein. And a firing chamber 130 for performing firing at a temperature of 750 to 1000 ° C. when the coated metal tube is fed,

The firing chamber conveyor 600 includes a firing chamber conveyor 600 for conveying the heated metal tube 10 to the output conveyor 300 while supporting the heated metal tube 10 downwardly, And a roller (270).

All of the technical features described above in the enamel coating method can be applied to the enamel coating apparatus of the metal tube, and redundant descriptions thereof are omitted in this section.

The elongated rollers included in the firing chamber conveyor may be installed on an axis that forms an angle of 5 ° to 35 ° in a clockwise or counterclockwise direction with respect to a transverse line perpendicular to the longitudinal direction of the firing chamber conveyor .

It is preferable that the coating unit 100 is installed so that the total length of the coating unit 100 in the direction in which the metal tube is fed is 5 m or less.

In the enamel coating apparatus, the pretreatment chamber 110 of the coating unit 100 is installed such that the total length in the direction of the metal tube 10 is 3 m or less, preferably 1 m or less, Is preferably 2 m or less, preferably 1 m or less, and the firing chamber 130 is preferably provided such that the total length of the firing chamber 130 is 7 m or less, preferably 5 m or less, in order to make the coating portion 100 compact.

The enamel coating apparatus of the metal tube includes an in-feed conveyor 200 for advancing and advancing the metal tube 10 to the pretreatment chamber 110, and a metal tube having been coated from the calcination chamber, And an out-feed conveyor 300 for conveying a plurality of sheets.

2 (a), the in-feed conveyor 200 includes a metal tube mounting portion 240, a gold tube loading portion 250, and a metal tube, The metal tube transfer part 260 transfers the metal tube 10 from the loading part 240 to the loading part 250 at a predetermined time interval to transfer the metal tube 10 to the loading part 250, May be continuously supplied to the coating portion 100. [0050]

In addition, the above-described structure can be applied to an out-feed conveyor 300. FIG. In the out-feed conveyor 300, the coated metal tube 11 is transferred from the metal tube loading part 250 to the metal tube loading part 250.

10: metal tube 11: enamel coated metal tube
12: heat conductive fin 100: coated portion
110: Pretreatment chamber 111: Heating means
112 (132): heating coil 113 (133): insulating cover
114 (134): AC power supply 120: coating chamber
121: Enamel glaze supply nozzle 122: Coating brush
123: air jet nozzle 130: firing chamber
131: Induction heater 200: In-feed conveyor
210: an in-feed conveyor die 220: a motor
230: rotating roller 240: metal tube loading part
250: metal tube loading part 260: metal tube transfer part
270: Long spherical roller 271: Cooling solution circulation passage
300: out-feed conveyor 400: preprocessing chamber conveyor
500: Coating chamber conveyor 600: Conveyor for plastic chamber
The foregoing description is merely illustrative of the technical idea of the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the essential characteristics thereof. Therefore, the technical idea of the present invention is not limited to the above embodiment.

Claims (7)

(a) pre-treating a surface of a metal tube by feeding a metal tube advancing and rotating by an in-feed conveyor into a pretreatment chamber;
(b) coating the surface of the metal tube with an enamel glaze supplied from an enamel glaze supply nozzle installed inside the coating chamber by feeding the metal tube, which has been pretreated in the step, into a coating chamber; And
(c) firing the coated metal tube into the firing chamber and firing at 750 to 1000 ° C in the step (a);
In the step (c), the firing chamber includes a firing chamber conveyor including two or more elongated rollers, and the firing chamber conveyor conveys the metal tube heated by the elongated roller to the output conveyor while supporting the metal tube downward Wherein the method comprises the steps of: The firing roller conveyor according to claim 1, wherein the elongated roller is installed on a shaft forming an angle of 5 to 35 degrees in a clockwise or counterclockwise direction with respect to a transverse line perpendicular to the longitudinal direction of the firing chamber conveyor, Wherein the chamber conveyor rotates and advances the metal tube heated by the elongated roller while supporting the metal tube, and transfers the metal tube to the output conveyor. The method according to claim 1 or 2, wherein the elongated roller includes a cooling solution circulation passage passing through a rotation axis, and the step (c) further comprises circulating the cooling solution through the cooling solution circulation passage Enamel coating method of a metal tube. The enamel coating method of a metal tube according to claim 1, wherein the metal tube is a fin tube for a heat exchanger having heat conductive fins formed on a tube surface. A pretreatment chamber for pretreating the surface of the metal tube to be fed while rotating from an in-feed conveyor; A coating chamber for coating the surface of the metal tube with an enamel glaze supplied from an enamel glaze supply nozzle installed therein when the pre-processed metal tube is fed; And a firing chamber for performing firing at a temperature of 750 to 1000 ° C when the coated metal tube is fed,
Wherein the firing chamber is provided with a firing chamber conveyor for conveying the heated metal tube to an output conveyor while supporting the fired metal tube, and the firing chamber conveyor includes two or more elongated rollers. The firing chamber conveyor according to claim 5, wherein the elongated roller included in the firing chamber conveyor is an axial shaft which forms an angle of 5 to 35 degrees in a clockwise or counterclockwise direction with respect to a transverse line perpendicular to the longitudinal direction of the firing chamber conveyor Wherein the enamel coating apparatus of the metal tube is provided with an enamel coating apparatus. 7. An in-feed conveyor according to claim 6, wherein the in-feed conveyor and the output conveyor each comprise at least two elongate rollers, Is installed on a shaft forming an angle of 5 ° to 35 ° in a clockwise or counterclockwise direction with respect to a transverse line at right angles.

Images