KR101779589B1 - Coating apparatus for coating inside and outside of steel pipe and a coating method thereof - Google Patents

Abstract

The present invention can prevent the leakage of noxious gas by heating a steel pipe by a heating device such as an induction heater and maintain a constant temperature throughout the steel pipe to reduce the quality deviation of the thermosetting epoxy powder coating, The inside surface and the outside surface of the steel pipe are coated so that the inner surface coating portion enters the inside of the rotating steel pipe to improve the coating quality of the steel pipe by reducing the gap between the outer surface and the inner surface of the heated steel pipe The present invention relates to an inner and outer coating apparatus for a steel pipe and a coating method therefor.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating apparatus for coating inner and outer surfaces of a steel pipe,

The present invention relates to an inner and outer coating apparatus and a coating method of a steel pipe. More particularly, the present invention relates to an inner and outer coating apparatus for a steel pipe, The present invention relates to an inner and outer coating apparatus of a steel pipe and a coating method thereof, which can improve the coating quality of a steel pipe by reducing the gap between the outer surface and the inner surface of the heated steel pipe.

In general, pipes are used for various purposes in various kinds of prefabricated structures, and these pipes are mainly made of a metal such as steel. In recent years, pipes having a metal surface treatment, a pipe coated with liquid paint, Coated pipes coated with synthetic resin have been widely used.

In particular, the synthetic resin coated pipe can be provided with an exquisite appearance by processing various colors on its outer surface depending on the color of the synthetic resin to be coated.

These pipes, which are used as water supply and drainage pipes, use mostly steel pipes due to high water pressure.

The steel pipe is coated on the inner and outer surfaces to prevent corrosion by the fluid. At this time, a liquid resin or a resin powder is used as a coating material for coating the steel pipe.

In the method of coating a steel pipe using powder, the surface of the steel pipe is pre-treated so that the paint is adhered well, and the steel pipe is pre-heated to about 200 ° C to 230 ° C using a heating device. Next, powder coating is sprayed on the preheated steel pipe at a constant thickness. Then, the powder coating is melted by the heat of the steel pipe and hardened to form a coating film.

On the other hand, such a conventional steel pipe coating apparatus is disclosed in Korean Patent Laid-Open Nos. 10-2010-0012538 and 10-0992571.

Since the coating apparatus of the conventional steel pipe can not coat the inner surface and the outer surface of the pipe together, it takes a long time for the coating operation. In order to coat the inner surface of the pipe, liquid paint or resin is used. There is a problem that harmful substances that are generated are discharged.

As a conventional prior art for improving this, Korean Patent Registration No. 10-1446197 entitled "Device for simultaneously coating a plastic powder on both sides of a metal pipe and a metal pipe coated with a plastic powder on both sides thereof" .24) a pipe rolling mill having a frame and a plurality of turning rollers provided on top of the frame; And a powder spray gun which is charged into the metal pipe rotated by the turning roller and moves back and forth; A plastic powder flame coater disposed adjacent to an outer circumferential surface of the metal pipe; At least one plastic powder feeder supplying the plastic powder and connected to the plastic powder sprayer and the plastic powder flame coater, respectively; An air compressor communicating with at least one or more of the plastic powder feeder and the plastic powder jetting road organ and the plastic powder flame coater; And a combustion gas storage container communicating with the one or more plurality of plastic powder flame coaters and supplying a combustion gas, wherein the plastic powder spray is also provided on both sides of the metal pipe by the organs and the plastic powder flame coater, A plastic powder is coated on the inner surface of the metal pipe and the plastic powder is coated on the inner surface of the metal pipe, and two or more plastic powder spray nozzles and two or more plastic powder spray nozzles are provided. The length of one plastic powder spray nozzle is shortened , A short plastic powder spray nozzle, a plastic powder sprayer, a long powder sprayer, and a plastic sprayer with a short length. The spray powder is composed of a powdered epoxy resin or a polyethylene powder, Tid A plastic powder of one of polypropylene, polypropylene, acrylic acid-treated polyethylene, acrylic acid-treated polypropylene or chlorinated polypropylene, or polyamide, or polyvinylidene fluoride or ethylene tetrafluoroethylene plastic powder, Or a surface layer coated with a primer layer, a powdered epoxy or non-polar polyethylene, or a non-polar polypropylene or polyvinylidene fluoride or the like through a long plastic powder spray gun, Or one or more plastic powders are covered and coated on the inner surface of the metal pipe at the same time or more than two or more layers of plastic resin at the same time and the outer surface of the metal pipe is coated with the plastic powder, The plastic powder flame coater is constituted as described above. In one plastic powder flame coater, first, as a plastic material constituting the primer adhesion layer, a powder epoxy or a maleicide polyethylene, a maleicide polypropylene, an acrylic acid-treated polyethylene, Or chlorinated polypropylene or polyamide or polyvinylidene fluoride to form a surface layer in which the plastic powder is melted and coated with a single layer, or a powdered epoxy resin, a powdered epoxy resin, a maleicide resin, A plastic powder such as polypropylene, acrylic acid-treated polyethylene, acrylic acid-treated polypropylene or chlorinated polypropylene, or polyamide or polyvinylidene fluoride is put into the plastic powder to melt the plastic powder The surface of the primer coating layer constituting the surface layer coated with one layer is coated with a powdery epoxy or non-polar polyethylene powder, or a non-polar polypropylene powder or polyamide, or a polyvinylidene fluoride Or one or more different kinds of plastic powders to coat the outer surface of the metal pipe at the same time with two or more layers of the plastic.

In this case, equipment such as a compressed air storage tank, a combustion gas storage container, and an air compressor are required to supply a compressed gas and a combustion gas to a plastic powder flame coater for coating the outer surface of a steel pipe, The temperature of the steel pipe is controlled in real time in a process of selectively spraying only the plastic powder, providing only the flame heat, or spraying the plastic powder, It is troublesome to select the coating operation according to the measured and measured temperature.

In addition, in the case of a plastic powder flame coating machine, when the deviation of the portion where the flame heat is transmitted is generated along the outer surface portion of the steel pipe to which the flame flame is directly transferred, there is a possibility that the thickness of the melted plastic powder coating may be changed. Or harmful gas may be generated.

Other prior art techniques for coating existing steel tubes include Korean Patent Registration No. 10-1141583 entitled " Tube Coating Apparatus Using Epoxy Powder, Tube Coating Method Using Epoxy Powder, and Powder Epoxy Coated Steel Pipe Produced Therefrom " A steel pipe rotating part for rotating the steel pipe, the steel pipe being heated to 170 占 폚 to 300 占 폚 is seated; An outer coating part positioned above the steel pipe so as to be spaced apart from the steel pipe and applying an epoxy powder to the outer surface of the steel pipe; An inner surface moving coating unit movably installed on one side of the steel pipe rotating unit to be inserted into the inner surface of the steel pipe and moving while spraying an epoxy powder on the inner surface of the steel pipe; And a non-acid powder suction unit for covering the open both ends of the steel pipe seated on the steel pipe rotating part and sucking the epoxy powder scattered by the spray of the inner surface moving coating part to the outside of the steel pipe, A first cover case movably installed on one side of the steel pipe so as to cover one side of the steel pipe; A second cover case movably installed on the other side of the steel pipe so as to cover the other side of the steel pipe; And a dust collector connected to the first cover case through a duct to suck air in the first cover case.

Such a conventional coating apparatus for a steel pipe has a structure in which an outer side of a steel pipe is coated with an epoxy powder and then a steel pipe is heated using a heating apparatus such as a heat treatment furnace in the process of coating the inside of the steel pipe with epoxy powder, A time gap is formed between the outer side of the steel pipe and the inner side of the steel powder coating process so that the steel pipe is cooled to cause a temperature difference between the front end portion and the rear end portion of the steel pipe, There is a problem that the coating quality of the steel pipe is varied depending on the temperature variation.

Therefore, there is a need for a technique for improving the coating quality by minimizing the cooling deviation of the steel pipe by reducing the gap of the powder coating operation between the outer surface and the inner surface of the steel pipe during the powder coating process of the steel pipe.

Korean Patent Registration No. 10-1446197 entitled "A device for simultaneously coating a plastic powder on both sides of a metal pipe and a metal pipe coated with a plastic powder on both sides thereof" (Registered on April 24, 2014) Korean Registered Patent No. 10-1141583 entitled " Tube Coating Apparatus Using Epoxy Powder, Tube Coating Method Using Epoxy Powder, and Powder Epoxy Coated Steel Pipe Produced Therefrom "(Registered on April 24, 2012)

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a method and apparatus for heating a steel pipe with a heating device such as an induction heater, The inner and outer coatings of the steel pipe are improved so as to improve the coating quality of the steel pipe by reducing the gap between the coating process of the outer surface and the inner surface of the heated steel pipe by coating the inner and outer surfaces of the steel pipe by entering the inside of the steel pipe And a coating method thereof.

Another object of the present invention is to provide a coating apparatus for an inner and outer coating of a steel pipe improved in structure so that the steel pipe can be easily transferred to the outer surface coating portion and the inner surface coating portion by allowing the steel pipe to be moved in the horizontal direction while rotating the steel pipe in the lateral direction movement .

According to an aspect of the present invention, there is provided an inner and outer coating apparatus for a steel pipe, including: a vertical transfer unit for vertically transferring a steel pipe; A transverse direction conveying part for horizontally conveying the steel pipe conveyed from the longitudinal conveyance part; Heating means for heating the steel pipe to be transported in the transverse direction; An outer coating part for applying the epoxy powder to the outer surface of the steel pipe heated by the heating device; And an inner surface coating portion disposed to be movable in a lateral direction at a position spaced apart from the outer surface coating portion and entering the inner side of the steel pipe to be transported in the transverse direction at the time of lateral movement to apply the epoxy powder, The coating unit includes a moving carriage which can move and return in a direction corresponding to the steel pipe to be transversely conveyed on the moving rail, a base mounted on the moving carriage, and a base provided on one side of the base, A first injection nozzle provided on an end side of the support bar for applying an epoxy powder to an inner surface of the steel pipe, and a second injection nozzle disposed inside the support bar, An epoxy supply pipe for supplying the molten resin to the nozzle side, It is charged, characterized by consisting of a cooling tube to cool the supply pipe epoxy.

The transverse direction conveying unit includes a conveying wheel disposed on the left and right sides of the conveyed steel pipe in an oblique manner, and a conveying wheel that is axially coupled to the conveying wheel, supports the conveying wheel so as to be spaced apart from the ground, And a cooling water nozzle disposed at an end of the hose member for spraying cooling water onto a surface of the conveyance wheel.

The heating means is an induction heater, and the heating temperature of the steel pipe is 180 to 250 ° C.

The inner coating portion may include a dust hopper provided below the support bar for sucking a foreign substance adhered to the inner surface of the steel pipe, and a dust chamber disposed inside the support bar and providing a vacuum suction force to the dust hopper, An epoxy recovery hopper which is disposed on a rear side of the first injection nozzle and which is fixed to the support bar and recovers the epoxy powder sprayed from the first injection nozzle; And an epoxy recovery pipe connected to the recovery hopper and sucked to recover the epoxy powder sucked from the epoxy recovery hopper.

Wherein the outer surface coating portion is disposed on the inner side of the inner surface of the outer surface coater, and the second surface coating portion is provided on the outer surface of the outer surface coating portion, And an injection nozzle.

Another aspect of the present invention is a method for coating inner and outer surfaces of a steel pipe, comprising the steps of: a steel pipe preparation step for continuously supplying a steel pipe to a side of a lateral direction transfer part; A steel pipe transferring step of transferring the steel pipe in the lateral direction in the lateral transferring part; A steel pipe heating step of heating the steel pipe while allowing the steel pipe to be conveyed to pass through the heating means disposed on the movement path of the steel pipe; A steel pipe outer surface coating step of coating the outer surface of the steel pipe by applying the epoxy powder to the outer surface of the heated steel pipe while passing the heated steel pipe through the outer surface coating portion disposed at the outlet side of the heating means; Coating the inner surface of the steel pipe by applying an epoxy powder to the inner surface of the steel pipe to be introduced into the inner surface coating portion into the steel pipe to be passed through the outer surface coating portion; A step of withdrawing an inner coating part for withdrawing and separating the inner surface coating part from the steel pipe after the coating operation of the inner surface coating part is completed; And a steel pipe withdrawing step of vertically transferring the steel pipe separated from the outer surface coating part and the inner surface coating part, wherein the inner surface coating part is movable on the movable rail in a direction corresponding to the steel pipe transversely conveyed A support bar which is provided on the end side of the support bar so as to be protruded from one side of the base and which enters the inside of the steel pipe when the movable carriage is moved in the lateral direction, An epoxy supply pipe disposed inside the support bar for supplying the epoxy powder to the first injection nozzle side, and an epoxy supply pipe wound on the outside of the epoxy supply pipe and filled with cooling water in the interior thereof, And a cooling pipe for cooling the epoxy supply pipe.

The present invention adopts a heating method by an induction heater to maintain a constant temperature throughout the steel pipe without releasing noxious gas, thereby reducing the quality deviation of the thermosetting epoxy powder coating material. In addition, It is possible to reduce the temperature variation of each part of the steel pipe caused by the heat of the steel pipe being cooled by minimizing the gap of the start time of the coating operation, thereby improving the coating quality of the steel pipe.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing a structure of an inner and outer coating apparatus of a steel pipe according to the present invention; Fig.
Figure 2 shows the lateral transfer part of the invention.
3 is a block diagram showing the configuration of the inner surface coating portion of the present invention.
4 is an internal configuration view of the inner surface coating portion of the present invention.
FIGS. 5A, 5B and 5C are explanatory diagrams sequentially showing the coupling operation of the outer surface coating portion and the inner surface coating portion of the present invention. FIG.
6 is a flow chart sequentially showing inner and outer coating methods of a steel pipe according to the present invention.
FIG. 7 is a graph showing the results of measurement of temperature change of a steel pipe by a heating method using a conventional heat treatment furnace, and FIG. 8 is a graph showing a measurement result of temperature variation of a steel pipe according to a heating method using the induction heater of the present invention .
9 to 15 are graphs showing test results of the curing degree of the test piece for each heat treatment temperature.

As shown in FIGS. 1 and 6, a method of coating inner and outer surfaces of a steel pipe according to the present invention includes a steel pipe preparing step (S100) of continuously supplying a steel pipe (10) to a side of a lateral direction transfer part, (10) to the steel pipe (10) while passing the steel pipe (10) through the heating means (200) disposed on the moving path of the steel pipe (10) And an outer coating unit 300 disposed on an outlet side of the heating unit 200. The outer surface of the heated steel pipe 10 is heated by passing the heated steel pipe 10 through the outer coating unit 300, Coating the outer surface of the steel pipe 10 by coating the outer surface of the steel pipe 10 by applying the powder to the outer surface coating unit 300 and the inner surface coating unit 400 into the steel pipe 10 to be passed through the outer surface coating unit 300 An epoxy powder is applied to the inner surface of the steel pipe 10 to be conveyed to form an inner surface of the steel pipe 10 (S500), and a step of withdrawing the inner coating part (400) by withdrawing the inner coating part (400) to a position separated from the steel pipe (10) after the coating operation of the inner surface coating part (S600), and a steel pipe withdrawing step (S700) for vertically transferring the steel pipe 10 separated from the outer surface coating portion 300 and the inner surface coating portion 400. [

The steel pipe preparing step S100 is a step of supplying the steel pipe 10 to the side of the lateral transferring part 100 by using the longitudinal transferring part 50 after performing the ironing work for treating the outer and inner surfaces of the steel pipe 10 .

When the steel pipe 10 is continuously supplied in the longitudinal direction toward the side of the lateral transferring part 100 by using the longitudinal transferring part 50 in the steel pipe preparing step S100 The steel pipe 10 is transported in the lateral direction in the steel pipe feeding step S200 and the steel pipe 10 to be transported in the lateral direction passes through the heating means 200, The epoxy powder coating material is sprayed onto the outer surface of the steel pipe 10 while passing through the outer surface coating part 300 while the heated steel pipe 10 is being transported by the lateral transfer part 100, Coating.

Then, when the front end portion of the steel pipe 10 passes through the outer surface coater 305, the inner surface coating portion 400 is moved laterally to the steel pipe 10 side on the moving rail 405 to enter the inside of the steel pipe 10 The inner surface of the steel pipe 10 is coated by spraying the epoxy powder coating material on the inner surface side of the steel pipe 10 from the inner surface coating portion 400.

At this time, as the steel pipe 10 is moved in the horizontal direction while being spirally rotated by the lateral direction transferring part 100, the epoxy powder paint sprayed from the outer surface coating part 300 and the inner surface coating part 400 is transferred to the inner surface of the steel pipe 10 It is coated uniformly on both outer and inner surfaces.

Thereafter, the inner coating part 400 is returned to its original position and moved to a position where it is not disturbed from the steel pipe 10, and then the steel pipe 10 is transported in the longitudinal direction to complete the coating process of the steel pipe 10.

Referring to FIGS. 1 to 4, the coating apparatus for coating inner and outer surfaces of a steel pipe according to the present invention to which the above-described coating method is applied comprises a longitudinal transferring unit 50 for longitudinally transferring the steel pipe 10, A lateral transfer unit 100 for transferring the steel pipe 10 transferred from the direction transfer unit 50 in the lateral direction, a heating means 200 for heating the steel pipe 10 to be transferred in the lateral direction, An outer coating unit 300 for applying epoxy powder to the outer surface of the steel pipe 10 heated by the outer coating unit 200, And an inner surface coating part 400 for entering the inner side of the steel pipe 10 to be transported in the transverse direction to apply the epoxy powder.

The longitudinal transferring part 50 continuously and periodically supplies the steel pipe 10 to the side of the transverse conveying part 100. The steel pipe 10 is provided on the longitudinal rail using a bogie or kicker device Can be transported.

As shown in FIG. 2, the transverse conveyance unit 100 includes a conveyance wheel 110 disposed in an oblique direction on the left and right sides of the steel pipe 10 conveyed from the longitudinal conveyance unit 50, A rotation shaft 115 which is axially coupled to the conveying wheel 110 to support the conveying wheel 110 from the ground and rotates the conveying wheel 110 in response to the rotational force of the motor, And a cooling water nozzle 125 disposed at the end of the hose member 120 for spraying the cooling water onto the surface of the conveyance wheel 110. [

The conveying wheel 110 arranged in a diagonal line can adjust the lateral conveying speed of the steel pipe 10 by adjusting the angle and the rotational speed so that the lateral conveying unit 100 can control the conveying speed of the steel pipe 10, (10) is transferred in the lateral direction while rotating in the spiral direction.

The heating means 200 employs an induction heater, not a heat treatment furnace, and it is preferable to heat the steel pipe 10 to a temperature of 180 to 250 ° C.

When the heating temperature of the heating means 200 is less than 180 ° C, the coated epoxy powder is not easily cured. When the heating temperature is higher than 250 ° C, the epoxy powder coating may be carbonized.

The inner coating part 400 includes a moving carriage 410 capable of moving and returning in a direction corresponding to the steel pipe 10 being traversed on the moving rail 405 and a moving carriage 410 mounted on the moving carriage 410, A support bar protruding from one side of the base 415 and adapted to enter the inside of the steel pipe 10 when the moving bogie 410 is moved in the lateral direction, A first injection nozzle 435 provided on an end of the support bar 420 for applying an epoxy powder to the inner surface of the steel pipe 10; An epoxy supply pipe 430 for supplying the powder to the first injection nozzle 435 side and a cooling pipe wound around the epoxy supply pipe 430 and filled with cooling water to cool the epoxy supply pipe 430 440).

The base 415 is provided with a controller for adjusting the height of the support bar 420 and controlling the moving speed of the moving bogie 410.

The inner surface coating part 400 includes a dust hopper 455 provided below the support bar 420 for sucking foreign substances adhered to the inner surface of the steel pipe 10, A dust collecting pipe 450 disposed inside the dust hopper 455 and supplying a vacuum suction force to the dust hopper 455 to suck foreign matter sucked through the dust hopper 455, An epoxy recovery hopper 465 disposed in the support bar 420 and adapted to recover epoxy powder sprayed from the first injection nozzle 435 and an epoxy recovery hopper 465 connected to the epoxy recovery hopper 465, And an epoxy recovery pipe (460) sucked to recover the epoxy powder sucked from the pipe (465).

The inner surface coating part 400 includes a connecting member 475 connected to the lower side of the supporting bar 420 and a connecting member 475 disposed at the end of the connecting member 475 and contacting the inner circumferential surface of the steel pipe 10, And a guide wheel 470 for supporting the movement of the supporting bar 420.

The outer surface coating unit 300 includes an outer surface coater 305 provided in a tunnel shape to allow the steel pipe 10 to be transported in the lateral direction to pass therethrough and an outer surface coater 305 disposed at left and right sides of the inner surface of the outer surface coater 305, And a second injection nozzle 310 for spraying the coating liquid onto the outer surface of the steel pipe 10.

As the steel pipe 10 is transported in the lateral direction by the transverse transfer unit 100, the steel pipe 10 passes through the outer surface coater 305 and the steel pipe 10 is transferred to the outer surface coater 305, the epoxy powder is sprayed from the second injection nozzle 310 and is applied to the outer surface of the steel pipe 10.

The reference numerals 30 and 40 denote the external surface microwave ovens 30 and the internal microwave ovens 40 of the steel pipe 10 and perform a microwave treatment for removing the rust on the outer surface and the inner surface of the steel pipe 10 do.

In the present invention having such a configuration, when the steel pipe 10 is fed longitudinally by using a bogie or kicker device of the longitudinal direction transfer part 50 and supplied to the lateral direction transfer part 100 side, the transfer wheel 110 is transferred The steel pipe 10 is conveyed in the transverse direction in the longitudinal direction of the steel pipe 10 while rotating the steel pipe 10 in the spiral direction by the rotational driving force of the conveyance wheel 110 arranged in an oblique direction with respect to the advancing direction of the steel pipe 10 .

The steel pipe 10 conveyed by the transverse conveyance unit 100 is heated to an appropriate temperature while passing through the induction heater serving as the heating means 200. The heated steel pipe 10 is coated on the outer surface of the outer coating unit The epoxy powder sprayed through the second injection nozzle 310 is coated on the outer surface of the steel pipe 10 and coated on the outer surface of the steel pipe 10 as shown in FIG. .

At this time, since the steel pipe 10 is rotated in the spiral direction by the lateral transfer unit 100, the epoxy powder injected through the second injection nozzle 310 is uniformly applied to the outer surface of the steel pipe 10.

When the end portion of the support bar 420 of the inner surface coating portion 400 is advanced to the inside of the steel pipe 10 to be transported in the lateral direction when a part of the tip of the steel pipe 10 passes through the outer surface coating portion 300, The end of the support bar 420 is supported on the inner surface of the steel pipe 10 being conveyed while the wheel 470 is in contact with the inner surface of the steel pipe 10 and is sprayed through the first injection nozzle 435 The epoxy powder is applied to the inner surface of the steel pipe 10.

At this time, the inner coating part 400 moves the supporting bar 420 to the steel pipe 10 on the moving rail 405 provided on the ground at a time corresponding to the start of coating the outer surface of the steel pipe 10, The gap between the outer surface coating and the inner surface coating operation of the steel pipe 10 can be minimized as the inner surface coating operation of the steel pipe 10 proceeds after the initial outer surface coating of the steel pipe 10 is performed .

The epoxy powder is supplied to the first injection nozzle 435 through an epoxy supply pipe 430 disposed inside the support bar 420 and is supplied to the side of the first injection nozzle 435 by a cooling pipe 440 wound on the outer circumferential surface of the epoxy supply pipe 430 It is possible to prevent the epoxy powder from melting due to heat transmitted from the support bar 420 as it is cooled.

At this time, the dust hopper 455 provided at the tip of the support bar 420 sucks foreign matter such as dust, which is stuck on the inner circumferential surface of the steel pipe 10, by a vacuum suction force, The epoxy recovery hopper 465 disposed behind the first injection nozzle 435 discharges the epoxy powder remaining in the dust form without being applied to the inner surface of the steel pipe 10 by vacuum suction And collected through the epoxy return pipe 460 disposed inside the support bar 420 to the outside.

The outer surface coating work of the steel pipe 10 is coated by a Fusion Bonded Epoxy (FBE) coating method in which an epoxy powder is coated by an electrostatic coating method.

5C, after the outer surface of the steel pipe 10 is coated with the outer surface of the steel pipe 10, the inner surface coating unit 400 is returned from the steel pipe 10 to the inner surface of the steel pipe 10 And the steel pipe 10 is transported in the longitudinal direction using the longitudinal transfer unit 50, the coating process of the steel pipe 10 is completed.

In the present invention, the heating process of the steel pipe 10, the outer surface coating process and the inner surface coating process are continuously performed on the same axial line, and the outer surface coating of the steel pipe 10 after the heating of the steel pipe 10 and the start The time gap can be minimized and the coating quality of the steel pipe 10 can be improved.

FIGS. 7 and 8 are graphs showing the temperatures of the steel tube 10 heated by the conventional heat treatment furnace and the temperature of the steel tube 10 heated by the heating means according to the present invention, Is assumed to be 5 minutes before the start of coating after the heating by the heating means 200. When the rotation speed of the steel pipe 10 is 41 rpm and the cargo conveyance speed of the inner coating portion 400 is 1.5 m / The measurement results at the temperature measuring points of 0.2 m, 6.0 m and 11.8 m from the tip of the steel pipe 10 are shown.

In this case, as shown in FIG. 7, as the time for transporting and coating the steel pipe 10 heated by the conventional heat treatment furnace has elapsed, the temperature suddenly drops, while the temperature of the steel pipe 10 heated by the induction heater As shown in FIG. 8, it can be seen that the temperature change of the steel pipe 10 is relatively small at the coating time of the steel pipe 10.

9 to 15 are graphs showing the results of the DSC hardness test of the epoxy powder coating according to the heat treatment temperature of the coating apparatus of the present invention and the test piece coated by the coating method.

Fig. 9 shows the test results of the specimens heated to 150 DEG C, Fig. 10 shows the results at 187 DEG C, Fig. 11 shows the results at 214 DEG C, Fig. 12 shows the results at 222 DEG C, The graph of the test results of the heated specimen is shown.

? Tg: glass transition temperature difference,

Tg4 is the glass transition temperature of the reference sample,

Tg3: Glass transition temperature of the test sample

ΔH: reaction heat of the powder

DELTA H1: the heat of reaction of the coating film,

(ΔH-ΔH1) / ΔH × 100 of the conversion rate (%).

The full curing condition is completely cured when ΔTg is 5 ° C or lower and the conversion rate is 95% or more.

In the curing test of the test piece according to the above heat treatment temperature, the test piece heated to 257 ° C or higher had a glass transition temperature difference (ΔTg) of less than 5 ° C and fully cured, but in the case of a test piece heated to 238 ° C or less, (? Tg) exceeded 5 占 폚 and complete curing did not occur.

However, since the test piece has a thickness of 3 mm and a dimension of 300 × 150 mm, the cooling rate is faster than the actual steel pipe, so that the test piece heated at 280 ° C., which is outside the use range of the epoxy powder, And then cooled to a temperature below the carbonization temperature.

Thus, when the actual steel pipe is heated, complete curing is performed even at a lower temperature than the test piece.

Therefore, as described above, it is preferable to heat the steel pipe at a temperature in the range of 180 to 250 占 폚.

Accordingly, there is a risk that the paint quality may be varied in the strat part, the middle part, and the end part due to the heating temperature variation of the steel pipe during the FBE coating after heating in the conventional furnace system. However, , It is possible to prevent the discharge of harmful gas and it is possible to maintain a constant temperature throughout the steel pipe to reduce the quality deviation of the thermosetting epoxy powder coating material and to prevent the coating of the outer surface of the steel pipe and the coating It is possible to reduce the temperature deviation of each part of the steel pipe (front end, middle, rear end) as the heat of the steel pipe is cooled by minimizing the time gap, thereby improving the coating quality of the steel pipe.

10: Steel pipe 30: External surface treatment device
40: Internal medicine dispenser 50: Longitudinal transfer part
100: transverse direction feeding part 200: heating means
300: outer coating part 305: outer surface coating machine
310: second injection nozzle 400: inner surface coating part
405: Moving rail 410: Moving carriage
415: base 420: support bar
430: epoxy supply pipe 435: first injection nozzle
440: Cooling tube 450: Dust recovery tube
455: Dust hopper 460: Epoxy recovery pipe
465: Epoxy recovery hopper 470: Guide wheel
475:

Claims (6)

A longitudinal transferring section 50 for longitudinally transferring the steel pipe 10;
A lateral conveying part (100) for conveying the steel pipe (10) conveyed from the vertical conveying part (50) in the lateral direction;
Heating means (200) for heating the steel pipe (10) transported in the transverse direction;
An outer coating part 300 for applying an epoxy powder to the outer surface of the steel pipe 10 heated by the heating device 200; And
An inner coating part 400 (hereinafter, referred to as " outer coating part ") 400 which is disposed to be movable in the lateral direction at a position spaced from the outer surface coating part 300 and enters the inside of the steel pipe 10 to be transported in the transverse direction at the time of lateral movement, ), ≪ / RTI >
The inner surface coating unit 400 includes a moving truck 410 capable of moving and returning in a direction corresponding to the steel pipe 10 being traversed on the moving rail 405, A supporting bar 420 protruding from one side of the base 415 and entering the inside of the steel pipe 10 when the moving car 410 is moved in a lateral direction; A first injection nozzle 435 provided on an end of the support bar 420 to apply an epoxy powder to the inner surface of the steel pipe 10 and an epoxy powder disposed inside the support bar 420, And a cooling pipe (440) wound on the outer side of the epoxy supply pipe (430) and filled with cooling water to cool the epoxy supply pipe (430) , External coating equipment. The method according to claim 1,
The transverse conveyance unit 100 includes a conveyance wheel 110 disposed on the left and right sides of the conveyed steel pipe 10 in an oblique manner,
A rotating shaft 115 axially coupled to the feed wheel 110 to support the feed wheel 110 away from the ground and to receive the rotational force of the motor to rotate the feed wheel 110,
A hose member 120 for supplying cooling water to the conveying wheel 110 and a cooling water nozzle 125 disposed at an end of the hose member 120 for spraying cooling water onto the surface of the conveyance wheel 110 Wherein the inner surface and the outer surface of the steel pipe are coated with a coating material. The method according to claim 1,
Wherein the heating means (200) is an induction heater, and the heating temperature of the steel pipe (10) is 180 to 250 占 폚. The method according to claim 1,
The inner surface coating part 400 includes a dust hopper 455 provided at a lower end of the support bar 420 to suck foreign matter adhered to the inner surface of the steel pipe 10,
A dust collecting pipe 450 disposed inside the support bar 420 and providing a vacuum suction force to the dust hopper 455 to suck foreign matter sucked through the dust hopper 455,
An epoxy recovery hopper 465 disposed on the rear side of the first injection nozzle 435 and fixed to the support bar 420 to recover the epoxy powder sprayed from the first injection nozzle 435,
Further comprising an epoxy recovery pipe (460) connected to the epoxy recovery hopper (465) and sucked to recover the epoxy powder sucked from the epoxy recovery hopper (465). The method according to claim 1,
The outer surface coating unit 300 includes an outer surface coater 305 provided in a tunnel shape to allow the steel pipe 10 to be transported in the lateral direction to pass therethrough,
And a second injection nozzle (310) arranged on left and right sides of the inner surface of the outer surface coater (305) for spraying and spraying epoxy powder onto the outer surface of the steel pipe (10) Device. A steel pipe preparation step (S100) for continuously supplying the steel pipe (10) to the side of the lateral transfer part (100);
A steel pipe feeding step (S200) of feeding the steel pipe (10) in the lateral direction in the lateral direction feeding part (100);
A steel pipe heating step (S300) of heating the steel pipe (10) while passing the steel pipe (10) through the heating means (200) disposed on the movement path of the steel pipe (10);
An epoxy powder is applied to the outer surface of the heated steel pipe 10 while passing the heated steel pipe 10 through the outer surface coating portion 300 disposed at the outlet side of the heating means 200, Coating a steel pipe outer surface coating step (S400);
The inner coating part 400 is introduced into the steel pipe 10 to be passed through the outer coating part 300 and the inner surface of the steel pipe 10 is coated with the epoxy powder on the inner surface of the steel pipe 10 Coating a steel pipe inner surface coating step (S500);
A step S600 of withdrawing an inner coating part for withdrawing and separating the inner surface coating part 400 from the steel pipe 10 after the coating operation of the inner surface coating part 400 is completed; And
A steel pipe withdrawing step S700 for longitudinally transferring the steel pipe 10 separated from the outer surface coating part 300 and the inner surface coating part 400,
The inner surface coating unit 400 includes a moving truck 410 capable of moving and returning in a direction corresponding to the steel pipe 10 being traversed on the moving rail 405, A supporting bar 420 protruding from one side of the base 415 and entering the inside of the steel pipe 10 when the moving car 410 is moved in a lateral direction; A first injection nozzle 435 provided on an end of the support bar 420 to apply an epoxy powder to the inner surface of the steel pipe 10 and an epoxy powder disposed inside the support bar 420, And a cooling pipe (440) wound on the outer side of the epoxy supply pipe (430) and filled with cooling water to cool the epoxy supply pipe (430) , Outer surface coating method.

Images