JPS5815185B2 - Kinzoku Kanaiment Souhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION When painting the inner surface of a metal tube, the present invention provides a method for controlling the direction in which the coating material is discharged from the pole gun of the coating jig inserted into the tube and the heating position by the induction heating coil surrounding the metal tube. The present invention relates to a method for painting the inner surface of a metal pipe, which comprises adjusting the inner surface of a metal pipe.

Conventionally, the following various methods have been known for coating the inner surface of metal pipes with paint, varnish, anticorrosive paint, heat-resistant paint, etc.

i.e. ■Pole gun insertion method ■Immersion method ■Filling method ■Sphere ball method ■Mixed air flow method ■Rotary coating method etc., and several other methods are also known.

As described above, a large number of methods are known for painting the inner surface of metal pipes, and each of these methods has its own characteristics and is used.

Although the present invention falls under the above method (2), various problems remain in the conventional method (2).

In this pole gun insertion method, regardless of whether the coating material is powder paint or liquid paint, the discharge part of the pole gun is inserted into the metal pipe to be painted, the discharge slot is directed toward the inner surface of the pipe,
Many methods are used to spray paint in a conical pattern.

In this method, the metal tube is rotated and the nozzle is moved in the longitudinal direction of the metal tube to apply the coating, so there is a drawback that spiral-shaped uneven coating marks tend to appear on the painted surface.

Further, after painting in this manner, the painted surface is separately force-dried or baked by heating the metal tube, but there is a drawback that the painted surface tends to sag at this time.

In order to eliminate these drawbacks, there are cases in which powder coating is applied inside a heating furnace, but the complexity of building the heating furnace equipment and the temperature distribution of the metal tube inside the furnace depend on the characteristics of the heating furnace. However, there were disadvantages such as unevenness in coating film thickness, drying, and baking.

In view of these conventional drawbacks, the present inventors have found a method that eliminates these drawbacks, and provide the method herein.

The present invention involves inserting a pole gun into the inner surface of a metal tube, spraying the coating material uniformly in the circumferential direction of the inner wall of the metal tube while moving either the metal tube or the combination of the pole gun and an induction heating coil, and at the same time applying induction heating to the coating material. (a) When the discharge slot of the coating material of the pole gun precedes the induction heating zone directly under the induction heating coil with respect to the direction of coating progress, the direction of discharge of the coating material from the slot should be set in the direction of the progress of the pole gun. (b) When the discharge slot discharges the coating material in the induction heating zone, the direction in which the coating material is discharged is opposite to or perpendicular to the traveling direction of the induction heating coil; (c) The induction heating zone When the coating material precedes the coating material discharge slot, the coating material is discharged from the slot in either the forward direction, the opposite direction, or the right angle direction to the traveling direction of the induction heating coil. It's a method.

In this way, the present invention combines the features of the pole gun, which sprays coating liquid or powder evenly over the circumference of the inner surface of the steel pipe, with an induction heating system that can effectively perform zone heating. It is applied to the inner surface coating of steel pipes that rotate around their long axes, and these features are combined to produce a synergistic effect, resulting in uniform coating.

In the case of the present invention, the steel pipe may be stopped, and the pole gun inserted into the pipe and the induction heating coil may be combined and moved relative to the steel pipe, or the pole gun inserted into the steel pipe and the induction heating coil may be combined. It may stop and the steel pipe may move.

In the present invention, both of the above methods can be applied arbitrarily, but it is preferable to use a method in which the steel pipe is fixed and a pole gun and an induction heating coil are combined to run and move along the steel pipe, and the steel pipe is centered around the central axis in the longitudinal direction. Excellent coating results when rotated in place.

The details of the invention will be explained by way of example with reference to the drawings.

Figures 1 to 3 show (a) (
b) It is a longitudinal sectional view showing (c) (only the pole gun is a side view), and the steel pipe is shown in a stopped state.

FIG. 1 is a longitudinal sectional view showing the method of (a) above, in which an induction heating coil 2 surrounding the outer diameter of a steel pipe 1 is provided, a pole gun 3 is disposed inside the steel pipe, and a coating material is passed from this pole gun 3. 4 is discharged onto the inner surface 5 of the steel pipe.

The shape of the pole gun according to the present invention will be explained next.

The nozzle of this pole gun 3 has a trumpet-shaped end with an enlarged discharge slot, and a slot 6 is provided in an annular shape (partially connected in some places, the same applies hereafter) on the circumference of the enlarged part. is shown in FIG. 4P, and in this case, if the pole gun 3 moves in the steel pipe in the direction of the arrow 7, the discharge direction arrow 8 of the coating material 4 is backward and in the opposite direction to the traveling direction of the pole gun.

Similarly, in Fig. 4 Q, the coating material 4 is completely covered by the arrow 9 from the enlarged part.
It is a discharge slot with an open diameter and discharges in the direction opposite to the direction in which the pole gun 3 moves.

In FIG. 4R, the slots 10 are provided in the circumferential direction of the enlarged part, so that the coating material 4 can be said to be discharged in a radial or perpendicular direction (arrow 11) onto the outer layer of the enlarged part.

Figure 4 S shows a slot 1 in the peripheral wall of the inclined part of the nozzle in the enlarged part.
2 is produced, and it can be said that the discharge is in the same direction (arrow 13) as the traveling direction 7 of the pole gun 3.

Considering the discharge situation of the coating material 4 from the discharge slot of the pole gun 3 of the present invention, the discharge direction of the pole gun 3 used in FIG. 1 is the discharge direction arrow 8 in FIG. 4P,
The arrow 9 in the discharge direction in FIG. 4Q is required, and the discharged coating material at this time collides with the induction heating zone.

That is, the discharge direction arrow 8.9 of the coating material of the pole gun 3 is the discharge direction opposite to the traveling direction 7 of the pole gun 3,
This case corresponds to the case where the pole gun 3 is ahead of the induction heating coil 2 in the right direction in the figure.

FIG. 2 of the present invention shows the case (b) of the present invention described above, in which the pole gun 3 is located just below the induction coil 2, and in this case, the painted materials P, Q, and R of FIG. The discharge direction of arrows 8, 9, and 11 are required.

In this case, the steel pipe is heated by the induction heating coil 2, and the coating material 4 collides with the inner surface of the steel pipe in the heating zone, so that the inner surface of the steel pipe is coated with anti-adhesion coating, and is also heated and baked.

FIG. 3 of the present invention corresponds to (c) of the present invention, and the induction heating zone of the steel pipe heated directly below the induction heating coil 2 is located to the right of the pole gun 3 as shown in FIG. In this case, the induction heating coil 2 is ahead of the pole gun 3, and at this time, the coating material 4, which has already been heated by the induction heating coil 2 and is discharged onto the inner surface of the steel pipe that forms the heating zone, collides with the inner surface of the steel pipe, as shown in Fig. 4. A sufficient paint baking effect can be obtained with any of P, Q, R, and S.

As described above, the method of the present invention uses the combined effect of the pole gun 3 and the induction heating zone to efficiently apply and fix the coating material to the inner surface of the steel pipe smoothly without uneven coating, and prevents the occurrence of "sagging" or spiral marks. Excellent paint fixation and baking.

Further, the induction heating coil used in the present invention may be one used for ordinary induction heating, and the slotting of the pole gun 3 is simple and can be carried out quickly and easily at low cost.

An SGP pipe 25A was used as the steel pipe, and epoxy resin powder, nylon powder, polyethylene powder, etc. were painted and baked on the inner surface according to the method of the present invention as shown in the table below.

In this case, the induction heating coil installed concentrically around the outside of the steel pipe has a frequency of 150 Hz, an effective power of 15 kW, and an effective voltage of 250 mm.The steel pipe is fixed, and the induction heating coil and the pole gun are moved in the longitudinal direction of the steel pipe at a speed of 150 Hz. It moved 2 meters in 7 minutes.

At this time, the heating relationship between the discharge slot of the pole gun and the induction heating coil was determined as shown in FIGS. 1 to 3.

The results are shown in the table below, and a uniform coating thickness and an excellently smooth coated surface were obtained.

The present invention was applied to various types of paramagnetic metal pipes as well as steel pipes, and similarly excellent results were obtained.

EXAMPLES As described above, the coatings of the examples of the present invention were excellent.

[Brief explanation of drawings]

1 to 3 are vertical cross-sectional views corresponding to (a), (b), and (c), respectively, showing heating forms in the implementation of the present invention. FIG. 4P-8 is a longitudinal sectional view showing the direction of discharge from the discharge slot of the pole gun. DESCRIPTION OF SYMBOLS 1... Steel pipe, 2... Induction heating coil, 3... Pole gun, 4... Painting material, 5... Steel pipe inner surface, 6,10
, 12... Pole gun discharge slot, 8, 9, 11
°13...Discharge direction of coating material.

Claims (1)

[Claims] 1. A pole gun is inserted into the inner surface of the metal tube, and while moving either the metal tube or the combination of the pole gun and induction heating coil, a coating material is uniformly sprayed in the circumferential direction of the inner wall of the metal tube, and at the same time induction heating is performed. (a) When the discharge slot of the coating material of the pole gun precedes the induction heating zone directly under the induction heating coil with respect to the direction of painting progress, the direction of discharge of the coating material from the slot is (b) When the discharge slot discharges the paint material in the induction heating zone, the discharge direction of the paint material is opposite to or perpendicular to the direction of travel of the induction heating coil; (c) When the induction heating zone precedes the coating material discharge slot, induction heating coating is performed by setting the discharge direction of the coating material from the slot to either the forward direction, the opposite direction, or the right angle direction to the traveling direction of the induction heating coil. A method for painting the inner surface of a metal tube.