JPH0466164A - Method for coating outer surface of steel pipe - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a film by a method wherein a part of a steel pipe is coated on the way of on-line feed to be stayed in a hot air atmosphere and a cooling air atmosphere and, next, the remainder thereof is applied to be stayed in hot and cooling air atmospheres for the same time to forcibly dry and cure the coated film. CONSTITUTION:A steel pipe (p) subjected to painting is placed on a chain conveyor 71 by a steel pipe feed apparatus 21 and moved through a drying chamber 61 by the chain conveyor 71 to forcibly volatilize the solvent component of the coating material on the steel pipe (p). The drying chamber 61 is set to a hot air atmosphere of 60 - 100 deg.C by a hot air generator 81 and the feed speed of the chain conveyor 71 is controlled so that the steel pipe is stayed for 5 - 20min within the drying chamber 61 and subsequently guided to a cooling chamber 91 set to a cooling atmosphere of 20 deg.C or lower by a cooling air generator 101 to be stayed for 10 - 40min within the cooling chamber 91 to cure the coated film. By this method, the damage of the film or hue irregularity is eliminated and the film of high quality is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for on-line painting the external surface of a steel pipe with good coating quality without impairing the working environment.

(Prior art) The exterior coating of steel pipes is done for the purpose of corrosion prevention.
Various paints are atomized and a paint film is formed on the outer surface of the steel pipe to a thickness that achieves the unique performance of the paint.

By the way, in general, when painting the outer surface of a steel pipe, a method is used in which a partial coating is first applied, the coating is dried, the steel pipe is supported on the dried coating surface, and the remaining unpainted parts are painted.

(Problem to be solved by the invention) Regarding quick-drying paints that dry relatively quickly, such as primary rust prevention paints, is there a way to force dry them using online painting equipment? After that, the entire steel pipe is preheated to perform forced drying, and when painting the next unpainted part, the paint film will soften, causing damage to the painted part and uneven color of the painted part of the vermilion painted part. There is a problem of deterioration of coating film quality.

An object of the present invention is to provide a method for painting the outer surface of a steel pipe that can solve the above-mentioned problems.

(Means for Solving the Problems) In order to achieve the above object, the method for painting the external surface of a steel pipe according to the present invention is such that after painting a part of the steel pipe during online transportation, the steel pipe is heated to a temperature of 60 to 100°C in a hot air atmosphere. 5 to 20 minutes at a temperature not exceeding 35℃, then 10 to 40 minutes in a cold air atmosphere below 20℃, then after painting the remaining part, stay in the same hot and cold air atmosphere as above for the same time. Then, after painting the remaining part, the paint film is forced to dry and harden by staying in the same hot air and cold air atmospheres for the same period of time.

In the present invention, the temperature in the hot air atmosphere is set at 60 to 100°C.
This is because if the temperature exceeds 100°C, the paint will boil and a smooth coating surface cannot be obtained, and if the temperature is below 60°C, no drying effect can be obtained.

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In addition, in the present invention, in the hot air atmosphere of 60 to 100°C, the temperature of the steel pipe is 5 to 2°C within a range not exceeding 35°C.
The purpose of allowing the water to stay for 0 minutes is to prevent damage to the paint film of the steel pipe during transportation, and to maintain a good color appearance of the paint film.
This is to obtain the desired drying effect and to minimize the equipment space as much as possible.

In other words, Figure 2 shows that urethane-modified alkyd paint
Figure 2 shows the results when a 5A steel pipe was left in a hot air atmosphere at 80°C for 10 minutes and then transported with the pipe temperature at 10 to 50°C. In this case, it can be determined whether paint film damage occurs or whether it can be prevented.

Next, Figure 3 shows the results of examining the color appearance of the coating film formed on the outer surface of a 15A steel pipe when it was coated with a urethane-modified alkyd paint at a temperature in the range of 10 to 60°C. As shown in Fig. 3, it can be seen that when the steel pipe temperature is kept below 35°C, the color appearance of the coating film can be maintained well.

From the results shown in Figures 2 and 3, the steel pipe temperature was
It can be seen that it is desirable to keep the temperature below 5°C.

In addition, in the present invention, the temperature of the cold air atmosphere is set to 20°C or less because if it exceeds 20°C, the cooling effect will be small and the curing of the coating will be delayed.The temperature is preferably 10 to 20°C, and the cold air is It is easy to obtain and has a great cooling effect.

In addition, in the present invention, the residence time in the cold air atmosphere is 10 to
The reason for setting the time to 40 minutes is to obtain the desired cooling effect and to minimize the equipment space as much as possible.

(Example) The method of the present invention will be explained below with reference to FIG.

FIG. 1(A) is a schematic diagram of an apparatus for painting the outer surface of steel pipes, and FIG. 1(B) is an explanatory diagram showing an outline of the coating.

Reference numeral 1 denotes a base pipe providing stand, and the steel pipe p is transferred from this base pipe providing stand 1 to a raw pipe conveying device 2 installed in the coating room II. The tube is then sent to the tube rotation device 31 and given the required rotation.

41 is a reciprocating device provided above the tube rotating device 31, and has, for example, three painting guns 5, which are connected to the first
A portion of the outer surface of the steel pipe p is coated by moving it in the direction of the pipe axis shown by the arrow in FIG.

In addition, as the secondary rust prevention coating, use a urethane-modified alkyd paint or a butyral paint, with a dry film thickness of 20 to 3.
A coating film of 0 μm is produced.

Then, the coated steel pipe p is transferred to a raw pipe conveying device 2. The coating material is placed on a chain conveyor 71, and the solvent component of the coating material is forcibly volatilized while being moved within the drying chamber 61 by the chain conveyor 71.

By the way, in the method of the present invention, a hot air atmosphere of 60 to 100° C. is created in the drying chamber 61 by the hot air generator 81. The conveyance speed of the chain conveyor 7 is controlled so that the conveyor stays within 5 to 20 minutes.

The steel pipes on the chain conveyor 71 are placed in the drying chamber 6.
After staying there for 20 minutes, the cooling room 9 is created with a cold air atmosphere of 20° C. or lower by the cold air generator 101. I was guided to this cooling room 9. The coating is left in the solution for 10 to 40 minutes to cure the painted area.

Next, from the chain conveyor 7 to the next blank pipe conveying device 2□
The tube is then transferred to a tube rotation device 32 from which it is given the required rotation.

Thereafter, as before, the reciprocating device 42 is moved in the direction of the tube axis to coat the remaining portion, and the coating is forcibly dried and hardened by the chain conveyor 72 through the drying chamber 62 and the cooling chamber 9□.

After that, the conveyor roll 13 passes through the exit skid 12.
It will be transported to

(Effect of the invention) As explained above, when the method of the present invention is applied,
It has the effect of eliminating paint film damage and color unevenness, which were problems in the past, and providing a high-quality paint film.

[Brief explanation of the drawing]

Figure 1 (a) is a schematic diagram of the external surface coating equipment for steel pipes, (b) is an explanatory diagram showing the outline of the coating process, Figure 2 is a diagram showing the experimental results of areas where paint film damage occurs during transport of steel pipes, Figure 3 shows the relationship between steel pipe temperature and paint film color appearance. 6. 62 is a drying room, 7I, 72 is a chain conveyor,
9. ．． 92 is a cooling room, p is a steel pipe. ]Fg (b)

Claims (1)

[Claims] (1) After painting a part of the steel pipe during online transportation, the temperature of the steel pipe is 35°C in a hot air atmosphere of 60 to 100°C.
℃ for 5 to 20 minutes, then stay in a cold air atmosphere below 20℃ for 10 to 40 minutes, then paint the remaining part, stay in the same hot air and cold air atmosphere as above for the same time, and paint. A method for painting the exterior surface of steel pipes, which is characterized by forcibly drying and curing the coating.