JP3594407B2 - Method and apparatus for coating coated steel on coated steel - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a coating method and a coating apparatus for coating a coating material made of a thermoplastic resin on a coating steel material such as a coating steel pipe (pile), a coating steel shape, a coating steel bar or the like, which requires high corrosion resistance.
[0002]
[Prior art]
As is well known, steel materials, for example, steel pipes are frequently used in transporting gas, water, oil, and the like and in marine structures. In order to improve the corrosion resistance, a resin such as polyethylene, polypropylene, polyamide (nylon), or the like is used. And is often used as a coated steel pipe.
[0003]
In many cases, a plurality of such coated steel pipes are connected and used, and in this case, butt welding is generally used.
When the coating material is coated on the welded portion, the coating material impairs the weldability during welding, and the strength of the welded portion cannot be secured. Further, in the vicinity of the welded portion, the coating material is lost due to the welding heat, and the function as the coating material is lost.
Therefore, when using by welding and joining, it is common practice not to cover the welded portion and its peripheral portion with a coating material, or to remove the coating in advance and re-coat the coating material after welding.
[0004]
Conventionally, as a method of coating a welded portion of a coated steel pipe and a peripheral portion thereof, a heat-shrinkable tube generally comprising a polyethylene layer and an adhesive layer is used, and the tube is heated and heat-shrinked to bond and coat. Coating methods are known.
[0005]
In this coating method, as shown in FIG. 6, a coating c is not formed on the steel pipe P at the joint wp of the coated steel pipes Pa and Pb to be welded and the peripheral portion thereof, or the coating is removed and welding is performed. Before butting the two coated steel pipes Pa and Pb, a heat-shrinkable tube tb composed of two layers of a polyethylene resin ps and an adhesive ss is inserted into one of the coated steel pipes and then butted. Weld.
[0006]
After welding, the welded portion wp and its peripheral portion are brushed to remove extraneous matter, the heat-shrinkable tube tb is positioned so as to cover the welded portion wp and its peripheral portion, and the outer surface of the heat-shrinkable tube tb is positioned. The burner is heated from the side to melt the adhesive ss on the inner surface of the tube tb, and heat-shrink the tube to bond and coat the adhesive ss on the welded portions wp of the coated steel pipes Pa and Pb and the peripheral portions thereof. It was made.
[0007]
However, in this coating method, since the welded portion wp is not flat, as shown in FIG. 7, a gap ao is generated in the stepped portion between the welded portion wp and the coating c of the coated steel pipe, and after the coating, the gap ao is formed. It is inevitable that air remains in the air, and there is a problem that oxidation of the steel pipe P grows in the air remaining portion, and the durability of the steel pipe is reduced.
In addition, it is necessary to uniformly heat the heat-shrinkable tube tb with a burner in order to uniformly heat-shrink the tube. Therefore, the skilled worker is required to have a good construction technique, and the heating requires a long time.
[0008]
In addition, it is necessary to insert a heat-shrinkable tube into one of the coated steel pipes before welding, and it is exposed to the outdoor environment until the construction is completed. It is not uncommon that moisture and the like adhere and remain, thereby impairing the adhesiveness of the adhesive.
A complicated countermeasure for preventing the occurrence of such an inconvenient phenomenon is required, and there is a problem that the construction cost increases.
[0009]
[Problems to be solved by the invention]
The present invention relates to a method for coating polyethylene-based resin, polypropylene-based resin, and polyimide (nylon) -based resin on the outer surface of a coated steel material (including stainless steel and hereinafter referred to as “coated steel material”) such as a coated steel pipe, a coated steel bar, a coated steel bar, and a steel wire. When coating with a coating material made of a thermoplastic resin such as the above, there is no concern about oxidation of the steel pipe due to residual air, a decrease in adhesiveness, and a rise in construction cost. An apparatus is provided.
[0010]
[Means for Solving the Problems]
The first invention of the present invention heats a coating material coating target area of a coated steel material, mounts a split mold on an outer surface of the coated steel material, and inserts a split mold into a gap formed between an outer surface of the coated steel material and a split mold inner surface. A solid coating material made of a thermoplastic resin is melted and press-fitted, and the coating material is adhered to the outer surface of the heated coating steel material while molding the coating material in the gap. This is a method of coating the coating material.
[0011]
The second invention is to install a split mold provided with a heating device in a coating material coating target area on the outer surface of the coated steel material, and after heating the coated steel material, in a gap formed between the outer surface and the split mold inner surface, A method of coating a coating material on a coated steel material, characterized in that a solid coating material made of a thermoplastic resin is press-fitted in a molten state and bonded to an outer surface of a heated coated steel material while being molded in the gap. is there.
[0012]
The third invention and the fourth invention are positioned as a coating device for implementing the first invention or the second invention, and the third invention is a mobile trolley, a coating material storage hopper, A coating material extruder disposed at an outlet of the storage hopper, a coating material heating device attached to the extruder, a split mold having a coating material pressure inlet and a gas vent, and the coating material extruder; A supply hose for connecting a split-type coating material pressure inlet is provided.
[0013]
Further, a fourth invention provides a movable trolley, a coating material storage hopper, a coating material extruder disposed at an outlet of the storage hopper, a coating material heating device attached to the extruder, a coating material pressure inlet, A split mold having a gas vent and a heating device, and a supply hose connecting the coating material extruder and the coating material pressure inlet of the split mold are provided.
A fifth invention is characterized in that, in the third invention or the fourth invention, the split mold has a water cooling structure.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, when a coating material made of a thermoplastic resin such as a polyethylene resin, a polypropylene resin, or a polyamide (nylon) resin is coated on the outer peripheral surface of a coated steel material, for example, a coated steel pipe, a split mold is used. After the coating target area of the steel pipe is heated, the coating material made of a solid thermoplastic resin is softened in a gap corresponding to the coating thickness formed between the outer peripheral surface of the coated steel pipe and the inner surface of the split mold. While press-fitting and molding, it is melted and adhered to the outer peripheral surface of the heated coated steel pipe, and there is concern about oxidation of the steel pipe due to residual air in the coating part of the coating material, decrease in adhesiveness, increase in construction cost , And the coating of the coating material can be easily and accurately realized.
[0015]
INDUSTRIAL APPLICABILITY The present invention can be widely applied as a method for coating the outer surface of a coated steel material with a coating material made of a thermoplastic resin. This method is more suitable as a method for coating a coating material within a narrow range.
[0016]
In the case of joint coating, the method should be applied not only when this joint is obtained by butt welding, but also when the coated steel is joined in a T-shape or when it is joined in an inclined manner. Can be. In this case, the shape and structure of the split mold to be mounted may be considered in accordance with the shape of the joint and its peripheral portion.
[0017]
The split mold is for press-fitting and molding the molten thermoplastic resin into the coated steel material with a predetermined thickness, so that a gap corresponding to the thermoplastic resin coating thickness is formed between the outer surface of the coated steel material and the inner surface of the split mold. A predetermined sealed gap for press-fitting and molding a thermoplastic resin can be formed by fitting and locking the split mold to the outer surface of the coated steel material.
[0018]
As the coating material of the thermoplastic resin used in the present invention, a modified polyethylene resin, a modified polypropylene resin, a modified polyamide (nylon) resin, or the like is suitable, and depending on the type of the coating of the coating steel, the adhesive force ( (Affinity) is sufficient, and the adhesive strength (affinity) to the steel material is selected.
[0019]
It can be said that the coating of the coated steel material and the coating material are preferably the same, but it is not necessary that they be the same. If the coating and the coating material are not the same, the coating of the coated steel material that comes into contact with the coating material may be subjected to primer treatment, roughening, or heat treatment in advance to enhance the adhesive force with the coating material. It is valid.
[0020]
The particle size of the coating material made of such a solid thermoplastic resin is generally in the form of a commercially available pellet and has no problem. This coating material is stored in a storage hopper, and is pressed into the split mold from below the storage hopper by an extruder, an injection molding machine, or the like.
[0021]
In order to sufficiently secure the press-fit density of the coating material and improve the moldability, it is necessary to appropriately melt a solid thermoplastic resin and to secure fluidity. For this purpose, a coating material heating device (reference numeral 4 in FIG. 1) is attached (built-in) to the extruder, and the supply hose has a heat retaining structure in order to prevent a temperature drop during the supply process. It is valid.
[0022]
As the coating material heating device 4 for melting the solid coating material, a heating device that can accurately control a heating temperature that affects the adhesion of the coating material, such as an electric heating device or an induction heating device, is highly suitable. May be.
Further, means for heating the coated steel material in order to prevent a temperature drop of the coating material made of a thermoplastic resin in a molten state pressed into a split mold and maintain fluidity (reference numerals 12 and 12a in FIGS. 3 and 4). As the heating device 12b) , a heating device such as an electric heating device or an induction heating device that can accurately control a heating temperature that affects the adhesiveness of the coating material is highly suitable, but a flame burner may be used.
[0023]
However, in the case of a flame burner, it is effective to use a split annular burner so that the heating temperature distribution by the flame becomes uniform, for example, when covering a coated steel pipe, and it is effective to use a predetermined heating area. It is effective to arrange heat shield plates provided with cooling structures on both sides so as to efficiently heat only the steel sheet and not to hinder the coating of the coated steel pipe.
[0024]
The timing of heating by these heating means is roughly classified into a case where the coating target area of the coated steel material is pre-heated before the split die is mounted on the coated steel material, and a case where the split die is mounted on the coated steel material and then heated. In the former case, any of the above heating means is suitable.
[0025]
In this case, in order to efficiently melt and adhere the thermoplastic resin only to the coated steel material side, heat the coated steel material so that the temperature of the coated steel material side is higher than the temperature of the mold side, and then melt. It is effective to press-fit the thermoplastic resin in the state.
Further, if air or gas remains in the split mold, the formation of a good coating layer is hindered. Therefore, it is preferable to provide a gas vent in the split mold to discharge the air or gas.
[0026]
The inner surface of the split mold is desirably subjected to an adhesion preventing treatment such as chrome plating, Teflon processing, or coating of a release material so that the thermoplastic resin does not adhere. In addition, since the temperature of the split mold rises due to the press-fitting of the coating material in the molten state, the solidification of the coating material coated on the coated steel material is delayed and workability is impaired. Thereafter, it is preferable to provide a cooling structure for supplying a cooling medium, for example, water, for cooling the split mold itself and the coating material.
[0027]
Hereinafter, the present invention will be described with reference to FIGS. 1 to 4 together with an example of a coating apparatus for implementing the present invention. In this example, the coated coated steel pipes Pa and Pb are to be coated, and the coated steel pipes Pa and Pb are heated in advance, and then a split mold is attached to cover the thermoplastic resin as a coating material. Is the case.
[0028]
As shown in FIGS. 1 and 2, a coating apparatus according to the present invention includes a moving truck 1, a coating material storage hopper 2 mounted on the moving vehicle, and a coating material extruder disposed at an outlet of the storage hopper. 3, a heating device 4 attached to the extruder, a split mold 7 having a pressure inlet 5 and a gas vent 6 at the top, and a pressure inlet 5 of the coating material extruder 3 and the split mold 7. And a flexible supply hose 8 having a heat retaining structure.
[0029]
The split mold 7 includes an upper mold 7a and a lower mold 7b. The upper mold 7a and the lower mold 7b can be locked by a locking tool 9. The split mold 7 is provided with gap adjusting rings 10a, 10b made of silicon rubber which also serve as side walls at both end portions. When the split mold 7 is attached to the joined coated steel pipes Pa and Pb, the split mold is formed. A sealed gap A corresponding to the coating thickness of the coating material cp can be formed between the outer surfaces of the coated steel pipes Pa and Pb joined to the inner surface of No. 7.
[0030]
The split mold 7 has a cooling structure. That is, a cooling pipe 18 for circulating cooling water is provided inside the split mold, and the split mold 7 can be cooled by supplying cooling water from a tank 19 by a pump 20 via a supply pipe 21. . The split mold 7 is mounted on a gantry 11 provided on the movable trolley 1 and is manually attached to and detached from the coated steel pipes Pa and Pb.
[0031]
3 and 4 show a structural example of an annular burner as a heating device for heating a welded portion wp of the coated steel pipes Pa and Pb and a peripheral portion thereof.
Reference numeral 12 denotes an annular burner, which is composed of a pair of divided burners 12a and 12b having a large number of flame nozzles fn on an inner peripheral surface. The annular burner 12 has handles 14 on both sides for handling, and is mounted on the gantry 11 provided on the movable trolley 1, and can be manually attached to and detached from the coated steel pipes Pa and Pb.
[0032]
The divided burners 12 a and 12 b constituting the annular burner 12 are connected to gas cylinders 16 mounted on the mobile trolley 1 via gas supply hoses 15, respectively. The annular burner 12 is provided with heat shield plates 17a and 17b at both end portions of the inner surface, and when attached to the coated steel pipes Pa and Pb, prevents the diffusion of the flame f from the flame nozzle fn to achieve thermal efficiency. And the coating c of the coated steel pipes Pa and Pb is not hindered.
[0033]
Using the coating device and the annular burner (heating device) configured as described above, it is possible to cover the welded portion of the coated steel pipe with the coating material made of a thermoplastic resin.
The coating operation is performed in the following procedure.
{Circle around (1)} The coated steel pipes Pa and Pb welded in place are butt-welded and joined, and then this joint wp and its surroundings are sanded to clean the surface (anti-rust treatment if necessary). .
[0034]
(2) The movable trolley 1 is moved to a predetermined position, and the annular burner 12 mounted on the gantry of the movable trolley is mounted so as to cover the butt weld portion wp of the coated steel pipes Pa and Pb and its peripheral portion. These parts are heated by the flame f from the annular burner 12. This heating time is set in advance according to the temperature of the flame f.
[0035]
{Circle around (3)} After heating for a predetermined time, the annular burner 12 is immediately removed from the coated steel pipes Pa and Pb, returned to the gantry 11 of the mobile trolley 1, and the split die 7 placed on the gantry 11 of the mobile gantry immediately is removed. The butt-welded portion wp of the heated coated steel pipes Pa and Pb and its peripheral portion are mounted.
[0036]
{Circle over (4)} The solid thermoplastic resin (coating material) cp is extruded from the storage hopper 2 by the extruder 3 while being heated by the heating device 4 and is melted, and the coating material pressure of the split mold 7 is supplied through the supply hose 8. From the inlet 5, it is press-fitted into a gap A formed between the inner surface of the split mold and the outer surfaces of the coated steel pipes Pa and Pb, and is molded simultaneously.
[0037]
{Circle over (5)} After confirming at the gas vent 6 that the molten thermoplastic resin cp is sufficiently filled in the gap A, the molten thermoplastic resin cp is held for a predetermined time, and the press-fitted and molded thermoplastic resin pc is coated with a coated steel pipe. It is bonded to the butt-weld portion wp of Pa and Pb and its peripheral portion.
[0038]
{Circle around (6)} The split mold 7 is cooled in a state of being mounted on the coated steel pipe to cool the coating material. After the coating material is solidified, the split mold is removed, and the split mold is returned to the gantry 11 of the movable carriage 1.
In this way, the butt weld portion wp of the coated steel pipes Pa and Pb and its peripheral portion can be coated with the thermoplastic resin pc with a predetermined thickness.
[0039]
Note that the present invention is not limited to the contents of the above-described example. For example, the object to be coated can be applied not only to a coated steel pipe but also to a coated shaped steel, a coated steel bar, a coated steel wire, and the like.
In addition, when the coating work position is not fixed, it is preferable that the split die and the heating device for heating the coated steel pipe be mounted on a movable trolley so as to be movable, but it is not essential to mount the movable trolley on the movable trolley. If the workplace is fixed, it may be installed in the coating workplace.
[0040]
Further, the annular burner 12 is used as a heating device for heating the coated steel pipe. However, the heating device may be another device such as an induction heating device, a hot air heating device, a band heater, or may be attached to a split mold.
[0041]
【Example】
Using a coating apparatus and a coating method for a coated steel pipe as shown in FIGS. 1 to 4, a maleic acid-modified polyethylene is coated on a butt weld joint of coated steel pipes 1 a and 1 b having a coating of maleic acid-modified polyethylene. A coating experiment was performed. . The experimental conditions and experimental results will be described below.
[0042]
[Experiment conditions]
(Steel pipe to be coated)
Material: general structural steel, outer diameter: 200 mm, thickness: 5.8 mm
Coating material: Maleic acid-modified polyethylene, coating thickness: 3 mm
(Coating conditions)
Material of coating material: maleic acid-modified polyethylene, particle size: pellet shape (commercial product), coating width: 300 mm, coating thickness: 2.5 mm or more (split mold condition)
Split type gap: 3mm
(Heating and cooling conditions)
Heating device: Annular burner, coated steel tube Heating temperature: 150-200 ° C
Cooling: split type water cooling
As shown in FIG. 5, the appearance of the welded portion of the coated steel pipe and its surroundings obtained in this experiment was slightly large in the surface roughness as shown in FIG. The outer surface was flat and the appearance was good, and no defects that impaired the film properties were observed.
[0044]
In addition, inspection and evaluation of the film formed on the welded portion and its peripheral portion, such as film thickness, peel strength, and presence or absence of air entrapment, were also performed. As a result, the film thickness was 2.7 to 2.9 mm, and there was no problem. The peel strength was 13.0 to 18.0 kg / cm, indicating a sufficient adhesive strength. Regarding the presence / absence of air entrapment, no air remained in the vicinity of the welded portion and also in the overlapping step with the coating c of the coated steel pipe.
[0045]
【The invention's effect】
In the present invention, when the coating material is coated on the outer surface of the coated steel material, the coated steel material is heated, and then the closed gap corresponding to the coating thickness formed between the inner surface of the split mold and the outer peripheral surface of the coated steel material is formed. A molten thermoplastic resin is press-fitted and molded so as to be melted and adhered to the outer surface of the coated steel material. Thereby, it is possible to easily realize the coating of the coated steel material with the coating material without the concern of oxidation of the steel pipe due to residual air in the coating material coating portion, a decrease in adhesiveness, and an increase in construction cost.
[Brief description of the drawings]
FIG. 1 is a schematic side view illustrating an example of the structure of a coating apparatus used to carry out the present invention.
FIG. 2 is a partially cutaway side view conceptual illustration showing an example of mounting the split mold in FIG. 1 to a coated steel pipe.
FIG. 3 is an explanatory side view conceptually showing a structural example of an annular burner as an example of a heating device used in the present invention.
FIG. 4 is a partially cutaway side view conceptual illustration showing an example of mounting the annular burner of FIG. 4 to a coated steel pipe.
FIG. 5 is a partially cut-away side view conceptual diagram showing a coated state of a coated material of a coated steel pipe obtained by an example of the present invention.
FIG. 6 is a partially cutaway side view conceptual illustration showing an example of a conventional method for coating a coated steel pipe with a coating material.
FIG. 7 is a partially cut-away side view conceptual diagram showing a coated state of a coated material of a coated steel pipe obtained by a conventional example.
[Explanation of symbols]
A Closed gap c Coating cp Coating material (thermoplastic resin)
f Flame fn Flame nozzle P Steel pipe Pa, Pb Coated steel pipe wp Welded part 1 Moving trolley 2 Coating material storage hopper 3 Extruder 4 Heating device 5 Coating material pressure inlet 6 Gas vent 7 Split mold 7a Upper mold 7b Lower mold 8 Supply hose 9 Locking tools 10a, 10b Gap adjusting ring 11 Mount 12 Annular burner 12a, 12b Split burner 13 Locking tool 14 Handle 15 Supply hose 16 Gas cylinder 17a, 17b Heat shield plate 18 Cooling pipe 19 Tank 20 Pump 21 Supply pipe

Claims (5)

Heating the coating target area of the coated steel material, mounting the split mold on the outer surface of the coated steel material, and forming a solid material made of thermoplastic resin fat in the gap formed between the outer surface of the coated steel material and the inner surface of the split mold. A method of coating a coated steel material with a coating material, wherein the coating material is press-fitted in a molten state, and the coated material is adhered to an outer surface of a heated coated steel material while being molded in the gap. A split die equipped with a heating device is attached to the coating material coating target area on the outer surface of the coated steel material, and after the coated steel material is heated, a solid resin made of a thermoplastic resin is placed in a gap formed between the outer surface and the split die inner surface. A method of coating a coating material on a coated steel material, wherein the coating material in a molten state is press-fitted in a molten state, and the coating material is adhered to an outer surface of a heated coated steel material while being molded in the gap. A moving trolley, a coating material storage hopper, a coating material extruder disposed at an outlet of the storage hopper, a coating material heating device attached to the extruder, and a gas release port having a coating material pressure inlet. An apparatus for coating a coated steel material with a coating material, comprising: a split die; and a supply hose connecting the coating material extruder and the coating material pressure inlet of the split die. A moving trolley, a coating material storage hopper, a coating material extruder disposed at an outlet of the storage hopper, a coating material heating device attached to the extruder, and a coating material pressure inlet and a gas vent. An apparatus for coating a coated steel material with a split die having a device, and a supply hose connecting the coating material extruder and the coating material pressure inlet of the split die. An apparatus for coating a coated steel material with a coating material, characterized in that the split mold according to claim 3 or 4 has a cooling structure.

Images