JP3106315B1 - Hot-dip metal plating method for steel pipe outer surface and plug device used in the method - Google Patents

Abstract

The present invention relates to a plating method in which both ends of a steel pipe are plugged and immersed in a plating bath. Provided is a method for plating a molten metal on the outer surface of a steel pipe, which can be manufactured by an ordinary continuous manufacturing apparatus for metal-plated steel pipes using a plug device that is immersed without being forcedly pushed in. SOLUTION: A core having a length corresponding to the length of a steel pipe to be plated is penetrated into the steel pipe, and a plug having an insertion hole from each end side of the steel pipe to the core is inserted into the core. Then, after closing the end of the steel pipe, the steel pipe is immersed in a molten metal plating bath and plated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for plating a molten metal on the outer surface of a steel pipe and a stopper device used in the method. The present invention relates to a method for applying metal plating and a stopper device used for the method.

[0002]

2. Description of the Related Art In hot-dip galvanizing of steel pipes, for example, hot-dip galvanizing, there are cases where plating is applied to both inside and outside surfaces of a steel pipe, where only inside surfaces are plated, and where only outside surfaces are plated. In this case, the present invention relates to a case where plating is performed only on the outer surface of the steel pipe.

Conventionally, a method of plating only the outer surface of a steel pipe, for example, hot-dip galvanizing, is as follows: (1) A molten metal adhesion preventing material (anti-plating material) for preventing plating is applied to the inner surface of the steel pipe, and the molten steel is placed in a molten zinc bath. (2) A method in which a steel pipe is continuously moved to a molten zinc bath through a joint on the inlet side of a bath molten zinc bath via a joint, and plated using a dedicated apparatus for external plating that removes the joint on an outlet side. (3) There is a method in which both ends of a steel pipe are plugged so that hot-dip zinc (hot-dip metal) does not enter the steel pipe and is immersed in a hot-dip zinc bath (hot-dip metal bath).

[0004]

The above-mentioned (1) method of plating by coating an inner surface of a steel pipe with an anti-plating material involves applying an anti-plating material to the inner surface of the steel pipe and removing the anti-plating material after plating. In addition, there are problems such as troublesome and time-consuming and poor productivity. The method of plating with the dedicated apparatus for outer surface plating of the above (2) is as follows:
There is a disadvantage that the equipment cost is high. In particular, the equipment only for external plating cannot be used for other general steel pipe galvanizing,
Other equipment for galvanizing steel pipes is required in addition to a dedicated apparatus for external surface plating, so that both initial cost and running cost are higher, and the cost is higher as a whole.

The method of (3) plating by plugging both ends of a steel pipe and immersing it in a plating bath is effective because it can be plated by a general galvanized steel pipe continuous manufacturing apparatus. There are such disadvantages. (A) In the conventional stopper, since the inside of the steel pipe is empty, the air in the steel pipe may expand and the stopper may come off. (B) Since the inside of the steel pipe is empty, large buoyancy is generated in the steel pipe (due to the specific gravity of molten zinc of about 7.1), and the steel pipe floats in the plating bath, so that transport troubles easily occur, and the steel pipe is forcibly pushed into the bath. Otherwise, the device cannot be immersed, so a device for forcibly pushing it into the bath is required.

The present invention has been proposed in order to solve the above-mentioned drawbacks in a plating method in which both ends of a steel pipe are plugged and immersed in a plating bath. Even if the volume is small and the air expands, the plug does not come off, the buoyancy is small and the weight is applied to the steel pipe, so only the outer surface of the steel pipe is immersed using a plug device that does not need to be forced into the plating bath. An object of the present invention is to provide a method for hot-dip metal plating and a stopper device used for the method.

In the present invention, a core is used. The core may be broken due to a difference in thermal expansion elongation due to a temperature difference between the steel pipe to be plated and the core. In view of this point, the present invention provides a method of hot-dip metal plating only the outer surface of a steel pipe in which the core is not broken due to a difference in thermal expansion elongation due to a temperature difference between a steel pipe to be plated and a core, and a plug used in the method. It is a second object to provide a device.

[0008]

According to a first aspect of the present invention, there is provided a method for plating a molten metal on an outer surface of a steel pipe, the hollow having open ends at a length corresponding to the length of a steel pipe to be plated. The core constituted by the body penetrates into the steel pipe, and a plug having an insertion hole to be inserted into the core from each end side of the steel pipe is inserted into the core, and the end of the steel pipe is inserted. After closing, the steel pipe is immersed in a molten metal plating bath to perform plating.

According to a second aspect of the present invention, there is provided a method for plating a molten metal on the outer surface of a steel pipe, wherein the plug closing an end of the steel pipe is temporarily welded to the steel pipe and the core. And

According to a third aspect of the present invention, there is provided a method for plating a molten metal on the outer surface of a steel pipe, wherein the method comprises forming a hollow body having both ends open, and having a thread corresponding to the length of the steel pipe to be plated at both ends. The core of the steel pipe penetrates into the steel pipe, and a plug having a threaded insertion hole on the inner surface is screwed into the core from each end side and inserted into the core to close the end of the steel pipe. After that, the steel pipe is immersed in a molten metal plating bath for plating.

Further, in the method for plating a molten metal on the outer surface of a steel pipe according to a fourth aspect of the present invention, the steel pipe to be plated or the core has a difference in thermal expansion elongation due to a temperature difference between the steel pipe to be plated and the core. It is characterized in that a stretch absorbing means for absorbing is provided.

Further, the plug device used in the method for plating a molten metal on the outer surface of a steel pipe according to claim 5 of the present invention is a hollow body having both ends opened with a length corresponding to the length of the steel pipe to be plated penetrating into the steel pipe. And a core having an insertion hole to be inserted into the core, which is removably inserted from both ends of the steel pipe into the core penetrated into the steel pipe, and closes the end of the steel pipe. And a stopper body.

The plug device used in the method for plating a molten metal on the outer surface of a steel pipe according to claim 6 of the present invention is a hollow body having both ends opened with a length corresponding to the length of a steel pipe to be plated penetrating into the steel pipe. And a core having an insertion hole to be inserted into the core, which is removably inserted from both ends of the steel pipe into the core penetrated into the steel pipe, and closes the end of the steel pipe. And an expansion / contraction absorbing means provided on the steel pipe or core to be plated, for absorbing a difference in thermal expansion and elongation caused by a temperature difference between the steel pipe to be plated and the core.

Further, plug device for use in molten metal plating method of the steel pipe outer surface according to claim 7 of the present invention, is threaded at both ends periphery of the core, screw off the insertion hole inner surface of the plug body The plug is screwed into and inserted into the core.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing an embodiment of the present invention, FIG. 2 is a partial cross-sectional view showing an embodiment of the present invention, and FIG. 3 is a cross-sectional view of a stopper device showing the embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a steel pipe to be plated (hereinafter referred to as a steel pipe).
Reference numeral 2 denotes a plug device including a plug 3 and a core 4.

The plug 3 is formed of a cylindrical small-diameter portion 3a and a flange-shaped large-diameter portion 3b. An insertion hole 5 into the core 4 penetrates the center, and a screw 6 is formed on the inner surface of the insertion hole 5. Is cut off. When the plug 3 is inserted into the steel pipe 1 from the end opening of the steel pipe 1 by inserting the small cylindrical part 3a into a flange-shaped large diameter part 3b.
Abuts on the end face of the steel pipe 1 to close the opening of the steel pipe 1. Therefore, as shown in FIG. 2, the outer diameter D ₃ of the flange-shaped large-diameter portion 3 b is substantially equal to the outer diameter D ₁ of the steel pipe 1, and the outer diameter d ₃ of the cylindrical small-diameter portion 3 a is equal to the inner diameter of the steel pipe 1. preferably slightly higher than d ₁ smaller.

The core 4 has a long cylindrical shape, and screws 7 corresponding to the screws 6 of the plug 3 are cut on the outer periphery of both ends. As shown in FIG. 3, the insertion hole 5 of the plug 3 is screwed into and inserted into the core 4 at both ends. This core 4
Is inserted into the steel pipe 1 and, as shown in FIG. 1, the plugs 3 inserted into the openings at both ends of the steel pipe 1 are screwed and attached. However, when immersing in a molten metal plating bath in the state shown in FIG. 1 to perform plating, a hollow cylindrical shape is preferable because a plating solution can enter and buoyancy is reduced.

Thus, the cylindrical small-diameter portion 3b is inserted into the steel pipe 1 from the end opening of the steel pipe 1, and the flange-shaped large-diameter portion 3b contacts the end face of the steel pipe 1 to close the opening of the steel pipe 1. The plug 3 is fixed by screwing the screw 6 of the insertion hole 5 of the plug 3 into the screw 7 cut at both ends of the core 4 located in the steel pipe 1 (the state of FIG. 1). The steel tube 1 whose both ends are closed by the plug 3 is immersed and plated in a molten metal plating bath. By doing so, the outer surface of the steel pipe 1 is plated,
Since the inner surface is sealed by the core 4 and the plug 3, it is not plated. After the plating process, if the plug 3 and the core 4 are removed, a steel pipe with an external metal plating is obtained. And at this time, screw 6
And 7 are hot-dip metal plating even if plated
It can be reused for use, and if the plating is screw 6 and
7 can be regenerated by heating and melting
You. Similarly, the plug 3 and the core 4 can be reused .

Further, since the steel pipe 1 is filled with a core 4 and the like, and a plating solution also enters the hollow core 4, the buoyancy is small.
Since it does not float in the plating bath, forcibly push it into the bath
It is not necessary, and there is no transportation trouble in the plating bath. Further, since the openings at both ends of the steel pipe 1 are sealed with the plugs 3 and the buoyancy is small and there is no transportation trouble, a conventional metal-plated steel pipe in which every several steel pipes are immersed in a molten metal plating solution and pulled up by a transport device. An external metal-plated steel pipe can also be manufactured with a continuous manufacturing apparatus.

FIG. 4 is a sectional view showing another embodiment of the present invention. In this embodiment, when the plug 3 is disc-shaped, and when the core 4 is inserted into the steel pipe 1 longer than the steel pipe 1, both ends of the plug 3 come out of the steel pipe 1, and the plug 3
The screw 6 of the insertion hole of the plug 3 is screwed and attached to seal the openings at both ends of the steel pipe 1, and the other parts are the same as those of the above-described embodiment. According to the present embodiment, since the plug 3 is only disk-shaped, there is no trouble to form the cylindrical small-diameter portion 3a and the flange-shaped large-diameter portion 3b as in the above embodiment, Manufacturing becomes easy.

FIG. 5 is a sectional view showing still another embodiment of the present invention. In this embodiment, there is no screw in the outer periphery of both ends of the insertion hole 5 and the core 4 of the disc-shaped plug 3 in the example of FIG. The plug 3 is temporarily welded 8 between the steel pipe 1 and the core 4 and fixed, and the other components are the same as those in the above embodiment.

FIGS. 6 and 7 are cross-sectional views showing modifications of the embodiment shown in FIGS. In this modification, the outer diameter (d ₃ in FIG. 2) of the small-diameter portion 3b is different from the case where a commercially available socket or the like is used as the plug 3, for example.
In the case where the diameter of the steel pipe 1 is considerably smaller than the inner diameter (d _{1 in} FIG. 2), a gap is formed and the core is easily shifted without adhesion, this is an example in which the stabilizer 9 is inserted into the small diameter portion 3a to prevent the core from shifting. Since this embodiment is the same as the embodiment shown in FIGS. 1 to 3, the same reference numerals are given and the details are omitted.

Further, in the method for plating molten metal on the outer surface of a steel pipe according to the present invention and the plug device used in the method, the difference in thermal expansion elongation due to the temperature difference between the steel pipe 1 to be plated and the core 4 is described. As a result, the core 4 may be broken. When the core 4 is hollow and the molten metal plating solution can penetrate into it, no temperature difference occurs, but when the core 4 is a solid body, a temperature difference occurs, and the possibility of breakage increases particularly. .

Therefore, the steel pipe 1 or the core 4 to be plated is
It is preferable to provide expansion / contraction absorbing means for absorbing a difference in thermal expansion / elongation due to a temperature difference between the steel pipe 1 to be plated and the core. FIG.
9 is a cross-sectional view in the case where the expansion and contraction absorbing means 12 according to the embodiment of the present invention is provided. FIG. 8 shows a case where the core 4 is divided and a spring 10 is interposed between the core 4a and the core 4b as expansion / contraction means 12, and FIG. 9 shows a state where the plug 3 and the steel pipe 1 to be plated are interposed. Spring 1 as expansion / contraction absorbing means 12
1 and the disc spring 11 make close contact with each other.
This is a case where self-sealing is performed , and the other components are the same as those in the above-described embodiment. In particular, in the case of FIG.
3 is fastened to one of the cores 4a or 4b.
4. A tension is generated on the whole, and the two plugs 3, 3
It is preferable to make it adhere to both ends of 1 .

In the embodiment shown in FIG. 8, the difference in the amount of thermal expansion and elongation due to the temperature difference between the steel pipe 1 to be plated and the core is absorbed by the spring 10. That is, the amount of elongation of the steel pipe 1 to be plated is absorbed by the spring 10 and does not affect the core 4. In the present example, the spring 10 serves to press the plug 3 against the end face of the steel pipe 1 to be plated, and thus also functions to ensure the sealing performance.

Further, in the embodiment shown in FIG.
The difference in the amount of thermal expansion and expansion due to the temperature difference between the steel pipe 1 to be plated and the core 4 is absorbed by the disc spring 11. That is, the amount of elongation of the steel pipe 1 to be plated is absorbed by the disc spring 11 and does not affect the core 4. In addition, in this example, the disc spring 11 also functions to secure the sealing property by being pressed against the end face of the steel pipe 1 to be plated by itself.

The present invention is not limited to the above embodiment, and the core and the plug need only have a structure that seals the end of the steel pipe. Also, a plug body that matches the steel pipe to be plated,
Of course, you can choose a core. Also, the expansion / contraction absorbing means may be made of a material which can expand and contract the core, or may have a structure.

[0029]

As described in detail above, according to the present invention, the openings at both ends of the steel pipe are sealed with plugs, the buoyancy is small and the mesh is small.
Because it does not float in the bath, it is necessary to force it into the bath
No need for transport trouble. In addition, the outer surface metal-plated steel pipe can be manufactured by a conventional metal-plated steel pipe continuous manufacturing apparatus in which every several steel pipes are continuously immersed in a molten metal plating solution and pulled up by a transfer device. Also, if you select a plug and a core that match the steel pipe to be plated,
It can handle a wide range of external plating of steel pipes regardless of the type and diameter of the steel pipes. By the way, in the case of the SGP steel pipe of 20A to 100A, it was very good. Further, according to the plug device of the present invention, the amount of air in the steel pipe is small because of the core, so the amount of expansion of the air is also small, and since the plug does not come off, the plug does not come off even if the air expands. . Also, by selecting the core, the weight of the steel pipe to be plated can be adjusted. Moreover, the core and the plug can be used repeatedly. Furthermore, since the expansion and contraction absorbing means is provided, the difference in the amount of thermal expansion and elongation due to the temperature difference between the steel pipe to be plated and the core is absorbed,
The core does not break.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a partial sectional view showing an embodiment of the present invention.

FIG. 3 is a cross-sectional view of the stopper device showing the embodiment of the present invention.

FIG. 4 is a cross-sectional view showing another embodiment of the present invention.

FIG. 5 is a sectional view showing still another embodiment of the present invention.

FIG. 6 is a sectional view showing a modification of the present invention.

7 is a cross-sectional view of the plug device of the modification shown in FIG.

FIG. 8 is a cross-sectional view in the case where the expansion and contraction absorbing means according to the embodiment of the present invention is provided.

FIG. 9 is a cross-sectional view of another embodiment of the present invention in which another expansion / contraction absorbing means is provided.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 plated steel pipe (steel pipe) 2 stopper device 3 stopper 4 core 5 insertion hole 6, 7 screw 8 temporary welding 9 stabilizer 10 spring as expansion and contraction means 11 disc spring as expansion and contraction absorption means 12 expansion and contraction absorption means

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yutaka Hirano 1-1-1 Kawasaki-cho, Handa-shi, Aichi Prefecture Kawatetsu Tuvic Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 2 / 00-2/38

Claims (7)

(57) [Claims] 1. A core comprising a hollow body having a length corresponding to the length of a steel pipe to be plated and having both ends opened, penetrates into the steel pipe,
Insert the steel pipe into the core from each end side of the steel pipe
A molten metal plating method for an outer surface of a steel pipe, which comprises inserting a plug having an insertion hole to close an end of the steel pipe, and then dipping the steel pipe in a molten metal plating bath to perform plating. 2. The method for plating molten metal on the outer surface of a steel pipe according to claim 1, wherein the plug closing the end of the steel pipe is temporarily welded between the steel pipe and a core. 3. A core having a length corresponding to the length of a steel pipe to be plated, which is formed of a hollow body having both ends opened and threaded at both ends, is penetrated into the steel pipe. After plugging and inserting a plug having a threaded insertion hole on the inner surface from each end side to close the end of the steel pipe, this steel pipe is immersed in molten metal plating and plated. A molten metal plating method for an outer surface of a steel pipe, characterized in that: 4. The steel pipe or core to be plated is provided with expansion / contraction means for absorbing a difference in thermal expansion and elongation due to a temperature difference between the steel pipe to be plated and the core. 4. The method for hot-dip plating of an outer surface of a steel pipe according to 1, 2, or 3. 5. A core comprising a hollow body having a length corresponding to the length of a steel pipe to be plated penetrating into the steel pipe and having both ends opened, and an insertion hole inserted into the core. A plug device used for a method of plating molten metal on the outer surface of a steel pipe, comprising: a plug which is detachably inserted into the penetrated core from both ends of the steel pipe and closes an end of the steel pipe. 6. A core having a length corresponding to the length of a steel pipe to be plated that penetrates into a steel pipe, and a core having an insertion hole for the core and penetrating into the steel pipe is provided at both ends of the steel pipe. A plug that is removably inserted from and closes the end of the steel pipe, and a difference in thermal expansion elongation due to a temperature difference between the steel pipe to be plated and the core, which is provided in the steel pipe to be plated or the core, is absorbed. A stopper device for use in a method for plating a molten metal on the outer surface of a steel pipe, comprising a stretch absorbing means. 7. The core is threaded at the outer periphery of both ends, the plug is threaded inside the insertion hole of the plug, and the plug is screwed and inserted into the core. Item 7. A stopper device used in the method for plating a molten metal on the outer surface of a steel pipe according to item 5 or 6.