JPH07106456B2 - Method for manufacturing corrosion-resistant layer-coated metal pipe - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a corrosion resistant layer-coated metal pipe.

[Conventional technology]

For example, metal pipes such as centrifugal cast steel pipes are often used for building pillars and the like. The metal pipes such as the centrifugal force cast steel pipes are often used because the metal pipes such as the centrifugal force cast steel pipes are comprehensively excellent in mechanical properties and cost. When a metal pipe such as the centrifugally cast steel pipe is used for a building pillar or the like, its surface is often required to have corrosion resistance. Therefore, conventionally, the centrifugal cast steel pipe is formed by winding a corrosion resistant metal plate such as a stainless steel thin plate around a metal pipe such as the centrifugal cast steel pipe and arc welding the abutting portions of the ends of the corrosion resistant metal plate. The surface of a metal tube such as the above is coated with a corrosion resistant metal.

[Problems to be Solved by the Invention]

On the surface of the metal tube, by using the method as described above, when a coating of corrosion-resistant metal is applied, the abutting portion of the end of the corrosion-resistant metal plate is arc-welded and welded in a welded state. However, the arc weld usually extends to the metal pipe. This is because it is very difficult to match the melting depth by arc welding with the thickness of the corrosion-resistant metal plate.

Therefore, in the arc welded portion, not only is the fusion resistant state between the corrosion resistant metals, but also the fusion resistant state between the corrosion resistant metal and the metal forming the metal pipe. Therefore, there is a problem that an electrochemical reaction occurs between the two metals, and electrolytic corrosion occurs based on the reaction.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of manufacturing a corrosion-resistant layer-coated metal pipe that can avoid the problem of occurrence of electrolytic corrosion.

[Means for Solving the Problems]

A first characteristic configuration of the method for producing a corrosion-resistant layer-coated metal pipe according to the present invention is to wind a corrosion-resistant metal plate around a metal pipe, and fusion weld the abutting portions of the ends of the corrosion-resistant metal plate to form a metal pipe. A method for producing a corrosion-resistant layer-coated metal pipe, the surface of which is coated with a corrosion-resistant metal plate, wherein the surface of the metal pipe corresponds to a butt portion of the corrosion-resistant metal plate, and fusion welding of the butt portion is performed. A concave portion for preventing fusion of the portion to the metal pipe is formed in advance.

In addition, the second method of manufacturing the corrosion-resistant layer-coated metal pipe according to the present invention
The characteristic configuration of the above is that an insert material for preventing fusion bonding of the fusion-welded portion of the butted portion to the metal pipe is previously arranged in the recess.

[Work]

According to the method of the present invention having the first characteristic configuration, it is difficult to match the melting depth of the end surface of the corrosion-resistant metal plate during welding with the thickness of the corrosion-resistant metal plate, and the welded portion is Despite attempting to reach the metal tube, the presence of the recess formed in the metal tube reliably prevents the butt weld of the end of the corrosion-resistant metal plate from being fused to the metal tube. It will be different.

Further, according to the method of the present invention having the second characteristic configuration, due to the presence of the recess formed in the metal pipe and the insert material arranged in the recess, the butt weld portion of the end portion of the corrosion-resistant metal plate is The fusion to the metal tube can be prevented more reliably.

〔The invention's effect〕

As described above, according to the method of the present invention, it is prevented that the butt-welded portion of the end portion of the corrosion-resistant metal plate is fused to the metal pipe, and thus the metal that constitutes the corrosion-resistant metal and the metal pipe. Therefore, the conventional problem that an electrochemical reaction occurs between the two metals and fusion occurs between them and electrolytic corrosion occurs based on the reaction is avoided.

〔Example〕

Hereinafter, a method of manufacturing a corrosion-resistant layer-coated metal pipe according to the present invention will be described with reference to the drawings.

1 (A), (B), (C), (D), (E),
(F) is a schematic explanatory view showing an example of all steps of the method of the present invention in the order of steps.

As shown in FIG. 1 (A), a centrifugal cast steel pipe (1) as an example of a metal pipe, and stainless steel as an example of a corrosion-resistant metal plate to be coated on the outer peripheral surface of the centrifugal cast steel pipe (1) First, the steel plate (2) is prepared. The centrifugal cast steel pipe (1) is subjected to shot blasting to remove scale from the surface of the centrifugal cast steel pipe (1).

Next, the stainless steel plate (2) is bent and wound around the centrifugal cast steel pipe (1), and in the wound state, a portion where the end faces of the stainless steel plate (2) face each other, that is, a butted portion. (21) was TIG welded (tungsten inert gas arc welding), so that the centrifugal cast steel pipe (1) was made of stainless steel as shown in FIGS. 1 (B) and 2 (C) (both figures show the same process). A raw material (4) of a two-layer metal combination (3) arranged so as to be covered with a steel plate (2) is obtained.

TIG the abutting part (21) of the stainless steel plate (2)
When welding, the butted portion (2) of the stainless steel plate (2) on the surface of the centrifugal cast steel pipe (1)
As shown in FIG. 2, a recess (11) for preventing fusion of the fusion-welded portion of the butting portion (21) to the centrifugal cast steel pipe (1) is previously formed at a location corresponding to 1). I'll do it. And the abutting part (21) of the stainless steel plate (2)
When TIG welding is performed, the stainless steel plate (2) is formed due to the presence of the recess (11) formed in the centrifugal cast steel pipe (1).
It is possible to reliably prevent the welded portion of the butted portion (21) from being fused to the centrifugal force cast steel pipe (1).

Also, the abutting part (21) of the stainless steel plate (2)
As shown in FIG. 2, a gap (S) is formed partially depending on the dimensional accuracy of the centrifugal cast steel pipe (1) and the abutting end faces do not contact each other. Therefore, the gap (S) is formed. ), Insert material for gap filling to fill it (7)
Is placed. The material of the insert material (7) is determined in consideration of the weldability of the abutting portion (21) during welding.

Next, the material (4) of the two-layer metal combination (3) is placed in a vacuum chamber of an electron beam welding machine, and both edges (4a) of the material (4) are melted into a vacuum to be deeply melted. Circumferential electron beam welding is performed under such a condition that the depth reaches the centrifugal force cast steel pipe (1). As a result, the gap between the centrifugal cast steel pipe (1) and the stainless steel plate (2) is sealed under reduced pressure, and both (1) and (2) are as shown in FIG. 1 (D). A two-layer metal combination (3) is obtained which is integrated via the electron beam weld (3a).

Next, the two-layer metal combination (3) is subjected to hot hydrostatic pressure treatment using a hot hydrostatic compression treatment device. Specifically, hot isostatic pressing was performed on the two-layer metal combination (3) under the conditions of treatment temperature: 1200 ° C., treatment pressure: 1000 kg / cm ² , atmosphere gas: argon gas, treatment time: 2 hr. Apply processing. As a result, as shown in FIG. 1 (E), the two-layer metal combination (3) is compressed, and the stainless steel plate (2) is heated along the surface shape of the centrifugal cast steel pipe (1). A hydrostatic compression-treated product (5) is obtained. The treatment temperature of the hot isostatic pressing treatment was 1200 ° C. in the above example, but the hot isostatic pressing product (5) can be effectively obtained even when the treatment temperature is 930 ° C. When the centrifugal cast steel pipe (1) is carbon steel, the cast steel pipe (1) after cooling the cast steel is heated to 930 ° C., held for a predetermined time, and then air-cooled to perform a heat treatment to obtain a predetermined strength. This heat treatment is performed by applying the hot isostatic pressing treatment at 930 ° C.
It is possible to omit the processing by performing the combined processing by processing in.

Next, the existing portion of the electron beam welded portion (3a) in the hot isostatically pressed product (5) is cut and removed to obtain a corrosion resistant layer-coated metal pipe (6) as shown in FIG. 1 (F). obtain.

The thus-obtained corrosion-resistant layer-coated metal pipe (6) is in a state where the surface thereof is coated with the stainless steel plate (2), and the corrosion resistance, fire resistance and durability of the surface are secured.
Moreover, the portion of the stainless steel plate (2) of the corrosion-resistant layer-coated metal pipe (6) is deformed along the surface shape of the portion of the centrifugal cast steel pipe (1), and the original centrifugal cast steel is formed on the surface. Irregularities that are affected by the irregularities of the casting surface of the pipe (1) are formed, so that the surface thereof also has a design characteristic peculiar to the casting.

[Another embodiment]

As shown in FIG. 3, an insert material (9) for preventing fusion of the welded portion of the butted portion (21) to the centrifugal cast steel pipe (1) is previously arranged in the recess (11). It is better to keep it. This is because the presence of the insert material (9) more reliably prevents the welded portion at the end of the stainless steel plate (2) from being fused to the centrifugal cast steel pipe (1).

Further, as shown in FIG. 4, the function of the insert material (9) for preventing fusion of the welded portion of the butted portion (21) to the centrifugal cast steel pipe (1), and the gap filling insert. Insert material (8) having the function of material (7)
It is also conceivable that the embodiment is arranged so as to extend over the gap (S) and the recess (11).

In addition, bending the stainless steel plate (2) and winding it around the centrifugal cast steel pipe (1), and TIG welding the abutting portion (21) of the stainless steel plate (2) in the wound state. The present invention can be applied even when the combination itself obtained by the method is a metal tube covered with a corrosion resistant layer which is the object of the method of the present invention.

It should be noted that although reference numerals are added to the claims for convenience of comparison with the drawings, the method of the present invention is not limited to the method shown in the accompanying drawings.

[Brief description of drawings]

1 (A), (B), (C), (D), (E),
(F) is a schematic explanatory view showing all steps of the method of the present invention in the order of steps, FIG. 2 is a perspective view showing the main steps, and FIGS. 3 and 4 are the main steps of another embodiment of the method of the present invention. FIG. (1) …… Metal tube, (11) …… Recessed part, (2) …… Corrosion resistant metal plate, (21) …… Butt part, (3) …… Insert material.

Claims (2)

[Claims] 1. A metal pipe (1) is obtained by winding a corrosion-resistant metal plate (2) around a metal pipe (1) and fusion-welding an abutting portion (21) at an end of the corrosion-resistant metal plate (2). ) Is coated with a corrosion-resistant metal plate (2), the method for producing a corrosion-resistant layer-coated metal pipe, comprising a butting portion (21) of the corrosion-resistant metal plate (2) on the surface of the metal pipe (1). ), A recess (11) for preventing fusion of the fusion-welded part of the butting part (21) to the metal pipe (1) is formed in advance. . 2. The butting part (2) is provided in the recess (11).
The method for producing a corrosion-resistant layer-covered metal pipe according to claim 1, wherein an insert material (9) for preventing fusion of the fusion-welded portion of 1) to the metal pipe (1) is arranged in advance.