JPS5834203B2 - Yellow-bellied goldenrod - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a welded laminated metal tube.

As is well known, the most common use of large-diameter, thin-walled steel pipes these days is for transportation line pipes, and this trend will only accelerate in the future, with the contents gradually shifting from primary products such as crude oil and gas to secondary products. .

In response to these trends, line pipes are required to have (1) excellent fracture toughness;

(2) Do not cause fraying due to transported objects.

(3) Do not impure the transported object.

(4) Low cost.

etc. can be mentioned.

Conventional methods have attempted to solve these demands as follows.

That is, regarding the fracture toughness (1), the use of laminated steel plates is an example.

Research to date has shown that the fracture toughness of line pipes has two characteristics: brittle fracture characteristics and unstable ductile fracture characteristics.

For the former, the material does not necessarily need to be of good quality as long as the plate thickness is thin, while for the latter, it is necessary that the impact absorption energy at the operating temperature be high.

However, manufacturing methods that increase absorbed energy generally tend to have inferior brittle fracture properties, and it has generally been difficult to achieve both.

For this reason, the steel plates used as the material for steel pipes are laminated in a metallurgically bonded state to improve unstable ductile fracture resistance with steel materials that have high absorption energy, while brittle fracture resistance is compensated for by lamination. becomes possible.

As mentioned above, the meaning of lamination in conventional methods is that either the layers are originally an integrated material, or the outer and inner layers are bonded to each other metallurgically during the processing process. It refers to the state.

In the processing process, the following examples have heretofore been seen as techniques for laminating this type of steel pipe.

1) Explosive molded cladding 2) Rolled cladding method 3) Plastic lining method 4) Metallizing method Or (2) For corrosion resistance, the laminate comes into contact with corroding objects.

This can be compensated for by making the surface a material with strong corrosion resistance, such as stainless steel or a Zn plating layer.
By using commercially available clad steel materials, and in order to avoid impurity of the transported object (3), it is necessary that the metal object does not react with the transported object and produce corrosive substances.

As mentioned above, among the required characteristics (1), (2),
Regarding (3), the objective can be achieved by laminating the materials in a metallurgically bonded state.

However, the most serious problem here is the cost aspect (4).

The above-mentioned generally known laminated materials and means for laminating them in the steel pipe processing process are both expensive and have no marketability for this type of mass use, and have no practical value. It cannot exist at all.

Therefore, the present invention provides a method for manufacturing a laminated metal tube that has excellent fracture toughness and is inexpensive in terms of cost.

A feature of the shape of the laminated metal tube in the present invention is that the entire interface between the outer tube and the inner tube is not fixed together.

In other words, the outer layer and the inner layer are not completely integrated as a laminate.

Furthermore, the most advantageous aspect of the present invention is that this manufacturing method can be carried out on a normal manufacturing line without adding any special manufacturing equipment or complicated steps.

As mentioned above, the basic idea of the present invention is to set the difference between the inner diameter of the outer tube and the outer diameter of the inner tube within a certain range, or to mutually The purpose is to bring the surfaces in contact with each other into close contact due to frictional force.

The concept of the present invention is explained using the stress-strain diagram in Figure 4.
Now, the outer tube is a steel tube with excellent unstable ductile fracture resistance, and curve A
1. The inner tube is a thin-walled steel tube with excellent brittle fracture resistance, and curve B is used.

In this case, the yield point of the outer tube is higher than that of the inner tube.

If the difference between the inner diameter of the outer tube and the outer diameter of the inner tube is set to a gap that will not cause brittle fracture even if the inner tube expands under internal pressure,
If the inner tube expands under internal pressure, it pushes the outer tube apart and deforms plastically to point a in Figure 4.The outer tube remains plastically deformed until that point, but when the internal pressure is no longer applied, the outer tube expands. At points c and c' where the internal stresses of the inner tube and the inner tube balance each other, an equilibrium state is reached with positive residual stress remaining in the outer tube and negative residual stress remaining in the inner tube.

In this way, at least the initial brittle fracture of the inner tube when subjected to internal pressure can be prevented, and even after further internal pressure is applied, the outer tube has excellent unstable ductile fracture resistance and superior laminated structure. As a result, a steel pipe with excellent brittle fracture resistance and excellent overall fracture properties can be obtained.

That is, the present invention provides (1) a method for manufacturing a laminated pipe in which multiple metal pipes are assembled by welding, in which the difference between the outer diameter of the inner pipe and the inner diameter of the outer pipe having an unwelded opening is equal to the outer diameter of the inner pipe; 5
A welded laminated metal characterized by fitting a piece smaller than φ so that the welding position of the outer tube and the welding position of the inner tube are parallel and do not overlap, and then welding the opening to fix the inner tube and the outer tube. In a pipe manufacturing method, (2) a laminated pipe manufacturing method that combines multiple metal pipes formed by welding, the difference between the outer diameter of the inner pipe and the inner diameter of the outer pipe with an unwelded opening is the outer diameter of the inner pipe. After fitting the outer tube so that the welding position of the outer tube and the welding position of the inner tube are parallel so that they do not overlap, the inner tube and the outer tube are fixed by welding the opening, and then the inner tube is fixed. This is a method for producing a welded laminated metal tube, which is characterized by expanding by hydraulic or mechanical methods to bring the inner surface of the outer tube into close contact with the outer surface of the inner tube.

Next, the manufacturing method of the present invention will be explained in detail.

Example of manufacturing double steel pipes with UOE process, 1st
The inner tube 1 and the outer tube 2 are manufactured using the UO process shown in FIGS.

In this case, in order to easily push the inner tube into the outer tube, it is necessary that the inner diameter of the outer tube is slightly larger than the outer diameter of the inner tube.

This needs to be controlled by the board width, 0press die, and Opress UP-set cost.

Of the pipes manufactured using this UOprocess, the seam part 3 of the inner pipe is tacked or permanently welded to fit tightly, the seam part 4 of the outer pipe is left open, and the inner pipe is attached to the outer pipe as shown in Figure 1. Push in like this.

In this case, if necessary, the outer tube may be expanded and the inner tube may be pushed in (the opening of the outer tube is preferably about (0 to 1100) x).

Next, it is necessary to weld the inserted inner tube and outer tube to integrate them.

However, when using a pipe whose inner tube has been permanently welded in advance, it is not necessary to integrate the inner tube and outer tube by welding.

Further, it is preferable to remove the excess buildup on the inner surface bead of the outer tube and the outer surface bead of the inner tube.

If the seams 3' and 4' of the inner and outer pipes match, it will be very difficult to weld, so when welding, weld the two pipes and set the opening lines 3 and 4 at an arbitrary angle to the extent that is comfortable for welding. It is necessary to shift it.

The pipes thus made are integrated by welding them from the inner surface (not necessary if the inner tube has been fully welded in advance) and the outer surface.

In this case, welding should be at least 1/3 of the outer plate thickness if the welds on the inner and outer surfaces are on the inner surface, or 1/3 or more of the inner plate thickness in the case of external welding.
/3 or more is desirable.

In this case, the caps of the inner and outer tubes (Fig. 2) P x 100
) If ΔD is 5 or more, the welded part will break due to stress due to its own weight during transportation of multiple pipes, so it is necessary to keep it within 5.

Furthermore, if the diameter is within 5φ, even if the inner tube expands under internal pressure and undergoes plastic deformation, it will press against the outer tube and exhibit excellent unstable ductile fracture characteristics and brittle fracture characteristics.

However, if an integrated structure is required for strength, as shown in Figure 3, it is possible to expand the pipe from the inner surface in the direction of the arrow by hydraulic pressure or mechanical means in order to make the interface of the laminated pipes integrated by welding stick together. good.

In this case, the gap △D between the inner and outer pipes before expansion is 3%.
If the diameter is not within 3φ, there is a risk that the welded portion will be destroyed during pipe expansion and the properties of the inner surface material will deteriorate, so it is desirable that the diameter be within 3φ.

In this case as well, if the number is within 3, even if the pipe is forcibly expanded, superior fracture characteristics will be exhibited more effectively.

By combining the above methods, if necessary, prepare an outer tube and use the above-mentioned double tube as an inner tube, making it easy to manufacture multiple tubes.

However, in terms of performance, if ΔD is within 5φ, it is sufficient that the inner tube and outer tube are not fixed together by welding.

If you are only concerned with fracture toughness and cost, as shown in the example above, you can manufacture double-walled steel pipes using the UO process or spiral process. The objective can be achieved by using suitable metal tubes while arranging the surfaces.

In the present invention, by the process described above, multiple metal pipes can be manufactured at low cost using the current pipe process.
It is characterized by the fact that it can be manufactured without major changes, and its industrial value has been significantly increased.

Next, implementation of the welded laminated metal pipe of the present invention will be explained.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram of the state in which the inner pipe is pushed into the outer pipe in the laminated pipe manufacturing method, Figure 2 is an explanatory diagram of the state in which the double pipe is integrated only by welding the outer pipe, and Figure 3 is the two-layered pipe. FIG. 4 is a conceptual diagram of a method of welding a heavy pipe from the inner and outer pipes and expanding the pipe from the inner surface to bring the inner and outer pipes into close contact. FIG. 4 is a stress-strain diagram. 1...Inner pipe, 2...Outer pipe, 3...
... Seam part of inner tube, 4... Seam part of outer tube.

Claims (1)

[Scope of Claims] 1. In a method for manufacturing a laminated pipe in which multiple metal pipes are assembled by welding, the difference between the outer diameter of the inner pipe and the inner diameter of the outer pipe having an unwelded opening is the outer diameter of the inner pipe. Welding is characterized in that the inner tube and the outer tube are fixed by fitting the outer tube and the inner tube so that the welding positions of the outer tube and the inner tube are parallel and do not overlap, and then the opening is welded. Manufacturing method for laminated metal tubes. 2 In the manufacturing method of laminated pipes in which multiple metal pipes are assembled by welding, the difference between the outer diameter of the inner pipe and the inner diameter of the outer pipe with an unwelded opening is less than 3 times the outer diameter of the inner pipe. After fitting the outer tube so that the welding positions of the outer tube and the inner tube are parallel and do not overlap, the inner tube and the outer tube are fixed by welding the opening, and the inner tube is further fixed by hydraulic or mechanical 1. A method for producing a welded laminated metal tube, which is characterized by expanding the tube by a method and bringing the inner surface of the outer tube into close contact with the outer surface of the inner tube.