JPH0647551A - Circumferential welding method of steel pipe clad with cu-ni alloy - Google Patents

Abstract

PURPOSE:To circumferentially weld steel pipes clad with Cu-Ni alloys to each other on one side from the outer peripheral side. CONSTITUTION:Beads of single layer or plural layers are formed side by using a welding material of the same material as that of the material to be welded having the same compsn. as the compsn. of cladding metals 2 or the compsn. analogous therewith at the time of joining the steel pipes clad with the Cu-Ni alloys as the cladding metals 2 to each other. The beads of the single layer or plural layers are then formed on the upper layer thereof by using an Cu-Ni alloy or Ni-Cr-Mo alloy welding material, by which these steel pipes are circumferentially welded. Then, the steel pipes clad with the Cu-Ni alloys are efficiently joined to each other by one-side welding; in addition, the excellent weldability is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circumferential welding method for Cu-Ni alloy clad steel pipes, which are circumferentially welded to each other from the outer peripheral side on one side.

[0002]

2. Description of the Related Art Since the inner surface of seawater pipes used for transporting seawater is easily corroded by the seawater flowing through the pipes, a method of improving corrosion resistance by coating a plastic has been put into practical use. This seawater pipe is liable to adhere and grow on its inner surface and hinders the smooth flow of seawater.Therefore, we regularly scrape seawater from the inside of the pipe, but during the scraping work, It has been pointed out that the plastic coating is easily scratched and impairs corrosion resistance. In order to deal with such a problem, a clad steel pipe in which a Cu-Ni alloy, which is excellent in corrosion resistance and effectively prevents the adhesion of marine organisms, is clad as a composite material on the inner surface of the pipe instead of the plastic coating has been proposed. There is. When joining the clad steel pipes together, a welding material suitable for the base material and the composite material is prepared, and the base material is fusion-welded from the outer peripheral side to prevent cracking of the welded portion, and then the inner peripheral surface is welded. The mixture is welded by fusion welding from the side.

[0003]

However, the conventional method of welding from both sides has a problem that the work is inefficient and the work is troublesome. Further, there is a problem that it is difficult to perform welding work from the inner peripheral side of a long clad steel pipe or a clad steel pipe having a small diameter, and it is difficult to perform the peripheral welding itself. The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for circumferentially welding a Cu-Ni based alloy clad steel pipe capable of efficiently joining clad steel pipes to each other by single-sided welding from the outer peripheral side. It is what

[0004]

In order to solve the above-mentioned problems, a method for circumferentially welding a Cu-Ni alloy clad steel pipe according to the present invention is used when joining clad steel pipes containing a Cu-Ni alloy alloy as a mixture. Using a common metal welding material having the same or similar composition as the composite material, one or more beads are formed while forming a backside bead from the outer peripheral side, and a Ni-Cu alloy welding material or Ni-Cr is formed on the upper layer. -It is characterized in that a single layer or a plurality of beads are formed by using a Mo alloy welding material, and the beads are circumferentially welded.

The clad steel plate to which the present invention is applied can use a known carbon steel or the like as its base material, and the composite material is a Cu-Ni alloy containing Cu as a main component and Ni as a main component. To be selected. An alloy called Cupronickel (trademark) is used for this Cu-Ni alloy. This cupronickel contains 10 to 30% of Ni, and F
Alloys containing a small amount of e, Mn, Zn, Sn, etc. are in practical use. For example, in the case of JIS standard wire materials, YCuNi-
1 (90Cu-10Ni welding wire) is shown.

[0006] Further, it is desirable that the common metal welding material forming the back bead has the same composition as that of the above-mentioned composite material, but it is also possible to use one having a similar composition.
It is selected so that the bonding between the composite materials is good. The bead using this common metal welding material can be formed in a single layer or a plurality of layers, and can be appropriately selected depending on the plate thickness conditions and the like. The welding method for forming the bead is not particularly limited, but TIG welding or MIG welding, which has good arc directivity and allows work in all postures, is suitable. As a method of supplying the common metal welding material, in addition to supplying it as a welding wire, an insert ring method in which the welding material is formed into a ring shape and this ring is inserted and arranged between the steel pipes to be joined and melted is also possible. is there.

Ni- used for forming the upper layer beads
The Cu alloy welding material is mainly composed of Ni and has Cu as a main component, and an alloy called Monel Metal (trademark) is used. Further, K Monel to which Al is added is also included. Further, instead of the Ni-Cu alloy welding material,
It is also possible to use a Ni-Cr-Mo alloy welding material. This Ni-Cr-Mo alloy includes Inconel (trademark)
A Ni alloy referred to as is used. For example, YNiCrMo-3 is shown for a JIS standard welding wire. The Cu-Ni alloy layer, the Ni-Cu alloy layer or the Ni-Cr alloy
An intermediate layer of pure Ni or the like is preferably formed between the Mo alloy layer and the Mo alloy layer so as to prevent deterioration of weldability due to diffusion of components. Further, it is desirable that the groove of the welded portion has the following shape so that good bondability can be obtained. That is,
It is desirable to set a groove angle of 50 to 100 degrees, a lip thickness of 1 to 3 mm, and a root gap of 0 to 3 mm.

[0008]

In other words, according to the present invention, the mixture of the clad steel pipes is well fused by the beads of the Cu-Ni alloy, and the back bead formed by the root pass of the first layer causes the corrosion resistance of the inner surface of the clad steel pipes and the sea. The effect of preventing organisms from adhering and growing is secured. Ni− formed on the upper layer
The Cu alloy or Ni-Cr-Mo alloy bead fuses the upper part of the lower layer bead, and the base metals are well fused and welded, and the clad steel pipes are well welded as a whole.

[0009]

EXAMPLES Base material 1 and composite material 2 having the components shown in Tables 1 and 2
A clad material 3 having a plate thickness of 11.0 mm (base material side 9 mm, composite material side 2 mm) clad with is prepared, and the groove angle θ is 6
A groove 4 having a degree of 0 degrees, a lip thickness t of 1.5 mm, and a root gap G of 1.5 mm was formed. Also, as a welding material,
The Cu-Ni alloys shown in Table 3 having a similar composition to that of the composite material, and Tables 4 and 5
The Ni-Cu alloy and the Ni-Cr-Mo alloy shown in (4) were prepared, and the clad materials were butt welded by manual TIG welding (DC positive polarity, back shield Ar 20 l / min) under the conditions shown in Table 6. A 2.4 mm diameter welding material was used for the wire, and a common metal welding material having a thickness of 1.5 mm and a width of 3 to 3.5 mm was used for the insert ring 5 as shown in FIG. .

The mechanical properties of the obtained welded clad material (test material) were examined, and the results are shown in Table 7. Further, for comparison, a cupro clad steel sheet (test material No.
A similar test was conducted for 5). In the test method,
In the tensile test, the width including the welded part is 25 mm and the length is 5
A 0 mm test piece was cut out and a tensile load was applied, and the radiation inspection of the welded portion was performed according to JIS Z3104. Furthermore, the corrosion resistance of the welded portion was measured in artificial seawater at 25 ° C. for a flow rate of 2 to 3 m / sec and a period of 30 days.

As is apparent from the table, the test material prepared by the method of the invention was excellent in bending strength of the welded portion, defect inspection and corrosion resistance. On the other hand, in the comparative example using SUS309 stainless steel as the welding material, the bending strength was not sufficient, and the result of the defect inspection of the welded portion was not good either. Next, a 200 mm diameter clad steel pipe is manufactured using the clad material, and the clad steel pipes are welded to each other by the welding method (test material No. 1,
They were joined by circumferential welding in the same manner as 3). The mechanical properties of the obtained peripherally welded clad steel pipe were examined and the results are shown in Table 8. As with the results in Table 7, the welds obtained by the invented method had good properties.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

[Table 3]

[0015]

[Table 4]

[0016]

[Table 5]

[0017]

[Table 6]

[0018]

[Table 7]

[0019]

[Table 8]

[0020]

As described above, the Cu-
According to the circumferential welding method for Ni-based alloy clad steel pipe, Cu-N
When joining clad steel pipes that use i-based alloy as a composite material, a single or multiple bead is formed so that the backside bead is formed from the outer peripheral side by using co-metal with the same or similar composition as the composite material. And Ni-Cu based alloy or Ni-
Since a single layer or a plurality of beads are formed by using a Cr-Mo alloy and circumferential welding is performed, it is possible to perform efficient welding with good weldability by working from one side.

[Brief description of drawings]

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

FIG. 2 is a partial perspective view of an insert ring material used in Examples.

[Explanation of symbols]

 1 Base material 2 Composite material 3 Clad material 4 Groove 5 Insert ring

Claims (2)

[Claims] 1. When joining clad steel pipes made of a Cu-Ni alloy as a composite material, a back metal bead is formed from the outer peripheral side by using a common metal welding material having the same or similar composition as the composite material. Alternatively, a plurality of beads are formed and Ni-Cu is formed on the upper layer.
A method for circumferentially welding a Cu-Ni based alloy clad steel pipe, characterized in that a single layer or a plurality of beads are formed using a system alloy welding material and circumferential welding is performed. 2. When joining clad steel pipes made of a Cu—Ni alloy as a composite material, a common metal welding material having the same or similar composition as that of the composite material is used to form a backside bead from the outer peripheral side. Or, a plurality of beads are formed and Ni-Cr is formed on the upper layer.
-A circumferential welding method for Cu-Ni based alloy clad steel pipe, characterized in that a single layer or a plurality of beads are formed using a Mo based alloy welding material and circumferential welding is performed.