JPH0655354B2 - Low dilution multi-electrode submerged arc welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to high alloys such as stainless steel, Ni, Ni alloys, Cu and Cu alloys, and non-ferrous metals with materials having a large Fe content such as carbon steel and low alloy steel. Welded in coexistence, high alloy,
The present invention relates to a multi-electrode submerged arc welding method effective for preventing the non-ferrous metal weld metal from being diluted by the Fe component, and more particularly to a method for low dilution welding a high alloy onto carbon steel.

[Conventional technology]

When welding a laminated material of clad steel in which high alloy is layered on carbon steel as overlay material, or when high alloy or non-ferrous metal is overlay welded to carbon steel, high alloy, non-ferrous metal is a base metal with a large Fe content It is important to prevent being diluted by.
When this dilution occurs in the welding of high alloy and non-ferrous metals, components that contribute to the corrosion resistance in the weld metal, such as Cr, Ni, M
The respective components such as o and Cu are insufficient, and the desired corrosion resistance cannot be obtained.

In order to suppress the dilution of the weld metal by the base metal, it is effective to limit the welding heat input and suppress the melting of the base metal, and suitable welding methods for this are gas shielded arc welding methods such as MIG and TIG. It is well known.

However, since this type of welding method has a low heat input, it is basically inefficient. The welding method which is excellent in efficiency is the submerged arc welding method.

The submerged arc welding method has high efficiency and the quality of the welded portion is stable, and the welding efficiency is further improved by adopting multi-electrode welding of two or more electrodes.

However, this welding method essentially causes remarkable melting of the base metal as compared with gas shielded arc welding methods such as MIG and TIG. Therefore, when the above-mentioned dilution of the weld metal by the base metal becomes a problem, a special welding method as disclosed in JP-B-59-48705 and JP-A-62-45480 is required.

The former is a method of performing welding with a single electrode while limiting the welding current to 100 to 350 A by using a thin wire of 0.8 to 2.0 mmφ and a pulse arc power source, and the latter is a method of welding with two electrodes and a predetermined electrode for both electrodes. Is a method of welding with a large diameter cored wire of 4.0 mmφ or more.

[Problems to be Solved by the Invention]

However, the former method uses a single electrode, and since it severely limits the welding current, it has a low efficiency despite the submerged arc welding.

The latter method uses two electrodes and does not require any extreme limitation on the welding current. Therefore, it is excellent in efficiency. However, since it is a stringer bead, the range of groove design is limited. Further, in any of the methods, it is necessary to limit the welding material such as wire.

In general, limiting welding materials, groove design, welding conditions, etc. means separation from ideal conditions, which not only reduces welding efficiency but also complicates work and strict condition management. Then, in many cases, there is a practical disadvantage.

In view of such a situation, the present invention is a submerged arc capable of highly efficient low-dilution welding of a high alloy on a carbon steel without adding practically disadvantageous restrictions to the welding material, groove design, welding conditions, etc. It provides a welding method.

[Means for Solving the Problems]

In order to achieve this object, the present inventors examined the weaving of electrodes in the multi-electrode submerged arc welding method. As a result, they have found that it is effective to weave only the leading electrode at a right angle to the welding direction and fix the second and subsequent electrodes for welding.

That is, the weaving of the leading electrode in the multi-electrode submerged arc welding method has the effect of reducing the penetration depth and suppressing the dilution of the weld metal by the base metal.

When the leading electrode is fixed, such an effect cannot be obtained even when weaving the second and subsequent electrodes. This is because the penetration depth is determined only by the welding conditions of the leading electrode when the welding current after the second electrode is set to the same level as or lower than that of the leading electrode.

Even when weaving multiple electrodes including the leading electrode,
Only the same effect as in the case of weaving only the leading electrode can be obtained. This is because the weaving after the second electrode does not substantially contribute to the low dilution as described above.

Weaving only the leading electrode does not substantially reduce the welding efficiency, but when weaving multiple electrodes including the leading electrode, the welding efficiency is reduced and the welding equipment is complicated and large, for example, the inner surface of a steel pipe. Makes it difficult to use in a narrow space such as.

In short, weaving only the leading electrode effectively suppresses the dilution of the weld metal by the base metal, does not require any other particularly severe restrictions, and has a multi-electrode system for welding efficiency. The advantage of is followed as it is.

Since the present invention has been made based on such knowledge, when welding a high alloy on a base material made of carbon steel by a multi-electrode submerged arc welding method, weaving only the preceding electrode at right angles to the welding direction, and , Its weaving width is 10
The gist is a low-dilution multi-electrode sub-aged arc welding method, which is characterized by setting the thickness to -30 mm and suppressing the dilution of the weld metal by the base metal.

[Work]

In the welding method of the present invention, the multi-electrode submerged arc welding of two or more electrodes is adopted because the single electrode is insufficient in efficiency even if the welding conditions are improved, and for example, when the clad steel pipe is manufactured by the UOE method, the inner surface bonding material is used. This is because it causes a problem that it cannot be applied to welding.

The reason why the leading electrode is weaved is that the weaving of the leading electrode is dominant with respect to the effect of the low dilution, as described above. Another major reason is that weaving of only the leading electrode does not hinder the efficiency improvement of the multiple electrodes.

The distance between the electrodes, the weaving width and the number of times may be appropriately determined mainly from the viewpoint of welding stability such as arc stability and slag entrainment, and there is no particular limitation except for the weaving width that also affects dilution. These conditions will be described below.

○ If the distance between the electrodes is less than 10 mm, the leading and trailing arcs are too close to each other, and the arcs become unstable due to mutual interference. On the other hand, if it exceeds 30 mm, the arc will be separated too much, and slag entrainment will easily occur. Further, the molten pool is also separated, and it becomes difficult to obtain a good bead appearance. Therefore 10-30mm
Is preferred.

○ If the weaving width is less than 10 mm, the penetration depth reduction effect by weaving is insufficient, and the dilution of the weld metal by the base metal may increase. On the other hand, when it exceeds 30 mm, the arc is separated and the slag is apt to be caught. In addition, separation of the molten pool also occurs, making it difficult to obtain good beads. Therefore, the weaving width is limited to 10 to 30 mm.

○ Weaving frequency Adjusted appropriately according to the welding speed. Since the welding speed is greatly influenced by the number of electrodes, the following parameter Pw, which is proportional to the welding speed ν, is 5 when the case of two electrodes is described.
If it exceeds 0, the number of weaving times C with respect to the welding speed ν
If w is too small, unevenness at the toe of the bead and welding defects, particularly undercut, are likely to occur, and the bead appearance is also deteriorated. On the other hand, when Pw is less than -50, the number of times of weaving Cw becomes excessive with respect to the welding speed ν, and slag entrainment easily occurs. Therefore, −50 ≦ Pw ≦ 50 is preferable.

Pw = 0.2 × ν-Cw Cw: Number of weaving times (times / minute) ν: Welding speed (mm / minute) Also under other conditions, extreme restrictions are not required, applicable materials, target dilution ratio values, etc. It will be decided according to
There is no particular limitation.

For reference, in order to secure the performance of the welded portion, the material that must limit the dilution rate from the base metal to the welded metal to 20% or less, specifically, 20Cr-40Ni-based Incoloy 825, Fe component, etc. The preferred conditions for materials that require a strict limit of are described below.

○ Number of electrodes Since a single electrode lacks efficiency as described above, multiple electrodes are required. However, since a high speed condition is obtained when three or more electrodes are used, the bead appearance may be deteriorated by the normally used bond flux. Therefore two electrodes are most preferred.

○ Welding current When both the leading electrode and the trailing electrode are less than 300 A, the amount of deposition is insufficient, and particularly when the wire diameter is 3.2 mm or more, which is generally used, the arc stability is deteriorated and the welding workability is deteriorated. On the contrary, if it exceeds 600 A, the penetration depth increases, and it becomes difficult to suppress the dilution rate to 20% or less. Therefore, 300 to 600
A is preferable, and the leading electrode to be weaved has a greater effect on the penetration depth than the trailing electrode, so it is more preferably limited to 500 A or less.

○ If the welding speed is less than 150 mm / min, the efficiency is insufficient and slag entrainment easily occurs. If it exceeds 2000 mm / min, undercutting occurs and the bead appearance becomes poor. Therefore, 150 to 2000 mm / min is preferable.

○ Groove The design of the groove may be appropriately determined according to the target member. For example, when applying this method to the cladding material side of clad steel and performing 1-pass welding or 1-layer 1-pass laminating welding, the groove width (W) of the cladding material is set to the weaving width +10 mm or less as shown in FIG. Is preferred. This is because when the groove width (W) of the laminated material exceeds the weaving width +10 mm, fusion failure may occur at the open tip.

〔Example〕

Example 1 Bead-on-plate welding was performed on a 16 mm-thick carbon steel under the conditions shown in Table 1 using a combination of Inconel 625 wire (3.2 mmφ) and bond flux. The conditions shown in Table 1 are the same welding amount per unit length of bead (7
It is a necessary condition to secure ~ 8 g / cm). For weaving, weaving width 15m
m, weaving frequency 50 times / min, both ends stop time 0.5
The condition was seconds. However, when the welding speed was 670 mm / min, the weaving frequency was 100 times / min. The dilution rate of the weld metal from the base metal was determined by investigating the composition of the weld metal and was set at 20% or less.

No. 1 is an example of the present invention in which the leading electrode is weaved with three electrodes, and No. 2 is an example of the present invention in which the leading electrode is weaved with two electrodes. In the case of 3 electrodes, the dilution rate is suppressed to 20% or less at a speed of 670 mm / min and in the case of 2 electrodes 350 mm / min.

On the other hand, Nos. 3 to 5 are the conventional example and the comparative example.
The case where no weaving is performed on the electrodes and the case where the second electrode and the third electrode are weaved are shown. The welding speed is 670 mm / min, but the dilution rate exceeds 20%.

Nos. 6 and 7 are for two electrodes, but the dilution ratio exceeds 20% at a speed of 350 mm / min because the leading electrode is not weaved.

Nos. 8 and 9 are the case where weaving was performed with a single electrode and the case where weaving was not performed. When weaving with a single electrode, the dilution rate is suppressed to 20% or less, but the speed is only 100 mm / min. Without weaving with a single electrode,
In addition to being inefficient, the dilution rate reaches 40%.

Example 2 With the same combination of welding material and base material as in Example 1, two-electrode bead-on-plate welding was performed while weaving the preceding electrode according to the method of the present invention, and the influence of the welding conditions and the weaving conditions on the welding results was examined. investigated. The results are shown in Table 2.

In Nos. 11 to 17, all the welding conditions including the weaving conditions were appropriate, so the welding speed reached a maximum of 1800 mm / min, the dilution rate was suppressed to 20% or less, and the welding workability was good.

On the other hand, in No. 18, the welding speed for the test is 10
Since it is set to 0 mm / min, which is extremely low, the dilution rate is kept low, but slag is involved.

In No. 19, since the welding current is insufficient, arc instability occurs.

In No. 20, the weaving width is set excessively, so that slag entrapment occurs, and in No. 22, the electrode distance is set too small, and arc instability occurs.

In No. 23, the number of weavings was too small for the welding speed, so the bead toe was uneven, and in No. 24, on the contrary, the number of weavings was too large, causing slag inclusion.

In No. 25, the welding speed was set too high, resulting in frequent undercuts.

No. 18 to 25 are examples in which conditions were intentionally shifted for testing purposes. No. 11 to 17, which were set as general conditions for two electrodes, had the same efficiency, dilution ratio, and welding as described above. Good workability results have been obtained.

Example 3 When manufacturing an inner clad steel pipe in which a base material made of carbon steel is laminated with Incoloy 825 having the composition shown in Table 3 as an inner surface mating material by the UOE method, the method of the present invention is used for welding the inner surface mating material. Applied The same welding material as in Example 1 was used, and the welding conditions shown in Table 2 No. 11 were adopted. The components shown in Table 4 are tables showing respective component values of the weld metal on the side of the laminated material at that time. As is clear from the table, the components Cr, Ni, and Mo contributing to corrosion resistance are Incoloy 825 shown in Table 3. It is contained in a larger amount than that of the above, and the dilution of the weld metal by the base metal is effectively suppressed.

[Advantages of the Invention] As described above, the multi-electrode submerged arc welding method of the present invention enables highly efficient low dilution welding without adding practically disadvantageous restrictions to welding material, groove design, welding conditions, etc. To do. Therefore, when applied to welding that requires high efficiency and low dilution such as welding of high alloy composite material in the production of clad steel pipe by UOE method, it has a great effect on product quality improvement, production efficiency improvement, production cost reduction, etc. Is to demonstrate.

[Brief description of drawings]

FIG. 1 is a view showing an example of a groove according to the present invention. In the figure, 1 is a laminated material and 2 is a base material.

Claims (1)

[Claims] 1. When welding a high alloy onto a base material made of carbon steel by a multi-electrode submerged arc welding method, only the preceding electrode is weaved at a right angle to the welding direction, and its weaving width is 10 to 30 mm. As a low-dilution multi-electrode submerged arc welding method, which is characterized by suppressing the dilution of the weld metal by the base metal.