JPH0857642A - Manufacture of welded steel tube - Google Patents

Abstract

(57) [Abstract] [Purpose] It can be applied to welded steel pipe production line easily and effectively, and the excess part of the tack weld bead can be removed easily, quickly and efficiently. (EN) Provided is a welded steel pipe manufacturing method capable of eliminating any influence on the welded steel pipe. [Structure] After temporarily welding the abutting portion of the base material formed into a tubular shape, the main surface of the other surface is welded. Next, before performing main welding on the side where the tack welded portion is present, the bead protrusion of the tack welded portion is melted and removed by a high energy density heat source beam to be smoothed, and the smoothed groove is formed. Perform main welding. [Effect] A welded steel pipe having a high quality welded joint can be manufactured at low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a welded steel pipe such as a UOE welded steel pipe, and more particularly to a method for manufacturing a welded steel pipe having a high quality welded joint.

[0002]

2. Description of the Related Art Welded steel pipes are manufactured by forming raw steel plates into a tubular shape by a process such as CU-0 press, roll bend, press head, tube mill, spiral mill, and melting and welding the end face abutting portions. This is conventionally done. In the method for manufacturing such a welded steel pipe,
The open seam pipe that has been formed is subjected to temporary welding and internal and external main welding in the welding process. The welding procedure will be described with reference to FIG. 3. First, the tubular steel sheet 1 is formed.
Grooves 2-1 and 2-2 are formed by performing groove processing on the inner surface and the outer surface side of the end face abutting portion of (a). Next, tack welding is performed on the outer seam portion by a tack welding machine to form tack welding beads 3 (b). Then, main welding (generally using a submerged arc welding method) is performed from the inner surface side and the outer surface side to form the main welding beads 4-1 and 4-2 (c).

When performing pipe welding by the above method, the main welding bead 4 formed on the temporary welding bead 3 side (outer surface side)
-2 is formed by welding the groove 2-1 without the tack welding bead because the extra portion 3-1 of the tack welding bead 3 has a convex shape as shown in FIG. 3B. The arc becomes unstable as compared with the main weld bead 4-1 thus produced, and welding defects such as slag inclusion or undercut occur. Furthermore, since the penetration depth is shallow and the fluctuations are large, the welding heat input is too large in order to obtain a sufficient penetration depth, resulting in excessive build-up height and poor weld toughness. There was a problem such as.

Therefore, as a means for solving such a problem, there has been proposed a method of mechanically cutting the temporary welding bead portion and reworking the groove to perform main welding (Japanese Patent Laid-Open No. 54-54).
-40266). That is, this method deeply cuts the base metal together with the temporary welding beads for thick base metal to form a deeper groove than the existing groove, and for thin base metal, This is a method of cutting only the welded bead to reveal the original groove again, and a cutting machine such as a motor-driven cutter is used as the cutting means.

[0005]

However, the method of mechanically cutting the temporary welding bead portion and reworking the groove to perform the main welding is to remove the influence of the temporary welding bead on the main welding. However, there are drawbacks described below.

That is, in the method of mechanically cutting the weld bead portion, the operation of the cutting machine and the cutting of the weld bead are time-consuming and inefficient, and therefore, for example, the welding speed (usually 4 Cost increase is inevitable in order to make the efficiency commensurate with (~ 12 m / min). In addition, since the equipment must be upsized, it is difficult to install it in the limited space of the welded steel pipe production line, and the equipment cost is high.

The present invention has been made in order to solve the above-mentioned conventional drawbacks, and can be easily and effectively applied to a welded steel pipe production line, and the remaining of the temporary welding bead portion can be simply, quickly and efficiently. An object of the present invention is to propose a method for manufacturing a welded steel pipe which can remove the raised portion (protruding portion) and can eliminate the influence of the tack weld bead on the main welding.

[0008]

A method for manufacturing a welded steel pipe according to the present invention is a method of manufacturing a welded steel pipe by temporarily welding the abutting portions of a base material formed into a tubular shape and then performing main welding from the inner surface and the outer surface. In the method of manufacturing, the temporary welding is performed from the other surface prior to the main welding of one of the inner and outer surfaces, and the main welding of the one surface is performed after the temporary welding, and then the other Before the main welding of the surface of, the bead protruding portion of the tack welding portion is removed by melting to smooth the groove portion,
A method of performing main welding on the other surface is summarized, and as a means for melting and removing the bead protrusion of the tack weld portion in this method, 0.1 kw / mm ^{2 is} applied to the surface of the tack weld portion.
Irradiating the above high-energy-density heat source beam, and melting the bead protrusion to smooth the groove, and the high-energy density heat source beam with a laser beam, a plasma arc, or an electron beam. It is characterized by being used.

[0009]

In the present invention, the bead protruding portion (excessive portion) of the tack welded portion is melted to smooth the groove portion, and the smoothed groove portion is main welded. The arc is stable like the main weld bead formed by welding the groove
No welding defects such as slag inclusion and undercut. Further, since the penetration depth is deep and the fluctuation is small, a sufficient penetration depth can be obtained without increasing the welding heat input amount, and the weld zone toughness is not deteriorated.

As a means for melting the bead protruding portion of the tack welded portion to smooth the groove shape, a heat source having a relatively low energy density such as TIG arc can be used. Welding speed in welding (4-12m /
Min) to obtain a bead width (4 mm or more) of 0.1
A heat source beam having a high energy density of kw / mm ² or more is required, and a laser beam, a plasma arc, or an electron beam is used as a heat source capable of obtaining such a high energy density.

FIG. 1 shows the relationship between the energy density and the processing speed when a TIG arc, a plasma arc, a laser beam or an electron beam is used as a heat source. As is clear from this figure, the energy density is 0.
With a TIG arc of 01 kw / mm ² , the target processing speed of 4 m / min for obtaining a processing width of 4 mm or more cannot be reached.
It is difficult to use as a heat source for melting the bead protruding portion of the tack welded portion to obtain a predetermined groove shape. On the other hand, in the case of a laser beam, a plasma arc, and an electron beam, a high energy density of 0.1 kw / mm ² or more satisfying a target processing speed of 4 m / min for obtaining a processing width of 4 mm or more is obtained, It is suitable as a heat source for melting the bead protruding portion of the tack welded portion to obtain a predetermined groove shape.

[0012]

EXAMPLE FIG. 2 is a diagram showing a welding process of welded steel pipe according to an embodiment of the present invention, and 5 is a high energy density heat source beam.

That is, in FIGS. 2 (a) to 2 (c), as in the conventional case, a groove is formed on the inner surface and the outer surface of the end face abutting portion of the material steel plate 1 formed in a tubular shape to form a groove 2- 1,
2-2 is formed (a), and temporary welding is performed on the outer seam portion by a temporary welding machine to form a temporary welding bead 3 (b).
Then, main welding is performed on the inner seam portion by the main welding machine to form the main welding beads 4-1 (c). Next, the surface of the tack weld bead 3 is irradiated with a high energy density heat source beam 5 of 0.1 kw / mm ² or more (d), and the bead protrusion is melted to smooth the surface of the tack weld bead 3. Sliced groove 2-
1-1 is formed (e). The groove processing width t at this time is 4 m
m or more. Thereafter, main welding is performed on the outer seam portion by the main welding machine to form the main welding beads 4-2 (f). High energy density heat source, laser beam,
Either plasma arc or electron beam is used. In addition, the tack welding is generally performed by a gas shield arc welder, and the main welding is generally performed by a submerged arc welder.

Example 1 The outer seam portion of a blank tube having the components and dimensions shown in Table 1 and subjected to a predetermined groove process was tack welded under a welding condition shown in Table 2 by a gas shield arc welding machine. After that, the inner seam portion is main welded by the submerged arc welding machine under the conditions shown in Table 3, and then the groove on the temporary welding bead side is processed under the temporary welding bead processing conditions shown in Table 4, and the groove processing is performed. rear,
When the outer seam portion was main-welded under the conditions shown in Table 3 and the results of the main-welding on the temporary-welding bead side were used as the melting heat source for the temporary-welding bead, a low energy density heat source outside the scope of the present invention was used (comparison). Table 5 shows a comparison between the example) and the case where the tack weld beads were processed by mechanical cutting and the case where they were not processed at all (conventional example). It should be noted that Table 5 shows the results of 1000 tests.

As is clear from Tables 4 and 5, Test No. 1 to 3 are all target processing speeds of 4 m /
In addition, there were no welding defects in the main welding bead on the temporary welding bead side (external pipe side). Further, the required welding heat input amount was as low as 40 kJ / cm, and the surplus height of the main welding bead was as low as 1.5 mm, and a good bead was formed. On the other hand, the test No. of the comparative example in which the TIG arc of low energy density was used as the heat source for the melting process of the tack welding beads. No. 4 and test No. 4 using a laser beam whose energy density was reduced by defocusing. In 5, the processing speed did not reach the target of 4 m / min. In addition, the test No. of the conventional example using the mechanical cutting method for processing the tack weld beads. 6
As for the test No., the processing speed did not reach the target of 4 m / min, and the tack weld beads were not processed. Regarding No. 7, a slag inclusion defect with a number ratio of 1.5% occurred in the outer surface main welding bead, and the necessary welding heat input amount and the extra weld height of the main welding bead were high values of 50 kJ / cm and 3 mm, respectively. The result was extremely unfavorable.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

[Table 5]

[0021]

As described above, the method of the present invention uses the high energy density heat source beam for the smoothing treatment of the tack weld bead to prevent the welding defect of the main weld bead and the tack weld bead side book. It has a great effect on reducing the required welding heat input of the weld bead and can be easily applied to the existing welded steel pipe production line, so the groove after tack welding can be efficiently applied without causing any disadvantageous restrictions to the pipe making process. The shape can be smoothed, the manufacturing cost can be significantly reduced compared to the conventional mechanical cutting method, and high quality welded joints with excellent uniformity and soundness can be obtained at low cost. It has an excellent effect that it can.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between respective energy densities and processing speeds when a TIG arc, a plasma arc, a laser beam, and an electron beam are used as a heat source of a melt removing means of a tack weld bead portion of a welded steel pipe.

FIG. 2 is an explanatory view showing an embodiment of the present invention, in which (a) to (f)
FIG. 4 is a pipe welding process diagram of a welded steel pipe.

FIG. 3 is an explanatory diagram showing a conventional example to which the present invention is applied.
(a)-(c) is a pipe-making welding process figure of a welded steel pipe.

[Explanation of symbols]

 1 Raw material steel plate 2-1, 2-1, 2-2 Groove 3 Temporary welding bead 3-1 Extra part 4-1 and 4-2 Main welding bead 5 High energy density heat source beam

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location B23K 31/00 P 37/08 Z (72) Inventor Hiroyuki Yoshikawa 4-chome Kitahama, Chuo-ku, Osaka City, Osaka Prefecture No. 5 33 Sumitomo Metal Industries, Ltd.

Claims (3)

[Claims] 1. A method for producing a welded steel pipe by temporarily welding a butt portion of a base material formed into a tubular shape and then performing main welding from an inner surface and an outer surface, wherein either one of the inner surface and the outer surface is manufactured. Prior to the main welding, the temporary welding is performed from the other surface, after the temporary welding, the main welding of the one surface is performed, and subsequently, the bead protrusion of the temporary welding portion is performed before the main welding of the other surface. Part by melting and smoothing the groove part,
A method for manufacturing a welded steel pipe, characterized in that main welding of the other surface is performed. 2. The surface of the tack weld is 0.1 kw / m.
The method for producing a welded steel pipe according to claim 1, wherein the groove portion is smoothed by irradiating a high energy density heat source beam of m ² or more and melting the bead protruding portion. 3. The method for producing a welded steel pipe according to claim 2, wherein a laser beam, a plasma arc or an electron beam is used as the high energy density heat source beam.