JP3367566B2 - Large heat input single-sided submerged arc welding method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-pass, single-pass, single-pass submerged arc welding method for a steel plate having a thickness of 50 to 80 mm. 2. Description of the Related Art It is a common practice to weld extremely thick steel plates such as box joint corner joints by one-pass welding to a thickness of 50 mm using a two-electrode submerged arc welding method. However, the plate thickness of more than 50mm performed under layer welding, such as CO ₂ welding, a method of finishing by submerged arc welding of 1-2 path is normal. However, as the height of the building has been increased and the demand for higher welding efficiency has been increasing, 50 mm
As a high-efficiency welding method for the extremely thick steel plate, a one-pass welding method using a three-electrode submerged arc welding method is being studied.
By the way, in the single-sided submerged arc welding method using multiple electrodes, the distance between the electrodes is very important from the viewpoint of crack resistance, prevention of welding defects such as slag entrainment, and various studies and proposals for preventing the above items. Has been made. A method of dispersing the heat input and preventing the deterioration of toughness by increasing the distance between the electrodes or electrode groups forming one molten pool in the multi-electrode single-sided, single-layer submerged arc welding method to 300 mm or more is disclosed in Japanese Patent Publication No. Sho 56. -3998
No. 9 has been proposed. In the three-electrode submerged arc welding, the distance between one electrode and two electrodes is set to 150 to 290.
Japanese Patent Application Laid-Open No. 61-189876 proposes a method in which the distance between the two electrodes and the three electrodes is set to 30 mm or less to prevent toughness deterioration and welding defects such as slag entrapment. However, the target welding heat input was up to 1 in the examples.
It is 50 kJ / cm. Since the welding heat input required for single-sided single-layer welding with a plate thickness of 50 mm is about 400 kJ / cm, the solidification time, solidification form, or welding phenomenon of the molten metal differs from the above method, and the single-sided single-sided submerged plate with a plate thickness of 50 mm or more is different. It is difficult to apply to arc welding and prevent welding defects. SUMMARY OF THE INVENTION The present invention relates to slag entrainment, insufficient penetration, weld cracking, undercut, etc. in a three-electrode single-sided, one-pass, one-pass submerged arc welding method for a very thick steel plate using a DC power supply as a leading electrode. The purpose of the present invention is to solve the problem of welding defects. SUMMARY OF THE INVENTION The present invention is directed to a plate having a thickness of 50 to 8 mm.
In one-sided single-pass welding of a 0 mm thick steel plate, a DC power supply is used for a leading electrode (hereinafter, referred to as L), and an AC power supply is used for a middle electrode (hereinafter, referred to as M) and a following electrode (hereinafter, referred to as T).
When the plate thickness is 50 mm or more and 60 mm or less The distance between the poles within the range of the following condition 1 is used. When the plate thickness is 60 mm or more and 70 mm or less. This is a large heat input single-sided submerged arc welding method, characterized in that welding is performed with the distance between the electrodes set within the range of the following condition 3. When the thickness of the sheet is plotted on the abscissa and the distance between the poles is plotted on the ordinate, graphs are drawn for the relationship between the plate thickness and the distance between the LM poles and the relationship between the plate thickness and the distance between the MT poles. , Condition 1 is 50m thickness
m, the distance between the LM poles is 40 mm and 160 mm,
T pole distance is 90mm and 150mm, plate thickness is 60mm
When the distance between LM poles is 50 mm and 180 mm, MT
The condition range in which the distance between the poles is surrounded by 100 mm and 160 mm, and the condition 2 is that when the plate thickness is 60 mm, the distance between the LM poles is 5
0mm and 180mm, distance between MT pole is 100mm and 1
60 mm, and when the plate thickness is 70 mm, the distance between the LM poles is 6
0mm and 190mm, distance between MT pole is 110mm and 1
A condition range surrounded by 80 mm, and a condition 3 is a plate thickness of 70 mm.
When the distance between LM poles is 60 mm and 190 mm, MT
The distance between the poles is 110mm and 180mm, and the plate thickness is 80mm
When the distance between the LM poles is 70 mm and 200 mm, the MT
Condition range in which the distance between the poles is surrounded by 120 mm and 190 mm. The distance between the electrodes is a value obtained by measuring the distance between the electrodes at the bottom of the groove. The present inventors have conducted a comprehensive study on three-electrode one-sided one-sided submerged arc welding of an extremely thick steel plate, and have obtained the following findings. First, from the viewpoint of crack resistance, it is necessary to arrange the electrodes so that the molten pool formed by the electrodes does not completely separate. That is, the solidification direction of the weld metal by the leading electrode is corrected upward by the upper heating effect by the trailing electrode to prevent solidification cracks formed at the weld metal solidification association portion. Also L
Since the pole weld metal has a shape in which the length in the penetration direction is considerably longer than the width, solidification cracks are easily generated at the upper portion of the weld metal. Melting this crack is also an important role of the M pole. When the distance between the LM poles is reduced, an arc is generated in the molten metal, the penetration depth is reduced, and there is a possibility that the penetration is insufficient. In addition, it has been found that the bead width becomes narrower with a decrease in the distance between the MT poles, and there is a danger that undercut may occur. Therefore, it is necessary to properly set the distance between the electrodes so as not to cause the welding defect. The reason for limiting the gap distance will be described in detail below. When the distance between the LM poles is short, an arc is generated in the molten metal for the above-described reason, and insufficient penetration is likely to occur. In addition, slag blow-up becomes severe, and welding workability is significantly impaired. When the distance between the LM poles is increased, solidification of the L-pole molten metal proceeds at the M-pole position.
As shown in FIG. 3, the solidification crack of the weld metal generated above the pole weld metal remains as a crack as shown in FIG.
Further, the solidification of the L-pole slag proceeds, so that slag entrainment is likely to occur, and the generation of the M-pole arc becomes unstable due to the influence of the solidified slag, thereby deteriorating welding workability. As the plate thickness increases, the input welding heat input also increases. Therefore, the distance between the electrodes needs to be set according to the plate thickness as shown in FIG. When the distance between the MT poles is reduced, the bead width is reduced, and the possibility of undercut is increased. Further, since the M-pole weld pool and the T-pole weld pool form one pool, the upper heating effect by the T pole cannot be obtained, so that solidification cracking as shown in FIG. 4 is likely to occur. Further, the blow-up of slag increases, and welding workability deteriorates. If the distance between the MT poles is long, the slag by the M poles is solidified, so that the slag is likely to be entrained, the generation of the T pole arc becomes unstable, and the welding workability deteriorates. The distance between the MT poles also needs to be set as shown in FIG. 2 according to the increase in the plate thickness. From the above, it has been found that adjusting the distance between the LM poles and the distance between the MT poles to an appropriate range is an essential condition for performing defect-free welding.
That is, FIG. 1 shows the relationship between the LM pole-to-pole distance and the defect at each plate thickness of 50, 60, 70, and 80 mm.
FIG. 2 shows the relationship between the distance between the poles and the defect.
When the distance between the LM poles is 40 to 160 mm, the distance between the MT poles is 90 to 150 mm, and when the plate thickness is 60 mm, L-
The distance between M poles is 50 to 180 mm, and the distance between MT poles is 10
When the thickness is 0 to 160 mm and the thickness is 70 mm, the distance between the LM poles is 60 to 190 mm, and the distance between the MT poles is 110 to 180.
mm, the thickness between the LM poles is 70 to 2 when the plate thickness is 80 mm.
By setting the distance between the poles to 00 mm and the distance between the MT poles to 120 to 190 mm, welding having a sound bead without defects is possible. The reason why a DC power supply is used for the leading electrode is that DC has a deeper penetration than AC and has good arc stability, and the DC power supply is not used for the intermediate and trailing electrodes. This is to avoid magnetic blowing of the arc due to the magnetic field generated by the DC current at the pole and the DC current at the rear. EXAMPLES Table 1 shows welding conditions and welding results for examples according to the present invention. In Table 1, the unit of the groove angle is deg, the root face (RF) is mm, the current is V,
The distance between the poles is mm. The practice of the present invention resulted in a sound weld bead. [Table 1] The case shown in Table 2 is a comparative example using the condition that the distance between the poles is out of the range of the present invention. L-
If the distance between the M poles is short, insufficient penetration occurs, and if the distance between the MT poles is short, undercutting occurs. L-
If the distance between the M poles is long, cracks occur, and if the distance between the MT poles is long, slag entrainment occurs. In Comparative Example 13, although the distance between the electrodes was within the range of the present invention, the penetration was insufficient due to the use of alternating current as the power supply for the leading electrode. [Table 2] By using the welding method according to the present invention, it is possible to perform one-sided single-pass welding of a plate thickness of 50 to 80 mm without defects, and it is not necessary to perform rework after welding, thereby improving the efficiency of welding work. Has improved dramatically.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a characteristic diagram showing a relationship between a distance between an LM pole and a defect when a distance between an MT pole is fixed to 120 mm. FIG. 2 is a characteristic diagram showing a relationship between a distance between the MT poles and a defect when the distance between the LM poles is fixed to 120 mm. FIG. 3 is an explanatory diagram showing weld metal solidification cracking when the distance between LM poles is long. FIG. 4 is an explanatory diagram showing weld metal solidification cracking when the distance between MT electrodes is short.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-210874 (JP, A) JP-A-2-52174 (JP, A) JP-A-4-266482 (JP, A) JP-A-58- 135766 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B23K 9/18

Claims (1)

(57) [Claims 1] In a single-sided one-pass submerged arc welding of a thick steel plate having a thickness of 50 to 80 mm, a DC power supply is used for a leading electrode (hereinafter referred to as L) and an intermediate electrode (hereinafter referred to as M). ) And a trailing electrode (hereinafter referred to as T) using an AC power source and having a thickness of 50
In the case of not less than 60 mm and 60 mm or less, the distance between the poles within the range of the following condition 1 is used.
In the following case, a large heat input single-sided submerged arc welding method is performed in which welding is performed with the distance between the electrodes set within the range of the following condition 3. When the thickness of the sheet is plotted on the horizontal axis and the distance between the poles is plotted on the vertical axis, graphs are drawn for the relationship between the plate thickness and the LM pole distance and the relationship between the plate thickness and the MT pole distance, respectively. Is the distance between the LM poles is 40 mm when the plate thickness is 50 mm
And 160mm, the distance between MT poles is 90mm and 150mm
When the plate thickness is 60 mm, the distance between the LM poles is 50 mm and 180 mm, and the distance between the MT poles is 100 mm and 160 mm.
Condition 2 is that the distance between the LM poles is 50 m when the plate thickness is 60 mm.
m and 180 mm, the distance between MT poles is 100 mm and 160
mm, and when the plate thickness is 70 mm, the distance between the LM poles is 60 m.
m and 190 mm, the distance between MT poles is 110 mm and 180
and Condition 3 is that the distance between the LM poles is 60 mm when the plate thickness is 70 mm.
And 190mm, the distance between MT poles is 110mm and 180m
m, and when the plate thickness is 80 mm, the distance between the LM poles is 70 mm.
And 200mm, the distance between MT poles is 120mm and 190m
Condition range surrounded by m. The distance between the electrodes is a value obtained by measuring the distance between the electrodes at the bottom of the groove.