Submerged arc welding method for steel sheets

Abstract

Provided is a submerged arc welding method whereby: welds are provided with high toughness with low input heat; the heights of weld reinforcements can be reduced by minimizing melting that exceeds a requisite amount of wire; and deep penetration and a wide bead width can be obtained. The diameter of a first electrode wire at the head thereof in the welding direction is set at 2.0 to 3.2 mm, and the current density is at least 145 A / mm2. A second electrode onward is positioned in a single line behind the first electrode. The shape of a groove formed on a steel sheet is a two-level groove that satisfies [theta]B < [theta]T, where [theta]B represents a bottom-layer-side groove angle, and [theta]T represents a top-layer-side groove angle.

Description

technical field [0001] The invention relates to submerged arc welding of steel plates, in particular to submerged arc welding suitable for seam welding of large-diameter steel pipes such as UOE steel pipes and spiral steel pipes. Background technique [0002] Submerged arc welding (for example, refer to Patent Documents 1 and 2) using two or more electrodes for seam welding of large-diameter steel pipes such as UOE steel pipes and spiral steel pipes has become popular, and is widely used from the viewpoint of improving the productivity of large-diameter steel pipes. It is an efficient double-sided single-layer surfacing welding with one bead on the inner surface side and one bead on the outer surface side. [0003] In double-sided single-layer surfacing welding, it is necessary to ensure the depth of penetration so that the weld metal on the inner surface side and the weld metal on the outer surface side are fully fused without producing unmelted parts. Therefore, a large cu...

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Problems solved by technology

[0004] On the other hand, in the seam welding of large-diameter steel pipes, there are problems such as deterioration of the toughness of the welded part, especially the heat-affected zone. In order to improve the toughness of the welded part, it is necessary to reduce the welding heat input as much as possible.

However, if the welding heat input is reduced, there is a problem that the risk of insufficient penetration increases, unmelted parts are likely to occur, and surface defects such as undercuts are likely to occur

[0007] However, in the technology disclosed in Patent Document 3, arc energy is injected in the thickness direction of the steel sheet to suppress dissolution in the width direction of the steel sheet, so there is a problem that the bead width becomes small, and surface defects such as undercuts tend to occur.

[0009] However, in the technology disclosed in Patent Document 4, although the effect of increasing the bead width is obtained, a large current must be supplied in order to significantly increase the bead width. The problem of deterioration of resilience

In addition, supplying a large current will increase the melting amount of the welding wire and increase the reinforcement height of the weld, so it is necessary to redesign the groove shape

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