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EP-4737045-A1 - NARROW-GROOVE GAS-SHIELDED ARC WELDING METHOD

EP4737045A1EP 4737045 A1EP4737045 A1EP 4737045A1EP-4737045-A1

Abstract

Provided is a narrow-gap gas-shielded arc welding method that can achieve high welding efficiency and produce a weld joint while preventing defects such as poor penetration on a groove surface. Specifically, provided is a narrow-gap gas-shielded arc welding method for joining steel plates with a plate thickness t of 22 mm or greater using narrow-gap multi-layer welding by setting the angle θ of a groove between the steel plates to 25° or less and setting the gap G of the groove at the bottom to 7 mm to 18 mm, the method including setting the distance d between a side edge portion at the welding wire tip and a groove surface at the bottom of the steel plate to a range of 3.0 mm or less, and setting the value of a variable K determined from Expression (1) below to a range of 24.0 to 66.0: K = 92.3 × I / W + 9.1 × H − 0.5 × d where H represents the welding heat input (kJ/mm), I represents the welding current (A), and W represents the welding wire feed rate (cm/min).

Inventors

  • KONISHI, Kyohei
  • NAGAO, RYOTA
  • KOZUKI, Shohei
  • TANIGUCHI, KOICHI

Assignees

  • JFE Steel Corporation

Dates

Publication Date
20260506
Application Date
20240325

Claims (6)

  1. A narrow-gap gas-shielded arc welding method for joining steel plates having a plate thickness t of 22 mm or greater, comprising performing narrow-gap multi-layer welding with a groove angle θ of 25° or less and a groove gap G at a bottom within the range of 7 mm to 18 mm, characterized in that a distance d between a side edge portion at a welding wire tip and a groove surface at a bottom of the steel plate is adjusted to fall within a range of 3.0 mm or less, and wherein a value of a variable K determined from Expression (1) below is adjusted to fall within a range of 24.0 to 66.0: K = 92.3 × I / W + 9.1 × H − 0.5 × d where H represents a welding heat input (kJ/mm), I represents a welding current (A), and W represents a welding wire feed rate (cm/min).
  2. The narrow-gap gas-shielded arc welding method according to claim 1, wherein a distance h from a tip of a power supply tip of a welding torch to the welding wire tip is set within a range of 10 mm to 40 mm, and a feed angle ϕ of the welding wire with respect to the groove at the bottom is set within a range of 0° to 15° with respect to a perpendicular line.
  3. The narrow-gap gas-shielded arc welding method according to claim 1 or 2, wherein a diameter f of the welding wire is set within a range of 1.0 mm to 1.6 mm, the welding heat input H is set within a range of 0.8 kJ/mm to 2.3 kJ/mm, the welding current I is set within a range of 270 A to 370 A, and the welding wire feed rate W is set within a range of 1000 cm/min to 1700 cm/min.
  4. The narrow-gap gas-shielded arc welding method according to any one of claims 1 to 3, wherein a penetration depth p at the groove surface is set to 1.0 mm or greater.
  5. The narrow-gap gas-shielded arc welding method according to any one of claims 1 to 4, wherein a mixed gas containing 20 volume% or more CO 2 gas is used as a shielding gas for the gas-shielded arc welding.
  6. The narrow-gap gas-shielded arc welding method according to any one of claims 1 to 5, wherein the welding wire fed to the power supply tip of an electrode is curved to have a curvature radius ρ within a range of150 mm to 300 mm.

Description

Technical Field The present invention relates to a gas-shielded arc welding method, particularly to a narrow-gap gas-shielded arc welding method to be applied to steel plates (hereinafter also simply referred to as "thick steel plates") with a thickness of 22 mm or greater. The "narrow gap" herein means that the angle of a groove is 25° or less, and the minimum width of the groove gap between the steel plates, which are the materials (base metals) to be welded together, is 50% or less of the thickness of the steel plates. The numerical range "x to y" represents x or more and y or less, inclusive of boundary values. Background Art Gas-shielded arc welding used to weld steel plates together is widely utilized in the manufacturing fields, including but not limited to automobiles, buildings, bridges, and electrical devices. In recent years, with the trend toward increased size and wall thickness of steel structures, the amount of deposit metal required for welding, particularly for butt welding of steel plates in the manufacturing process has increased. Consequently, the welding process has become more time-consuming, resulting in higher manufacturing costs. To address the challenge, the application of a narrow-gap gas-shielded arc welding method is being considered. The method involves performing multi-layer welding on a groove between steel plates with a small gap relative to the plate thickness, using a gas-shielded arc welding method. Compared with conventional gas-shielded arc welding methods, the narrow-gap gas-shielded arc welding method requires less deposit metal, enables high-efficiency and energy-saving welding, and is further expected to reduce the process costs. In response to such a demand, Patent Literature 1 discloses a double-sided multi-layer welding method for a double-sided U-shaped groove joint. The welding method includes performing layered welding based on TIG welding with the use of an inert gas, wherein the inert gas is employed to suppress the generation of slag and spatter and prevent defects in the stacked layers. Patent Literature 2 discloses narrow-gap welding that includes weaving a welding torch to suppress spatter and incomplete fusion. Patent Literature 3 discloses a narrow-gap gas-shielded arc welding method for joining thick steel materials involving performing multi-layer welding on a narrow groove between the steel materials. According to the method described in Patent Literature 3, the first-layer welding is performed using multi-electrode welding with two or more electrodes, where one of the preceding first and second electrodes has straight polarity and the other has reverse polarity, with both positioned along predetermined parallel weld lines. Further, the distance between the welding wire tips of the first and second electrodes is set to 5 mm to 16 mm, the angle of a straight line connecting the welding wire tips of the first and second electrodes, with respect to the direction perpendicular to the weld lines is set to 45° or less, and the depth of fusion in the direction perpendicular to the weld lines at the bottom of the thick steel materials is set to 1.5 mm or greater. The method is to improve welding efficiency without causing defects, even when performing beveling working such as gas cutting or plasma arc cutting. Citation List Patent Literature Patent Literature 1: JP-2009-061483APatent Literature 2: JP-2010-115700APatent Literature 3: JP-2015-223605A Summary of Invention Technical Problem However, the TIG welding method, which uses a non-consumable electrode as described in Patent Literature 1, has a significantly lower welding efficiency than MAG or CO2 welding, which uses steel wires as consumable electrodes. In addition, according to the welding method described in Patent Literature 2, the weaving direction of the welding torch is oriented toward the steel plate surface rather than toward the depth direction of the groove, making it necessary to weave the welding torch before molten metal drips. Consequently, it is necessary to use a low welding current of approximately 150 A to suppress the amount of deposit metal per pass. Therefore, when this welding method is applied to the welding of thick steel plates, multi-pass layered welding with small amounts of deposit metal is required, which leads to an increase of defects in the stacked layers, such as poor penetration, as well as a significant decrease in welding efficiency. Further, it is commonly known that gas-shielded arc welding, when performed with straight polarity, results in arc instability and a large amount of spatter. When the method described in Patent Literature 3 is employed, a large amount of spatter may be generated from the electrode for which straight polarity is adopted, and spatter may adhere to the inside of the groove as well as to the welding torch, which may cause welding defects. Furthermore, when multi-electrode welding is performed with three or more electrodes, hot cracks may oc