JP-7855536-B2 - Ar-CO2 mixed gas shielded arc welding flux-cored wire

Inventors

• 浅野 宏弥
• 岩上 友勝

Assignees

• 日鉄溶接工業株式会社

Dates

Publication Date

20260508

Application Date

20230220

Claims (1)

1. In a flux-cored wire for Ar- CO2 mixed gas shielded arc welding, which has a steel outer sheath filled with flux, As a mass percentage of the total wire mass, the sum of the steel sheath and flux, C: 0.03-0.08%, Si: 0.1-0.6%, Mn: 1.5-2.8%, Cu: 0.01 to 0.5%, Ni: 0.5-1.5%, Ti: 0.05-0.25%, B: Contains 0.002 to 0.015%, Al: 0.05% or less, The total amount of Nb and V, or either one or both, is 0.01 to 0.1%. Furthermore, in mass % of the total wire mass, the flux contains Total Ti oxide equivalent value: 3-8 % Total Al oxide content in Al₂O₃ equivalent : 0.02–0.3% Total SiO2 equivalent value of Si oxide: 0.1–0.6% Total Zr oxide content in ZrO2 equivalent: 0.25–0.65% One or more of the following: sodium oxides, sodium fluorides, potassium oxides, and potassium fluorides: 0.05 to 0.2% in total, based on the values of Na₂O and K₂O . Mg: 0.1-0.8%, Total F equivalent value of fluorine compounds: 0.05–0.25% The total Bi equivalent value of either or both Bi and Bi oxides contains 0.001 to 0.01%. Ar- CO2 mixed gas shielded arc welding flux-cored wire, characterized in that the remainder consists of Fe from the steel outer sheath, iron powder, Fe content from iron alloy powder, and impurities.

Description

The present invention relates to a flux-cored wire for Ar-CO2 mixed gas shielded arc welding, which provides good arc stability, low spatter generation, particularly good slag detachability, no welding defects, and excellent strength and low-temperature toughness of the weld metal in all -position circumferential welding of steel pipes. Flux-cored wires for gas shielded arc welding, particularly rutile-type flux-cored wires offering superior welding efficiency and workability in all-position welding, are widely used in various fields such as shipbuilding, bridges, offshore structures, and steel structures. For example, in recent years, the development of natural gas and oil fields on the seabed has progressed, leading to an increase in pipeline construction. Therefore, flux-cored wires for gas shielded arc welding, enabling highly efficient construction in all-position welding of pipelines, are being used. Because pipelines are laid on land, underwater, and in cold regions, they require extremely high reliability due to harsh operating environments, and high quality is also required for welds. For example, Patent Document 1 discloses a flux-cored wire technology that achieves good weldability in all positions by specifying a fluorine compound containing Na and K. However, the technology disclosed in Patent Document 1 does not contain Bi and has a small amount of Zr oxide, resulting in poor slag detachability and welding defects such as slag inclusion. Furthermore, the lack of Nb and V means that the strength of the weld metal of steel pipes cannot be consistently obtained. Patent Document 2 discloses a flux-cored wire technology that achieves good weldability and low-temperature toughness in all-position welding by optimizing the slag, alloy, and deoxidizing agent components. However, the technology disclosed in Patent Document 2 does not include Nb and V, resulting in the problem that the strength of the weld metal for steel pipes cannot be consistently obtained. Japanese Patent Publication No. 2016-131985Japanese Patent Publication No. 2018-153853 Figure 1 shows the groove shape of a steel pipe used in weld metal testing. The following describes the component composition and content of flux-cored wire for Ar- CO2 mixed gas shielded arc welding to which the present invention is applied, as well as the reasons for limiting the composition of each component. The content of each component will be expressed as a mass % relative to the total mass of the flux-cored wire, and when expressing the mass %, it will simply be written as %. [Total C content of steel shell and flux: 0.03–0.08%] Carbon (C) has the effect of improving the strength of the weld metal. However, if the C content is less than 0.03%, the strength of the weld metal will be low. On the other hand, if the C content exceeds 0.08%, the strength of the weld metal will be excessive, and its low-temperature toughness will decrease. Therefore, the total C content of the steel sheath and flux should be between 0.03% and 0.08%. In addition to the components contained in the steel sheath, C can be added from metal powders and alloy powders in the flux. [Total Si content of steel shell and flux: 0.1–0.6%] Si contributes to improved weldability by enhancing the appearance and shape of the weld bead through partial formation as weld slag during welding. However, if the Si content is less than 0.1%, the effect of improving the appearance and shape of the weld bead is not sufficiently obtained. On the other hand, if the Si content exceeds 0.6%, the excess Si remains in the weld metal, resulting in excessive strength and a decrease in the low-temperature toughness of the weld metal. Therefore, the total Si content of the steel sheath and flux should be between 0.1% and 0.6%. In addition to the components contained in the steel sheath, Si can be added from the flux using alloy powders such as metallic Si, Fe-Si, and Fe-Si-Mn. [Total Mn content of steel shell and flux: 1.5–2.8%] Like Si, manganese (Mn) contributes to improved welding workability by improving the appearance and shape of the weld bead as part of the weld slag during welding. Furthermore, Mn retains in the weld metal, increasing its strength and low-temperature toughness. However, if the Mn content is less than 1.5%, the bead appearance and shape are poor, and the low-temperature toughness of the weld metal decreases. On the other hand, if the Mn content exceeds 2.8%, an excessive amount of Mn is retained in the weld metal, resulting in excessively high weld metal strength and decreased low-temperature toughness. Therefore, the total Mn content of the steel sheath and flux should be between 1.5% and 2.8%. In addition to components contained in the steel sheath, Mn can be added from alloy powders such as metallic Mn, Fe-Mn, and Fe-Si-Mn from the flux. [Total Cu content of steel shell and flux: 0.01–0.5%] Cu refines the microstructure of the weld metal, increasing its strength and low-temperature tough