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KR-20260064508-A - Welding wire, fused flux, and welding material comprising the same for high heat input electroslag welding for LPG or ammonia transport ships

KR20260064508AKR 20260064508 AKR20260064508 AKR 20260064508AKR-20260064508-A

Abstract

A welding wire, a molten flux, and a welding material containing these are disclosed for use in high heat input ESW welding for LPG or ammonia carriers. The welding wire according to the present invention contains chemical components within the following ranges so as to ensure impact toughness of 27J or more at -60°C after welding. Si: 0.2~0.5 wt%, Mn: 1.1~1.8 wt%, Ni: 1~2 wt%, Ti: 0.15~0.25 wt%, Mo: 0.1~0.3 wt%, B: 0.002~0.006 wt%

Inventors

  • 장길수
  • 김병철

Assignees

  • 에이치디한국조선해양 주식회사
  • 현대종합금속 주식회사

Dates

Publication Date
20260507
Application Date
20250910
Priority Date
20241031

Claims (6)

  1. A welding wire used for high heat input ESW welding for LPG or ammonia carriers, characterized by containing chemical components within the following range to ensure impact toughness of 27J or more at -60℃ after welding. Si: 0.2~0.5 wt% Mn: 1.1~1.8 wt% Ni: 1~2 wt% Ti: 0.15~0.25 wt% Mo: 0.1~0.3 wt% B: 0.002~0.006 wt%
  2. In paragraph 1, The welding wire described above is characterized by having a metal-cored wire structure in which metal powder is filled inside the outer sheath.
  3. In paragraph 1 or 2, A welding wire characterized by the composition of the above welding wire satisfying the following mathematical formula 1. [Mathematical Formula 1] 27 < 463 - 2112×wt%C - 306×wt%Si - 20.2×wt%Mn - 1777×wt%Al - 101×wt%Ni + 1040×wt%Ti - 644×wt%O (Note: wt% refers to the weight percentage of each indicated compositional element)
  4. A molten flux used for high heat input ESW welding for LPG or ammonia carriers, characterized by containing chemical components within the following ranges. SiO₂: 34~38 wt% Na₂O: 0.15~0.19 wt% K₂O: 0.8~1.5 wt% F: 1.5~2.5 wt% Al₂O₃: 4.1~6.1 wt% MgO: 3~6 wt% CaO: 3~6 wt% MnO: 30~50 wt%
  5. In paragraph 4, The above flux is a molten flux characterized by forming TiN and CaO-based non-metallic inclusions during welding to induce austenite grain refinement in the weldment and improve impact toughness.
  6. As a welding material used for high-heat input ESW welding for LPG or ammonia carriers, A welding wire containing Si: 0.2~0.5 wt%, Mn: 1.1~1.8 wt%, Ni: 1~2 wt%, Ti: 0.15~0.25 wt%, Mo: 0.1~0.3 wt%, and B: 0.002~0.006 wt%; and, A welding material comprising a molten flux containing SiO₂: 34~38 wt%, Na₂O: 0.15~0.19 wt%, K₂O: 0.8~1.5 wt%, F: 1.5~2.5 wt%, Al₂O₃: 4.1~6.1 wt%, MgO: 3~6 wt%, CaO: 3~6 wt%, and MnO: 30~50 wt%.

Description

Welding wire, fused flux, and welding material comprising the same for high heat input electroslag welding for LPG or ammonia transport ships The present invention relates to a welding wire, a molten flux, and a welding material containing the same, used for high heat input ESW welding for LPG or ammonia carriers. More specifically, the invention relates to a welding wire and a molten flux with optimized chemical composition to ensure impact toughness of the weld even in a cryogenic environment of -60°C, and a welding material containing the same. Since LPG or ammonia carriers must maintain the internal temperature of their cargo tanks at -60°C or lower during operation, welding technology capable of maintaining high impact toughness even at cryogenic temperatures is required for the tank and hull structures. To satisfy these cryogenic conditions, high-toughness low-alloy steel is primarily used for the ship's structures, and welding of this material must also ensure high-quality and uniform performance. To increase the productivity of ships, Electroslag Welding (ESW), an automatic welding method with high heat input, is being increasingly applied to large assembly processes. Compared to multi-layer, multi-pass manual welding, ESW has the advantage of higher productivity and fewer defects such as porosity and slag inclusion. However, due to the very high heat input, the cooling rate of the Heat Affected Zone (HAZ) slows down, resulting in the formation of a coarse microstructure at the Fusion Line (F/L) and F/L+1mm regions, which leads to a decrease in impact toughness. In existing technologies, various mechanical or electrical condition controls were attempted to solve the problem of toughness degradation, but there were limitations in reliably satisfying the cryogenic impact toughness criteria of -60°C and 27J or higher. In particular, since the chemical composition of conventional welding wires and fluxes is standardized, the control of the metal microstructure formed after welding was limited, and consequently, it was difficult to structurally improve the weak areas of the HAZ. Therefore, in order to secure impact toughness of 27J or more even under -60℃ conditions, a welding wire and flux of a new composition capable of controlling the microstructural characteristics of the weld metal and heat-affected zone formed after welding are required. To solve this technical problem, the present invention proposes a welding material capable of securing excellent cryogenic impact toughness even in high heat input ESW processes by providing a welding wire having a specific chemical composition range and a molten flux that induces austenite grain refinement. Figure 1 is a conceptual diagram illustrating welding materials applied to the ESW welding process. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete, and to ensure that the spirit of the present invention is sufficiently conveyed to those skilled in the art. Throughout the specification, the same reference numerals indicate the same components. Figure 1 is a conceptual diagram illustrating welding materials applied to the ESW welding process. As shown in FIG. 1, two welding members (10) are arranged facing each other, and a backing material (20) is installed on the lower part of them. ESW welding proceeds in a vertical direction, and the weld area is first filled with flux (F), which is a welding material. At this time, the flux is continuously supplied through a flux supply pipe (110) installed at the top. The torch (120) generates an arc while transporting another welding material, the welding wire (W), between the welds, and the flux (F) is melted by the arc heat to form a slag layer (S). The slag layer (S) acts as a current transmission path, stabilizing the arc and simultaneously inducing the melting of the wire (W) to create molten metal (MM) underneath. The formed molten metal (MM) gradually solidifies to form weld metal (WM), thereby completing the joint between the weld members (10). In this welding process, the welding wire (W) of the present invention has a composition in which Si, Mn, Ni, Ti, Mo, and B are adjusted to a predetermined range, and is implemented as a metal-cored structure to increase heat input concentration and improve melting efficiency. In addition, the molten flux (F) of the present invention has a composition in which SiO₂, Na₂O, K₂O, F, Al₂O₃, MgO, CaO, and MnO components are adjusted, and forms non-metallic inclusions of the TiN and CaO series when the slag layer (S) is formed, thereby inducing the refinement of austenite grains and improving the toughness of the weld metal (WM). In addition, during welding, a copper di