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KR-20260064505-A - EGW welding system and welding method for high heat input welding in LPG or ammonia carriers

KR20260064505AKR 20260064505 AKR20260064505 AKR 20260064505AKR-20260064505-A

Abstract

A high heat input EGW welding system for an LPG or ammonia carrier and a welding method thereof are disclosed. The high heat input EGW welding system for an LPG or ammonia carrier according to the present invention includes a welding power supply that supplies power for performing welding, a feeder that supplies a welding wire used for welding using power supplied from the welding power supply, and an EGW welding carriage that performs welding through the power supplied from the welding power supply and the welding wire supplied from the feeder.

Inventors

  • 손주환
  • 김병철
  • 장길수

Assignees

  • 에이치디한국조선해양 주식회사
  • 에이치디현대중공업 주식회사
  • 에이치디현대삼호 주식회사

Dates

Publication Date
20260507
Application Date
20250910
Priority Date
20241031

Claims (10)

  1. In an EGW (Electro Gas Welding) welding system for performing high-heat input welding on the hull or tank structure of an LPG or ammonia carrier, A welding power supply that supplies power to perform welding; A feeder that supplies welding wire used for welding using power supplied from the above welding power source; and, EGW welding carriage that performs welding using power supplied from the welding power source and welding wire supplied from the feeder; A high heat input EGW welding system for LPG or ammonia carriers, characterized in that the welding power source is set to a Direct Current Electrode Negative (DCEN) polarity so that arc electrons are transmitted to the welding wire rather than the base material.
  2. In paragraph 1, The above welding power source is, A high heat input EGW welding system for LPG or ammonia carriers, characterized by further including a waveform control function to reduce irregular arcs and spatter that may occur depending on the polarity of the direct current cathode (DCEN).
  3. In paragraph 2, The above welding power source is, A high heat input EGW welding system for LPG or ammonia carriers characterized by adjusting the switching frequency in the range of 10 kHz to 100 kHz.
  4. In paragraph 1, The above feeder is, A high heat input EGW welding system for LPG or ammonia carriers, characterized by adjusting the feed speed so that the value obtained by dividing the welding current by the feed speed is 16 to 20.
  5. In paragraph 1, A high heat input EGW welding system for LPG or ammonia carriers, characterized in that the diameter of the welding wire is 1.0 mm to 1.4 mm.
  6. In paragraph 5, A high heat input EGW welding system for LPG or ammonia carriers, characterized in that the value obtained by dividing the cross-sectional area of the welding wire by the surface area is 0.3 or less.
  7. In an Electro Gas Welding (EGW) welding method for performing welding on the hull or tank structure of an LPG or ammonia carrier using a high heat input method, A high heat input ESW welding method for LPG or ammonia carriers, characterized by applying a welding power source set to a Direct Current Electrode Negative (DCEN) polarity so that arc electrons are transferred to the welding wire rather than the base material.
  8. In Paragraph 7, The above welding is, A high heat input EGW welding method for LPG or ammonia carriers, characterized by being performed with a waveform control function applied to reduce irregular arcs and spatter that may occur depending on the polarity of the DC negative electrode (DCEN).
  9. In paragraph 8, The above waveform control function is, A high heat input EGW welding method for LPG or ammonia carriers, characterized by including a switching frequency set in the range of 10 kHz to 100 kHz.
  10. In Paragraph 7, The above welding is, A high heat input EGW welding method for LPG or ammonia carriers, characterized by being performed while adjusting the feed speed so that the value obtained by dividing the welding current by the feed speed is 24 or more and 35 or less.

Description

High heat input EGW welding system and welding method for LPG or ammonia carriers The present invention relates to a high heat input Electro Gas Welding (EGW) welding system for LPG or ammonia carriers and a welding method thereof. More specifically, the invention relates to a high heat input EGW welding system and a welding method thereof that can improve the impact toughness of the fusion line and the heat-affected zone by applying a welding power source with DCEN polarity to concentrate arc electrons on the welding wire and controlling the feed speed and waveform. Generally, since the hull and tank structures of LPG or ammonia carriers must maintain stability even in cryogenic environments, high-quality welding is essential for joining these components. Various welding methods are used for these vessels, including Flux Cored Arc Welding (FCAW), Submerged Arc Welding (SAW), Electro Gas Welding (EGW), and Electro Slag Welding (ESW). In particular, at shipbuilding sites, the use of automated high-heat input welding processes such as SAW and EGW, which can be automated, is gradually expanding to ensure work efficiency and quality. However, high-heat input automated welding processes present a problem in that the large heat input makes it difficult to control the heat of the fusion line and the surrounding heat-affected zone (HAZ) formed during welding. In particular, if the arc heat source is excessively concentrated on the base metal or if molten metal remains uncooled, the microstructure may coarsen, leading to a decrease in impact toughness. This problem can result in rejection at the 5mm or 10mm position during impact tests conducted according to classification society standards, and poses a greater burden on quality assurance, especially for LPG or ammonia carriers that require cryogenic environments below -60℃. Therefore, there is a need for a technical alternative that can stably secure impact toughness of the weld through localized heat and cooling control while maintaining the productivity and efficiency of high-heat input automated welding. To address these issues, various technical approaches are required to ensure cryogenic impact toughness even when applying automated high-heat input welding processes. For example, in the EGW process, by applying Direct Current Electrode Negative (DCEN) polarity to ensure that arc electrons are transferred toward the welding wire rather than the base metal, excessive penetration of welding heat into the base metal can be prevented, and heat input can be concentrated on the wire. Additionally, by optimizing the feed rate and welding waveform to control heat input and ensure arc stability, microstructure coarsening in the fusion line and heat-affected zone can be suppressed, thereby improving impact toughness. In the case of the ESW process, by controlling the ratio between the feed speed and the welding current within an appropriate range, excessive heat input can be prevented and the thermal impact on the weld area minimized. Furthermore, the system can be configured to enable stable feed through a digital feeder and dual roller drive. This enables the realization of an automated process applicable to vertical welding of extremely thick materials, while simultaneously ensuring uniformity in welding quality and productivity. In addition, copper quenching technology that selectively cools the relevant areas is required as a method to fundamentally resolve the problem of impact toughness degradation in the fusion line and heat-affected zone. In particular, by arranging independent cooling channels centered on both sides of the fusion line formed during welding and optimizing the spacing between cooling channels by considering the beveled surface opening width and the distance between fusion lines, rapid cooling near the HAZ after welding can be induced and microstructure formation promoted. Through this, it is possible to secure toughness exceeding classification society standards in the F/L to F/L+1mm section, where impact toughness is most vulnerable, and effective thermal control can be achieved while preventing unnecessary cooling of the molten metal. Therefore, there is an urgent need to develop high-heat input welding technology that can ensure welding quality suitable for cryogenic environments while simultaneously satisfying the productivity of automated processes. FIG. 1 is a configuration diagram of a high heat input EGW welding system for an LPG or ammonia carrier according to one embodiment of the present invention. FIG. 2 is a conceptual diagram comparing cases where the welding power applied to the EGW is set to the polarity of the conventional DCEP and the DCEN of the present invention, respectively. Figure 3 is a graph comparing the switching frequency of a conventional welding power supply applied to an EGW and the switching frequency of the welding power supply of the present invention. Figure 4 is a graph comparing the ratio of the conventional f