KR-20260064225-A - Laser welding device for LNG cargo holds and laser welding system for LNG cargo holds including the same

KR20260064225AKR 20260064225 AKR20260064225 AKR 20260064225AKR-20260064225-A

Abstract

A laser welding device for an LNG cargo tank and a laser welding system for an LNG cargo tank including the same are disclosed. The laser welding device for an LNG cargo tank according to the present invention comprises a body portion forming a path for a laser beam, a coaxial camera portion provided on one side of the body portion and capturing image information on the same axis as the laser beam performing welding, and a dichroic mirror provided on the laser beam path of the body portion, which transmits the laser beam and reflects visible light and light of a specific wavelength range to transmit to the coaxial camera portion.

Inventors

박정원
조영호

Assignees

에이치디한국조선해양 주식회사

Dates

Publication Date: 20260507
Application Date: 20241031

Claims (8)

A body part that forms the path of a laser beam; A coaxial camera unit provided on one side of the above-mentioned body part and capturing image information on the same axis as the laser beam performing welding; and, A laser welding device for an LNG cargo tank comprising: a dichroic mirror provided on the laser beam path of the body portion, which transmits the laser beam and reflects visible light and light of a specific wavelength range to transmit to the coaxial camera portion.
In paragraph 1, The above body part is, A first extension part extending a certain length from a laser receiver that receives a laser beam, and The bend where the path of the received laser beam is changed, and A laser welding device for an LNG cargo tank, characterized by including a second extension portion that forms a certain angle with the first extension portion and extends a certain length from the curve portion in the path direction of the modified laser beam.
In paragraph 2, A laser welding device for an LNG cargo tank, characterized in that the above-mentioned coaxial camera unit is provided on one side of the above-mentioned second extension unit.
In paragraph 3, A laser welding device for an LNG cargo tank, further comprising a first reflective mirror provided in the above-mentioned bending section and reflecting the laser beam to change its path.
In paragraph 4, A laser welding device for an LNG cargo tank further comprising a second reflective mirror that reflects visible light transmitted to the coaxial camera side toward the image sensor side.
entity; A moving part that moves the above main body along a certain trajectory; and, A laser welding device provided on one side of the main body and moving together with the main body to perform laser welding; is included. The above laser welding device is, A laser welding system for an LNG cargo tank characterized by including: a coaxial camera unit provided on one side of the body of the above-mentioned laser welding device and capturing image information on the same axis as the laser beam performing the welding.
In paragraph 6, A laser welding system for an LNG cargo tank further comprising a dichroic mirror provided on the laser beam path of the body portion, which transmits the laser beam and reflects visible light and light of a specific wavelength range to transmit to the coaxial camera portion.
In Paragraph 7, A laser welding system for an LNG cargo tank further comprising a second reflective mirror that reflects visible light transmitted to the coaxial camera side toward the image sensor side.

Description

Laser welding device for LNG cargo holds and laser welding system for LNG cargo holds including the same The present invention relates to a laser welding device for an LNG cargo tank and a laser welding system for an LNG cargo tank including the same. More specifically, the invention relates to a laser welding device for an LNG cargo tank and a laser welding system for an LNG cargo tank including the same, which can track a welding line by acquiring image information on the same axis as the laser beam, thereby minimizing the occurrence of sensing distortion and error. Due to its characteristics, liquefied natural gas (LNG) must be stored and transported at cryogenic temperatures; to this end, ships or storage tanks used for storing or transporting LNG require highly reliable cargo tanks. The cargo tanks of LNG carriers are critical structures for safely storing and transporting cryogenic LNG. LNG carrier cargo tanks are classified into MOSS and membrane types. Inside membrane-type cargo tanks, membrane-shaped components are manufactured from metal materials such as Invar or stainless steel, and multiple panels are connected by welding. Conventional membrane welding methods have mainly applied traditional arc welding technologies such as TIG (Tungsten Inert Gas) or plasma welding. However, while TIG and plasma welding have the advantages of good weld quality and aesthetics, the welding speed is slow, resulting in low welding work efficiency. To address these issues, the introduction of laser welding technology has been considered. Laser welding offers advantages such as high precision and consistency, fast welding speeds, a small heat-affected zone, and low deformation. Automated laser systems can ensure uniform welding quality, and the use of high-energy-density laser beams can significantly improve welding speeds. However, there are still several technical challenges in laser welding of LNG cargo tank membranes. Major challenges remain, such as the difficulty of laser welding on metal surfaces with high reflectivity, precise laser beam control and positioning for large structures, ensuring welding quality for curved and corner sections, and real-time monitoring and quality control during the welding process. Specifically, LNG cargo tank membranes consist of very thin metal panels, so the welding depth and energy control must be very precise during laser welding. Otherwise, excessive welding may damage the membrane or reduce airtightness. In addition, optimization of the size and shape of the laser welding device is required, and due to the structural characteristics of the vessel, welding operations must be possible at various positions and angles. Therefore, developing a laser welding device specialized for welding the membranes of LNG cargo tanks and achieving high-quality welding through this is an important task in this technology field to increase the efficiency of the manufacturing process and ensure the stability of the cargo tanks. Meanwhile, since the laser beam of a conventional fiber laser welding device has a diameter of several hundred micrometers, welding must be performed through 'beam wobbling' when the gap size increases during membrane welding. Here, 'beam wobbling' refers to a method of rapidly moving the laser beam in a circular or straight line perpendicular to the weld seam. However, applying a wobble head to a laser welding device to implement 'beam wobbling' has disadvantages. The addition of motors and other components for wobbling increases the system's weight, making installation and relocation difficult and reducing productivity. Furthermore, the increased complexity of the system can affect maintenance and durability. Additionally, 'beam wobbling' increases welding time and can cause sagging during side and overhead welding of cargo tanks, potentially leading to quality issues. Therefore, there is a need to develop a laser welding system capable of responding to gap increases by increasing the effective cross-sectional area of the laser beam without configuring additional devices for 'beam wobbling' such as wobble heads and motors. FIG. 1 is a perspective view of a laser welding system for an LNG cargo tank according to one embodiment of the present invention. FIG. 2 is a front view of a laser welding device for an LNG cargo tank according to an embodiment of the present invention. FIG. 3 is a perspective view of a laser welding device for an LNG cargo tank according to an embodiment of the present invention. FIG. 4 is a perspective view of a laser welding device for an LNG cargo tank according to one embodiment of the present invention, viewed from another side. FIG. 5 is a configuration diagram illustrating a light homogenization section of a laser welding device for an LNG cargo tank according to an embodiment of the present invention. Figure 6 is an image comparing the cross-sectional profile of a typical laser beam with a profile in which the cross-sectional area of the ef