Abstract
Due to various environmental regulations, the demand for natural gas, i.e., a clean energy, is expected to increase continuously. In terms of efficient storage and transportation of natural gas, liquefied natural gas has an advantageous volume of 1/600 compared to natural gas, but the materials that can be used at a cryogenic temperature of −163 °C are limited. A 9% nickel steel is a material recommended by IMO through IGC. It has excellent mechanical properties compared to other cryogenic materials, but its use has been limited due to its disadvantages in arc welding. Therefore, the main topic of this study is the automatic welding of 9% nickel steel using fiber laser and its purpose is to predict the welding deformation during fiber laser welding. First, an investigation was conducted to find the fiber laser welding heat source. A model that can cover all the models in prior studies such as curve, exponential, conical, conical-conical combination, and conical-cylinder combination models was proposed and the heat source model was constructed in a multi-layer format. Heat transfer analysis was performed using the ratio of a heat source radius and heat energy of each layer as a variable and the pass or failure of a heat source was determined by comparing the analysis results to the experimental results. By changing the variables in conjunction with the optimization algorithm, the main parameters of a passed heat source model were verified in a short period of time. In addition, the tendency of parameters according to the welding speed was checked.
Highlights
Due to global warming and environmental pollution, regulations on fossil fuels are becoming stricter
The International Marine Organization (IMO) specifies the materials that can be used at the liquefied natural gas (LNG) boiling point in the IGC Code, and these materials are STS304L, STS316L, Invar (36% nickel steel), high manganese steel, and 9% nickel steel [3]
The welding heat source model is configured as an integrated heat source model that can cover all existing laser heat source models
Summary
Due to global warming and environmental pollution, regulations on fossil fuels are becoming stricter. The main purpose of this study was to predict the amount of welding deformation and deformation patterns through finite element analysis when welding 9% nickel steel, i.e., a cryogenic material, using a fiber laser. Kim proposed a model of a circular cone shape as a welding heat source, performed finite element analysis, predicted a fusion zone, and verified it through an experiment [20]. A common characteristic of prior studies is that a heat source was estimated based on the shape of a weld bead and it was used as the heat source for a finite element analysis model. AsFthore tfhirisst ssttuepdyt,oadefirbivere ltahseegr ewneerldalinwgemldaincghihneeawt siothuracecaepquacaittiyono,fth5ekpWurpwoasse uosfed. thisMsityuadcyhiwwaesldtoindgeeriqvueipthmeesnhtawpeasouf saewd ealnddinigt choenastisstosuorfcea ulassienrgwaewldeilndginogschilelaattosro, uorpcteical mmwawfaetooewssta2rsddiryee.tl0eeadtts4tillstfhemnteotkovw4eghmu/We0a0ineaml,0tto,xhdncapvμiapodnnnaaemnecd.rdowrdtihi,rmetmooaiiNhstglrpneselk2htedanhferirwot,nexde,tacghpdaewtnaeghesalderrtenulfoileceumdgshehnsielteenieighdolaongltefwetnhtarhfsfwe,srwzuoeareoaaaeussaenstirdspsfioecsphnorx1eoooewme4urwtrzd8efraa.oo.cncsd8anBerttiiimeemyunvr0saseet◦imFddind.imagiig,vDnuawtutaihdsshudtrheeeeraiatindinlhn2nfSegod.edEguccTMtstrhatshhhiahplaneeteendrigposahgheeipyfceipxeoinoteanaptuftgdhttierdthsrteesawieohi.oatmaueeaumTtalrseesrhcesncprm6eetoeateenu,metrereia,tnrdnohmcttaotifeetoonfa,otphfnt1fof1ohoeoai5r.vprewl5oyLeteepdmiesa/amtilreciscam/fchwa.hyoamliTeclnallruaaihhss.nsyyysee4,fi,Bseenaowaatxrrto,feneat1mddh6s source model was sought by linking the global optimization algorithm and finite element analysis
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