Nitrogen Distribution on Rapid Solidification in LASER Welded Duplex Stainless Steels.

Simulation of Microstructure Formation Process in Fe-23Cr-6Ni-3Mo-0.1N Alloy Using Multiphase Field Method

“…The change in growth behavior around 1350 K corresponds to the γ phase formation in the grains. This result nearly corresponds to that of the previous study 4) , in which the cooling rates during laser welding were changed. In addition, the calculated average concentration of N in the δ phase decreased with an increase in the cooling rate by image analysis), while the morphology of the γ phase also appeared to be nearly similar to that obtained by the experiment.…”

“…However, this requires the acquisition of substantial amounts of experimental data for each alloy, and a statistical analysis of the data must also be performed. In addition, the composition profile could not be predicted in previous studies, although the nitrogen content in the ferrite phase significantly affects the pitting corrosion resistance in duplex stainless steels 4) .…”

Effects of Welding Velocity and Short Time Post Weld Heat Treatment on Precipitation of Austenite in Laser Beam Welds of Duplex Stainless Steels

“…二相ステンレス鋼は，従来よりも優れた機械的性質及び 耐食性を有することから，化学プラント，海洋関連装置， 熱交換器など，種々の腐食環境にさらされる設備，機械に 幅広く使用されている．さらに，近年では水門等のインフ ラ設備等に適合するため，経済性とのバランスをとれる新 鋼種である省合金二相ステンレス鋼なども開発され実用化 されている [1][2][3][4][5] ．二相ステンレス鋼を構造材料として用いる 場合の課題として，溶接過程において溶接部での相比が崩 れ，とくに入熱量が大きい場合，著しくフェライト相量が 増加することから，鋼種の特性が劣化する可能性もあり， 十分な機械的特性，耐食性が発揮されない可能性があるこ とが挙げられる [6][7][8][9] ．これらの現象に関して議論した例には， 従来法による二相ステンレス鋼の溶接部に置いて，置換型 元素らは母材のような分配を起こさず，オーステンナイト 相の成長は窒素濃度から律速されるとの報告がある [10][11][12] ．さ らに，窒素を添加した溶接材及び窒素雰囲気での溶接も検 討されている [3][4][5][6][7][8][9][10][11][12][13][14][15] ．しかし，近年，実施工への応用が期待さ れているレーザ溶接法を種々の二相ステンレス鋼に適用し た事例については未だ十分には検討されていない [16][17][18] When conventional arc welding methods welded various kinds of duplex stainless steels, it is well known that the ferrite phase was enriched in welds. Notably, in the case of laser beam welding (LBW), due to high energy density and welding velocities, the phase balance might be remarkably changed from that in the base material.…”

Morphological Characteristics of Widmanstätten Austenite Formed in Laser Beam Welds of Lean Duplex Stainless Steels

“…In the previous research of welds in duplex stainless steel, the austenite precipitated at welds is mainly composed of nitrogen and also affects the growth of Widmanstätten austenite 2,3) . Meantime, the shape characteristics of the Widmanstätten structure have been described in many studies are primarily classified as elongated needle-like.…”