高温酸化スケールのブリスタリングの成長過程に及ぼす窒素の影響

摘要

Blistering occurs when oxide scale swells during oxidation at high temperatures. Blistered scale causes surface defects when rolled. The present study investigated the effect of nitrogen on blister growth when steel is oxidized at high temperatures, and drew the following conclusions. Atmospheric conditions before oxidation affect blister growth. Blisters nucleate but do not grow, when a steel sample is held in Ar gas or in vacuum before oxidation. Blisters inflate when a steel sample is held in N_2 gas before oxidation. The gas inside the grown blisters is mainly N_2 gas. The steel surface is nitrided in N_2 gas at high temperatures. It is deduced that the steel surface is nitrided before oxidation, and the nitrogen component causes blister growth upon its release as N_2 gas at the scale/steel interface.%熱間圧延中に鋼材表面の酸化スケールが剥離して膨れるプリスタリングという現象がある。プリスターが発生した状態で鋼材が圧延されると表面疵の原因となることが知られている。表面疵を防止するためにも，ブリスターの発生原因を理解することが重要である。