送電鉄塔用鋼管 STKT590 溶接熱影響部の溶融亜鉛めっきぜい化に及ぼす微量ボロンの影響

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This paper represents the effect of boron on liquid zinc induced embrittlement in the heat affected zone of STKT590. To determine the susceptibility toward liquid metal zinc induced embrittlement at a fracture time of 400s (S_<LM-400>), 64 kinds of carbon steel whose boron content was varied in 4 levels, have been tested by the notched-bar-tensile test method. S_<LM-400> is reduced linearly if a small amount of boron, less than 4 mass ppm, is added. In the case of more than 4 mass ppm of boron, S_<LM-400> is minimized to 10 to 20%. Therefore, boron is considered to intensify liquid zinc induced embrittlement, because the ferrite ratio at the grain boundary is reduced. Additionally, we reconsidered the JIS regression formula of carbon equivalent for susceptibility liquid zinc induced cracking (CEZ). As a result, a modified formula of CEZ was suggested to revise the JIS formula. This formula has been considered to be effective in predicting resistance to zinc induced cracking in large steel structures.
社団法人日本鉄鋼協会の論文
1993-09-01