局部予熱における冷却時間t_<8/5>と熱因子の予測式の検討

概要

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Preheating is performed to prevent cold cracking in steel constructions. Preheating produces a good effect on cooling times, which are t_<8/5>(cooling time from 800℃ to 500℃) related to the maximum hardness at HAZ, or which are t_<200>, t_<150>, t_<100>(t_θ : cooling time from the solidification to θ) connected with the thermal factor. In the welding field, a whole member can not be preheated uniformly, and then local preheating near the weld line is generally performed. This report deals with local preheating and welding procedures of a butt joint and a corner joint. Predicted values of cooling times have been compared with the experimental data. The predicted values have been obtained by theoretical formulae. The results are summarized as follows : (1) Relation between cooling time and thermal factor, (ΣD・Δt)_<100> has been investigated. The thermal factor is correlated most closely with cooling time t_<150>.(2) The predicted values of cooling time t_<8/5> and thermal factor, (ΣD・Δt)_<100> have given good agreement with the experimental values.
1991-08-05