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°C to 500°C) 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.
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