308 系溶接金属の硬さ・組織に及ぼす溶接熱サイクルの影響

概要

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Changes of the metallurgical and mechanical properties, in the root pass weld metals accompanied with the repeated welding heat cycles of the multi-layer submerged arc welding, are studied. The obtained results are as follows. 1) The first and the second time welding heat cycle do not increase the hardness for the root pass weld metal, and the hardnesses increase from Hv150 to Hv190 between the third and the sixth time welding heat cycle. 2) Cooling rates down to 500℃ for the first time and the second welding heat cycle are 24℃/s and 5.9℃/s, cooling rate decreases till 1.5℃/s for the sixth welding heat cycle. 3) Precipitates are formed in the δ ferrite along δ ferrite-austenite boundaries, and the precipitates grow up to about 1000Å in size. 4) Fine precipitates, which diameter are hundreds Å, are formed in the austenite matrix, and the dislocations in the austenite matrix are fixed by these fine precipitates. 5) Dislocation densities in the austenite matrix are increased from (10)^8/(cm)^2 to 2×(10)^9/(cm)^2 by the released strain accompanied with the six times repeated welding heat cycles.
社団法人溶接学会の論文
1983-01-05