高張力鋼 熔接이음 融合境界領域의 組織과 靭性評價에 對한 硏究 = A Study on Thoughtness Valuation and Structure of fusion Boundary Zones in a Welded for High tension Steel

다국어 초록 (Multilingual Abstract)

The fracture toughness in a high tension welded steel-has been examined with particular reference to HAZ microstructures. It is show that a wide variety of structure in the HAZ adjacent to fusion boundary through thickness is produced by Virtue of the different thermal histories experienced by each part in a multipass welded high tension steel. The HAZ microstructures can be classified into seven distinct kinds (named A, B, C, D, E, F and G) according to the microscopic constituent and grain size. Fracture toughness dependence on the HAZ microstructures is demonstrated by instrumented charpy dynamic ?? and static COD test on small specimens taken from the full thickness welded plate, the slit tip is carefully located in the HAZ adjacent to fusion boundary. The results make it clear that static COD test is more available for assessing fracture toughness dependence on the HAZ microstructues than instrumented charpy impact test. The martensite-bainitic HAZ microstructures (A, B and C) which are localized in the Vinicity of the weld toe fusion boundary impair most significantly of all the HAZ microstructures Furthermore, the emphasis must be placed upon the fact that martensitic-bainitic HAZ microstructure G tempered at relative high temperature during following welding process has excellent toughness, although the microstructure G seems to be similar to the microstructure of weld toe HAZ.