1995 Volume 13 Issue 2 Pages 276-282
The purpose of this paper is to investigate the impact characteristics of the weld metal produced using various welding parameters by directing our attention to the electroslag welding (ESW). This is one of high heat input welding processes which are usually applied for the manufacture of four side thick plate box column for general multistoried buildings, ets.
In particular, this paper clarified the impact characteristics of ESW weld metal in its both center [Core (C) ] and peripheral locations [Rim (R) ]. The test results obtained are summarized in the following.
(1) The impact test value (vE) of weld metal in its core (C) is lower than those in the rim (R) locations.
(2) As for the change of vE value according to the change in welding heat input (at six levels of Q=10.1 to 126.7 kJ/mm), the vE value of both C and R locations generally decreases according to the increase of heat input. However, vE. value in the core (C) is always lower than those in R locations.
(3) Regardless of the changes in steel types (such as TMCP and SM490A), flux types (three molten types) and amount of flux supplies (0.5 N or 0.7 N), the vE value of C location is always low without any significant change. Futhermore, the vE value decreases according to the change in shielding gas types from Argon gas (Ar) to air and then to oxygen (O2) in this order.
(4) The formation of grain boundary ferrite in the coarse prior austenite (γ) boundaries and that of fine acicular ferrite inside the grains are mainly noticed in R locations as the result of the observation of microstructure. However, the formation of grain boundary ferrite in the fine prior γ boundaries and that of coarse ferrite inside the grains are densely noticed in C locations.
(5) As the result of the observation of impact fractures with a scanning electron microscope (SEM), it is found that the facet size of weld metal in C locations is actually large which matches the low vE value.
Moreover, selective fractures propagation along the grain boundary ferrite in the core of the impact fracture is found as the result of the observation on both two faces of structure at the same time. This indicates that the low vE value in C locations has been caused by the existence of both dense grain boundary ferrite and coarse ferrite inside the grains.
