Abstract
The characteristics of inclusions and microstructure in heat-affected zones (HAZs) of steel plates with Ca deoxidation after high heat input welding of 400 kJ·cm−1 were investigated through simulated welding experiments and inclusions automatic analyzer systems. Typical inclusions in HAZs of steels containing 11 ppm and 27 ppm Ca were recognized as complex inclusions with the size in the range of 1~3 μm. They consisted of central Al2O3 and peripheral CaS + MnS with TiN distributing at the edge (Al2O3 + CaS + MnS + TiN). With increasing Ca content in steel, the average size of inclusions decreased from 2.23 to 1.46 μm, and the number density increased steadily from 33.7 to 45.0 mm−2. Al2O3 + CaS + MnS + TiN complex inclusions were potent to induce the formation of intragranular acicular ferrite (IAF). Therefore, the HAZ toughness of steel plates after high heat input welding was improved significantly by utilizing oxide metallurgy technology with Ca deoxidation.
Highlights
In recent years, the high heat input welding technology with the heat input larger than 400 kJ·cm−1 has been widely used for welding heavy steel plates in the areas of shipbuilding, architectural construction, etc
Characterization of Inclusions and Microstructures after Charpy impact tests. These specimens were polished and with analyzed by cross the inclusion. These heat-affected zones (HAZs) specimens were taken from the surfaces in parallel the fracture sections These specimens were taken from the surfaces in parallel with the fracture cross sections automatic analyzer system is consisted of scanning electron after Charpy impact tests. (IAAS)
The effect of Ca content on the number, size and composition of inclusions in the heat-affected zones (HAZs) of steel plates with Ca deoxidation was investigated based on the experimental study
Summary
The high heat input welding technology with the heat input larger than 400 kJ·cm−1 has been widely used for welding heavy steel plates in the areas of shipbuilding, architectural construction, etc. It is widely accepted that the oxide metallurgy technology is an effective method for the improvement of HAZ toughness of steel plates after high heat input welding [3]. Yang et al [1,4,5,6] have developed third-generation oxide metallurgy technology to obtain excellent HAZ toughness by inclusion control with Mg deoxidation They found that the formation of micro-meter inclusions and the nano-meter precipitates in steel plates can effectively promote the formation of IAF and restrain the growth of γ. The characteristics of inclusions and microstructure in HAZs of steel plates with Ca deoxidation are studied after high heat input welding of 400 kJ·cm−1. The mechanism of improvement of HAZ toughness after high-heat input welding by inclusion control with Ca deoxidation is illustrated
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