Excellent heat affected zone(HAZ)toughness technology improved by strong deoxidizers(ETISI)technology has been developed by Baosteel.In the deoxidation process of molten steel by adding strong deoxidizers,the formation of micrometer inclusions and nano-meter precipitates in steel plates can be effectively controlled by a precise control of oxygen concentration.In the welding process with a high-heat input,the formation of acicular ferrite can be selectively promoted with the aid of the micrometer inclusions;the growth of γ grains can also be selectively restrained by the pinning effect of the nano-meter precipitates.After welding with a high-heat input of 400 kJ/cm,excellent HAZ toughness can be obtained in the steel plates with both of the above microstructures,and the average absorbed energy is greater than 200 J for the V-notch Charpy impact test at-20℃.
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