Effect of Calcium Addition on the Cast Microstructure of a Kind of HSLA Steel

The rapid development of the large steel structure brings a great opportunity for steelmaking industry. The steel plates not only have the strength and toughness but also can withstand the high energy input welding. Using the calcinm oxide of high melting-point and high stability to pin the grain boundaries is an effective method to improve the welding performance of the structure steel. This experiment takes the HSLA steel as the research object, the second phase particles which would not be dissolved or aggregated at high temperature will be expected by means of adding calcium into the steel in the form of Ca-Si alloy. The effect of calcium addition on the cast microstructure of HSLA steel was analysed. The results show that the cast microstructure is mainly consist of lamellar and acicular ferrite, a small amount of pearlite and bainite. Compared with the original steel, there are acicular ferrites presenting in the experimental steel after adding 5 wt% Ca, which are the microstructure that we hope to get. The acicular ferrite will have a positive impact on the mechanical properties of the subsequent rolled steel.