Effect of Calcium and Magnesium Addition on the Rolled Microstructure Grain Size of HSLA Steel

A new technology to obtain a fine-structured and high-toughness HAZ of HSLA steel for high heat input welding is developed using metallurgical thermodynamics, physical chemistry of metallurgy and material processing methods synthetically in this study. The effect of calcium and magnesium addition on the rolled microstructure grain size of HSLA steel was analysed. The results show that adding Ca and Mg elements into the rolled steel can accelerate the nucleation and refrain the grain growth, so the grains are refined. Almost every rolled experimental steel grain becomes finer after adding Ca and Mg elements. The range of the mean grain size is from 0.518 mm to 0.879 mm. When adding 5wt% Mg, the mean grain size is the smallest, 0.518 mm, while the biggest grain size is 1.011mm in rolled raw steel. The grain size in Mg 5wt% steel is refined by 48% in contrast with the rolled raw steel. Almost every rolled experimental steel grain becomes finer contrast with cast experimental steel.