Microstructure and Properties of Hot Rolled X65 Pipeline Steel Strip Produced by Tangsteel

The microstructure and mechanical properties were studied on X65 pipeline steel produced by Tangsteel using methods of optical microscope, SEM, TEM and tensile tests and so on. Impurities in the steel and impact toughness were researched by experiments. The results show that microstructure of X65 pipeline steel strips is fine and more homogeneous, the grains of ferrite which is about 6 mu m are acicular. Finer M/A island structure and deteriorated pearlite are dispersed in the lathing of acicular ferrite. The impurities in steel are mainly sphericity, subspheticity of silicates and sulfuret, and the size of most impurities is smaller than 4 mu m. there was second phase partical precipitating in the ferrite grain or on the ferrite boundary of finished strip. The strength and toughness of X65 pipeline steel strips are high because of the fine microstructure and low quantity of deleterious components and impurities.