ON RESEARCHING THE REASONS OF A DECREASE OF DUCTILE CHARACTERISTICS OF PIPELINE STEEL SPECIMENS DURING CTOD TEST
The paper considers the pipeline steel specimens with different values of CTOD. A number of metallographic structure researches by optical microscopy and scanning electron microscopy were carried out. Chemical compositions of matrix and nonmetallic inclusions were determined. It was established that the chemical composition, presence and distribution of nonmetallic inclusions in specimen center part are the main factors that determine the ductile characteristics.