Comprehensive study of characteristic signs of defects detected during magnetic powder control at the final stage of production of seamless hot‑rolled pipes

Abstract

Defects on the outer surface of seamless hot‑rolled steel pipes are formed both as a result of the defects’ transformation in the surface and macrostructure of the initial workpiece, and due to non‑compliance with the rolling technology. Timely detection of defects and elimination of the causes of their formation, allows you to get high‑quality products with high operational reliability. Detection of violations of technology, control of the technological process, carrying out metallographic studies allow classifying defects and establishing the nature and causes of their formation.The article presents the results of a metallographic study of a defect on the outer surface of a hot‑rolled seamless pipe. The genetic and morphological signs of the defect were determined. Descriptions of the appearance of the defect, the microstructure in the defect zone are given. A comparative analysis of the defect detected during magnetic powder control with defects on experimental pipe blanks with artificial defects was carried out. Based on the data obtained, the causes of the defect formation are determined, its classification is given.

Keywords

• metal
• defect
• seamless steel pipe
• steel‑melting captives at mark
• mechanical damage
• mark
• microstructure
• causes of formation
• reagent “nital”
• morphological and genetic signs
• defects’ transformation