Evaluating Pipes from the Sinarskii Pipe Plant Based on their Content of Corrosion-Active Nonmetallic Inclusions

Abstract

To refine existing standards on the content of corrosion-active nonmetallic inclusions (CANI) in semifinished products, the Sinarskii Pipe Plant has made a study of the change in the density and shape of CANI from the semifinished product to the finished pipe. The study was performed on three heats having a CANI density within the established norm (no more than 2 inclusions/mm2) and on six specimens with a CANI density greater than 2 inclusions/mm2. Researchers followed the change in inclusion density in relation to the degree of deformation of semifinished products of steel 20-PKS made by the Volga Pipe Plant. The semi-finished products were 120 and 156 mm in diameter and were used in pipe production. An analysis of the study results showed that CANI density in the finished pipe is no greater than 2 inclusions/mm2 if the CANI in the semifinished product are uniformly distributed, their average density is no greater than 2 inclusions/mm2, and their maximum density is no greater than 4 inclusions/mm2. It was determined that CANI density is not affected by the degree of deformation of the semifinished product.