Thixomet Ltd. (St. Petersburg, Russia):

A. A. Kazakov, Dr. Eng., Prof., Head of the Metallurgical Expertise Laboratory, e-mail: kazakov@thixomet.ru
D. V. Kiselev, Technical Director

JSC Vyksa Steel Works (Vyksa, Russia):

V. A. Murysev, Chief Specialist of the Engineering and Technology Center

Using an example of the quality assessment of welded pipe joints made of steel 09G2S, the method of processing the results of factory expert opinions has been developed to interprete the origin of non-metallic inclusions detected in the defects of a welded joints. Thermodynamic calculations have been made to assess the possible indigenous origin of these inclusions, the results of which are summarized in the form of radar diagrams of five clusters, which combine similar deoxidation products. According to the same method, more than 136 actual inclusions found on dozens of welded joints specimens are combined in 7 clusters. After a comparative analysis of these two types of radar diagrams, the origin of all real inclusion clusters was determined, three of which are predominantly indigenous and the other ones are predominantly exogenous. None of the clusters contains only indigenous inclusions. Several of the inclusions of one of the clusters contain pure exogenous MgO inclusions. The sources of inclusions in weld discontinuities are conglomerates consisting of exo-indigenous or indi-exogenous inclusions, which were torn off from the refractory surface. The method is implemented as a Thixomet PRO plug-in and allows to automate the process of metallographic conclusions generation under conditions of factory practice, as well as to accumulate all information in the database for subsequent processing and analysis.

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