St.Petersburg State Polytechnical University (St.Petersburg, Russia):

A. Kazakov, kazakov@thixomet.ru

D. Kiselev

O. Pakhomova

Standards currently used to assess the quality of steel plate for pipelines are out of date and cannot be used for this purpose. The motorized hardware-software complex “Thixomet SmartDrive” has been developed and installed in dozens of enterprises and companies to provide an objective quantitative estimation of all types of structural inhomogeneity in modern pipeline steels, such as microstructural banding, general anisotropy, blocks of bainite with lath morphology and centerline segregation.

All developed standards are either unique and have no analogues (general anisotropy and blocks of bainite with lath morphology), or are compatible but exceed in efficiency and objectiveness of quality estimation: current Russian (GOST 5640-68) and foreign (ASTM 1268, GB/T 13298) standards. Our work has demonstrated that structural heterogeneity evaluated by the volume fraction and size of elongated areas of bainite blocks with lath morphology parallel to the rolling direction will adequately describe mechanical properties obtained from tensile and impact tests of pipeline steels with yield strength from 485 up to 625 N/mm².

The “structure - properties" relationships determined can be used as a background for developing a quality estimation system that includes acceptance tests for steel products between suppliers and consumers of pipeline plate, and also for the improvement of production technology.

1.Shigeaki Ogibayashi. Advances in Technology of Oxide Metallurgy. Nippon Steel Technical Report. April 1994. No. 61. 76 p.

2. Novosti Metallurgii po Stranam i Regionam. Kitai. Novyi tolstolistovoi stan kompanii Xoangtan (Iron and Steel News of the World. China. New heavy plate mill of Xiangtan). Chernye Metally - Ferrous metals. 2010. № 12. p 10.

3. Saltykov S. A. Stereometricheskaya metallographiya (Stereometric metallography). Мoscow. Metallurgiya. 1970. 376 p.

4. Kazakov A. A., Kiselev D. V., Andreeva S. V., Chigintsev L. V., Golovin S. V., Egorov V. A., Markov S. I. Razrabotka metodiki kolichestvennoi otsenki mikrostrukturnoi poloschatosti izkolegirovannykh trubnykh stalei s pomoshchyu avtomaticheskogo analiza izobrazheniya (Development of the technique for quantitative evaluation of microstructural banding for low-alloyed pipeline steels using automatic image analysis). Chernye Metally - Ferrous metals. 2007. № 7-8. p 31-37.

5. Pratt W. K. Tsifrovaya obrabotka izobrazheniy (Digital Image Processing). Moscow. Mir. 1982. Book 1. 312 p. (Translation from English: A. Willey – Interscience Publication. John Willey and Sons. 1978).

6. Malakhov N. V., Motovilina G. D., Khlusova E. I., Kazakov A. A. Strukturnaya neodnorodnost i metody ee snizheniya dlya povysheniya kachestva konstruktsionnoi stali (Structural inhomogeneity and methods for its lowering for quality improvement of structural steels). Voprosy Materialovedeniya – Material Science Problems. 2009. № 3 (59). p. 52-64.

7. RF Patent № 2449055. Sposob issledovaniya struktury trubnykh stalei (The method of examination of pipeline steels structure).

8. Kazakov A. A., Kazakova E. I., Kiselev D. V., Motovilina G. D. Razrabotka metodov otsenki mikrostrukturnoi neodnorodnosti trubnykh stalei (Development of the methods for evaluation of microstructural inhomogeneity of pipeline steels. Chernye Metally – Ferrous metals. 2009. № 12. p. 12-15.

9. Kazakov A. A., Chigintsev L. V., Kazakova E. I., Ryaboshuk S. V., Markov S. I. Metodika otsenki likvatsionnoi polosy listovogo prokata (The technique for evaluation of centerline segregation in rolled plate). Chernye Metally - Ferrous metals. 2009. № 12. p. 17-22.