Poleschuk M. Investigation of the process and development of technology of electroslag casting of high-pressure flange stop valve bodies

Thesis for scientific degree of Candidate of Technical Sciences by specialty 05.16.02: Metallurgy of ferrous and non-ferrous metals and special alloys, the E.O. Paton Electric Welding Institute of the NAS of Ukraine, Kyiv, 2010. The work is devoted to the investigation of electroslag process to develop the technology of electroslag casting of high-quality billets of stop valve bodies with flanges at the ends of branch pipes for Christmas tree method production of oil and natural gas at pressure of up to 70 MPa. The regularities of electroslag process of shape formation and casting of billets of intricate geometry were experimentally investigated in the work. Using methods of mathematical and computer modeling, the nature of distribution of density of Joule heat sources in slag pool was studied at all stages of melting. The redistribution of sources of heat generation in the slag volume was found in melting-on of branch pipes in electroslag casting with melting-on. The metallographic examinations showed the high degree of homogenization of metal near the fusion line resulting in high increase in impact strength of metal of this zone. As a result of investigations, carried out in this work, two variants of technology of a serial production of billets of stop valve bodies with flanges at the ends of branch pipes were developed: - ESC of all-cast billets of steels of different classes, including corrosion-resistant steels; - ESC of billets with melting-on of branch pipes with flanges of medium-carbon alloyed steels. Key words: high-pressure equipment for oil and natural gas production, billets of stop valve bodies with flanges, electroslag casting of intricate billets, electroslag casting with melting-on, mechanical properties of metal, high reliability.