Якість металу котельної трубної заготовки виробництва ПАТ «Дніпровський металургійний комбінат»

• Date: 2023
• Main Authors: Опришко, Л.В., Головняк, Т.В.
• Format: Article
• Language: Ukrainian
• Published: Physico-technological Institute of Metals and Alloys 2023
• Subjects: злиток безперервного розливання; котельна трубна заготовка; макроструктура; технологічна пластичність; осьова ліквація; точкове забруднення крайове; залишки литої структури; жароміцність
• Online Access: https://www.metalsandcasting.com/index.php/mcu/article/view/182
• Journal Title: Metal and Casting of Ukraine

The article presents results of comprehensive studies of qualitative indicators of metal of the hot-rolled tube billets manufactured by PJSC "Dneprovsky Iron & Steel Integrated Works" from continuously cast ingots of ‘20’ steel grade taken from 2 heats of oxygen-converter smelting. The studies were performed according to current standards and methods. The results of these studies have made it possible to assess ability of the production technology used at this enterprise to produce high-quality tube billets for the manufacture of boiler tubes designed for steam boilers and pipelines operating at high and supercritical steam parameters. It has been established, that the current steelmaking and casting technology used at the Works does not fully ensure the manufacture of boiler tube billets in accordance with requirements of regulatory documents and requires further study and improvement. Axial segregation and a light band (contour) were revealed in the macrostructure of metal of the tube billets the degree of development of which exceeded the established norms, as well as unacceptable edge point pollution. It was established that presence of the edge point pollution along with non-metallic inclusions in the billet metal exceeding the established norms result in formation of unacceptable laminations in locations of the contaminants expanded by rolling the tube metal. Metal macrostructure of the hot-rolled tube billets under study features presence of cast structure residues negatively affecting formation of the proper microstructure of metal of the boiler tubes manufactured from these billets and, accordingly, the tube service properties. The necessity of increasing norms of sampling from hot-rolled continuously cast tube billets manufactured by PJSC "Dneprovsky Iron & Steel Integrated Works" as well as the necessity of introducing requirements to the degree of development of the cast structure residues observed in the metal macrostructure of these billets previously not used in regulatory documents were shown. The obtained study results are of great scientific and practical value. They have served as a basis for development of a modern Technical Specification for hot-rolled carbon steel boiler tube billets manufactured by PJSC "Dneprovsky Iron & Steel Integrated Works" as well as for working out and implementation of measures to improve the technology of production of boiler tube billets at this enterprise taking into account requirements of the developed Technical Specification. This will allow PJSC "Dneprovsky Iron & Steel Integrated Works" to produce competitive high-quality tube billets and reduce shortage of the carbon steel tube billets in Ukraine.