PSI - Issue 36

Valentin Ilyushenko et al. / Procedia Structural Integrity 36 (2022) 100–105 2 V. Ilyushenko, T. Maydanchuk, E. Lukianchenko, S. Kozulin, S. Marynenko / Structural Integrity Procedia 00 (2021) 000 – 000 1. Introduction At present, in the world's steelmaking, oxygen converters and arc steelmaking furnaces (ASF) are mainly used. The open-hearth method of steel production currently is uncompetitive, which is confirmed by the almost complete decommissioning of open-hearth furnaces. Analysis of literature data conducted by Belkovsky et al. (2003) showed that the share of electric steel was increased from 30 to 45% over the last 20 years. It is expected that the share of electric steel in total production will further increase, primarily due to developing countries demands. In order to intensify the melting in the ASF, auxiliaries and techniques are used, providing additional heat input into the electric furnace. In the construction of ASF, this is achieved through the use of cast-welded copper water cooled assemblies (Fig. 1a), consisting of a jetbox, a removable jetbox panel, a chamber (Fig. 1b) and a nozzle, as shown by Ilyushenko et al. (2019). A mixture of oxygen and natural gas is fed through a copper chamber. The chamber body has channels for water cooling under working pressure of 6… 8 atm. 101

а

b

Fig. 1. The design of the copper water-cooled unit (a) and the appearance of the gas-oxygen chamber (b).

However, during operation, cracks, chips, dents are formed on the surface of the chambers, which leads to a violation of the tightness of the water-cooling channels. In the presence of leaks – the cameras are discarded and must be replaced with new ones. In the scientific and technical literature, there is no data on the causes of failure, including the formation of cracks in water-cooled copper products, as well as the possibility of their repair. Therefore, the present work, developing the research by Ilyushenko et al. (2019) is aimed to clarify the reasons for degradation of the copper chambers and

the extension of their service life. 2. Experimental investigation

As a result of detailed studies of the metal of the copper chambers after their operation, it was found that these parts wore out as a result of extremely difficult operating conditions (thermal, chemical and mechanical stress). In this case, the characteristic defects of the chambers are the formation of deep cracks over the entire working surface of the grid (Fig. 2 a), traces of mechanical impact (Fig. 2 b), local burnout of copper on the end part of the chamber (Fig. 2 c), up to through burn-throughs walls of water-cooling channels (Fig. 2 d), which leads to the appearance of leaks, as shown by Ilyushenko et al. (2019).