Variação da taxa de descarburação para vários padrões de injeção de argônio na perna de subida do desgaseificador a vácuo RH

• Ano de defesa: 2010
• Autor(a) principal: Marlon José dos Anjos Silva
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Engenharia metalúrgica e de minas; Engenharia metalúrgica; Metalurgia extrativa
• Link de acesso: http://hdl.handle.net/1843/BUDB-8DHF4X

With increasing quality requirements in Ultra Low Carbon steels in recent years, there has been a growing demand for these steel grades containing very low carbon contents in extremely narrow ranges. These steels are commonly produced in RH degassers. For this reason the RH degasser has been the focus of various studies investigating the effects of different variables on the circulation and decarburization rates.The efficiency of the RH degasser is related to the argon flow rate used in the upleg snorkel. This flow rate is one of the most important process control variable in RH, since it determines the kinetics of the decarburization reaction. The purpose of the present study is to investigate the variation of the decarburization rate as a function ofthe argon flow rate in the upleg snorkel, and to determine the best flow rate to be used in each decarburization stage. At this test were evaluated 97 heats of ultra low carbon steel using three different argon flow rates of 80, 110 and 140 Nm3/h alternately. Steel samples were taken for chemical analysis. It was taken at approximate 0, 6 and 12 minutes of each heat to analyze two different decarburization process stages used at Usiminas. For the first decarburization stage, the apparent rate constant was similar for the three conditions tested (80, 110 and 140 Nm3/h). Therefore, the treatment pattern was exchange from 110 to 80 Nm3/h, using the smallest flow rate. The estimated argon consumption reduction is 18.900 Nm3/year and consequently, this gas is available for other activities at steelmaking shop. It represents an economy of approximately R$ 22.700,00/year. Another benefit is the reduction of the steel temperature drop during the treatment. This reduction is estimated in approximately 0,04°C/treatment. For the second decarburization stage, the apparent rate constant to the argon flow rate of 140 Nm3/h was higher than other ones (80 and 110 Nm3/h). In this case, it was decide to maintain the pattern of 140 Nm3/h.