The present invention relates to a continuous temperature sensor used in a Ruhrstahl-Heraeus (RH) process of mainly performing vacuum degassing in steelworks, and an RH apparatus including the same.
Vacuum level and temperature within a vacuum vessel and additives are important control factors for an RH apparatus that performs a vacuum degassing process.
Although various information for continuous measurement and control of temperature can be obtained through a temperature sensor or a composite sensor using a thermocouple in a batch, the temperature sensor or composite sensor is limited in the continuous provision of information regarding molten steel.
Referring to U.S. Pat. No. 6,235,084 (issued on May 22, 2001), the temperature of an RH apparatus is generally measured with a temperature measurement element-thermocouple using a lance on an upper surface of a ladle exposed to the atmosphere. In this case, however, since temperature measurement is performed using a disposable sensor, the temperature is intermittently measured, thereby making it difficult to achieve continuous temperature management.
Korean Patent No. 10-0816634 (issued on Mar. 18, 2008) discloses a method of measuring temperature for a long period of time by arranging a thermocouple within a protective body. However, this method requires an expensive platinum thermocouple which has a long length like a sensor and, thus, costs are incurred due to a high-priced protection tube and thermal equilibrium takes a long duration when the thermocouple is dipped in a melt to be measured, thereby causing undesirable response performance. Also, degradation rapidly progresses due to characteristics of the vacuum degassing process, in which dipping and recovery of the thermocouple are repeated, thereby making it difficult to use the thermocouple for a long period of time.
U.S. Patent Application Publication No. 2007-0268477 (published on Nov. 22, 2007) discloses a method in which continuous temperature measurement can be performed by dipping an optical fiber in molten metal, while correcting an error of a measurement instrument due to radiant heat. The optical fiber directly contacts the interior of the molten steel while avoiding slag floating on the molten metal, thereby enabling temperature measurement of the molten metal. In this method, since the dipped optical fiber can be lost, continuous dipping of the optical fiber is performed through a feeder supplying optical fibers. Further, this method can suffer from problems caused by heat radiation.
An objective of the present invention is to provide a continuous temperature measuring device which can continuously measure temperature at low cost and can effectively measure the temperature of molten steel in an RH apparatus, and an RH apparatus including the same.