Development of On-line Analytical Method for Hydrogen in Molten Steel at Vacuum Degassing Process

Abstract

Degassing operation in the steel making process is important in the production of low-hydrogen steel. The conventional analytical method for hydrogen in molten steel with sampling using a quartz tube takes a long time, and has insufficient accuracy.A direct analytical method for hydrogen in molten steel has been developed to solve these problems.In this system, a refractory probe is immersed in the molten steel and inert gas is blown through it into the molten steel.The hydrogen concentration in molten steel is then continuously measured by recovering samples of gas that has reached equilibrium in floating upward to a specified level in the ladle. This new analytical system is installed at the RH vacuum degasser of the steel making plant, and is being tested for its application to commercial operation. During degassing operation, the analytical values obtained by the proposed method well agree with those by the conventional method in the low concentration range.On the other hand, the proposed analytical method yields higher values in the high concentration range, probably because of the escape of hydrogen from the sample during and after sampling in the conventional method.The new analytical method can continuously measure the hydrogen concentration of molten steel in 2.5 min, about one-tenth of the analytical time of the conventional method.Key words : on-line analysis ; hydrogen in molten steel ; degassing process ; equilibrium of hydrogen between molten steel and inert gas ; refractory probe for hydrogen sampling.

Steel and related materials

“…At high concentrations the furnace-side probes yield higher results. The discrepancy is due to hydrogen escape during and after sampling when the laboratory method is employed (118). Other workers have bubbled argon through the steel bath and collected the resultant gas under the ladle cover or a bell jar.…”