真空加熱法によるチタン中の水素定量方法におけるガス抽出温度の定量値への影響

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The method for determination of hydrogen in metallic titanium by high temperature vacuum extraction was investigated to find the optimum gas extraction temperature. A temperature of 1500°C was found to be the best for gas extraction temperature based on the experimental data for gas collection curves and gas collection times. Compared with the existing method using a temperature of 1000°C, the established method was found to give higher values by 16 ppm on the average than the existing method for samples containing 2080 ppm of hydrogen and to give a smaller coefficient of variation less than 3%, and to require a shorter gas collection time within 310 minutes. The average amounts of hydrogen obtained at the gas extraction temperatures are significantly different between 1000°C and 1500°C at the 95% confidence level. To clarify the reason why a high value was obtainable, an experiment was carried out using a palladium alloy permeating type analyzer for gases in metals which had been developed by one of the authors. From this experiment it was found that a quantity of hydrogen ascribable to the temperature difference between 1000°C and 1500°C was obtained when the sample was heated to 1500°C after being determined at 1000°C. Another experiment involving a gas-recycling recovery was made to understand the adsorption phenomena by attaching a gas recycling device to the gas collecting section of this apparatus. By the device, after the determination of hydrogen in titanium at 1000°C has been finished, the gas was recycled to the gas extraction furnace by way of a cock. When approximately the same quantity of hydrogen as the extracted gas from the sample is introduced into the constant volume manometric section of gas collecting system to be recycled, and then the graphite crucible in the furnace is heated to 1500°C, approximately the same quantity of hydrogen as from the sample can be collected, indicating that the gas adsorption phenomena occur with difficulty at 1500°C. The measured recoveries were found to be nearly 100% at 1500°C against 95% at 1000°C, showing evident gas adsorption phenomena at 1000°C. From these results it is evident that titanium shows a definite difference in the hydrogen adsorption phenomena depending on the gas extraction temperature in contrast to the previous view implying a difficulty for the adsorption to occur at a high temperature below the melting point. This fact is considered to be responsible for a higher value obtainable at 1500°C rather than at 1000°C.
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真空加熱法によるチタン中の水素定量方法におけるガス抽出温度の定量値への影響

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