GB979702A - Process and equipment for rapid oxygen determinations in metals,in particular steels - Google Patents

Abstract

979,702. Oxygen determination in metals. HUTTENWERK OBERHAUSEN A.G. May 28, 1963 [Aug. 21, 1962], No. 21179/63. Heading B1X. Oxygen in metals, particularly steels, is determined rapidly by placing a specimen in a recessed graphite electrode inside an extraction chamber, melting it by playing an arc on it to extract the oxygen as CO, switching off the arc immediately after extraction, transferring the extracted gas by pressure equalization to an evacuated measuring chamber filled with an inert carrier gas and determining the oxygen content as CO, e.g. using an I.R. absorptiometer. The end of the extraction is determined by observing the molten sample or by preliminary tests on known specimens; 10-30 seconds being disclosed as a suitable period for melting and extracting the sample. Equipment for this process comprises an extraction chamber with an electrode to hold a specimen and a counter electrode together with an evacuatable measuring chamber connected to analytical apparatus. Manually operated apparatus may be used or a programme controller and servomotor can be used for actuating the pumps, valves and other items automatically in timed sequence. In a specific embodiment (see the Figure), extraction chamber 1 has a rotatable plate 2 with recessed graphite electrodes 3 in which are placed specimens 4 of known weight under a current of protective gas. The chamber is evacuated briefly, e.g. for 30 seconds, by backing pump 7 through valve 6 whereafter valve 6 is closed, valves 9 and 26 opened and high vacuum pump 18 further evacuates chamber 1. The pressure in the two lines is-indicated by gauges 10 and 11. The evacuated chamber is filled with an inert gas, e.g. argon, by valve 12, to slightly above atmospheric pressure, the arc is struck, the specimen melted and the current reduced whilst extraction takes place. During this stage measuring chamber 13 having a volume three times that of chamber 1, is evacuated through valve 14 by pump 7. After extinction of the arc the CO cloud passes through valves 15 and 16 and filter 17 to chamber 13 by pressure equalization. Chamber 13 is then filled with pure argon to slightly above atmospheric pressure, valves 19, 20 and 21 is opened and the gas mixed by circulating pump 22. After mixing the pump is switched off and the CO content determined by I.R. absorptiometer 18. The measuring circuit may be purged through valves 24 and 25 with, e.g., argon, and chamber 13 evacuated by pump 7. A valve 26 provides for the introduction of calibrating gases.