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Platinum Metals Rev., 1958, 2, (4), 116

Immersion Thermocouple Practice in the USA

Benefits of Tapping Temperature Control in Open-Hearth Furnaces

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The metallurgical and economic advantages to be obtained by using the platinum: rhodium-platinum immersion thermocouples were emphasised in the course of a paper on "Basic Open-hearth Steelmaking in the USA" presented during the meeting of the Iron and Steel Institute held in June in Belgium and Luxembourg (J. Iron Steel Inst., 1958, 189, (July), 205–216).

The authors, Dr. M. W. Lightner and Dr. D. L. McBride, both of the United States Steel Corporation, recall that for some time most steel plants confined their use of the immersion couple to recording bath temperatures just before tapping or furnace deoxidation. It was soon recognised, however, that the thermocouple could be a valuable tool for controlling bath temperatures within a prescribed range so that furnace banks and bottoms would not be damaged by getting heats too hot, while excessive ladle skulls could be minimised by avoiding cold heats. Control charts were therefore established showing the relationship between bath temperature and carbon content which would permit rapid ore feeding without chilling the bath.

Throughout the plants of the United States Steel Corporation every effort is now made to tap all heats within of the prescribed temperature. It is found that, with proper attention, all plants can tap at least 80 per cent of their heats within the specified temperature range, some plants consistently achieving 90 per cent compliance.

The excellent control of tapping temperatures has been accompanied by a substantial improvement in pouring practice, while other benefits obtained include a 21 per cent decrease in heats downgraded on account of skulls and a 22 per cent reduction in stool consumption. These improvements in quality have been achieved concurrently with a 7.5 per cent decrease in heat time.

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