Oxygen in Steel Refining as Determined by Solid Electrolyte Techniques

Summary

These illustrations are typical of the results which have been obtained by use of the O-Probe in acid open hearth steels. It is obvious that the probe can provide valuable information to the operator while the steel is still liquid.

Such instantaneous information, if properly interpreted, can go a long way toward the production of quality steels and provide a solution to one of the oldest problems encountered in all steelmaking.

For some time to come, it will probably be desirable to study the oxygen trends of heats using both the vacuum fusion test and the O-Probe. And as shown in these illustrations, if they do not agree, there should be a feasible metallurgical explanation.

The O-Probe will be most useful during the period of an active carbon boil, just prior to tapping and during teeming. The latter is true particularly for rimming or semi-killed steels. Such instantaneous information should go a long way toward improving steel quality.

The solid electrolyte results reported in this paper were obtained through the use of two developments which have not been previously reported. One of these is the use of a carbonate as the source of CO₂ and thus, as the oxygen standard reference.

The other is the “O-Mold”. Instead of a probe inserted into a liquid metal, this device consists of a refractory mold containing the probe, a thermocouple, and an auxiliary electrode. Wherever one may obtain a spoonful of metal which can be poured into the O-Mold, one may determine its oxygen content. A number of heats have been followed by this method and it has many advantages.

The probe in the mold is equipped with a Pt-PtRh thermocouple so that a simultaneous temperature is recorded, through the use of a two channel recorder. The freezing point of the metal and also the carbon content are thus indicated simultaneously with the oxygen by this means.