SU550580A1 - Method for rapid determination of steel oxidation - Google Patents

Description

This invention relates to physicochemical studies of metallurgical processes. A known method for the rapid determination of the oxidation of steel is based on the measurement of the electromotive force of a high-temperature galvanic cell. This method has a very low accuracy, due to the large scatter of the values of the fraction of ionic conductivity of solid 10 electrolyte at the tips, even from one batch; parasitic electromotive forces or electromotive forces arising at the point of contact of the current collector with the metal due to its dissolution and oxidation; 15 uncontrolled closure of the current collector and the standard electrode through red-hot ceramics; the imposition of errors arising from the measurement of the fraction of ionic conductivity, oxygen activity in the standard 20 element, bath temperatures, which are added together with the errors of the secondary devices. In addition, despite the seeming versatility of the method, its practical application requires a continuous study of the fraction of ionic conductivity of solid electrolyte for tips of each batch. In order to improve the accuracy of determination, a gas is passed through the molten metal using a capillary, the metal droplets emitted by the evolving inert gas bubbles are collected and the amount of oxygen dissolved in the metal is judged by their size. The proposed method is based on the established relationship between the size R of a bubble exiting the capillary and the surface tension of the metal a R AY, where A is a value independent of a and determined by the conditions of the experiment. The general scheme of the proposed method can be described by the following structural formula, which means that the amount of oxygen dissolved in the metal determines the surface tension of the metal, and the surface tension determines the size of gas bubbles passed through a calibrated capillary, and the size of the bubbles, in turn, determines the size of the ejected metal droplets. Thus, the determination of the concentration of oxygen dissolved in the metal is reduced

to determine the size of metal particles.

An example of the method.

The wire is a special study that calibrates the equipment used. To do this, gas is passed in a bubbly mode at a predetermined temperature through the molten steel of a given grade, and metal drops formed by the bubbles are taken out and their size is determined. At the same time, the content of dissolved oxygen is determined with high accuracy (for example, by the alumina method). By changing it (by blowing metal with oxygen), the measurements are repeated.

Thus, the dependence of g-for a given steel grade is determined at a determined temperature. The study is repeated for other temperatures, since the magnitude of the surface tension depends on the temperature, and the results are plotted on a common sheet. The same nomogram is made for other steel grades.

To expressly determine the oxidation of steel, a gas bubble is introduced through a ceramic capillary immersed in a metal in a bubble mode at a frequency of one bubble per second. It is convenient to use a 2 mm capillary. When using larger capillaries, large drops of metal are formed that are difficult to cool to solidify in the carrier gas stream. In addition, large drops are more susceptible to deformation, which makes it difficult to use the known automatic methods of particle size (with the exception of tepometric).

On the other hand, the use of narrower capillaries also increases the determination error, as the relative measurement error increases with decreasing particle size and the blurring of the capillary by the metal greatly affects. An inert gas with low heat capacity (argon) should be used as bubbling gas. The use of active gases leads to unreported side effects. The depth of the capillary is chosen to be 10–15 cm. With a very small depth of the capillary, the kinetic energy of the bubbling up of the bubble is insufficient to detach the drops of metal from the bath.

The surface of the metal is usually covered with a layer of slag. In order to create the conditions for the free escape of bubbles around the flow zone of the bubbling gas, an intense gas curtain is created which pushes the slag back from the surface of the bath at the measurement site. If the amount of slag is very large, then it is pre-downloaded one of the known methods. As a result of the passage of bubbles from

Drops of metal are ejected, the size of which, under other conditions being constant, is determined by the content of dissolved oxygen in the metal. These droplets rise in an upward flow, cool therein and

quickly harden. Hardened metal droplets along the discharge path are transferred from the extraction zone to the outside of the bath and enter the sensor of the measuring system. It is convenient to use argon as the gas supplied to create the blowing gas curtain and to form a transport stream.

Photoelectric, capacitive, inductive and strain gauge sensors can be used in the measurement system circuit to automatically determine particle size. It is preferable to use a strain gauge, since in this case the weight of each particle entering the sensor and the total weight of the particles are measured. The method may also have a non-automatic ending: incoming particles are collected and weighed on an analytical balance; based on the weight and number of particles, find their sizes.

Evaluation of the accuracy of measuring the amount of oxygen dissolved in the metal by the proposed method gives a relative error of 8%.

Claims (1)

Invention Formula A method for the rapid determination of the oxidation of steel, characterized in that, in order to increase the accuracy of the determination, an inert gas is passed through the molten metal using a capillary, the metal droplets emitted by the released inert gas bubbles are collected and judged on the amount dissolved in megayllus oxygen.