vacuum induction furnace smelting the core problem
The vacuum induction furnace is a common tool for advanced steel smelting in China. In order to make the operation personnel in operation of have a deeper understanding, so as to rapidly improve their proficiency, and on this basis, the obtained product yield and quality improvement, the authors in the literature from the past, choose a few important discourse, were introduced, and the computer simulation, in order to solve the problem in the future.
Introduction to 1.
The vacuum induction furnace has two basic characteristics: first, it has a high vacuum degree, which can reach 10 "mm mercury column generally. The other is the induction capacity of electromagnetic induction to molten steel. At a high vacuum, some of the elements or gases in the melt that can be boiled can be expelled from the melt. Examples include lead, manganese, tin, copper, magnesium, CO, H:, etc. For example, Olette chuan believes that the order of the distillation speed of elements is :Pb>Mn>Cu>Sn, while Gill: Sn, Mn> Pb Cu. The notable one is manganese. Because other elements are rare, manganese is common. There are also many reports on the distillation of manganese. The manganese of 0.04% of the original charge is less than 0.01% in the final ingot due to the loss of evaporation. The wall of the cooling chamber is covered with black pit deposits that can ignite. The analysis is basically manganese oxide and iron oxide c32. There are many examples of volatile gases produced in the reaction, the most important of which is the reaction of carbon and oxygen in iron to form CO. The advent of vacuum steelmaking is driven by it. General behavior of oxygen in steel: the steelmaking reaction is generally the two main processes of oxidation reaction and reduction reaction. In the beginning, people need to use oxygen to remove the excess carbon, phosphorus and other elements of iron water to a certain extent. In order to achieve this goal, it is inevitable to retain too much oxygen in subway water, so reduction reaction is needed to eliminate the excess oxygen. Oxygen exists as an atom in iron water. After oxidation, oxygen is stored in a large quantity, and when the iron water cools to 6 iron, oxygen is precipitated out. As the temperature drops, the oversaturated oxygen is precipitated. Oxygen may be precipitated from iron water by combining with soluble elements such as phosphorus, carbon, manganese, silicon, aluminum, or FeO with Fe. In the molten state to form oxides from molten iron is possible. But in molten iron oxides formed after solidification, all for solid inclusions in the dendrite arm of iron, or precipitation in r within the boundary of iron. Gaseous oxides exist in iron as bubbles. These values, when compared with 0.23%, show a large drop in oxygen solubility. It should also be noted that oxygen is constantly precipitating out during the process of iron cooling from liquid to room temperature. Carbon is the most common element in steel. Oxygen is usually precipitated by forming CO bubbles with carbon during cooling. Even though the outer layer of molten steel has solidified, there is still CO precipitation. This phenomenon caused trouble in ingot injection. In the history of steelmaking, this phenomenon has been used in the environmental deep drawing of effervescent steel and the semi-sedation steel with the highest steel yield. The benefits have been achieved by precisely controlling the formation of bubbles. But soon people have higher request for the use of steel performance, which requires ingot or casting must be completely ruled out the formation of air bubbles, it need to add more steel deoxidizer greatly reduced oxygen in the molten steel before solidification. The removed oxygen is removed with an oxide insoluble in iron water. In the refining of steel, is to use oxygen and carbon and other elements of the selective oxidation, and refined after the residual oxygen through clever adjustment, make steel ingot, casting or continuous casting slab and billet can get the best structure of the most productive rate and qualified products. The supposed deoxygenation product can easily float on the surface of iron water and be removed, but it is not so simple. Some elements add to form oxides quickly, such as silicon, but oxides float very slowly. Some elements, such as aluminum, float faster, but when added, they form more slowly. As a result, some of the oxides are still trapped inside the ingot, forming non-metallic inclusions. In addition, after the solidification of iron water, the oxygen gradually precipitated and the remaining iron inside the silicon, aluminum, manganese combination of the non-metal inclusion, is retained in the ingot. Non-metallic inclusion is very harmful to the performance of steel. Some mechanical properties such as fatigue life and tear resistance are very sensitive to inclusion. For some key parts of major equipment, the unit of use has very strict requirements on the number and type of inclusions in steel, which shows the importance of carbon deoxygenation in vacuum.
Carbon and oxygen reactions in vacuum
Vacuum carbon deoxidization: as far as possible to reduce the number of inner inclusion is the most effective way to reduce the number of deoxidizer, and its method is before adding strengthen deoxidizer, try to reduce the oxygen content in iron. Carbon deoxygenation is an ideal method. Because the carbon and oxygen reaction product is CO, is a gas, easy to escape out of iron water and do not form inclusion. When the resulting CO bubbles flow through the molten iron layer, they also carry suspended inclusions in the molten iron and hydrogen and nitrogen, which are already dissolved in the molten iron. Meat, the study of carbon deoxygenation has attracted many researchers' interest. In the production of carbon or high carbon steel, vacuum smelting can produce steel ingots that meet the requirements of sedation steel by carbon deoxidation alone without any strong deoxidizer added. However, there are other reasons to add enhanced deoxidizer in general.