Formation and Solid solution Behavior of Carbonitride in Large Steel Ingots
Large steel ingots, ranging from 10 to 28 tons in weight, are commonly used to produce a broad range of products including automotive components, pipelines, and large machinery parts. As one of the important microstructural constituents in steel, the presence of carbonitrides can significantly affect the mechanical properties of the final products. Carbonitrides form in steel either during the solidification process, or as a result of further thermal processing of the ingot. During the solidification process, fast quenching and re-melting in the electric arc furnace lead to heterogeneous nucleation of nitrogen and carbon-containing species, resulting in the formation of either MC or M2C type of carbonitride nitrides. The solid solution behavior of carbonitride nitrides in steel is affected by various factors. For instance, the presence of other alloying elements such as molybdenum and chromium can promote the dissolution of carbonitride nitrides in steel. Additionally, the cooling rate of the ingot can also control the dissolution and size of carbonitride nitrides.
The effect of carbonitrides on the mechanical properties of steel is well known. For instance, the high strength of the steel products is largely attributed to the presence of carbonitrides. Additionally, it is also known that nitrogen based carbonitride particles, such as M2C, provide very good resistance to hot tearing. Therefore, it is important to understand the formation and solid solution behavior of carbonitrides in large steel ingots.
Laser head extraction technique is a common method for studying the solid solution behavior of carbonitrides in steel. In this technique, a cutting tool is used to extract a thin slice from the steel ingot and analyze its microstructure using electron microscopy. The extracted slice is then annealed to reduce and control the size of grains and carbonitride particles. Annealing also helps to enhance the precence of carbonitrides, allowing for better characterization of their solid solution behavior.
Another widely used method for studying carbonitride formation in steel is differential thermal analysis. In this technique, a rapid thermal ramp is applied to the steel ingot to study its phase transformation behavior. The Austin-Knudsen computational model is used to predict the formation and subsequent solid solution of carbonitrides in the steel ingot. The model takes into account the thermal history of the steel ingot, the actual temperature-time history of thermal treatments, and the presence of carbon and nitrogen in the steel. The model can effectively predict the formation and solid solution behavior of carbonitride nitrides in different steel alloys.
In conclusion, the formation and solid solution behavior of carbonitride nitrides in large steel ingots has a significant effect on the mechanical properties of the resulting product. Laser head extraction and differential thermal analysis are two effective ways to study the formation and solid solution behavior of carbonitride nitrides in steel. By understanding the effect of carbonitride nitrides on the microstructure and mechanical properties of steel, it is possible to optimize their formation and subsequent solid solution behavior for better and more durable products.
