The first shows how you can use equilibrium calculations set up in the Process Metallurgy Module to gain a general understanding of your BOF process and help you determine optimal operation conditions and predict and optimize costs of raw materials and recycling.
The second example gives detailed instructions on how to simulate the kinetics of the Basic Oxygen Furnace process using the kinetic process simulation released in Thermo-Calc 2020b.
Both examples include calculation files, which can be downloaded and run if you have a license for Thermo-Calc and the relevant databases.
A basic oxygen furnace (BOF) is a vessel used to convert hot metal into steel. The process is known as the basic oxygen furnace process, basic oxygen steelmaking or the oxygen converter process. During the process, oxygen is blown into a BOF converter containing liquid hot metal containing high carbon content. The oxygen combines with the dissolved carbon to form CO, which then escapes as gas. Thus, the hot metal is transformed into liquid steel with a low carbon content.
The Basic Oxygen Furnace process can be used to remove other impurities in addition to carbon. Two elements that are very important in steelmaking and steel refining are sulphur (S) and phosphorus (P). Both elements are usually undesirable and must be removed from the liquid steel. This is generally done by transferring them to a CaO-rich slag phase. In this example, we show how the Process Metallurgy Module in Thermo-Calc can be used to investigate suitable conditions for removing P from liquid steel using a basic oxygen furnace. In a later example, we show how the Module can be used to investigate desulphurization in a ladle furnace.
Two plots from the example showing the change of the chemical composition of the liquid metal as a function of added oxygen. In the left plot, no slag formers are added. In the right plot, 3t of CaO rich slag formers are added, leading to a reduction in P content during the end of the blow, as shown by the light blue line.
The Process Metallurgy Module also allows users to calculate an optimum combination of amount of oxygen and amount of slag required to remove both C and P from the liquid steel for a given hot metal and slag composition. In the equilibrium example, about 5500 Nm3 of oxygen needs to be blown and about 2.7 t of high CaO slag former must be added.
Such a calculation not only predicts the amount of raw materials required, but also the amount of waste produced and the yield of the process. If the cost of the raw materials and the cost of recycling the produced slag is known, then this allows one to calculate and optimize the total cost of the converter process.
Carbon and Phosphorous content in liquid metal (left) and total amount of oxide phases and oxygen content in the liquid metal (right) as a function of oxygen and slag phase added to the system. The optimal combination is shown as a black dot.
This example simulates the kinetics of the Basic Oxygen Furnace process. Metallurgical processes such as the BOF process rarely reach equilibrium. Therefore, a model description must include kinetics if meaningful results are to be obtained. In recent years, a simple but powerful model termed the Effective Equilibrium Reaction Zone (EERZ) model has been developed and widely applied to simulate various metallurgical processes. The model was introduced into Thermo-Calc’s Process Metallurgy Module beginning with the 2020b release.
This example shows you how to set up a kinetic simulation of the BOF process in the Process Metallurgy Module and includes a description of the EERZ model.
This example includes three calculation files:
DEMO: works with the free DEMO version of Thermo-Calc and uses an included demo database.
OXDEMO: works with the full version of Thermo-Calc 2020b or newer and uses an included demo database.
TCOX10: works only with the full version of Thermo-Calc 2020b or newer and requires a license for that database TCOX8, TCOX9 or TCOX10.
The Process Metallurgy Module can be used to investigate the entire steelmaking process, from scrap to fully refined steel. The examples below investigate other steps in the steelmaking process: