Modeling and Optimization of Steel Machinability with Genetic Programming: Industrial Study
2. Materials and Methods
- The maximum width of the flank wear land VBB max is equal to or more than 0.6 mm;
- The average width of the flank wear land VBB is equal to or more than 0.3 mm;
- tool failure;
- The depth of the crater KT is equal to or more than 0.18 mm;
- The crater front distance reduces to a value of KF = 0.02 mm;
- The crater breaks through at the minor cutting edge (typically resulting in a poorly machined surface finish).
- Secondary metallurgy (i.e., ladle treatment):
- Calcium-carbide-cored wire (m) used for the modification of aluminum silicate inclusions. According to the length of the calcium-carbide-cored wire addition, the inclusions of different types and morphology form, influencing the material properties and consequently the machinability.
- Ladle treatment time (min), including raffination, argon stirring, alloying, heating, slag forming, taking of samples and technological delays. Ladle treatment time is needed for melt homogenization (including temperature field) and also for purifying. Argon stirring causes inclusions to float up toward the slag, which can trap them.
- Calcium-silicon-cored wire (m) used for the modification of aluminum silicate inclusions. Calcium silicon has the same function as calcium carbide to form proper inclusions.
- Alloys added using automatic feeders:
- Ferrochromium with a low carbon content (kg).
- Ferrochromium with a high carbon content (kg).
- Ferromanganese (kg).
- Ferromolybdenum (kg).
- Ferrosilicon (kg).
- Ferrovanadium (kg).
- Nickel (kg).
- Sulfur-cored wire (m).
- Silicon manganese (kg).
- Casting parameters influencing thermomechanical behavior, solidification and segregations (i.e., chemical nonhomogeneity) during casting:
- Average casting temperature (°C). The casting temperature influences the thermal field in the mold, which influences heat removal and solidification. Due to the thermomechanical behavior of melt in the mold, the melt solidifies, gradually forming a layered nonhomogeneous structure. This structure influences the steel properties.
- Average difference between the input and output water temperature for each mold (°C). This temperature difference is a measure of the efficiency of heat removal from the mold (i.e., primary cooling). The mold is cooled with water. The heating up of the cooling water flowing through the mold indicates the efficiency of heat removal, which influences the melt solidification.
- The average cooling water pressure in the first (directly below the mold) and the second zone of secondary cooling (bar). The melt primarily solidifies in the mold. After exiting the mold (mold is a 1 m long copper tube), the strand is cooled by water sprays, where water flux can be automatically set with varying water pressure. Consequently, water pressure is a measure of water spray nozzle clogging. In the event of water spray nozzle clogging, the pressure should be increased in order to achieve the same water flux, which enables cooling of cast billets. Secondary cooling directly influences the billets’ macrostructure, including chemical composition, segregations (i.e., chemical nonhomogeneity) or material defect formation, which all influence the mechanical properties.
- Chemical composition (%). Content of carbon, silicon, manganese, sulfur, chromium, molybdenum, nickel, aluminum, vanadium and calcium. Chemical elements influence the microstructure and mechanical properties.
- The cutting speed where the tool wears out within 15 min for individual batches (m/min).
3. Modeling of Cutting Speed Where the Tool Wears Out within 15 min
3.1. Modeling of Cutting Speed Where the Tool Wears Out within 15 min Using Linear Regression
3.2. Modeling of Cutting Speed Where the Tool Wears Out within 15 min Using Genetic Programming
- Size of the population of organisms: 1000;
- Maximum number of generations: 100;
- Reproduction probability: 0.4;
- Crossover probability: 0.6;
- Maximum permissible depth in the creation of the population: 30;
- Maximum permissible depth after the operation of crossover of two organisms: 30;
- Smallest permissible depth of organisms in generating new organisms: 2.
4. Optimization of Steel Making Process for the 20MnV6 Steel Grade
Data Availability Statement
Conflicts of Interest
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|Calcium-carbide-cored wire (m)||CAC2||0||215|
|Ladle treatment time (min)||TIMEL||24||100|
|Calcium-silicon-cored wire (m)||CASI||0||340|
|Ferrochromium with low carbon content (kg)||FECRA||0||597|
|Ferrochromium with high carbon content (kg)||FECRC||0||1578|
|Sulfur-cored wire (m)||SM||0||110|
|Silicon manganese (kg)||SIMN||0||1199|
|Average casting temperature (°C)||TEMPC||1516||1564|
|Average difference between input and output water temperature for each mold (°C)||DELTATEMP||4.66||8.78|
|The average cooling water pressure in the first zone of secondary cooling (bar)||P1||2.61||6.68|
|The average cooling water pressure in the second zone of secondary cooling (bar)||P2||1.53||4.93|
|Carbon content (%)||C||0.08||0.55|
|Silicon content (%)||SI||0.02||0.45|
|Manganese content (%)||MN||0.34||1.59|
|Sulfur content (%)||S||0.013||0.059|
|Chromium content (%)||CR||0.06||2|
|Molybdenum content (%)||MO||0.01||0.37|
|Nickel content (%)||NI||0.05||1.96|
|Aluminum content (%)||AL||0.011||0.031|
|Vanadium content (%)||V||0||0.14|
|Calcium content (%)||CA||0.0011||0.005|
|The cutting speed where the tool wears out within 15 min forindividual batches (m)||Vc, 15 min||210||450|
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Kovačič, M.; Salihu, S.; Gantar, G.; Župerl, U. Modeling and Optimization of Steel Machinability with Genetic Programming: Industrial Study. Metals 2021, 11, 426. https://doi.org/10.3390/met11030426
Kovačič M, Salihu S, Gantar G, Župerl U. Modeling and Optimization of Steel Machinability with Genetic Programming: Industrial Study. Metals. 2021; 11(3):426. https://doi.org/10.3390/met11030426Chicago/Turabian Style
Kovačič, Miha, Shpetim Salihu, Gašper Gantar, and Uroš Župerl. 2021. "Modeling and Optimization of Steel Machinability with Genetic Programming: Industrial Study" Metals 11, no. 3: 426. https://doi.org/10.3390/met11030426