Abstract
The multiscale model of pearlitic transformation, including the finite element solution of the second Fick’s equation with moving boundary in the microscale and Fourier equation in the macroscale, is presented in this paper. According to the mixed-mode approach, both the volume diffusion and the interface mobility were considered. Model describes sidewise and frontal growth of cementite and ferrite plates in a single grain of the austenite. Assessment of the possibility of the developed model application to determine the key parameters in terms of strength properties of pearlitic steel, i.e., pearlite grain size and colony size as well as interlamellar spacing for various cooling conditions, was the main aim of this work. The model was validated and verified on the basis of experimental tests performed for two eutectoid steels. In practice, developed model can support design process for a technology of high-strength rods and long products manufacturing. Rails were selected as a case study in this work, and therefore, numerical simulations of accelerated cooling of the rail head were performed and the relationship between the parameters of heat treatment, parameters of the structure and properties of the finished product was determined on the basis of obtained results.
Highlights
Pearlitic steels are of great importance in a number of extremely demanding structural applications, in a large part due to their combination of strength and toughness (Ref 1)
AuthorÕs earlier works (Ref 6, 7) showed that the model based on the solution of the FickÕs equation is characterized by the large predictive capabilities
The smallest interlamellar spacing equal to 0.21 lm was obtained for time– temperature profile according to cycle II at point 1 located close to the head surface
Summary
Pearlitic steels are of great importance in a number of extremely demanding structural applications, in a large part due to their combination of strength and toughness (Ref 1). These exceptional properties are controlled by the microstructures developed in pearlitic steels, especially interlamellar spacing, pearlite colony size and prior austenite grain size. Among many applications of pearlitic steel we can distinguish wires (Ref 2) and rails (Ref 3) investigated in the present paper. Numerical models of pearlitic transformation can support process of designing of rails manufacturing technology, which leads to costs reduction and improves the quality of finished products. Advanced full field models based on the explicit representation of the microstructure have been recently developed and are available in the scientific literature (Ref 4, 5)
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