Abstract
This paper summarizes a mathematical model for the industrial heating and cooling processes of a steel workpiece corresponding to the steering rack of an automobile. The general purpose of the heat treatment process is to create the necessary hardness on critical parts of the workpiece. Hardening consists of heating the workpiece up to a threshold temperature followed by a rapid cooling such as aquaquenching. The high hardness is due to the steel phase transformation accompanying the rapid cooling resulting in non-equilibrium phases, one of which is the hard microconstituent of steel, namely martensite. The mathematical model describes both processes, heating and cooling. During the first one, heat is produced by Joule’s effect from a very high alternating current passing through the rack. This situation is governed by a set of coupled PDEs/ODEs involving the electric potential, the magnetic vector potential, the temperature, the austenite transformation, the stresses and the displacement field. Once the workpiece has reached the desired temperature, the current is switched off an the cooling stage starts by aquaquenching. In this case, the governing equations involve the temperature, the austenite and martensite phase fractions, the stresses and the displacement field. This mathematical model has been solved by the FEM and 2D numerical simulations are discussed along the paper.
Highlights
Introduction and Description of the IndustrialProcedureThis work deals with the thermomechanical modeling and the numerical simulation of metallurgical phase transitions of steel during an industrial heat treating.Iron and steel production has a very long history that probably dates back to some millennia
In this work we are interested in the mathematical description and the numerical simulation of the hardening procedure of a car steering rack including mechanical effects
This paper describes a problem related to the industrial heating-cooling process of a steel workpiece corresponding to the steering rack of an automobile
Summary
This work deals with the thermomechanical modeling and the numerical simulation of metallurgical phase transitions of steel during an industrial heat treating. In steels with less than 0.8 wt% carbon, known as hypoeutectoid steel, it is possible to observe a significant variation of its internal structure in a temperature range between 727 ◦ C and 912 ◦ C, approximately In this situation, all phases are transformed into austenite (or γ−iron). If the cooling rate is not big enough, the austenite is transformed back into the other phases, i.e., ferrite, pearlite, and bainite (Figure 2) possibly along with a different partition. There are some common situations in which the industrial requirement is such that the outer surface should be hard whereas the inner core should be kept ductile This ensures the workpiece wear resistance while reducing at the same time the material fatigue
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