In the production of heavy steel plates basically two different process routes can be distinguished: One way is the thermomechanical rolling and a subsequent online accelerated cooling process. Here an appropriate temperature control during rolling and cooling is necessary in order to achieve the desired mechanical properties of the plates. The alternative is quenching after reheating in a so-called ”Quette”. Within this process the rolling only influences the geometric properties, while the mechanical properties are adjusted afterwards in a heat treatment step. The cooling in the Quette induces a characteristic residual stress-state in the plates. In this thesis the cooling process in the Quette is simulated with different numerical models. These models should reliably predict the thermomechanical behaviour of the plates in the Quette. An important factor for the implementation in the online-process control is the calculation of the residual stresses within reasonable computation times. To this end three different Finite-Element-models were created. With the FEM-software Abaqus a 3D-model of a representative segment of the plate was generated. This model was compared with a 2D-model and furthermore with an already existing simplified 1D-Matlab-model modified to satisfy the geometrical constraints in the Quette. This model is very efficient in that it is capable of calculating the stresses much faster than the Abaqus models. The main goal of this work is to establish a correlation between the three different model approaches in order to provide tools for future online-control software. For the modelling the following aspects have to be observed: The clamping- mechanism defines the geometric boundary conditions of the plates. Once in the Quette, a plate is no longer able to bend out of plane, hence residual stresses form. The stress distribution across the thickness is asymmetric, which can be explained by a different water-spraying-intensity on the upper surface versus the lower surface. On the upper surface a boiling steam film will isolate the plate, but on the lower surface a totally different situation prevails due to the gravity acting on the fluid. Furthermore transformation induced plasticity (TRIP) during the phase change from austenite to the product phase has an important influence on the residual stress distribution.
|Translated title of the contribution||Thermomechanical simulation of the quenching process of quenched and tempered heavy steel plates|
|Award date||1 Jul 2016|
|Publication status||Published - 2016|
Bibliographical noteembargoed until 27-04-2021
- heavy steel plates
- residual stress