Abstract:
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The mold is one of the most important components of the continuous casting machine since
the mold controls the shape and initial solidification of the steel product, where quality is
either created or lost. During casting, the mold is submitted to heat flux from liquid steel on
one side whereas the other side is water cooled, leading to the generation of large
temperature gradients. It is also submitted to other stresses such as ferrostatic pressure and
clamping forces. Casting can last several dozens of hours whereas the cooling step of the
mold, when liquid steel is not poured anymore into the mold, can last only a few minutes.
Maintaining a reliable, crack-free mold within close dimensional tolerances is crucial to safety
and productivity.
In order to withdraw the right amount of heat and to prevent mold distortion, mold is generally
made of copper alloys that have the thermal and mechanical properties required for this
function. The two copper alloys most widely used for casting mold are Cu-Ag and Cu-Cr-Zr.
They present a wide range of thermal and mechanical properties due to the different
treatments to which they can be submitted.
The present master thesis aims to study the influence of thermomechanical properties of
copper alloys on continuous casting mold behavior during casting and cooling, and more
precisely on mold for continuous casting of steel slabs using realistic finite element models of
heat transfer and stress.
After realizing a literature review of the most widely used copper alloys, three finite elements
models were developed in order to study the influence of three copper alloy grades on mold
thermomechanical behavior. The three finite elements models were a 2D simplistic
transverse section of the mold model, a 2D transverse section of the mold model that
includes bolts and the backup plate and a 3D quarter mold model. Simulations of casting and
cooling step were performed with ABAQUS 6.10® for the two most widely used copper alloys
and a copper alloy that was previously submitted to a heat treatment. Simulations results
show that the two copper alloys most widely used lead to similar mold behavior. Besides, the
material submitted to a heat treatment does not lead to a critical behavior but can lead to a
necessity of more frequent re-machining of the mold. |