Broken edge: influence of edge trimming over falt rolled steel in hot strip mills
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Abstract
The trimming process of sheet metals has been used to prepare workpieces (steel
coils) for subsequent forming operations: from very light components to heavy
appliances and machinery. The present work is based on the quality of trimmed edge,
which is affected not only by the material characteristics by itself, but also by process
parameters such as: clearance between knives (upper and lower) and sharpness of
the knives during the side trimming process.
The present research has the objective of developing a model to explain the edge
trimming behavior of flat rolled steel.
In the present investigation, the edge trimming process is FEM-simulated using a
rigid-plastic model, where a very localized plastic deformation near the upper and
lower knife gives at certain stage, the driving force for cracking, being the cracks'
direction a direct factor that affects the quality of the edges. A mechanical study was
carried out to obtain the intrinsic mechanical properties such as the strain hardening
exponent (n) and the strength coefficient (K), which were taken into account to obtain
near-real simulation results; furthermore, a metallurgical and hardness study was
made to take into account the microstructure and hardness behavior of the flat rolled
steel. At last, a correlational study was performed, to develop a state of the art edge
trimming model.
The final proposed model gives high-confidence horizontal clearances values for the
studied sheet steels; taking as principal factor, the energy (N-mm) expended during
the edge trimming process. The final contour of every steel was analyzed and its
trends over clearance. The proposed model gives results in agreement with the FEM
simulations information.
A model has been developed in order to help edge trimmer operators to adjust and
control technological parameters of the process.