Abstract
A new experimental method, called the ‘hole filling method’, is proposed to simulate the healing of internal cracks in rolled workpieces. Based on the experimental results, the evolution in the microstructure, in terms of diffusion, nucleation and recrystallisation were used to analyze the crack healing mechanism. We also validated the phenomenon of segmented healing. Internal crack healing involves plastic deformation, heat transfer and an increase in the free energy introduced by the cracks. It is proposed that internal cracks heal better under high plastic deformation followed by slow cooling after rolling. Crack healing is controlled by diffusion of atoms from the matrix to the crack surface, and also by the nucleation and growth of ferrite grain on the crack surface. The diffusion mechanism is used to explain the source of material needed for crack healing. The recrystallisation mechanism is used to explain grain nucleation and growth, accompanied by atomic migration to the crack surface.
Highlights
In recent years, steel production has increased rapidly, and it is significant to develop high performance steel products with low cost for high competiveness [1]
Driving force behind internal crack healing Compared with material without cracks, existing cracks result in an increment in the free surface energy in metals
Is heat generated during the hot rolling process with plain carbon steel samples with internal cracks, the crack surfaces can come into contact or be ‘welded’ to reach the threshold of atomic interactions under the adequate rolling pressure
Summary
Steel production has increased rapidly, and it is significant to develop high performance steel products with low cost for high competiveness [1]. It is proposed that material diffusion, grain nucleation and recrystallization contribute to the healing of internal cracks. Driving force behind internal crack healing Compared with material without cracks, existing cracks result in an increment in the free surface energy in metals.
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