Continuous casting process is gradually cooled and solidified by forced into a hot slab physical process, but also the slab during solidification to withstand solidification shrinkage, cooling shrinkage, shrinkage phase transition shrinkage stress, thermal stress caused by temperature gradients, steel bulging stress hydrostatic pressure caused by stress and bending and straightening equipment malfunction caused additional stress of thermo-mechanical process.
In continuous casting production, reducing the intensity of the secondary cooling zone cooling which uses weak cooling can reduce and prevent cracks. Reducing the cooling rate can reduce the thermal stress caused by temperature gradients within and outside the large sample cause, but also can make the steel substrate precipitates increases, reducing the number of grain boundaries along fine precipitates and inhibit precipitation of fine mesh ferrite, the plastic is improved. low strain rate in the continuous casting process, the size of the strain rate significantly affect the temperature of the plastic material.
Casting process is an uneven cooling process, which is reflected in the uneven since the secondary cooling crystallizer to the whole process, in particular in:
(1) The initial solidified shell in the mold meniscus formed at the cooling and solidification shrinkage due from the mold wall, then the static pressure of the molten steel to turn the pressure of the mold, so that as a contact between the two – out – dynamic process of engagement. Fluxes in the solidified shell thickness is formed on the surface uneven, resulting in uneven and uneven growth of the mold cooling suffered solidified shell is the main cause of slab surface cracks and skin cracks. In the mold made various efforts such as level control, and other measures to improve the protection of slag characteristics can mitigate this inhomogeneity cooling to a certain extent, can not be eradicated.
(2) the slab in the secondary cooling zone of acceptable spray cooling liquid core, resulting in cooling and radiation heat transfer through the air, cooling spray nozzles for cooling and guide rollers are uneven cooling, if uneven cooling severe, will lead to the expansion of the existing performance of small cracks, slab bulging, and cause more internal cracks. Improper cooling liquid core will cause prolonged improper slab surface temperature, surface temperature of the slab in straightening when exposed to high temperatures brittle zone, prone to the performance of transverse cracks, uneven cooling during the initial solidification of oscillation mark trough position is particularly serious.
Post time: Oct-14-2019