In the quality control of slab continuous casting, in addition to the internal and surface defects of slab, the control of slab shape defects should be considered. The common shape defects of slab are bulging, depression and so on:
1, defect morphology and effect
From the perspective of the cross section, the shape of the casting slab in the large or lateral deviation from the angle of the slab to the inside of the billet
The narrow surface of the slab: in the narrow surface of the billet, the shell is in the shape of arc to the inside of the slab.
The slab deviation angle of deflection angle generally associated with depression or defects, may cause serious leakage of deflection angle steel.
2, cause of formation
1) a serious depression arising from the deviation angle
It is mainly caused by the failure of the fan section of the hydraulic system such as the end of the solidified shell, the lifting of the fan-shaped segment, the fault of the fan section, or the bending of the fan section.
2) general deviation angle depression
The main factors include the composition of molten steel; mold; mold flux; fan section; vibration, temperature, and the speed of the nozzle.
3) the reasons for the overall depression of the narrow face
The main reason for the foot roll adjustment partial hard lead.
3, control measures
1) for the prevention of large deviation angle of severe depression, should do segment hydraulic system maintenance, inspection, to prevent the loss of pressure or hydraulic lift segment. To improve the quality of the roller segment and do daily check, prevent roll fracture, severe depression after the deviation angle position should immediately stop, avoid excessive loss. Hydraulic system failure or replacement of segment after shutdown.
2) try to control the carbon content in the steel to avoid the peritectic reaction zone (C) to the upper or lower limit control.
3) to ensure that the mold to ensure uniform water slot, to improve the mold material, to prevent serious mold wear and coating off, the crystallization of the implementation of weak cold cooling, reasonable control of cooling intensity.
4) according to the characteristics of the steel slag suitable, appropriate increase of mold slag viscosity, improve heat transfer uniformity, slag added with less and adhere to the principle of.
5) to improve the accuracy of sector section arc, especially the mold and the zero section, found that the zero section of the roller bending serious and timely replacement.
6) to monitor the vibration stability, to ensure that the lateral vibration of the pendulum is not greater than 0.2mm, the vertical deflection is not greater than 0.4mm.
7) appropriate to increase the degree of contact with the narrow side foot roller billet, prevent slab bulge, but the foot roller should not adjust good, otherwise it may cause friction, the side slab sag is too large.
8, control the superheat of molten steel, determine the appropriate speed of the system, to prevent the temperature is too high, too fast speed caused by the thin shell.
9) strict nozzle assembly, to ensure good water, to prevent drift, ensure uniform billet solidification.
