The Study On Causes And The Measures Of Controlling About Corner Cracks In Continuous Casting Slab

There are some kinds of defects on the surface of casting slab,corner crack is one of the most serious surface defects.It will affect the quality and the running of the continuous casting.The corner crack of the slab not only makes the hot charging and heat transfer impossible,but also must be cleaned by scarfing or mechanical grinding,resulting in a large amount of waste of energy,materials and human resources.And the stock of slab yard will increase,the normal production rhythm is destroyed.After the hot rolling with the corner crack,the defects such as edge crack or sliver will be found on the strip,then the coil will be downgraded or rejected.This has become a technical bottleneck that the enterprises achieves energy saving and consumption reduction.The passage investigated the corner crack in the slab,analyzed all the reasons like the process,operation and the machine that caused the corner crack.We did a lot of work on optimizing the chemistry of the different steel grades,the parameter of mould cooling and the secondary cooling,and increasing the precision of equipment,and adopting the chamfer mould and so on.In this paper,the chemical composition of crack sensitive steel grade is designed and optimized to minimize crack.Carbon content avoids the area as much as 0.08-0.16 %.Phosphorus content control below 0.015 % and sulfur content control below0.010 %.For the steel grade with B element,we use 0.010-0.020 % titanium for decreasing the quantity of BN then avoid the defects of crack.For increasing the temperature of slab corner through optimizing the secondary cooling.We decreased the margin quantity about 20-50% of the secondary cooling except the bending segment.The corner temperature arrived 920? finally.By improving the precision and management of the equipment,such as the stable mould copper plate quality,mould alignment,clean the filters and nozzles and so on,to reduce the corner cracks caused by mechanical stress.At the same time,through the introduction of the chamfer mould,heat transfer of the corner is changed to reduce the slab corner crack.Under the conditions of industrialization,through a series of studies,the purpose of effectively improving and controlling the defects was achieved.Now the slab quality has a big improvement,the ratio of defect is reducing below 1%.