Production Technology Of Cleaning-free Continuous Casting Slab

The development history, the character of the production technology and the application situation of CC-DHCR and CC-HCR have been introduced in this paper,and the importance of production of cleaning-free slab in this process has been summarized in detail. Based on the production practice of 3rd caster of a steel factory, the factors which affect the rate of cleaning-free of C-C slab were studied. Series of measures including composition of steel, casting process and 2nd cooling system have been proposed and these measures were validated in successful industrial experiments. The goals of this paper have all been achieved after all the work finished.The main conclusions are as follows:1) The compositions of steel have significant effect on its C-C slab quality. The special phase transition occurring in the meniscus region of mould in course of initial shell are growing makes peritectic steels having lognitudinal crack on its C-C slab surface. The occurring rate of this crack was under controlled behind 0.4% after its C content was adjusted fractionally and chemical and physical characters of mould power were optimized.2) Micro-alloy steels are difficult to be casted due to their special mechanical behaviors. The microalloying elements affect mechanical behaviors through change its interfaces or inner character of grain. Ductility and plasticity of their slabs decline with these elements addition. Transversal corner crack and transversal crack usually occur on slabs and finished plates of these steels for the unstable austenitic grain boundary being break and deteriorated in C-C and rolling process, which will depress the rolling yield and efficiency of production. Measures as reduce cooling water of mould and 2nd cooling zone have been taken to cope with the crack and the waster rate of plates bring by these cracks have declined to 2%. Measures as reduce water in mould power and other ancillary materials and blowing argon flowrate in C-C process were taken to deal with the contingently occurred slab surface porosity defect, which was avoided soon.3) Slag entrapment (on surface and under surface) is fatal defect of high-quality steels such as deep drawing steel plate and galvanized sheet. This type of defect was come from slag engulfed in mould. The defect was eliminated by adjusting components of mould powder and C-C operating procedure.4) The whole 2nd cooling system and its control mode was revamped to improve the controlling precision and regulating conveniences, at the same time, improve the defect -controlling level and hot charging level of 3rd caster through increased temperature of the slabs. Anticipated result was rechieved after series of measures were taken to improve the quality of narrow slabs and degraded rate of finished plates decreased obviously.5) The cleaning-free rate of slabs of 3rd caster has been improved to 99% and virtual hot charge rate to 55%, which have done the trick.