Study On The Temperature Field Of CC Slabs In Conveying Process And Stack Cooling Process

In recent years, the technology of hot charge continuous casting slabs has beenwidely used in the steel industry. Hot charge of continuous casting slabs can not onlyreduce energy consumption, but also reduce the stack yard, shorten the production time,improve both the quantity, etc. With the extensive use of the technology of hot charge,which promoted the development of steel production to continuous, low-cost andhigh-quality direction, the extent of the application has gradually been an importantmark to measure the level of steel production technology.The new district of Chongqing iron and steel (group) Co. Ltd. went into productionsince December2009, and the process is designed to achieve the ratio of hot chargecontinuous casting slabs greater than85%. Based on the description above, in order toboth improve the temperature of the slab and the production of defect free slabs for3#caster to realize the hot charge, the solidification heat-transfer mathematical model,conveying cooling heat-transfer mathematical model and stack cooling heat-transfermathematical model were established. The finite difference method was adopted toconstruct the explicit differences equation of slab heat transfer, and the temperaturesimulation soft ware was developed using C#language in the platform ofMicrosoftVisualStodio.NET.Temperature distribution and variation of the slab in solidification process,conveying process and stack cooling process were simulated by using the simulationsoftware. And the comparison between the simulation results and the data measured inproduction site proved that the heat-transfer models can reflect the heat transfer of theprocess. The critical cause of transverse corner cracks was analyzed aiming at the Nb,HSLA steel slabs through the hot tensile test and numerical simulation. To make theslab corner temperature avoid the low ductility region III during bending and/orstraightening is the key for preventing the transverse corner cracks. The asymmetricnozzles have been applied in zone V~VIII. And the quality of the slab was improvedwith these modifications.The effects of different operational conditions were analyzed through thesimulation software, and the results showed that the casting speed and intensity ofsecondary cooling zone are major factors to control solidification rate and quality of theslab in the solidification process. If only the cooling intensity of one cooling zone changed in the secondary cooling zone, there will be great effect on the temperature ofthe slab just in the corresponding cooling zone and the next cooling zone, however, theimpact on next couples of the cooling zone will gradually weaken. So as to improve thetemperature of the slab, the secondary cooling intensity could be reduced accordingto the specific situation of the caster and characteristics of the steel, meanwhile extend-ing the position of the solidification latent heat release is another way to improve thetemperature of the slab.In this paper, the effects on temperature of different initial temperature of slab anddifferent ambient temperature in conveying process were analyzed through theconveying cooling heat-transfer simulation software. And further analysis indicated thatin the existing continuous casting production process and delivery system, the temperat-ure of slab surface and within a certain range below the slab surface were in the two-phase region which was not suitable for hot charge.Under the same stacking conditions, the effects on the temperature with differentambient temperature, stacking blocks and slab thickness were also analyzed. Andstacking time-period to reach the traditional cold charging temperature was calculatedwith different cross-sections, different stacked form of the slab which provides theoreti-cal guidance for stacking space and stacked time in the actual production process.The Hydrogen content was reduced by stack cooling in steelmaking plant. In viewof the fact that Hydrogen diffusion coefficient is related to the slab temperature,one-dimensional diffusion of hydrogen mathematical model was established basedon the stack cooling heat-transfer mathematical model. The hydrogen diffusionmathematical model can be used to calculate and analyze how long time it took to avoidflake and hydrogen embrittlement.