| CAS refining process has been widely used for its low operating cost, simple operation, fast and accurate contral of composition and temperature, high and stable alloy recovery efficiency. CAS refining process can be divided into two steps:One is deslagging process, gas is injected into steel through plug, and float to free surface, break up the slag layer; another is CAS process, adjusting alloy addition compositiom maiNly. To the present problem of CAS refining process in Xin Steel, a physical model has been used in this paper to optimize the appropriate gas flow rate for deslagging and plug position、snorkel depth and gas flow rate in CAS process, while studying the effect of plug positon、gas flow rate and slag layer thickness on deslagging area in deslagging process and flow field in CAS process by mathematical modeling, and established mathematical model is used to study the effect of the important process and model parameters on CAS refining processfinally. On the basis of research results, industial experiment has been done, which can test and verify effect of CAS refining process after optimizion. The result shows that:For the deslagging process, plug position has almost no fluence on deslagging area, gas flow rate and slag layer thickness have a great effect on deslagging area. Small gas flow rate is disadvantageous for deslagging, the thicker the salg layer is, the more difficult it is broken up and the smaller effect gas flow rate has on deslagging, while the gas flow rate varies from480to720Nl/min, diameter of slag eye increase by277mm for the salg layer whose thickness is80mm, and for for the salg layer whose thickness is160mm, the diameter of slag eye increase by111mm. For thickness of slag layer is80mm,120mm,160mm, the gas flow rate for deslagging should be more than600Nl/min,800Nl/min,1000Nl/min,respectively. Slag layer viscosity and the air bubble particles size have almost no influence on the simulated results of deslagging process.For the CAS process, while blowing with single plug, the mixing time is the shortest when plug has a distance of600mm from center of ladle bottom, it is about134s with gas flow rate of600Nl/min; while blowing with double plugs, plug2 shoule be1000mm from center of ladle bottom, and angel of two plugs diametrically is100°or160°. In the CAS mixing process, the gas flow rate at plug outside of snorkel should be small enough so that the slag layer can not be broken up, it is advantageous to mixing; in the CAS process with single plug, high gas flow rate accelerate the motion of steel, shorten mixing time, which is beneficial for mixing but harmful for ladle and snorkel refractory wearing, so the appropriate gas flow rate is600Nl/min～700Nl/min, and the mixing time is124s～137s; Snorkel depth has a great influence on flow field, horizontal velocity of steel at free surface still exists when snorkel depth is shallow, which is disadvantageous to inclusion removal, and there is a large dead zone outside of snorkel when snorkel depth is too depth, which is disadvantageous to mixing, so the snokel depth shoule be about200mm.On the basis of research results, industial experiment has been done, including Q235and JBDR. It shows, the time for snorkel to fall off in the CAS process is about9～15minites, time tempo and link up of temperature accord of present CAS refining process. In the experiment of hot rilled silicon steel, alloy recovery efficiency in optimized ladle reach84%, higher than present ladle of66.6%and ladle without snorkel of42%, for the main function of CAS refining, it can be extend to straight carbon steel、lower-level ship steel、lower-level line pipe and so on. |
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