Research On Mineral Structure Of Mold Slag And Flux Film In Different Slab Continuous Casting

Slab defects often occur in continuous casting production both the popular stability thick slabs and thin slabs which is high-speed and low-cost.It's benifit for thick and thin slab cracks reduced by low heat transmission.Therefore,many scholars have studied on the physical and chemical properties of molten steel,metallurgical processes and equipment,and the properties of mold fluxes.But there is little research focus on the mold slag and flux film.So the mineral struture of mold flux and slag film for different slab casting process was studied.The crystallization process of mold flux for different slab casting process was analysed and the relationship of the crystallization process and mineral struture was found.These can provide a theoretical basis for the optimization of mold slag and improve the surface quality of different slab in continuous casting.The results show that almost all the structures of thin and thick slab mold flux were layered as “crystal layer-glass layer” alternately,and the thin slab films were wider than that thick slab.The microstructure of thick and thin slab films for peritectic steel which were thickness uniformity and that of thick slab films for medium carbon steel were two layers.But microstructure of thin slab film for medium-carbon steel and thick and thin slab for low alloy steel were low thickness uniformity and multi-layer structure.The mineral composition of thick and thin slab film mainly contains melilite,cuspidine and a little of wollastonite and other mineral phase.Crystallization rates of thick slab peritectic steel and medium carbon steel slab are about 80% and 75% respectively,which are higher than those of steel slags of 65% and 60%,low alloy steel slag film crystallization rate was 85%,which was higher than the slab low alloy steel slag film 70%.Simulations for crystallization process show that the crystallization temperature of slab continuous casting mold flux was 1750~1100?,while the crystallization temperature of thin slab mold flux was in 1450~1100?.Thick,thin slab mold fluxes are compatible with the order of crystallization.Firstly,the cuspidine began to crystallize,followed by the precipitation of the magnesiite mineral phase,and then followed by the precipitation of the feldspar,the fake wollastonite and the intermediate product,it shows that the content of the magnesium akermanite was significantly higher than that of the gehlenite,followed by fake wollastonite and intermediates shift to other end products.Based on the research of the relation between the structure of slag film and the crystallization law of slag,it is found that the slab slag is separated into two phases.The first stage is the beginning of crystallization of cuspidine to the end,after the slag crystallization "pause" into the crystallization of birth;the second stage is the conversion process of many other minerals and a small amount of intermediate products.However,the thin slab mold powder crystallization process is a continuous multi-mineral deposition and partial mineral conversion process.This is the main reason that the slab slab crystallization rate and crystal growth are higher than that of the slab slab.