| Slab surface crack is a common defect in the continuous casting of low alloy peritectic steel.The research of the ordinary low alloy peritectic steel’s slag is mainly concentrated in the influence that peritectic reaction on billet quality. No the contrary, the research on the relationship between the solidification characteristics of low alloy steel and the performance of the slag has had a signicant impact on the quality of continuous casting products. The study protocol was performed by the analysis of the low alloy steel solidification characteristics, put forward the performance optimization scheme of the mold flux. It has important significance to improve the quality of continuous casting billet, meanwhile,improve the enterprise efficiency.Regard the 16MnD-R continuous casting slab of a steel company in Jiangxi as the research object and based on the condition that molten steel composition and casting machine parameters are normal,the paper studyed the matching problem between physical and chemical properties of mold flux and slab quality,and it discussed the relationship between mold flux composition 、 physical and chemical properties and low alloy peritectic steel.According to the requirement of the physical and chemical properties and preparation principle of mold flux,adjust the mold flux composition and study to optimize mold flux physical and chemical properties on the basis of use the original mold flux.Through the metallographic analysis of the steel, it is concluded that the initial crack is produced at every stage of the casting slab’s solidification. According to the type of alloy elements in steel, the solidification characteristics and the mechanism of induced crack in mainly brittle temperature range are analyzed. The mechanism of low alloy peritectic steel’s surface crack for the following three points:(1)The first brittle temperature range(1495℃~1394℃) is the peritectic reaction leading to a severe contraction of the lattice.Produce the intergranular crack in the stress concentration;(2)The formation of TiC increases the strength of the slab by dispersion strengthening, the increase of the strength of the casting billet is higher, and the crack tendency increases when the heat flux is not uniform;(3)The third brittle temperature range(700℃~600℃),the TiN begins to precipitate indirectly to reduce the plasticity of the cast slab.Meanwhile, the transformation from austenite is gradually transformed into ferrite and pearlite. Due to the large intensity difference,it is easy to cause stress concentration.Based on the physical and chemical properties of the original casting powder, the idea of improving the basicity, melting point, viscosity and decreasing the crystallization rate was put forward. According to the relationship between the physicochemical properties and composition of slag. Stage of reducing the content of part components of the original casting powder. By using Melting point measuring instrument, Rotary Viscometer, DSC to carry out the experiment of melting point, viscosity and crystallization property, it was determined and analyzed to obtain a more suitable component with the theoretical requirement. Finally, on the basis of the protection of slag, Alkalinity increased from 1.26 to 1.31,%Na2O decreased by1.31%,%F- decreased by 1.75%, and%MgO decreased by 0.45%.The paper analyzes the problem of the original mold flux according to the solidification characters and the formation mechanism of crack of the low alloy peritectic steel,which made the physical and chemical properties of mold flux is more matched with the theoretical requirements.On the one hand,it could effectively weaken intergranular crack tendency of the peritectic reaction;On the other hand,it could improve the uniformity of heat transfer of slag film,which can provide theoretical reference and experimental basis for reducing the generation of 16MnD-R continuous casting slab surface crack and the selection of mold flux for low alloy peritectic steel. |
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