Inclusion Control Of X80 Pipeline Steel Tundish Station Laboratory Experimental Study On The Thermal Simulation

The 21st century can be described as the peak of the construction of gas pipeline in china,however,total domestic rate of steel line pipe is not high,showing that it is an urgent need for china to to accelerate the research and development of high-grade Pipeline.Development of current pipeline projects tends to be large-diameter,high-pressure rich gas transmission,thick wall of subsea pipelines as well as cold and corrosive service environment.Therefore the modern pipeline steel should have high strength,low Bauschinger effect,high toughness and resistance to brittle fracture,low welding carbon and good weld-ability,corrosion and resistance to HIC and H2S.However,non-metallic inclusion reduces the plasticity,toughness and fatigue life of steel,so hot and cold workability of steel as well as the deterioration of certain physical properties are bad,these have a direct impact on the steel strength,elongation,toughness,machinability,corrosion resistance,surface finish properties,welding performance and other aspects.So study of inclusions is adsorbed and removed as much as possible in the casting process is particularly important.Different covering agent and casting temperature on adsorption influence of inclusions as well as oxidation resistance discipline of different covering agent are studied in this subject.Firstly,we can conclude from the investigation of operation process and technology,and analysing the sample especially with defect that the operation is stable as well as low content of oxigyen and nitrogen.The inclusion of samples without calcium treament is mianly Al2O3.While samples under calcium treament is mainly CaO-Al2O3.Moreover the latter has a higher CaS content.Secondly,theoretical calculation,calculate different components of the covering agent influence on the slag property,conclude that appropriate increase alkalinity and lower Al2O3 help improve the fluidity of slag.And the effects of different temperatures on the inclusion float,conclude that increase casting temperature can reduce the viscosity of the slag and increase the speed of floating inclusions.Finally,we do the thermal simulation experiment and analysis the samples.We find that increasing the alkalinity of tundish covering agent in a certain range doing benefit to improve the purity of the liquid steel.With the increasing of Al2O3 from 10%to 30%,the total oxygen is ascending.When it reaches the 40%,the total oxygen is increasing markedly.The total oxygen content drops from 0.0035%to 0.0028%when the temperture changes from 1520?to 1560? and the mean diameter is also smaller.So higher temperture is good for improving the purity of the liquid steel.Enhancing the alkalinity of tundish covering agent and premelting the covering agent lead to the low total oxygen and nitrogen content.