Abstract: The 22 mm thick X80 hot-rolled coil production process replaces the traditional wide and thick plate production process, which has remarkable advantages in improving the yield, reducing the cost of manufacturing, and improving the outer diameter adjustment of pipeline.Aiming at the unqualified problem of low temperature drop weight tear resistance (DWTT) of products during development and trial production, the morphology of brittle fracture and the segregation degree of composition in slab thickness direction at different proportions were systematically analyzed by scanning electron microscopy (SEM) .It is concluded that the distribution of sulphide and Ca O·Al2O3calcium aluminate composite inclusions at the fracture site is more than that of Ca O·Al2O3calcium aluminate composite inclusions, and the large size effects the drop weight tear resistance performance of X80 pipeline.Also the relationship between high nitrogen content in molten steel and the decrease of drop weight tear resistance performance was analyzed.Moreover, the steel strip manganese sulfide segregation destruction of tissue continuity, easy to become a source of ductile brittle fracture crack.Through the optimization of refining Ca wire feeding technology and the protective casting technology in continuous casting process, improving the centerline segregation degree, decreasing the number of inclusions in steel, can effectively improve the performance of drop weight tear resistance, to achieve a stable development and production of 22-mm thick X80 pipeline steel hot rolled steel strip.
Abstract: The laboratory experiments of inclusions in H13 die steel modified by Ca treatment were employed in a vacuum induction furnace and the inclusions were analyzed using a scanning electron microscope equipped with an energy dispersive spectrometer in the present study.The evolution of inclusions in H13 steel was analyzed based on thermodynamic calculation.And the component and structure of inclusions in H13 steel after Ca treatment were investigated.The results show that the particle size is modified to tiny and the roundness increases after calcium treatment, the ratio of the sum of cross sectional area of all the inclusions to the total area of the observed view fields decreases.The inclusions change from Si O2-Al2O3to Ca O-Si O2-Al2O3- (MgO) , and all the inclusions are in the1400℃low melting temperature region of the Ca O-Si O2-Al2O3- (MgO) ternary phase diagram at the calcium mass content of 12×10-6.Ca S is unable to form after Ca treatment due to the high T.O content of current steel.The Al2O3in complex inclusions would be totally eliminated as the mass ratio of Ca/T.O reached 0.3.The (Mn, Cr) S precipitated on oxide inclusions is detected, and the morphology of complex inclusions is depended on the degree of segregation of Mn, Cr and S.
Abstract: Experimental and theoretical studies were carried out to investigate the effects of the slag and remelting process on sulfur content and steel cleanliness control during electroslag remelting (ESR) process.AS136 die steel was used as the electrode and remelted under three different remelting conditions by using a 4 t ESR furnace.The contents of sulfur and inclusion along the axial direction of ingot products were analyzed.It was found that the sulfur content in ingot remelting with slag S1 (50%Ca F2+30%Al2O3+20%Si O2in mass fraction) ranges from 0.066%to 0.075%in mass fraction, which can satisfy the requirement of AS136 steel (the sulfur content ranges from 0.05%to 0.1%in mass fraction) , but the levels of B-alumina type and C-silicate type inclusions are higher than the standards.Under the condition of slag S3 (70%Ca F2+28%Al2O3+2%MgO in mass fraction) combined with extra 4.5%MgO in mass fraction continuously added into molten slag during the whole ESR process, the macrosegregation of sulfur along the height of ingot can be improved, the oxygen and inclusion contents reduce.Constant addition of extra amounts of MgO to the molten slag with the increase of slag temperature and Si O2content in slag during the remelting process can improve the macrosegregation of sulfur distributed along the axial direction of ESR ingots.
Abstract: With the addition of Al, the type, amount and precipitation temperature of inclusions in high strength steel for automobile will change.The characteristics of inclusions including amount, species and precipitation temperature in three typical automotive high strength steels with different Al contents were investigated by oxygen and nitrogen analysis, scanning electron microscopy (SEM) , and thermodynamic calculation.The results show that the mass fraction of Al in steel increases from 0.054%to 1.35%, the mass fraction of T[O]in steel decreases from 0.00150%to 0.00075%, and the number of inclusions decreases from 38.28 mm-2to 28.12mm-2, the number of inclusions in steel tends to decrease.With the increase of Al mass fraction in the steel, the evolution route of main oxide inclusions is Al2O3·MnO→MgAl2O4, the main aluminum inclusion changes from Al2O3to Al N;and the evolution route of sulfide inclusions is MnS to MgS.The thermodynamic calculations indicate that the formation of Al N inclusions is related to the Al content in the steel, and the Al N inclusions in steel with high Al content are easier to be formed.The precipitation temperature of Al N increases with the increase of Al content, and the precipitation temperatures are 1375, 1528 and 1561 K, respectively.
Abstract: There are strict requirements for non-metallic inclusions in bearing steel, especially for Type-D inclusions.To analyze the formation mechanism of Type-D inclusions in high-frequency detection defects of GCr15 bearing steel bar sample in domestic steel plant and give the effective controlling measure, the inclusion evolution in bearing steel production process before and after optimization was investigated by ASPEX automatic scanning electron microscope.The results show that, the main formation mechanism of calcium aluminate Type-D inclusions present in the original process includes two aspects:one is the high basicity of refining slag, resulting in the high Ca O activity in slag.The other is the strong stirring in vacuum degassing (VD) process, providing good kinetic conditions for slag-steel reactions.The bearing steel production process is optimized from the basicity of refining slag and the vacuum degree of VD process.After optimization, the inclusions change from calcium aluminate to spinel type, and the formation of Type-D inclusions in bearing steel is reduced.Meanwhile, the high cleanliness of bearing steel is maintained.
Abstract: The influence of oxygen, temperature, and Bi on the morphology of MnS inclusions in free-cutting steel was studied using thermal experiments, chemical analysis, scanning electron microscopy (SEM) research, and thermodynamic calculations.The results show that high oxygen content, high temperature heating, and Bi can effectively reduce the aspect ratio of inclusions in steel and improve the proportion of large particle size inclusion.Statistical analysis reveals that the aspect ratio of MnS inclusions reduce when the total oxygen content becomes higher.The aspect ratio of inclusions increases as the area of a single inclusion in as-cast steel or rolled wire increases.With the increase of the heat treatment temperature, large particle inclusions were found in samples, and the contour of inclusions became clearer.The aspect ratio of inclusions with an area of 0-5μm2became less than 2.0 after 900℃and1200℃heating, which was lower than the aspect ratio before heat treatment by 43%.Thermal experiments reveal that in S-Bi freecutting steel with total oxygen (TO) content of 2.2×10-5and Bi content of 0.0010%, the aspect ratio of inclusions with area of 0-5μm2is less than 1.6, which is 20%lower than that after 900℃and 1200℃heat treatment.
Abstract: Comparing the properties of Q345E steels of two different components, it is found that the yield strength and tensile strength of Q345E increase with the additions of microalloying elements Nb and Ti, but the low-temperature impact performance reduces.The results of the equilibrium phase calculation of Nb-Ti steel and C-Mn steel using thermodynamic software Thermo-Calc reveal that the main difference between them is the precipitation of (Nb, Ti) (C, N) phase.Furthermore, three titanium containing high-strength test steels were designed to observe the microtopography of the fracture and the second-phase particles of steels after impact test under scanning electron microscopy.With the increase of Ti, the low-temperature impact performance of steels reduced, and a number of large particles were gathered in the fracture, which were found to be (Nb, Ti) (C, N) using energy dispersive spectrometer (EDS) analysis, resulting in reduced impact energy.The results indicate that Ti deteriorates the low-temperature impact performance of low-alloy high-strength steel Q345E;therefore, it is necessary to control the size of the second-phase particles using controlled rolling and cooling or component design.
Abstract: The addition of Ti O2during the electroslag remelting (ESR) of Ti-containing superalloys can restrain the loss of Ti elements.The physical properties of the slag system are related to the smooth operation of smelting and the excellent quality of products.A five-membered slag system composed of Ca F2-Al2O3-Ca O-MgO, and different contents of Ti O2was designed for ESR of superalloys.The effects of Ti O2content on the melting point, viscosity, density, optical alkalinity, electrical conductivity, and other physical parameters of the slag were studied.Resultsshow that the melting temperature range of the slag is 1264-1296℃.In addition, the melting point of the slag decreases gradually with the increase in Ti O2content and the formation of a low-melting-point phase.The addition of Ti O2can decrease the viscosity of the slag, and this viscosity in the high-temperature region (1350-1550℃) only slightly changes, thereby improving the surface-forming quality of the ESR ingot.The electrical conductivity, optical basicity, and density of the slag system decrease with the increasing Ti O2content from 0%to 9%of the mass fraction.The density and optical alkalinity show no considerable changes, and the five groups of slag are in line with the ESR on the density and optical alkalinity requirements.
Abstract: Inconel 718, a precipitation strengthening nickel-based superalloy, is widely used in aerospace and other high-temperature process industries because of its adequate strength, ductility, and good workability.The increasing demand for alloys with remarkable comprehensive performance necessitates the development of alloys with highly uniform microstructures and highly homogeneous composition;therefore, electroslag remelting (ESR) has attracted much attention in metallurgical circles.However, strong chemical reactions, such as (Al2O3) +[Ti]= (Ti O2) +[Al], usually occur at the electrode-slag interface (ESI) or the droplet-slag interface (DSI) and the metal pool-slag interface (MSI) ;therefore, the concentrations of Al and Ti cannot be maintained within specifications, or the elements cannot be uniformly distributed along the height of the ingots during the ESR process.Consequently, mechanical property deteriorates and the production cost of nickel-based alloy increases.To overcome these issues, in this study, a thermodynamic model for calculating equilibrium content of Al and Ti in a nickel-based alloy during ESR was developed based on the ion and molecule coexistence theory (IMCT) .The chemical composition of slags plays a key role in the physicochemical properties of slags and controls the loss of alloying element during ESR process.Therefore, the respective relations between the activity and activity ratio of individual slag components with chemical composition of Ca O-Si O2-MgO-Fe O-Al2O3-Ti O2-Ca F2slag were studied.Furthermore, effect of the slag composition on the equilibrium content of Al and Ti in Inconel 718 superalloy under various metallurgical temperatures during ESR was investigated.The results indicate that the equilibrium content of Al increases with increasing temperature, however, the equilibrium content of Ti decreases.MgO and Ca F2have little influence on the control of the loss of active alloy elements.
Abstract: In order to realize the effective enrichment of phosphorus in high phosphorus converter slag, using the Ca O-Si O2-Fe2O3-P2O5-MgO-MnO slag with a P2O5content of 10% (mass fraction) as the research object, the form of phosphorus in the high phosphorous slag was studied by the laboratory hot state experiment.The effects of basicity and Fe2O3content on the enrichment of phosphorus in high phosphorus converter slag were investigated.The results show that the phosphorus element in the high phosphorus converter slag mainly exists in the form of n2CaO·Si O2-3CaO·P2O5 (n C2S-C3P) solid solution and the changes of slag basicity and Fe2O3content have no effect on the phosphorus occurrence form.The change of basicity has an effect on the production of 2CaO·Si O2.Too high or too low basicity is not conducive to the enrichment of phosphorus from slag to phosphorus-rich phase.Controlling the slag basicity in the range of 1.5-1.8 is conducive to the full enrichment of phosphorus in slag.Increasing the Fe2O3content in the slag can reduce the precipitation of 2CaO·Si O2and increase the content of P2O5in the phosphorus-rich phase, which is favorable for the enrichment of phosphorus in the slag.
Abstract: A predominantly liquid and MgO saturated slag is preferred in secondary metallurgical processes.It contributes to the mass transfer in molten steel and the extension of the refractory life.In the present study, the saturability of Mg O in quaternary Ca O-Si O2-Al2O3-MgO system in secondary metallurgical slag with low basicity was investigated by commercial thermodynamic software and laboratory experiments.The result shows that in the basicity (Ca O/Si O2) range of 0.5-1.8, the saturability of MgO fluctuates between2%and 39%and decreases with the increase of basicity.The saturability of MgO increases in the MgO saturated phase periclase (MgO) and forsterite (2MgO·Si O2) and decreases in the MgO saturated phase spinel (MgO·Al2O3) with an increase in Al2O3content.Si O2content has a great effect on the saturability of MgO in lime-silicate slag.Besides, the MgO saturability increases with an increase in temperature.
Abstract: The 06Cr18Ni11Ti (321) stainless steel has good corrosion resistance and mechanical properties.However, the addition of Ti leads to the formation of Ti N inclusions, which deteriorates the condition of continuous casting and causes the clogging.The formation of clogging in the submerged entry nozzle (SEN) of 321 stainless steel was studied by scanning electron microscopy (SEM) , energy disperse spectroscope (EDS) and thermodynamic calculation.According to the change of components, three layers in sample were defined:the refractory materials layer, the reaction layer and metal layer from the outer layer to the inner layer of SEN.The results show that the molten steel corrodes the refractory materials of SEN and the high-melting-point slag phase forms.Then Ti N inclusions attach to the inner layer and form curved chain or reticular structure with slag phase, which causes the clogging of SEN.Resultsof thermodynamic calculation indicate that the equilibrium solubility of titanium and nitrogen increases with temperature.There is high Ca/Al proportion in Ca O-Al2O3-Ti O2-5%MgO phase.So controlling the compositions of slag is needed to prevent clogging.
Abstract: Based on the deep dephosphorization process of molten steel out of converter, the various dephosphorization agents for secondary dephosphorization were investigated by laboratory scale experiments.The initial phosphorus content in steel and the amount of dephosphorizing agent added into the tube furnace were firstly determined.And then, the compositions of the Ca O-based and Ba O-based dephosphorization agent were investigated, respectively.The results shows that the best ratio of Ca O-based dephosphorizing agent is w (Ca O) ∶w (Ca F2) ∶w (Fe O) = (65-70) ∶ (15-20) ∶ (10-20) , the best ratio of Ba O-based dephosphorizing agent with Fe O is w (Ba O) ∶w (Ca O) ∶w (Ca F2) ∶w (Fe O) = (10-20) ∶ (55-65) ∶15∶10 and the best ratio of Ba O-based dephosphorizing agent without Fe O is w (Ba O) ∶w (Ca O) ∶w (Ca F2) = (30-40) ∶ (55-65) ∶ (15-20) .
Abstract: Bottom-blowing technology is widely adopted in electric arc furnace (EAF) steelmaking to promote the molten bath fluid flow, accelerate the metallurgical reaction and improve the quality of molten steel.In this study, a water model experiment and a computational fluid dynamics (CFD) model were established to investigate the fluid flow characteristics of molten bath with bottom-blowing in EAF steelmaking process and the effects of bottom-blowing gas on the fluid flow were analyzed.Meanwhile, based on industrial application research, the heat transfer in the molten bath with bottom-blowing was analyzed.Compared with traditional smelting conditions without bottom-blowing, bottom-blowing technology can strengthen the stirring of the molten bath, promote the heating rate and the temperature homogeneity of the molten bath.Hence, bottom-blowing technology greatly improves the efficiency of energy utility in EAF steelmaking.
Abstract: Studying on the Ca O base containing V2O5and Ti O2semi-steel slag, a model of enrichment degree Rci-cjwas built with the help of the ion and molecule coexistence theory, the result was compared with the actual enrichment form of phosphate.The results indicate that with the increasing of basicity, the mass action concentration of 3CaO·P2O5gradually decreases, and the mass action concentration of 4CaO·P2O5gradually increases.While the mass action concentration of 2CaO·Si O2first increases and then decreases.The enrichment possibility range of the C3P+C4P is 87%-94%and the C2S that is the essential substance for the formation of the rich phosphate mineral phase is main calcium silicate compounds.The solid solution 2CaO-Si O2-3CaO-P2O5 (C2S-C3P) and 2CaO-Si O2-4CaO-P2O5 (C2S-C4P) are the primary phosphate enrichment phase in the slag.According to the scanning electron microscopy (SEM) results, X-ray diffraction (XRD) analysis and hypothesis, the containing P2O5solid solution in dark grey area is calculated as2CaO·Si O2-3CaO·P2O5and 2CaO·Si O2-4CaO·P2O5, which is consistent with the theoretical calculation results.
Abstract: Top and bottom combined blown converter has been widely utilized in steelmaking process.Multiple supersonic oxygen jets generated by top blown oxygen lance penetrate into the molten bath and form a penetration cavity on the surface of molten bath, which is the main reaction zone in steelmaking.Therefore, the characteristics of the multiple oxygen jets play a crucial role in converter flow fields and metallurgical performance.Several numerical and experimental studies have been conducted previously to investigate the supersonic oxygen jet.However, most of them were carried out at ambient room temperature by ignoring the high-temperature environment in steelmaking converters.In fact, the characteristics of supersonic oxygen jet are closely related to the ambient temperature.The effect of ambient temperature on single-stream oxygen jet has been previously studied, and it was confirmed that the jet characteristics improve with the increase in ambient temperature.Characteristics of multiple jets generated by converter oxygen lance at high ambient temperatures have not been previously studied.There are big differences between single-stream oxygen jet and multiple jets because the multiple jets deviate from the axis of oxygen lance.The coalescence phenomenon occurs in these multiple jets due to formation of low pressure zone between them.The difference between multiple jets characteristics at ambient room temperature and ambient steelmaking temperature inevitably leads to the difference between penetration cavity and flow fields in the converter, which has never been studied.To reveal the multiple jets characteristics and jet-bath interactions in converters at steelmaking temperature, a three-dimensional fullscale geometric model based on an industrial 110 t combined blown converter was established in this work.Using the combined blown converter model, coupled with standard k-epsilon turbulence model and volume of fraction multiphase model, the effect of ambient temperature on multiple oxygen jet characteristics was studied in detail.Moreover, jet-bath interactions at room temperature and steelmaking temperature were compared and analyzed.The results show that with the increase of ambient temperature, velocity attenuation of the multiple jets is inhibited and the radial expansion of the jets is aggravated.Meanwhile, the multiple jets are heated by the ambient medium, and the final temperature of multiple jets becomes close to ambient temperature, which decreases the jet density.Coalescence between multiple jets is suppressed in high ambient temperature.Research on the jet-bath interactions shows that penetration depth and flow velocity in molten bath are larger at steelmaking temperature because the velocity attenuation of supersonic jet is suppressed.These results indicate that the effect of ambient temperature in multiphase numerical researches is significant and cannot be ignored.
Abstract: The coherent lance technology is widely used in the electric arc furnace (EAF) steelmaking process.It achieves a better metallurgical effect compared with the conventional supersonic lance technology.Herein, to further improve the stirring ability of the coherent lance, the effects of shrouding nozzle arrangement on the flow field and stirring ability of coherent jet were analyzed under two environment temperatures.Based on the results of the numerical simulation and combustion experiment, the characteristics of axial velocity and total temperature distributions has been introduced for researching the impaction ability of coherent jet using various shrouding nozzle arrangements.The appropriate simulation model was built by testing three types of mesh levels.The eddy dissipation concept (EDC) model and chemical kinetic mechanism were adopted to represent the combustion reactions of the O2-CH4jet flame in the numerical simulation process.Resultsreveals that the numerical simulation data shows good agreement with combustion experiment.The initial velocity at the exit of main oxygen Laval nozzle does not change with different shrouding nozzle arrangements.With increase in the distance between the main oxygen and shrouding nozzles, the length of the velocity potential core first increases and then reduces.Moreover, all shrouding nozzle arrangements increase the length of velocity potential core.
Abstract: The application of the bottom-blowing process in electric arc furnace (EAF) steelmaking process can shorten the mixing time of the molten bath effectively;accelerate the removal of carbon, phosphorus, and sulfur;as well as improve the production efficiency and product quality.The velocity field of molten steel flow under different gas flow rates in eccentric bottom tapping (EBT) zone of EAF was simulated using simulation software.The average velocity of molten steel in the EBT zone was increased from 2.805×10-3■flow rates in EBT zone were increased from 100 to 267 L·min-1 (the rest gas flow rates were maintained at 133 L·min-1) .An empirical formula of gas flow rates in EBT and molten steel flow was obtained.A prediction model for carbon content was proposed based on molten steel stirred via bottom blowing during the EAF steelmaking process.This provided theoretical suggestions for the homogeneity of bath and reasonable oxygen supply considering that the kinetic factor of reactions in the bath was the molten steel flow at the end point of smelting.
Abstract: Coherent jet is widely adopted in electric arc furnace (EAF) steelmaking to promote molten-bath fluid flow, accelerate the metallurgical reaction, and improve the quality of molten steel.A water model experiment was conducted and a computational fluid dynamics (CFD) model was established to validate the theoretical model of penetration depth, which was built and modified by mathematical analysis.Resultsshow that the impact law of the coherent jet is similar to that of conventional supersonic jet.With the same jet condition, the penetration depth decreases as the lance height increases.At the same lance height, the penetration depth of the coherent jet is greater than that of the conventional supersonic jet as indicated by the higher k value and jet gas density of the former.
Abstract: Reasonable process parameters in the RH refining process are very important to improve the decarburization rate and shorten the refining time.In view of the problem of long decarburization time of 300-t RH in the IF steel production, SPSS statistical software was used to analyze the correlation relationship between the process parameters of the RH refining process and the decarburization time.Based on large numbers of refining process date statistics and off-gas analysis, the relationship between the process parameters and decarburization time was obtained and the improvement measures were put forward.The results show that the limit vacuum should be reached as early as possible and pressure drop platform should be avoided in the refining process;the addition amount of carbon powder should be no more than 35 kg, the join number should be no more than 2 times and the carbon powder should be added as soon as possible before reaching the ultimate vacuum pressure;oxygen blowing should be controlled before the peak value of CO, and the start time of oxygen blowing should be controlled in the range of 2.5-3.5 min.Through industry technology verification, the average decarburization time is reduced from 21.4 to 18.3 min after the optimization of process parameters, decreasing amplitude reaches14.5%.
Abstract: The mixing behavior of molten steel and slag has an important impact on refining effect in vacuum degassing (VD) process.In the VD refining process, the vacuum condition makes the bottom argon gas agitate the molten steel vigorously, and increase the exposed molten steel area, which not only aggravates the degree of steel slag mixing in the ladle, but also promotes the degassing reaction in molten steel.Moreover, it has an important influence on the desulfurization effect of molten steel.In the actual melting process, the exposed situation of the molten steel can be observed over the slag, but the steel and slag mixing situation in the ladle cannot be observed.Therefore, it has a great practical significance to study the slag mixing behavior in VD refining process under the different process conditions.In the water model experiment, the critical condition of half-mixing and complete-mixing was first defined.And then the impacts of the total blowing flow rate, vacuum degree, and the bottom blowing positions on half-mixing and complete-mixing were discussed.Besides, the effects of critical stirring energy density and stability of flow field on mixing behavior were also analyzed.The results indicate that half-mixing and complete-mixing critical gas flow rate decreases with the increase of vacuum degree in the laboratory condition.And the critical gas flow rate in 2/3R+2/3R is greater than that in 2/3R+center hole.In addition, the fitting formulas of vacuum degree and critical gas flow rate were given.Based on fitting formulas, critical gas flow rate in actual VD process was obtained when vacuum degree was 67 Pa.According to the results, the critical stirring energy density is nearly a constant when the steel-slag mixing reaches the same condition in steady flow field, which indicates that flow character can further influence mixing effect and it is affected by the bottom blowing positions.
Abstract: The present situation and utilization mode of LF refining slag were investigated in detail for more than 30 typical iron and steel enterprises in China.It is found that the treatment method of LF refining slag is relatively simple, the utilization level is low and the waste of resources is serious.Meanwhile, LF refining slag is characterized by high optical basicity, high sulfur capacity, high sulfur distribution ratio, low melting temperature, and low viscosity.So LF refining slag could be recycled in smelting process, but sulfur enrichment is a restriction factor during the cyclic utilization.To solve this problem, the sulfur removal test and metallurgical recycling utilization of LF refining slag were carried out.The results show that sulfur in LF refining slag can be oxidized to SO2by O2, and it has good desulfurization result when blowing air into the slag at 1643 K and 1673 K.Sulfur removal at 10 min by blowing air is over47%, and over 90%at 60 min, and it can meet the sulfur content requirement of LF refining slag used for smelting process.Finally, a simple and efficient method of LF refining slag used for smelting process is proposed, which goes well with current steelmaking process.
Abstract: In regards to the end temperature prediction of molten steel in RH refining, an integrated case-based reasoning (CBR) method based on multiple linear regression (MLR) and genetic algorithm (GA) was proposed.Firstly, MLR was used to intelligently simplify the number of attributes to modify the lack of methods in the accurate selection of influencing factors in general CBR method.Secondly, GA was used to optimize the attribute weights in order to resolve the lack of attribute weights calculation method for similarity computation in case retrieval.Lastly, the end temperature prediction of molten steel in RH refining was realized based on the simplified influencing factors and optimized weights, and using grey relational degree (GRD) in case retrieval.Testing was performed based on the actual production data in RH refining in steelmaking plant, and comparison between MLR method, BP neural network, general CBR method and integrated CBR method was carried out.The results show that integrated CBR method has better prediction accuracy than MLR method, BP neural network and general CBR method in multiple temperature ranges.
Abstract: Melting and gasification behavior of Ca Al cored wire with 0.74-mm steel sheet and better feeding process in 1873 K molten steel in 150 t ladle was simulated, and the influence of different Ca cored wire and composition of liquid steel on Ca recovery were analyzed.The results show that calcium alloy of Ca Al cored wire has smelted before its covering steel sheet melts when cored wire is fed into molten steel, melting time of Ca Al cored wire is 0.92 s, then liquid Ca alloy diffuses into liquid steel.Liquid Ca alloy floats upward to 1.22 m below the liquid steel surface and gasifies when alloy has get enough steam pressure of gasification.The feeding speed of 3.22-4.83 m·s-1for Ca Al cored wire is appropriate to get ideal feeding depth of 2.96 m in ladle with liquid steel.When the elements contents of carbon, silicon and manganese in liquid steel are high, pure Ca cored wire should be used to get bigger Ca recovery, on the contrary, Ca Al cored wire is a better option for low carbon liquid steel with low elements contents of silicon and manganese.
Abstract: To study the influence of slag denaturalization process on the top slag oxidation and inclusions in interstitial free (IF) steel, the slag and steel samples were analyzed and taken from different positions in different slag denaturalization experiments.In the results, the best denaturalization effect is obtained by added the denaturalization agent in argon station, the slag oxidizability, indicated as the content of total Fe and MnO by mass in slag, w (T.Fe+MnO) , decreases by 8.73%.Compared with the slag denaturalization process added the denaturalization agent after RH deoxygenation-alloying and RH refining, the number density of inclusions in slag denaturalization process added the denaturalization agent in argon station is decreased by 38.5%and 36.0%, respectively.After RH refining, the number of inclusions in steel is less, but when the slag is in high oxidizability, the oxygen is transferred from slag to steel, which makes the number of inclusions in steel rise.
Abstract: The morphology, distribution, and entrapped inclusions of bubbles in thick slab of X70 pipeline steels were investigated by peeling layer.The results show that the diameters of 94%bubbles in thick slab are less than 200μm;the bubbles and the entrapped inclusions are common in 8 mm depth from the slab surface, but the defects are hardly found as peeling deeper into the middle of slab, only a small number of defects are shown, presenting a random distribution in this area;the main morphology of bubbles existing in slab are single bubbles and twin bubbles, the calabash bubbles and petal bubbles are also found;the inclusions are mainly in four existent forms:oxides, aggregation in clusters, bubbles in clusters, and ash inclusions.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
