Abstract: To solve the problems such as relatively big dead zones,insufficient flotation of inclusions and high casting remnant in tundishes when producing high quality interstitial-free (IF) steel,a series of optimizing measures were practiced in water modeling experiments. The results show that the fluid flow manifests an obvious up-ward trend using the high dam with two upward holes,the minimum residence time increases by 12.5%,and the dead zone decreases by 36%. In the end of casting,liquid steel can flow out through the holes avoiding a large amount of steel between the dames,the theoretical casting remnant declines from 9 to 4.5 t,and the metal yield increases obviously.
Abstract: A water model was builted by employing 1:4 ratio to simulate 210 t multi-function RH devices. The flow pattern of molten steel and the influence of argon blowing quantity,snorkel insertion depth and the number of argon blowing holes on the flow field of molten steel and mixing time were investigated by the water model. The results show that a main backflow and lots of small backflows exist in the steel ladle,and the decline fluid flow from the down tube forms a liquid-liquid two-phase flow,which plays a critical role in mixing and transforming in the steel ladle. The conclusion about ‘short flow’ that exists between the down tube and the offtake pipe in early studies is denied by the flow pattern in the RH steel ladle in this paper. The argon blowing quantity,snorkel insertion depth and the numbers of the upper and lower argon blowing holes influence the mixing time of molten steel obviously,but the argon blowing quantity and the number of lower argon blowing holes are stronger.
Abstract: Deoxidization,inclusion control and dehydrogenation were analyzed theoretically and the process experience was carried out to study the basicity of slag and the refining time during refining high-speed heavy rail steel. The theoretical analysis results indicate that high basicity slag is propitious to deoxidization in LF refining,and in order to prevent the precipitation of 2CaO·Al2O3·SiO2,the contents of Ca and Al in the steel should be controlled to be lower. The process experience shows that the contents of total oxygen and hydrogen become already stable after 15 min refining and the slag basicity has not obvious influence on the deoxidization during RH refining,but high basicity induces to increase fragile inclusions in the steel. During high speed heavy rail steel refining,the slag with a higher basicity of 2.5 to 3.0 can be used in LF refining,but the basicity of slag should be suitably reduced (about 2.0) in RH refining,and the goals of deoxidization,inclusion control and dehydrogenation can come true after RH refining for 15 min.
Abstract: Factors associated with the generation and consumption volume of coal gas in steelmaking were studied through the gray correlation analysis method. A forecasting model of coal gas was established on the basis of the relationship of Shisteel's generation and consumption volume of coal gas with related influencing factors. An optimization system of coal gas was developed for realizing a rational application and distribution of coal gas.
Abstract: In order to continuously forecast the carbon content in a RH molten bath and control the carbon content at the RH terminal point,the off-gas flow rate was analyzed and the content of CO + CO2 in the off-gas was monitored continuously. Based on carbon balance calculations,a decarburization mathematical model was established for the 250 t RH in a steel plant. Calculation results from the model showed that the precision of carbon content at the end point of RH treatment was ±5×10-6 for ultra-low-carbon steel (w[C] ≤ 30×10-6). When the content of CO + CO2 in the off gas was lower than 5% in the late period of RH decarburization,the decarburization rate was lower than 10-6 min-1,so decarburization could be determined to finish. In combination with site technological conditions,the effects of the pressure drop platform and oxygen blowing operation on the RH decarburization rate were studied.
Abstract: De-titanium of hot metal pretreatment has been applied in the metallurgy industry. Carbon,silicon,manganese,and phosphorus may be oxidized during the process of de-titanium. The thermodynamic calculation and thermal simulation experiment show that low temperature is beneficial for the de-titanium reaction. The content of silicon in hot metal declines proportionally to the content of titanium,while the contents of carbon and manganese change little. The oxidization of carbon in hot metal depends on the temperature,and the higher the temperature,the easier the oxidization of carbon. To remove more titanium,a lower content of silicon and a lower temperature of hot metal are requisite. Apart from these,it also needs to control the oxidation of carbon.
Abstract: Based on the analysis of thermodynamics and kinetics of the titanium removal process from hot metal by the powders injection,a kinetic model was built to calculate the removal amounts of titanium,silicon,and carbon with the change in residence time in hot metal for different sizes of injected particles. With the help of the calculated actual residence time,it can be concluded that the particle size of titanium removal agents with a high content of iron oxide in the range of 0.5 to 0.8 mm is more suitable for titanium removal. The experiment in the induction furnace was performed to study the relationship between titanium removal and silicon removal of the titanium removal agents. The results show that titanium removal and silicon removal proceed synchronously,the related ratio of titanium removal amount to silicon removal amount is in the range of 0.8 to 1,and the removal efficiencies of titanium and silicon are both in 40%-80% after 30 min treatment. It is found that in the industrial practice,the particles injection with a high content of iron oxide as the titanium removal agent should be chosen firstly and the optimal effect can be attained.
Abstract: Based on the principle of Coriolis force and the structure of 120 t combined side and top blowing AOD converter,the relationship between Coriolis force and the AOD was analyzed and calculated theoretically. The results show that Coriolis force affected AOD's flow field by the action on the gas flow of top and side lances. As to the AOD converter in this research,it is found that the deflection angles of top gas and side gas from outlet to bath surface generated by Coriolis force were 7.92×10-8 (°) and 1.88×10-4 (°),respectively,showing that the influence of Coriolis force on side gas was greater than on top gas.
Abstract: In order to play the role of refining high quality steel and process rhythm adjustment ability of ladle furnace, the molten steel composition adjustment and optimization in ladle furnace process were researched. The work would help to realize fast and accurate alloy calculation, reduce processing cycle, and improve process rhythm adjustment ability. The work was also in favor of realization of automatic weighing,automatic addition as well as reduction of labor intensity. It would achieve the lower limit control for the molten steel composition and reduce alloy consumption,especially,for the precious alloy. It also would realize narrow composition control for molten steel,improve the quality of steel and achieve a material to be multi-purpose,etc. In order to establish the model of molten steel composition adjustment in ladle furnace,the derivation process and analysis of alloy calculation formulas were given for the first time. The flow diagram for the ladle furnace molten steel alloy composition fine-tuning was given. And a foundation for the ladle furnace process optimization had been lain.
Abstract: In order to optimize the production process of ultra low carbon aluminium killed steel blooms,a large number of experiments were conducted on the basis of the existing equipment and process conditions in certain iron and steel plant and the BOF-LF-RHbloom caster process was established. A series of optimizing measures were practiced,such as quality control of initial converter molten steel,ladle top slag modification and content control,process optimization for RH,and calcium treatment. The process parameters were obtained after taking the optimizing measures:the oxygen content,0.04% to 0.08%; the final carbon content,0.035% to 0.05%; the (FeO + MnO) content after adjusting the refining slag,< 3%; and the[Ca]content after calcium treatment, 0.002% to 0.003%. As a result,the problem of nozzle clogging has been solved,the average heats of continuous casting has increased to more than 8 heats,and the quality of final products has already reached a high level:the carbon content < 50×10-6 and the total oxygen content ≤ 30×10-6.
Abstract: Chemical composition,inclusions,billet equiaxed rate,hot-rolling,cold rolling and annealing process have great impacts on deep-drawing properties of the materials. Combined with the actual technology level of hot-rolled SUS430 stainless steel in Shandong Taishan Iron & Steel Group Co. Ltd.,the study focused on cold-rolled and annealing process. Through comparative analysis,it is concluded that annealing hot-rolled sheet,followed by pickling and a cold rolling with a reduction rate of 80%-85% can make the cold rolled annealed sheet product has excellent deep drawing properties.
Abstract: Experimental studies on reduction behaviors of Fe and Ni in Fe-Ni-O-C systems (NiO + C,Fe2O3 + C,NiFe2O4 + C, NiO + Fe2O3 + C,and Ni + Fe2O3 + C) under different conditions were carried out by differential scanning calorimetry (DSC) analysis and X-ray diffraction (XRD) detection. The results show that due to the formation of NiFe2O4 and Fe-Ni alloys,the starting temperature of the NiO + Fe2O3 system is higher than that of pure NiO,while both of the temperatures corresponding to the maximum reduction rate and ending point are lower than those of pure Fe2O3. Compared with the system of NiO + Fe2O3,the reduction of NiFe2O4 shows higher starting and ending temperatures and lower reduction rates. The reduction of Fe2O3 by C could be divided into three stages,and the presence of Ni can obviously promote the transfer of iron oxides (Fe2O3,Fe3O4,and FeO) into metallic Fe. The data reveal that the reduction process of NiFe2O4 by C can also be divided into three stages,and the products in different stages show great difference.
Abstract: The smelting of non-quenched and tempered N80 steel for oil well piping by basic oxygen furnace (BOF) in Angang was investigated by systematic process design,laboratory experiments,industrial test and manufacturing production. Instead of conventional quenching and tempering process,the chemical composition of the steel was designed by V and N microalloying. Then the smelting process and the process control points of the steel for mass production in Angang steel were determined,especially the regression equation of endpoint carbon content,oxygen content and temperature under actual conditions as well as the VD dynamic model of increasing nitrogen by bottom-blowing. Analysis results of data measured from continuous production show that the non-quenched and tempered smelting process is stable,the chemical composition and metallurgical process were reasonable,moreover the mechanical properties and service performance can meet the specific requirements of oil well pipe production and the standard of API Spec 5CT.
Abstract: Dephosphorization treatment was utilized in the clean steel process in Shougang Jingtang Iron & Steel United Co. Ltd. Based on the first 58 heats tests,the practical operation process were established,especially for slag making,oxygen injecting,and temperature controlling. The stable and efficient method for low-P content and ultra-low-P content steel production was obtained. According to the experiments results,the average P content (mass fraction,so as the following) in the dephosphorization converter is 0.017%,the C content is 3.69%,and the converter terminal temperature is 1 350℃. Moreover,the P content of 10 heats is below 0.015% with the lowest content of 0.008%,which meets the requirement of ultra-low-P steel. The factors which can affect the dephosphorization process,such as silicon content,carbon content,converter terminal temperature,slag basicity,and oxidizability were investigated. The results demonstrate that when the silicon content is below 0.45%,dephosphorization is relatively more efficient. As the converter terminal temperature increases,the dephosphorization result becomes worse; however,to guarantee the temperature in the de-carbon converter,the dephosphorization converter terminal temperature is fixed at 1 350 to 1 380℃. The reasonable carbon content in the dephosphorization converter is 3.3% to 3.8%. To meet the dephosphorization requirement,the basicity (R) is controlled between 1.8 and 2.2. Enhancing the ore addition and keeping the higher lance position are suggested to increase the FeO content in slag to increase the dephosphorization efficiency.
On the basis of laboratory and industrial converters,some tests were carried out in order to improve dephosphorization in steelmaking. The results show that stirring intensity,conversion temperature of carbon-phosphorus oxidation reactions,carbon content of hot metal and slag compositions have significant effects on the dephosphorization under the top and bottom blowing conditions. A formula for the distribution ratio of phosphorus was established,which included carbon content and agitating factors,and a dephosphorization reaction rate equation was verified by test data. While the oxidizability of the molten bath was investigated,a blowing index for dominating the iron-oxidation in the molten bath was suggested to adjust the distribution of oxygen between slag and hot metal. In practical operations,both the dephosphorization and the peroxidation of iron in the molten bath were improved by controlling the top and bottom blown conditions and the slag compositions.
Abstract: In order to promote hot metal desulphurization,Al is used to deoxidize during molten iron pretreatment. Because of the high carbon content of hot metal,Al and C exist in hot metal simultaneously. Determinant conditions of Al4C3 precipitation were investigated and the effect of Al4C3 on aluminum deoxidation was analyzed. The value of aAl4·aC3 product was calculated by using a thermodynamic method and then the equilibrium of Al-C-O was studied. According to the calculated value of aAl4·aC3 product,the Al-C equilibrium curve was plotted and the equilibrium was analyzed to determine the composition range in which Al4C3 can precipitate from hot metal.
Abstract: The interrelations among CO,CO2,O2 and N2 in electric arc furnace (EAF) off-gas as well as the effects of oxygen flow and the pool's carbon content on EAF off-gas composition were investigated to perfect studies on the variation laws of EAF off-gas composition. The result shows CO appears under the existence of a lot of CO2,and its content increases with increasing CO2 content. The O2 content is in a linear relationship with the contents of CO2 and N2,but in an exponential relationship with the CO content. As the oxygen flow increases,the contents of CO and CO2 increases,the contents of O2 and N2 reduces,and the utilization rate of oxygen improves. The contents of CO and CO2 achieve the maximum when the mass fraction of carbon in the pool is about 1.3%.
Abstract: The computational formulas of CO2 partial pressure pCO2 and[C] activity coefficient fC,% under the condition of high carbon concentration and low temperature were derived from the analysis of limestone decomposition and CO2 oxidation in the early stage of BOF steelmaking by the thermodynamic method. It is shown that the equilibrium decomposition reaction temperature of calcium carbonate in limestone near the surface of molten iron with high carbon concentration and low temperature is much lower than that under the standard state. The reaction tendency of limestone decomposition increases as the furnace temperature rises,and the reactions of CO2 with[C],[Si],[Mn]as well as Fe(l) can occur spontaneously as the same reaction sequence of oxidation by O2 in the early stage. The value of pCO2 under the condition of high carbon concentration and low temperature is very small,near the value of 0.002 2 to 0.000 5pΘ in the early stage of BOF steelmaking,so all of the CO2 produced from the limestone decomposition reaction can be thought to participate in the oxidation reaction of molten iron.
Abstract: In the process of vacuum oxygen decarburization (VOD) refining for stainless steel,the vacuum boiling of molten slag and steel is a kind of intractable and ubiquitous metallurgical problem. The generation,performance,and harm of vacuum boiling were described. Some effective measures to prevent and control the vacuum boiling were introduced. The results show that,the prevention can be realized by stabilizing the initial condition of melts and strengthening the management of ladle state; controlling the process and technical parameters of VOD vacuum refining reasonably is the key to avoid vacuum boiling; in addition,the innovatory design of the VOD vacuum cover can also weaken the harm of vacuum boiling to a certain extent.
Abstract: A small experimental furnace was established,the hot simulation test for coherent jet heating cold metal material was conducted,the flame was measured,and the off gas composition was sampled and analyzed in different stages. The results show that the coherent jet flame presents the different characteristics in different stages,and the composition of combustion products is in change. Under the effect of cold metal material,little CO2 appears,O2 increases,and CO decreases; in the melting stage,O2 rises and CO reduces gradually,and the mass fraction of CO2 stays about from 1% to 2%; compared the decarburization stage with the melting stage, O2 reduces,CO increases,and CO2 increases little; in the decarburization stage,the carbon content in molten steel reduces gradually, CO2 and O2 rise a little,but the CO content reduces violently. Every composition in the coherent jet flame connects with each other,CO content increases as O2 content reduces; in the melting stage,CO content increases as CO2 content increases,but in the decarburization stage,CO content reduces as CO2 content increases.
Abstract: Based on the characters of high-phosphorous oolitic hematite,the dephosphorization research was carried out with the method of coal-based direct reduction,and Hami coal was used in this experiment. The results show that it can get the iron fine with the lowest mass fraction of P 0.031% in the lab after the processes of coal-based direct reduction and magnetic separation. To get the results,it should insure the best reduction temperature and the proper amount of adding carbon (in this experiment,the best reduction temperature is 1 250℃,the mass ratio of ore to coal is 1.25). The wet balls require the proper binary basicity(R ≤ 0.8),and the proper ore size (the ore size is below 2 mm),and finally the reduction time is required to last until the balance of the reaction (50 min).
Abstract: In view of the serious tundish nozzle clogging and less casting sequences in casting SPHD low-carbon low-silicon Alkilled steel that produced by LD-RH-CC process in a factory,the effects of adding the fluorite into the RH slag on the inclusions and castability of SPHD steel were studied. The results show that the main component of the blockage is Al2O3 -CaO-MgO with more than 70% of Al2O3 mass fraction. The mass fraction ratio of CaO to Al2O3 in refining slag can be controlled at 2 by adding some block fluorite through the vacuum chamber of RH furnace which is benefit to lower the content of Al2O3 in the slab and also reduces its particle size. Furthermore,the proportion of CaO·Al2O3 inclusions is increased and the average continuous casting heats can be raised to 3 at least.
Abstract: In order to achieve the higher low-temperature impact toughness,good weldability,and other special requirements of the classification society,Shougang rolling mill line uses the low carbon,Nb/V/Ti,Ni micro-alloying composition design for strict controlling the chemical composition and the steel purity,especially TMCP control system. The E36/40,F36/40 grade ship plate was developed,which has the low alloying element contents,less process,the good low-temperature toughness and welding properties. E36/E40 grade high-strength ship plate made by this technics in Shougang reaches the stable quality for the industrial production. Also the plates have the higher pass rate of performance and yield of product. The production process is reasonable,the quality is stable,and the synthesis performance is excellent.
Abstract: Calcium treatment experiments were carried out on L360QS pipeline steel. The effect of calcium and sulfur contents in molten steel on the inclusions modification was investigated. The result shows that sulfur content in molten steel is decreased to the range of 0.002% to 0.003% and the highest desulfurization rate reaches 85.0%,which achieves the expected result. With the sulfur content increasing,the average CaS + MnS content in inclusions increases in liquid steel,however,the CaS content don' t. The effect of calcium content in liquid steel on inclusions modification is greatly obvious,and almost all inclusions in the pipeline steel with high calcium content are modified into spherical calcium aluminate complex inclusions,in which the CaS is uniformly dispersed,and there are few MnS inclusion and MgO·Al2O3 inclusions. In order to modify both oxide and sulphide inlusions completely,the sulfur content in molten steel should be controlled about 0.002%,and the calcium content in molten steel should be in the range of 0.003 5% to 0.004 0%,as well as the Ca/S should be above 1.9.
Abstract: In order to solve the nozzle clogging in the compact strip production (CSP) process of high-content aluminum steel,the steel composition and inclusions before and after the calcium treatment were analyzed,and thermomechanical analysis based on Bj?rkvall model was also carried out. The results show that the[S]and[Ca]are both too high,as a result,CaS and high-content CaS inclusions are the main causes of the clogging. According to the Al-Ca-S equilibrium diagram,when the high-content aluminum steel, whose[Al]s is at 0.32% to 0.39%,is prepared,in order to prevent the formation of CaS in casting process,the[S]in steel should be controlled less than 0.002 0% and[Ca]in the molten steel should be controlled in the range of 0.004 0% to 0.008 5%.
Abstract: Reaction mechanism between CO2 and molten pool elements at the steelmaking temperature was researched. The related thermodynamics and kinetics were analyzed. The industrial test by top and bottom blowing CO2 was carried out in a 30 t converter. It is discovered that the amounts of smoke dust and T-Fe are reduced by 11.15% and 12.98% on average. Iron loss of slag is lowered by 3.10%,and the contents of nitrogen and phosphorus are decreased by 50% and 23.33% respectively. The new process is absolutely feasible,which will provide a new method for saving energy consumption in BOF steelmaking process.
Abstract: Cleanliness has important effect on the mechanical properties of ship plate steel. The total oxygen,nitrogen,and inclusions in DH36 ship plate steel produced by BOF-LF-RH-CC processes were studied by systematically sampling in each step in steel production and analyzing the shape,size,quantity and components of inclusions by multiple analyzing techniques. The results indicate that the cleanliness of DH36 steel produced with BOF-LF-RH-CC processes is high. The average total oxygen content of the slab is 17.0×10-6,the N content is 29.0×10-6,and the quantity of micro inclusions in the slab is 6.8 mm-2. They are mostly spherical complex oxides and sulfides with the size less than 5 μm in the slab,which meet the requirements of high-level ship plate steel.
Abstract: In order to improve the cleanliness of container steel for the compact strip production (CSP) production line of Wuhan Iron and Steel Corporation,the effect of slag compositions,argon blowing and calcium treatment on T[O] and inclusions was studied by industrial trials. The results show that increasing the ratio of (CaO + MgO)/SiO2 is beneficial to decreasing T[O]in molten steel., but the ratio of (CaO + MgO)/Al2O3 should be considered. The increase of argon blowing time before and after calcium treatment can improve the cleanliness of molten steel obviously. The suitable ratios of (CaO + MgO)/SiO2 and (CaO + MgO)/Al2O3 in the slag are not only beneficial to improving the cleanliness of molten steel but also forming the low melting temperature inclusions of CaO-MgOAl2O3 type. Based on thermodynamic data,a thermodynamic calculation model for the equilibrium of[Ca]and[Al]was given when liquid calcium-aluminate formed in actual production.
Abstract: In order to improve the RH treatment efficiency and the molten steel cleanliness,some investigations on decarburization processes,oxygen concentration in molten steel and inclusion removal during RH refining were carried out. The decarburization efficiency can be improved through the measures of appropriately controlling the contents of carbon and oxygen during tapping,rapidly increasing the RH vacuum,increasing the lifting gas amount,forcing the decarburization,prolonging the decarburization time,expanding the snorkel diameter and optimizing the snorkel shape. The carbon content of final products is controlled within 20×10-6 by controlling the increment. The oxygen content in as-cast slabs and the off-grade cold-rolled products due to inclusions are decreased greatly by the optimization of RH heating technology and the development of silicon deoxidation,magnesium deoxidation and tundish covering modification technology. Through the above measures,reasonable ultra-low carbon steel production and increment controlling techniques have been established.
Abstract: The influences of RH circulation time after Ti alloying,holding time,and the T. Fe content in ladle slag on the T[O] content of IF steel were studied to optimize the RH process parameters and improve the cleanliness of IF steel after RH treatment. The results show that appropriately prolonging the circulation time is favorable for improving the cleanliness of IF steel. The T[O]content of molten steel after RH degassing can be decreased below 30×10-6 if the circulation time is more than 6~8 min after Ti alloying. The T[O]content of molten steel in tundish generally decreases with increasing the holding time after RH treatment,and the T[O]content can be decreased below 35×10-6 when the holding time is more than 30 min. When the T. Fe content in ladle slag is increased by 1%,the average loss rate of Al and Ti is increased by 1.05×10-6 min-1,wherein the loss rate of Al is 0.40×10-6 min-1 and that of Ti is 0.65×10-6 min-1.
Abstract: According to the smelting situations of hot metal with high sulphur content,combined with different produce processes, technologies for controlling the sulfur content during hot metal pretreatment,converter smelting,and second refining are developed. Technologies in clean steelmaking such as increasing the cleanness of steel,quantity and shape control of non-metallic inclusions are formed. Clean steel,such as rail steel at a speed of 350 km·h-1 and electric steel,are produced. As for the high speed rail steel,over 95% of the steel has the[S]content ≤ 0.008%,the content of T[O]deceases to below 0.0015%,and the distribution and shape of inclusions are controlled effectively. The desulfurization rate of low-sulfur electric steel can reach about 20%,and the content of[S] in products is controlled to about 0.006%.
Abstract: The solidification structure and inclusions of high-purity ferritic stainless steel stabilized with Ti or Nb were investigated by the optical microscopy (OM) and scanning electron microscopy (SEM). The results showed that Ti could increase the isometric crystal ratio and Nb could refine crystal size in the high-purity ferritic stainless steel. The composition and status of inclusions were all significantly different in the high-purity ferritic stainless steel stabilized with Ti and Nb,respectively.
Abstract: The characteristics and reasons of C,Si,Mn,P,S composition segregations in low carbon high sulfur free cutting steel were researched by chemical analysis and hot hydrochloric acid. The results show that the segregation degree of elements (C, Si, Mn, P, S) is between 0.9 and 1.1,S and P elements are negative segregation at the billet center region,and the center area of continuous casting billet is porosity. The analyses show that the center porosity is the main reason of element negative segregations at the center area.
Abstract: The control of oxygen content and composition and the transformation conditions of non-metallic inclusions in gear steel are calculated with the thermodynamic calculation software Factsage. The results show that the composition of non-metallic inclusions with high plasticity in 20CrMoH steel is as follows (mass fraction):SiO2 0% to 10%,Al2O3 22% to 55%,CaO 42% to 60%,and MgO 5% to 10%. Under this condition,the mass fraction of aluminum in molten steel is above 0.020%,that of calcium is above 0.7×10-6,and the activity of oxygen in molten steel is about 0.000 5%. If the compositions of refining slag with CaO > 40%, Al2O3 ≤ 37%, MgO 10%, (% CaO +% MgO)/% SiO2=10,and the SiO2 content as low as possible are selected,Al2O3 and MgO·Al2O3 in molten steel can transform into calcium aluminates with low melting point. It is found that the contents of T[O]at the end of LF and RH refining both decrease with the increase in slag basicity,and the content of T[O]decreases with increasing the content of Al2O3 in the slag. In the refining process,the composition of the non-metallic inclusions changes in order of "inclusions of the Al2O3 system→inclusions of the MgO-Al2O3 system→inclusions of the CaO-MgO-Al2O3 system",among which the change of inclusions of the MgO-Al2O3 system to inclusions of the CaO-MgO-Al2O3 system is inwardly from the outside surface and the reaction speed is relatively slower. Thus,at the end of the ladle furnace refining (LF),there are still many unchanged MgO-Al2O3 system inclusions. The T[O]content of the steel significantly affects the composition change of the inclusions and decreasing T[O]content favors the change of inclusions.
Abstract: The sizes,quantity,distribution,and compositions of inclusions in the surface layer of IF slab produced with the BOFRH-CC process were synthetically studied by means of total oxygen and nitrogen content analysis,optical microscopy,scanning electronic microscopy (SEM),energy dispersive X-ray spectroscopy (EDS),and metal original position analysis (OPA). It is found that reoxidation is serious during the unsteady casting period,and the number of large size inclusions increases obviously; the number of inclusions at the position of 1/4 in slab width is higher than that at the edge and the center of the slab; with the increase of the distance to the inner arc surface,the average size of the inclusions drops and the ratio of the inclusions larger than 10 μm decreases; the number and size of inclusions in the surface layer are obviously larger than those in the inner of the slab,and the amount of inclusions at the position of 6 mm from the inner arc surface is the highest.
Abstract: Inclusions in a 5.0-t H13 ingot were studied by dissection. Morphologies and compositions of the inclusions were studied by scanning electron microscopy and energy dispersive spectrum,and the distribution of the inclusions was studied by T[O]analysis and metallographic microscopy. Results show that the average total oxygen in H13 ingot is high and reaches 27.8×10-6,so further refining is required. The inclusions in H13 are mainly near-spherical CaO-Al2O3-SiO2 inclusions,angular TiN-VN inclusions,large linear VC-CrC-MoC inclusions distributed in grain boundaries,and a few CaS-MnS inclusions. Large VC-CrC-MoC inclusions are harmful to the toughness of H13 steel,which should be controlled in following refining. The total oxygen and inclusions are uneven in ingots,the segregations of inclusions and total oxygen are negative around the core of the ingot head,while they are positive in the center and the lower part of the ingot; meanwhile,it is also found that the amount of larger inclusions in the center and the lower part of the ingot is higher. Inclusion segregation index is put forward to describe the segregation degree of inclusions,which is 0.75 to 0.85 around the core of the ingot head and 1.2 to 1.3 in the center and the lower part of the ingot.
Abstract: The utilization status of iron-containing sludges & dusts in eight domestic steel plants including typical EAF short route and BOF long route metallurgical processes was investigated,and the basic properties of iron-containing sludges & dusts were studied using X-ray fluorescence spectrometry,chemical analysis,size distribution analysis,X-ray diffraction,scanning electron microscopy and other analytical methods. The results show that the steelmaking sludges & dusts have high contents of Fe,Ca,and Zn. They can not only be recycled inside the steel plants,but also can be used to develop high value-added products,which relate to the chemical and materials industry. There are more differences in particle size,specific surface,and moisture for the sludges & dusts from different processes. And the iron is present as magnetite,ferrous oxide,hematite,calcium ferrite,and metallic iron,and zinc exists in zinc ferrite. Such above factors must be taken into consideration when the steelmaking dust is studied and utilized. At present,the proportion of steelmaking dust for sale is large and some is used as the sintering raw material,and a small portion of steelmaking dust is used for the slag forming agent. Considering the low utilization levels,relevant technology should be studied to utilize iron-containing sludge & dust efficiently.
Abstract: Laboratory shear test was used to evaluate the shear strength of epoxy polymer overlays on cement interfaces and to analyze the influence of factors such as shearing rate,temperature and membrane thickness on the shear strength. The result indicates that the shear strength rises in a power exponent law with the shearing rate increasing,but falls gradually with increasing temperature. In the experiment,the shear strength,when at 60℃,reaches its lowest point,but much higher than those of other road bonding materials. In a semi-logarithmic coordinate system,the shear strength is less affected by temperature,almost approaching a linear change,in comparison with bituminous materials. The shear strength firstly rises and then falls with increasing membrane thickness. The optimum membrane thickness of Mark-135 is 0.28 mm but 1.10 mm for Mark-163.
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
