Effect of lump ore ratio on the metallurgical properties of blast furnace charge

We conducted a series of experimental studies on the metallurgical properties of N-lump and F-lump ores used in Baosteel’s blast furnace, including thermal cracking, low-temperature reduction pulverization, reducibility, and droplet properties.The results show that the thermal burst properties of N-lump ore are better than those of F-lump ore.The low-temperature reduction degradation index(RDI) pulverization of the charge is the best when the ratios of N-lump ore and F-lump ore account for 35% each.The reduction performance of the charge is improved when F-lump and N-lump ores are mixed with sinter.In the softening-melting performance experiment, when the proportion of N-lump ore is 40%,the characteristic area value(S) as the charge permeability index is the smallest.When F-lump ore is mixed with sinter, its droplet performance improves compared with that of single F-lump ore.The proportion of F-lump ore should not exceed 15%.

Influence of shielding gas on the mechanical and metallurgical properties of DP-GMA-welded 5083-H321 aluminum alloy

In the present research, 6-mm-thick 5083-H321 aluminum alloy was joined by the double-pulsed gas metal arc welding （DP-GMAW） process. The objective was to investigate the influence of the shielding gas composition on the microstructure and properties of GMA welds. A macrostructural study indicated that the addition of nitrogen and oxygen to the argon shielding gas resulted in better weld penetration. Furthermore, the tensile strength and bending strength of the welds were improved when oxygen and nitrogen （at concentrations as high as approximately 0. 1vol%） were added to the shielding gas; however, these properties were adversely affected when the oxygen and nitrogen contents were increased further. This behavior was attributed to the formation of excessive brown and black oxide films on the bead surface, the formation of intermetallic compounds in the weld metal, and the formation of thicker oxide layers on the bead surface with increasing nitrogen and oxygen contents in the argon-based shielding gas. Analysis by energy-dispersive X-ray spectroscopy revealed that most of these compounds are nitrides or oxides.

Study on metallurgical properties and pellet proportioning technology of stainless steel cold-rolling sludge

With a complicated composition, large rolling sludge has been a focal point concerning neither at home nor abroad have any technologies suitable for bulk utilization of stainless steel cold- production and serious damage to the environment, stainless steel cold- environmental protection for stainless steel enterprises. Up to now, come into being that are not only proper, safe and economical but also rolling sludge. Based on the characteristics of the stainless steel cold- rolling sludge, orthogonal experiments were carried out on pellet proportioning and high-temperature roasting, and major metallurgical properties of sludge pellets were also tested. As the results show, pellets with 30% addition of cold-rolling sludge are qualified regarding their compressive strength, chemical composition and major metallurgical properties. No adverse impact happens to the blast furnace operation when sludge pellets account for 10% of the blast furnace raw materials. Therefore, the technical route applied in this paper is proved simple, feasible and environmentally friendly for cold-rolling sludge treatment.

Effects of SiO_(2) on the preparation and metallurgical properties of acid oxidized pellets

The effects of SiO_(2) content on the preparation process and metallurgical properties of acid oxidized pellets, including compressive strength, reduction, and softening–melting behaviors, were systematically investigated.Mineralogical structures, elemental distribution, and pore size distribution were varied to analyze the mechanism of the effects.The results show that with an increase in SiO_(2) content from 3.51 wt%to 7.18 wt%, compressive strength decreases from 3150 N/pellet to 2100 N/pellet and reducibility decreases from 76.5% to 71.4%.The microstructure showed that pellets with high SiO_(2) content contained more magnetite in the mineralogical structures.Additionally, some liquid phases appeared, which hindered the continuous crystallization of hematite.Also, the softening–melting properties of the pellets clearly deteriorated as the SiO_(2) content increased.With increasing SiO_(2) content, the temperature range of the softening–melting zone decreased, and the maximum differential pressure and the comprehensive permeability index increased significantly.When acid oxidized pellets are used as the raw materials for blast furnace smelting, it should be combined with high basicity sinters to improve the softening–melting behaviors of the comprehensive charge.

Effects of iron compounds on pyrolysis behavior of coals and metallurgical properties of resultant cokes

The utilization of highly reactive and high-strength coke can enhance the efficiency of blast furnace by promoting indirect reduction of iron oxides.Iron compounds,as the main constituent in iron-bearing minerals,have aroused wide interest in preparation of highly reactive iron coke.However,the effects of iron compounds on pyrolysis behavior of coal and metallurgical properties of resultant cokes are still unclear.Thus,three iron compounds,i.e.,Fe;O;,Fe;O;and FeC;O;·2H;O,were adopted to investigate their effects on coal pyrolysis behavior and metallurgical properties of the resultant cokes.The results show that iron compounds have slight effects on the thermal behavior of coal blend originated from thermogravimetric and differential thermogravimetric curves.The apparent activation energy varies with different iron compounds ranging from 94.85 to 110.11 kJ/mol in the primary pyrolysis process,while lower apparent activation energy is required for the secondary pyrolysis process.Iron compounds have an adverse influence on the mechanical properties and carbon structure of cokes.Strong correlations exist among coke reactivity,coke strength after reaction,and the content of metallic iron in cokes or the values of crystallite stacking height,which reflect the dependency of thermal property on metallic iron content and carbon structure of cokes.

Study on the Shaft-Direct Reduction Process with Cold Bound Pellet

The metallurgical properties of cold bound pellet were tested and analysed, and the behaviour and characters of reduction in the shaft were further investigated on the basis of analysis. The experimental results indicated that the metallurgical properties of cold bound pellet could satisfy the demands of the shaft direct reduction. The reduction of ferrous oxide with gas was taken as the domination. The reduction ratio of ferrous oxide with fixed carbon increased with the raising of temperature, and most part of the carbon remained in metallized pellet. The shaft could be smoothly operated to obtain rather higher constant utilization.

Recent collaborative researches between Japanese universities and steel industry on the iron ore agglomeration process

The properties of iron ores used in ironmaking process have been drastically changed in the past couple of decades.Especially,the change has become significant in the last few years because of the considerable increase in the world steel production.The property change of the iron ore is mainly caused by the depletion of the hard and high-grade lump hematite ores.It has led to the increasing use of ores containing a larger amount of goethite/limonite,i.e.,hydro-oxides of iron.Typically,the proportion of pisolitic ores,which are course limonitic ores,has remarkably increased by several times in Japan.Further,large deposits of the fine goethite ores called Marra Mamba have been developed in Australia and exported to Asian countries.Such trends will be continued in future.Since the change of the ore properties affects not only to the productivity and yield of the sinter but also its metallurgical properties in the blast furnace,further improvement in the sintering technology/ process is required including the preliminary treatment process of raw materials.In order to make wide researches concerning the above issues,the research project 'New Sintering Process through Designing of Composite Granulation & Bed Structure' was formed in the ISIJ,which was the collaborative project between Japanese steel companies and several universities.The project was started in 2005 and carried on the wide range of studies for three and half years.Its main objects are the characterization of pisolitic/goethitic ores and the understanding the behavior during the iron ore sintering process.Further,considering the ore characteristics,some basic researches on the optimum designs of raw material blending,granulation,bed structure,and the metallurgical properties of the produced sinter were performed.The project have invented the technical principle of a new sintering process, namely MEBIOS(Mosaic EmBedding Iron Ore Sintering Process),characterized by the composite granulation and bed-structure,aiming to cope with the drastic shift of the ore properties.Another big issue fallen on the steel industry is the global warming.CO,emission from steelmaking industry occupies about 15%of the total value of the artificial emissions in Japan and therefore its reduction is urgently required.In order examine the possibility to minimize or to reduce further the CO_2 emission from the iron ore sintering process,the research project 'Technological Principle for Low-Carbon Sintering' has been formed since 2009 in the ISIJ.In this project,the analyses of the combustion rates of carbonaceous materials and heat transfer in the sintering bed are first examined by referring the previous studies.Further,experimental works will be conducted on the combustion/oxidation characteristics of biomass charcoal,some organic wastes,steel can scraps,mill scale and partially reduced iron ores as alternative agglomeration reagents of coke and anthracite coal.The effect of their use on the sintering process will be evaluated systematically.It is expected that the structural changes of the sintering bed is considerably different between carbonaceous materials,which disappear during combustion leaving a little amount of ash components and metallic iron bearing materials,which increase the mass and volume during its oxidation. Previous studies showed that the use of metallic iron bearing materials such as steel can scrap and mill scale led to significant decreases in the production rate.This project examines the characteristics of such changes of the sintering bed structure and mineral phases and main process parameters,which govern such phenomena.Further, it searches for a new process principle to overcome the demerits and realize the significant reduction of CO_2 emissions from the iron ore sintering process.In the symposium,summary of activities and the major results and progresses of the above two research projects will be introduced.

Metallurgical Behaviour and Carbon Diffusion in Buttering Deposits Prepared With and Without Buffer Layers

Use of a buttering deposit on ferritic steel in dissimilar metal weld（DMW） joint is a common practice in nuclear plants to connect pressure vessel components（ferritic steel） to pipelines（austenitic stainless steel）.Carbon migration and metallurgical changes near fusion interface（ferritic steel–austenitic stainless steel） lead to a steeper gradient in material properties,and minimizing this gradient is the major challenge in the manufacturing of DMW joints.Inconel 82 is often deposited on ferritic steel material as buttering to reducing the gradient of physical and attaining material compatibility.Inconel 82/182 fillers are used to minimize the carbon migration,but the results are not truly adequate.In this paper,Ni–Fe alloy（chromium-free） has been used as the intermediate buffer layer in the weld buttering deposit to address the issue of carbon migration and subsequent metallurgical deterioration.The weld pads with and without buffer layers of Ni–Fe alloy have been investigated and compared in detail for metallurgical properties and carbon diffusivities.Ni–Fe buffer layer can significantly control the carbon migration which resists the metallurgical deterioration.It showed the better results in postweld heat treatment and thermally aged conditions.The buttering deposit with Ni–Fe buffer layer could be the better choice for DMW joints requirements.

Exploring a new path of green and efficient utilization of sinter return fine to produce composite pellets

Efficient utilization of sinter return fine is an important measure to reduce cost,increase efficiency,save energy and reduce emission.A new path of green and efficient utilization of return fine was proposed to produce composite pellets.The metallurgical properties of composite pellets under the condition of hydrogen-rich blast furnace were studied.The experimental results indicate that the coated concentrate was consolidated for the composite pellets through normal Fe_(2)O_(3) recrystallization.Near the surface of core return fine,the liquid phase formed due to its low-melting point,assimilated the adjacent concentrate,and then consolidated with the temperature decreasing.Compared with regular pellets,the com-pressive strength and reduction swelling index of composite pellets were decreased,but the reducibility index and softening-melting properties were improved.In addition,the reduction degradation index of composite pellets was sig-nificantly higher than that of sinter.Therefore,adding composite pellets was conducive to indirect reduction in blast furnace,reducing fuel ratio and improving production efficiency.According to the effect of the roasting system on the metallurgical properties,the roasting temperature and time were determined as 1250℃and 30 min,respectively.The composite pellets can be produced under the traditional pelletizing process.

Mechanical Properties and Microstructure Evolution of AA1100 Aluminum Sheet Processed by Accumulative Press Bonding Process

Accumulative press bonding（APB） is a novel variant of severe plastic deformation processes,which is devised to produce materials with ultra-fine grain.In the present work,the mechanical properties and microstructural evolution of AA1100 alloy,which is produced by APB technique,were investigated.The study of the microstructure of AA1100 alloy was performed by optical microscopy.The results revealed that the grain size of the samples decreased to 950 nm after six passes of APB process.The yield strength of AA1100 alloy after six passes of the process increased up to 264 MPa,which is three times higher than that of the as-cast material（89 MPa）.After six passes,microhardness values of AA1100 alloy increased from 38 to 61 HV.Furthermore,the results showed that the behavior of variations in mechanical properties is in accordance with the microstructural changes and it can be justified by using the Hall-Patch equation.Moreover,the rise in the yield strength can be attributed to the reduction in the grain size leading to the strain hardening.

Effect of Hydrogen Addition on Low Temperature Metallurgical Property of Sinter

Hydrogen-enrich iron making process is certainly to be an effective method to reduce greenhouse gases emission.However,the effect of hydrogen addition on the low temperature metallurgical property of sinter is still unclear.A detailed investigation was performed on the above topic.The results are as follows.When CO is partially replaced by H2,the RDI〈3.15（RDI〈2.8） of sinter decreases with the increase of the H2 content;when the content of H2 increases,the CO,CO2 and N2 decrease proportionally,in this case,RDI〈3.15（RDI〈2.8） of sinter increases with the increase of H2 content;the value of RDI〈3.15（RDI〈2.8） basically depends on the reduction index（Ri）.The experimental data of RDI〈2.8 based on Japanese industrial standard（JIS） are a little higher than the data of RDI〈3.15 based on Chinese industrial standard（CIS） in the same condition.In addition,for part of CO is replaced by H2：RDI〈2.8=3.38394＋1.1585 RDI〈3.15;for other gases,except H2,are decreased proportionally：RDI〈2.8=17.39678＋0.42922 RDI〈3.15

Characteristics of Calcined Magnesite and Its Application in Oxidized Pellet Production

Calcined magnesite is a binding additive and an MgO-bearing flux for pellets production. The effects of cal- cination temperature and time on the characteristics of calcined magnesite were investigated. Experimental results in dicated that the best calcination condition was 850℃ and 1h. Under this condition, the hydration activity of the eal cined magnesite was 80.56%, and the average diameter of crystal grain D, specific surface area S and the medium particle size D50 were 25.4 nm, 45.40 m2/g and 3.41μm, respectively. This kind of calcined magnesite was a good binding additive for pellets production. At the same proportion of calcined magnesite, the effects of activities of cal cined magnesite on metallurgical properties of green pellet and indurated pellet showed that calcined magnesite with high activity could improve the dropping strength and compressive strength of green pellet and enhance the burst temperature of green pellet; however, the effects of activity on compressive strength, low-temperature reduction degradation index, reduction swelling index and reduction index of indurated pellet were not obvious.

Measures of Decreasing Blast Furnace Fuel Consumption and Improving Sinter Performance in Guofeng

To further decrease the fuel consumption of blast furnace in Tangshan Guofeng Iron and Steel Co Ltd, measures of improving the quality of sinter and pellet and the performances of raw materials were put forward through phase analysis and physical and chemical performance testing. The measures of increasing the grade of sinter, decreasing the sinter reduction degradation index at low temperature, and increasing the sinter soft melt performance at elevated temperature, as well as the reasonable process parameters of sintering were described in detail.