A three-dimensional DEM-based model was used to investigate the effect of scaffolding on the burden behavior such as the solid flow pattern and the interactive force in COREX shaft furnace. The improvement of the discharge rate on the solid flow under scaffolding conditions was also explored. The results confirm that the scaffolding occurred near the bustle pipe zone would directly affect the movement trajectory of the burden, resulting in the changes of solid flow pattern. Meanwhile, the interactive force was increased obviously compared to the normal condition. The solid flow pattern was also changed significantly when the scaffolding was generated in the guiding cone, and the particle segregation can be observed under the scaffolding. Comparing with the condition where scaffolding was generated near the bustle pipe zone, the interactive force was enhanced further. The force between the particles was decreased dramatically by increasing the speed of screw under the scaffolding, and the probability density distribution of interactive force shows a similar tendency as the normal condition. The findings of this work can provide guidance and theoretical basis for the optimized operation of COREX shaft furnace.

In order to promote sensible heat recovery of smelting slag, reduce energy consumption in iron and steel smelting process, and improve utilization rate and economy of smelting slag, by analyzing the difficulties in the treatment and utilization of the molten slag in steel mills, a dry granulation method for molten slag based on the modification and foaming treatment is proposed, and the thermal conductivity as well as granulation of slag are improved by introducing metallic iron and foaming, which provides a way to solve the problems faced by the dry granulation and slag utilization. At last, some suggestions on the future research direction of dry granulation are given.

For the iron ore variety, quality, volatility of domestic steel enterprises resulting in a decline in blast furnace burden structure stability problem, through laboratory test, the system is studied on the metallurgical properties of iron ore, the high temperature properties of the comprehensive burden structure of the sinter and different kinds of natural lump ore, the sinter and pellet collocation and different kinds of natural ore and pellets. The results show that the reduction performance and the droplet property of sinter are better than that of acid pellets and imported block ore, but the low-temperature reduction degradation phenomenon is very serious, low temperature reduction degradation index RDI_{>3.15 mm} is only 70%. Ha leather lump ore dripping temperature is too low, only about 1 353 ℃. The South Africa ore pressure difference is too large (6 820 Pa), which is not conducive to the stable and anterograde blast furnace. Due to the excellent metallurgical properties of Rio ball and samaco ball, the proportion of them can be appropriately increased in the production of the blast furnace to make up the shortage of sintering capacity and reduce the pollution to the environment. Under the condition of low sintering ratio (55%), using different pellet collocations, the burden of softening and melting interval is narrowed, the Δp_m is lowered and the comprehensive performance is obviously improved. The best composite charge structure is 55% sinter +20% Rio pellet +5% Samaco pellet +20% Hopi block ore. With the addition of the new mixed ore burden structure, the soft melting range is narrowed, the Δp_mand the S are lowered and the soft melt dripping performance is better.

In order to formulate a reasonable inclusion control process to improve the quality and magnetic properties of FeSiB amorphous ribbon, the source and the formation mechanism of inclusions were analyzed. The results show that the spherical and elliptical inclusions consisted of Al₂O₃ and SiO₂ mainly come from the industrial pure iron. During the next smelting process, ellipsoidal inclusions of 20-30 μm in the pure iron were removed by floatation, while spherical inclusions of 1-3 μm combined with the deoxidized products and form aluminum silicate inclusions and aluminum calcium silicate inclusions in FeSiB master alloy. Some of these inclusions accumulated in the inner wall of the nozzle during the spraying process, while the other parts of inclusions flowed out of the nozzle and remained in the FeSiB amorphous ribbon.

The evolution of inclusions in steel before and after the cerium treatment was studied by adding different amounts of cerium into the 304 stainless steel. And the effects of inclusion properties on corrosion resistance of 304 stainless steel were analyzed using the corrosion weight loss experiment and electrochemical experiment. MnS inclusions and composite oxide inclusions mainly existed in the stainless steel without cerium, and the average size of inclusions is 8.6 μm, while the self-corrosion potential of steel is only -348.52 mV. After the addition of cerium, the inclusions are gradually modified into spherical or elliptical inclusions, and the average size is reduced, while the corrosion resistance of stainless steel is improved. When the content of cerium reaches 0.012%, the MnS inclusions in steel are all modified into spherical inclusions containing cerium, and the corrosion potential of stainless steel is as high as -311.25 mV, which has the best corrosion resistance. As the content of cerium continues increasing, the shape of the inclusions in steel becomes irregular, and the size of inclusions also increases, resulting in a decrease in the corrosion resistance of the stainless steel.

As a pillar industry of the national economy with huge energy consumption,the green development of the iron and steel industry gradually becomes the intrinsic demand. The induction heating (IH) technique in the metallurgical field is in a cross-cutting,multidisciplinary rapid development stage,and the trend is that the heating process is becoming more precise and more controllable. The development status of precision and targeting electromagnetic induction heating in the field of iron and steel processing such as electromagnetic metallurgy,induction welding and surface heat treatment were analyzed. The intelligence and frequency conversion adaptive of the IH power supply provides a reliable basic equipment for the rapid development of IH precision technology in the future. The development trend of induction heating technology in this field was discussed. The IH precision technology in the field of iron and steel research will play a positive role in the production of fine steel. Improving the targeting and pre-control ability of the IH technology to the heating target and accurately obtaining the reasonable gradient temperature distribution are issues that will be faced and solved in the development of the thermal processing which was in the iron and steel industry.

Scientific management and control of crude steel output is important for healthy development of Chinese steel industry. It analyzes growth direction and reasons of crude steel output in detail,investigates significance of management and control of crude steel output,and focus on research about scientific regulation of crude steel output by means of differentiated management and control. China's crude steel production control should adhere to the "two kinds of thinking" of bottom line and overall situation. Under the new development condition that domestic circulation is main body and domestic and international dual circulation are promoted mutually,it is necessary to build consensus and form a joint force,strengthen the market of fair competition,formulate long-term mechanism of scientific management and control,promote combination of effective market and capable government,enhance existing advantages further and advance dynamic balance between supply and demand,in order to promote high quality development of the steel industry.

The new developing tendency of special steels in the world during the 21st century was briefly introduced with the bearing steel as the typical example. The disparity and problems between domestic and oversea production of bearing steels were analyzed. The developing status and research achievements in steel-making technologies for high-quality special-steels were emphatically introduced， including high-carbon dephosphorization for low oxygen steel in converter， refining process with lower reduction-potential in ladle-furnace， origin and control of large-size inclusions， ultra-low-Ti steel technology and the convex-roll reduction at the solidification end of large-size bloom-casting.

High strength steel is still the main material of automobiles，and has certain advantages and potentials in light weight，energy saving，emission reduction and cost for automobiles. The use ratio of high strength steel increases year by year and develops towards higher strength. Lower cost are important developing trend，the low cost production modes mainly reflected in hot rolling instead of cold rolling to produce sheet steel，and cold forming instead of hot stamping to produce ultra-high strength automobile parts，and so on. The third generation automobile steel，which relies on the metastable austenite enhancing strength and ductility，has become important development trends of advanced high strength steel. The development of advanced automobile steels bring new challenges to the material science，processing and equipment.

Abstract： From 2005， series surveys and researches of the RHF technology have been done in Baosteel， and in Zhanjiang base of Baowu Group， the first RHF production line has been constructed in 2015， which has been put into production in 2016. After a series of improvements for the production line， such as the sludge drying system， the material batching system， the briquetting process and the RHF operation technology， the RHF production line in Baosteel has reached the designing output and the standard， and it has already became a world-class RHF production line. Many harmful impurities， such as Zn， K， Na， Pb， Cl have been removed from the iron and the zinc bearing dust and sludge by the RHF process. The DRI production has been returned to the iron and steel production line， and the high temperature steam has been returned to the steam system， and the zinc powder has become the material for the zinc metallurgy process， so the iron and zinc bearing dust and sludge can be utilized well. Furthermore， the laterite nickel ore treating process has been explored in the RHF production line， and it is a good exploration for the RHF process developing.

In order to study the quantitative emission indexes of air pollutants emission of sinter flue gas（SFG），the existing problems and the development trend of the emission standard of air pollutants for SFG of the standard is analyzed. Then two kinds of calculation methods for calculating air pollutants emission of the SFG are proposed. One is the calculation method of the reference oxygen concentration， and the other is the calculation method of the sinter ore per ton. The two methods are about emission concentrations and emission intensities of air pollutants emission of the SFG. At the same time， on the basis of the second method， a method for calculating the limited production plan is proposed， which can be used to calculate the proportion of the production reduction accurately for each sintering machine in the limited region during the special period without using the one-size-fits-all approach. The application of this method will help enterprises to improve their own clean production level. Enterprises with high levels of clean production will be fewer limited in production， while those with low levels of clean production will be more limited in production.

In recent ten years，the automobile industry in China has a rapid development，and the related upstream and downstream industries are well developed. In a series of key words such as “Forward Design”，“Lightweight”， “Intelligent” and “New Energy”，"EVI" also goes into people’s horizons and is gradually accepted. EVI is the abbreviation of ‘Early Vendor Involvement’. Baosteel has already established a specific work pattern of ‘532’ for automotive products through exploration and practice for many years. ‘5’indicates five different technical support phases including advanced engineering design， vehicle body design， tooling design， production preparation and cost optimization. ‘3’ means three different collaboration levels which are BIW， part and VA/VE. In addition， ‘2’ stands for two types of solutions， i.e. cost- and lightweighting- oriented objectives. Based on analysis of customers’ requirements and creative EVI solutions， Baosteel not only meets the requirements and creates value for customers， but also carries out a closed loop from technical development to efficient operation that provides guarantee for independent innovation.

The removal mechanisms for main pollutants in sintering flue gas，process flow for flue gas purification and systematical equipment of the sintering flue gas purifying systems by activated coke were introduced in detail，which is the first self-designing and manufacturing purifying system of its kind in China. The major facilities including flue system，adsorption system，desorption system，activated coke storage and transportation system were systematically and completely illustrated. The inner structure，working principle and relevant designing and operating parameters of some major equipment were concisely presented. The technological characteristics of this purifying system were summarized through analyzing and the actual treatment effect was presented，which had the advantages of high reduction rate of pollutants and steady and reliable operating performance. SO2 content ranges from 412.091 to 642.811 mg/m3 before being purified，while its content is decreased between 1.227 and 7.999 mg/m3 after treatment，with a high removal rate from 98.53% to 99.76% on the basis of daily averages. [NOx]content ranges from 235.451 to 365.218 mg/m3 before being purified，while its content is decreased between 92.707 and 137.663 mg/m3 after treatment，with a removal rate from 57.63% to 69.44%. The toxic equivalent quantity of dioxin ranges from 0.82 to 5.40 ngTEQ/m3 before being purified，while its TEQ is decreased between 0.002 3 and 0.008 9 ngTEQ/m3 after treatment，with a high removal rate from 99.43% to 99.89%. The dust content after treatment is decreased between 7.747 and 11.500 mg/m3. An evaluating conclusion on this purifying system was drawn based on the actual treatment effect and practical run performance. Meanwhile，the application prospect of this new purifying system was predicted.

At the height of high-quality development，the high-quality development of iron and steel is defined in terms of the supply system，demand，layout，circular economy and comprehensive benefits. The fundamentals for the high-quality development of the iron and steel industry and the deep-level problems existed in the high-quality development process of the steel industry，i.e.，the product quality，the green development，the technical equipment，the smart manufacturing，the service awareness，the industrial order and the internationalization were analyzed. Meanwhile， the supply-side reform and laid a solid foundation for the development of the iron and steel industry in China was also discussed. Combining the practice of the high-quality development of the outstanding iron and steel industry，it is pointed out that the iron and steel industry should improve its competitiveness through the technological advancement，product upgrading，technological innovation， low-carbon development and standard leadership to achieve the high-quality development.

Based on the characteristics of mold heat transfer，a three-dimensional transient heat transfer model of billet continuous casting mold is established. Casting process of the billet is simulated by a node temperature transfer method. The ANSYS finite element software is used to analyze the model. The three-dimensional steady-state temperature field of the billet mold is obtained by sufficient iteration and compared with the traditional two-dimensional model. The influence of scale on mold temperature distribution has been analyzed through the continuous change of the scale loading technique of dynamic boundary conditions. The result is detailed as follows. The analyzed result obtained by three-dimensional heat transfer model in the top zone of the mold is basically coincident with copper wall temperature distribution rule. The copper wall temperature reached its peak at 50 mm near the meniscus. The highest temperature of copper wall would be increased from 187 to 318 ℃ when meniscus scale thickness added from 0.1 to 0.5 mm. In this case，high temperature region of copper wall would be expanded so that copper wall deformation degree could be increased.

The research status of 40CrNiMo at home and abroad was reviewed in detail from five aspects of conventional heat treatment andproperties，deformation heat treatment，surface heat treatment，precipitation and alloying optimization，and other aspects. The research and application of new technology（surface chemical heat treatment，surface laser quenching，chrome plating shot peening，alloy optimization and precipitation phase）on the production of 40CrNiMo steel and the research of heat treatment（subcritical quenching，cryogenic treatment） on its performance mining were mainly reviewed. In addition，the influence of turning parameters on fatigue strength and surface roughness of 40CrNiMo steel and its fracture characteristics under stress corrosion condition were briefly summarized. The short comings of current research of 40CrNiMo steel and its potential future directions were pointed out.

Numerical simulation combining the finite element method and the finite volume method was employed to study the multi-fields in bloom mold with cross-sectional dimension of 240 mm×240 mm. Firstly， the parameters of submergence depth of the submerged entry nozzle （SEN） and casting speed were optimized by calculating the flow and solidification of molten steel. Secondly， the coupling calculations of magnetic?field and the optimized flow field were performed to optimize the parameters of electromagnetic stirring， such as current intensity and frequency. The simulated magnetic field was in good agreement with the measured data. The results show that the optimized SEN-depth is 100 mm and casting speed is 0.7 m/min. With the electromagnetic stirring， the tangential velocity increases from 0.042 to 0.300 m/s under the condition of casting speed 0.7 m/min and SEN-depth 100 mm， when the current intensity increases from 100 to 400 A. The frequency has little effect on fluid flow. Hence， the optimal flow field can be obtained with 100 mm of SEN-depth， 0.7 m/min of casting speed and 400 A/2 Hz of current.

Steel Enterprise Innovation Infrastructure (SEII) is an infrastructure system for upgrading, integrating, and innovating the steel industry, driven by technological innovation and managed with industrial network, based on the development concept of innovation, coordination, green, openness, and sharing. SEII is aimed at high-quality development and aims to improve the core competitiveness of steel enterprises. The basic framework of SEII was put forward, it is a digital innovation platform serving steel enterprises based on the Industrial Internet. The underlying level LPPL(Lab-Pilot-Production Line) is in charge of providing sensors collected data to the system and accurate execution of operation orders from the edge. The digital twin, that is process set-up model in the edge, and the bottom LPPL consist of a CPS, which is the core of SEII. The digital driven cloud platform is in charge of the operation management and serves of the system. It is analyzed that the characteristic functions of SEII′s include greening(GX), digitization(DX), high quality(MID), and strong chain(SC), namely the key process equipment innovation function for greening, the super intelligent CPS process control function, the high-efficiency and low-cost products innovation function, and the coordinated management and optimization operation function of the entire industry chain. It is pointed out that giving full play to the advantages of China′s socialist national system, developing SEII, and establishing a national, local, and enterprise SEII multi-level management system are of great significance for GX-DX-MID-CS of the steel industry, and promoting its high-quality development.The construction of SEII began. The practical results of construction of SEII indicate that the deep integration of the steel industry real economy and digital science/technology can leverage the enormous advantages of data resources and data technology application scenarios in the steel industry. The double-layer architecture of data driving, software definition, data perception/data processing will give full play to the effect of amplification, multiplication and superposition of digital technology, greatly accelerate the digital transformation of the steel industry, and reduce the cost of digital transformation of the steel industry. The significant progress made in the construction of SEII at present fully demonstrates that with the support of SEII, the core competitiveness of the steel industry has significantly increased, showcasing a bright prospect for the future innovation advance, coordinated sharing, and high-quality development of the steel industry.

Ultra high strength（UHS） stainless steels have been widely demanded because of high strength，good toughness and excellent corrosion resistant. Precipitation hardening plays an important role in possessing high strength of the steels，but the complex precipitation process and unclear mechanism are the key factors to limit the exploitation of new UHS stainless steels. The classifications，marks，compositions and mechanical properties of UHS stainless steels were introduced. The evolution of precipitations and reinforcement mechanism research of martensitic UHS stainless steels were summarized. The significant directions of development of UHS stainless steels as computational materials science，strengthening theory and resource saving technology were pointed out.

Rational gas distribution is the primary factor for blast furnace to maintain the stable production with high efficiency and low consumption. The gas distribution is affected not only by the qualities of burden and operating rules，but the inner profile of blast furnace. As the innate factor，the rational inner profile design is the basis of acquiring the ideal gas distribution. Depending on the theories of heat transfer and hydromechanics，mathematics models of heat transfer and gas flow in blast furnace were established，and the critical parameters were obtained through experiments. Subsequently，the effect of bosh angle，shaft angle and equivalent bosh angle on the gas distribution were studied through numerical simulation method. The result indicates that decreasing bosh angle and increasing shaft angle are in favor of suppressing the edge flow. And adjusting the equivalent bosh angle can achieve the same destination as well，but which plays a role with higher intensity and wide range compared to the bosh angle adjustment，also with a different maximal affecting position to gas flow.

By investigating the material metabolism between industrial system and the environment，the air was regarded as a resource for metallurgy，and the relationship among air consumption，waste gas production，polluted materials emission and the ambient air quality was established. Based on the survey of steel plants，the air consumptions and waste gas emissions of BF-BOF route，including sintering，coking，iron-making，steel-making and steel rolling，were obtained and compared with EAF route. The shares of materials consumption and waste gas emission of Chinese steel industry were calculated on a ton-of-steel basis. It is shown that air consumption contributes more than 85% of the mass of materials consumption. Thus，it is reducing the air consumption and waste gas emission that is of great significance to the reduction of polluted materials and improvement of air quality. The emission-reducing scenarios，such as oxygen-enriched or pure oxygen combustion，waste gas recycle and reuse，and vertical-type sintering ore waste heat recovery were investigated. It is pointed out that these operative technologies，as well as optimizing steel manufacturing process and developing EAF-route，are effective to reduce air consumption and the resulted reduction of particulate matters，SO2 and NOx emissions.

The oolitic hematite ore was recognized as one of the most difficult iron ores to use because of its unique oolitic structure， fine iron particle size， and high phosphorus content. The reduction of high phosphorus oolitic hematite played an important role in subsequent magnetic separation， especially the accumulation and growth of iron. The influence of borax on the reduction of high phosphorus oolitic hematite was studied. It indicates that the weight loss rate is up to 31.11% and the metallization rate is up to 90.10% when the temperature is 1 000 ℃ and the borax percentage is 6%. XRD and SEM analyses show that borax could decrease the melting point of the reactant.On the other hand，the diffraction peaks of fayalite （Fe2SiO4）， ferrospinel （FeAl2O4） and kyanite （Al2SiO5）disappear， and then the ones of anorthite （CaAl2Si2O8） ， sodium aluminum borate（Na2Al2B2O7） and sodium borate （Na2B6O10） with low melting points appear. In the end， the amount and particle size of iron in the reduced samples increase with the addition of borax increasing.It indicates that the effect of reduction is strengthened.

On September 22,2020,China announced at the 75th United Nations General Assembly that it aims to peak its carbon dioxide emissions before 2030 and achieve carbon neutrality before 2060. The deep decarbonization of the steel industry is a necessary step to achieve these goals,as well as an important strategic measure for addressing climate change,alleviating energy crises,and promoting green and healthy development. Green and low-carbon development is the key to the transformation,upgrading,and high-quality development of the steel industry,as well as an important support for China′s carbon peak and carbon neutrality goals. An analysis was conducted on the current carbon emissions of China′s steel industry,followed by a comparison of the carbon neutrality goals and implementation paths of major steel-producing countries. Using dynamic material flow analysis methods,a steel demand model and a scrap recycling model were constructed,and China′s steel demand and scrap resources were predicted until 2060. The results indicated that China′s steel demand will decrease to 878 million tons and 543 million tons in 2030 and 2060,respectively. Domestic scrap production will be approximately 420 million tons in 2030,gradually decreasing after 2055 but remaining above 400 million tons. Based on the dynamic material flow analysis results and scenario analysis methods,a carbon emissions model for the steel industry was constructed,potential for energy conservation and emission reduction in the steel industry were analyzed,and a timetable and roadmap were formulated for China′s steel industry to achieve carbon peak and carbon neutrality based on the carbon neutrality path analysis model of the steel industry,pointing out that the Chinese steel industry will experience four stages before achieving carbon neutrality: fluctuations and control of crude steel production-carbon control,reduction of crude steel production-emission reduction,period of crude steel production at a low level plateau-low carbon,and stabilization of crude steel production at a low level-carbon neutrality,providing important guidance and action plans for China′s steel industry to achieve carbon peak and carbon neutrality goals.

Through deploying the big data acquisition platform and using the efficient distributed information transmission technology，the collection and summary for the massive data of sintering production were completed，and data warehouse of the whole production line was established. By combining the process knowledge and data mining technology，the underlying rules of the parameters of raw material property，ore blending theory，process parameters，production quality index and production cost were extracted. Based on the mathematical statistics and machine learning algorithm as the core，the quality intelligent control model based on the big data technology for the whole production line of sintering was further researched. Using the methods of decision tree and the optimization，a perfect decision system was established. Based on the algorithm of gradient boosting decision tree，the prediction model of sintering burn through point was established，and the prediction rate of the model is more than 99%. Compared with the prediction model established in the past，the prediction accuracy and stability of the model were further improved. The research results will promote the development of innovation，automation and intellectualization for the sintering production，stabilize the quality index，reduce the production cost，and have wide application value.

CO,one of the six standard air pollutants,is toxic to human body and the environment. The steel industry releases large amounts of industrial tail gas containing CO into the atmosphere every year. Under the background of "carbon peaking" and "carbon neutral",the whole steel industry is facing huge CO emission reduction pressure. The present situation of CO emission from flue gas in typical steel production process was summarized. Continuous emissions included coke oven flue gas,sintering flue gas and rotary kiln flue gas,etc. The CO concentration in these flue gases was low and the flue gas emissions were large. For CO reduction in flue gas,the research works on source control,process reduction and terminal treatment technologies were summarized. Source control refers to replacing fossil energy with environmentally friendly hydrogen and electrical energy. Process reduction focuses on improving fossil fuel combustion conditions to reduce CO emissions. Terminal treatment involves physically/chemically separating CO from the flue gas or oxidizing it to CO₂. Among the terminal treatment technologies,catalytic oxidation technology has low investment cost,no operational energy consumption and secondary pollution,and significant emission reduction effect. In addition,it can be combined with flue gas desulfurization and denitrification technology and has the possibility of industrial practice,but the current catalysts need to be optimized in terms of anti-poisoning and preparation cost. Finally,according to the CO emission reduction of sintering flue gas is an urgent problem to be solved,the feasible technical routes and challenges for CO emission reduction of sintering flue gas were analyzed. It is suggested that low input and high efficiency CO emission reduction can be achieved by coupling flue gas cycle,medium spraying,fuel improvement and catalytic oxidation technology.

Background of carbon emission and control measures taken by European Union countries in the situation of global climate warming are summarized. Main measures and achievements for controlling carbon emissions of China are also introduced. Research and development in carbon emission control of steel industry，and corresponding cutting-edge technologies in EU，US，South Korea and Japan are presented intensively. Furthermore，BAT technology for energy saving and emission reduction，green process，green manufacturing products，green logistics and new technology are also introduced. A reference for the carbon emission reduction of China steel industry is provided，aiming to draw the attention of steel enterprises to carbon emissions.

The iron and steel industry is a typical resource- and energy-intensive industry and one of key industries for the energy conservation and emission reduction. The progress and problems in the energy conservation and emission reduction achieved by China's iron and steel industries since the 12th Five-Year Plan were summarized. Based on the dynamic material flow analysis method， the steel demand forecast and the scrap recovery model were constructed. Based on the evaluation of 35 energy saving and emission reduction technologies， combined with the energy consumption and CO2 emission models， the energy saving potential of the China's iron and steel industry by 2050 and the impact of various factors were analyzed. Finally， several ways to improve the energy efficiency were proposed which provides the theoretical guidance for the green and low-carbon transformation and sustainable development of the China's iron and steel industry.

The problem of easy cracking and deformation of high manganese steel wear liner was studied by analysis of composition and properties. The hardness，wear resistance，impact resistance and service life of high manganese steel wear liner were greatly improved by added a certain amount of alloy additives and improve the heat treatment. Finally the hardness，abrasion resistance，tensile strength and yield strength of high manganese steel were improved 10.7%，62.7%，7.4% and 8.13% respectively.

In order to improve technical and economic indexes of blast furnace， the metallurgical properties of low [w(MgO)] slag were studied and evaluated systematically by laboratorial and industrial test in Ansteel. The results show that under the low Al2O3 load in blast furnace， the[w(MgO)]in slag is 4%-7%，and the melting temperature of all the slag is less than 1 350 ℃. When the temperature of slag is 1 500 ℃， the viscosity of the slag can satisfy the need of blast furnace in theory with[w(MgO)]over 3%. The best basicity of slag is about 1.245. Under the production condition in industry， the[w(MgO)]of slag is controlled in 4.5%-5.0%， and the viscosity of slag is about 0.16-0.20 Pa·s. The desulfurization capacity of the slag may not fall down when[w(MgO)]in slag decreases by optimizing basicity of slag. The production cost from BF operation decreases obviously and 17 kg/t（Fe） of the slag ratio is almost reduced by adopting new technology. So， it helps to implement green sustainable development.

In the production process of iron and steel enterprises，a large amount of dust and sludge with iron element as the main component is produced. Iron and steel dust sludge is an important part of solid waste in iron and steel industry. It contains valuable elements such as iron，carbon，zinc，potassium，sodium and so on. If it is stacked or discharged directly，it will inevitably cause environmental pollution. And the valuable elements in the Iron and steel dust sludge are not used effectively. Iron and steel enterprises should choose appropriate methods and equipment based on understanding the composition characteristics of different types of dust sludge，defining the final purpose and effect of the recycling and utilization of dust sludge. The utilization technology and method of iron and steel dust sludge are analyzed，and the main direction of dust sludge treatment in the future is put forward，which is the combination of fire and wet process.

The longitudinal particle size segregation of the sinter bed is an important factor affecting the sinter quality， and the nine-roller plays a crucial role in the distribution of the material layer on the sintering pallet. Based on the actual size of the sintering nine-roller in a steel enterprise， a three-dimensional model was established， and the distributing process under different conditions was simulated by EDEM soft ware. The results showed that when the nine roller speed increased from 4 to 40 r/min， the thickness of the material layer had no obvious change， and the accumulation angle of particles decreased from about 55° to about 49°， and the longitudinal segregation degree of the material layer increased first and then decreased. When the rotational speed of the nine-roller was 30 r/min， the longitudinal size segregation degree was the highest. When the angle of the nine roller arrangement increased from 33° to 43°， the height of the material layer decreased gradually， and the longitudinal size segregation increased first and then decreased. When the tilt angle of the nine-roller was 38°， the segregation degree was the highest.

Sintering is one of the main processes in blast furnace ironmaking process. The application of big data intelligent technology is expected to solve the traditional problems such as complex variety of raw materials, distortion of ore blending constraints, difficulty in optimizing ore blending model, low accuracy of sintering process prediction model, weak adaptability of production and difficulty in characterization of sintering state and quality. At present, some iron and steel enterprises have established iron-making data platform including sintering process data to realize the collection, storage and preliminary processing of sintering process data. The constraint setting of the existing ore blending model is more consistent with the field conditions, and the optimization speed and accuracy of the ore blending model are accelerated by data analysis and intelligent algorithm. The intelligent prediction models of key parameters of sintering state and sinter quality constructed by different methods have good prediction effect on the test set. The comprehensive evaluation and optimization of sintering process have also been explored and some achievements have been made. Based on the existing research progress, the research and application directions of intelligent sintering technology are prospected, such as data management of the whole sintering chain, intelligent ore blending of mechanism and data fusion, self-updating prediction of key parameters of sintering, construction and optimization of adaptive comprehensive evaluation system of sintering based on data and experience. It is necessary to carry out modular governance for the problems in sintering data, eliminate the time delay between parameters and build a dynamic association rule base for parameters. The intelligent ore blending model of sintering is further developed, which is deep fusion of mechanism data and experience to the conditions of production line, and the deep optimization of sintering intelligent ore blending is carried out which combined with the effect of blast furnace. According to the characteristics of production line data and the needs of field operators, the target parameters of sintering process prediction will be selected comprehensively, and the self-updating prediction model of sintering process parameters will be established according to the data frequency of target parameters, the actual sintering production smelting cycle and the needs of operators. The characterization parameters and operation parameters of sintering process were selected based on the data information of sintering production process and expert experience, and a comprehensive adaptive evaluation system of sintering state quality was established based on the integration of data and experience. The operation parameters of sintering will be adjusted based on the demand of blast furnace for the sintering process and the prediction of sintering process parameters. Finally realize the digital transformation and intelligent upgrading of sintering production.

Taking the six-high five-stand cold tandem mill of 2 230 mm as research object，the three-dimensional nonlinear mill simulation model with intermediate roll using ESS profile wase stablished through the ABAQUS finite element software platform. By numerical simulation，the variation law of the shape regulation region was analyzed under the combined action of shape control means including work roll bending， intermediate roll bending and intermediate roll transverse movement. Meanwhile， the control performance of different parameters including work roll bending force，intermediate roll bending force and intermediate roll transverse movement value to quadratic crown and quartic crown of the strip was researched systematically. The application results show that the mill with ESS profile has a good control effect on the shape and transverse thickness of the strip.

In order to get a lower fuel ratio and BF smooth operation after the use of high performance coke， the relationship between the high temperature performance of coke and coke burden was studied. The high temperature performance of coke has an important influence on BF coke burden. Since the medium-capital overhaul of Shouqin No.1 BF， several suitable blast parameters have been chosen according to the blast system and operation profile with high-quality CDQ. Through the strengthen management of raw materials and BF tapping， and reasonable regulation of the upper and lower gas distribution， the operation of high coke burden was achieved under the condition of economic burden. Under the pressure of limiting production， the tuyere area was reduced by 11.38% . Meanwhile， reasonable blast parameters were adopted to lengthen the raceway depth and maintain the stability of the hearth. Moreover， the narrow and strong central gas distribution with a stable edge temperature formed. Production practice shows that under the condition of an average slag ratio up to 433.30 kg/t， the coke burden is improved to 6.01 t·t－1 with the average fuel ratio 499.17 kg/t. It is proved that the fuel consumption could be reduced effectively by the use of high-quality coke.

To research potential of applying local dew point technology on Al-bearing high strength steel，effects of dew points during heating on selective oxidation behavior of a C-Mn-Si-Al steel were studied through a hot-dip process simulator （HDPS）. The dew points during heating were set as －10，－20 and －50 ℃，respectively，while the dew point during soaking was －50 ℃. External surface of as-annealed steel samples was characterized by SEM/EDS. Alloying element profiles were detected by GDOES. Kinds of compound on the external surface were identified by XPS. As heating with the dew point of －10 ℃，little oxides could be found on the external surface and remarkable internal oxidation of Al could be found. As the dew point during heating decreased to －50 ℃，much more oxides composed with manganese and aluminum were observed on the external surface. Therefore，high dew point during heating extremely suppress enrichment of alloying elements and formation of oxides on the external surface for the C-Mn-Si-Al steel.

In order to reduce the rate of flaw detection disqualification in 45 round steel with diameters from[?200 mm]to[?250 mm]which was rolled in 360 mm×450 mm bloom. The main causes of flaw detection disqualification were center segregation and porosity of blooms. The casting speed，secondary cooling water and electromagnetic stirring at end of solidification were contrast tested. The roller of heavy reduction was optimized. Microscopy，scanning spectrometer and true density of the blooms were analyzed. The results show that the 0.45 m/min casting speed and low secondary cooling water with 300A and 2.4 Hz parameters of electromagnetic stirring were benefit to the equiaxed grains expanding. The biggest area of equiaxed grains was 280 mm×170 mm.The true density and compactness of bloom with convex roller were 8.022 6 g/cm3 and 0.998 4 respectively which was higher than that in flat roller. After comprehensive technology application，the qualification rate of flaw detection was improved form from 70.85% to 95.87% in 2 583 tons 45 round steel production.

The change of basicity of sinter will have some influence on its yield， quality， metallurgical property and economic and technical index of blast furnace. The relationship between the basicity of sinter and sinter yield， yield of the blast furnace as well as coke ratio effect was compared， and the influence of sinter basicity change on the sinter yield， utilization coefficient and metallurgical properties of correspondence was tested. When the basicity of sinter with high silicon in Jiuquan Steel is within 1.6-1.9 ， the metallurgical properties and various indexes are better. The utilization coefficient increases with the increase of basicity. Within the basicity interval and reducing the sinter basicity， the sinter and blast furnace grade can be improved， and the cost of pig iron can be reduced.

Serious pollution to the environment is caused by the increasing city combustible solid waste，and how to effectively deal with them has become a major problem. The chemical composition，the calorific value，the combustion characteristics and research status of city combustible solid waste were discussed. The city combustible solid waste mixed injection was put forward based on the physicochemical properties and processing properties of city combustible solid waste，which could bring new fuel for the blast furnace， dispose many kinds of city combustible solid waste，complete the solid waste disposal on the surrounding society，and expand the social function of steel plant in the city.

The process of iron and steel production produces a large amount of dust， containing a lot of carbon， iron， zinc， lead， potassium， sodium and other valuable elements， which would not only cause environmental pollution， but also would lead to a waste of resources if appropriate treatment method is not taken. The comprehensive and efficient treatment technology of dust is focused. The process parameter characteristics of steel enterprises in the whole process were classified firstly and on this basis， several typical dust treatment processes were compared and analyzed. Finally， the dust treatment technology in the future was forecasted combined with the actual situation of China and a new dust treatment process was put forward to realize the efficient utilization of secondary dust in iron and steel enterprises.