With the increase of yield of iron concentrate and rare earth ore concentrate of Baoshan Mining Co., it is necessary to increase the processing capacity of ball mill to increase yield, while the most effective measure is to increase the fine fraction content of feedstock of ball mill so that more crushing and less grinding is achieved. In the paper, it is introduced the existing crushing and screening system of Baoshan Mining Co. is optimized through improving the distributing device of crusher, adjusting the eccentric distance of intermediate crusher as well as improving the dimension of screen hole for screen cloth of vibrating screen. As a result, the machine-hour yield of fine crusher is increased by 40.71 t/h and operation rate of crusher is reduced sharply; service time of liner plate for intermediate crusher is extended by 15 days and service time of liner plate for fine crusher is extended by 30 days; screening efficiency of vibrating screen is increased from 81.43% to 84.70% and content of feedstock with size fraction of -12 mm under it is increased from 81.43% to 94.12%; processing capacity of ball mill is increased to 380 t/h, which creates conditions for increasing the yield of iron concentrate and rare earth ore concentrate.

The blast furnace hearth is the key part that restricts blast furnace campaign to over 15 years and the key factor determining blast furnace campaign. The direct causes for temperature rise on side wall of hearth are determined to be aggravated circulation of molten iron and severe erosion of carbon brick through studying erosion mechanism of hearth aiming at the rise of side wall temperature of 5^# blast furnace hearth. The temperature at iron notch of elevation of 8.663 m for side wall of hearth is decreased and basically stabilized at 350~450 ℃ before blowing out, which is within controllable range through taking such preventing measures as setting the early warning standards, strengthening daily management, optimizing standards of depth of iron notch and strengthening maintenance as well as adjusting production and operation parameters based on three-grade early warning.

The effects of MgO on rheological property of blast furnace slag of Baotou Steel are analyzed by preparing slag specimen with pure chemical reagent under N₂ atmosphere based on the 4^# blast furnace slag of Baotou Steel under laboratory conditions and crude fuel conditions of blast furnace ironmaking production of Baotou Steel. Moreover, the effects of MgO on melting property and enthalpy of blast furnace slag of Baotou Steel are also explored. The results showed that the MgO content of slag was increased from 8.00% to 13.00%, melting temperature of blast furnace slag of Baotou Steel was on the rise, viscosity and viscous flow activation energy showed a trend of first decreasing and then increasing, fluidity and thermal stability of slag became first good and then poor under experimental conditions. In addition, the characteristic temperature of melting property for blast furnace slag of Baotou Steel shows a trend of first decreasing and then increasing as well as enthalpy of slag shows a trend of increasing with the increase of MgO content of slags, which show that the heat storage capacity of slag in blast furnace hearth is enhanced. The MgO content of blast furnace slag of Baotou Steel is suggested to be controlled at 10.00% by comprehensively considering the experimental study results, relevant theoretical calculations and control level of MgO content of existing blast furnace slag of Baotou Steel.

The optimized coal blending system for coal injection is independently developed based on considering the physicochemical characteristics, safety performance and processing property of coal injection aiming at the problems in process of optimizing coal blending for coal injection of blast furnace. The coal blending scheme with cost optimization satisfied the constraint conditions of production demands is calculated by adopting the hybrid programming technology of VB+EXCELVBA, invoking such algorithms as plan solution and multiple linear regression as well as taking ACCESS as background database. The production applications show that the system model plays an important role in reducing costs and stabilizing quality for coal injection of blast furnace.

The changes of microstructure for air quench steel slag are studied by observing the changes of various phases in air quench steel slag with time as well as calculating the numbers and area of particles for various phases with the softwares of Photoshop and Image J. The results showed that the phase types of air quench steel slag were not changed with time and diffraction peak intensity was slightly decreased. The number of particles for dicalcium silicate phase in slag is decreased significantly with time and total area of the phase is changed a little. Within 20 days,the average particle size is increased from 4.96 μm to 6.06 μm, while there are no significant changes for other phases. It can be seen that the increase of particle size for dicalcium silicate is due to its own recombination, not the change of other phases. The equation of phase change for dicalcium silicate in air quench steel slag is 1-(1-α)^1/3=0.039 T.

The effects of flow control device on flow conditions of molten steel in tundish are studied with the method of physical simulation through establishing physical model of tundish for double-strand slab caster with geometric similarity ratio of 1∶4 based on the similarity principle. The results showed that the peak time and average retention time of molten steel in tundish were increased, volume of dead zone for molten steel in tundish was reduced due to the optimized flow control device was adopted by tundish of slab. The peak time of molten steel is increased by 240.98%, average retention time of molten steel is increased by 2.37% and volume of dead zone is reduced by 7.56%. As a result, the flow conditions of molten steel in tundish are optimized as well as collision, aggregation, floatation and removal of inclusions in tundish are promoted so that the cleanliness of molten steel is ensured.

The effects of refining slag on cleanliness of liquid steel are very important. Its main functions are improving the deoxidizing capacity of deoxidizing elements, absorbing nonmetallic inclusions in steel and preventing secondary oxidation of liquid steel to generate FeO, MnO and SiO₂. In the process of refining liquid steel, the reasonable composition of refining slag plays a role of adsorbing and removing inclusions in steel. In the process of smelting rare earth steel, rare earth oxides and rare earth sulfides are formed due to rare earth is easy to react with oxygen and sulfur elements in steel as well as rare earth elements could enter refining slag because of the function of potential energy of high oxygen and sulfur for refining slag. In the production process of steelmaking, the contents of each component in ternary refining slag CaO-SiO₂-Al₂O₃ are different and the effects of rare earth on physical properties of refining slag are different because of different deoxidation systems. In the paper, such physical properties of rare earth refining slag when smelting rare earth steel as melting point, viscosity and alkalinity are analyzed by means of testing to predict the physical properties of refining slag, which could provide theoretical basis for improving the level of slag formation, cleanliness of smelting steel grade and yield of rare earth.

The 5×××series aluminum alloy belongs to Al-Mg alloy system and Mg is its main element, which is a type of wrought aluminum alloy. The 5××× series aluminum alloy is with better corrosion resistance and is often as rust-proof aluminum alloy, which is widely used in the field of off-shore building. It is also with such advantages as light weight and high strength as well as is also widely used in the fields of automobile parts manufacturing and ship structure making. In this paper,the research progress for the effects of alloying elements and heat treatment process on comprehensive properties of 5××× series aluminum alloy in recent years is summarized as well as the effects of rare earth elements on microstructure and properties of 5××× series aluminum alloy are mainly analyzed, which provide the theoretical guidance for subsequent research and development of 5××× series aluminum alloy with higher comprehensive mechanical properties.

The cracked part is analyzed with metallographic microscope and scanning electron microscope aiming at the peeling and cracking of hot rolled high strength beam steel plate during the process of bending. The results showed that many continuous punctiform or banded inclusions containing O, Al and Ti elements were distributed close to the surface layer at cracking; metallographic microstructure of decarburized layer on surface layer of steel plate was coarse equiaxed ferrite. The analysis suggests that hard inclusions, TiO₂ and Al₂O₃ destroy the continuity of product matrix and plasticity of surface layer is reduced by microstructures of oxidation and decarbonization, the matrix with inclusions fractures firstly in bending process, which makes the deformation of upper surface layer increase and it is out of tolerance range so that peeling and cracking are formed. The problem of lamellar cracking during bending for steel plate is solved by adopting the technology of pre-blowing argon in tundish to prevent oxide inclusion caused by secondary oxidation of molten steel at the initial stage of pouring.

In this paper, the production technology process and relative process parameters of new product, 27SiMn spring steel plate are introduced. The microstructure needed by product is obtained through reasonably setting cooling parameters after rolling, with which the mechanical properties of product are ensured. The using status of users shows that the performances of 27SiMn spring steel plate are good by making full use of existing equipment of Baotou Steel, adopting reasonable process parameters under the condition that both of raw materials and liquid iron meet the requirements. Its tensile strength is not less than 800 MPa and elongation is not less than 19%. Moreover, the effects of atmosphere in heating furnace on decarburized layer on the surface of medium carbon steel with silicon are important, decarburized layer on the surface of 27SiMn spring steel plate is just 24% of the requirements in the national standard GB/T 1222—2016 by reducing atmosphere and micro-positive pressure operations in heating furnace.