The exploration for effects of rare earth (RE) on phase transformation of Fe-based alloy is significant in the development process of advanced high strength steel containing RE. In the paper, the effects of La and Ce on martensite phase transformation of steel are studied from such two aspects as driving force and minimum energy path (MEP) using first principles calculations. The calculations of formation energy revealed that the stability of fcc-Fe was increased and stability of bcc-Fe was decreased through substitution of RE for part of Fe atom so that the driving force of martensite phase transformation was decreased. Meanwhile, the analysis on generalized solid-state nudged elastic band method indicated that there would be an additional energy barrier when phase transformation went on to the FM state with ratio c/a of 1.14 along Bain transformation path in the system containing RE, which was related to the sudden decrease of magnetic moment caused by the hybridization between atomic orbital of RE and nearby atomic orbital of Fe.

In the paper, it is elaborated the inherent difficulties and advantages for comprehensive utilizations of resources in Bayan Obo ore deposit, proposed several problems noteworthy of better comprehensive utilizations, pointed out the most likely minerals to be utilized next as well as emphasized that comprehensive utilizations of nonmetallic minerals in the deposit should not be ignored. The complex deposits provide abundant mineral resources for people and cause many difficulties of recycle. In order to do comprehensive utilization of resources well, it is necessary to investigate thoroughly inherent characteristics of the ore as well as have corresponding assessment and motivation mechanism so that the comprehensive utilizations could be put into practice indeed and mineral resources could be used as far as possible.

The iron and steel industry is the pillar industry in national economic development as well as its energy conservation and carbon reduction are the priority among priorities to achieve the national development goal of “carbon dioxide emission and carbon neutrality”. In this paper, it is briefly introduced the types and characteristics of main low carbon ironmaking technologies with hydrogen metallurgy as well as expounded its progress and current situations at home and abroad. The hydrogen rich reduction technology with blast furnace and hydrogen-based direct reduction technology with shaft furnace are the main technologies of low carbon ironmaking technologies with hydrogen metallurgy. Among them, the ability of carbon reduction for hydrogen rich reduction technology with blast furnace is limited, so it can be as short-term development direction of low carbon ironmaking technologies with hydrogen metallurgy for iron and steel industry. If combine with the carbon capture, utilization and storage (CCUS) technology, CO₂ emissions could be further decreased. The hydrogen-based direct reduction technology with shaft furnace is without fossil energy in production process and carbon emissions could be reduced by over 80% compared with traditional production process of “blast furnace-converter”, which is inevitable development trend of technological reform in the iron and steel industry. In order to actively respond to the national green and low carbon development strategy and five major political tasks of Inner Mongolia, Baotou Steel actively implements the green low carbon ironmaking technologies with hydrogen including hydrogen-based mineral phase transformation of medium lean ore in Bayan Obo, hydrogen rich reduction with blast furnace and hydrogen-based direct reduction with shaft furnace so that the low carbon green production process of iron and steel is significantly improved.

The effect laws of coiling temperature on microstructure and texture of 50W470 non-oriented silicon steel under hot rolling and normalizing processes are studied with such detection and analysis technologies as the optical microscope (OM) and electron back-scattered diffraction (EBSD). The results showed that high temperature coiling could promote the transformation of deformed microstructure in central layer of hot rolled plate to equiaxed grain without distortion. The promoting effect of coiling at 740 ℃ is better than that of coiling at 600 ℃. After high temperature coiling, the proportion of favorable texture {100}+{110} is increased, while the proportion of unfavorable texture{111} is decreased. After normalizing, the microstructure of high temperature coiling plate is with perfect recrystallization and the deformed microstructure is disappeared as well as the coiling plate with temperature of 740 ℃ is with more favorable texture {100}+{110} and fewer unfavorable texture{111} than those of coiling plate with temperature of 600 ℃.

In this paper, the effects of rare earth element Ce on DWTT properties of pipeline steel are studied in laboratory by taking X80 pipeline steel as the research object. The study results showed that the addition of rare earth element Ce could help to improve the low temperature toughness of test steel. The impact energy of sample after adding rare earth element Ce could reach 210 J at -40 ℃, which is increased by 19.3% compared with that of sample without adding rare earth. The addition of rare earth element Ce could help to reduce the ductile-brittle transition temperature of pipeline steel. The impact energy of heat affected zone after welding for sample without adding rare earth element is 189 J and the impact energy of heat affected zone for sample after adding rare earth element Ce could reach 216 J, which is increased by 14.3%.

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 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.

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 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.

In the denitrification process, flue gas needs to be heated due to the temperature requirements of denitration reaction are high, more blast furnace gas is consumed so that a large amount of CO₂ is generated. In order to achieve the energy conservation and carbon reduction, energy saving type built-in direct fired furnace is used instead of traditional heating furnace. The flue gas is heated with the heat released by igniting the CO in flue gas with energy saving type built-in direct fired furnace so that the consumption of blast furnace gas and carbon emission are reduced as well as temperature requirements of denitrification could be met. The consumption of blast furnace gas is reduced by 17.9% with energy saving type built-in direct fired furnace, annual CO₂ emission reduction of over 35 000 t is achieved and annual cost saving could reach over RMB 4 million yuan through applications and comparisons, which could meet the requirements of energy conservation and carbon reduction for steel enterprises on the premise of meeting requirements of denitrification reactions.