With the increasing demand of high quality carburizing steel for key spare parts as well as proposal of “carbon peaking and carbon neutrality goals”, the requirements for such comprehensive properties of carburizing gear steel as wear resistance and strength and toughness are higher. It is the development direction of carburizing gear steel to develop high efficiency, energy saving, low carbon and economic high temperature carburizing technology with rare earth microalloying. In the paper, it is discussed the key problems and regulation of microstructure and properties for applications of rare earth in high temperature carburizing gear steel as well as summarized the applications and development trend of high temperature carburizing for gear steel with rare earth microalloying through introducing the applications and development situations of high temperature carburizing gear steel at home and abroad, which are of great significances for developing high temperature carburizing gear steel with rare earth characteristics.

In order to improve the corrosion resistance of HRB400E steel, test steel is rolled by adding lanthanum-cerium mischmetal into it in refining process and controlling rolling-start-temperature. The inclusions and microstructure are characterized with scanning electron microscope, energy dispersive spectrometer and optical metallographic microscope as well as the effects of rare earth and rolling-start-temperature on corrosion resistance of test steel are analyzed combining with neutral salt spray test. The results showed that the Mn-Si-O inclusions were completely transformed into (Ce, La)₂O₃ and (Ce, La)₂O₂S after treatment with lanthanum-cerium mischmetal as well as part of Mn and S were nucleated around them to form complex inclusions of rare earth, but a small amount of individual MnS inclusion was still precipitated. Under the experimental conditions, the corrosion resistance of 2^# test steel is optimal when rolling-start-temperature is 900 ℃, content of mischmetal is 0.011 6% and corrosion rate is 1.577 g/(m²·h).

As the important steel of basic building components, screw-thread steel is widely used in such engineering constructions as buildings, bridges and roads. Its proportion of carbon emission is higher in building materials due to its large consumption so that the management and evaluation research of carbon footprint in its manufacturing process are particularly important. In this article, the key direction for its carbon reduction is found out through analyzing operation and conversion of carbon flow in its production process. The data of carbon emission and carbon footprint of products is qua.pngied as well as all of potential influencing factors are calculated with the LCA method so as to ide.pngy and control key areas of carbon emission, which could provide guidance for Baotou Steel to establish measures and plans of carbon reduction as well as environmental product declarations(EPD) of screw-thread steel products are successfully released on the EPD platform.

In the paper, it is introduced current treatment processes and utilization ways of coking high salinity wastewater as well as analyzed the restraining factors and solutions for technologies of salt separation and crystallization in treatment of coking wastewater. The treatment scheme of deep oxidation, salt separation and crystallization for coking high salinity wastewater is adopted by a coke making enterprise based on the existing biochemical treatment, deep treatment and membrane concentration treatment to further remove such pollutants as organic matters, ammonia nitrogen and fluoride in coking high salinity wastewater so that wastewater recycling is realized. Moreover, the recycling and zero discharge of coking wastewater are realized through producing such two high quality by products of crystal salt as sodium chloride and sodium sulfate by evaporation crystallization.

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.

In the paper, the technical progress of ironmaking system of Baotou Steel is summarized and analyzed. It is thought that the technological breakthrough and innovation of beneficiation, sintering and smelting problems for special iron ore of Bayan Obo are fundamental guarantee for achieving the ironmaking production with high efficiency and quality, low consumption, long service life and environmental protection as well as technical support of great-leap-forward development for ironmaking of Baotou Steel.

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 inheritance mechanism of rare earth element lanthanum in baiyuneboite during process of blast furnace ironmaking is studied by taking rare earth lanthanum as the object. The microscopic behaviors of lanthanum from slags to iron during process of blast furnace ironmaking are analyzed by thermodynamic calculations and experimental characterization. The results indicated that La₂O₃ in blast furnace slags could be reduced to LaC₂ during process of blast furnace ironmaking, and then LaC₂ is dissolved in molten iron and La is adsorbed by the oxygen functional groups on porous graphite so that the rare earth could be inherited to subsequent steelmaking processes, which makes up for the problem in traditional view that the rare earth oxides in blast furnace slags are difficult to be reduced during process of blast furnace ironmaking and cannot be inherited to subsequent processes.

The baiyuneboite is the largest paragenic ore of rare earth resource reserve in the world. It is the key of effectively utilizing rare earth resources to figure out the inheritance rules of rare earth in steel as well as clearly understand roles and mechanisms of rare earth in steel. In the paper, it is summarized the years of research achievements of authors’ team as well as inheritance of rare earth of baiyuneboite in steel, effects of rare earth on metallurgical quality of steel and microalloying of rare earth in steel. The related fundamental research work can enrich the understanding of roles of rare earth in steel as well as provide theoretical and technical supports for high-quality and efficient utilizations of rare earth resources of baiyuneboite in steel.

The applications of elements are out of balance in the rare earth industry in our country as well as abundant lanthanum and cerium are surplus so that the applications of rare earth in steel are gradually heeded. In the paper, the research progress on treating steel with rare earth lanthanum and cerium at home and abroad in recent years are overviewed, which includes the effects of rare earth on purifying liquid steel, modifying inclusions and microalloying as well as design of deoxidation test for rare earth proves the feasibility of rare earth as deoxidizer of liquid steel. Moreover, the performances of rare earth in strengthening properties of steel as well as superiorities of purifying liquid steel with rare earth and alkali metal and microalloying of rare earth under low oxygen condition are introduced. The efficient utilizations of rare earth in steel are expected based on summarizing the on-going results.