In the process of developing high quality steel, rare earth elements are widely used and effects are significant. In this paper, the mechanisms of action and lack of research of rare earth elements in steel are summarized as well as application situations of rare earth elements in wear-resistant steel, H beam and corrosion-resistant steel are overviewed. The design thinking of determining additive amount of rare earth by scie.pngically applying the first principle of density functional theory and combining mismatch theory with thermodynamic calculations is proposed aiming at such problems as lack of researches for the theory of determining additive amount of rare earth as well as solid solution of rare earth and mechanisms of action of the rare earth at grain boundary in steel, which could provide the thinking and references for design and wide applications of rare earth steel alloy.

Baotou Steel is one of the main production bases of heavy rail steel in China and large size nonmetallic inclusions are the bottleneck restricting improvement of quality of heavy rail steel. In this paper, the control technology for superfine dispersion of inclusions in heavy rail steel with magnesium is developed based on the physicochemical and metallurgical properties of magnesium. The comparative analysis between industrial tests of magnesium modification and traditional process showed that the inclusions in heavy rail steel such as MnS and CaO-Al₂O₃-SiO₂ were transformed into small size composite inclusions of MgO·Al₂O₃ and MnS, density of inclusions on vertical and horizontal observation planes and intermediate vertical observation plane of the rail were increased from 17 mm^-2, 21 mm^-2 and 18 mm^-2 to 22 mm^-2, 29 mm^-2 and 25 mm^-2 respectively, while equivalent diameters were decreased from 2.7 μm, 2.6 μm and 2.4 μm to 2.3 μm, 2.4 μm and 2.3 μm respectively as well as proportion of area of inclusions were decreased from 0.017%, 0.016% and 0.014% to 0.013%, 0.014% and 0.012% respectively after magnesium modification. Moreover, the nonmetallic inclusions in steel are rated as Grade A (0.5, 0.5), Grade B (0.5, 0.5), Grade C (1.0, 0.5), Grade D (0.5, 0.5) and Grade Ds (0) according to Method A as well as rated as 2.78 according to Method K. The inclusions of heavy rail steel after magnesium modification could meet the standard requirements.

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).

The effects of rare earth Ce on the microstructure and properties of V, Ti microalloyed steel are studied by tensile and impact tests as well as with such analysis means as transmission electron microscope, scanning electron microscope and energy spectrometer. The results showed that the interlamellar spacing of pearlite for test steel was decreased, inclusions containing titanium were changed from rectangle with sharp edge angle to smooth spherality as well as long and thin MnS inclusions became shorter and spherized with the increase of rare earth Ce content. Moreover, the yield strength and impact toughness of test steel are improved.

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.

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.

On the occasion of the 70th anniversary of establishment of Baotou Steel, the works done for transformation and upgrading of key technologies and equipment of rail of Baotou Steel, creating characteristic rail products with advantages of rare earth resources as well as developing new technologies and steel grades of rail to satisfy the demands of rail market at home and abroad are summarized in this paper. In the 70-year process of enterprise development, brand building of rail of Baotou Steel becomes mature continuously with the enterprise development. Relying on advantages of rare earth resources and technological inheritance, Baotou Steel strives to create characteristic brand of rail to support the brand development strategy of “rare earth rail” and puts forth effort to building rail products as well known brands at home and abroad. Moreover, the brand advantages are transformed into driving forces of enterprise development, various property indexes of rail products are continuously improved by closely combining with the demands of user side so that rail of Baotou Steel could always maintain advanced level in the industry.

The development of high performance rare earth steel with special effects of rare earth elements is of great significances for the utilization of rare earth resources and technological progress of iron and steel in Baotou, while it is the key for developing rare earth steel to clear the quantitative behavior of rare earth in steel. In the paper, the behaviors and mechanisms of rare earth elements in steel are discussed from such aspects as their thermodynamics, nucleation of rare earth inclusions and mechanism of internal friction for rare earth. Moreover, the non destructive characterization methods of rare earth inclusions are introduced.

With the rapid rise of production and sales volume for new energy automobile, the quantity demanded of ultra high strength automobile steel is increasing. The problems such as spring back, deformation and cracking in cold forming process of ultra high strength automobile steel become the main factors restricting its applications. Therefore, it is of practical application values and huge market potential to develop a kind of automobile steel with high strength and excellent formability. It is found in many studies that the comprehensive properties of automobile steel could be improved by adding rare earth elements. In this paper, two groups of composition schemes are designed and the same process parameters of annealing of reverse transformation (ART) are used. The influencing mechanisms of rare earth elements on the microstructure and properties of cold formed ultra high strength automobile steel are studied by means of tensile test, scanning electron microscopy and X-ray diffraction (XRD). The results showed that the microstructure of experimental steel was martensite, retained austenite and trace ferrite under the ART process, but content of retained austenite of experimental steel with rare earth in the two composition schemes was slightly higher than that of experimental steel without rare earth, which provided the microstructure basis for transformation-induced plasticity (TRIP) effect in subsequent forming process. Under the optimum heat treatment process parameters of quenching at 800 ℃ and holding for 5 min., then annealing at 645 ℃ and holding for 15 min., the content of retained austenite in experimental steel with rare earth in the first scheme is increased by 8.1% compared with that of experimental steel without rare earth, percentage elongation after fracture is increased by 21.8% as well as product of strength and elongation (PSE) is increased by 17.2% and reaches 28.47 GPa·%; in the second scheme, the content of retained austenite in experimental steel with rare earth is increased by 4% compared with that of experimental steel without rare earth, percentage elongation after fracture is increased by 2.8% as well as PSE is increased by 5.1% and reaches 34.8 GPa·%, which illustrate that the comprehensive properties of ultra high strength automobile steel could be improved to different extent by adding rare earth elements.

In this article, the effects of key hot rolling process parameters on the properties of hot dip galvanized extra deep drawing IF steel for home appliances are studied combining with production practices. The analysis on the texture, me-tallographic structure and mechanical properties of test steel at finishing rolling temperatures of 880 ℃ and 915 ℃ as well as coiling temperatures of 680 ℃ and 710 ℃ separately are carried out. The study results revealed the correlation between different hot rolling process parameters and texture, metallographic structure as well as mechanical properties of finished product of hot dip galvanized extra deep drawing IF steel for home appliances, which could be as the reference for improving the properties of hot dip galvanized extra deep drawing IF steel products through establishing reasonable hot rolling process.