With the process of desulphurization of hot metal-basic oxygen furnace-LF refing-vacuum degassing (VD) /RH treatment-continuous casting (CC), the yield is not closely related to the grade of steel, fluctuation of sulfur and oxygen content after add the rare earth, but it is strongly related to the type of processes. The effects of rare earth on denaturation of inclusions in steel are different for different steel grades. However, after add rare earth, the size of inclusions in steel decreases and their distribution becomes more dispersive so that the fatigue and impact performances are improved. The welding performance of steel plate after add rare earth is improved by delaying the formation of upper bainite and inhibiting the growth of austenite grains during welding.

The wide and heavy plate production line of Baotou Steel adopts the green and clean steel making, continuous casting, double-stand rolling and heat treatment processes. A kind of green and environment friendly high-strength wear-resistant steel plate with rare earth used for construction machinery is researched and developed. It is with high strength, hardness and excellent wear resistance, good low temperature toughness and welding performance as well as the idea of circular economy is through its whole cycle process of production and use.

In the paper, the key control and smelting process in each procedure of steel making for wheel steel with rare earth are introduced. The stable control for the yield of rare earth in steel and pourability of casting machine is realized with different controls of steel making process. Such procedures as KR desulfurization process, end point of converter, steel tapping, LF and RH refining process and casting in steel making are strictly controlled combining with the characteristics of deoxidation and desulfurization for rare earth elements to increase the yield of rare earth elements in steel. As a result, the yield of rare earth elements is guaranteed to be stably controlled at 38%~40% so that the production control for wheel steel with rare earth in steel making is completed.

In this paper, the steel-making production technology of adding rare-earth ferroalloy with the process route of LD-LF-RH-CC was studied. The results showed that the oxygen content of rare earth steel produced with trial production process was significantly lower than that of conventional steel. When the content of S in molten steel of tundish is lower, the inclusions are mainly RE_2O2S-CaO, RE₂O₂S and RE₂O₂S-Al₂O₃ below 2.0 μm, which are submicron inclusions with rare earth. The nozzle clogging materials are mainly deoxidation products of rare earth and aluminate of rare earth in steel as well as the aggregation and adhesion of rare earth inclusions are the main causes of nodulation.

In this paper, the control targets for the process of adding rare earth after VD are defined through the industrial test of adding rare earth into U75V heavy rail steel of Baotou Steel as well as the effects of rare earth on modification of typical inclusions in heavy rail steel are defined by sampling on the rail, analyzing the components of rare earth and characteristics of inclusions.

In the experiment of producing 25CrMoBVRE and U76CrRE, the ladle input method was used to add rare earth alloy. After pretreatment of hot metal, converter smelting, deoxidization and alloying process, deep desulfurization process in LF ladle refining, the sulfur and oxygen contents in molten steel were very low, which had positive effects on improving the yield of rare earth. The rare earth La-Si-Ca-Fe alloy and Ce-Fe alloy were added into ladle before and after VD by effectively controlling the oxygen and sulfur contents in molten steel as well as the amount added were 0.012% and 0.003% respectively. The test results showed that there was no nozzle clogging, the production process was trouble－free, operations were convenient, yields of rare earth could reach 15% and 40% respectively as well as costs were reduced by 60% and 50% respectively by taking corresponding protective pouring measures. The distribution of rare earth in steel is uniform, which can improve inclusions. The properties of products can fully meet the requirements of product standards and customer use.

In the paper, the control for each process of smelting rare earth is introduced. The test results showed that the rare earth was still with deoxygenation and desulfuration when the contents of oxygen and sulfur in steel were ultra low as well as the inclusions in steel were mainly tiny rare earth oxysulfides with the size of 3~5 μm. There is serious nozzle clogging during pouring process and the blockage is mainly cold steel. Such measures as improving the cleanness of molten steel and rare earth alloy, increasing pouring temperature and developing new-type nozzle are proposed by analyzing the mechanism of nozzle clogging to solve the problem of pouring nozzle clogging for rare earth steel.

Based on the experiment of adding rare earth into interstitial free(IF) steel of Baotou Steel, the changes of cleanliness of IF liquid steel were studied. The results showed that no rare earth oxides were found in the slag when steel ladle left RH. CeO and Ce₂O₃ were found in the slag during casting as well as the valence states were + 2 and + 3. The effects on oxidability and Ca-Al rate in slag were not great with and without adding rare earth. The content of TFe in tundish is about 5% and CaO/Al₂O₃ is stabilized at about 1.3. The size of Al₂O₃ along the thickness direction of casting blank for the heats without adding rare earth is larger and increases from inner and outer arc to the center of casting blank as well as it decreases and the quantity of Al₂O₃ increases after add rare earth.

On the basis of the original five round billets with Φ180~Φ270 mm of 2^# casting machine of Steel Tube Co. of Baotou Steel, Φ245 mm billet has been successfully developed by various studies such as the crystallizer structure design, design of vibration process for crystallizer, secondary cooling process and continuous straightening process for the billet. The production practices show that the internal and external qualities of Φ245 mm billet could meet the requirements of standard and rolling as well as its development reaches the desired effects.

In this paper, the effects of rare earth alloy addition on the internal quality and conventional mechanical properties of ingot blank are compared and analyzed by adding 0.003 0% ferro cerium alloy into the existing 310 Z-steel of Baotou Steel. The comparison results showed that the comprehensive mechanical properties of 310 Z-steel were effectively improved by adding the ferro cerium alloy.

The functions of rare earth Ce on metallographic structure, texture and magnetic properties of finished products of non-oriented electrical steel with 1.5% Si were analyzed with such equipment as the Zeiss microscope and X-ray diffraction (XRD). The results showed that the average grain size of metallographic structure of finished products increased after add 87 × 10^-6 Ce, the density of such textures as {111} and {110}<001>in finished products harmful to magnetic properties decreased as well as the average iron loss value P_15/50 decreased by 0.102 W/kg and the magnetic polarization intensity B₅₀ kept constant.

In this paper, the effects of adding rare earth into A572.Gr65 steel on its inclusions, microstructure and properties were studied with industrial experiments. The results showed that the inclusions in steel were mainly Al₂O₃ and Al₂O₃-CaO before add the rare earth and the size was about 5 μm as well as the inclusions were changed to spherical RE₂O₂S with the size less than 2 μm after add the rare earth. The thermodynamic and dynamics calculations showed that RE₂O₂S was the most easily formed inclusion in steel after add rare earth as well as the diffusion rate of RE³⁺ and Al³⁺ in the intermediate layer of RE₂O₂S·Al₂O₃ was the restrictive link of modified rare earth inclusions. After add the rare earth, the microstructure of hot rolled plate was refined as well as the impact and tensile properties were increased with the increase of rare earth content.

In the paper, the effects of rare earth elements on the mechanical properties and metallographic structure of welded joints of low-alloy high-tensile structural steel Q345E are compared and analyzed. The effects of rare earth on fatigue property of base metal and welded joint are analyzed from the control of grain size and inclusion of Q345E steel by rare earth elements.

In this paper, based on the chemical composition of U75V rail, the rare earth element Ce with contents of 0%, 0.002%, 0.004%, 0.006 and 0.008% was added into the rail respectively as well as the samples were prepared by such process as smelting in 25 kg induction furnace, ingot casting and rolling to explore the influences of Ce on the microstructure and corrosion performance of rail steel. In this experiment, the pearlite lamellar spacing of rail steel is affected by adding Ce element. With the addition of Ce element, the pearlite lamellar spacing is first decreased and then increased as well as reaches the minimum when adding 0.004% Ce and the corrosion resistance is also the best.

The Ce-Fe alloy is added at the stage of RH in the process of smelting IF steel to improve the overall performances of automobile sheet steel through industrial tests. The industrial sampling was carried out for the test results so that the type, size and microstructure of rare earth inclusions in the entire process of smelting were systematically analyzed with the SEM-EDS electron microscope, ASPEX automatic scanning of inclusions, X-ray diffraction(XRD) and thermodynamic calculation. The results showed that such inclusions as Al₂O₃ and MnS could be modified with rare earth Ce from RH to slab and rolled products so that such rare earth inclusions as Ce₂O₃, Ce₂O₂S and CeO₂ were preferentially formed, rare earth inclusions were gradually transformed from Al-O-Ce to such inclusions as Al-O-Ce, Ce-O-S and Al-O-Ce-S as well as the shape tended to be spherical and ellipsoidal and the size was below 5 μm.

In the paper, it is studied the mechanical properties and corrosion resistance of weather-resistant ribbed bar, influences of rare earth on corrosion resistance, composition of rust layer and determination of CCT curve for test steel in the laboratory. The trial production of rare earth weather-resistant ribbed bar with the characteristics of Baotou Steel by 6^# casting machine and billet process has been successful. Its test results such as the slab quality, mechanical properties and bending of products could meet the requirements of corrosion-resistant ribbed bar standard.

In the paper, it is introduced the types and change rules of stable compound after add Ce into the liquid steel are obtained by comparing the absolute values of gibbs free energy for the standard production of Ce and its compounds in liquid steel; it is elaborated the changing situations of rare earth content in liquid steel as well as its effect on w [S] in liquid steel and cleanliness of liquid steel for the heats without adding rare earth and with adding rare earth Ce when producing rare earth steel with the KR + BOF + LF + RH + CCM process route.

In the process of casting rare earth steel, the rare earth oxides enter the melting layer of casting powder, which affects and limits the normal play for metallurgical properties of casting powder. In the paper, the effects of rare earth oxides on melting temperature, viscosity and crystallization temperature of mould flux with different basicities are systematically analyzed aiming at the problem. The results showed that a small amount of rare earth oxides could facilitate the melting of casting powder as well as the melting temperature, viscosity and crystallization temperature of casting powder with different basicities were changed significantly with the increase of rare earth oxides content.

In order to study the high temperature deformation behavior of T91 steel containing 0.016% rare earth Ce, the thermal shrinkage test was carried out with the Gleeble-1500D thermal simulator. Its stress-strain curves were measured when the deformation temperature T was 1 100~1 250 ℃ and the strain rate was 0.5~5.0 s^-1. The constitutive equation of high temperature plastic deformation was constructed with the Zener-Hollomon parametric method, the energy dissipation diagram was calculated and the high temperature deformed microstructure was studied with optical microscope. The results showed that the stress-strain curves of T91 steel with rare earth Ce were without characteristics of double peaks and there was dynamic recrystallization; the hot deformation activation energy calculated by flow stress model was 559. 46 kJ·mol^-1, which indicated that the addition of rare earth Ce increased the hot deformation activation energy of T91 steel; rare earth Ce delayed the dynamic recrystallization process of T91 steel combining with the energy loss diagram and microstructure as well as dynamic recrystallization was easy to occur at high temperature and low strain rate.

The industrial production of non-oriented electrical steel 50W600 with rare earth is with the CSP production line. The microstructure, inclusions and texture of casting blank, hot rolled plate and finished plate were studied with such equipment as the transmission electron microscope, scanning electron microscope and X-ray diffraction (XRD). The main results were as follows: the development of columnar crystal for casting blank was suppressed obviously, space between dendritic crystal was decreased, ratio of equiaxed crystal was increased and banded structure of hot rolled plate was improved; the function of purifying liquid steel with rare earth was so obvious that the precipitation of MnS was reduced and precipitation of part of AlN was transformed from nubby and elemental to spherical and compound; the average grain size was increased, the favorable textures (100) and (110) were increased as well as the unfavorable texture (111) was reduced after annealing; the average iron loss was reduced by 0.4 W/kg and average magnetic induction intensity was increased by 0.011 T for finished products.

In the paper, the dissolution methods of such samples as steel and alloy are studied. Dissolve the samples with hydrochloric acid and nitric acid as well as the optimum instrument conditions of inductively coupled plasma mass spectrum (ICP-MS), select the spectral lines of elements to be tested with high sensitivity and fewer interferences as the analytical lines. The matrix matching is used to eliminate the influences of matrix effect in calibration curve so that the contents of lanthanum, cerium, praseodymium, neodymium and samarium in steel and alloys can be determined with the inductively coupled plasma source mass spectrometer.

In the paper, it is introduced the process of establishing the standard system of rare earth steel of Baotou Steel. Its principles and framework are determined, the relative standardization activities are carried out as well as the series of standards of rare earth steel products and basic universal standard of rare earth steel are organized to be formulated by summarizing and studying the construction of national steel standard system as well as the R&D, productions, sales and standardization of rare earth steel of Baotou Steel. On this basis, organize to declare the provincial standards, group standards, professional standards and national standards for related rare earth steel product standards, establish the build report and standard system program of rare earth steel standard system and complete the establishment of standard system of rare earth steel of Baotou Steel.