In this paper, the microstructure and macrotexture of Hi-B steel at various stages of production are analyzed with such detection means as Zeiss microscope and X-ray diffractometer. The results showed that the microstructure of Hi-B steel was ferrite at all production stages. The microstructure is completely recrystallized after decarbonizing and nitriding annealing and average grain size is 28.92 μm as well as secondary recrystallization is completed after high temperature annealing and average grain size of finished product is about 2 cm. The texture types in sub-surface of hot rolled plate are mainly three types of typical shear textures. The texture of cold rolled plate is mainly composed of α line texture and rotating cube texture {001}<110>, the texture after decarburizing annealing is mainly α^* texture and γ line texture {111}<112> as well as the macrotexture after high temperature annealing is mainly Goss texture. The texture of Hi-B steel after stretching, leveling and annealing is single Goss texture with accurate orientation as well as its strength reaches peak.

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 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 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 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.

In this paper, the differences of microstructure, mechanical properties and resistance to hydrogen sulfide stress corrosion between as-hot-rolled steel pipe and quenched and tempered steel pipe are compared and studied. The study results showed that the microstructure of as-hot-rolled steel pipe consisted of bainite, martensite as well as a small amount of ferrite and pearlite, its tensile strength could meet the requirements of technical agreement, but elongation was close to lower limit of the requirements of technical agreement; the microstructure of quenched and tempered steel pipe was tempered sorbite, strength and toughness and ductility were significantly improved compared with those of as-hot-rolled steel pipe, impact energy at 0 ℃ was over 2.5 times of lower limit for the requirements of technical agreement as well as it is with good resistance to hydrogen sulfide stress corrosion.

In this paper, it is introduced the online accelerated cooling process test of a type of hot rolled C-Mn seamless steel pipe in 460 production line of Baotou Steel Pipe Co., Ltd.. The test results showed that the effects of online accelerated cooling process on microstructure and properties of test steel were significant, generation of proeutectoid ferrite in two phase region could be restrained by online controlled cooling so that the matrix grains were refined as well as grain size was increased from level 6.5 under non controlled cooling conditions to level 8 and the banded structure of steel was improved. The mechanical properties and impact properties of steel pipe are significantly improved, the yield strength could reach 300~345 MPa, tensile strength could reach 485~545 MPa, average value of longitudinal impact energy at room temperature could reach 102 J, average value of longitudinal impact energy at 0 ℃ could reach 86 J and average value of longitudinal impact energy at -20 ℃ could reach 60 J.

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.

The SS steel grade rail with 60E1 cross section is manufactured with small batch production by comparing the rails with 60E1 and 115RE cross sections, optimizing chemical composition, adopting narrow composition control, increasing C content, controlling contents of Mn and Cr as well as optimizing rolling process. The rail performances could reach R_p0.2≥512 MPa,R_m≥982 MPa,A≥10% and tread hardness (HB) ≥310. The small batch industrial production practices prove that the production process of SS steel grade rail with 60E1 cross section is trouble free and its performances are stable, which could meet the user needs so that it can be produced with incremental quantity.

In this paper, it is introduced the current situations of such rail standards as AREMA Railway Engineering Maintenance Manual(2020), European Standard EN 13674-1:2011+A1:2017 and China Railway Industry Standard TB/T 2344.1—2020 as well as mainly compared and analyzed the differences of cross section, compositions, properties and test methods for rails satisfied the above three standards. The analysis results showed that the differences of technical requirements for rails satisfied the above three standards were greater due to the level and style of domestic and foreign standards were different. The export level of domestic rails is fully known by comparing these differences, which creates conditions for exporting domestic rails to the international market.