The effects of number of bottom gas supply component and bottom-blown gas intensity on mixing time of molten pool are studied through the water model test of bottom blowing system for 150 t converter in Steel-making Plant. The mixing time of 6 bottom gas supply components is the shortest with the same bottom-blown gas intensity; the higher the bottom-blown gas intensity, the shorter the mixing time with the same number of bottom gas supply component. The mode of bottom-blown gas supply in the processes of smelting different steel grades with 150 t converter is optimized combining with the results of water model test. As a result, the dephosphorization rate at smelting end-point could reach 92.3% and total iron content of slags at end-point of whole campaign could reach 17.3%, which could provide the technical guidance for improving the economic and technical norms of production.

In the external refining process, the elements of oxygen and sulfur are enriched in slag. In the process of smelting rare earth steel, the yield of rare earth is influenced. The reason is that the rare earth element Ce added with alloy reacts with the elements of O and S in slag to form compound so that a lot of rare earth elements remain in slag as well as just a small amount of them are into the link of pouring with liquid steel because of the active chemical property of rare earth elements. In the paper, the relation between refining slag amount and yield of rare earth element Ce is discussed through contrast test and analyzing the existence forms of rare earth element in refining slag. The results showed that the rare earth Ce in refining slag existed in the compound forms of oxides, sulfides and oxysulfides as well as the amount of refining slag affected the yield of rare earth Ce, which could provide the theoretical basis for improving it in industrial production process.

The effects of structure of retaining wall and dam on the flow condition of liquid steel in tundish are studied based on the physical model with geometric similarity ratio of 1∶4 established according to the similarity principle by taking the six-strand continuous casting tundish of bloom of Baotou Steel as the object of study. The results showed that the average retention time of liquid steel was increased by 5.51% and proportion of dead band was reduced by 20.73% by comparing the structures with and without retaining wall and dam. The flow condition of liquid steel in tundish could be effectively controlled, peak time and average retention time of each strand for tundish are increased as well as volume of dead band for the whole tundish is reduced so as to be beneficial to fully mixing liquid steel in tundish as well as aggregation and floating of inclusions.

In the article, a type of FeMnAlC series of low density steel is designed. Its tensile strengths of rolling direction (RD) and transverse direction (TD) are both greater than 1 300 MPa as well as it is with higher elongation. On the basis of ensuring stable high strength and toughness of the material, the corrosion behaviors of FeMnAlC series of low density steel in the simulated naval air environment with high temperature, humidity and salt spray are studied through the indoor accelerated test with alternation of wetting and drying as well as the tests with scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) to provide the references for evaluating corrosion resistance of the new generation of high strength low density steel.

The hot-rolled coil with X52MS pipeline steel for acid service by industrial production is chosen as the research object as well as its material performances are analyzed from microstructure and chemical components. Its resistance to hydrogen induced cracking (HIC) behavior in H₂S solution is mainly studied, the effects of microstructure and microregion components on the resistance to HIC are investigated by HIC test as well as the main causes for crack generation are analyzed so that its regularities are found out. It is summarized that banded structure is the main cause for failure of resistance to HIC for this material, carbon segregation and central aggregation of inclusion of carbohydrates and nitrogenous compounds would worsen the effects of banded structure on the HIC performance; the thought of low carbon component design is the premise of designing pipeline steel for acid service as well as reasonable control of nitrogen content is also one of the considerations in production of pipeline steel for acid service.

In this paper, the mechanical properties and metallographic structure of the joint with different welding technologies are compared and analyzed with the theoretical calculations of crack sensitivity index and preheating temperature as well as the methods of inclined Y-groove welding crack sensitivity test combining with operative weldability test of steel plate. Moreover, the JM-100 welding wire and 80%Ar+20%CO₂ argon-rich gas are determined to be adopted for welding the Q550D steel plate with thickness of 20 mm. The crack sensitivity index is 0.28, minimum preheating temperature is 13 ℃ and preheating treatment is not needed during welding. The welding heat input is controlled at 9.0~24.8 kJ/cm, temperature between weld passes is controlled below 200 ℃, mechanical properties of joint reach the best and there are no coarse and abnormal structures in weld seam and heat affected zone.

In this paper, the optimization plan of chemical composition, hot rolling and annealing processes is formulated through analyzing the influences of stress concentration, inclusions, chemical composition, mechanical properties and metallographic structure on fatigue strength with the metallographic microscope and field emission scanning electron microscope. The results showed that the tensile strength of material could be improved by 11~45 MPa by increasing the contents of carbon and manganese in chemical composition, reducing the content of harmful element sulfur as well as matching hot rolling and annealing processes so that the pearlite in metallographic structure was granular and with dispersed distribution. After made into the guide rail, its push-pull effort, service life and functions are tested as well as it is determined to be qualified according to the standard requirements.

In the paper, it is studied the effects of alloy elements on microstructure, mechanical properties and resistance to scute burst of high strength enamel steel for inside liner of water heater as well as analyzed the mechanism of action of hot rolling process such as finish rolling temperature, coiling temperature and continuous annealing process of cold rolling on microstructure and mechanical properties. The trial production results showed that the yield strength was 245~272 MPa, tensile strength was 362~386 MPa and elongation was 39.0%~41.0% for the cold rolled high strength enamel steel, which could meet the production requirements of inside liner of water heater. Its microstructure is mainly composed of ferrite and pearlite as well as a little MnS and TiN particles were with dispersed distribution. It is further verified that the developed high strength enamel steel is with good resistance to scute burst through the sensitivity test of anti scute burst and test of end user.

The independent research and development has been carried out by Baotou Steel according to the technical requirements of steel for protective base plate of special vehicle for users. Its reasonable chemical compositions, rolling and quenching and tempering processes are designed as well as the microstructure is determined and mechanical properties are analyzed. The results showed that its mechanical properties were excellent, yield strength was 730~770 MPa, tensile strength was 826~860 MPa, elongation after fracture was 18.0%~20.0% and low temperature impact absorbing energy at -40 ℃ was 203~256 J, which could meet the technical requirements of users.

In this article, the current status of processes and equipment for smelting and rolling heavy rail steel in domestic manufacturing enterprises of heavy rail is mainly introduced. The advantages and disadvantages of different steel-making processes are analyzed through comparing the technical indicators achieved by different control modes of different smelting processes, pretreatment of hot metal, smelting with oxygen top-blown converter, refining with ladle furnace (LF), vacuum degassing and continuous bloom casting; the effects of different processes on product quality and the product range that can be rolled are analyzed through comparing the process characteristics of different layout forms of rolling modes such as continuous rolling modes of universal three stands, universal three stands 2+1, universal five stands 2+2+1 and universal four stands 3+1 so that the advantages and disadvantages of different rolling processes are elaborated. In addition, the straightening machine and detection equipment of heavy rail are briefly introduced.