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    Steelmaking    2005, 21 (06): 58-62.  
    Abstract869)            Save
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    Research on control equipment of straight edge crack defect of medium plate
    Steelmaking   
    Accepted: 01 January 1900

    Research and practice of non-metallic inclusion control process for wheel steel SCX400
    Steelmaking    2020, 36 (6): 54-60.  
    Abstract123)            Save
    The cleanliness problem of SCX400 wheel steel plates was checked by SEM and the results showed that the dot-line macro-inclusions inside the steel plates shaped from the big CaO-MgO-Al2O3 inclusions during rolling process, and those inclusions oriented form refining and casting process, not floating up into slag, consequently kept inside of slabs. Base on this study, actions were implemented to change inclusion into solid classes before RH process as Al2O3, MgO-Al2O3 or high melting point CaO-MgO-Al2O3 who have better tendency to float upon, and then global Al2O3-MgO-CaS inclusions, with high melting point. After that, inclusions were tested as Al2O3 or Al2O3-CaO cores coated by CaS inside the plate. The single-test qualified rate increased from previous 90 % to current 95.4 %, whilst cracking defect rate in production decreased to 0.5 %-1.0 % and the fatigue lifetime of wheels stabilized beyound million times.

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    Process research on LF with steel scrap as the addition
    Steelmaking    2020, 36 (5): 27-31.  
    Abstract161)            Save

    Due to the slump of steel scrap price in domesticusing steel scrap as the raw material for converter smelting can greatly reduce the production costs. Combined with its own process featuresTianjin Tiangang United Special Steel Co.Ltd. fully used the arc heat source of LF furnace and the residual temperature of molten steel to melt steel scrap. According to the thorough research on the melting mechanismmelting and mixing time and inclusion analysis of steel scrap adding to LF refining furnacethe reasonable process of LF refining furnace with steel scrap as the addition was determinedthus the steel scrap ratio in steelmaking was improvedand the iron loss was reduced. Through production practicewhen LF refining furnaces were fed with steel scraps reaching 1.54t per furnace in June2019iron loss could be reduced to 10.56kg/t. By means of benefit accountingwhen a gap between the price of steep scraps used in LF refining and the sales price of actual steel billets reached more than 280yuan/tdistinct economic benefits could be produced. Furthermoreadding steel scraps during LF refining didn’t cause adverse effects to the quality of molten steelThe endpoint oxygen level met steel grade requirementsand showed remarkable effects.

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    Practice on control of oxygen and inclusions for 50Cr5MoV backup rolls
    Steelmaking   
    Accepted: 01 January 1900

    Numerical analysis of flow field based on the new desulfurization agitator of KR method
    Steelmaking    2020, 36 (5): 14-20.  
    Abstract91)            Save

    In order to improve desulfurization equipment and technology of hot water pretreatmentand improve the desulfurization efficiencya new type of agitator was formed through combining the advantages of agitator and spray gun with reference to the traditional KR desulfuration method. The flow field in the hot metal tank was analyzed by Fluent software and Eulerian model. The effects of different eccentricitystirring speed and ventilation flow of the agitator on the desulfurization effect were studied from the aspects of flow velocity and gas distribution. The results showed that the new agitator could enhance the flow fieldand the desulfurization gas ejected by the nozzle at the bottom of the agitator would make the desulfurization gas spread more widely and more evenly in the iron tank. When the new agitator had a stirring speed of 150 r/minventilation flow rate of 5.0 m3/h and eccentricity of 0.3the distribution and intensity of gas was the bestand the flow field had a large average velocitywhich was beneficial to the reaction of hot metal and desulfurization agent.

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    Development and prospect of Mg clean steel technology
    Steelmaking    2020, 36 (5): 1-13.  
    Abstract193)            Save

    Nonmetal inclusion control has always been an important subject in clean steel production. In recent years,the focus of Mg application in steel has changed from the traditional modification of inclusions to the microalloying. This paper reviews the research status of Mg application in steel at home and abroad,represents the advantages of Mg from several aspects,such as cleanliness control,oxide metallurgy,solidification microstructure refinement,slab crack control,etc. The possible development fields and directions of magnesium clean steel are also analyzed and prospected.

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    Research on slag entrainment by vortex during continuous casting in 250t ladle
    Steelmaking   
    Accepted: 01 January 1900

    Effect of antioxidant in MgO-C brick on acid soluble aluminum in tire cord steel
    Steelmaking    2020, 36 (5): 69-74.  
    Abstract107)            Save

    In order to avoid the formation of brittle inclusions in tire cord steel, the measures that controlling the Al content of charge and alloy and making low basicity slag system in LF refining furnace were adoptedand the mass fraction of acid soluble aluminum (Als) in molten steel could be controlled at about 9×10-6. By optimizing the type and content of antioxidants in ladle magnesia carbon lining brick, reducing the metal Al powder from 1.61% to 0.15%, and replacing the rest by the same amount of Si powderw(Als) in molten steel reduced from 8.8×10-6 to 6.1×10-6, with a decrease of 30.7%. The average mass fraction of Al2O3 in typical composite inclusions in steel reduced to 8.6%, while the maximum was 23.8%. The inclusions could be controlled in the plastic zone of low melting point.

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    Optimization on bottom blowing process in converter steelmaking with semi-steel
    Steelmaking    2020, 36 (5): 21-26.  
    Abstract78)            Save

    To solve the problem of low bottom blowing effect and fast erosion of bottom tuyeres caused by high oxidability of slag during semisteel steelmaking in Pangang Group Xichang Vanadium & Steel Co.,Ltd.,measures such as application of new bottom blowing tuyeres,optimization of bottom tuyeres arrangement and optimization of thermalreplacement scheme were adopted. Bottom blowing effect during the converter campaign was improved. Industrial application indicated that after the optimization of bottom blowing process,mean thermalreplacement time was shorten by 95 min,average phosphor distribution ratio(LP)between steelslag during the whole converter campaign was improved from  78.0  to  92.5,mean TFe mass fraction in endpoint slag was reduced form 19.7 % to  18.6 %,and average carbonoxygen concentration product at endpoint was reduced from 0.002 8  to 0.002 3. Production efficiency of converter steelmaking was improved and cost of BOF blowing was reduced as well.

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    Analysis and control of break out in the bloom continuous casting process
    Steelmaking    2020, 36 (5): 52-57.  
    Abstract127)            Save
    Aiming at the frequent break out accidents in the second cooling zone of continuous casting bloom of Q235KZ steel,the SEM,composition analysis,viscosity measurement,and simulation calculation were used for investigation. The results showed that longitudinal crack was found on the surface of bloom and the largesized slag existed near the shell of breakout. Besides,it was found that the thickness of solidified shell was unevenly distributed. In the exit of the copper mold,the thickness of the thinnest shell was 7.9 mm,while that of the thickest was 20.2 mm. The frequency of break out was significantly reduced by increasing the alkalinity of protective slag,reducing the heat transfer rate of slag film,optimizing water distribution in the secondary cooling zone.
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    Study on evolution behavior of the quicklime reactivity under high temperature
    Steelmaking    2020, 36 (5): 79-84.  
    Abstract193)            Save

    The disintegration caused by f-CaO is one of the main obstacles to the utilization of steel slag. The f-CaO come from the incomplete dissolution of the quick lime and the decomposition of tricalcium silicate. In terms of the f-CaO derived from the undissolved limeit is necessary to strengthen the dissolution behavior of lime in the converter process. The lime reactivity plays a key role on its dissolution, and is closely related to its microstructure. The evolution behaviors of the reactivity and microstructure of quick lime under high temperature were investigated in this work. The lime samples were prepared in the laboratory, the microstructure was detected and analyzed by SEM, XRD and a mercury-injection instrument, and the reactivity was test according to YB/T 1052005 standard. The results showed that when temperature increased, the reactivity and porosity of the quick lime decreasedand the average diameter of pores increased. The CaO crystals grew gradually under the action of the grain boundary migration. The change of microstructure was closely related to the change trend of lime activity. On basic of the growth of CaO crystal and the decrease of the porosity, the lime activity decreasedwhich would obstacle the dissolution of quick lime during the steelmaking process and increase the content of f-CaO in the slag.

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