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Table of Content

    05 February 2018, Volume 34 Issue 1
    Development and application of high efficiency blowing technology of converters in Shougang
    2018, 34(1):  1-9. 
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    In order to solve the problem that the actual converter bottom blowing effect was difficult to guarantee due to low bottom blowing intensity and the slag splashing technology under high converter campaign life,high efficiency bottom blowing technology for converter steelmaking was developed in Shougang Co.,Ltd. (SGQG). During the development process,a series of key technologies such as optimization of bottom blowing tuyeres arrangement and pool mixing flow field,exposure technology of bottom blowing tuyeres under the conditions of slag splashing,bottom blowing tuyeres long life technology,etc. The optimization of bottom blowing mode was carried out,and the stable control of converter bottom blowing effect was achieved,even at the late age of the campaign,the carbon oxygen product could still be less than 0.0020 under the converter campaign life of about 6500. By applying the above technologies,in the production of ULC and IF steel (converter end point carbon mass fraction was 0.025%~0.05%),the average reduction of converter end oxygen mass fraction was more than 0.025%,TFe mass fraction in end slag was more than 4%,and the erosion of refractory materials was significantly reduced,converter dephosphorization efficiency was significantly improved.

    Technologies of purification production in electric arc furnace steelmaking processes
    2018, 34(1):  10-19. 
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    Based on the application of purification production technologies in electric arc furnace (EAF) steelmaking processes,this article introduced and analyzed the technology developments in high efficiency and purification of EAF steelmaking,such as scrap crushing and sorting,combined blowing,gas-solid injection,quality analysis & cost control and application of CO2. It is indicated that the key to improve product quality and competitiveness of EAF steelmaking is to speed up the technological innovation of purification production and construct the clean production platform for EAF steelmaking processes,which is one of the key development directions of EAF steelmaking in the future.
    Experimental study on recycle utilization of slag after gasification dephosphorization in 60 t converter
    2018, 34(1):  20-24. 
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    In order to study recycle utilization effect of slag after gasification dephosphorization,The comparison experiment of gasification dephosphorization with coke powder was carried out in Tangsteel 60 t converter. The results showed that adding coke powder for gasification dephosphorization was feasible during the slag splashing stage. According to the multi-furnace phosphorus balance algorithm,the average dephosphorization rate of the test furnace was 25.06%. Compared to conventional smelting furnace,the slag mount of gasification dephosphorization furnace had decreased for 8.66kg per ton steel,which meant a reduction of 7.45%. The phosphorus content of end molten steel of test furnace was fluctuated at around 0.02%,which meant that the recycle of the gasification dephosphorization slag would not affect the dephosphorization effect of subsequent furnace.

    Water modeling experiment research on structural optimization of eight-strand tundish

    2018, 34(1):  25-29. 
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    Based on the size of ratio 1:3 of the tundish in The 1st Plants of Hansteel,the water modeling experimental research of a eight-strand tundish was investigated,According to the RTD curves analysis of flow distribution under various flow control devices,the structure of the tundish was optimized. By adjusting V shape wall hole to the axial direction,the response time of edge flow was reduced and the various flow synchronization was improved. Through setting the double low dam on each side,matched with V shape wall,the reserved time of central two stands was prolonged. The optimized structure “new wall + current stabilizer + double low dam” was used,the average reserved time of steel in tundish was effectively prolonged,the dead zone volume was reduced,the initial response time of each flow was delayed,the RTD curve peak time difference of eight flow decreased,and it benefitted for uniformity of steel temperature in tundish.
    Numerical simulation of heat transfer and solidification in GCr15 steel bloom
    2018, 34(1):  30-35. 
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    The solidification mathematical model was established by using GCr15 steel bloom as a research object. The effects of superheat,casting speed and cooling water on the solidification process of bloom were studied. By analyzing the center solid fraction and liquid core length of the bloom,the optimum F-EMS position was determined and the casting speed was optimized. The results showed that the superheat had the little effect on the solidification of the bloom. With the increase of the superheat,the surface temperature of the billet increased,the length of liquid core and the length of liquid zone increasd,while the length of two-phase zone decreased. The effect of casting speed was the largest,the surface temperature,the length of liquid core,the length of two-phase zone and the length of liquid zone were all increased with the increase of the casting speed. With the increase of the water ratio,the surface temperature of the billet and the length of the liquid core decreasd. When the water ratio was 0.29 L/kg,the superheat degree should be controlled at 15–35℃,the casting speed could be controlled in the range of 0.46–0.49 m/min,and the best casting speed was 0.48 m/min.
    Research on surface and subsurface slag inclusion in SPHC slabs
    2018, 34(1):  36-43. 
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    The distribution,type,composition and formation cause of slag inclusion on the surface and subsurface of continuous casting SPHC slabs had been researched and discussed through observing metallographic samples by optical microscope,SEM and energy spectrum analysis. The result showed that,the slag inclusion could be classified into four characteristic types with different formation mechanism. Slag entrapment of continuous casting mould powder and big-size deoxidation products dropped out from submersed nozzle sediments were the principal source of slag inclusion in continuous casting SPHC slabs. Raising the cleanliness of molten steel,maintaining the stability of continuous casting,alleviating the fluctuation of liquid level in mould,strengthening the anti-fluctuating ability of molten slag layer were helpful to reduce the incidence of slag inclusion in continuous casting slabs.
    Evolution of Al-Ti-Mg-O inclusions during refining and casting process of interstitial free steel
    2018, 34(1):  44-50. 
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    The evolution of chemical composition,size,proportion,and morphology of the Al-Ti-Mg-O inclusions during the steelmaking process of interstitial free (IF) steel were investigated by means of Auto-SEM. Results showed that after RH deoxidation,the main inclusions were pure Al2O3 inclusions. Then the proportion of Al2O3 in inclusions decreased,while the proportion of inclusions containing titanium and magnesium increased from RH deoxidation to slab. The size of pure Al2O3 inclusions was larger and the size of inclusions containing titanium was smaller. Thermodynamic analysis resulted showed that the inclusions should be stable with Al2O3 at the concentration of molten steel. But the titanium alloying and spontaneous enrichment would make a high titanium concentration environment that was in favor of the TiOx existence. Moreover,more TiOx component could control Al-Ti-Mg-O inclusions with a lower melting temperature.
    Optimization of phosphorus and sulfur in high-grade welding wire steel production process
    2018, 34(1):  51-56. 
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    Five heats of industrial trials were performed to investigate the cleanliness of high level welding wire steel produced with hot metal after desulfurization and dephosphorization pretreatment.The variation of T.O contents and the transformation route and mechanism of inclusions in the steel were studied by system sampling during steelmaking processes.The results showed that the average oxygen mass fraction was 610.2×10-6 at the converter end,484×10-6 at RH start,220×10-6 before adding aluminum alloy,4.6×10-6 at RH end,and the overall control was better. The inclusions were mainly MnO-SiO2-Al2O3 at RH start,which shapes were mostly spherical,and the sizes of some inclusions were more than 20 μm. The inclusions were mainly Al2O3 inclusions and a little MgO-SiO2 inclusions after RH treatment to slabs.
    Research and prospect on rare earth treated steel
    2018, 34(1):  57-64. 
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    Rare earth treated steel can significantly affect the mechanical properties,high temperature oxidation resistance,corrosion resistance,weldability and magnetic property of steel,the function mechanism of rare earth elements in steel and its effect on performance of the steel were summarized. The research and development progress,the production status and the application of rare earth treated steel at home and abroad were reviewed in recent years. At the same time,some troubles on production of the rare earth treated steel were mentioned,and the trend and the prospect on developing the rare earth treated steel were proposed.
    Practice of on-line treatment of converter slag by air-granulated and steam self-disintegrated technology
    2018, 34(1):  65-70. 
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    The principle, process and equipment of converter slag air-granulated and steam self-disintegrated technology were introduced respective. The chemical composition,mineral composition and microstructure of air-granulated slag and steam self-disintegrated slag were analyzed. Combined with the production, practice of on-line processing of converter slag by combination of air-granulated and steam self-disintegrated technology was introduced. According to the aspects of technology, energy utilization, utilization of steel slag and the cost, the advantages and future improvement direction of combination of air-granulated and steam self-disintegrated technology were analyzed.
    Research on the dissolution rate of limestone and lime in high FeO slag
    2018, 34(1):  71-74. 
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    The effects of temperature on the dissolution rate of limestone and lime were studied in this paper,and their dissolution rates in pre-slag containing high FeO were also compared at 1 300,1 400 and 1 500 ℃,using a length of 10 mm limestone cube and lime cube as the test sample. The results showed that the dissolution rate of limestone was obviously faster than that of lime under the experimental conditions. The dissolution rate increased with the temperature,it would double when the temperature increased from 1 300 ℃ to 1 400 ℃. There was a stagnation period lasting about 10 to 30 seconds during the dissolution process of limestone and lime at different temperatures,and which the dissolution rate of limestone was lower than lime due to its heat absorption. After the stagnation period,the dissolution rate of limestone was greater than that of lime.
    The effect of 2CaO•SiO2 on the enrichment behavior of phosphorous in slag
    2018, 34(1):  75-78. 
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    The effect of slag constituent and 2CaO•SiO2 content on the enrichment behavior of phosphorous in slag was studied by SEM and EDS. The results showed that phosphorous distributed uniformly in 2CaO•SiO2. The L_"P" ^(s/l) (phosphorus distribution ratio between solid and liquid phase of slag) increased with the increase of (SiO2+P2O5) and (FetO) content before it reached the maximum and then began to decrease. The maximum value was obtained when the (SiO2+P2O5) and (FetO) mass fraction was 20% and 70% respectively. The L_"P" ^(s/l) changed little with the ratio of 2CaO•SiO2 particles.