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2018 Vol. 53 No. 9
Published: 2018-09-15
1
XIE Quan-an，WEI Zhen-kai，GUO Rui，CHENG Huan
Present situation of evaluation method of coke thermal properties
Coke is one of the most important raw materials for blast furnace ironmaking. The property of coke is related to the efficiency and cost of blast furnace process directly. The thermal property of coke has become a rising concern in the coking and iron making industry. New methods were proposed to test the thermal properties of coke constantly based on the experimental results. It is important to obtain a simple and practical coke thermal property index for blast furnace production. The work reviews some progresses in reaction behavior of coke in blast furnace and evaluation methods of coke thermal property. The characteristics of coke thermal property evaluation methods were summarized. Some new ideas and research directions about coke reaction behavior and coke property evaluation were also proposed.
2018 Vol. 53 (9): 1-6 [
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7
LAN Dong，，LI Ting-le，，SUN Chang-yu，，WANG Qi，
Slag evolution of Ti-bearing high basicity sinter during softening-melting process
It is generally accepted that Ti-bearing sinter is more difficult to smelting in blast furnace process than common sinter because of its low content of Fe， complex compositions and mineral phase. However， the blast furnace coefficient in smelting Ti-bearing sinter is not inferior to that of some common sinter in practical production which may result from the difference of the slag evolution between Ti-bearing sinter and common sinter. In order to clarify the reasons for the difference and analyze the performance of Ti-bearing sinter in BF， the softening-melting property of Ti-bearing sinter was test firstly. Then samples interrupted at the softening-melting characteristic temperature were analyzed by scanning electron microscopy and X-ray diffraction in order to clarify the slag evolution of Ti-bearing high basicity sinter during softening-melting process. The results show that softening-melting temperature of Ti-bearing sinter was lower， the max pressure drop was 547 kPa which was lower than common sinter with the same basicity. In softening-melting process， the mineral phase of slag contained FeO， melitite and proviskite and the kinds of mineral phase of slag were unchanged. The main reason for low softening and melting temperature of Ti-bearing sinter was low eutectic temperature of the slag. The pressure drop curverised twice in softening-melting process which may resulted from the large difference of melting temperature between slag and metal.
2018 Vol. 53 (9): 7-13 [
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14
MA Hong-xiu，ZHANG Jian-liang，JIAO Ke-xin，CHANG Zhi-yu，WANG Yi-jie，ZHENG Peng-chao
Analysis of erosion characteristics and causes of blast furnace hearth
To further study erosion characteristics of carbon brick and common causes of lining erosion of blast furnace hearth，two domestic blast furnaces were investigated and the situations were analyzed. Based on the field data，the thickness of the hearth and the floating height of dead man were calculated，respectively. The root cause of erosion of hearth was identified，and the location of the erosion has been determined. The results showed that when the permeability of the dead man becomes worse，the circulation of molten iron is aggravated，resulting in erosion of brick in the root of dead man. However，the floating height of dead man varies correspondingly with the practical production parameters. An example was given，which verified the location of the erosion of the blast furnace hearth within the 1-3 m range below the tap hole. The key to prolong the service lies in the stable raw materials supply，operation and establish of mechanism，a system to check monitoring the floating height of dead man and residual thickness of carbon brick.
2018 Vol. 53 (9): 14-19 [
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LI Chen-xiao，，WANG Shu-huan，，XUE Yue-kai，，ZHAO Ding-guo，，ZHANG Ming-bo，HAN Yu
Experiment on gasification dephosphorization with coke powder reducing converter molten slag
In order to realize the gasification dephosphorization process in converter slag splashing stage which is beneficial to avoid the P enrichment and achieve the recycling of the dephosphorized slag in subsequent furnaces， the experiment of reduction of converter slag by coke powder in the laboratory was carried out. The results showed that with the increasing of the experimental temperature， the gasification dephosphorization rate of coke powder gradually increaseed， and the gasification dephosphorization rate at 1 900 K could reach up to 82.35%. The gasification dephosphorization rate decreased with the increasing of the slag basicity. When the amount of the added coke powder is sufficient， increasing mass percent of FeO of slag properly was favorable for the gasification dephosphorization reaction. When the coke particle size was between 0.5-2.5 mm， the gasification dephosphorization rate changed little， about 58%， but when the coke particle size between 2.5-3.5 mm， the gasification dephosphorization rate dropped to 52%. In the P-rich micro-region， mass percent of C was inversely proportional to mass percent of P， confirming that the coke does participate in the gasification dephosphorization reaction. The results provided some theoretical guidance for industrial development.
2018 Vol. 53 (9): 20-24 [
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25
MIAO Zhi-qi，CHENG Guo-guang，LI Shi-jian，CHEN Lie，LIU Zhi-quan，LI Cheng-wei
Mathematical model of electrode immersing depth in industrial electroslag remelting process and application
In order to predict reasonable electrode immersing depth in different electroslag remelting processes， the corresponding slag pool resistance values for different electrode-immersing depths， slag amounts and slag conductivities under steady-state conditions in the industrial electro-slag remelting process were obtained based on the MHD model in Fluent software. Then combined with the actual factory production regulations， an electrode-immersing depth mathematical model was deduced from the relationship of the voltage， the current， the slag weight and the slag conductivity. The results of the comparison between the calculated values and the measured values showed that the relative error of them was very small. The cleanliness of the steel was obviously improved and the problem of the oxidized Al elements and the excessive increase of oxygen was effectively solved by adjusting the slag system and increasing the slag amount in actual production situations based on the aforementioned model.
2018 Vol. 53 (9): 25-29 [
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30
ZHAO Jun-pu ，，LIU Liu，RAO Jin-yuan
Effect of solidification reduction process on center compactness of continuous casting bloom
In order to improve the center compactness of continuous casting bloom，the effect of post solidification reduction process on the center shrinkage cavity existing in the bloom was studied. The deformation behavior of shrinkage cavity during solidification reduction was analyzed using thermo-elastic-plastic model. The results revealed that the center compactness of bloom can be effectively improved when reduction technology was applied after complete solidification，and the effect is 22.5% higher than hot rolling under the same deformation. With the increase of reduction amount，the size of the center shrinkage cavity is significantly reduced. However，it is difficult to completely eliminate the large size shrinkage cavity due to the limited reduction amount of post solidification reduction. To further eliminate the shrinkage cavity，it is advisable to increase the soft reduction rate to 0.02 mm/s at the end of solidification to reduce the initial size of shrinkage cavities，or increase the post solidification reduction amount. Post solidification reduction technology was applied to the production of continuous casting bloom SA-213 T12. Experiment result shows that most of the center shrinkage cavities have been welded. The size of the remaining shrinkage cavities is reduced from 8 mm to 2 mm，and the number is reduced by 50%.
2018 Vol. 53 (9): 30-36 [
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37
GAO Jian-bing，CHANG Peng-fei，ZHANG Bin-bin，JIANG Zhou-hua，LI Hua-bing
Effect of Ce on inclusion modification in a new type super duplex stainless steel 2707HD
In order to improve the cleanliness of the steel and realize the harmlessness control of the inclusions, the effect of Ce on inclusion modification behavior of a new type super duplex stainless steel 2707HD was researched. The possible inclusions generate type in super duplex stainless steel with Ce was preliminary determined by thermodynamics calculation. The sizes，morphology and type of inclusions were characterized and analyzed by metallographic microscope，scanning electron microscope，energy dispersive spectrometer and Image-Pro6.0. The results showed that the tiny inclusions （less than 1 μm） and 1-2 μm inclusions increase，while the proportion of inclusions larger than 2 μm decrease in the super duplex stainless steel with mass percent of 0.03% Ce. The proportion of inclusions smaller than 2 μm decreased，and inclusions larger than 5 μm were formed with mass percent of 0.06% Ce. Ce can transform irregular Al2O3 inclusions into regular Ce2O3 and Ce2O2S rare earth inclusions and accompanied by the formation of Ce2O3-Ce2O2S and CeAlO3-Ce2O2S composite inclusions. Moreover Ce element can effectively decrease the amount of irregular inclusions.
2018 Vol. 53 (9): 37-44 [
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45
MA Li-dong，，HUANG Qing-xue，，CHEN Shuo，MA Hao-xi
Optimization of varying curvature profile of two-roll bar straightener
Based on the problem that requirements of the high straightness accuracy and the surface quality of the high quality bar cannot be satisfied at the same time，a variable curvature roll design method was proposed. The straightening roller was composed of multi parts，and the curvature was increased uniformly from two ends to the center of the straightening roller according to a given value. This method can improve the contact unevenness caused by the curvature mutation during the contact between the straightening roller and the bar，so as to achieve the goal of improving the surface quality. Further，the curvature analysis model of the whole process of the two-roll bar straightening process was established. The theory was verified by the field roll profile and process parameters，and the accuracy of straightening was consistent. Through the continuous bending and the springback analysis of the roller straightening process with different curvature ranges，the principle of optimizing the variable curvature roll profile was obtained as following：The variable curvature range can straighten various specifications of the bar in the product outline and has a reasonable curvature margin for the straightening demand，considering the fact that the bending curvature decreases due to the wear of the straightening roller. Numerical method was adopted to verify the roll shape design method，and numerical results showed that the straightening accuracy of the bar was 0.54 mm/m，which satisfied the requirement of 1 mm/m in the production site. The results showed that the roller design method can meet the need of the straightening bar.
2018 Vol. 53 (9): 45-52 [
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53
SUN Bin，YOU Hong-guang，HAO Ming-xin
Kinetics of high temperature oxidation of 0.09C-0.5Mn-0.22/1.9Si steel
In order to evaluate the effects of Si on oxidation kinetics behavior of steels， the oxidation behaviors of Fe-0.2Si steel and Fe-2Si steel at 900-1 200 ℃ in the air-steam atmosphere were investigated by TGA in order to calculate the oxidation rates of two steels. The activation energies of the two steels were obtained. The results show that the oxidation kinetics cures of the two steels obey linear law in the early stage of oxidation process. It appeared that a critical thickness of scale existed，at which the law of the scale-growth mechanism changed from linear to parabolic. The critical thickness of scale increased with the silicon mass percent in the steel increasing and the temperature rising.
2018 Vol. 53 (9): 53-56 [
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57
ZHU Rui-qi，SONG Xin-li，ZHENG Ai-qin，CHEN Rong-dong，JIA Juan，FAN Li-xia
Microstructure characteristic and mechanical properties of hot rolled DP600 steel
In order to research the microstructure characteristic and mechanical properties of high strength dual phase steel DP600，the strength and plasticity was measured by tensile testing machine. The microstructure and inclusion and dislocation were analyzed by scanning electron microscope and transmission electron microscope. The results showed that the ferrite and martensitic were both obtained in dual phase steel DP600. With the increase of static stretching strain，the dislocation density increased and the dislocation tangle was more serious and crack initiated at the interface of inclusions or at the grain boundary of ferrite and the crack was found in martensite island. The yield strength was 394.9 MPa，tensile strength was 641.6 MPa. Plastic strain hardening index[n]was 0.154 and yield ratio was 0.616. The mechanical properties of hot rolled DP600 steel were higher than the cold rolled and annealing dual phase steel of the same class.
2018 Vol. 53 (9): 57-62 [
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63
FU Yuan，，LIAO Yan-song，LU De-ping，LIU Jin，CHEN Zhi-bao，WEI Shi-yong，
HCF propagation with unilateral initial crack in 304 stainless steel piece by XFEM
In order to investigate the fatigue life of micro crack metal with low stress level cyclic loadings，an unilateral fatigue crack propagation of 304 stainless steel piece was researched with Paris criterion and extended finite element method （XFEM） based crack tip singularity. And the crack propagation with high cycle stress was analyzed by experiment and numerical method separately. Result shows that the whole cycle life of this sample is about 1.18 million times. The simulated values of propagation velocity are in good agreement with that of experimented values. The nonlinear fitting degree in whole areas between numerical solution by XFEM and analytical solution by stress intensity function （SIF） is very well. But the fitting degree of[?K]value in III area is reduced for the reason of stress intensity factor in crack tip operational instability enlarged with the crack expanding.
2018 Vol. 53 (9): 63-68 [
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JIN Guo-zhong，，PEI He-zhong，LIU Zhen-bao，LIANG Jian-xiong，WANG Xiao-hui，
Effect of mass percent of chromium on microstructure and properties of ultra high strength stainless steel
The effect of mass percent of Cr on the mechanical properties and microstructure of a new type of ultra strength stainless steel with Cr-Ni-Mo-Co system was studied. The results show that the increase of mass percent of Cr leads to the [Ms]point drop，which results in the increase of austenite mass percent in steel and restrains the precipitation of the Laves phase，resulting in a decrease in the yield strength of the steel. The test steel with 9.5%wt Cr quenched at 1 100 ℃ for 1 h and then refrigerated at －73 ℃ for 8 h. After aging at 540 ℃ for 4 h，the ultimate tensile strength of the steel up to 2 256 MPa. At this time，the intermetallic Laves phase of 5-10 nm was dispersed in the lath martensitic，that the strength reaches the highest value. This study provides basic experimental data for the development of a new type of 2.2 GPa-grade stainless steel materials which has broad applications in aerospace and aerospace fields.
2018 Vol. 53 (9): 69-73 [
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ZHAO Hong-yu，，LIU Rong-pei，WANG Chang-jun，LIANG Jian-xiong，HU Jia-qi
Hot deformation behavior and energy dissipation diagram of 9Ni martensite stainless steel
In order to study the hot deformation behavior of 9Ni martensite stainless steel，the thermal deformation test for the sampling of 9Ni steel forgings with[?400 mm]large sizes was carried out. The Gleeble-1500 thermal simulator was used to select the engineering strain 60%，the deformation temperature was 950-1 200 ℃，and the strain rate was 0.01-5 s－1. And the true stress-strain curves under different deformation processes were drawn. The constitutive equation of 9Ni steel was constructed by introducing Zener-Hollomon parameters. The relative error of this constitutive equation model was only 0.03%-0.42%，and had good goodness of fit. The energy dissipation diagram of 9Ni steel under different strain was drawn，and the optimum heat processing interval of large forgings of 9Ni steel was established with the microstructure after deformation. The temperature was at 1 100-1 150 ℃，and the strain rate was 0.1-0.3 s－1.
2018 Vol. 53 (9): 74-79 [
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ZHANG Yong，ZHANG Xiao-yue
Design optimization of convection plate at bottom of bell type annealing furnace
In order to reduce the purchase cost of convection plate and achieve the purpose of saving energy and reducing consumption，based on the using actuality，the manufacturing cost，the rolling steel coil end strip overflow size of the convection plate at the bottom of the bell type annealing furnace，the grooving process was performed in the proper place on the upper and lower end face of the convection plate at the bottom，and the appropriate manufacturing materials was chosen to meet the yield strength. This approach can decreases the annealing coil stacking overflow wounded volume ratio by 15.18%，the weld volume rate by 31.55%，and the single convection plate material cost by 82.22%. The decrease of the convection disc weight enable the lifting energy consumption reduction of 9%. Achieved a unified convection disk size specifications, and different annealing furnace types are common. Achieved the goal of reducing the volume rate of steel roll wounds, reducing the cost of making convection trays, saving hoisting energy, and improving the operating rate of heat treatment units.
2018 Vol. 53 (9): 80-86 [
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87
XIA Tian，XIANG Zhi-dong，HE Zhu，HU Shou-tian，LUO Zhong-han
Numerical simulation and analysis of temperature field for annular furnace
In order to improve the high temperature annealing process of oriented silicon steel，the heat transfer process in the annular furnace was studied by a simulation analysis approach. Through the analysis about the furnace structure and the working conditions，the model was simplified appropriately. The numerical model of the temperature field of the oriented silicon steel in high temperature annealing process was built. The temperature feature of stainless cover was concluded for different nozzle working conditions. The result of the calculation showed that when the burners were out of work，the temperature of the flue gas declined quickly along the flow direction. Moreover，when the burners were working with high power，the furnace temperature raised obviously. The high temperature region appeared in the center of the furnace whose temperature could be higher than the average value above 100 ℃. The heat transfer efficiency of radiation and convection in the furnace was high，and the maximum difference of the cover was within 30 ℃. The area of cover with unstable temperature cannot influence the coil directly. Thus，it can be considered that the temperature of the cover was well-distributed. The average error between the simulation temperature and the measurement temperature was about 15 ℃，and it declined to less than 10 ℃ after 7 h annealing process.
2018 Vol. 53 (9): 87-92 [
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