钢铁研究学报(英文版)
 
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2012年 19卷 7期
刊出日期:2012-07-15

材料
工艺
   
工艺
1 WU Tong,CHENG Su-sen
Model of Forming-Accretion on Blast Furnace Copper Stave and Industrial Application
Copper staves have been equipped on nearly all of BF (blast furnaces) with volume over than 1000 m3 in China since their introduction from abroad about more than 10 years ago. Because of short application and lack of experience, phenomena of thickened or naked of copper stave happen occasionally which influence production severely. So it is important to study the model of forming-accretion on BF copper stave and realize real-time monitoring of forming-accretion on different copper staves. Therefore, mathematic model of calculating accretion thickness by heat flow of BF is proposed, and the calculated results indicate that accretion thickness could be kept at a reasonable range of around 50 mm by controlling heat flux around 22.0 kW/m2. The monitoring program based on the model was applied to a certain BF in China successfully, and it is found that slip of BF near the inner wall is one of most important reasons that cause fluctuation of accretion thickness. During the period of scheduled maintenance of the certain BF, the thickness of accretion measured through the static pressure holes is in good accordance with the value calculated by the monitoring program, so the results calculated by the monitoring program can be used to guide industrial production.
2012 Vol. 19 (7): 1-5 [摘要] ( 1754 ) [HTML 0KB] [PDF 0KB] ( 36 )
6 ZU Ling-yu,MENG Hong-ji,XIE Zhi
A Compensation Model of Continuous Temperature Measurement for Molten Steel in Tundish
A compensation model has been proposed to reduce errors caused by the immersion depth of the sensor and the time lag of continuous temperature measurement for molten steel in tundish, which is based on the limited data fitting method and data fusion technology. According to the heat transfer analysis of sensor, the thermal model has been bulit to determine the temperature variation function.The parameters of the compensation model are recognized by generic algorithm, which combines the determine function, the molten steel mass in the ladle and pouring time. The processing of error compensation is divided into three stages: tracking, holding and compensation. When the processing is stable, the measured temperature error is small, and the measured temperature is regarded as accurate value and tracked. For the end of pouring stage of the ladle, the temperature error is caused by the immersion depth of the sensor, and the measured temperature before sharp decreasing is considered as real temperature and held. For the temperature increasing stage after ladle changed, the measured temperature is compensated online.The application results show that the error between the compensation temperatures and the actual ones have been decreased to ±2 ℃, and the time lag could be shortened from 3-5 min to 40 s by applying this model.
2012 Vol. 19 (7): 6-11 [摘要] ( 1784 ) [HTML 0KB] [PDF 0KB] ( 43 )
12 QU Tian-peng,LIU Cheng-jun,JIANG Mao-fa
Numerical Simulation for Effect of Inlet Cooling Rate on Fluid Flow and Temperature Distribution in Tundish
The fluid flow in tundish is a non-isothermal process and the temperature variation of stream from teeming ladle dominates the fluid flow and thermal distribution in tundish. A numerical model was established to investigate the effect of inlet cooling rate on fluid flow and temperature distribution in tundish based on a FTSC (Flexible Thin Slab Casting) tundish. The inlet cooling rate varies from 0.5 to 0.25 ℃/min. Under the present calculation conditions, the following conclusions were made. When the stream temperature from teeming ladle drops seriously (for inlet cooling rate of 0.5 ℃/min), there is a “backward flow” at the coming end of casting. The horizontal flow along the free surface turns to flow along the bottom of tundish. The bottom flow shortens the fluid flow route in tundish and deteriorates the removal effect of nonmetallic inclusions from molten steel. Nevertheless, when the inlet cooling rate decreases to 0.25 ℃/min, the horizontal flow is sustained during the whole casting period. The present research provides theoretical directions for temperature control in teeming ladle and continuous casting tundish during production of advanced steels.
2012 Vol. 19 (7): 12-19 [摘要] ( 1736 ) [HTML 0KB] [PDF 0KB] ( 24 )
20 WU Wei,MENG Hua-dong,LIU Liu,YUAN Tian-xiang,BAI Yan-jiang,YAN Zhan-hui
Slag Melting Characteristic of Slag Forming and Slag Splashing for BOF Less Slag Smelting
The slag melting characteristic of slag forming and slag splashing for 300 t BOF less slag process is researched by combining the methods of the slag chemical composition, the melting point determination and the petrographic analysis. The results show that the melting point of final slag for less slag smelting is 20 ℃ lower than that for conventional smelting. According to results of the petrographic analysis, the C3S (3CaO·SiO2) and C2S (2CaO·SiO2) content for less slag smelting are lower than those for conventional smelting, while the RO (FeO, MgO, MnO, etc) phase and C4AF (4CaO·Al2O3·Fe2O3) phase are higher than those for conventional smelting. According to results of the chemical analysis, the (CaO) content and slag basicity for less slag smelting are higher than those for conventional smelting, while (FeO) and (MgO) content in slag for less slag smelting are almost equal to those for conventional smelting. The reason why slag melting point for less slag smelting is lower than that for conventional smelting is that the quantity of added fluorite for less slag smelting is more than that for conventional smelting. According to the analysis results the slag melting point is determined by the C3S, C2S, RO phase and C4AF content. According to the results of slag melting characteristic before and after slag splashing for less slag smelting, the present adjusting slag process has little effect. It is important to adjust the composition of BOF final slag. The (FeO) content in slag is to be reduced at the slag splashing and adjusting slag process for less slag smelting.
2012 Vol. 19 (7): 20-25 [摘要] ( 1764 ) [HTML 0KB] [PDF 0KB] ( 18 )
26 XU Ji-fang,ZHANG Jie-yu,JIE Chang,TANG Lei,CHOU Kuo-chih,
Measuring and Modeling of Density for Selected CaO-MgO-Al2O3-SiO2 Slag With Low Silica
The densities of the selected quaternary CaO-MgO-Al2O3-SiO2 slag with low silica were measured by the Archimedean method in a wide temperature range from 1773 to 1873 K. Nine different slag compositions were chosen based on three different levels of CaO content and three different levels of SiO2 content. wMgO was equal to 7.0%. wCaO were varied from 40.04% to 50.64%, for wSiO2=10.25%-20.70%. The effects of temperature, SiO2 content and optical basicity were studied. It is shown that density decreases approximately linearly with an increase in temperature. Under the same CaO content, the density decreases with increasing of SiO2 content, and increases with optical basicity increasing. Based on the experimental data as the boundary of the homogenous phase region predicated by FACTSAGE software, the mass triangle model is used to calculate the density of selected limited homogenous phase region. The results showed that the mass triangle model works well.
2012 Vol. 19 (7): 26-32 [摘要] ( 1991 ) [HTML 0KB] [PDF 0KB] ( 47 )
33 HOU Yan-qing,XIE Gang,TAO Dong-ping,LI Rong-xing,YU Xiao-hua
Activity Calculation by Application of Sub-Regular Solution Model in Binary Oxide Systems
To confirm sub-regular solution model valid for predicting the activity of component in binary oxide systems, seven systems in the whole concentration and twelve systems presenting saturation concentration have been studied. The total average relative errors of component 1 and 2 are 3.2% and 4.1% respectively by application of the sub-regular solution model into the systems within the whole concentration. However, the total average relative errors are 16% and 1088% in the systems presenting saturation concentration. The results show that sub-regular solution model is not good for predicting the systems presenting saturation concentration, especially for the systems containing acidic or neutral oxide. The reason may be that the influence of the two types of oxide on the configuration is greater in binary oxide systems. These oxides can be present in the form of complex anion partly, Si-O, Al-O, Ti-O and so on, for example (SiO4)4-. That is contrary to sub-regular solution model which is supposed that the oxide systems consist of cation and O2-. But compared with regular solution model and quasi-regular solution model, sub-regular solution model is closer to the characteristics of actual solution and the calculated results are superior.
2012 Vol. 19 (7): 33-38 [摘要] ( 1730 ) [HTML 0KB] [PDF 0KB] ( 13 )
39 LONG Xiao,HE Sheng-ping,XU Jian-fei,HUO Xu-ling,WANG Qian
Properties of High Basicity Mold Fluxes for Peritectic Steel Slab Casting
In high speed continuous casting of peritectic steel slabs, mold fluxes with high basicity are required for less surface defect product. However, the basicity of remaining liquid slag film tends to decrease in casting process because of the crystallization of 3CaO·2SiO2·CaF2. Thus, a way is put forward to improve mold fluxes′ properties by raising the original basicity. In order to confirm the possibility of this method, the effect of rising original basicity on the properties of mold fluxes is discussed. Properties of high fluorine based mold fluxes with different basicities and contents of CaF2, Na2O, and MgO were measured, respectively. Then, properties of higher basicity mold fluxes were discussed and compared with traditional ones. The results show that increasing the basicity index can improve the melting and flow property of mold fluxes. With the increasing basicity, crystallization rate of mold fluxes increases obviously and crystallization temperature tends to decrease when the basicity exceeds 1.35. The method presented before is proved as a potential way to resolve the contradiction between horizontal heat transfer controlling and solidified shell lubricating for peritectic steel slab casting. But further study on improving the flow property of liquid slag is needed. This work can be used to guide mold fluxes design for high speed continuous casting of peritectic steel slabs.
2012 Vol. 19 (7): 39-45 [摘要] ( 1890 ) [HTML 0KB] [PDF 0KB] ( 27 )
材料
46 Karin Gong,LUO He-li,ZHOU Zhi-feng,TIAN Zhi-ling,Lars Nyborg,LI Chang-hai
Wear Evaluation on Ni3Al/MnS Composite Related to Metallurgical Processes
Iron alloyed Ni3Al with composition of Ni-18.8Al-10.7Fe-0.5Mn-0.5Ti-0.2B in atom percent (NAC alloy) showed attractive tribological properties under unlubrication condition at room temperature. The alloy was prepared by hot isostatic pressing (HIP) process. The wear properties were associated with its intrinsic deformation mechanism. Unfortunately, the single phase NAC-alloy worked inadequately with its counterpart disk, and also showed a poor machinability. In the present work, NAC-alloy matrix composite with 6% (volume percent) MnS particle addition was studied to improve its wear behaviors and performance on machining. Two metallurgical processes of HIP and vacuum casting were applied to produce the testing materials. Pin-on-disk (POD) measurements were carried out at room temperature. A commercial vermicular graphite cast iron was selected as a reference material. The counterpart disk was made of a grey cast iron as liner material in ship engines. The contact pressures of 2.83 MPa and 5.66 MPa were normally applied in the tests. The investigation indicated that MnS particle addition in the NAC-alloy composites functions as an effective solid lubricant, and improved wear properties and machinability of the materials. Obviously, as-cast NAC-alloy with in-situ formed MnS-phase was working more effectively with the counterpart, comparing to the HIPed NAC-alloy composite with MnS particles. At the high contact pressure of 5.66 MPa, the specific wear rate of the as-cast NAC-alloy composite was high. The phenomenon of the negative effect is mostly due to the brittle second NiAl phase as evidenced in the microstructure analysis.
2012 Vol. 19 (7): 46-54 [摘要] ( 1658 ) [HTML 0KB] [PDF 0KB] ( 46 )
55 HU Zheng-fei,WANG Qi-jiang,ZHANG Bin
Microstructure Evolution in 9Cr Martensitic Steel During Long-Term Creep at 650 ℃
Standardarized creep and rupture strength tests were conducted for commercial T91 martensitic heat-resistant steel at 650 ℃ and corresponding microstructure was characterized by BSED, TEM and EDS. The martensitic microstructure degenerated seriously during creep exposure, including martensitic substructure recovering, carbides coarsening, dissolving and precipitating. EDS analysis shows that the M23C6 carbides in different morphologies have dissimilar compositions. The rod/sheet like M23C6 particles within the matrix contain more additions, which might precipitate in situ while fine MX particles were re-solving. The high content of silicon in these rod/sheet like M23C6 carbides is probably related to self diffusion coefficient increasing for the exposed condition at 650 ℃ close to Curie temperature Tc. For those reasons, martensite substructure becomes unstable, and microstructure evolution is accelerated and leads to creep strength deteriorating severely.
2012 Vol. 19 (7): 55-59 [摘要] ( 1776 ) [HTML 0KB] [PDF 0KB] ( 27 )
60 MA You-ping,LI Xiu-lan,WANG Cheng-hui,LU Lu
Microstructure and Impact Wear Resistance of TiN Reinforced High Manganese Steel Matrix
A high-manganese austenitic steel matrix (Mn13) composite reinforced with TiN ceramic particles was synthesized by means of Vacuum-Evaporation Pattern Casting (V-EPC). The composite microstructure and interface bonding of TiN/matrix were analyzed utilizing optical microscope (OM) and X-ray diffraction (XRD). The effects of different volume fraction of TiN on impact wear resistance were evaluated by MLD-10 impact wear test.The results showed that TiN was evenly distributed in composite layer and had a good interface bonding with matrix when the volume fractions of TiN were 27% and 36%, respectively. However, cast defects and TiN agglomeration occurred when the TiN volume fraction increased to 48%. Compared with high-manganese austenitic steel (Mn13), the impact wear resistance of the TiN-reinforced composite is better. In small impact load conditions, composite layer can effectively resist abrasives wear and TiN particles played an important role in determining impact wear resistance of composite layer. In large impact load, the synergistic roles of spalling of TiN particles and the increase of work hardening of Mn13 based material are responsible for impact wear resistance.
2012 Vol. 19 (7): 60-65 [摘要] ( 1731 ) [HTML 0KB] [PDF 0KB] ( 23 )
66 SHI Zhen-xue,LI Jia-rong,LIU Shi-zhong
Effect of Hf on Stress Rupture Properties of DD6 Single Crystal Superalloy After Long Term Aging
The specimens of the second generation single crystal superalloy DD6 with different Hf contents were prepared in the directionally solidified furnace with a high temperature gradient. The long term aging of the specimens after full heat treatment was performed at 1040 ℃ for 800 h. The effect of Hf on the microstructure and stress rupture properties under 980 ℃/250 MPa of the alloy after long term aging was investigated. The results show that the γ′ coarsening and rafting and no topologically close packed phase (TCP) are observed in the microstructures of DD6 alloy with different Hf contents after aged at 1040 ℃ for 800 h. It indicates that DD6 alloy with different Hf contents all possesses good microstructure stability. With increasing Hf content the rupture life after long term aging turns shorter and the elongation represents the increasing first and decreasing afterwards. The fracture mechanism of the alloy with different Hf contents at 980 ℃/250 MPa all shows dimple model. The influence of the microstructures on the stress rupture properties of the alloy is also discussed.
2012 Vol. 19 (7): 66-70 [摘要] ( 1707 ) [HTML 0KB] [PDF 0KB] ( 31 )
71 I K Lee,C L Chung,Y T Lee,Y T Chien
Effect of Thermal Refining on Mechanical Properties of Annealed SAE 4130 by Multilayer GTAW
During the first welding process in manufacturing a precise seam container, the steel material must first undergo a full annealing treatment. Multilayer welding operations are conducted and then applied with refining treatment to obtain the goal by hardening. The influence of thermal refining on mechanical properties of annealed SAE 4130 by multilayer GTAW (gas tungsten arc welding) was discussed. The AW (annealing+welding) and AWST (annealing+welding+solution+tempering) occurred with a minimum hardness value at GGHAZ (grain growth heat affected zone) due to coarse grain growth; the hardness occurred with sudden drops between the multilayer welding, but was still larger than the minimum value at HAZ (heat affected zone). The welded joint efficiency of the AWST was 89.9%, with the elongation reduced to 77.2% of AST (annealing+solution+tempering). The cross section of the tensile samples both appeared with a uniform dimple-shaped structure, and however the necking for AST was greater than that for AWST. The impact value for AWST was 166.5% of AST. Moreover, from microstructure observations, it was found that AWST had a greater tendency to ductile failure than AST. These results can be inferred: the process of steady pressure and the initial position of the precision tube breakage HAZ. However, when stress occurs instantly, HAZ can absorb more energy, therefore the initial damage does not occur.
2012 Vol. 19 (7): 71-78 [摘要] ( 1676 ) [HTML 0KB] [PDF 0KB] ( 26 )
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