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2016 Vol. 51 No. 9
Published: 2016-09-15
1
CAO Wen-quan，XU Hai-feng，，ZHANG Ming-da，DONG Han，WENG Yu-qing
Research and development of a new hot rolled laminated structure
In view of energy shortage and high safety requirements， steels with low density， high strength and high toughness have become a hot research topic in material science. A large number of reports show that the Al and other elements alloying can significantly reduce the steel density， and the laminated composite structure greatly improves the toughness of the steel. In this study， based on the introduction of high strength and high toughness steel with equiaxed grains，steel with layered composite and low-density steel at home and abroad，the idea of low density low to medium-alloy design（4%-12%） of Fe-Al-Mn-C dual phase steel and the micro-laminated control by grain shape pancaking of both high temperature delta-ferrite phase and austenite phase during hot rolling process is proposed， which makes it possible to obtain a alternatively arranged micro-laminated composite steel with low density， high strength and high toughness. It is proved that it is feasible to obtain the dual phase steel with low density （6.5-7.5 g/cm3）， micro-laminated， high strength （1 000-1 500 MPa） and high toughness （200-400 J）， which breaks the limitation of toughening mechanism of conventional steel with equiaxial grain structure and opens a new research and development approach for the high strength and high toughness steel. At the end of this paper， a thorough study on the low density and micro-laminated dual phase steel is proposed to understand the relationship between chemical composition， parameters of the micro-laminated structure and the properties of strength and toughness， and to explore the strengthening and toughening mechanism of the new designed low density and micro-laminated dual phase steel， which would indeed open an innovative direction for future research and development on the low density， high strength and high toughness steels.
2016 Vol. 51 (9): 1-10 [
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11
LIU Jie，ZHANG Hong-yu，ZHOU Ming-shun，ZHAI Li-wei，ZHANG Hui，XU Li-bing
Rational burden structure of blast furnace based on softening and melting property
In order to fully understand the softening-meting properties of sintering ore with different basicity， ration of natural lump ore， and BF burden structures in Ansteel and find the methods used to estimate BF burden structures， some investigations were made systematically in laboratory on the metallurgical performance of sintering ore with different basicity. In addition， the high temperature performance of combined BF burdens forming by the sinter with various basicity， pellet and natural lump ores， were also discussed. The results show that the mineral sinter compositions became more rational with the increase of basicity， hence， the reducibility and the reduction degradation were improved. When the basicity was in the range of 1.90-2.05， good softening-melting performance could be obtained just with individual sinter ore. As the basicity increased to 1.95-2.15， the penetrability was better. When the basicity of the combination of sinter and pellet was 1.90-2.15， the softening and melting zones became narrow and property with low[S]was realized. With the addition of natural lump ore， the softening zone widened while the melting zone became narrow， the comprehensive performance was improved. Based on the research results， an assessment index for Ansteel raw material was obtained for the interactive reaction among burdens. The index can be used to assess the reasonableness of BF burden structure. Considering the reactivity index and the economic cost， the reasonable proportion of lump ores in blast furnace needs to be controlled within 15%-20%.
2016 Vol. 51 (9): 11-15 [
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16
YANG Shuang-ping，GUO Shuan-quan，ZHANG Pan-hui，ZHOU Jiang-feng，WANG Miao
Influence of semi-coke used as sintering fuel on metallurgical properties of sinter
Semi-coke used as sintering fuel was studied through the sintering cup experiment， sinter load softening experiments， sinter reduction test and low-temperature sinter reduction powder experiment. Emphasis was mainly focused on the influence of semi-coke substitution ratio on sinter metallurgical properties. The result shows that， the addition of semi-coke and the increase of basicity do not have obvious negative impact on the sinter yield， grade， the drum index and grain size. When the content of semi-coke is 30% and the basicity is 1.82， the drum strength as well as the softening property of sinter can improve. In addition， with the increase of semi-coke replacement ratio， the sinter basicity increases， leading to a decrease of the FeO content in sinter which is helpful for the sinter reducibility and low-temperature reduction disintegration. Considering the roles of semi-coke and alkalinity in sintering process and the influence of sinter metallurgical properties， the application of semi-coke as fuel in sintering process is feasible， and the optimum condition is 30% addition of semi-coke and the basicity of 1.82.
2016 Vol. 51 (9): 16-21 [
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ZHANG Jian-liang，GUO Jian，WANG Guang-wei，ZHANG Lu-ming，XU Tao，ZHENG Chang-le
Effect of iron ore fines addition on microstructure and properties of iron-coke
In order to clarify the effect of iron ore fines which were added during coking process on the coke properties， three different iron ore blend ratios (0，5% and 10%) were used to make iron-coke. I-type drum、thermogravimetric analyser、SEM、XRD and optical microscope were used to investigate the properties of iron-coke， such as strength， reactivity， microstructure， crystallite structure and optical texture. Moreover， the method of Coats-Redfern was used to calculate the kinetics parameters of the gasification reaction. The results showed that it could increase the cold strength and reactivity of iron-coke by adding iron ore fines into gas coal. With the increase of iron ore blend ratio， the stacking height[Lc]value of iron-coke and the gphitization degree decreased. The pore size of iron-coke became smaller as well. The density of Fe atom attaching to the surface of the pore increased， and a piece of iron region was found. The isotropic and mosaic structure in coke was reduced， while the residual carbon structure was increased. According to the kinetics analysis， the activation energy of iron-coke with 0，5% and 10% iron ore fines blend ratio was 228.4，235.5 and 256.7 kJ/mol， respectively. Meanwhile， it was found that the apparent activation energy and pre-exponential factor had a kinetic compensation effect.
2016 Vol. 51 (9): 22-29 [
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30
ZHANG Xue-wei，ZHANG Li-feng，YANG Wen，DONG Yuan-chi，LI Yang-zhou
Thermodynamics and dynamics of MnS inclusions precipitation during solidification process in heavy rail steels
The three-dimensional morphologies of MnS inclusions in continuous casting blooms and rolled rails of U75V steel were obtained by electrolytic extraction method using non-aqueous electrolytes combined with SEM method. However， MnS was elongated along the rolling direction during rolling process， and the morphology of MnS inclusions presents an elongated shape in rail. Precipitation of MnS inclusions was studied on the basis of thermodynamics and kinetics model in heavy rail steels， and the amount of segregation behavior of[w([Mn])]and[w([S])]elements in molten steel was quantified during solidification. The calculated results show that MnS inclusions were generated due to the initial concentration product of manganese and sulfur equaled to the equilibrium concentration product， i.e.， MnS inclusions started to precipitate in the solid which fraction was 0.94. In comparison， the thermodynamic calculation results were in good agreement with that of the results by Thermo-Calc and FactSage6.4. Effect of the initial concentration of Mn and S in molten steel and cooling rate during solidification on the amount of MnS inclusions was calculated using micro-segregation model. In addition， the size of MnS inclusions decreased obviously with increasing cooling rate through the dynamic calculation. Therefore， the influences of the content of[w([Mn])]and[w([S])]in molten steel and the cooling rate on the characteristics of MnS inclusions in heavy rail steel were analyzed， including precipitation size， time and amount of the MnS particles. Thus， it would be helpful for decreasing detrimental factors on the properties of steel.
2016 Vol. 51 (9): 30-39 [
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40
LI Zhi-zheng，，ZHU Rong，LIU Run-zao，WANG Xue-liang
Comparison of smelting effects by bottom blowing different gases
Based on thermodynamics and kinetics of bottom blowing during the steelmaking process， the smelting effects of bottom blowing with O2， CO2， Ar and N2 were studied. It is found that the bottom blowing Ar or N2 does not react with the elements of molten pool. The temperature of liquid steel basically remains unchanged， while the nitrogen content in liquid steel is high. However， when the bottom blowing gas is O2 or CO2， the decarburization rate and the content of nitrogen and hydrogen in liquid steel are basically the same， the temperature of molten pool is raised by 162 and 45 ℃， respectively. Compared with O2， if CO2 is injected from the bottom of furnace， the amount of steelmaking dust will be decreased，[w((TFe))]in slag will be decreased by 2.50%，[w((O))]will be decreased by 90.2%.
2016 Vol. 51 (9): 40-45 [
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JIA Ji-xiang，GUO Qing-tao，LIAO Xiang-wei，LI De-gang，NI Chong-yi，PENG Chun-lin
Unpolluted deoxidization technology with applied electric field between metal and slag
In order to explore the influence of various applied electric fields and electrodes on the unpolluted deoxidization of molten steel， a new deoxidization system for commercial experiment and numerical simulation has been designed and fabricated based on the mechanism of electrochemical reaction. And the unpolluted deoxidization technique has been studied when a DC field was applied between the metal and slag. The results show that electrochemical deoxidization can be carried out effectively with the application of electric field at the interface between metal and slag. The maximum deoxidization rate could reach 0.001 86%/min. Both increasing the mass transfer coefficient of oxygen ions and the reaction area of the metal and the slag could increase the oxygen ion current between the steel and slag，so the deoxidization rate could be improved. This technology is new kind of green and environmental steel refining process，which has broad application prospects.
2016 Vol. 51 (9): 46-50 [
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51
WANG Dong-cheng，，ZHANG Wei，WANG Zhi-jie，LIU Hong-min，
Fast shape prediction method for six-high cold rolling mill
Compared with the shape prediction of the four-high mill，there are more unknowns obout the six-high mill，and the calculation speed is slower. Therefore，the model coupling method is extended to the six-high mill，and the linear equations of the strip plastic deformation models and the elastic deformation model of roll system are established. Considering the input parameters of flatness problems usually does not include the no-load roll gap value，a new linear equation is proposed according to the average thickness of the strip at exit. The value of the no-load roll gap is incorporated into the unknown quantity. Therefore，the applicability of the model coupling method is improved. Two calculation examples show that，when applied to six-high mill，the calculation results of model coupling method are in well agreement with the calculation results of relaxation factor method，but it can increase the calculation speed by about 100 times.
2016 Vol. 51 (9): 51-56 [
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57
XU Xiu-mei，XIE Peng-peng，XIAO Hong，XIE Hong-biao，ZHANG Shao-kun
Effect of hot-rolling process on properties of stainless steel/iron scrap clad plate
In order to study the properties of stainless steel and iron scrap， the stainless steel/iron scrap clad plate was hot-rolled by using solid metal recycling concept.Through metallographic observation to analyze the interface between stainless and iron scrap and shearing and tensile experiments to test the performance of the composite plate，the current study investigated the effect of hot-rolling process on the properties of stainless steel/iron scrap clad plate. The results show that the reason why the large single pass quantity does not make two metals be composite is that the high pressure cannot completely make the holes among iron scraps disappear. The iron scraps still have flowing space in spread direction. But when the single pass reduction was smaller and the accumulated amount reached 17 mm， its shear strength was at 225 MPa，which reaches the national standard. Therefore，a certain accumulated amount is one of the key factors affecting the composite of stainless steel and iron. Adding graphite powder in the iron scraps can improve the mechanical properties of materials and improve the tensile and shear strength of the after- test sample，but the elongation will be reduced.
2016 Vol. 51 (9): 57-62 [
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63
LI Hong-bin ， ，YU En-lin
Investigation on microstructure evolution of medium carbon steel during warm deformation
The warm compression test for medium carbon steel was carried out on Gleeble-3500 thermal-simulation machine. The effects of deformation temperature (550， 600， 650， 700 ℃) and strain rate (0.001， 0.01， 0.1， 1， 10 s－1) on the microstructure evolution were studied. The processing map was established to explore the best parameter combination to generate the evenly distributed and fine cementite particles on the ferrite matrix. The results show that during the warm deformation， dynamic spheroidization of lamellar cementite and ferrite dynamic recrystallization occurred， and the flow stress was influenced by the evolution of microstructure. According to the processing map， the best processing parameter that the temperature range of 630-700 ℃ and the strain of 0.30-10 and 0.001-0.007 s－1 could be obtained. The composite microstructure with ultrafine ferrite grains and uniform distribution of cementite particle was obtained.
2016 Vol. 51 (9): 63-69 [
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70
LI Jie，DU Feng-shan，LIANG Yang，WU Shuo，TAN Tian-yu
Hydrogen diffusion calculation experiment of sheet metal
The materials used in the hydrogen diffusion calculation experiments is rolled sheet of 40Cr and 4Cr13. CS Electrochemical Workstation is a type of laboratory apparatus which is applicable for diffusing hydrogen atoms， based on the theory of electrochemical methods to let the hydrogen atoms diffuse into the sheet. The preliminary of experiments proceeded with polishing specimens surface， nickel preplating treatment and electroless nickel plating on the rolled sheet， then the diffusion coefficients of hydrogen atoms were tested out and calculated， finally the diffusion coefficients of hydrogen atoms in the rolled sheet of 40Cr were obtained. This experiments can be suit for measuring the hydrogen atoms diffusion coefficient in various metal materials. It plays an important role to quantitativelycalculate the content of the hydrogen in the steel materials. By the comparison of composition and diffusion coefficient of two kinds of material， the effect of metal alloy element content on the hydrogen diffusion in the metal needs further study.
2016 Vol. 51 (9): 70-75 [
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QIAN Guo-yu，QU Zhi-dong，CHENG Guo-guang，LI Liu-yi，，ZHANG Jian-guo，LI Jing-yu
Effect of Al in FeSi alloy on continuous casting and surface defect of stainless steel hot-rolled sheet
In response to the problem about Al2O3 inclusion and surface delamination defects in the 304 stainless steel hot-rolled sheet under the conditions of Si deoxidization process， the influence of Al content in FeSi alloy on the formation of Al2O3 and its effect on the continuous casting mold fluxes and the surface delamination defects of hot-rolled sheet were studied by electrolysis for slab， sampling of hot-rolled sheet， analysis of scanning electron microscopy (SEM) and calculation of FactSage software. The results showed that the main step to form Al2O3 inclusions was the deoxidization process with FeSi alloy at the beginning of the GOR reduction in the whole process of smelting. The maximum value of Al content in FeSi alloy was obtained by the calculation of FactSage software for suppressing the formation of Al2O3. Conclusions were obtained through the calculation and industrial tests that the generation of Al2O3 could be occurred as the Al content in FeSi alloy was more than 1.8%， which led to the formation of massive inclusions with high melting point and high viscosity that was the mixture of Al2O3 and mould fluxes when the Al2O3 floated into mould fluxes. Subsequently， these massive inclusions could result the surface delamination defects in the process of hot rolled if they were entrapped by the initial solidified shell. However， Al2O3 was difficult to form when the Al content in FeSi alloy was lower than 1.5%， so such surface delamination defects were effectively suppressed in the hot-rolled sheet.
2016 Vol. 51 (9): 76-81 [
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LIANG Jian-xiong，YONG Qi-long，ZHANG Liang，WANG Chang-jun
Hot deformation behavior and its processing map of 1Cr17Ni1 duplex stainless steel
The hot deformation behavior of the 1Cr17Ni1 martensite - ferritic duplex stainless steel at 950-1 150 ℃ with the strain rate of 0.1-10 s－1 on a Gleeble-3800 simulated machine was investigated. The constitutive equation was constructed by using hyperbolic sine function to obtain the apparent deformation activation energy which was 391.586 kJ/mol， and based on dynamic material model the hot processing map of 1Cr17Ni1 steel under different strain was made. At lower deformation temperature， the dynamic recovery and dynamic recrystallization occurred for the tissue morphology. At the high temperature， only the dynamic recovery occured. An optimum processing parameters of hot deformation for this steel can also be obtained by the the processing map and deformation， in which the hot working temperature range was 950-1 000 ℃， and the thermal deformation rate range was 0.1-0.3 and 5-10 s－1.
2016 Vol. 51 (9): 82-89 [
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90
LIU Yang-bo，TONG Qian，SUN Qi-song，CHAO Yue-lin
Thermal simulation on effect of water cooling process on microstructures and hardness of 20CrMnTiH steel
Reducing the hardness of Bars is conductive to further processing. Effects of finishing rolling temperature， water cooling and cooling rate at cooling bed on the microstructures and the hardness of 20CrMnTiH small bars were investigated by using a thermal simulator. Without water cooling，the ferrite proportions increase with the decreasing of finishing rolling temperature and cooling rate at the cooling bed，while it is exactly the opposite for the bainite proportions. Thus，the hardness of bars decreases with the decreasing of finishing rolling temperature and cooling rate at the cooling bed. The ferrite proportions are increased，and the bainite proportions are decreased by water cooling. Therefore the hardness of bars is decreased significantly. The hardness of water cooling bar is less than 217HBW， which satisfies the hardness requirement for the annealing or high temperature tempering materials.
2016 Vol. 51 (9): 90-95 [
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96
JIN Yu-tao，WANG Wen-gang，WEN Yan
Ultra-filtration technology on treatment of cold-rolled oily water
Cold rolling wastewater treatment most difficult in the metallurgical sewage wastewater, Its water quality complex composition, high concentration, stable, difficult degradation, water quality varies significantly, especially oil pollution of complex components of high concentration of oil wastewater, Need to use technology to achieve outstanding specific standard treatment, in order to achieve green development of metallurgical processes. Introduces the ultra filtration oil removal technology applied to oil emulsion wastewater treatment in a cold-rolled. infinite ceramic ultra filtration is adopted to improve the oil removal in this paper， With the aid of ultra filtration loops，reduce the oil content of wastewater. Ultra filtration water production oil in 20 mg/L， oil removal rate is more than 96%， operation cycle can be up to 10 days， the overall effect is better. The operation control of the system， chemical cleaning and membrane pollution prevention and control are studied， find out targeted operation control parameters and membrane pollution prevention and control measures， and realization of ultra filtration in the cold rolling thick oil wastewater in a stable and good application effect.
2016 Vol. 51 (9): 96-99 [
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