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	2022 Vol. 57 No. 3
	Published: 2022-03-15



	Technical Reviews Raw Material and Ironmaking Steelmaking Metal Forming Materials Environmental Protection and Energy

Technical Reviews

	1	ZHANG Fu-ming, XIE Jian-xin, YIN Rui-yu
		Analysis on dissipative structure of ironmaking procedure for iron and steel manufacturing process
		In order to study the essences and characteristics of the dissipation structure of iron and steel manufacturing process, the blast furnace ironmaking segment is targeted, some issues are studied and analyzed for dissipative structure optimization under the condition of multi-process cooperative dynamic operation. The ironmaking segment composed of raw material yard, coking, sintering, pelletizing and blast furnace procedures, is not only an important material/energy conversion center in the steel manufacturing process, but also the key and basic link of dynamic, orderly, coordinated and continuous operation of the whole process. The physical essence of ironmaking segment is the process that iron ore converts/transforms into high temperature hot metal, forms blast furnace gas and liquated slag, and produces a lot of residual energy and heat, under drive and function of carbon element energy flow, and through a series of heat, mass and momentum transmission as well as complex metallurgical physical and chemical reaction engineering. This complex process requires multi-process cooperative coupling, dissipative structure optimization, and dynamic and orderly operation. The connotation of dissipative structure theory, the basic conditions for formation and maintenance of dissipative structure were analyzed, and it was pointed that the ironmaking procedure of steel manufacturing process was a typical dissipative structure. The progress of function analysis optimization and engineering evolution of main unit procedures for ironmaking segment was expounded. It was indicated that the formation and development of coking, sintering, pelletizing and other unit processes were the evolution result and engineering effect of function analysis optimization, integration optimization and reconstruction optimization for modern blast furnace. The optimization objectives included improving product quality and production efficiency, reducing operation costs and energy consumption, decreasing CO₂ and pollutant emissions, and achieving ecological environment friendliness. Based on the theory of dissipative structure, the theory and methods of function analysis, dissipative structure characteristics and dissipative structure construction and optimization of main units in ironmaking segment process were promoted, and the comparative analysis and selection of unit process function, as well as selection for parameters such as ability and quantity of equipment/device were discussed. Under the guidance of dissipative structure theory and metallurgical process engineering theory, the concept design, top-level design and dynamic precision design system of Shougang Jingtang Iron and Steel Plant were constructed, the dynamic-orderly, synergetic-continuous, and dissipative construction optimized production process had been established. Production practice with reasonable dissipative structure, low material and energy dissipation, advanced production and operational indices and significant economic and social benefits, has proved that the theory has great theoretical research and promotional application value.
		2022 Vol. 57 (3): 1-9 [Abstract] ( 368 ) [HTML 1KB] [PDF 1803KB] ( 645 )

	10	SHEN Feng-man, ZHENG Ai-jun, ZHENG Hai-yan, WANG Xiao-ai, LI Yang, ZHANG Wei-ling
		Thoughts on preparation of hydrogen-based reduction gas and process of direct reduction iron
		Optimizing and improving the preparation process of hydrogen based direct reduction iron is one of the effective ways to develop and implement carbon emission reduction in China. Therefore, hydrogen-based direct reduction iron process will have great development with the promotion of “carbon emission reduction” and “carbon neutralization”. This paper discussed and analyzed the difficult problems in the process of hydrogen-based gas direct reduction of iron from three aspects: iron containing raw materials, reduction gas preparation parameter selection and energy guarantee. Especially for the selection of reduction gas preparation parameters, an innovative graphical method for determining the process parameters of hydrogen-based reduction gas was proposed. This method was used to construct the "mass and chemical balance diagram of H-C-O system" and unify the expression of reducing gas by n_H/n_C and n_O/n_C. Through the introducing of ray nH₂O/nCH₄ scale passing through CO₂ point, the nCO₂/nCH₄ scale parallel to line L₁ (nH₂O+nCH₄>0、nCO₂=0), and the straight line family of nH₂/nCO isolines at different temperatures, and using " mass and chemical equilibrium diagram of H-C-O system", the existence domain of any composition gas could be clearly expressed, that means, the n_H/n_C and n_O/n_C of any composition gas could be clearly expressed. Using this method, the addition amount of nH₂O or nCO₂ or for 1 mol CH₄ under a given nH₂/nCO can be determined. For the process of preparing hydrogen-based reducing gas by reforming natural gas or coke oven gas, the process operating parameters (such as, addition amount and ratio) for preparing hydrogen-based reducing gas with a given nH₂/nCO at a specified temperature can be easily determined by graphical method according to the gas source conditions, so as to provide a theoretical guiding basis for the selection of process parameters for preparing hydrogen-based reducing gas.
		2022 Vol. 57 (3): 10-15 [Abstract] ( 385 ) [HTML 1KB] [PDF 1221KB] ( 614 )

Raw Material and Ironmaking

	16	HUANG Jun-chen, WANG Qi, ZHANG Song
		Influence of gas non-equimolar diffusion on coke solution-loss reaction
		As an important raw material for ironmaking, coke has attracted much attention in terms of its thermal properties. The results obtained by different thermal property evaluation methods (CRI, CSR, CRR₂₅, CSR₂₅) for the same coke may be completely different, which is due to the lack of in-depth and comprehensive understanding of coke solution-loss reaction mechanism. In the process of coke solution-loss reaction, the factor of gas non-equimolar diffusion is always ignored, which leads to the deviation in understanding of coke solution-loss reaction mechanism. In order to understand the coke solution-loss reaction mechanism more clearly and comprehensively, a kinetic model considering gas non-equimolar diffusion was established.The gasification experiments of industrial coke and CO₂ with 25% solution-loss at 1 100-1 300 ℃ were carried out. The effect of gas non-equimolar diffusion on coke solution-loss reaction was explained by comparing the CO₂ effective internal diffusion coefficient, the effective area of CO₂ concentration in coke and the reaction controlling step with and without consideration of gas non-equimolar diffusion. The results show that with considering the gas non-equimolar diffusion, the CO₂ effective internal diffusion coefficient decreases and changes with temperature, reaction process and internal radius of coke. With increase of temperature, the effective area of CO₂ concentration in coke decreases, as well as the opening, area and position, and it is closer to the coke surface, meanwhile, the region of solution-loss reaction decreases. The reaction controlling step has no obvious variation trend and remains stable with the reaction process.
		2022 Vol. 57 (3): 16-26 [Abstract] ( 185 ) [HTML 1KB] [PDF 3505KB] ( 376 )

	27	WEI Ru-fei, KE Ji, LI Jia-xin, ZHENG Bao-song, LONG Hong-ming
		Gasification differences of different reactive carbons and their effects on iron ore reduction
		Coupling of pure oxygen blast furnace and coal gasification is an important way to reduce energy consumption and carbon emission in ironmaking and coal gasification process. The key to realize gas conditioning and coke ratio reduction is to study the gasification difference of different reactive carbons and its impact on iron ore reduction. The experimental studies for gasification of charcoal, semi-coke and coke and the reduction of sinter and pellet ore were carried out under condition of simulating the coupling process of oxygen blast furnace and coal gasification. The results show that the order of reactivity for three carbons with CO₂ and steam is charcoal > semi-coke > coke, the reaction starting temperatures with CO₂ are 650.0, 730.0 and 877.5 ℃,respectively, and the reaction starting temperatures with steam are 613.5, 672.0 and 841.5 ℃, respectively. The characteristic reaction temperatures of three carbons with steam are all lower than that with CO₂. The activation energies of charcoal, semi-coke and coke with CO₂ are 109.51, 119.31 and 176.84 kJ/mol, respectively, while the activation energies with steam are 167.59, 211.67 and 238.65 kJ/mol, respectively. Among the three kinds of carbons, charcoal has the best reactivity and the lowest activation energy. Addition of high reactive carbon can promote the reduction of iron ore, thus the promotive action of charcoal and semi-coke is better than that of coke. Compared with the situation that is no carbon addition, after adding the most reactive charcoal, the reduction degree of sinter and pellet increase by 13.72% and 18.37% respectively. Compared with adding coke, adding the most reactive charcoal increases the reduction degree of sinter and pellet by 2.07% and 14.98% respectively. In blast furnace, an appropriate amount of high reactive carbon can be used to replace coke, so as to reduce the coke ratio, promote the conversion of CO₂ to CO and steam to H₂ and improve the quality of gas.
		2022 Vol. 57 (3): 27-35 [Abstract] ( 173 ) [HTML 1KB] [PDF 4553KB] ( 458 )

Steelmaking

	36	CHE Zhi-chao, LIU Wei, YANG Shu-feng, LI Jing-she, LIU Chao, YUAN Hao
		Modification of sulfide inclusions in 15-5PH steel by tellurium treatment
		15-5PH precipitation-hardened stainless steel has excellent machining properties,which can be affected by inclusions in steel significantly. Long strip sulfide inclusions often lead to obvious anisotropy in mechanical properties due to the decrease of transverse performances for sulfur-containing steel during machining,which leads to material fracture failure. In order to investigate the effects of tellurium treatment on morphology,size and aspect ratio of sulfide in 15-5PH steel, high temperature test, SEM-EDS and statistical method were used in the test,and the mechanism of tellurium control on the morphology of manganese sulfide inclusions was discussed. The results show that sulfide of long strip and chain typeⅡin steel are modified into spherical MnS-MnTe and (Al-Si-O)-MnS-MnTe complex inclusions by tellurium treatment. The morphology and distribution of tellurium sulfide inclusions in steel were greatly changed. The aspect ratio of inclusions in steel decreased from 1.83 to 1.49,spheroidization rate was significantly increased,and the modification effect was obvious. When w([Te])/w([S]) in steel was 1.42,the inclusions had lower aspect ratio and smaller size, and the modification effect was the best. When w([Te])/w([S]) in steel was 2.32,large inclusions with high tellurium phase and sulfide embedded in telluride were found in the steel,and the average size of inclusions increased while the modification effect decreased. It indicates that there is an optimal amount of inclusion in tellurium treated steel,and high tellurium sulfide ratio exceeds the certain amount can not further improve the spheroidization rate. The addition of tellurium can significantly spherize sulfide inclusions in steel,reduce the aspect ratio of inclusions, improve the transverse performance and the cutting performance of steel. It can provide more application scenarios and possibilities for sulfide modification in steel,and provide certain reference for field process formulation.
		2022 Vol. 57 (3): 36-43 [Abstract] ( 217 ) [HTML 1KB] [PDF 3300KB] ( 357 )

	44	GUO Wei, LONG Mu-jun , WU Jia-lu, ZHANG Hao-hao, AI Song-yuan, CHEN Deng-fu
		Effect of solute partition coefficient and TiN precipitation on micro-segregation of 22MnB5 steel
		In order to improve the micro solute segregation in solidification process the accuracy of the model calculation, based on the solute distribution coefficient and the inclusion of the important influence to the solute segregation, this study quantitatively analyses the solute distribution coefficient and separation effect on solidification process of solute elements content of TiN, provide theoretical reference for the research on high strength steel solidification process of micro alloy. A solute microsegregation model coupled with TiN precipitation thermodynamic model was established for 22MnB5 steel, and the effects of temperature and solidification path on solute distribution coefficient were investigated. The results show that the phase transition has greater effects on k_Ti (titanium distribution coefficient) and k_N (nitrogen distribution coefficient) than the temperature. When the solid phase ratio is 0.74, the phase transition from L+δ to L+γ occurs, k_Ti decreases from 0.26 to 0.20, and the degree of titanium segregation increases. k_N increased from 0.30 to 0.46, and the degree of nitrogen segregation decreased. When the solid phase ratio f_s is 0.43, TiN begins to precipitate. When the effect of TiN precipitation on microstructure segregation is not considered, the mass percent of Ti and N in the liquid phase at the end of solidification is 0.286% and 0.005 6%, respectively. When TiN precipitation is considered, the mass percent of Ti and N in the liquid phase at the end of solidification are 0.237% and 0.001 9%, which decrease by 17.2% and 66.9%, respectively. At the same time, due to the high degree of titanium segregation during solidification, the enrichment of titanium at the solidification front is enough to offset the consumption of TiN precipitation, while the mass percent of initial nitrogen in steel is low, and the trend of nitrogen segregation decreases with the solidification process, and the degree of solute nitrogen segregation is also reduced under the influence of the transformation from L+δ to L+γ phase. So the segregation of solute nitrogen at the solidification front is not enough to offset the consumption of TiN precipitation. Therefore, the mass percent of nitrogen in the liquid phase at the solidification front increases to decrease obviously due to the precipitation of TiN, while the segregation degree of titanium only weakens at the end of solidification.
		2022 Vol. 57 (3): 44-54 [Abstract] ( 156 ) [HTML 1KB] [PDF 3523KB] ( 514 )

	55	CHEN Gu-jun, YANG Jiang, LI Long, ZHANG Min, HE Sheng-ping
		Metallurgical reaction behavior of Ar-CO₂ mixed injection during RH refining process
		The resource utilization of CO₂ during iron and steel production process makes a valuable contribution towards achieving the target of “carbon peak and carbon neutralization”. Ar-driven RH (ruhrstahl–heraeus) vacuum device is the key equipment for decarburization of ultra-low carbon steel, and the decarburization, degassing and inclusion removal can be effectively achieved by circulation flow of liquid steel in high vacuum. Since CO₂ can directly react with carbon in the liquid steel to form CO, the decarburization can be realized and the bath stirring can be strengthened. Therefore, an attempt was made to introduce the Ar-CO₂ mixed gas, as the lifting gas, into the RH decarburization process of ultra-low carbon steel. Firstly, the thermodynamic analysis between Fe-C-O melt and Ar-CO₂ was carried out to study the metallurgical reaction behavior under different pressures in RH refining conditions. Then, an industrial test platform for taking Ar-CO₂ mixed gas as RH lifting gas was built, and the effect of Ar-CO₂ mixed injection on decarburization, denitrification and temperature drop of liquid steel during RH decarburization process of ultra-low carbon steel was investigated by industrial tests. Thermodynamic analysis between Fe-C-O melt and Ar-CO₂ shows that CO₂ can react with carbon in the molten steel under conditions of low atmospheric pressure and ultra-low carbon content, and RH decarburization and degassing can be accelerated. Industrial test indicates that the average carbon content in molten steel after RH treatment with 100% CO₂, 50% Ar+50% CO₂ and 100% Ar injection are 0.001 50%, 0.001 57% and 0.001 19%, respectively, and thus the decarburization efficiency is not significantly affected by Ar-CO₂ mixed injection. Meanwhile, compared with 100% Ar injection, 100% CO₂ and 50% Ar+50% CO₂ injection have slight effect on RH denitrification efficiency and temperature drop of molten steel because the reaction of CO₂ with carbon is quite limited. Therefore, CO₂ can be used to partially or completely replace the Ar during RH decarburization process of ultra-low carbon steel based on economic and environmental considerations, although the refining efficiency cannot be improved.
		2022 Vol. 57 (3): 55-60 [Abstract] ( 162 ) [HTML 1KB] [PDF 1491KB] ( 451 )

	61	PIAO Zhan-long, WANG Xing-juan, ZHANG Cai-jun, ZHU Li-guang, LI Shao-ying, WANG Bo
		Steel-slag interface reaction behavior in continuous casting mold of high titanium steel
		In order to control the steel-slag interface reaction of high titanium steel in the continuous casting process, the steel-slag interface reaction experiment between high titanium steel which the w([Ti]) was 0.05%-1.91% and conventional CaO-SiO₂ system mold flux was conducted by the electromagnetic induction furnace, and then the effect of different Ti contents on the steel-slag interface reaction was systematic analyzed. The rate controlling step of steel-slag interface reaction was judged by two-film theory and elements mass transfer. Meanwhile, the kinetic model was established combining the law of mass conservation and equation of chemical equilibrium, which revealed the mechanism and reaction extent of steel-slag interface reaction. It is found that the extent of steel-slag interface reaction is slight when w([Ti]) is 0.05%. When the w([Ti]) is 0.20% and the reaction is balance, the w([Ti]) in steel and w((SiO₂)) in mold flux are decreased from 0.20% to 0.01% and 31.8% to 29.1%, respectively, and the balance time is 600 s. When the w([Ti]) is 1.91% and the reaction is balance, the w([Ti]) in steel and w((SiO₂)) in mold flux are decreased from 1.91% to 0.05% and 31.77% to 16.98%, respectively, and the balance time is 900 s. It is clearly stated that the extent and equilibration time of steel-slag interface reaction is increased with w(Ti). The mass transfer of Ti, Si in steel and TiO₂, SiO₂ in mold flux all have some impact on the slope of 公式 and t, which means that the mass transfer of them are all the reaction rate controlling step, and the effect of Ti is the most. The change trends of calculated value from kinetic model and experimental value are consistent, which indicates that the model can describe the reaction extent of actual steel-slag interface, furthermore, it provides theoretical guidance for the steel-slag interface reaction of high titanium steel.
		2022 Vol. 57 (3): 61-70 [Abstract] ( 292 ) [HTML 1KB] [PDF 3919KB] ( 698 )

Metal Forming

	71	WANG En-rui, CHEN Zi-gang, LIU Feng-lin, LIU Tian-wu, ZHANG Ming
		Oxide scale structure of hot rolled structural steel and its effect on pickling quality
		To clarify the oxide scale thickness and structure of hot rolled structural steel and the effect on pickling quality, two hot rolling processes called “High Temperature and Low Cooling Speed (HT-LCS)” and “Low Temperature and High Cooling Speed (LT-HCS)” were designed in this work. The preparation of hot rolled structural steel was carried out accordingly. Oxide scale thickness and structure in the transverse direction of hot rolled strip under different hot rolling processes and its surface morphology after pickling were analyzed by OM and SEM. On the basis of oxide scale thickness and structure difference, the pickling effects and causes of color difference defect after pickling were discussed. The results show that the oxide scale for both designed hot rolling processes is composed of outer Fe₃O₄ layer and low-temperature transformation structure of FeO located inside of oxide scale. Because of uneven distribution of temperature field during rolling process and after coiling, the thickness of oxide scale at the edge of strip is small and structure is compact, and the content of Fe₃O₄ at the edge of strip is more than that in the middle. On the other side, oxide scale is thick and porous in the middle of strip, and the transformation of FeO at low temperature is more sufficient than in the edge area. The transverse uniformity of oxide scale, including oxide scale thickness and structure distribution, was poor under HT-LCS process. Specifically, the thickness difference of oxide scale between edge and middle area of strip was 4.7 μm,and the thickness difference of Fe₃O₄ was up to 2.5 μm. However, the transverse uniformity of oxide scale was much better under LT-HCS process. The thickness difference of oxide scale between edge and middle area was 2.5 μm,which was reduced by 46.81% compared with that of HT-LCS process, and the thickness difference of Fe₃O₄ layer was 0.2 μm, which was only 8.0% of the former. The transverse uneven distribution of thickness and structure for oxide scale are the main inducement to defect of “pickled dark strip”. Eutectoid structure (α-Fe+Fe₃O₄) is loose and porous, and its pickling process is carried out in the way of “stripping”, which is more efficient in pickling. The parts of strip that are preferentially pickled will be continuously immersed in the acid solution, resulting in a large number of “erosion cracks” on the strip surface, and lead to a “color difference” finally. Optimizing the oxide scale distribution, adjusting the proportion of Fe₃O₄ and eutectoid structure in oxide scale are important to optimize production process and improve the pickling quality.
		2022 Vol. 57 (3): 71-78 [Abstract] ( 314 ) [HTML 1KB] [PDF 3035KB] ( 506 )

Materials

	79	YAN Shao-wen, MU Xing, QI Yan, XU Li-hong, ZHANG Hong-ping
		Research progress on mechanical properties strengthening of Fe-Ga magnetostrictive alloy
		Fe-Ga magnetostrictive alloy is one of important magnetically driven smart materials,it has not only the characteristics of functional material with high magnetostrictive strain under low magnetic field,but also the characteristics of structural material with high mechanical strength. The integration of structure and function is obvious,which has extensive research value and application prospect. A large amount of researche has been carried out on the control of its magnetostrictive properties and mechanical properties. Among them,it is feasible to control mechanical properties and magnetostrictive properties by adding elements into Fe-Ga alloy,and a series of Fe-Ga magnetostrictive alloys with integrated structure and function have been preliminarily obtained. Focused on the strengthening and toughening mechanism,the research progress of mechanical properties strengthening of Fe-Ga magnetostrictive alloy is described. The effects of strengthening and toughening mechanism caused by element addition, such as solid solution strengthening,second phase strengthening and fine grain strengthening,on mechanical properties and magnetostriction properties of Fe-Ga alloy are reviewed. The results have shown that the addition of Al,Nb,Mo,V,Co,Mn,Cr,C and other elements in Fe-Ga alloy matrix has a high solid solubility,and the strengthening and toughening mechanism of the alloy is mainly by solution strengthening effect. However,the addition of carbides such as NbC and TaC or elements such as Tb,Dy,Y and B in Fe-Ga alloy matrix has a low solid solubility,and the strengthening and toughening mechanism of the alloy is mainly the second phase strengthening and fine grain strengthening effect. Among them,the appropriate addition of Co,Al,C,B,NbC,TaC,Tb,Dy,Y is possible to rea lize the simultaneous optimization of mechanical properties and magnetostrictive properties. Finally,combined with the latest researchresults of domestic and foreign scholars on Fe-Ga magnetostrictive alloy,the future research is prospected.
		2022 Vol. 57 (3): 79-90 [Abstract] ( 222 ) [HTML 1KB] [PDF 5799KB] ( 428 )

	91	JIANG Chang, WANG Zi-bo, WANG Yang, LU Heng-chang, MAN Ting-hui, ZHOU Lei
		Continuous cooling transformation law of cold work hardening non-quenched and tempered steel
		The continuous cooling transformation(CCT) law of steel is the basic basis of microstructure regulation. In order to optimize the microstructure and mechanical properties of cold work hardening non-quenched steel for fasteners in hot rolling state,the thermal expansion curves of the test steel at cooling rates 0.1-50 ℃/s was measured by DIL805A phase transformation instrument,combined with metallographic hardness method to determine the transformation type,and draw the static CCT curve of the test steel. The results show that the martensite transformation point (M_s) of the test steel is 280 ℃,and ferrite is formed in different cooling rate ranges. With the increase of cooling rate,the transition temperature of ferrite and pearlite decreases,and the content and grain size of ferrite decrease. Cooling rate less than 3 ℃/s,the room temperature microstructure is composed of proeutectoid ferrite and pearlite,and the hardness changes little with the increase of cooling rate,which is 156-166HV. When the cooling rate reaches 3 ℃/s,bainite and martensite begin to appear,and the hardness increases rapidly to 181HV. When the cooling rate is greater than 3 ℃/s,the content of proeutectoid ferrite and pearlite decrease gradually,the content of bainite and martensite increase,and the hardness increase continuously. When cooling rate is 30-50 ℃/s,the microstructure is mainly bainite and martensite.Nb and V play important roles in the continuous phase transition. The precipitation behavior of Nb and V carbonitride in the test steel was calculated by Thermo-Calc software. The total solid solution temperatures of V (C,N) and Nb (C,N) were 780 ℃ and 1 144 ℃ respectively. Under the condition of austenitizing at 900 ℃,V(C,N) is completely solid solution,and Nb(C,N) is solid solution by 8%. Because the diffusion rate of Nb and V is much slower than that of C,the solid solution Nb and V have no time to diffuse in the cooling transformation process and gather at the two-phase interface,reducing the growth rate of ferrite,inhibiting the formation of ferrite and promoting bainite or martensite transformation.
		2022 Vol. 57 (3): 91-96 [Abstract] ( 152 ) [HTML 1KB] [PDF 3199KB] ( 397 )

	97	PENG Ning-qi, FU Gui-qin, ZHOU Wen-hao, FAN Ming, XIONG Xiang-jiang, ZHU Miao-yong
		Material selection and acceptance of fracture resistance for high strength and toughness weather-resistant bridge steel of Q690qNH
		For the 40 mm thick Q690qNH weathering steel plates for bridge produced by TMCP+T and QT processes, tensile tests on longitudinal surface, longitudinal 1/4, longitudinal center and transverse surface at room temperature and Charpy V-shaped impact tests at -120 -+20 ℃ were carried out according to GB/T 228.1—2010 and GB/T 229—2020 standards respectively, and series temperature dynamic tearing tests of -120-+20 ℃ and type P2 non-plastic transition temperature drop hammer tests on longitudinal surface, longitudinal central and transverse surface were carried out according to GB/T 5482—2007 and GB/T 6803—2008 standards respectively, and longitudinal crack tip opening displacement (CTOD) tests and full-thickness deep notched wide plate tensile tests were carried out according to GB/T 21143—2014 and Q/725-1182—2005 standards. Then the experimental data and their correlations were analyzed, at the same time, the metallographic structure of different thickness of steel plate of two kinds of process were observed by using optical microscope, and the fracture morphology of experimental CTOD samples were observed by scanning electron microscope (SEM), and combining with the failure assessment FAD diagram of BS 7910 and the estimation of fracture driving force of typical bridge welded members, the material selection and acceptance method of fracture resistance for high strength and toughness weathering bridge steel Q690qNH were discussed. Results show that the steel plate with QT process has more uniform strength in transverse, longitudinal and thickness directions, and its plasticity, impact, dynamic tear, CTOD and fracture toughness K_C are better, and can be used as D-class steel for key components. However, if it is used as E-class steel, even for general components, there is a certain risk. While the steel plate with TMCP+T process has poor fracture toughness, and even as D-class steel, it does not meet the requirements of material selection based on fracture resistance. It also shows that the rapid increase of brittleness starting temperature at 1/4 thickness of longitudinal impact test has good reliability and applicability as the breaking criterion and acceptance of test Q690qNH weather-resistant bridge steel. When used as a key component, the fiber area ratio at 1/4 thickness of longitudinal impact fracture should be higher than 97.5% and the corresponding impact energy should not be less than 125 J.
		2022 Vol. 57 (3): 97-107 [Abstract] ( 171 ) [HTML 1KB] [PDF 4423KB] ( 363 )

	108	ZHOU Da-qian, LU Heng-chang, LI Zhi-feng, WEI Xi-cheng, DONG Han
		High temperature oxidation behavior and kinetics of HRB400 rebar
		In order to optimize the oxide layer structure of HRB400 rebar to improve corrosion resistance, the oxidation behavior of test steel under air condition at temperatures of 800, 850, 900, 950, 1 000 and 1050 ℃ was investigated using the thermogravimetric method. An oxidation kinetic model was developed, the oxidation activation energy of test steel was calculated, and the structure and composition of oxide layer was analyzed and determined by scanning electron microscopy (SEM). The oxidation layer formation law was discussed in relation with the actual production of rebar and an oxidation skin growth model was established. The results showed that the oxidation of test steel had a fast oxidation phase with a linear oxidation kinetic curve in the early stages and a slow oxidation phase with a parabolic oxidation kinetic curve in the middle and late stages, and the time required to change from linear to parabolic increased with the temperature increasing. The oxidation activation energy of test steel was 208.4 kJ/mol which was calculated by Origin fitting. The best macroscopic condition of test steel oxide skin surface appeared at an oxidation temperature of 900 ℃, and varying degrees of flaking and damage to the test steel oxide skin at all other oxidation temperatures. At the oxidation temperatures of 850 and 900 ℃, only dark grey outer layer of Fe₃O₄ and light grey inner layer of FeO were observed in the test steel oxide due to the low oxidation temperature which could not break through the energy barrier for Fe₂O₃ production. The oxide skin of test steel at oxidation temperatures of 950, 1 000 and 1 050 ℃ consisted of a three-layer structure of Fe₂O₃, Fe₃O₄ and FeO. As the oxide skin undergone pre-eutectoid reaction (precipitation of Fe₃O₄ from FeO) and eutectoid reaction (transformation of FeO into Fe₃O₄ + Fe) during cooling, a complex oxide skin structure was resulted in.
		2022 Vol. 57 (3): 108-114 [Abstract] ( 208 ) [HTML 1KB] [PDF 2519KB] ( 478 )

	115	LI Long-fei, ZHANG Yang, LIN Teng-chang, MENG Hua-dong, HE Qing, YAO Tong-lu
		Austenite grain growth behavior of X80 pipeline steel containing vanadium
		In order to make clear the influence of vanadium addition on the austenitizing process of X80 pipeline steel, the austenite grain growth behavior of 4 experiment steels with different vanadium contents (0%, 0.042%, 0.084%, 0.130%) under different austenitizing temperatures was investigated, and the austenite grain growth kinetics in the experimental steel was analyzed and calculated by Thermo-Calc thermodynamic calculation, austenitizing heating treatment, metallographic analysis and theoretical model derivation and calculation. The results show that as the soaking temperature is lower than 1 050 ℃, the austenite grain size and change trend of 4 experimental steels with different vanadium contents are similar. But when the soaking temperature is higher than 1 050 ℃, the austenite grain size of vanadium free experimental steel is significantly higher than that of experimental steels containing vanadium. With vanadium contents increasing, the number of vanadium containing precipitates increasesHowever, due to its low solution temperature, vanadium content has little effect on austenite grain growth of vanadium containing steels. The austenite grain size of experimental steel grew up with the increase of austenitizing temperature. When the soaking temperature was in the range of 850-900 ℃, the austenite grains grew slowly, while the austenite grain sizes increased rapidly when the soaking temperature was higher than 1 200 ℃. The austenite grain sizes of 4 experimental steels increased exponentially with the increase of soaking temperature. At the same austenitizing temperature, the austenite grain size increased with the increase of soaking time, and the growth rate gradually decreased. The measured experimental data combined with the grain growth kinetics theory were used to establish a mathematical model of No.2 experimental steel containing 0.042% vanadium content, 公式, which was verified and fitting result was good. The research and experimental conclusions obtained in this paper can provide a theoretical basis for the thermo mechanical control process parameter design and engineering application of vanadium containing X80 pipeline steel.
		2022 Vol. 57 (3): 115-123 [Abstract] ( 207 ) [HTML 1KB] [PDF 3720KB] ( 549 )

	124	CAO Sheng-li, WU Shao-wen, ZHANG Cai-jun, ZHANG Qing-jun
		Three-dimensional morphology and formation mechanism of grain boundary ferrite in low carbon microalloyed steel
		In order to better understand the three-dimensional morphology and formation mechanism of grain boundary ferrite in low carbon microalloyed steel, the 3D morphology of the different location was observed by focused ion beam scanning electron microscope equipped with electron back-scatter diffraction(EBSD), and the growth rate under test conditions was calculated by in-situ observation technology, finally the solute diffusion model was calculated by Matlab,from two aspects of test results and the theoretical data for the demonstration and analysis. The results show that the grain boundary surface ferrite does not grow along the austenite parent phase grain, but grows in a certain angle toward the grain. At the same time, it only grows near the austenite grain boundary and cannot grow too deep. Its three-dimensional morphology is flat on the front and thin strip on the side, accompanied with a large number of pits and defects. The grain boundary ribbed ferrite and austenite at the grain boundary have fixed interface on one side, and the other side is angular and grows into the grain. The three-dimensional morphology of ridged ferrite is like a triangular pyramid with a pointed tip. The adhesion surface is smooth, tidy, and the side has a deep gully. The findings were calculated using in situ observation techniques, the grain boundary ferrite precipitated at 725-775 ℃ has a faster growth rate, Locating between 100-250 μm/s, and the grain boundary ferrite precipitated at other temperatures has a lower growth rate. The distribution of grain boundary ferrite growth rate with temperature in local equilibrium/ para-equilibrium mode is obtained, the results find that the growth rate of grain boundary ferrite is mainly distributed in the para-equilibrium mode, and the growth rate of intragranular ferrite is only controlled by carbon diffusion.
		2022 Vol. 57 (3): 124-132 [Abstract] ( 186 ) [HTML 1KB] [PDF 5219KB] ( 419 )

Environmental Protection and Energy

	133	LIU Chen, HU Bing, HU Pei-wei, WEN Rong-yao, YE Heng-di, WEI Jin-chao
		Innovative coupled denitrification technology of SNCR and embedded SCR for pelletizing flue gas
		Under the situation of vigorously promoting green and low-carbon development in China, iron and steel industry comprehensively implements ultra-low emission of air pollutants from sintering and pelletizing. At present, the NO_x emission reduction in pelletizing is imminent, which is related to the survival and development of pellet industry. Aiming at the problem of high NO_x emission concentration in the domestic mainstream grate-kiln process of pelletizing production, research on coupled denitrification technology of selective non-catalytic reduction denitrification technology (SNCR) and embedded selective catalytic reduction denitrification technology (SCR) was conducted on the basis of system analysis for flue gas features and NO_x distribution. The results show that pelletizing flue gas has the characteristics of high temperature (850-1 000 ℃ in the hood, 350 ℃ in the bellows), high NO_x concentration (400-600 mg/m³) and small flow at the preheating stage of grate source, which is conducive to the collaborative coupling technology application of SNCR and SCR methods. When ammonia hydroxide is used as reducing agent, flue gas temperature is 830-930 ℃ and ammonia nitrogen mole ratio is 1.0-1.5, the denitrification rate of SNCR method can reach 40%-60%. The assembly of air balance plate on the grate can solve the cross air problem and prevent the disorderly diffusion of NO_x. Then adopting NO_x centralized treatment and implementing precise control of reducing agent dosage, can comprehensively improve the utilization efficiency of reducing agent and SNCR denitrification rate. Optimizing the structure of conical diffusion plate in SCR reactor was made by FLUENT numerical simulation method. When the horizontal angle of diffusion plate was tilted from 90° to 65°-75°, the distribution of flue gas velocity and ammonia reducing agent into the rectifier grid were more uniform. The optimized pelletizing flue gas SNCR coupling embedded SCR denitrification technology has a reasonable route, superior technical and economic performance, and a broad prospect for industrial application, which is a major innovation of China's pelletizing flue gas nitrogen oxide ultra-low emission technology.
		2022 Vol. 57 (3): 133-141 [Abstract] ( 171 ) [HTML 1KB] [PDF 5412KB] ( 357 )

	142	YIN Ruo-ming, FU Hai-tao, YANG Xiao-hong, AN Xi-zhong
		Iron oxide nanoparticles prepared by sinter ash of sintering machine and their gas-sensing performances
		Sinter ash of sintering machine is considered as undesirable waste with high iron content during ironmaking processes, and how to deal with sinter ash is always a difficult point in metallurgical field. In this work, we demonstrated a method for preparing high value-added spherical iron oxide nanoparticles by sinter ash. Various iron oxide nanoparticles (e.g. pristine α-Fe₂O₃ and Fe₃O₄ nanoparticles, and Fe₃O₄/Fe₂O₃ nanocomposites) were successfully prepared by controlling the ratio of reducing agent to iron element via a solvothermal process. X-ray powder diffractometer (XRD), X-ray fluorescence spectrometer(XRF), ultraviolet spectrophotometer, field emission scanning electron microscopy(SEM) were used to characterize the materials. The results indicate that pure α-Fe₂O₃, Fe₃O₄ nanoparticles, or different Fe₃O₄/Fe₂O₃ ratio nanocomposites can be gotten by controlling the amount of reducing agent. The sizes of these nanoparticles are uniform and they all have high purity (α-Fe₂O₃, 92.74%; Fe₃O₄, 94.44%), and they are easily prepared and have high repeatability. The gas sensing performance of prepared iron oxide nanoparticles was tested by gas sensor tester. The nano scaled products showed excellent gas sensing performance, especially towards 1-butanol had high sensitivity and unique selectivity. It is found that the optimal working temperature of Fe₃O₄/Fe₂O₃ nanocomposites (100 ℃) is lower than those of α-Fe₂O₃ and Fe₃O₄ nanoparticles by 160 and 100 ℃, respectively. Among the composites, 56/44 Fe₃O₄/Fe₂O₃ nanocomposite shows the highest sensing response (6.33) towards 1-butanol. The preparation of high-added value iron oxide nanoparticles with sintering machine of sinter ash realized the rational utilization of sintering machine ash resource, which has important theoretical and practical significance, and it provides a reference example for treatment of high iron-bearing solid waste in the steel and ironmaking process.
		2022 Vol. 57 (3): 142-152 [Abstract] ( 140 ) [HTML 1KB] [PDF 5770KB] ( 380 )

	153	ZHANG Xiao-ying, LI Su-qin, LEI Hai-ping, LI Yong-kui
		Discussion on removal of chloride ion from circulating water in iron and steel industry
		Circulating cooling water in the iron and steel industry accounts for 70%-80% of industrial water consumption. It is mainly used in factories to condense steam and cool products or equipment. Facing the increasingly serious shortage of water resources in China, increasing the circulation rate of the water treatment system, reducing the new water index per ton of steel, and increasing the concentration multiple of the circulating cooling water system are one of the important water-saving technologies. With the increase of the concentration ratio, chloride ions could continually concentrate, which greatly aggravates the risk of intergranular corrosion of equipment and pipelines, affects normal production and shorten the service life of equipment, and even leads to personal safety accidents. Therefore, it is an inevitable choice to remove chloride ions from circulating water in the iron and steel industry. Experts and scholars at home and abroad have devoted themselves to studying the removal of chloride ions in various types of waste-water, forming four major types of chlorine removal technologies, namely precipitation salt method, separation method, ion exchange method, and oxidation-reduction method. In addition to their advantages, these technologies also have some shortcomings. The articles describe different chloride ion removal technologies and their mechanism of action, and compares and analyzes their advantages and limitations in the removal of chloride ions in water, highlights the advantages of the lime aluminum salt precipitation method, and proposes a process technology for the removal of chloride ions in circulating water in the iron and steel industry. At the same time, this also provides a new idea for the continuous concentration of chloride ion removal problems. It is believed that the technology of removing chloride ions from water will become more and more perfect in the future, and it will also play an increasingly important role.
		2022 Vol. 57 (3): 153-159 [Abstract] ( 207 ) [HTML 1KB] [PDF 808KB] ( 391 )

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