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	2022 Vol. 57 No. 9
	Published: 2022-09-15



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

Technical Reviews

	1	WANG Xin-dong, HUANG Yong-jian, PENG Shao-feng, YU Yang-yang, LI Shuang-jiang
	')" href="#">	A new generation of electric furnace short-flow special steel plant HBIS Group Shisteel New Region designed with concept of "green, intelligent and efficient"
		HBIS Group Shisteel new region is a concrete practice of full implementation of the guiding spirit of "Determined to reduce, initiative to adjust and accelerate transformation" which is put forward by General Secretary Xi Jinping and the concrete practice of the transformation and upgrading of the Iron and steel industry in Hebei Province. Hesteel is committed to building the new area into a green production, intelligent production line, efficient process, high-end products of modern special steel dream factory. Based on the design concept of "green, intelligent and high efficiency", and guided by the theory of metallurgical process engineering, HBIS Group Shisteel new area uses the physical system and process interface technology of metallurgical manufacturing process, which is dynamic and orderly, cooperative and continuous, the planning and design of the new generation of EAF short-flow special steel demonstration project is a vivid portrayal of the global special steel enterprise intelligent manufacturing and the transformation and upgrading of China's steel industry from long-flow to short-flow steel. HBIS Group Shisteel new region is a collection of the world's most outstanding design elements and ideas in short-flow process innovation, full-process ultra-low emissions, intelligent manufacturing and other aspects. The project integrates more than 70 advanced short-process cutting-edge technologies and green steel manufacturing technologies, targeting 3 series of high-end products to achieve ultra-low emissions. The project covers the first large-scale double-shaft scrap preheating ultra-high-power DC ARC furnace in China and the largest section and deepest depth vertical caster of special steel bloom in the world, it has promoted the homogenization level of steel for high-end equipment manufacturing in our country and the step of domestic production substitution. The new zone has led to the brand appreciation of the special steel industry in Tianjin, Hebei and Hebei. It represents the development direction of a new generation of green, intelligent and efficient electric furnace short-flow steel mills in the steel industry under the dual-carbon target, it also contributes to the development of electric furnace short process in China's iron and steel industry.
		2022 Vol. 57 (9): 1-10 [Abstract] ( 276 ) [HTML 1KB] [PDF 3501KB] ( 840 )

	11	ZHANG Fu-ming
		Development prospects and methods on low- carbon technology in ironmaking system
		The man-made agglomerate iorn ore and coke are the modern blast furnace ironmaking material basis. Modern blast furnace realizing green and low-carbon ironmaking needs to optimize the technical process and key technologies from the level of ironmaking procedure, and realize the collaborative optimization of multiple processes such as sintering, pelletizing and blast furnace. Facing the future, to improve the resource and energy utilization efficiency, adopt low-carbon energy saving technology and advanced technical process base on the fundation of existing technology. For the traditional technologies such as sintering and blast furnace, advanced technologies should be further researched and applied to improve production efficiency and reduce energy consumption and carbon emissions. The green and low-carbon sintering technologies should be continue to study and promote, such as low-carbon and thick material layer sintering technology, hydrogen-rich gas spraying technology of sintering material surface, reback sinter ore efficient recovery technology, low temperature sintering technology and hot air circulating sintering technology, to effectively reduce energy consumption and CO₂emissions in the sintering process. Make the most of China's concentrate iron ore fine resources to produce pellet, improve the production capacity and output of pellet, and then improve the pellet charging ratio and the comprehensive grade of burden, and effectively reduce the carbon fuel consumption. Increase the blast furnace oxygen enrichment ratio and pulverized coal injection rate, continue to increase the hot blast temperature and reduce the fuel consumption, and improve the blast furnace top pressure and gas utilization ratio. The hydrogen enrichment gas injection to reduce coke consumption, develop and apply the blast furnace top gas recycle injection and CO₂ removal and reuse technology (CCUS) in some conditional blast furnaces. The thermodynamic mechanism of carbon-hydrogen coupled reduction in blast furnace ironmaking process is researched and analyzed, the reduction capacity of solid carbon, CO and H₂ under different temperature zone in blast furnace is discussed, and the coupling and matching of direct reduction and indirect reduction is the technological core of the lowest fuel ratio are prosoed. The technical feasibility and economy of full hydrogen or enriched hydrogen injection into blast furnace are discussed. These comprehensive technical measures have a significant effect on further reducing the carbon consumption and reducing the CO₂ emission of the blast furnace process. As while as, design advanced and reasonable process system and dissipative structure, optimize the procedure interface technology, and construct a cyber physical system (CPS) to realize the coordinated, efficient, dynamic and orderly operation of ironmaking process. It is also one of the key and common technologies of blast furnace ironmaking process to achieve green and low carbon, and has wide applicability and significant application effect.
		2022 Vol. 57 (9): 11-25 [Abstract] ( 405 ) [HTML 1KB] [PDF 5728KB] ( 553 )

	26	ZHANG Fu-cheng, KANG Jie
		Progress in scientific research of interfaces in steel (Ⅱ)
		The chemical composition, crystal structure and electronic structure of the interfaces in steel, and their evolution under the action of external environments such as deformation and heating, all profoundly influence the mechanical and chemical behavior of the steel. They dominate the mechanical, chemical and processing properties. The interface in steel is often the nucleation point of new phases, the nodal point of deformation, the starting point of cracking and the source of corrosion. To a certain extent, by clarifying the science of interfaces in steel, the nature of steel failure and the direction of improving steel quality are also known. Based on the scientific study of interfaces in steel (Ⅰ), a detailed review of the effects of interfaces on the phase transformation behavior and service performance of steel is provided. The effects of phase boundaries and phase boundary composition or precipitate segregation on austenite to ferrite transformation, austenite to bainite transformation and reversal austenite transformation are analyzed; the effects of interfaces and interface composition segregation on strength, plasticity and toughness are discussed; the role of twin grain boundaries, phase boundaries and inclusions/matrix interfaces in fatigue crack initiation and extension is described; the focus is on the mechanism and application of grain boundary, twinning boundary and grain boundary segregation controlling to improve corrosion resistance; the effect of various interface types on the hydrogen embrittlement resistance is analyzed and the role of interfaces in creep deterioration is briefly discussed. The application of machine learning to interface research is also briefly introduced, and the interface science issues of steel in service performance are identified, along with suggestions for future research priorities.
		2022 Vol. 57 (9): 26-41 [Abstract] ( 199 ) [HTML 1KB] [PDF 6890KB] ( 541 )

Raw Material and Ironmaking

	42	GAO Jian-jun, ZHU Li, KE Jun-chao, HUO Xu-feng, QI Yuan-hong
		Industrialized application of hydrogen-rich gas injection into blast furnace of Jinnan Steel
		Iron and steel industry is one of the largest industrial carbon dioxide producers in China, accounting for about 15% of the total carbon dioxide emission. Blast furnace is the dominate carbon consumer, accounting for more than 70% of the total carbon consumption in the iron and steel making process. Lowering the carbon consumption of blast furnace is the most effective measure to reduce the carbon dioxide emission of iron and steel industry. Injecting hydrogen-rich gas into blast furnace can not only improve productivity and reduce pollutant emission, but also decrease coke or pulverized coal consumption, resulting in less carbon consumption in blast furnace at its source and less carbon dioxide emissions. Taking the industrial test data of hydrogen-rich gas injection into two 1 860 m³ blast furnaces of Shanxi Jinnan Steel Group as an example, the effects of hydrogen-rich gas injection into blast furnaces on fuel ratio, theoretical tuyere combustion temperature, bosh gas volume, H₂ utilization rate and CO₂ emission were studied. The results show that injecting hydrogen-rich gas can significantly reduce the consumption of solid fuel in blast furnace. When the injection volume of hydrogen-rich gas per ton of hot metal is 65 m³, the replacement ratio of hydrogen-rich gas to solid fuel is 0.49 kg/m³. The injection of hydrogen-rich gas into the tuyere lowers the theoretical tuyere combustion temperature by about 1.5 ℃ for each injection of 1 m³ hydrogen rich gas, and the blast volume and bosh gas volume of blast furnace decrease slightly. After injecting hydrogen-rich gas, the average utilization rate of H₂is 37.3%, the average utilization rate of CO is 43.2%. When the injection volume of hydrogen-rich gas per ton of produced hot metal is 65 m³, CO₂ emission per ton of produced hot metal can be reduced by about 80 kg, and CO₂ emission of blast furnace can be decreased by 5.6%, achieving good economic, environmental and carbon reduction results.
		2022 Vol. 57 (9): 42-48 [Abstract] ( 282 ) [HTML 1KB] [PDF 2687KB] ( 690 )

	49	ZHAO Hua-tao, LU Yu, HAN Xu, DU Ping, ZHANG Guo-liang
		Research and application of circumferential imbalance in Shasteel blast furnace
		In order to study the circumferential imbalance of O/C distribution in blast furnace and to minimize the gas fluctuation during the bunker change, a mathematical model on mass distribution in circumferential direction of blast furnace was developed. The mass distribution of burden material under different bunker-material combinations and different chute rotating directions was measured with a cold charging model which was built based on 1∶15 of the 5 800 m³ blast furnace, verifying the mathematical model. As a further step, the O/C distribution change pattern in circumferential direction was computed under different bunker-material combinations and chute rotating directions. It is revealed that change of bunker-material combination mainly reduces the deviation of O/C in east-west direction, while change of chute rotating direction mainly reduces the deviation of O/C in south-north direction for the blast furnace equipped with two bunkers in east-west direction. It also shows that the maximum O/C difference in circumferential direction during alteration of bunker-material combination is much bigger than the maximum O/C difference during alteration of chute direction. However, during the actual blast furnace operation, when the bunker change is being done, the gas distribution change is rather violent, causing high pressure drop, especially when the blast furnace condition is not stable. To overcome this problem, the O/C difference in each direction was calculated at different bunker-material combinations and chute rotating directions, and a combination of bunker change and chute rotating direction change was formulated to minimize the gas fluctuation during the bunker change. Three 2 680 m³ blast furnaces in Shasteel adopted this method and succeeded in improvement of hot metal quality, operational stability and technical index, as well as the reduction of equipment malfunction.
		2022 Vol. 57 (9): 49-56 [Abstract] ( 167 ) [HTML 1KB] [PDF 3726KB] ( 514 )

	57	PANG Jing, WANG Zhen-yang , ZHANG Jian-liang, ZHANG Shu-shi
		Construction and verification of energy and mass transfer model for HIsmelt smelting reduction main reactor
		HIsmelt smelting reduction ironmaking process takes iron ore powder and coal powder as raw materials, and does not require sintering, pelletizing and coking in the process. Compared with the blast furnace ironmaking process, it has the advantages of carbon reduction and emission reduction. Clearing the process of energy and mass transfer has guiding significance for the actual production of HIsmelt smelting reduction ironmaking. Based on the material balance and heat balance equation, the material and energy balance of input and output HIsmelt main reactor were calculated, and the energy and mass transfer model was established. The model was corrected by mass distribution ratio of each element between slag and iron calculated by Equilib module in FactSage and the actual production data. The model could calculate the effects of raw material and fuel composition, mass ratio of iron ore to coal, secondary combustion rate, hot air oxygen content and other parameters on the main smelting indexes such as slag iron temperature, slag composition, hot air volume and gas volume. Secondly, based on the model, the material balance and heat balance were calculated. According to actual production data, the calculation results of model were verified, and the results show that the model was highly consistent with the actual production data. The effect of the mass ratio of iron ore to coal on smelting was studied. When the mass ratio of iron ore to coal is between 1.39 and 1.45, a reduction of 0.1 in the mass ratio of iron ore to coal will reduce the secondary combustion rate by 0.23%, resulting in a lower utilization rate of gas chemical energy, while more hot air is needed to make the pulverized coal burn, and the amount of hot air and gas production increases, which can be improved by appropriately increasing the oxygen content of the hot air to improve the secondary combustion rate and reduce the amount of gas. The decrease of the mass ratio of iron ore to coal by 0.001 increases the slag iron temperature by 3.76 ℃, which is conducive to the subsequent processing of molten iron. However, the increase in hot metal temperature reduces the ratio of elemental Fe in the iron and slag, which increases the mass percent of FeO of slag by 0.026% and increases the iron loss, which can be reduced by reducing the amount of oxygen-rich hot air blowing to reduce the amount of iron oxidation, thus reducing the iron loss.
		2022 Vol. 57 (9): 57-64 [Abstract] ( 186 ) [HTML 1KB] [PDF 2881KB] ( 477 )

Steelmaking

	65	MENG Yao-qing, LI Jian-li, ZHU Hang-yu, WANG Kun-peng, WANG Wei
		Crystallization of CaO-SiO₂-Al₂O₃ based inclusions in solid steel killed by Si-Mn alloys
		In order to avoid the harm of high melting point hard inclusions such as Al₂O₃ and MgO·Al₂O₃ to subsequent processing of steel and product service properties, inclusion plasticizing control technique by Si-Mn killed is adopted for some steels, such as valve-spring steel, saw-wire steel and the thinnest stainless steel. It is insufficient for inclusion plasticizing control technique to focus only on whether the inclusion composition is in the low melting point region of phase diagram. The good plastic deformation of silicate inclusions in steel under non-liquid condition is mainly due to their properties of glass materials, and their softening temperature is obviously lower than hot rolling temperature. The hot rolling rheology of silicate inclusions largely depends on their crystallization state, so the transition of the inclusion from glassy state to crystalline state needs to be studied and controlled. The differences between glassy and crystalline inclusions were compared in terms of microstructure and microhardness change during heating, and the adverse effects of inclusion crystallization on the inclusion plasticizing control technique were pointed out. Through industrial examples and literature reports, it was clarified that glass inclusions may undergo crystallization transformation during steel solidification and heat treatment prior to hot rolling. In order to prevent serious crystallization of glassy inclusions, it is necessary to optimize the heating temperature and time of bloom/billet by combining the TTT curve of inclusions, or controlling the inclusion composition to fall into the more stable region of glass phase. Based on the research of current scholars, it is considered that the eutectic zone of tridymite, pseudo-wollastonite and anorthite is the ideal composition region for CaO-SiO₂-Al₂O₃ system inclusions to realize glass state stability control. The influence of magnesium oxide and alkali oxides on the crystallization properties of oxide inclusions in Si-Mn killed steel still needs to be studied further. And the TTT diagrams for relevant oxide inclusion compositions can be studied by the method such as SHTT (single hot thermocouple technology).
		2022 Vol. 57 (9): 65-74 [Abstract] ( 265 ) [HTML 1KB] [PDF 5000KB] ( 501 )

	75	WANG Qiang-qiang, CAI Zi-jie, SUN Pan, LIU Xiao-hua
		Analysis on interface wettability between TiC and steel
		TiC particle has characteristics of high hardness, high melting point, high thermodynamic stability and so on. As the reinforcing phase, TiC has the potential to improve the strength, high temperature resistance and wear resistance of steel matrix. In recent years, much attention has been paid to the development of related steel grades. Good wettability between reinforcing phase and steel matrix is the key to improve interfacial bonding strength and prevent particles from falling off during the steel wear service. To clarify the wettability between steel and TiC and guide the development of wear-resistant steel with TiC as the reinforcing phase, the spreading behavior of steel droplets on TiC substrate was observed by sessile drop method, the element distribution of micro-area between steel and TiC was analyzed by electron probe microanalysis, and the wetting behavior at high temperature was explored with the aid of thermodynamic calculation. Results shows that the wettability between steel and TiC is pretty good, as the molten steel can quickly penetrate into the TiC substrate through the micropores during heating and insulation process. The steel sample collapses and disappears from the observation window. During the penetration, N element can diffuse to the surrounding. No new phase is generated at the interface between molten steel and TiC particles. The predicted binary phase diagram indicates that TiC has a higher solubility in liquid steel than that of TiN, confirming the better wettability of TiC-steel system than that of TiN-steel system. The interface wettability between molten steel and TiC particles is good and there is no chemical reaction at the interface, which ensures that TiC particles can be used as reinforcing phase to improve the wear resistance of steel. The result can provide a guidance for the wettability study between TiC particles and high-titanium steel, and the composition design of high-titanium wear-resistant steel.
		2022 Vol. 57 (9): 75-81 [Abstract] ( 236 ) [HTML 1KB] [PDF 5698KB] ( 349 )

	82	ZHANG Jing, MA Hong-bo, ZHANG Ji, ZHANG Li-feng
		Effect of yttrium content on inclusions in Al-killed titanium-bearing stainless steel
		Taking the T4003 ferritic stainless steel as research object, the inclusions in the stainless steel with measured yttrium mass percent of 0,0.007 0%,0.014 0%,0.023 0% were analyzed by thermodynamic calculation and laboratory experiments. The effect of yttrium content on inclusions in the ferritic stainless steel was studied. The influence of different yttrium contents on inclusions in steel was summarized. The types of inclusions in the steel were predicted by calculating the Gibbs free energy change of inclusions that may be generated in the experimental steel, and the variation of Gibbs free energy change with temperature of different inclusions in the experimental steel with different yttrium contents was summarized. Then, the actual inclusions in the experimental steel were observed by scanning electron microscopy, and the observation results were compared with calculation results and they achieved consistent. The result shows that inclusions in the stainless steel without yttrium are mainly homogeneous TiN inclusions with non-uniform sizes and a small amount of heterogeneous composite inclusions of Al₂O₃, Mg-Al-O, Ca-Ti-O and TiN. After adding yttrium, inclusions in the steel are mainly small-size TiN and part complex inclusions with TiN wrapping around Y₂O₃ and Y₂O₂S. With the increase of yttrium content in steel, the total content of inclusions in steel increases first and then decreases, and the average diameter of inclusions decreases first and then increases. With the increase of yttrium content in the steel, the modification path of oxide inclusions is MgAl₂O₄-CaO-TiO_x → MgAl₂O₄-Y₂O₃-(CaO-) TiO_x→Y₂O₃-TiO_x→Y₂O₃-Y₂O₂S as well as Y₂O₃ and Y₂O₂S. The number density and area fraction of TiN inclusions in the experimental steel first increases and then decreases, and the average diameter first decreases and then increases. Due to the addition of yttrium, the number of TiN inclusions with small size less than 4 μm in the steel increases, but when the amount of yttrium is too high, the refinement of TiN inclusions decreases. Besides, when the mass percent of yttrium in steel is 0.007 0%, 0.014 0%, the size of TiN is obviously refined and the number of large-size TiN decreases remarkably.
		2022 Vol. 57 (9): 82-94 [Abstract] ( 169 ) [HTML 1KB] [PDF 19700KB] ( 313 )

Metal Forming

	95	WANG Zhen-hua, LIU Yuan-ming, WANG Tao, SUN Jie, ZHANG Dian-hua
		Prediction and analysis of rolling force and width spread in rough rolling
		The mathematical model of plate-strip rolling is the basis of automatic control,and the high-precision mathematical model is an important guarantee to improve product quality and market competitiveness. Rolling force and width spread are the key parameters in the hot continuous rolling process control. Their model accuracy not only affects the setting of rough rolling procedures,but also affects the profile of the final strip product. The rectangular slab rolling process of hot continuous rolling was taken as the research object and the three dimensional kinematically admissible weighted velocity field of rough rolling was established for the rolling deformation zone. Considering the width spread effect,based on the first variation principle of rigid-plastic material,the variable upper limit integration method was used to integrate plastic deformation,shear and friction power to get the total power functional of the deformation zone. The theoretical analytical solutions of the rolling force and width distribution were obtained by minimizing the total power functional using the Matlab optimization toolbox. Finally,the slab width spread model and weighted coefficient model of velocity field were obtained by using the data regression of the calculation results of the theoretical analytical model. The rolling force and spread predicted by the model proposed were compared with the on-line measured data and the predicted values of the model established by some relevant scholars. The results verified the accuracy of the model established. The spread model and the expression of velocity field weight coefficient are obtained from the research can be conveniently,flexibly and quickly applied to the rough rolling site,which lays a solid foundation for the production of higher quality hot strip products.
		2022 Vol. 57 (9): 95-102 [Abstract] ( 376 ) [HTML 1KB] [PDF 3008KB] ( 566 )

	103	WANG Xiao-jian, QIAN Sheng, CUI Meng-yu, ZHANG Ji, BAI Zhen-hua
		Stress model and influence factors of sunk roll system in hot dip galvanizing unit
		The stress of sunk roll system of hot dip galvanizing unit is complicated under the working condition of zinc pot,which is greatly affected by the outside. Taking full account of the equipment and process characteristics of the unit. Firstly,the stress of Sunk roll system under working condition was analyzed,and the relationship between the insertion quantity of the corrected roll and the wrap angle of the roll system and an empirical model of roll surface friction coefficient based on the deposition thickness of zinc slag on roll surface were established. Then,the contact pressure model and friction driving moment model of sunk roll system surface were established by strip element discrete method,and the axial end supporting force model and friction resistance moment model of sunk roll system were determined based on the simplified beam model. Finally,the force model of sunk roll system was applied to the galvanizing process section of hot dip galvanizing unit in the domestic,and the influencing factors of the system force were determined in a typical steel strip,and five different levels of production process parameters to analyze the process parameters on the influence law of roll system force condition according to actual working condition and the requirement of flatness,which provided a basis for guidance in process optimization of sinking roll system. The results show that the influences of the four process parameters on the contact pressure and friction moment of the roller system are different,and the contact pressure of the roller surface is nonlinear relationship. The influence of strip tension on the contact pressure of each roller is different,which is the most affected for the sunk roller among three rollers,while the other two rollers are almost not affected by the tension. The average friction coefficient of roller surface and strip speed have little influence on the contact pressure of roller. The friction driving moment of the roller system and the friction resistance moment of the shaft end increase with the increase of the insertion amount of the corrected roller and the average friction coefficient of the roller surface. There is a linear relationship between strip tension and friction driving moment and shaft end friction resistance moment of sunk roll,while strip tension has little effect on the other two rolls. Strip speed has little effect on the friction driving moment and shaft end friction resistance moment of roller system.
		2022 Vol. 57 (9): 103-113 [Abstract] ( 228 ) [HTML 1KB] [PDF 4981KB] ( 373 )

Materials

	114	BAN Jia-le, SHI Zhi-yue, YU Feng, CAO Wen-quan, GUO Yu-zhong
		Effect of double quenching on microstructure and properties of GCr15 bearing steel
		A double quenching process for GCr15 bearing steel is designed. Compared with the conventional heat treatment process,it is found that the tensile strength of GCr15 bearing treated by double quenching process is increased from 2 139.5 MPa to 2 654.5 MPa,and the median fatigue strength of rotary bending is increased from 1 000 MPa to 1 029 MPa. According to the qualitative characterization of the matrix structure,it was found that the structure after the two kinds of heat treatment was acicular martensite. Through quantitative calculation,it was found that the retained austenite content increased from 8.33% to 11.26%,and the dislocation density increased from 2.45×10¹²/cm² to 3.09×10¹²/cm². By means of scanning electron microscope,it is found that the double quenching process does not change the size,quantity and type of inclusions. Through the analysis of the relationship between microstructure and mechanical properties,it is found that the improvement of tensile strength,elongation and high cycle fatigue strength caused by double quenching is mainly attributed to the slow trip effect of retained austenite and the deformation uniformity caused by fine crystallization. Through the analysis of the relationship between microstructure and fatigue properties,it is found that the decrease of low cycle fatigue strength and the increase of high cycle fatigue strength caused by double quenching are mainly attributed to the transformation rate of retained austenite. The rapid austenite transformation leads to the increase of low-cycle stress concentration and the decrease of fatigue strength. On the contrary,the high cycle austenite trip relieves the stress concentration and improves the fatigue strength.
		2022 Vol. 57 (9): 114-122 [Abstract] ( 222 ) [HTML 1KB] [PDF 4140KB] ( 388 )

	123	LI Hua-ying, LIU Guo-xiang, SONG Yao-hui, ZHAO Hai-quan, LI Juan, TIAN Ying-hao
		Hot deformation behavior of antibacterial stainless steel containing 4.35% copper
		Austenitic stainless steel containing copper has excellent antibacterial properties and is widely used in food processing,medical and other fields. However,the addition of copper will significantly affect the processability of stainless steel. The single pass isothermal compression test of 4.35% austenitic antibacterial stainless steel containing copper was carried out by Gleeble-3800 thermal simulation test machine. The high temperature rheological behavior of stainless steel at deformation temperature 900-1 150 ℃,deformation rate 0.01-10 s^-1 and deformation amount 50% was studied. The constitutive equation reflecting the material characteristics is constructed,the microstructure after hot deformation is observed by metallographic microscope,and the microstructure evolution law under each deformation process is analyzed,which provides a theoretical reference for the plastic forming process and microstructure optimization of copper containing stainless steel. The results show that the flow stress of 4.35% Cu-304L steel is sensitive to the deformation process,and the stress decreases with the increase of deformation temperature and the decrease of strain rate. A strain compensated constitutive model based on Arrhenius fifth order polynomial fitting is established by using the stress-strain curve. According to this model the correlation coefficient(R) and average relative error(AARE) are calculated to be 0.972 and 9.03% respectively,indicating that the constructed model can accurately reflect the flow behavior of copper containing stainless steel. Combined with the microstructure,it is found that higher temperature and faster strain rate are conducive to the occurrence of recrystallization. Due to the low deformation energy provided by 0.01 s^-1 low strain rate,there are still initial deformed grains at 1 100 ℃/0.01 s^-1. At 900 ℃/10 s^-1,the grain distortion is serious,and there is an obvious deformation band formed by dislocation stacking,which is easy to lead to cracks. At the strain rates of 1 150 ℃/1 s^-1 and 10 s^-1,the grains are refined and equiaxed,indicating complete recrystallization. Therefore,for 4.35% copper stainless steel,1 150 ℃/1 s^-1 and 10 s^-1 should be considered as its hot working range.
		2022 Vol. 57 (9): 123-129 [Abstract] ( 182 ) [HTML 1KB] [PDF 3569KB] ( 436 )

	130	GU Chen, ZHENG Lei, GE Chen, ZHAO Hong-shan, GUO Long-xin, DONG Han
		Deformation behavior and simulation of 700 MPa steel subjected to TNT buried explosion load
		A new type of 700 MPa explosion-proof steel(BR700) developed by ourselves was taken as the research object,and the blast resistence process of BR700 steel was studied by simulation and orthogonal experimental design. According to the measured quasi-static and dynamic tensile properties,the Johnson-Cook constitutive equation of BR700 explosion-proof steel was fitted. The deformation behavior of 20 mm thick steel plate under 8 kg TNT buried blast load was studied by detonation test. A simulation model was established,and LS-DYNA simulation software was used to analyze the deformation,stress-strain distribution and overpressure. Under the condition of ensuring the accuracy of simulation model,combined with finite element analysis and orthogonal experimental design. Based on the evaluation indexes of deformation D of steel plate,the rule of the parameters affecting on the blast resistence were calculated by using range analysis, such as material yield strength A,strain hardening constant B,strain hardening index n,strain rate constant C and failure strain FS. The results show that the simulation results of deformation of BR700 steel under 8 kg TNT buried blast load can accurately reflect the deformation behavior of BR700 steel without considering the offset of the tool. The error between the simulated results and the actual steel plate deformation is only 7.7%. According to the overpressure analysis of the simulation results,the steel plate has a good energy absorption effect because of its good plastic toughness,which effectively weakens the damage of the explosion shock wave. According to the orthogonal experimental simulation results,the yield strength A of the material has the highest influence on the deformation D of the steel plate after explosion,followed by the strain hardening index n. The increase of material strength can greatly reduce the amount of explosion deformation and effectively reduce the damage of the explosion impact on the vehicle and occupants. At the same time,the effect of strength on anti-detonation deformation was verified by 1 100 MPa steel plate explosion experiment.
		2022 Vol. 57 (9): 130-137 [Abstract] ( 136 ) [HTML 1KB] [PDF 4349KB] ( 302 )

	138	WANG Jin-feng, YUAN Yao, LI Cong
		Microstructures and mechanical properties of laser tailor- welded dissimilar super-high strength steel sheets
		Automotive safety and crash energy absorption have increased the demand for higher strength,energy-absorbing materials and their joining technology. Laser tailor-welded of DP980 dual phase steel and 22MnB5 hot-forming steel is used to investigate the effect of welding heat input on the microstructure and mechanical properties. By keeping the laser output power constant(1.3 kW) and varying the welding speed to control the welding heat input,the relationship between the welding heat input and the microstructure and mechanical properties of the tailor-welded joints was investigated. The microstructure and properties of the different sub-regions of the joint were examined using optical microscopy(OM),scanning electron microscopy(SEM),micro-hardness tester and tensile test machine. The results show that when the welding speed varies between 16 and 26 mm/s,a complete and defect-free fusion zone is obtained; as the welding speed increases,not only does the weld surface depression gradually improve,and the width of the weld heat affected zone(HAZ) also decreases. Hardness tests indicated the presence of softened zones in the joint,mainly in the tempered zone and incomplete phase transformation region of the heat affected zone on the DP980 side,while the fine grain zone, coarse grain zone,heat affected zone of 22MnB5 and weld metal zone of DP980 together formed the hardened area of the joint. Furthermore,the tensile strength of the welded joints remained between 576 and 597 MPa,with the corresponding fractures occurring in the base metal zone of 22MnB5 and accompanied by significant necking. The post-break elongation of the joints ranged from 11.9% to 15.5% between the post-break elongation of the DP980(11%) and the 22MnB5(22%). The study also showed that the greater the heat input during welding,the coarser the microstructure of the same area of the joint.
		2022 Vol. 57 (9): 138-147 [Abstract] ( 140 ) [HTML 1KB] [PDF 7319KB] ( 329 )

	148	ZHANG Hong-liang, GONG Wei, JIANG Zhou-hua, WANG Peng-fei
		Effect of magnesium on precipitation of primary carbide in GH3625 alloy
		The mass percent of carbon in GH3625 alloy is about 0.05%. Because of the high content of Nb, Mo and Cr, carbides of MC, M₆C and M₂₃C₆ type will be formed in the alloy, and carbide segregation will easily occur due to the selective crystallization during solidification. Because of high redissolution temperature, carbide is difficult to eliminate in the wrought temperature range, which will lead to the problem of carbide banded aggregation in alloy bars and have a great influence on its service performance. Thermodynamic software of Thermal-calc was used to calculate and analyze the equilibrium precipitated phase and precipitation law of primary carbide in GH3625 alloy. The effect of Mg on the morphology, size and distribution of primary carbide in GH3625 alloy was studied by metallographic microscope and scanning electron microscope. The results show that the matrix of GH3625 alloy is a single austenite phase, and MC carbide, as a high temperature precipitated phase, precipitates directly from the liquid phase, which is rich in Nb, followed by a small amount of Ti, Mo and other elements. With the decrease of solidification temperature, the mass percent of Nb gradually increases. When Mg is not added, a large number of strip-shaped primary carbides are precipitated between secondary dendrites in GH3625 alloy, and their average diameter and area are large. After adding 0.014% Mg, Mg not only improves the distribution and morphology of carbides at interdendritic and grain boundary, but also reduces the size of primary carbides by changing the specific interfacial energy relationship between carbide phase and matrix phase. When the mass percent of Mg increases to 0.037%, the distribution of primary carbides is more uniform and dispersed, and the effect of refining and spheroidizing carbides by Mg is the best. At the same time, under the conditions of water cooling and air cooling, the cooling rate of experimental alloy is higher than that of furnace cooling, and the size of primary carbide precipitation is relatively smaller.
		2022 Vol. 57 (9): 148-155 [Abstract] ( 178 ) [HTML 1KB] [PDF 5097KB] ( 364 )

	156	WANG Gang, LU Liu-cheng, ZHANG Yue, WANG Shu-yan, CUI Chao
		Cyclic characteristics of surface-modified layers of 18CrNiMo7-6 alloy steel
		In order to study the constitutive characteristics of the surface-modified layers of 18CrNiMo7-6 alloy steel under cyclic loading,18CrNiMo7-6 alloy steel was carburized and heat treated. Round bar samples with different surface modified layer thickness were obtained through chemical corrosion. Monotonic tensile test and cyclic loading test were carried out respectively to analyze the differences of mechanical properties,hysteretic properties,energy consumption capacity and microstructure. The skeleton curve under cyclic loading was fitted,and the difference between its mechanical properties and that under monotonic tension was studied. The cyclic constitutive parameters of the surface-modified layers under cyclic loading were calibrated based on the Chaboche cyclic constitutive model,the simulation were verified by the finite element software ABAQUS. The results showed that the hardness, yield strength and tensile strength of the sample increase with the increase of the thickness of the surface modified layer under monotonic tension. Under the same strain amplitude loading,the thicker the surface metamorphic layer was,the greater the response stress was,the lower the energy dissipation coefficient was,and the weaker the energy dissipation capacity of the material was. Ramberg-Osgood model can better fit the cyclic skeleton curve of surface-modified layers under cyclic loading. The main component of 18CrNiMo7-6 alloy steel was lath martensitewith the increase of surface modification layer thickness,the higher the dislocation density was. The matrix material of 18CrNiMo7-6 alloy steel showed the characteristics of cyclic hardening under cyclic loading,and the sample gradually showed the characteristics of cyclic softening with the increase of the thickness of the surface-modified layers. Chaboche cyclic constitutive model can accurately fit the mechanical response of samples with different surface-modified layers under cyclic loading.
		2022 Vol. 57 (9): 156-165 [Abstract] ( 161 ) [HTML 1KB] [PDF 7578KB] ( 348 )

Environmental Protection and Energy

	166	BAO Xiang-jun, WENG Si-hao, CHEN Guang, WANG Jing, CHEN Xu, XIE Jing-cheng
		Comparison on multi-step prediction of blast furnace gas generation based on LSTM/SARIMA time series model
		In order to accurately predict the gas generation amount of blast furnace under normal and variable working conditions (such as wind off, production reduction, production shutdown, etc.) The amount of blast furnace gas generated. The prediction effects of the two models with different prediction steps under normal conditions are compared and that with the increase of the number of prediction steps, the prediction accuracy of the two models generally decreases, and the prediction accuracy of the LSTM model is generally higher than that of the SARIMA model are found. Model accuracy, the prediction effects of different input samples on the model under the condition of 30-step prediction are also compared. The results show that the optimal input sample size of the SARIMA model is about 200, the corresponding average relative error is 0.057 0, and the LSTM model is the best The input sample size is about 100, and the corresponding average relative error is 0.042 8. Therefore, the prediction effect of the LSTM model is better under normal working conditions; while the SARIMA model works better under variable working conditions, and the average relative error of the SARIMA model is 0.069 4, 0.094 0 for the LSTM model. Combining the advantages of the two models, a gradient-driven time series prediction composite model is established. The average relative error of the model's 30-step prediction under the composite working condition is 0.060 1, which is lower than the error when the two models are used alone. Therefore, it is recommended to run in the field. Using the gradient-driven time series prediction composite model for prediction provides better data support for blast furnace gas regulation, rationally distributes gas, improves gas utilization, and reduces gas emission.
		2022 Vol. 57 (9): 166-172 [Abstract] ( 205 ) [HTML 1KB] [PDF 2055KB] ( 465 )

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