IRON AND STEEL

钢铁

Home | About Journal | Editorial Board | Instruction for Authors | Subscriptions | Advertisement | Contacts Us | Chinese

　

Office Online

　

　

　

　

　

　

Editor-in-chief

　

Journal Online

　

　

Forthcoming Articles

　

　

　

　

Download Articles

　

　

Quick Search

Advanced Search

	2023 Vol. 58 No. 10
	Published: 2023-10-15



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

Technical Reviews

	1	LI Haifeng, CHEN Jingran, WANG Xindong, ZHANG Caidong, ZHENG Aijun, WANG Xiaoai
		Technical pathway analysis for low-carbon ironmaking with hydrogen-rich towards long-process
		The long ironmaking process with blast furnace and basic oxygen furnace (BF→BOF) is the leading process of steel production in China. Under the background of "dual carbon", green and low-carbon development has become the core proposition of the transformation and development for the iron and steel industry. At present, the hydrogen metallurgy low-carbon technology route based on hydrogen instead of carbon is mainly adopted at home and abroad, and the domestic route is mainly oxygen-rich BF and hydrogen-based shaft furnace (SF). It promotes the transformation of traditional BF to hydrogen-rich and oxygen and carbon-recycle (Hy-O-CR) technology. Combined with the mechanism of hydrogen metallurgy and the characteristics of the existing typical low-carbon process route, the upper limit of CO₂ emission reduction of hydrogen metallurgy technology route is analyzed. Starting with limiting the key parameters of CO₂ emission reduction in BF, the author puts forward a new ironmaking system and method of reduction smelting furnace (RSF) with Hy-O-CR. The ironmaking system includes many sets of equipment such as reduction smelting furnace, gas dust collector, dryer, CO₂ separator, electrolytic water device, blower, heat exchanger, storage tank of reduction gas, chimney, and other equipment, in which the reduction melting furnace includes an indirect reduction zone, a soft melting dripping zone, and a coke combustion zone from top to bottom. Ironmaking methods include coke and ore mixed charging, injection of the mixed reduction gas composed by electrolytic green hydrogen and circulating gas from the furnace top gas in the indirect reduction zone, injection of oxygen in the coke combustion zone, CO₂ recovery of the furnace top gas, slag and hot metal treatment. By designing the size of new furnace type and optimizing parameters, the metallization rate of ore in the indirect reduction zone is up to 85%-95%, and the carbon consumption per ton of hot metal is greatly reduced. Based on the theoretical calculation of thermodynamics, the relevant physical experimental data and the analysis of CO₂ emission indexes of six typical processes, the feasibility and popularization prospect of the new process are further expounded. Using the full-oxygen method to recycle the reduction gas produced by its own reactor, the process achieves the goal of reducing CO₂emissions by more than 50%, and realizes green and low-carbon metallurgy.
		2023 Vol. 58 (10): 1-11 [Abstract] ( 222 ) [HTML 1KB] [PDF 5465KB] ( 392 )

Raw Material and Ironmaking

	12	CHEN Qigong, PAN Jian, ZHU Deqing, GUO Zhengqi, YANG Congcong, LI Siwei
		Metallization sintering of magnetite pellets
		Under the background of "dual carbon", strengthening blast furnace smelting is one of the important directions to promote low-carbon emission reduction in the ironmaking process. A certain proportion of metallized burden can significantly reduce the coke ratio and increase the productivity of blast furnace. A new process of pre-reduction sintering of iron ore pellets with 100% magnetite concentrate as raw material was proposed. The process parameters of pellet metallization sintering were optimized under the premise conditions of green ball moisture at 7.5%, basicity at 1.0 by burntlime adjustment, drop strength of green ball with 6.0 times/0.5 m, compressive strength of 15.85 N/piece, thermal shock temperature at 500 ℃. The effects of different fuel types and addition methods, total C/Fe mass ratio, fuel distribution ratio, basicity and other conditions on the quality indicators of pre-reduced sinter were investigated. The metallurgical performance of the obtained pre-reduced sinter was evaluated. In addition, the morphology, quantity and composition of the different mineral phases of the resulting pre-reduced sinter were observed and measured.The results showed that under the pellet metallization sintering conditions of bed height of 300 mm, total C/Fe mass ratio of 0.4, internal addition anthracite and external addition bituminous coal, preheating temperature at 450 ℃, the metallization rate and total iron grade of the pre-reduced sinter reached 43.79% and 68.10%, respectively. The yield of pre-reduced sinter was 76.32%, tumble index was 78.10%, productivity was 0.41 t/(m²·h).The ore phase analysis shows that the pellet metallization sintering is mainly composed of metallic iron, fulvic and residual phases and has a high FeO content and a low Fe₂O₃ content. The metallic iron is densely distributed around the fulvic and residual carbon. From the top to the bottom of the column, the content of metallic iron increases, while the content of fulvic and residual carbon shows a decreasing trend. In addition, liquid phase consolidation and metal bonding links are the main consolidation methods for pellet metallization sintering.Total reduction degree of the pre-reduced sinter was 85.79%, reduction strength index and reduction chalking index were 90.82% and 92.52%, respectively, which had excellent low temperature reduction disintegration performance.
		2023 Vol. 58 (10): 12-22 [Abstract] ( 100 ) [HTML 1KB] [PDF 4786KB] ( 475 )

	23	WEN Bao-liang, ZHANG Xiao-ping, LI Jia-xin, WU Hong-liang, YANG Jia-long
		Preparation of fusible pellets from fine-grained iron ore concentrates
		The current research on the pelletization of fine-grained iron ore concentrate mainly focuses on the production of acidic pellets. To further improve the industrial application of fine-grained iron ore concentrate and to relieve the resource pressure of pellet production, the preparation of fusible pellets using fine-grained iron ore concentrate under different methods was investigated. The results show that: the fusible pellets prepared from fine-grained iron ore concentrate with 0.8-1.2 alkalinity and bentonite with limestone have better pellet quality, with a drop strength of 7.3 times/0.5 m and compressive strength of 16 N/pc, while the pellets prepared with slaked lime as binder and flux require an alkalinity greater than 1.0 to meet the production standard. Based on the model fitting results, the molten pellets with bentonite and limestone added to the fine-grained iron ore concentrate had a longer drying completion time than the molten pellets with slaked lime only, which were 360 s and 270 s. Based on the model fitting results, the molten pellets with slaked lime only had a higher water transfer and diffusion coefficient with Bi value less than 0.1, and the temperature distribution inside the raw pellets tended to be uneven during the drying process. Whether bentonite or slaked lime is used as binder for the production of fine-grained concentrate fusible pellets, a higher roasting temperature is required to promote the formation of large continuous crystals between hematite ores, and the strength of bentonite pellets with limestone is 3 656 N/pc and slaked lime pellets is 3 398 N/pc at a roasting temperature of 1 250 ℃. At 0.8-1.2 alkalinity, compared to the addition of bentonite and limestone, the addition of slaked lime only The fine-grained iron ore concentrate fusible pellets with slaked lime will slightly reduce the pellet reduction, but can improve the reduction swelling and reduction pulverization of the pellets, and the fine-grained iron ore concentrate fusible pellets prepared by both methods have good metallurgical properties.
		2023 Vol. 58 (10): 23-33 [Abstract] ( 113 ) [HTML 1KB] [PDF 5079KB] ( 256 )

	34	WANG Xindong, QIE Yana, LÜ Qing, WANG Yifan
		Analysis and comparison of energy saving and emission reduction of blast furnace injection with different hydrogen-rich mediums
		At present, China′s iron and steel enterprises are still based on the long process process of blast furnace-converter, and the Hydrogen enrichment operation of blast furnace is one of the important directions in the development of hydrogen metallurgy in China. There are many kinds of hydrogen rich medium and injection mode, so it is very important to select the hydrogen rich process of blast furnace reasonably and effectively. In order to determine the appropriate hydrogen enrichment process, the concept of "carbon consumption-carbon emission-coke ratio-raceway adiabatic flame temperature operating window" is proposed based on the Rist operating line tool with hydrogen and combined with the calculation of the overall and regional heat balance of blast furnaces. The energy saving and emission reduction effects of blast furnace injection of coke oven gas, natural gas and hydrogen at normal temperature and preheating conditions are compared and analyzed. The results show that coke ratio,raceway adiabatic flame temperature, carbon consumption and CO₂emission all increase with the increase of hydrogen rich medium injection, but the effect of oxygen enrichment rate on these indexes is opposite. In the case of blast furnace without coal injection, the hydrogen rich medium injection technology can reduce carbon consumption and carbon emission, but the coke ratio is still high. By comparing the operation window area size of different hydrogen-rich processes, it is concluded that blast furnace coal powder injection(PCI) + pure hydrogen in blast furnace has higher energy saving and emission reduction. The maximum injection volume and limiting link of different hydrogen-rich technology can be intuitively obtained from the operation window. The results show that the maximum injection amounts of BF PCI + natural gas, BF PCI + coke oven gas and BF PCI + H₂are 128, 359 and 500 m³/t respectively, and the energy saving and emission reduction rate of blast furnace coal injection + 950 ℃ preheating hydrogen is increased by about 20% compared with normal temperature conditions.
		2023 Vol. 58 (10): 34-41 [Abstract] ( 106 ) [HTML 1KB] [PDF 5563KB] ( 302 )

	42	LIU Zhengjian, LU Shaofeng, WANG Yaozu, ZHANG Jianliang, CHENG Qiang
		Operation strategies of gas-based direct reduction shaft furnace with different hydrogen-to-carbon ratios based on numerical simulation
		In order to reduce carbon dioxide emissions and alleviate the greenhouse effect, China puts forward the strategic goals of "carbon neutrality" and "carbon peaking". The iron and steel industry, while being a crucial pillar of the global industrialization process, is also one of the major sources of CO₂ emissions. The traditional process relies heavily on blast furnaces for iron production, which involves the use of coke, coal, and other reducing agents to convert iron oxides, resulting in the release of significant amounts of CO₂ into the atmosphere. Therefore, in order to achieve a "double carbon" target, the steel industry urgently needs to develop low-carbon hydrogen metallurgy technologies. The gas-based shaft furnace process, due to its unique characteristics, utilizes hydrogen-rich gases such as natural gas or coke oven gas as feed gas. These gases undergo reforming reactions to generate a reducing gas, which is then used to reduce iron oxides. This process not only replaces traditional fossil fuels but also produces non-polluting water vapor. Thus, as a low-carbon hydrogen metallurgy technology, the gas-based shaft furnace process has enormous potential to significantly reduce CO₂ emissions in the steel production process and play a crucial role in the future green and low-carbon development of the steel industry. A two-dimensional CFD model of the gas-based shaft furnace was established, and the effects of reducing gas hydrogen-to-carbon ratios, reducing gas temperature and top gas pressure on the gas-based shaft furnace were studied. The results show that increasing the hydrogen-to-carbon ratios (volume percent ratio)of reducing gas and top gas pressure is beneficial to reduce the furnace temperature and restrain the bonding of burden, the hydrogen-to-carbon ratios increases from 1.75 to 100% H₂(volume percent ), the DRI metallization degree decreases from 0.93 to 0.84. Increasing the gas temperature, gas flow rate and top gas pressure can increase the metallization degree of DRI. At the same time, increasing the reducing gas temperature and top gas pressure can also increase the H₂ utilization degree, but increasing the flow rate of reducing gas will lead to the decrease of the H₂ utilization degree.
		2023 Vol. 58 (10): 42-50 [Abstract] ( 162 ) [HTML 1KB] [PDF 3636KB] ( 351 )

	51	LI Hongwei, LI Xin, LIU Xiaojie, LIU Ran, CHEN Shujun, LÜ Qing
		Evaluation model for comprehensive operation condition of vanadium and titanium blast furnace based on big data mining
		The fluctuation of blast furnace conditions have a serious impact on the yield, quality of molten iron and energy consumption in the blast furnace production. A timely and comprehensive overview of blast furnace operating conditions to reduce furnace condition fluctuations is the key to maintaining stable and smooth blast furnace production. Based on the historical data of a vanadium and titanium blast furnace, a comprehensive evaluation model for the blast furnace operation is eastablised with the big data mining. Using the data warehouse of the blast furnace iron-making process, the related production data is collected and integrated, the null values and outliers of the raw data are processed, thus the clean data for the model is obtained. Combined with the process and expert experiences, 33 evaluation indexes characterizing the comprehensive operation condition of blast furnace are selected to carry out the evaluation system of the operation indexes for blast furnace. According to the combination weighting of analytic hierarchy process and entropy weight method based on game theory and the improved TOPSIS method, the AHP_EWM_TOPSIS model is established to evaluate the blast furnace operation. The comprehensive matching rate from the evaluation results verified with the actual production reaches 94.49%, which indicates this model could accurately evaluate the comprehensive operation of blast furnace and provide the timely and effective information for the operators. The statistical analysis of the blast furnace operation is carried out to derive the evolution of that. As the blast furance is operated well, the optimum operational parameters are summarised, which could further provide the operational basis and data support for the optimisation of blast furnace production. This model can quickly judge the real-time operation of blast furnace, and optimize the blast furnace production, as a result, the long-term stable operation of the blast furnace is obtained, and the production purposes include high quality, high production, low consumption, and long life of blast furance are realized.
		2023 Vol. 58 (10): 51-66 [Abstract] ( 92 ) [HTML 1KB] [PDF 6571KB] ( 308 )

Steelmaking

	67	ZENG Li, LUO Yanzhao, LIU Yanqiang, ZHAO Changliang, JI Chenxi, XU Haiwei
		Control technology and source of large-size calcium aluminate inclusions in automobile sheets
		In recent years, the high quality automotive panel users both domestically and internationally have demanded "zero defects" for the cold-rolled steel sheet, galvanized steel sheet, and other products for automotive panels. The appearance of large-size calcium aluminate inclusions in the steel is the main cause of the defects in IF cold-rolled steel plates. In the subsequent stamping process of steel plates, these large-size inclusions may result in cracking during stamping. In order to solve the problem of large size calcium aluminate inclusions in cold rolled IF steel sheet for automobile, the source and control of calcium aluminate inclusions in cold rolled IF steel sheet in a domestic steel plant were studied. Firstly, the morphology and composition of large size calcium aluminate inclusions were analyzed by SEM and EDS, and it was determined that the ladle slag was the main source of calcium aluminate inclusions. The control process research of RH refining top slag modification, ladle slag quantity optimization, high weir in tundish and high level molten steel operation has been carried out. By increasing the w((CaO))/w((Al₂O₃))of slag to reduce the FeO activity in slag, the surface tension of slag can be improved, and the aggregation of Al₂O₃ inclusion particles can be inhibited. High weir structure was established in the tundish, and molten steel sampling analysis found that the number density of larger than 5 μm inclusions is 7.83/mm² and 5.57/mm² front and back of the weir,respectively. When the high liquid level operation of molten steel in tundish is applied, it was found that the average residence time increased by 30.3 s when the liquid level was increased by 140 mm. Based on the above key control measures, the stable control of large size calcium aluminate inclusions in IF steel cold-rolled automobile sheet was achieved, and the defect occurrence rate was reduced.
		2023 Vol. 58 (10): 67-74 [Abstract] ( 144 ) [HTML 1KB] [PDF 3453KB] ( 510 )

	75	ZHANG Tao, WANG Xinhua, WU Zhongyou, LI Jinbo, GAO Fubin, LIU Junshan
		Optimization research on downgrade strategy of transition slabs of thin size and high quality automobile sheet
		Many automobile enterprises recently decreased the thickness of the steel sheet to about 0.65 mm,which resulted in a remarkable increase of cracking defects when large deformation is applied,particularly on the steel sheets produced from the transition slabs in continuous casting. The cracking of the thin gauge automobile sheets were investigated by the high-magnification observation,and composition analysis of the cracking were carried out by scanning electron microscopy and energy spectrum analysis. The flow and mixing characteristics of the molten steel in succeeding heat entered the tundish were analyzed by numerical simulation,and the results find out that the cracking was caused mainly inclusions of Al₂O₃ and calcium aluminates. More cracking occurred on steel sheets made from the transition slabs mainly due to a small amount of liquid steel being oxidized and a few tundish slag drops involved in the liquid steel at the time when the succeeding heat starts casting. The prediction model of the transient slab length was developed,and the applicability of the mathematical model was verified by sampling and analyzing the mixed-casting slabs. The cracking occurred mainly on sheets of the slabs cast within the time when the mass percent of the steel of the succeeding heat reached 20%-80% at the exit of the tundish. The tundish with the flow control structure of double weirs and double dams has the shortest time to produce the transition slabs and the time is 7.33 min. Industrial experiments were carried out based on the research results,and the actual production data of 30 casting sequences were tracked. According to the previous downgrade strategy of transition slabs,84 slabs needed to be downgraded,but through optimization,only 38 transition slabs should be downgraded. The amount of degradation was reduced from 41.38% to 18.72%,while the stamping cracking rate did not increase,and remained the advanced control level at less than 0.025%.
		2023 Vol. 58 (10): 75-84 [Abstract] ( 103 ) [HTML 1KB] [PDF 4654KB] ( 295 )

Metal Forming

	85	WANG Jiaqi, LIU Xiao, ZHANG Zengqiang, WANG Zhenhua, WANG Tao
		Rapid prediction of rolling force of precision thin strip based on non circular arc theory
		Precision stainless steel ultra-thin strip is an important industrial raw material in high-end fields such as microelectronics and micro-forming, High-precision steel strips are generally rolled by multi-roll mills. The rolling force model plays a decisive role in the rolling process control of ultra-thin strip, and the accuracy of the rolling force model is mainly affected by the two parameters of deformation resistance and friction coefficient. In the rolling process, the arc length of the contact deformation zone between the extremely thin strip and the roll is generally much larger than the thickness of the rolled piece. The roll profile is flattened into a non-circular arc profile, and the traditional rolling force model based on the assumption of the arc profile is no longer applicable. In view of the above problems, based on the non circular arc theory, the rolling force model applied to 304 stainless steel strip is developed by deducing the analytical equation based on Fleck theory and computer programming. In order to optimize the rolling parameters and improve the calculation accuracy of the rolling force model, considering that the process characteristics of the ultra-thin strip rolling process are large tension rolling, the yield strength change of the rolled piece is determined by the rolling-tensile experiment and the corresponding deformation resistance model is fitted. The friction coefficient calculation program based on Fleck rolling force model is designed. Combined with the data collected in the rolling process, the friction coefficient model about the change of rolling speed is calculated and fitted in reverse. The data show that during the rolling process of the ultra-thin strip, the friction coefficient decreases with the increase of the rolling speed within a certain range. This is because as the rolling speed increases, the lubricant is more easily brought into the deformation zone, making the oil film lubrication effect in the deformation zone enhanced. The calculation and verification show that the error between the calculated value and the measured value of the model is -10%-10%, which can meet the high efficiency control requirements in the production process.
		2023 Vol. 58 (10): 85-91 [Abstract] ( 95 ) [HTML 1KB] [PDF 1756KB] ( 242 )

	92	WANG Xiaogong, LI Hongbin, KONG Chao, TIAN Yaqiang, LU Jianlong, CHEN Liansheng
		Research and application on threefold regulation of crown distribution in rolling direction of hot-rolled strip
		Due to the temperature difference between the two ends of the strips and the longer rolling time of the thin strips, a significant attenuation of thin strips in rolling direction occurred on the 1 780 mm hot-rolling production line of Chengde Vanadium and Titanium New Material Co., Ltd., affecting the quality of strips. In response to this phenomenon, an analysis was conducted on the site, including the original roller shape of CVC, the lateral displacement setting of work rolls, and the bending force setting of each stand. It was found that the existing process parameters had reached the limit of plate crown control without changing the existing cooling equipment and rolling rhythm. Based on that, the threefold regulation combining original roller shape optimization of CVC, axial shifting control of work roll and dynamic adjustment of bending force is put forward, which provides theoretical guidance and basis for improving the crown attenuation of strips. Based on the three-dimensional metal deformation model and the elastic deformation model of the roll system, a crown control model suitable for the hot-rolled thin strips was constructed in light of the on-site working conditions and process characteristics. Four roller shape optimization schemes were proposed with the goals of F1, F1-F2, F1-F3, and F1-F4, respectively, which then were combined with the lateral displacement of work rolls and the dynamic adjustment of bending force. The effects on longitudinal distribution of crown and the rules of it were analyzed. The results show that with a target crown of (45±15)μm, the crown distribution of strip steel in rolling direction can be 34-45, 37-45, 40-47 and 41.2-49.4 μm respectively using the optimization schemes above. The corresponding attenuations are 11, 8, 7, and 8.2 μm respectively. The bending forces of F1 to F4 are increased by 500, 550, 740, and 680 kN respectively. In addition, the crown attenuation can be reduced from 8 μm to 10 μm after this method is applied to the production line of 1.5 mm×1 250 mm strips.
		2023 Vol. 58 (10): 92-101 [Abstract] ( 100 ) [HTML 1KB] [PDF 5743KB] ( 299 )

Materials

	102	ZHOU Qiang, CAO Yanguang, YANG Gengwei, LI Zhaodong, WAN Guoxi, WANG Wenjun
		Effect of tempering temperature on microstructure and mechanical properties of 700 MPa grade beam steel
		It is common that microalloying elements are not precipitated completely in hot rolled steel. When there are oversaturated solid solution microalloying elements in steel,tempering can precipitate them in the matrix and affect the mechanical properties. The effect of tempering temperature on microstructure and properties of Nb-Ti microalloying hot rolled 700 MPa automobile beam steel was studied by means of SEM,EBSD,TEM and tensile test. The results show that when tempering at 450 ℃ to 600 ℃,the matrix structure of the experimental steel is almost identical to the hot-rolled experimental steel,and it is mainly quasi-polygonal ferrite with slightly larger size. When tempering at 700 ℃,the microstructure of the experimental steel transforms to polygonal ferrite,the grain size increases rapidly,the grain boundary density decreases,and partial recrystallization occurs. When tempering,the oversaturated solid solution Ti and Nb in the hot rolling stage will precipitate in the form of (Ti,Nb)C. The higher the tempering temperature,the shorter the precipitation incubation period of (Ti,Nb)C and the larger the precipitation content. The average particle size will first decrease and then increase. When the tempering temperature is 600 ℃,the average particle size of (Ti,Nb)C is the smallest,only 5.47 nm. The tensile strength,yield strength and elongation increase with the increase of temperature when the experimental steel is tempered in the range of 450 ℃ to 600 ℃. When the tempering temperature rises to 700 ℃,the yield strength and tensile strength of the experimental steel decrease significantly and the elongation increases. When the tempering temperature is 600 ℃,the mechanical properties of the experimental steel are optimal. The tensile strength,yield strength and elongation are 803 MPa,755 MPa and 24.6%,respectively. The strengthening mechanism analysis shows that the yield strength improvement of the experimental steel is mainly caused by the precipitation strengthening of microalloying elements Ti and Nb during the tempering process.
		2023 Vol. 58 (10): 102-110 [Abstract] ( 130 ) [HTML 1KB] [PDF 4811KB] ( 371 )

	111	YAO Sancheng, ZHANG Jian, LIU Xuehua, ZHAO Hai, SHI Na, XU Jun
		Numerical simulation and experimental verification of interrupted quenching (IRQ) for heavy-haul railway wheels
		The non-pearlite mixed microstructure layer containing martensite (M) and bainite (B),which is generated during the heat treatment cooling process of railway wheels,is a potential source of driving faults and hazards. For heavy-haul railway wheels with prominent non-pearlite layer,the finite element numerical model of interrupted quenching (IRQ) was established based on software MSC. Marc and Thermal Prophet,and the influence of IRQ process on temperature field,microstructure and mechanical properties of the wheel was analyzed,and the physical verification was carried out. The simulation results show that during the short quenching interruption period,due to the influence of heat conduction inside the deeper rim,a small temperature platform or temperature return phenomenon occurs near the surface of the wheel tread. The return temperature is lower than the critical point A_c1,which can avoid secondary austenitization,but the tread sub-surface and inside of the rim are slightly affected. IRQ process slow down the temperature drop near the tread surface,and avoid most of the M and B transformation areas. The non-pearlitic layer is inhibited,and its thickness is controlled within 6 mm,so the microstructure near the tread is significantly improved. The interior of the rim has a relatively uniform microstructure with fine pearlite and a small amount of ferrite (P-F),but within a depth range of 10-15 mm from the tread surface,the composition of the microstructure may fluctuate locally,and a small amount of B microstructure may be regenerated in the P-F microstructure. The gradient of strength and hardness distribution from the tread surface of the wheel is reasonable and gradually decreased,and the strength and hardness level of most areas inside the rim is not significantly affected. Due to the pre-cooling effect,the IRQ process improves the average effective cooling rate within the depth range of 15-30 mm from the tread surface,forming a local maximum area of strength and hardness,slightly improving the strength and hardness compared with the traditional process wheel. The physical verification results are basically consistent with the simulation results. After comprehensive evaluation,it is basically feasible to apply IRQ process to control the non-pearlitic microstructure layer of heavy-haul railway wheels.
		2023 Vol. 58 (10): 111-119 [Abstract] ( 88 ) [HTML 1KB] [PDF 6062KB] ( 321 )

	120	WANG Gang, LI Junhao, SANG Xianggang, ZHANG Yue, LI Hao
		Effect of deformation on microstructure and residual stress of 18CrNiMo7-6 carburizing steel
		In order to grasp the deformation behavior of 18CrNiMo7-6 carburizing steel under load,improve material performance,and ensure the reliability and service safety of key components. Axial compression and tensile deformation tests are carried out,the crystal orientation and microscopic interface changes of the deformed sample are analyzed,and the surface residual stress of sample is measured to study the influence mechanism of the microstructure change on the residual stress during the deformation process,and to understand the microstructure,residual stress value and distribution of 18CrNiMo7-6 carburizing steel after deformation. The test results show that during the deformation process,with the increase of applied load,dislocation movement occurs in the carburized layer region of sample,resulting in an increase in the Kernel Average Misorientation and dislocation density,grain refinement,and the proportion of low-angle grain boundaries; the orientation of martensite in the slip system{111}〈110〉 is mainly soft orientation,which is prone to slip. During the quenching process of 18CrNiMo7-6 carburizing steel,due to the transformation from austenite to martensite,an inhomogeneous residual compressive stress field is generated in the carburized layer area. The overall distribution trend of residual compressive stress along the depth direction is gradually increasing first,then gradually decreasing,reaching the maximum value (-224.65 MPa) at a depth of about 900 μm from the surface. The axial deformation has no effect on the overall distribution trend of residual stress along the depth direction. When the sample deformation is -0.25%,-0.50% and -0.75%,the surface axial residual stress relaxes by 3.3%,4.9% and 18.9% respectively. When the deformation is 0.25%,0.50% and 0.75%,the surface axial residual stress relaxes by 1.3%,14% and 27%,respectively. The research results show that when the vector sum of applied stress and residual stress exceeds the local elastic limit of material surface,local plastic deformation will occur,which will cause the change of dislocation density,and then lead to the relaxation of residual stress. The larger the amount of plastic deformation,the more obvious the residual stress relaxation.
		2023 Vol. 58 (10): 120-130 [Abstract] ( 90 ) [HTML 1KB] [PDF 9666KB] ( 251 )

	131	LI Qi, ZHANG Xu, LI Xiaoqing, LI Junru, ZHANG Pengfei, ZHANG Yuxin
		Effect of Nb and Ti on dissolution behavior of delta ferrite in heat-resistant steel
		Delta ferrite is a common harmful precipitated phase in martensitic heat-resistant steel. Its existence will adversely affect the mechanical properties and corrosion resistance of the material,and it is difficult to be removed by conventional heat treatment. Therefore,how to remove delta ferrite is the focus of research in this field. C-Cr-Ni-Mo martensitic heat-resistant steel is taken as the main research object,and three kinds of experimental steels with different compositions of C-Cr-Ni-Mo,C-Cr-Ni-Mo-Nb and C-Cr-Ni-Mo-Ti are designed. By means of OM,SEM and EDS,the effects of Nb and Ti microalloying on the dissolution behavior of delta ferrite in martensitic heat-resistant steel are studied and the mechanism is revealed by comparing the volume percent of delta ferrite,the dissolution rate of delta ferrite and the austenite grain size in the as-cast microstructure of three different composition experimental steels,which provides a new method for the rapid dissolution of delta ferrite in martensitic heat-resistant steel. The experimental results show that Nb and Ti microalloying elements,as ferrite forming elements,will aggravate the segregation of alloy composition and fail to fully transform during the cooling process,resulting in an increase in the volume percent of delta ferrite in the as-cast structure at room temperature,but the size of the generated delta ferrite is relatively small. The dissolution rate of delta ferrite is related to its morphology and position. Nb and Ti microalloying can increase the dissolution rate of delta ferrite. On the one hand,Nb and Ti microalloying will refine the delta ferrite in the as-cast structure and increase the specific surface area of delta ferrite. On the other hand,by forming precipitates containing Nb and Ti,pinning grain boundaries,inhibiting austenite grain growth,delaying the transformation of delta ferrite from irregular shape to spherical shape during dissolution,more delta ferrite is maintained at austenite grain boundaries for a longer time during heating and maintain a large specific surface area,thereby increasing the dissolution rate of delta ferrite.
		2023 Vol. 58 (10): 131-139 [Abstract] ( 122 ) [HTML 1KB] [PDF 4032KB] ( 348 )

	140	WANG Yan, WEI Gang, WEI Yingkang, WANG Jianyong, ZHANG Liangliang, JIA Wenpeng, LIU Shifeng
		Effect of heat treatment on cavitation erosion properties of 17-4PH prepared by selective laser melting
		17-4PH (Precipitation Hardening) stainless steel, as a common material for overflow components such as hydrofoils and turbines, is seriously damaged by cavitation, which causes many safety problems. There are limitations in the traditional process of preparing irregular and complex structural components. In contrast, additive manufacturing technology is a very efficient way of processing such parts. 17-4PH stainless steel was prepared by selective laser melting (SLM). The influence of solution+aging treated (1 040 ℃/1 h+480 ℃/4 h) and ion nitriding on the microstructure and cavitation properties of 17-4PH stainless steel prepared by SLM was studied. The results show that due to the characteristics of rapid cooling and directional solidification of SLM, a large amount of residual austenite is retained in the deposited state, including the columnar crystal and cellular structure in the molten pool along the construction direction. After solution+aging treatment, the original molten pool boundary disappears, the structure is equiaxed crystal, and the strengthening phase precipitates. After ion nitriding treated, a hard layer of nitride of about 20 μm is formed on the surface of the sample. After ion nitriding treatment, the relative content of residual austenite in the sample decreased from 13.1% in the deposited state to 7.5%. In addition, nitrogen infiltration into the matrix material also causes lattice distortion, resulting in a significant shift in the diffraction peak. When cavitation damage occurs, crack initiation and propagation take precedence at the overlap of the melting channel. After solution + aging treated, the cavitation quality is reduced from 7.4 mg as deposit to 5.9 mg after 8 h cavitation damage due to elimination of the melting pool and the boundary of the melting channel and precipitation of the strengthened phase. After nitriding treatment, a hard nitride layer can be formed on the surface of the sample to further improve the cavitation resistance, cavitation damage causes minimal damage to the surface of the sample, resulting in minimal material detachment and a loss of only 5.5 mg of cavitation mass.
		2023 Vol. 58 (10): 140-150 [Abstract] ( 113 ) [HTML 1KB] [PDF 9747KB] ( 321 )

Environmental Protection and Energy

	151	TONG Shuai, AI Liqun, HONG Lukuo, LI Yaqiang, SUN Caijiao, WANG Xufeng
		Prospects of microwave-hydrogen synergistic reduction in steel industry
		Under the background of "carbon peaking" and "carbon neutrality" advocated by the state,the steel industry urgently needs to develop and apply green and low-carbon frontier technology,and the current hydrogen metallurgy technology is an important direction for the development of the steel industry,which has received extensive attention at home and abroad. Hydrogen metallurgy is a new type of metallurgical technology,using hydrogen as a reducing agent,which can achieve an efficient,environmentally friendly and energy-saving metallurgical process. In recent years,microwave technology,as a new heating method,has been widely used in the field of metallurgy,with significant characteristics such as accelerating the reduction reaction,improving metallurgical efficiency,and cleaning and environmental protection. Based on the advantages of hydrogen metallurgy technology and microwave technology to examine the energy structure of ironmaking from the perspective of the ternary relationship of "carbon-electricity-hydrogen",and proposes a new reduction method combining microwave and hydrogen-"microwave-hydrogen co-reduction",which has higher reaction rate and lower temperature requirements,can achieve precise control and optimization of the reaction process,and is expected to become one of the important technologies in the field of hydrogen metallurgy. Under the strategic goal of "dual carbon",combined with the current situation of domestic steel carbon emissions,the research progress of hydrogen metallurgy technology at home and abroad is first reviewed,mainly including blast furnace hydrogen-rich reduction,hydrogen-rich base reduction,hydrogen-rich fusion reduction and plasma hydrogen reduction. The application status and mechanism of microwave technology in the field of metallurgical melting were analyzed. Secondly,the research progress of new microwave-hydrogen co-reduction methods and some problems in the development process are introduced,which provides new ideas for the development of hydrogen metallurgy technology. Finally,the potential value of the new microwave-hydrogen co-reduction method in the field of hydrogen metallurgy in the future is discussed,and the long-term prospect is put forward for promoting the development of the new reduction method.
		2023 Vol. 58 (10): 151-162 [Abstract] ( 92 ) [HTML 1KB] [PDF 4417KB] ( 324 )

	163	DU Xueqiang, LI Xiuping, ZHOU Jicheng, SHANGGUAN Fangqin
		Energy consumption analysis and energy efficiency evaluation of iron-making system
		The energy conservation progress of steel industry in China has gone through several stages, such as single equipment energy conservation, system energy conservation and the popularization of major energy-saving technologies,to the current stage of energy flow network operation and improving energy conversion functions. The energy conservation of steel industry in China has made remarkable achievements. The energy conservation and emission reduction situation faced by the steel industry is becoming increasingly severe. In recent years, although the comprehensive energy consumption per ton of steel has still been reduced, the decrease has been very small, and even rebounded slightly in some years. Under the current theory and technologies, it is an obvious fact that the energy saving potential is decreasing, and it is very important to accurately determine the possibility and potential of energy saving. The pre-ironmaking system is the most significant energy consumption system of the steel manufactory process. Therefore, the pre-ironmaking system energy consumption is analyzed as an example, and the concepts of minimum energy consumption and standard energy consumption are proposed. Based on factory practice, the basis for determining ideal operating condition and standard operating condition, as well as the calculation method of theoretical minimum energy consumption and standard energy consumption are provided. The theoretical minimum energy consumption and standard energy consumption, as well as the actual energy consumption and standard energy consumption, are comparatively analyzed. Based on the analysis of the differences between ideal operating condition and standard operating condition, as well as between actual operating condition and standard operating condition, the ways and directions for energy saving for the coking process, sintering process, and iron-making process are provided respectively; Using the e-p analysis method under the theory of system energy saving, the influencing factors of the pre-ironmaking system, such as the system structure, the equipments scale, the raw material and fuel conditions, the energy-saving technology application, and the energy flow network are analyzed; and the measures and directions of energy conservation are proposed. The research results can provide theoretical support for the reasonable evaluation of the energy-saving potential of the pre-ironmaking system in the steel industry.
		2023 Vol. 58 (10): 163-171 [Abstract] ( 121 ) [HTML 1KB] [PDF 2063KB] ( 487 )

	172	KANG Yue, ZHANG Yuzhu, LIU Chao, XING Hongwei, SUN Ruijing, PEI Jingjing
		Mechanism of mineral composition on effect of blast furnace slag granulation
		As the main by-product in the ironmaking process, the blast furnace slag (BFS) crystallization capacity determines its potential as an active material. The higher the amorphous phase content, the stronger the activity of the BFS. The gas quenching process can effectively prepare high content amorphous slag beads as increasing the BFS cooling rate, which improves the BFS added value utilization. The BFS mineral phase evolution process is explained and the mineral phase precipitation mechanism is analyzed in the continuous cooling process through the thermodynamic simulation and in-situ observation method, which determines the initial crystallization temperature, initial crystal phase and critical cooling rate. At the same time, the crystallization activation energy and Avrami index are calculated to obtain the BFS composition which is conducive to inhibiting the mineral phase precipitation in the granulation process. The results show that, the initial crystal phase of the BFS with the basicity range of 0.9-1.3 are all gehlenite in the continuous cooling process. The initial crystallization temperature gradually increases and the precipitation amount of melilite increases with the increase of basicity, but a part of the melilite begins to change into dicalcium silicate when the basicity increases to 1.2. At the same time, the increase of basicity inhibits the precipitation of anorthite and augite, but has little effect on the precipitation of spinel. The BFS crystallization critical cooling rate gradually increases, the Avrami index gradually increases, and the crystallization activation energy gradually decreases with the increase of basicity. Therefore, high basicity BFS requires large overcooling to inhibit the mineral phase precipitation, which is conducive to obtaining high content amorphous slag beads. At the same time, the slag beads is prepared by gas quenching BFS with different basicities. The amorphous phase content increases and the transparency degree of slag beads gradually increases with the decrease of BFS basicity, and the amorphous content is higher than the national standard GB/T18046-2008 which the mass percent of slag amorphous phase should not be less than 85%, which provides a theoretical basis for the BFs high added value resources and waste heat efficient utilization.
		2023 Vol. 58 (10): 172-182 [Abstract] ( 102 ) [HTML 1KB] [PDF 6615KB] ( 305 )

钢铁

　

News

　

　

·

·

·

·

·

　　　　　　　　　　More

　

Author Center

　

　

Instruction for Authors

　

　

Copyright Agreement

　

Links

　

·	Links

　　　　　　　　　　More

Copyright © IRON AND STEEL　
Supported by: Beijing Magtech