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	2022 Vol. 57 No. 8
	Published: 2022-08-15



	Technical Reviews Raw Material and Ironmaking Steelmaking Metal Forming Materials Equipment Technology

Technical Reviews

	1	YANG Li-bin
		China steelmaking technology progress in the 13th five-year plan and prospection
		During the 13th Five Year Plan period,the rapid development of China′s steelmaking technology has made great progress in mechanism innovation,key process technology and equipment research,high-quality steel high-efficient production,intelligent control,low-carbon and green development and so on. Crude steel output of China continues to increase,which has reached 56.49% of the total output of world. The stable production of high-quality steel provides a guarantee for China′s rapid economic development. The progress of steelmaking science and technology during the 13th Five Year Plan period has been reviewed and summarized in this paper. The key technical achievements has been summarized into two aspects: "development and application of key technologies of high-quality steel steelmaking and continuous casting" and "research and development of clean steel efficient and green steelmaking and continuous casting technology". "Development and application of key technologies of high-quality steel steelmaking and continuous casting" mainly includes: the development of high-quality stainless-steel deoxidization and inclusion control technology, thin slab continuous casting and rolling production technology of electrical steel, heavy axle steel metallurgy technology, high-speed and heavy-load railway rail steel steelmaking technology, special varieties of high alloy steel smelting and continuous casting key technology; The main development of "research and development of clean steel efficient and green steelmaking and continuous casting technology" is reflected in: large converter high efficiency, green smelting key technology, green electric furnace high efficiency smelting technology, high quality special steel green and efficient electroslag remelting key technology, high quality steel high efficiency continuous casting technology. To realize the independent guarantee of key steel materials it is an important task for the steel industry to accomplish innovative development. Combined with the development needs and position of the "14th five-year plan", the key development directions of steelmaking technology in the future include should be summarized 4 points which include innovation and application of efficient and collaborative production technology of clean steel steelmaking and continuous casting, integration and application of intelligent control technology of steelmaking and continuous casting, application of low-carbon and green production technology and near final continuous casting and rolling technology.
		2022 Vol. 57 (8): 1-10 [Abstract] ( 531 ) [HTML 1KB] [PDF 2076KB] ( 712 )

	11	ZHANG Fu-cheng, KANG Jie
		Progress in scientific research of interfaces in steel (Ⅰ)
		Interfaces in steel,including grain boundaries and phase boundaries,differ significantly in structure and chemical composition from the bulk phase. They are also energetically specific and have a very important influence on the phase transformation mechanism and service performance of steel. In recent years,the rapid development of materials analysis and testing methods,combined with techniques and methods such as first principles and finite element simulations,have led to further insights into the science of interfaces in steel and a richer and more varied body of research in this area,with numerous results. An overview of domestic and international research developments in the regulation of microscopic solid-solid interfaces in steel was provided,covering both grain boundaries in single-phase steels and phase boundaries in multi-phase steels. A brief overview of the formation mechanisms of various interfaces in steel is given,and the energy differences,orientation differences and stress distribution of different interface types are discussed. Focusing on the control of interfacial quantity,interfacial structure and interfacial segregation,the influence of interface control methods,such as heat treatment,deformation and forming methods,on the formation of the final interface structure and chemical composition segregation is discussed. The application of advanced technical methods to characterize the interface structure and interfacial composition segregation is introduced. Finally,the future development trends of interfaces are predicted in terms of interfacial controlling methods,computer simulations and technical characterization methods.
		2022 Vol. 57 (8): 11-29 [Abstract] ( 176 ) [HTML 1KB] [PDF 10686KB] ( 629 )

Raw Material and Ironmaking

	30	GUO Jun, CHU Man-sheng, TANG Jue, LI Feng, LIU Zheng-gen, BAO Ji-wei
		Exergy analysis of blast furnace using iron coke
		China′s iron and steel production is mainly based on the long process of BF-BOF with high energy consumption and high emission, which has great pressure on energy conservation and emission reduction. Therefore, it is particularly important to actively develop blast furnace low-carbon ironmaking technology and promote CO₂ emission reduction in blast furnace process. Iron coke is a new type of carbon-iron composite burden after coking or carbonization by adding iron-containing raw materials into suitable coal. Its high reactivity can significantly reduce the temperature in the heat reserve area and then reduce carbon consumption. Using proper iron coke in blast furnace can realize energy saving and carbon reduction to a certain extent. Based on the field production data, the model of iron coke used in blast furnace was established by the theory of exergy analysis, and the influence of iron coke addition on material consumption and energy utilization efficiency of blast furnace was explored. The results show that after using of iron coke in blast furnace, indirect reduction in blast furnace is developed, carbon utilization rate is improved, ash content in blast furnace is reduced, and carbon consumption per unit pig iron and slag amount are reduced. Compared with no iron coke, carbon consumption per ton iron and slag amount are reduced by 25.95 kg and 11.28 kg respectively after using 114 kg/t iron coke in blast furnace. In addition, the metallic iron in iron coke only needs to be melted, which saves the exergy amount required for reduction, and the exergy amount brought by coke and blast will be significantly reduced, so the total exergy amount consumed per ton of iron in blast furnace smelting will be reduced, at the same time, the heat transfer in the furnace will be improved, and the internal exergy loss will be effectively reduced. Compared with no iron coke, after using 114 kg iron coke in blast furnace, the target exergy efficiency increases from 46.14% to 48.87%, and the thermodynamic perfection increases from 87.46% to 88.02%. Under these conditions, the internal exergy loss per ton of iron in blast furnace is reduced by 192.63 MJ, and energy saving is achieved by 6.57 kg.
		2022 Vol. 57 (8): 30-38 [Abstract] ( 239 ) [HTML 1KB] [PDF 2243KB] ( 496 )

	39	FU Xiao-wei, LU Ming, HE Zhi-jun, PANG Qing-hai, YANG Li-chun
		Effect of CO₂-H₂O mixed gas on depth reaction of tamping coke and top charging coke
		With global warming in recent years, CO₂ emission reduction has gradually become a hot spot of concern. The iron and steel industry, as a large CO₂ emission producer, needs to strictly control its CO₂ emissions. Hydrogen-rich ironmaking has become the future development trend of metallurgical processes due to the characteristics of reducing carbon emissions. However, the use of hydrogen-rich fuels will generate a large amount of water vapor in the blast furnace. Therefore, it is very important to study the changes of different types of coke and CO₂-H₂O mixed gas in the gasification and dissolution loss reaction, which can provide a theoretical basis for the selection and quality control of coke under the condition of hydrogen-rich smelting in blast furnace. By studying the deep gasification and dissolution reaction of tamping coke and top charging coke when gases with different CO₂-H₂O contents enter the tubular furnace, the difference of dissolution loss in gasification reaction caused by the change of water vapor content in CO₂-H₂O mixed gas was analyzed, the change law of coke organic functional groups and carbon structure was studied, and the restrictive links in the reaction process was analyzed by unreacted nuclear model. The research shows that the limiting link of the two kinds of coke gasification reaction is the interface chemical reaction. By comparing the differences of edge, middle, central gap structure and relative density in the gasification dissolution process for tamping coke and top charging coke particles, it is found that with the increase of water vapor content in CO₂-H₂O mixture gas, the surface dissolution reaction of two kinds of coke is more serious than the other two parts and there is obvious opening phenomenon. The internal cracking of tamping coke is more serious. Combined with FT-IR analysis, water vapor can aggravate the consumption of aliphatic functional groups and methyl groups in the structure of top charging coke and tamping coke during gasification reaction, resulting in the increase of aromaticity of the two kinds of coke. At the same time, the condensation degree of aromatic hydrocarbons in tamping coke samples increases after reaction.
		2022 Vol. 57 (8): 39-49 [Abstract] ( 164 ) [HTML 1KB] [PDF 5531KB] ( 381 )

	50	WANG Yu, FAN Ying-jie, CHAI Yi-fan, WANG Yi-ci, LUO Guo-ping, AN Sheng-li
		Changes in thermal performance of coke in blast furnace smelting process of Bayan Obo mine
		Metallurgical coke has become one of the necessary raw materials for modern blast furnace ironmaking technology. It is known as the "basic food" of the iron and steel industry, and has important strategic value and economic significance. With the advent of low-carbon era and the application of large-scale coal injection technology, the functions of coke have been gradually replaced. In order to ensure the air permeability and liquid permeability in the furnace, as the "louver" of blast furnace reflow belt, its role as the material column skeleton and channel is more prominent. Therefore, a deep understanding of thermal performance changes of coke in the smelting process of Bayan Obo mine is significantly important to guide its efficient smelting. The feed coke and tuyere coke were taken from No.4 blast furnace in Baotou Steel as the research object. X-ray diffractometer, thermogravimetric vertical furnace, scanning electron microscope, energy spectrometer and other analysis methods were used. The differences in the basic characteristics, main phases of ash, coke reaction index(CRI), coke strength after reaction (CSR), microscopic pore structure, and the content and distribution of alkali metals were compared and analyzed. Finally, the thermal performance of coke in the smelting process of Bayan Obo mine were obtained. The results show that the coke in the blast furnace undergoes a gasification reaction during descending process, ash content increases, volatile matter content decreases, and SiO₂ content decreases significantly, but the content of basic oxides such as CaO, K₂O, Na₂O, and MgO increases. In the early stage of secondary heating, nitrogen adsorption occurs in the coke, and the quality does not decrease but increases. In the later stage, the coke undergoes carbon gasification reaction, and the quality decreases rapidly, reactivity of tuyere coke is improved, and strength after the reaction is reduced. There are honeycomb-like pores on the surface of tuyere coke, and distribution of pore is uneven. In particular, the coke matrix eroded by slag and iron has rough pore walls, and the pores appear to merge. Alkali metals are enriched in tuyere coke, the content of alkaline oxides is increased. The half-width of (002) diffraction peak corresponding to the tuyere coke graphite carbon is sharply reduced, flat peak disappears, and the peak shape is sharp. The crystal structure tends to be ordered, and the degree of graphitization increases.
		2022 Vol. 57 (8): 50-59 [Abstract] ( 122 ) [HTML 1KB] [PDF 5932KB] ( 529 )

	60	ZHAI Xiao-bo, ZHENG Jun, WANG Gang, ZOU Zhong-ping, ZHOU Heng
		Mechanism on behaviors of iron ore dissolution and sintering melt flow
		During iron ore sintering, iron ores dissolve partially into sintering melt, which has a direct effect on the properties of melt, and hence the bonding of sinter. In order to clarify the interaction between iron ore and sintering melt, adhering fines of calcium ferrites existing in forms of Ca_3.6Fe_14.4O_25.2 and CaFe₂O₄ were prepared by calcination of chemical pure reagents. The behaviors of iron ore dissolution and sintering melt flow were studied through laboratory sintering method on the sintering couple composed of seven kinds of nuclei ore and adhering fines of calcium ferrites (w(CaO)=15%). Based on this, chemical compositions of nuclei ore were simulated using chemical pure reagents, and therefore the influence law of SiO₂ contents and Al₂O₃ contents in nuclei ore on horizontal flow area of melt and dissolution index of nuclei ore as well as its mechanism were explored. The results show that when nuclei ore dissolves into CaO-Fe₂O₃ system liquid phase, the interaction region is formed. After the minerals in iron ore, especially quartz, dissolves into the melt, complex CaO-Fe₂O₃ system liquid phase is formed at the area near the melt. At the same time, simple CaO-Fe₂O₃ system liquid phase is transformed into CaO-Fe₂O₃-SiO₂ system liquid phase at the area near nuclei ore. As the main minerals, calcium ferrites and hematite precipitate at the area near the melt, while silicates and hematite precipitate at the area near nuclei ore. With increasing of SiO₂ content in nuclei ore, on the one hand, the amount of SiO₂ dissolved into the melt increases, resulting in raising of dissolution index of nuclei ore. On the other hand, the viscosity of simple CaO-Fe₂O₃ system liquid phase is increased, resulting in reducing of horizontal flow area of melt. With increasing of Al₂O₃ content in nuclei ore, amount of Al₂O₃ dissolved into the melt increases, which decreases horizontal flow area of melt, but increases dissolution index of nuclei ore. Al₂O₃ in nuclei ore has stronger influence than SiO₂ on the behaviors of iron ore dissolution and sintering melt flow.
		2022 Vol. 57 (8): 60-68 [Abstract] ( 151 ) [HTML 1KB] [PDF 5496KB] ( 377 )

Steelmaking

	69	ZENG Yi-bin, BAO Yan-ping, ZHAO Jia-qi, WANG Min
		Formation and evolution of magnesia-alumina spinel in Si-Mn deoxidized 55SiCr spring steel
		The 55SiCr spring steel produced by a steel mill adopts silicon-manganese deoxidization process, but there are a lot of spinel inclusions in its smelting process, which is very unfavorable to the final product performance. Hard and brittle inclusions are one of the main factors during fatigue fracture of spring in service, so in order to clarify the source of spinel inclusions in spring steel and then control and remove non-metallic inclusions in steel, the evolution of inclusions and formation mechanism of main inclusions in 55SiCr spring steel during smelting were analyzed by means of automatic inclusion analysis, scanning electron microscope and energy spectrum analysis, combined with FactSage thermodynamic calculation. The analysis results show that the number of inclusions in the steel after LF refining increases greatly, and its average composition tends to the high melting point region in the ternary phase diagram of SiO₂-Al₂O₃-CaO. The inclusions are mainly SiO₂·Al₂O₃·CaO·MgO, mostly in the form of calcium aluminate-wrapped or semi-wrapped spinel composite inclusions, and a small amount of single spinel inclusions exist in steel. Thermodynamic calculation of formation and evolution for above inclusions shows that increase of Mg and Al content in molten steel will lead to the precipitation of a large number of spinel inclusions in steel and combine with liquid inclusions to form Mg-containing multiphase inclusions. At the same time, the change of molten steel composition will also lead to the substantial increase of MgO and Al₂O₃ contents in SiO₂·Al₂O₃·CaO·MgO inclusions generated during refining, and the spinel phase will be precipitated in the composite inclusions. Therefore, in order to reduce the formation of spinel-like hard and brittle inclusions in Si-Mn deoxidized spring steel, it is necessary to control the contents of Mg and Al in the steel strictly and reduce the contents of MgO and Al₂O₃ in the inclusions as much as possible, so as to realize the plastic control of non-metallic inclusions in spring steel.
		2022 Vol. 57 (8): 69-77 [Abstract] ( 171 ) [HTML 1KB] [PDF 4484KB] ( 361 )

	78	LÜ Ming, CHEN Shuang-ping, LI Hang, ZHANG Zhao-hui, LI Tao, LIU Kun-long
		Changes of blowing characteristics for worn supersonic oxygen lance nozzle in converter
		The oxygen lance nozzle of converter will be eroded to different degrees with the increase of lance age. In order to investigate the influence of oxygen lance erosion degree on the supersonic gas jet blowing characteristics, a three-dimensional full-size geometric model of 120 t converter and a supersonic oxygen lance were established, and the effects of different wear angles for oxygen lance nozzle on the gas jet characteristics, molten bath velocity, and wall erosion were studied. It is found that with the increase of wear angle, the jet velocity decays faster, the length of jet core area and the same isovelocity line are shortened, the maximum velocity of jet center and the distance from the maximum velocity point to the center increase. Dynamic pressure decay rate increases with increasing wear angles, the wear angle increases from 0 to 20°, the maximum dynamic pressure at 1.5 m from lance tip is reduced by 14.84%, and the 14 000 Pa isobaric envelope area is reduced from 0.038 m² to 0.002 m². The area of high-velocity zone at the liquid steel surface decreases with increasing wear angles, while the area of dead zone increases with increasing wear angle. The high-velocity area of longitudinal section for molten bath is mainly distributed near the impact dent and bottom blowing element, the low-velocity area is mainly distributed at the bottom of molten bath, and the dead zone is mainly distributed in the center of molten bath bottom and the lower part of furnace wall. In the depth range of 0.6 m below molten steel surface, the top blown oxygen jet plays a major role in the stirring of molten bath, the stirring ability of molten bath becomes weaker with the increase of wear angle, and the area of high-velocity zone decreases, while the area of low-velocity zone and dead zone increases. When the depth of molten bath exceeds 0.6 m, the bottom blowing airflow plays a major role in the stirring of molten bath, and the area of high-velocity zone is basically unchanged. The shear stress is concentrated in the slag-metal interaction area, the connection between furnace wall and bottom, and the wall near the bottom blowing stream, thus the erosion of refractories is serious. The turbulent kinetic energy and shear stress of fluid near the molten bath wall decrease with the increase of wear angle, and the erosion velocity of converter lining decreases.
		2022 Vol. 57 (8): 78-88 [Abstract] ( 154 ) [HTML 1KB] [PDF 9267KB] ( 371 )

	89	ZHAO Jin-xuan, XIAO Feng, ZHAO Bo, LI Xiang-chen, WU Wei, WU Wei
		Application of circular seam bottom blow gas supply element in extracting vanadium from vanadium-containing hot metal
		In order to solve the problem of residual vanadium in semi-steel and high metal iron in slag caused by the poor stirring ability of molten bath for vanadium extraction furnace, a circular seam bottom blow gas supply element was adopted in the process of vanadium extraction from vanadium-containing hot metal in vanadium extraction converter. A bottom blow process suitable for vanadium extraction from hot metal was developed, and industrial trial was carried out. Through investigation, it is found that the capillary-type gas-permeable brick has the problem of low bottom blowing stirring intensity and easy blockage during use of vanadium-extracting furnace. Change the capillary-type gas-permeable brick to circular seam bottom blow gas supply element. On this basis, the appropriate bottom blowing and top blowing process modes for vanadium extraction were determined by numerical simulation calculation and cold state simulation experiment, and the industrial test plan was formulated accordingly. The numerical simulation results show that with the increase of distance between the bottom blow gas supply element and the center of furnace bottom, the percentage of dead zone in the molten bath increases. The best opening position of the bottom blow element is selected at 0.45D from the center of the working layer (D is the diameter of the molten bath). The results of water model experiment show that under the condition of top blowing flow rate of 11 000-15 400 m³/h, the suitable bottom blowing gas supply intensity is 0.05-0.08 m³/(t·min). Industrial test results show that after optimization of bottom blow process, the average values of vanadium and carbon mass percent in the semi-steel are 0.033% and 3.35%, respectively, the former is 0.004% lower than that before the process optimization, and the later increases by 0.1%. The average values of vanadium oxide mass percent and metallic iron mass percent in vanadium slag are 18.99% and 22.25%, respectively. Compared with the process before optimization, the vanadium oxide mass percent increases by 0.67% and the metallic iron mass percent decreases by 3%. This shows that after the process is optimized, the stirring conditions of molten bath are improved, and the vanadium oxide reaction is more complete. The practice has proved that the circular seam bottom blow gas supply element has the characteristics of high bottom-blowing strength, easy maintenance, not easy to be blocked, safe and reliable, and is suitable for the process of vanadium extraction from hot metal in vanadium extraction converters.
		2022 Vol. 57 (8): 89-93 [Abstract] ( 127 ) [HTML 1KB] [PDF 1955KB] ( 315 )

	94	ZHENG Wan, KOU Jin-rong, LI Lie-jun, WANG Guan, WAN Xiang, LIU Chen-sheng
		Mechanisem of reduction of subcutaneous cracking susceptibility in niobium-containing steel by nitrogen fixation with titanium microalloying
		Reducing the crack sensitivity of Nb containing low alloy steel slabs is a necessary condition of the advanced process of hot delivery and hot charging of steel slabs with lower fuel consumption and emission reduction. The grain size number and precipitate characteristics of Nb bearing low alloy steel slab with different titanium content were comparative studied by ultra-high temperature confocal laser scanning microscope (HT-CLSM) and transmission electron microscope (TEM),in order to reveal the mechanism of reducing the crack sensitivity of Nb containing low alloy steel by nitrogen fixation with titanium alloying. Thermodynamic calculations and TEM results of precipitates in Nb containing low alloy steel slabs show that increasing the titanium content (from 0.010% to 0.023%) enhances the precipitation temperature of titanium nitride particles (more than 1 400 ℃), which reduces the grain size of the steel by about 44% (from grade 4 to grade 6.5) by pinning the austenite grain boundaries, resulting in a significant reduction in the crack susceptibility of the high-temperature cast billets. The preferential precipitation titanium nitride particles can fixing nitrogen element to reduce the precipitation temperature of niobium-carbon nitride and aluminum nitride, and act as a heterogeneous nucleation core of nitride precipitates of niobium and aluminum to inhibit their precipitation at the grain boundary,which reduces the risk of grain boundary embrittlement of the Nb bearing low alloy steel. Modulation of nitride precipitate behavior by nitrogen fixation with titanium microalloying and grain refinement of the Nb bearing low alloy steel effectively reduced the width and depth of the third embrittlement temperature groove and increased the high temperature tensile strength by 21.3%-27.5% of niobium-containing steels, resulting in reduction of the incidence of subcutaneous cracking in cast billets by more than 80%. Controlling the titanium content in the range of 0.015% to 0.020% niobium-containing low-alloy steels can effectively avoid grain-boundary chain precipitation of precipitates leading to rolling cracks of hot charged cast billets.
		2022 Vol. 57 (8): 94-102 [Abstract] ( 170 ) [HTML 1KB] [PDF 6545KB] ( 317 )

	103	ZHOU Hai-chen, LIU Guo-liang, LI Hai-bo, DENG Xiao-xuan, JI Chen-xi, LUO Yan-zhao
		Online prediction method of slag entrainment in mold based on numerical simulation
		When the mold flux is entrained in the molten steel, it is easy to be captured by the growing solidified shell. Finally, the surface defects caused by the mold slag entrainment will be formed on the cold rolling sheet,which seriously deteriorate the quality of steel products. The phenomenon of slag entrainment in the mold is effected by the molten steel composition,temperature,flow pattern,and argon flow rate. The velocity of molten steel at the top surface of mold is an important parameter that reflects whether slag entrainment occurs at the steel-slag interface. However,the maximum velocity of molten steel at the top surface under different casting speeds, argon flow rates,and submergence depths of SEN cannot be predicted online in the actual casting process. An online prediction method of slag entrainment in the mold based on the numerical simulation of multiphase flow in the slab continuous casting mold was proposed. First,a 3D mathematical model of the multiphase flow was built and the behavior of molten steel flow with different casting speeds,argon flow rates, and submergence depths of SEN was simulated. Then,the calculated maximum velocity of molten steel at the top surface was fitted and the prediction equation of the maximum velocity under the fixed mold section was obtained. Finally,the accuracy of the method was verified by nail board measurements in a steel plant. The results shown that the speed of molten steel on the top surface had a trend of increasing first and then decreasing along the mold width and had a maximum value at the 1/4 mold width under different casting parameters. The speed had a larger value near the narrow face and the SEN under the smaller and larger casting speed,respectively. It had a larger value near the SEN and the narrow face under the smaller and larger argon flow rate,respectively. With the increasing of submergence depth of SEN,the speed varied small near the SEN and the narrow face. Based on the fitted equation of the molten steel velocity,the online prediction of slag entrainment in the mold was realized through comparing the maximum speed of the molten steel with the critical speed of slag entrainment at the steel-slag interface.
		2022 Vol. 57 (8): 103-110 [Abstract] ( 169 ) [HTML 1KB] [PDF 4588KB] ( 507 )

	111	WANG Hong-tao, HAN Yi-hua, CAO Li-jun, ZHU Li-guang
		Optimization of electroslag remelting slag system of H13 hot work die steel
		Die steel is the most important part of mold, its variety, specifications and quality play a decisive role in the performance, service life and manufacturing cycle of the mold. Due to the strict quality requirements of die steel, higher requirements are put forward on the production technology and preparation process of die steel. The steel ingot smelted by the electroslag remelting (ESR) process has the advantages of high uniformity, high cleanliness and low segregation, gradually become one of the main technical means for smelting high-quality die steel. During electroslag remelting, the slag system plays a key role in melting electrodes, molten steel refining, solidification and crystallization, etc, it is the basis of smelting stability, therefore, selecting appropriate slag composition and performance is the key to the electroslag remelting process. This research combined the characteristics of 4Cr5MoSiV1 hot work die steel, take the current five H13 hot work die steel ESR slag systems of a steel factory as the research object, through the physical and chemical performance analysis and microstructure research of the slag systems, the direction of slag system optimization was put forward, then defined the slag systems suitable for ESR remelting H13 hot work die steel. The results shows that the melting point, viscosity, density, optical alkalinity, electrical conductivity and other physical and chemical properties of L4 slag system is better. The average coordination number of Al in the slag is the largest while it is 2.39. Moreover, the proportion of Al with three coordination and four coordination is relatively high, and the network structure is more complicated. Complex structural units Q³ and Q⁴ have the most content, and they have a network structure with high polymerization degree. Al—O bond length is short and Si—O, Si—F bonds with shorter bond lengths, electroslag remelting process is the most stable, using this slag system can effectively improve the structure and performance, surface quality of H13 steel, and reduce power consumption. The research results provide theoretical guidance for the industrial production of H13 hot work die steel electroslag remelting in a steel factory.
		2022 Vol. 57 (8): 111-122 [Abstract] ( 145 ) [HTML 1KB] [PDF 5124KB] ( 414 )

Metal Forming

	123	ZHANG Jian-lei, CHEN Wei, LU Jia-dong, YUE Chong-xiang
		Design and application of work roll profile on UCM-mill
		When UCM mill uses conventional chamfering work roll to produce silicon steel,the strip steel has the problem of edge tension and belt breaking,which affects the production efficiency. To solve this problem,the roll profile EDC anti breaking belt is designed independently. It reduces the change rate of edge chamfer through reverse arc design and homogenizes the strip steel edge stress. It can improve the production stability on the premise of ensuring that the mill edge drop control level is not reduced. The EDC roll profile curve is symmetrically distributed on both sides,including the middle flat roll zone,anti break belt control zone and deviation control zone. Because UCM mill does not have the function of work roll shifting,this paper divides multiple width sections according to the distribution law of product width. It designs multiple sets of roll profiles to adapt to the rolling of different width sections. The three-dimensional elastic-plastic finite element model of strip rolling is established by numerical simulation technology,and the strip edge stress and edge drop control effect of EDC roll profile and conventional chamfering work roll are compared. The simulation data show that strip edge stress of EDC work roll profile is reduced. Under the same roll bending force,the improvement effect of EDC roll profile on edge drop is more obvious. Under the condition of zero bending force,the edge drop of conventional chamfering work roll is 15 μm. The edge drop of EDC roll profile is 8 μm. The effect of edge drop control is better than conventional chamfering work roll. The roll profile parameters are written into Python software to realize the efficient and automatic solution of curve parameters. It can adjust the roll profile parameters according to the on-site roll use and product edge drop requirements,and has a certain flexibility. The EDC roll profile curve is applied to the commissioning of a 1 420 UCM coupled mill. The on-site shape is normal and the production is stable. The proportion of width thickness difference ≤7 μm is increased from 32% to 56%,with an increase of 75%. The effect is significantly improved. The belt breaking rate of the mill is controlled from 0.1% to less than 0.02%.
		2022 Vol. 57 (8): 123-131 [Abstract] ( 120 ) [HTML 1KB] [PDF 3209KB] ( 434 )

Materials

	132	CAO Guang-ming, SHAN Wen-chao, LIU Xiao-jiang, WANG Chen-yang
		High temperature oxidation behavior of Fe-2.2%Si steel in different atmosphere
		In order to explore the compound effect and mechanism of Si elements and heating process parameters(atmosphere,temperature and time) on the formation of oxide scale on the surface of Fe-2.2%Si steel,the high temperature oxidation behavior of Fe-2.2%Si steel under the condition of dry air and water vapor was studied by thermogravimetric analyzer(TGA). The oxidation rate constant and oxidation activation energy were calculated by using the oxidation weight gain data obtained from the experiment. The kinetic model of oxidation was established. In addition,the growth mechanism and nodulation mechanism of oxide scale in two kinds of atmosphere were clarified. The experimental results show that the oxidation weight gain curves obtained under different oxidation atmospheres are in accordance with the parabola law. When there is water vapor in the oxidation atmosphere,the oxidation rate of the experimental steel increases and the oxidation activation energy decreases,which leads to the increase of oxidation weight of the experimental steel. Under two kinds of oxidation atmosphere,the oxide scale of the experimental steel is composed of oxide scale and the Si-rich layer at the interface between the oxide scale and the matrix,but the Si-rich layer of the experimental steel obtained under water vapor is loose and porous,and there are a large number of voids and microcracks in the oxide scale. The oxidation mechanism is mainly due to the growth stress during the growth of oxide scale and the existence of water vapor,which leads to the outward diffusion of H₂,resulting in a large number of holes and cracks in the oxide scale, which provides a channel for the diffusion of oxidation medium and is beneficial to the diffusion of gas phase materials. and then promote the oxidation behavior of the experimental steel. In addition,the Si-rich layer formed at the interface between the oxide scale and the matrix consumes the Si elements in the matrix,resulting in a poor Si zone on the surface of the matrix,and the oxidation medium can contact the matrix directly through the holes and cracks in the oxide scale,so that the oxidation rate of the matrix in this area increases rapidly,the thickness of the oxide scale increases rapidly,and the nodulation shape is gradually formed.
		2022 Vol. 57 (8): 132-142 [Abstract] ( 301 ) [HTML 1KB] [PDF 6335KB] ( 382 )

	143	ZHANG Ying-bo, ZOU De-ning, LI Yu-nong, WANG Yong, XU Ran, WANG Fan
		Effects of Si on ductile-to-brittle transition behavior of a ferritic heat-resistant stainless steel
		The 18Cr-Al-Si ferritic heat-resistant stainless steel has excellent thermal conductivity and good high-temperature resistance for gas corrosion, and compounded addition with Al and Si elements to ensure its excellent resistance to high-temperature oxidation. This steel is a new type of material used for key structural connectors of supercritical and ultra critical power station boilers. In the past, the traditional water-jet forming method was mainly used for the processing of the connector material, but the production efficiency was low and the cost was high. When the room temperature stamping forming method is adopted, because the ferritic heat-resistant stainless steel plate is brittle, it is easy to generate cracks in the center of the thickness of the steel plate. When using warm stamping processing (ie processing in the toughness temperature range), the problem of cracking in the center of the steel plate can be avoided. In order to improve the production efficiency of the connecting parts, it is necessary to optimize and determine the technological parameters of the warm processing of the steel. The effect of ductile-brittle transition behavior of silicon content(mass fraction is 0%-0.9%)18Cr-Al-Si steel was studied by means of a series of Charpy impact test methods and by means of scanning electron microscope (SEM), transmission electron microscope(TEM) and energy dispersive spectrometer(EDS).The results show that with the increase of silicon content,the impact absorption energy at each test temperature gradually decreases,the ductile-brittle transition temperature(DBTT)increases, the proportion of cleavage plane area in the micro fracture gradually increases,and the dimple area gradually decreases.The silicon element has a great influence on the microstructure and precipitates of the annealed 18Cr-Al-Si steel. With the increase of silicon, the ferrite grain size in the steel gradually increases, and the M₂₃C₆ carbide gradually changes from small-sized strips or blocks. become long or large. The larger ferrite grain size and the precipitation of elongated or massive M₂₃C₆ carbides are the main factors that deteriorate the impact toughness of the steel.
		2022 Vol. 57 (8): 143-151 [Abstract] ( 128 ) [HTML 1KB] [PDF 6865KB] ( 300 )

	152	BAO Shuang, YANG Geng-wei, XU Yao-wen, HAN Ru-yang, ZHU Xiao-xiang, ZHAO Gang
		Austenite grain growth behavior of medium manganese martensitic NM500 steel
		Medium manganese martensitic wear-resistant steel is a new type of wear-resistant steel with low cost and high performance. It is of great significance for controlling the microstructure and properties of steel to reveal the growth behavior of austenite grains in the steel and to establish an accurate prediction model. The austenite grain growth behavior of medium manganese martensitic NM500 steel under different heating temperatures and holding times was systematically investigated by means of Gleeble-3500 thermal simulation testing machine,metallographic microscope and transmission electron microscope. The effect of second phase on the austenite grain growth behavior was also explored. The results showed that the effect of heating temperature on the austenite grain growth behavior in the experimental steel was significantly greater than that of the holding time,and the austenite grain growth behavior in the experimental steel could be divided into two regions due to the precipitation behavior of V(C,N) particles in the matrix. When the heating temperature was below 950 ℃,there were a large number of undissolved nanoscale spherical and short rod-like V(C,N) particles which can effectively pin the austenite grain boundaries in the experimental steel,and the austenite grains grew slowly. However,when the heating temperature was higher than or equal to 950 ℃,the V(C,N) particles in the experimental steel were dissolved and coarsened in large quantities. For example,when the heating temperature was 950 ℃ and the holding time was 60 min,the volume percent of V(C,N) particles in the experimental steel was only 0.041%,and the average particle size increased to 45.78 nm. Its pinning effect on the austenite grains was significantly reduced,and with the increase of heating temperature,the atomic diffusion speed was accelerated,resulting in the rapid growth of austenite. Moreover,based on the Beck model,the isothermal austenite grain growth kinetic model of the experimental steel was established,and the apparent activation energies of austenite grain growth in the experimental steel at lower and higher temperature regions were calculated to be 66.561 kg/mol and 170.416 kJ/mol,respectively. The calculated values of austenite grains were in good agreement with the measured results.
		2022 Vol. 57 (8): 152-159 [Abstract] ( 174 ) [HTML 1KB] [PDF 4573KB] ( 447 )

	160	GAO Xin-qiang, PENG Wei, FAN Zeng-wei, BAI Jia-xin, WEI Xi-cheng, DONG Han
		Effect of purity on recrystallization texture and grain Schmid factor of pure iron
		In order to study the effect of purity on recrystallization texture and Schmid factor of pure iron,the recrystallization texture and Schmid factor of 2N,3N,4N pure iron were studied by annealing recrystallization and EBSD with commercial 2N8 and 3N5 pure iron and 4N3 kg high purity iron prepared in laboratory. The results show that the grain structure of 2N8,3N5 and 4N3 pure iron is equiaxed ferrite with low residual stress and dislocation density,which was completed recrystallization. Among them,the texture of 2N8 and 3N5 pure iron showed the same dispersive distribution characteristics,while the texture of 4N3 high purity iron was concentrated with less random texture. The ODF figures and distribution density of orientation line further show that 2N8 and 3N5 pure iron have similar α {hkl}〈110〉 and γ {111}〈uvw〉 texture characteristics and variation trend that they both have higher distribution density in the α orientation {111}〈110〉 and the γ orientation line density decreases with the increase of φ₁. However,4N3 high purity iron has 〈113〉\|X and γ texture,and contains {332}〈113〉 texture which is favorable to anisotropy of mechanical properties. In addition,the γ orientation linear density increases with the increase of φ₁ until the orientation density of {111}〈112〉 is higher than that of 2N8 and 3N5 pure iron. The results of grain Schmid factor and its frequency distribution histogram show that low Schmid factor grains are surrounded by high Schmid factor grains in 2N,3N,4N pure iron. In the three slip systems {110}〈111〉,{112}〈111〉 and {123}〈111〉, the average of sum of Schmid factors of grains is 0.467(4N3)>0.461(3N5)>0.459(2N8),showing the trend of increasing with the increase of pure iron purity. According to Schmid′s law,the texture characteristics of 4N3 pure iron are most conducive to its deformation. In conclusion,as the purity of pure iron increases from 2N8 to 4N3,the impurity atoms of sample decrease,which promotes the formation of strong 〈113〉\|X and γ texture characteristics and {332}〈113〉 texture which is beneficial to the anisotropy of mechanical properties of the material of 4N3 high pure iron,and increases the average of sum of Schmid factor of grain.
		2022 Vol. 57 (8): 160-167 [Abstract] ( 203 ) [HTML 1KB] [PDF 5113KB] ( 538 )

Equipment Technology

	168	SUN Wei-hua, JIAO Ji-cheng, LI Shuai-min, CUI Jian, CAO Jin-sheng, WANG Meng
		Research and application of on-line steel mechanical property prediction in a hot strip mill
		The traditional testing method of mechanical properties of steel products in a hot strip mill is an experimental method based on the statistical random sampling theory. The test samples are cut from the tail end of a hot coil and then tested in a laboratory. Test results represent the performance of the whole batch of steel products. Due to the long steel production process and certain fluctuations in the control parameters of the production process, the traditional mechanical property testing method cannot reflect the mechanical properties of each coil of strip steel, and the representativeness of the tested samples is not sufficient. With the rapid development of industrial Internet, big data and artificial intelligence technologies, especially the development and application of industrial big data-related technologies, new approaches are provided for solving this problem. Taking the realization of on-line steel mechanic properties prediction (On-line MPP)of hot tandem rolling products of Shandong Iron and Steel Group Rizhao Co., Ltd. as the test object, and based on the key control process parameter data of the whole process of the hot rolling products, the neural network, random forest and other algorithms are used to establish carbon structural and low-alloy high-strength construction steel mechanical properties prediction model, built a mechanical properties prediction system for hot-rolled products based on industrial big data, including data acquisition, data cleaning, model training, result analysis and online application. The on-line MPP has put into application for over two years and it has demonstrated well precision,high stability and reliability. The prediction accuracy of the model is within ±6%, the sample volume reaches more than 90%, and the MAPE (average absolute percentage error) ≤4%, which is lower than the reproducibility detection level., it can replace sampling inspection. As a result, shorten product inspection cycle, the mechanical properties of the product can be grasped after rolling. The system has become an important part in the production and operation process.
		2022 Vol. 57 (8): 168-176 [Abstract] ( 179 ) [HTML 1KB] [PDF 4608KB] ( 403 )

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