钢铁钒钛

Study of electronic structures and optical properties of N-doped anatase TiO₂

Yin Xianglu, Teng Aijun, Zeng Zehua, Zhang Dongbin, Dai Yu, Wu Wei

2022, 43(2): 1-6. doi: 10.7513/j.issn.1004-7638.2022.02.001

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Abstract:
By substituting N atoms for Ti or O atoms at different positions, three doped structures at different positions are constructed, i.e., O-Ti-N, Ti-O-N and N-Ti-N. Based on density functional theory and first-principles calculations, the effects of three kinds of nitrogen doping on the crystal structure, energy band structure, density of states and optical properties of TiO₂ were studied. The research results show that all three doped structures can be stably existed in TiO₂. The doping of nitrogen atoms significantly reduces the band gap of TiO₂. Due to the hybridization between N 2p and O 2p, impurity levels are formed in the forbidden band region, which reduces the energy required to excite the electron to conduction band. In the Ti-O-N structure, the absorption spectrum shows obvious red shift, which proves that this structure is more conducive to improving the photocatalytic activity of TiO₂ in the visible light range.

Research progress in preparation of titanium dioxide catalyst carrier for denitrification

Li Huaquan, Qiu Guibao, Lv Xuewei

2022, 43(2): 7-14, 20. doi: 10.7513/j.issn.1004-7638.2022.02.002

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Abstract:
Titanium dioxide (TiO₂) has been widely used in SCR flue gas denitrification catalyst industry because of its excellent performance, and has become a hotspot of application research at home and abroad in recent years. We herein reviewed the technology research situation of titanium dioxide as denitrification carrier prepared by using liquid phase and solid phase methods, as well as the research situation of titanium dioxide loaded active component of denitration catalyst. The related principles, characteristics, advantages and disadvantages, and research progress of these preparation methods are compared and analyzed, and the application prospect of the denitration catalyst carrier titanium dioxide is presented. The deficiency and research direction in the industrialization and engineering application with regard to the preparation of denitration catalyst carrier TiO₂ were clarified. It was pointed out that the improvement and promotion of the preparation method relying on sulfuric acid method for the denitration catalyst carrier TiO₂ with large specific surface area, high activity and low cost will still be the research focus and development trend.

Study on the correlation between particle size and blue phase indicators of rutile titanium dioxide

Liu Chan, Lu Ruifang, Sun Qiang, Shi Ruicheng, Wu Jianchun

2022, 43(2): 15-20. doi: 10.7513/j.issn.1004-7638.2022.02.003

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Abstract:
In this paper, different K₂O-P₂O₅-ZnO salt treatment formulas were used to treat meta-titanic acid, and eligible rutile titanium dioxide was obtained after calcination. SCX value as the blue phase indicators, Z-Ave value as the ZS90 mean particle size and SEM mean particle size were detected. The linear correlation among them was analyzed by means of linear fitting and regression. The results show that as the correlation indicators, the Pearson correlation coefficients of Z-Ave value and SCX value, SEM mean particle size and SCX value are respectively −0.957 and −0.935. There is a negative linear correlation between the two particle size indicators and SCX value. The R-Sq value of the linear regression equation between SCX value and Z-Ave is 91.6%, while this value between SCX value and SEM mean particle size is 87.5%. The linear regression results show that the prediction effectiveness of the SCX value for Z-Ave value is slightly better than that for SEM mean particle size. Manufacturers can put the conventional monitoring index SCX value into the corresponding fitting equation to carry out statistical analysis and tracking of product particle size, and adjust the process technology accordingly.

Titanium flotation dynamics study for a beneficiation plant in Panxi

Tan Shiguo, Fan Xuesai, Jiang Rendong, Luo Rongfei

2022, 43(2): 21-24. doi: 10.7513/j.issn.1004-7638.2022.02.004

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Abstract:
The paper studies the dynamics characteristics of flotation cells for a beneficiation plant in Panxi. Based on the method of collecting air via draining water, the air flowrate is 0.16~0.51 m³/(m²·min) for rougher and scavenger. The air dispersion of direct flow cell is better than that of the pumping cell. During mineralized bubbles transporting from 1 000 mm towards 200 mm distance from the lip, the grade of mineral and bubble loading is almost same. It demonstrates that mineralized bubbles are stable after the mineralized bubbles transporting to 1 000 mm and minerals are difficult to detach from the bubbles. The solid concentration exists layering in flotation cell. Deeper than 1 500 mm from the lip, the solid concentration remains similar. With the distance decreasing, the solid concentration decreases sharply.

Research progress on V₂O₅ extraction from vanadium-bearing shale

Kang Xuanxiong, Ye Guohua, Zhu Siqin, Liang Xueyin

2022, 43(2): 25-34. doi: 10.7513/j.issn.1004-7638.2022.02.005

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Abstract:
The main links of vanadium extraction from vanadium-bearing shale were introduced, including pre-enrichment, roasting, leaching, etc. The advantages and disadvantages of each step were analyzed and discussed. Pre-enrichment of vanadium-bearing shale can improve the grade of vanadium in the raw ore, reduce ore processing capacity, and increase the effective utilization of vanadium-bearing shale resources, but requires high ore properties. Roasting can effectively destroy the crystal structure of vanadium-bearing shale and promote the conversion of vanadium from low valence to high valence. Nevertheless, there are some problems such as low efficiency, high energy consumption and potential pollution. The direct acid leaching process can effectively extract vanadium in the form of adsorption from vanadium-containing shale, but the applicability to vanadium-bearing shale with isomorphism in the mica crystal lattice is poor. Recently new occurring leaching technologies, such as ultrasonic leaching, microwave leaching, microbial leaching, etc., can strengthen the destruction of the crystal structure of vanadium-bearing minerals. However, these processes have not been well used in industry at present due to limited development level of technology and equipment.

Study on viscosity characteristics of molten vanadium slag during iron-extracting reduction process

Wang Ning, Chen Min, Zhang Lingxi

2022, 43(2): 35-40. doi: 10.7513/j.issn.1004-7638.2022.02.006

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Abstract:
In this paper, the viscosity variation of the vanadium slag system in the iron-extracting reduction process from molten vanadium slag in cutting waste was studied, and the effect mechanism of structural units in the melt on macro-viscosity was revealed from the perspective of microstructure by studying the melt structure of vanadium slag system. Results showed that the content of FeO in the slag decreased, and the content of SiO₂ increased during the reduction reaction. Meanwhile, the free oxygen ions in the slag decreased, and the chain and ring silicate structure could not be destroyed, further causing the decrease of simple silicate structural units such as Q⁰ and Q¹, and the increase of complex silicate structural units such as Q² and Q³. Finally, the melt polymerization degree increased, and the slag viscosity increased gradually.

Anisotropy of tensile and low cycle fatigue properties of commercial pure titanium TA2

Liang Yuanchang, Chang Le, Zhou Changyu

2022, 43(2): 41-47. doi: 10.7513/j.issn.1004-7638.2022.02.007

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Abstract:
To systematically study the anisotropy of tensile and low cycle fatigue properties of commercial pure titanium, tensile and low cycle fatigue tests at room temperature were carried out along the rolling direction (RD), 30° to RD (RD-30°), 60° to RD (RD-60°) and transverse direction (TD). With the increase of sample angle, the yield strength and yield ratio increase, and the plasticity of the material decreases. The Hollomon model and Johnson-Cook model were used to predict the true stress-strain curve of commercial pure titanium, and it was found that the Hollomon model has higher prediction accuracy. Low cycle fatigue test results find that all samples show cyclic softening feature. The cyclic stress amplitude increases with the increase of sample angle, and the total strain energy density increases, resulting in a decreasing trend of fatigue life. The low cycle fatigue life of specimens with different orientations satisfies Manson- Coffin empirical relation.

Molten salt assisted preparation of TiB₂ powder from Ti-Si-Fe and B

Cheng Dengfeng, Zhang Jinhua, Wang Jingran, Ke Changming

2022, 43(2): 48-55. doi: 10.7513/j.issn.1004-7638.2022.02.008

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Abstract:
TiB₂ powders were synthesized in NaCl-KCl molten salt by amorphous boron and Ti-Si-Fe alloy extracted from high titanium blast furnace slag. The effects of reaction temperature, holding time, molten salt amount and mole ratio of B to Ti on the reaction process were investigated. The results show that increasing the reaction temperature or extending the holding time can promote the reaction process. TiB₂ begins to form at 850 ℃ and the reaction completes at 1 100 ℃. Molten salt can facilitate the reaction process. The distribution of elements shows that the particles containing Fe also contain Si, corresponding to the product FeSi₂. Most of the particles contain Si, Ti and B at the same time, indicating that TiB₂ and Si are associated in these particles. A few particles contain only Ti and B, corresponding to TiB₂. There are two kinds of particle morphology of the product. One kind of particle presents cracking appearance with cracks or micron holes connected to the interior, which contains TiB₂, Si or FeSi₂. The other particle is composed of flake TiB₂. The reaction mechanism of Ti-Si-Fe alloy with B in molten salt is described below. First of all, titanium reacts with B to form TiB₂ , then Si and FeSi₂ are released. Most TiB₂ nucleate and grow with Si and FeSi₂ as the skeleton which maintain the original morphology of Ti-Si-Fe particles. A small amount of TiB₂ nucleate and grow in molten salt to form flake TiB₂ aggregates. The sequence of reaction between alloy phase and B is Ti₅Si₃, TiSi, TiFeSi₂ and TiSi₂.

Preparation of graphene/TiO₂ composites and study on degradation of methyl blue

Gao Wei, Wang Jun, Li Yufeng, Tang Weiwei, Zhang Zhe

2022, 43(2): 56-61. doi: 10.7513/j.issn.1004-7638.2022.02.009

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Abstract:
Photocatalytic degradation has become the fastest developing method in the field of wastewater treatment. GN/TiO₂ composites were prepared by sol-gel method in order to improve the photocatalytic performance of TiO₂ and the degradation effect of the composites on methyl blue was studied. The microstructure of the sample was characterized by XRD and SEM. The effects of calcination temperature, calcination time and the content of graphene on the photocatalytic performance of GN/TiO₂ composites were investigated. The experimental results show that TiO₂ is spherical with a size of 70～200 nm and distributing on the lamellar and edge of the graphene. When kept at 500 ℃ for 20 min and the concentration of graphene is 5%, the material has the best photocatalytic performance on the degradation rate of methyl blue with the value of 87.21%. Moreover, the reutilization rate and the mechanism of photocatalytic degradation of methyl blue by GN/TiO₂ composites were studied, and the results show that the degradation rate of methyl blue is reduced by 17.64% after 5 times repeated.

A study on fatigue damage behavior of single-wire MIG welding joint for TC4 titanium alloy

Zhang Long, Li Qingbo, Dai Yu, Chen Donggao, He Yifan

2022, 43(2): 62-67. doi: 10.7513/j.issn.1004-7638.2022.02.010

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Abstract:
A single-wire MIG welding process was carried out to weld TC4 titanium alloy with a thickness of 15 mm. The base metal and welded joint microstructure, tensile, and fatigue properties were analyzed and tested. The results showed that the welded joints were divided into the base metal, heat-affected zone, and weld zone. The base metal had an α+β equiaxed structure, and the heat-affected zone was a mixture of α+β and α′-martensite. The grains in the weld zone presented a coarse state under the intense thermal shock; meanwhile, the α′-martensite structure formed the interior of the grain. The tensile specimen fractured at the base metal, and the elongation after fracture was 10.5%. The fatigue life of base metal and welded joints decreased with increased stress levels. The fatigue life of base metal was higher than that of base metal at high-stress levels but opposite at low-stress levels. The fatigue source of the base metal was located at the surface scratches of the sample, and the joint fatigue originated from the internal pores. Many secondary cracks formed in the fatigue propagation zone of the joint, the spacing of the fatigue bands in the fatigue propagation zone was more minor than that of the base metal, and there were many dimples in the transient fracture zone of the joint and the base metal.

Study on the optimized preparation of high-purity V₂O₅ nanowire nonwoven

Ni Wei, Peng Bijun

2022, 43(2): 68-72. doi: 10.7513/j.issn.1004-7638.2022.02.011

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Abstract:
Aiming to solve the preparation problems of complex, high cost and low efficiency of the existing vanadium pentoxide (V₂O₅) nanomaterials, especially their nanowire nonwovens, herein a one-step hydrothermal method for efficient preparation of V₂O₅ nanowire nonwoven was provided and the relevant mechanism was preliminarily studied afterwards. In comprehensive consideration of product quality and economy, the optimized hydrothermal reaction conditions are 180～200 ℃, 18～24 h, the concentration of hydrochloric acid in the system is 1%～3%, and the concentration of ammonium metavanadate (AMV) is 1%～3%. The optimized nanowire cloth has a thickness of 0.1～1 mm with inner wire diameter of 50～100 nm. Through the optimization of preparation conditions, the resulting V₂O₅ nanowire nonwoven shows good flexibility, structural uniformity and adjustable wrinkles.

Progress of vanadium-based electrode materials in energy storage

Zhou Hua, Song Yongchang, Liu Jin, Hao Yanwei, Sun Ruimin, Zhou Yongheng, Zhang Yanshu

2022, 43(2): 73-80. doi: 10.7513/j.issn.1004-7638.2022.02.012

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Abstract:
Electrode materials derived from vanadium possessing variable valence states, open structures and high theoretical capacities are considered as low-cost and high-performance energy storage materials with potential application in the fields of sodium-ion batteries, lithium-ions batteries and supercapacitors. The electrode materials such as vanadium oxides, sulfides and vanadates were summarized and have attracted much attention on the design, the modification or composite materials furtherly enhancing the energy density, power density and cycle life, which have greatly promoted the research of vanadium materials for energy storage in theoretical and practical application.

Development and application instances of vacuum stirring evaporation technology of titanium tetrachloride slurry

Xu Weichun, Dai Yingjie, Wei Zhizhong, Wang Lijuan

2022, 43(2): 81-86. doi: 10.7513/j.issn.1004-7638.2022.02.013

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Abstract:
In order to realize the efficient recovery and utilization of titanium tetrachloride and valuable metals in the slurry, a vacuum rotary evaporation experiment and vacuum stirring evaporation system for titanium tetrachloride slurry were designed. This paper, used the waste heat steam to heat the titanium tetrachloride, the screw vacuum pump set provided a higher vacuum degree, and the stirring blade stirred the slurry. The moisture content of the obtained dry titanium tetrachloride powder was less than 1%, and the recovery rate of titanium tetrachloride was 99%, effectively solving the complex treatment problems of titanium tetrachloride slurry and difficult recovery of valuable metals in the slurry. The system was environmentally friendly, with high operation efficiency and automation, and was suitable for large-scale titanium tetrachloride production.

Investigating kinetics in preparation of precipitated silica from iron ore tailings

Zhang Peng, Chen Xingyue, Ren Zhifeng, Li Yihong, Zhao Aichun, He Yibo

2022, 43(2): 87-93. doi: 10.7513/j.issn.1004-7638.2022.02.014

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Abstract:
Iron ore tailings (IOT), which are by-product of the ore-smelting process. It will be an inevitable trend to recycle them as a secondary resource due to the potential value of more than 100 billion yuan. Through the composition analysis of IOT from a steel plant in Hebei Province, the SiO₂ in IOT reaches 68.64%, existing mainly in the form of quartz, albite, talc and other crystals. Therefore, the calcination–acid leaching method was proposed to produce silica. The optimum calcination parameters were determined as follows: calcination temperature = 850 ℃, calcination time = 2 h, Na₂CO₃/SiO₂ = 1:1.5. For the acid leaching process, the pH value of the solution is 7 and the stirring temperature is 60 ℃. The results show that the extraction rate of Si from IOT reached 86.43 %, and the content of SiO₂ was 92.26%. In addition, the kinetics of the calcination process was studied, and the activation reaction mechanism and kinetic parameters of IOT were deduced, which provided a theoretical basis for the activation calcination process of IOT.

Study on preparation of aerated concrete block from vanadium-titanium magnetite tailing

Ding Chunjiang, Zhang Kaifeng

2022, 43(2): 94-100. doi: 10.7513/j.issn.1004-7638.2022.02.015

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Abstract:
The aerated concrete block was prepared with the tailings as the main raw material by autoclave-free method. The influence of formula composition on dry density and compressive strength was studied. The results showed that the compressive strength increased first and then decreased, while the dry density had the opposite trend with the addition of cement and lime. The slag improved the compressive strength and dry density, which was lowered by the introduction of Al powder. Aerated concrete blocks with compressive strength of 4.41 MPa and dry density of 695 kg/m³ could be achieved, when the optimum formula (vanadium titanomagnetite tailings∶slag∶quicklime∶cement∶gypsum = 6∶6∶4∶3∶1, 0.05% aluminum powder) was adopted. After 28 days of curing, tobermorite and calcium silicate hydrate were produced. A large number of well-crystallized and fibrous tobermorite interweaved with CSH, forming a typical bridging structure. Therefore, the samples were endowed with low thermal conductivity, excellent water resistance, environmental safety, heat and fire resistance. This paper provides reference for efficient utilization of vanadium titanomagnetite tailings in Chengde.

Experimental study on the prediction model of carbonization depth in high Ti-bearing blast furnace slag concrete

Wang Jie, Li Gen, Liang Yuehua, Gan Bin, Zhao Yi

2022, 43(2): 101-106. doi: 10.7513/j.issn.1004-7638.2022.02.016

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Abstract:
Reinforcement corrosion caused by concrete carbonation is the main reason of durability failure of concrete structures. In order to study the carbonation resistance of Panzhihua high-titanium blast furnace slag concrete, we herein carried out the indoor accelerated carbonation test of high-titanium blast furnace slag concrete with different strength at different carbonation time. The results show that the lower the strength of high-titanium blast furnace slag concrete, the easier it is to be corroded by carbon dioxide. The longer the carbonation time, the more obvious the carbonation phenomenon. Based on Fick’s first law, a model for predicting the carbonation depth of high-titanium blast furnace slag concrete is established according to the strength and carbonation time of high-titanium blast furnace slag concrete. By comparing with the experimental results, the accuracy of the prediction model is verified.

Study on phase and chemical composition of V-Ti sinter during softening, melting and dripping process

Xie Hong’en, Hu Peng, Zheng Kui, Zhu Fengxiang

2022, 43(2): 107-117. doi: 10.7513/j.issn.1004-7638.2022.02.017

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Abstract:
The charging mode of vanadium-bearing titanomagnetite concentrate is an important matter for optimizing the burden structure of blast furnace in Pangang, which also has an important influence on the migration of V and Ti in the process of softening and melting process and the formation of Ti(C,N). At present, vanadium-titanium sinter is the main burden of blast furnace in Pangang, and about half of vanadium-bearing titanomagnetite concentrate enters the blast furnace through sinter. Therefore, the change of phase and chemical composition of vanadium-titanium sinter in the process of softening and melting process was studied. In the softening and dripping process of sinter, Ti, V, Si, Mg, and Al gradually migrate from the phases of titanohematite, titanomagnetite, calcium ferrite to the slag phase, and the slag absorbs the sulfur and ash of coke. The mass fraction of Ti, Si, S and C in hot metal has reached or even exceeded that of normal production. Although the mass fraction of V is much lower than that in normal production, the yield in metallic iron is much higher than that of Ti, Si and S. The main phase of slag after cooling is melilite, followed by perovskite and pyroxene. Ti and V mainly exist in perovskite, followed by melilite and pyroxene. In the process of softening, little titanium carbonitride is produced. However, in the process of melting, the content of titanium carbonitride in slag increases significantly.

Effect of TiO₂ on physicochemical properties and structure of high-alumina blast furnace slag

Yan Hua, Liu Huajun, Chen Buxin, Hu Meilong

2022, 43(2): 118-124. doi: 10.7513/j.issn.1004-7638.2022.02.018

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Abstract:
With the increase of the high-alumina raw materials with high economy in blast furnace (BF) of domestic iron and steel enterprises, the content of Al₂O₃ in slag increases and the fluidity of the slag iron becomes worse, which brings a series of problems to BF smelting. Taking five-component CaO-SiO₂-Al₂O₃-MgO-TiO₂ slag system as the research object, through phase diagram theoretical calculation, experimental research and slag structure analysis, the effects of different TiO₂ content (low titanium 5%, medium titanium 15%, and high titanium 25%) in high-alumina slag on the viscosity and melting temperature of high-alumina BF slag were studied, The reasons affecting the physicochemical properties of slag are analyzed by slag structure. The results show that the fixed alkalinity R₂ is 1.25, the mass fraction of TiO₂ increases from 1% to 25% and the melting temperature of slag in the phase diagram first decreases and then increases. When the mass fraction of TiO₂ is 7%, the liquid phase of slag first precipitates from plagioclase calcium aluminosilicate (Ca₂Al₂SiO₇) to calcium titanate (CaTiO₃) with melting point of 1975 ℃, and the melting temperature of slag increases. When the TiO₂ content increases from 5% (low titanium) to 25% (high titanium) the slag viscosity and melting temperature decrease. The higher the temperature, the better the fluidity of slag, that is, TiO₂ in slag exists in [TiO₆]8- octahedron structure, which can disintegrate the complex silica network structure in slag. When the content of TiO₂ increases from 5% to 25%, the content of complex structural unit Si(Q²+Q³) in the slag decreases, the content of simple structural unit Si(Q⁰+Q¹) increases, Si(Q²+Q³)/Si(Q⁰+Q¹) decreases, and the slag structure is simplified, that is, TiO₂ acts as a slag modifier in the slag whether in low, medium or high titanium content, which is helpful to reduce the viscosity and it plays a positive role in improving slag fluidity.

Effect of vanadium content on microstructure and precipitation of rare earth treated X80 linepipe steels

Wang Shudan, Song Bo, Mao Jinghong

2022, 43(2): 125-132, 177. doi: 10.7513/j.issn.1004-7638.2022.02.019

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Abstract:
In order to improve the corrosion resistance of X80 linepipe steel, different vanadium content (0.05%, 0.10% and 0.15%) was added into a rare earth (0.02%) treated X80 linepipe steel. Optical microscope (OM), cold field emission scanning electron microscope, thermodynamic software Thermo-CalC, transmission electron microscopy and energy dispersive spectrometer (TEM-EDS) had been used to investigate the structure and inclusions in steel to reveal formation mechanism of acicular ferrite in rare earth treated steel. Besides, the effects of different vanadium content gradients on the microstructure and precipitation of the experimental steels had been studied by thermodynamic calculations. Moreover, the corrosion resistance of experimental steels with different vanadium content in NaCl (3.5%) solution was tested by electrochemical technology. The results indicate that rare earth can bring inclusion modification and facilitate the formation of acicular ferrite. Vanadium can achieve grain refinement. The transmission electron microscope shows a positive correlation between the number and average size of precipitates and vanadium content, which causes a pinning effect and improves the strength of steel. The polarization curve and the AC impedance curve suggest that the corrosion resistance of the experimental steel is initially increased and then decreased with the increase of vanadium content. Vanadium can accelerate the formation of ferrite, which in turn lead to lower corrosion resistance ability due to refine grains.

Effect of bottom blowing argon flow on temperature and solidification of molten metal during casting

Gen Yunfei, Zhong Liangcai, Yang Xiaomeng, Yang Shicun, Zhang Ling, He Longlong

2022, 43(2): 133-139. doi: 10.7513/j.issn.1004-7638.2022.02.020

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Abstract:
The low melting point Pb₁₈Sn₁₂In₂₁Bi₄₉ alloy (mass fraction) in a stainless steel ingot mold during casting with bottom argon blowing was used to investigate the effects of bottom argon blowing on the temperature of the molten alloy and the microstructure of the solidified phase during casting by measuring the temperature at different positions in the mold by thermocouples and observing the microstructure of the solidified phase by scanning electron microscope (SEM). The experimental results showed that the temperature of the central temperature measurement point in the horizontal direction decreased slowly in the casting process without bottom blowing, and the temperature dropped sharply to the isothermal platform temperature after casting. The central point temperature decreased to solidification at a faster drop rate in the casting process with bottom argon blowing. When there was no bottom blowing argon during casting, the liquid alloy was solidified from bottom to top in the vertical direction, while with the bottom argon blowing, the solidification began at all monitoring points almost simultaneously. Under the same cooling conditions, bottom argon blowing noteworthy delayed the solidification start time at the lower part of the model during the casting process. The average diameter of the Sn-rich phase on the detection cross-section was 2.58 μm without bottom argon blowing. In contrast, with bottom argon blowing, the particle size distribution of solidified phase can be effectively improved, the microstructure of as-cast alloy can be refined, and the average diameter of the Sn-rich phase on the cross-section was about 1.89～2.20 μm, which was reduced by 26.7%～14.7% compared with that without bottom blowing.

Effect of Na₂O on the enrichment behavior of phosphorus in the slag system CaO-SiO₂-Fe₂O₃-P₂O₅

He Sai, Liu Yaqin, Lin Lu, Hou Zhongxiao, Huang Fang, Hu Yanbin

2022, 43(2): 140-145. doi: 10.7513/j.issn.1004-7638.2022.02.021

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In this paper, the effects of Na₂O in slag on the existing forms, the law of phase precipitation and the phosphorus enrichment behavior of phosphorus-containing slag are systematically studied by high-temperature experiments in MoSi₂ furnace and analyzed by FactSage, SEM and XRD. The research results show that: for the CaO-SiO₂-Fe₂O₃-P₂O₅ slag system, the addition of Na₂O will replace solid solution calcium of nC₂S-C₃P, forming Na₂Ca₄ (PO₄)₂SiO₄ solid solution. As the content of Na₂O increases to excess, the content of Ca and Si in P-solid solution (Na₂Ca₄(PO₄)₂SiO₄) reduces, and the Na₃PO₄ phase produces the grade of phosphorus in the P-rich phase increases. With the increase of the content of Na₂O in slag, the melting point of the slag decreases significantly, the content of phosphorus in the P-rich phase increases significantly, and the content of P₂O₅ exceeds 30%, which ultimately meets the requirement of phosphorus content in the steel slag phosphate fertilizer. Therefore, adding an appropriate amount of Na₂O (less than 6%) in the steel making process instead of CaF₂ as the fluxing agent can promote the phosphorus enrichment effect in the slag, and the converter slag can be used as a phosphate fertilizer.

Research on IAF nucleation behavior induced by Ce/Ce-Zr inclusion in high strength steel plate for shipbuilding

Meng Xianghai, Wang Wei, Bi Sheng, Li Yungang

2022, 43(2): 146-151. doi: 10.7513/j.issn.1004-7638.2022.02.022

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Abstract:
In this paper, the evolution behavior of ferrite induced by inclusions in FH40 ship plate steel after rare earth alloying was studied. The morphology characteristics of rare earth inclusions formed in steel and the mechanism of IAF formation were observed and analyzed by means of scanning electron microscope (SEM) and energy diffraction spectrum (EDS). The results show that the shape of the rare earth composite inclusions is spheroidized after Ce or Ce-Zr composite treatment, and both inclusions can induce the formation of IAF. Al-Ce-O+MnS inclusions formed by Ce can be explained by Mn-poor zone mechanism and inert substrate mechanism, while Ce-Zr-O+MnS inclusions formed by Ce-Zr combined treatment can only be explained by Mn-poor zone mechanism.

Effect of holding time on solid solution behavior of inhibitors in rare earth oriented silicon steel during reheating

Han Qiang, Yang Lilin, Li Tao, Sun Mingshuang, Fan Jing, Guo Xiaoyu

2022, 43(2): 152-156. doi: 10.7513/j.issn.1004-7638.2022.02.023

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Abstract:
In this paper the solid solution behavior of the inhibitor under various holding time in 0.001 1 % La oriented silicon steel during reheating had been investigated by using OM, LM, methods of electrolytic extraction and mass spectrometer. The results showed that grain size of the test steel increased significantly with the holding time prolonging when the rare earth oriented silicon steel was heated to 1 250 ℃ and held for 10, 20 min and 30 min respectively, and the growth trend slowed down after holding time more than 20 minutes. As inhibitor elements, Mn, Cu and Al were all dissolving back, and holding time greatly influenced dissolution of Mn and Cu. The solid solubility of Mn and Cu increased from 69.8% and 43.7% to 84.2% and 85.2% respectively. Furthermore, with the prolongation of holding time, the insoluble small size inhibitors gradually decreased or even disappeared, and those larger ones gradually changed into small size insoluble substances and gradually dissolved into matrix in RE oriented silicon steel. The quantity decreased and the type of insoluble matter changed from complex to single gradually.

Effect of different amounts of oil on electrochemical corrosion behavior of DC06 automobile steel

Zheng Haoqing, Zheng Zhiwang, Zuo Jun, Su Guanqiao

2022, 43(2): 157-162. doi: 10.7513/j.issn.1004-7638.2022.02.024

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Abstract:
The electrochemical corrosion behavior of DC06 steel plate under different temperatures and oil content was studied by constant temperature and humidity, electrochemical polarization curve and local electrochemical impedance tests. The experimental results showed that the corrosion rate of the DC06 steel plate increased with the increase in temperature under different temperature conditions, and severe pitting corrosion occurred when the temperature was 40 °C. With the increase of oil content to 1500 mg/m², the corrosion rate of steel plate decreased by about 20%, and with the increase in temperature, the corrosion performance improved; DC06 steel plate with a roughness of 1.2 μm can be obtained the optimum corrosion resistance. Moreover, the active dissolution degree of corrosion products of DC06 steel plate increased with the increase in temperature. The corrosion resistance of DC06 steel at high temperature was reduced due to the failure of antirust oil to form a stable protection film at high temperature and the uneven impedance characteristics of the micro area.

Effect of heating rate on austenitization of as-cast 60Si2Mn steel

Wang Ruizhang, Zhou Denghu, Jiang Yan, Yang Kai, Xi Bo, Liao Zhencheng, Huang Zhenyi

2022, 43(2): 163-171. doi: 10.7513/j.issn.1004-7638.2022.02.025

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Abstract:
The linear expansion coefficient of as-cast 60Si2Mn steel at different heating rates (0.2, 1, 3, 10, 50 ℃/s) was recorded using the thermal dilatometer DIL805A. The corresponding thermal expansion curves and volume transformation fraction curves (austenite) were obtained to study the effect of heating rate on austenitization. A high-temperature metallurgical microscope was used to observe and analyze the austenite transformation process of the steel during continuous heating. Studies have shown that the austenite transformation of 60Si2Mn steel during continuous heating can be divided into three stages: the transformation of pearlite to austenite, the dissolution of (Mn,Fe)₃C into austenite and the composition of austenite homogenizing. And as the heating rate increases, the critical temperature of phase transition increases, and the rate of phase transition increases. In addition, high-temperature metallography shows that the A transformation of the as-cast 60Si2Mn steel during the continuous heating process is an alternate nucleation and growth process. This process is discontinuous due to the difference in Si element content.

The effect of annealing process on the microstructures and properties of 2 000 MPa cold-drawn steel wire

Su Hongyan

2022, 43(2): 172-177. doi: 10.7513/j.issn.1004-7638.2022.02.026

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Abstract:
Annealing was used to simulate the galvanizing process of a kind of cold drawn steel wire, and the changes in the structure and properties of the cold drawn steel wire during the galvanizing process were studied utilizing a scanning electron microscope, transmission electron microscope, combined with conventional mechanical testing methods in this paper. The test results showed that the annealing time affected the steel wire′s microstructure and mechanical properties. With the extension of annealing time, the strength of cold drawn steel wire fluctuated first and then decreased significantly subsequently. Meanwhile, the torsional property showed a trend of decreasing first and then rising, and the stage of strength rising was consistent with the stage of significant deterioration of its torsional property. In addition, the surface structure of the steel wire firstly degenerated, the lamellar cementite breaks, forming cementite particles, and the internal dislocation density in the ferrite decreased, while the internal structure of the steel wire could maintain a relatively complete pearlite lamellar structure; after a long time of heat treatment, the surface and internal pearlite lamellar structures all degenerated. The severe deterioration of the torsional properties of cold drawn steel wire in the process of galvanizing was the surface structure inconsistent with the internal structure, and the surface strength was high, causing the deformation was the largest in the torsion process. As a result, stress concentration rapidly deteriorated the torsional performance.

Study on dynamic mechanical properties and constitutive model of 022Cr18Ni14Mo2 stainless steel under impact load

Jia Haishen, Luo Wencui, Zhang Jilin, Yi Xiangbin

2022, 43(2): 178-185. doi: 10.7513/j.issn.1004-7638.2022.02.027

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Abstract:
The quasi-static and dynamic compression tests of 022Cr18Ni14Mo2 stainless steel were performed by using UTM5305 universal testing machine and split Hopkinson compression bar. The strain hardening characteristics and the dependence of flow stress on strain rate were discussed. The quantitative analysis was carried out by taking two parameters of strain hardening index and strain rate sensitivity coefficient into account. Based on the above analysis results, the traditional J-C constitutive model was revised and a new type of constitutive model was constructed. The parameters of the modified constitutive model are identified with the help of experimental data. The predicted values from the model are compared with the experimental values, and the correlation coefficient (R) and average relative error (AARE) of the constitutive model are used to evaluate it. The results show that the sample has obvious strain hardening characteristics and remarkable strain rate sensitivity. The strain hardening index is dominated by strain and strain rate, and the strain rate sensitivity coefficient increases with the increase of strain rate, and the increase amplitude decreases gradually. The correlation coefficient (R) and average relative error (AARE) of the modified constitutive model are 0.9896 and 3.29%, respectively, which can better describe the rheological behavior of specimens at high temperature and high strain rate.

Study on microstructure and properties of high aluminum dual phase steel 980DH with high formability

Zhou Li, Xue Renjie, Cao Xiao’en, Dong Mengyao

2022, 43(2): 186-191. doi: 10.7513/j.issn.1004-7638.2022.02.028

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Abstract:
The influence of static continuous cooling transformation and continuous annealing process on the structure and properties of cold-rolled plates for high aluminum dual phase steel 980DH with high formability were studied by phase transformation quenching dilatometer, continuous annealing simulation tester. The results show that when the cooling rate is between 5 °C/s and 10 °C/s, only bainite transformation occurs. When the cooling rate is greater than 15 °C/s, the proportion of bainite decreases and the fraction of martensite increases as the cooling rate increases. The microstructure of 980DH steel contain mainly ferrite, martensite and retained austenite. Under the processing conditions of soaking temperature at (780～800 ℃)×160 s, slow cooling temperature at 650～700 ℃, cooling rate at 50 ℃/s to 300 ℃ aging treatment for 5 minutes, and then air-cooled to room temperature, CR550/980DH steel plates can achieve excellent performance. It is hoped that this research can be beneficial to the industrial development of high-grade DH steel.

Analysis of Chinese standard GB/T 3620.1—2016: Designation and composition of titanium and titanium alloys

Feng Junning, Xie Chen, Ma Zhongxian, Hu Zhijie, Wei Jiaqi, Feng Yongqi

2022, 43(2): 192-196. doi: 10.7513/j.issn.1004-7638.2022.02.029

Abstract(2523) HTML (366) PDF(221)

Abstract:
This article mainly introduces the historical evolution, the reason, basis, and content of the revision of the new Chinese standard GB/T 3620.1—2016, as well as the relationship between industrial pure titanium designations and material standards. Finally, it expounds the problems that are easy to appear in the transition period and the preventive measures, in order to provide guidance for the reference, production and acceptance of the standard in the follow-up process, deepen the understanding of the new standard, so as to master and apply the new standard in a more comprehensive and systematic way.

2022 Vol. 43, No. 2