钢铁钒钛

Research Progress of Solvent Extraction for Separation of Vanadium and Chromium

Ying Ziwen, Ren Xiulian, Wei Qifeng

2018, 39(4): 1-10,16. doi: 10.7513/j.issn.1004-7638.2018.04.001

Abstract(115) PDF(8)

Abstract:
Vanadium and chromium have the similar chemical properties and naturally coexist at most occasions,so the problem for separation of vanadium and chromium has not been properly solved for a long time.The solvent extraction is currently the most common method for the separation of vanadium and chromium. Traditional extraction systems for vanadium-chromium separation,including neutral complexation extraction system,ion association extraction system,acidic complexation and chelation extraction system,synergistic extraction system,were introduced.Three-liquid phase extraction system was used as an example for introducing a novel extraction system. Furthermore,the advantages and disadvantages of each extraction system were analyzed. Three-liquid phase extraction system is expected to have a broad prospect due to a high separation factor,well physical phenomena,short process flow,simple operation,low cost and flexible ratio of extractant,considering the environment protection and company benefits.

Dynamic and Frontier of Modifications of Li₄Ti₅O₁₂ Anode Material

Li Wang, Liu Jiali, Zhou Lan

2018, 39(4): 11-16. doi: 10.7513/j.issn.1004-7638.2018.04.002

Abstract(164) PDF(5)

Abstract:
As an anode material of lithium ion battery,lithium titanate（Li₄Ti₅O₁₂） has the advantages of stable structure,long life and high safety,and it’s getting more and more attentions in the fields of power and energy storage.However,lithium titanate has a low conductivity and poor electroconductibility prone to causing electrode polarization,which greatly limits its applications in charge-discharge at high current densities.Focusing on the above problems,we summarized the recent research trends on anode material of lithium titanate at home and abroad. It is found that the coated modification,ion doping and composite methods are hot spots for researches on improvement of electrochemical performances of lithium titanate material.At the same time,the shortcomings and defects of carbon anode material were pointed out here,further confirming the superiorities of lithium titanate.Nevertheless,the cost of lithium titanate material is much higher than that of carbon material,which is not conducive to large-scale popularization and promotion.How to reduce the cost of lithium titanate material,improve its specific energy and electrochemical properties,and achieve a widespread application in areas such as large scale energy storage systems,electric vehicles and electric tools is thus the problems that urgently need to be solved in the future.

Vanadium Extraction from Refractory Stone Coal Using a Streamlined Process

YANG Xiao

2018, 39(4): 17-23. doi: 10.7513/j.issn.1004-7638.2018.04.003

Abstract(142) PDF(4)

Abstract:
Based on the properties and petrographic analysis of a refractory stone coal from Hubei province,a novel vanadium extraction process of fluidized roasting-acid leaching with additive-solvent extraction-precipitation was proposed.The effects of roasting temperature,roasting time,dosage of additives,sulfuric acid concentration,liquid to solid ratio,leaching temperature and time on leaching ratio of vanadium were given a special concern.Results show that under the optimum conditions of roasting at 750 ℃ for 20 min,leaching additive dosage of 5%,sulfuric acid concentration of 15%,liquid to solid ratio of 2 ∶ 1 and leaching at 95 ℃ for 6 h,vanadium leaching efficiency can reach 91.32%.Using N235 as extractant,more than 98% of vanadium can be separated and concentrated from the leaching solution by three stages of counter-current extraction and three stages of counter-current stripping. Ammonium metavanadate can be precipitated from the vanadium concentrated solution after impurities removal,and then vanadium pentoxide with purity of 99.75% could be obtained after thermal decomposition of metavanadate. This vanadium extraction process has advantages of short procedure,high efficiency and high purity of product,showing well adaptability to refractory stone coal.

Leaching of Vanadium and Chromium from Vanadium-chromium Residue Intensified with H₂O₂

Peng Hao, Guo Jing, Li Gang, Wang Feng, Wang Lilian, Li Bing, Liu Zuohua, Tao Changyuan

2018, 39(4): 24-29. doi: 10.7513/j.issn.1004-7638.2018.04.004

Abstract(57) PDF(1)

Abstract:
Vanadium and chromium in low valence are difficult to be leached in alkaline medium.For vanadium and chromium leaching,roasting with sodium salts might emit some poisonous gas and large amount of waste water,while roasting with calcium salts will consume much more energy.H₂O₂ as an oxidant was applied to intensify the leaching process of vanadium-chromium residue under alkaline condition.The effect of Na OH dosage,reaction temperature,dosage of H₂O₂,reaction time and stirring rate on the leaching efficiency of vanadium and chromium was investigated.The results indicate that increasing reaction temperature and extending reaction time can improve the leaching efficiency of vanadium and chromium.Vanadium is more easily to be oxidized and leached out in alkaline medium,even with low dosage of oxidant.The leaching ratio of vanadium is up to 94.30% with addition of H₂O₂. The leaching ratio of chromium is proportionally increased with increase of H₂O₂ dosage.Over 90.12% of chromium can be leached out at optimal conditions.H₂O₂ is a clean oxidant,which realizes an efficient and synchronous extraction of vanadium and chromium without bringing other impurities.This method is environmental-friendly with high reaction efficiency,and it could be applied as a new liquid oxidation technology.

Investigation on Separation of Vanadium and Chromium in Alkaline Solution and Preparation of V₂O₅ and Cr₂O₃ Products

Li Ming, Jiang Lin, Wu Zhenxiu

2018, 39(4): 30-35,47. doi: 10.7513/j.issn.1004-7638.2018.004.005

Abstract(125) PDF(3)

Abstract:
This paper focused on vanadium and chromium separation in solution using hydrolysis technology.The factors of p H value,temperature and time for vanadium precipitation have been investigated to study their effect on the precipitation rate of vanadium,and the optimum parameters have been determined as follows: p H of 2,temperature of 90 ℃ and time of 60 min,at which the precipitation ratio of vanadium exceeds 98% with less than 0.3% of chromium residual in the filtration cake after washing.Chromium mainly remains in solution through precipitation,which realizes simple and efficient separation of vanadium and chromium in solution.V₂O₅ products with purity more than 99% can be obtained stepwise via alkali dissolution of the vanadium cake,vanadium precipitation by（NH₄）₂SO₄ and calcination.Using Fe₂（SO₄）₃ to remove vanadium in chromium solution,Na₂SO₃ for reduction and Na OH for precipitation,pigment grade Cr₂O₃ can be acquired by roasting the washed Cr（OH）₃.This work has realized low cost and high efficiency separation of vanadium and chromium in solution as well as preparation of high quality vanadium and chromium products,with 97% and 86.4% of total yield rate for vanadium and chromium,respectively.

Material Proportioning Calculations for Aluminothermic Reduction of Ti-containing Slag

Piao Rongxun, Ma Lan, Yang Shaoli, Yu Junzhi

2018, 39(4): 36-40,69. doi: 10.7513/j.issn.1004-7638.2018.04.006

Abstract(75) PDF(2)

Abstract:
The preparation of Ti-Al based alloy by aluminothermic reduction of Ti-bearing slag is a promising process due to the low cost of raw materials and products.To obtain a good slag-metal separation and required composition of Ti Al alloy,the material proportioning calculations are necessary. In this work,the general equations of material proportioning calculations for aluminothermic reduction of Ti oxides were derived.Using the obtained equations,the material proportioning calculations for aluminothermic reduction of acid-soluble titanium slag were conducted,and the slag composition,alloy composition and distribution of elements between alloy and slag phases were also calculated. The general equations derived in present study can be used in design of aluminothermic reduction process of metallic oxides system.

Carbothermic Reduction Kinetics of Oxidized Panzhihua Ilmenite Concentrate

SONG Bing

2018, 39(4): 41-47. doi: 10.7513/j.issn.1004-7638.2018.04.007

Abstract(66) PDF(6)

Abstract:
The isothermal carbothermal reduction of oxidized ilmenite concentrate/carbon composite pellets was performed with coke as reductant,and the kinetics was analyzed by integration method. The reduction temperature was set at 1 000,1 100,1 200 and 1 300 ℃,respectively.The reduction degree of iron oxides in the oxidized ilmenite concentrate,able to be 91%,increased with increase of the reduction temperature and time.The reduction of oxidized ilmenite concentrate was controlled by interface chemical reaction in early stage of solid state reaction（＜60 min） with activation energy of 51.23 k J/mol at 1 000 ~1 300 ℃,while it was controlled by diffusion in later period（＞ 60 min） with activation energy of 93.53 k J/mol. The main phase transformation during the reduction process can be described as follows: Fe₂TiO₅→ Fe₃Ti₃O₁₀→FeTiO₃.During the phase transformation,the particles’ inner pore and specific surface area were increased,the gas diffusion conditions were improved and the chemical reaction rate in early stage was accelerated.

Effect of Aluminum Purity on Vanadium Loss in Slag and Alloy Composition of Ferrovanadium Smelting Process

Yu Bin, Xiong Kaiwei, Sun Zhaohui, Pan Cheng, Liang Bin

2018, 39(4): 48-51. doi: 10.7513/j.issn.1004-7638.2018.04.008

Abstract(86) PDF(3)

Abstract:
Influence factors of low grade industrial aluminum for ferrovanadium preparation by aluminothermic reduction process were analyzed.Main components of different grades of reducing agent and its effects on vanadium loss and composition of alloy with different grades were investigated. The analysis shows that the reduction of industrial aluminum purity has little effect on the TV content in slag during the preparation of different grades of ferrovanadium.The content range of TV in three stages slag is 0.35% ~0.37%,0.67% ~0.71%,1.15% ~1.20% for FeV50 smelting and 0.20% ~0.25%,0.55% ~0.59%,0.99% ~1.07% for FeV80 smelting,when the purity of reducing agent is 99.8%,99.5% and 99%,respectively.The content of C,Si,P and Mn in alloy increases with decrease of the reducing agent grade.When the purity of industrial aluminum decreases from 99.8% to 99%,A-grade rate of FeV50 and FeV80 alloy decreases from 100% and 95% to 95% and 60%,respectively.

Preparation and Properties of TiO₂ Nanotubes

Xu Ying, Wang Huanhuan, He Shiyu, Cai Yanqing, Wang Bian

2018, 39(4): 52-57. doi: 10.7513/j.issn.1004-7638.2018.04.009

Abstract(225) PDF(9)

Abstract:
In order to make titanium based metals fit for the implant environment of human body and improve the wettability and corrosion resistance,TiO₂ nanotubes were prepared on the surface of titanium by anodic oxidation method at 25 V of DC voltage using NH₄F and ethylene glycol as electrolyte.The effects of anodic oxidation time on morphology,phase compositions,wettability and corrosion resistance of TiO₂ nanotubes were studied.The morphology and phase compositions of TiO₂ nanotubes were characterized by scanning electron microscopy（ SEM） and X-ray diffraction（ XRD）. Distilled water contact angle of the samples was measured by contact angle measuring instrument,and the corrosion resistance of the samples was studied by a potentiodynamic polarization curve method.The results show that when the oxidation time is 2 h,highly ordered TiO₂ nanotubes with pore size range of about 30 ~40 nm and pore wall thickness of about 20 nm can be prepared on the titanium surface. Contact angle between the titanium sheet and distilled water is about 28.8° indicating a better wettability.Furthermore,the self-corrosion voltage of titanium with TiO₂ nanotubes is 0.145 V,about 34% higher than that of pure titanium. The corrosion current is about 0. 468 μA/cm²,and the corrosion resistance Rpis about 1. 023×10⁵Ω/cm² for sample with TiO₂ nanotubes,significantly improving the corrosion resistance.

Preparation and Properties of Mesoporous TiO₂ Photocatalytic Materials

Yang Zaizhi, Fu Xiaoming, Sun Hu

2018, 39(4): 58-62. doi: 10.7513/j.issn.1004-7638.2018.04.010

Abstract(37) PDF(1)

Abstract:
Nano-TiO₂ photocatalyst was prepared by sol-gel method with tetrabutyl titanate as the raw material.The phase composition,microstructure and photocatalytic properties of the obtained nano-TiO₂ samples were characterized by XRD,SEM,UV-Vis,specific surface and aperture analyzer,respectively. The results show that the nano-TiO₂ samples are composed of single anatase phase under low calcination temperatures,having a certain degree of agglomeration with size of about 20 ~60 μm. With increase of the temperature,the size of agglomerations increases.The rutile phase is formed in the samples when the calcination temperature reaches 600 ℃,with size of crystals about 6 ~12 nm which inhibite the grain growth of anatase phase.There is a large number of 4 ~6 nm mesoporous in the sample having a specific surface area of 136.872 m²·g^-1.Degradation rate of methyl orange by the nano-TiO₂ can reach above 92%.

Research on the Properties of Li₄Ti₅O₁₂ Materials by Solid Phase Synthesis

Meng Weiwei, Xu Yongjun, Yan Beilei

2018, 39(4): 63-69. doi: 10.7513/j.issn.1004-7638.2018.04.011

Abstract(323) PDF(7)

Abstract:
Using titanium dioxide as the initial titanium source and lithium carbonate as the initial lithium source,lithium titanate samples were synthesized via solid phase routes with adjusting the ratio of Li/Ti at0.8,0.85,0.9 respectively,based on a deep study of the reaction principles for lithium titanate synthesis.The effects of synthesis conditions on phase structure,apparent morphology and electrochemical properties of the prepared lithium titanate were investigated respectively by TGA-DSC,XRD,SEM,TEM and constant current charge/discharge characterizations.Meanwhile,2016 button batteries were prepared using the lithium titanate samples,and their initial coulombic efficiency was studied.

Effect of Ti Content on Electrochemical Properties of MgNi Hydrogen Storage Alloy

Wang Haihua, Wang Xia

2018, 39(4): 70-73. doi: 10.7513/j.issn.1004-7638.2018.04.012

Abstract(46) PDF(2)

Abstract:
The electrochemical corrosion and electrochemical cycle stability tests of Mg₂Ni-Ti hydrogen storage alloys with different contents of Ti were carried out.The results show that the addition of Ti as alloying element can improve the electrochemical corrosion resistance and electrochemical cycle stability of Mg₂Ni alloy.The content of Ti in the alloy is optimized at 0. 8%. In comparison to those of Mg₂Ni alloy without Ti,the corrosion potential shifts by 87 m V in positive direction and the decay rate of discharge capacity decreases from 86% to 47% when 0.8% of Ti is added for the alloy.

Microstructures and Defect Analysis of TC4 Titanium Alloy Joints by the TIG Welding

LU Xin

2018, 39(4): 74-79,92. doi: 10.7513/j.issn.1004-7638.2018.04.013

Abstract(134) PDF(8)

Abstract:
TIG welding experiments on 20 mm thick TC4 titanium alloy plate were carried out by two varying heat inputs,and the joints were investigated in terms of microstructure,mechanical properties and welding defects.Microstructural observations showed that martensite in welded zone is more dispersed than those in fusion zone and heat affected zone.in Heat affected zone has less quantity and small size of martensite.With the welding heat input increasing,the grain size of the joints grows and martensite becomes larger and more dispersed.High heat input leads to stomata defect and deteriorate the mechanical properties of weld joint seriously.To avoid the defects such as abnormal structures and cracks,the welding heat input should be strictly controlled to prevent the coarse grain in the weld joints.

Research on Fatigue Crack Growth Rate of Electron Beam Welded Joint of TA1 Medium Plate

BAI Wei

2018, 39(4): 80-84. doi: 10.7513/j.issn.1004-7638.2018.04.014

Abstract(48) PDF(4)

Abstract:
Electron beam welding（ EBW） tests have been conducted on TA1 commercially pure titanium medium plates with a thickness of 30 mm.The effect of EBW welding process on microstructures and properties of TA1 material has been investigated by observing the microstructures and conducting Vickers hardness tests on base metal,heat affected zone and weld seam of the welded joints.The effects of microstructure distributional difference on the macroscopic crack growth path and crack propagation rate of welded specimens are discussed by combining the fatigue crack growth characteristics with the microstructures in different parts of the joint.Test results show that compared with the base metal of TA1,the weld seam and heat affected zone（ HAZ） of the welded joint have higher fatigue crack growth resistance,which leads to the deflection of fatigue crack propagation path and the paths extend to base metal finally.Compared with the base metal with equiaxed α phase,the serrated α and α columnar crystals produced by EBW welding have a restrict impact on the fatigue crack growth,which makes the fatigue crack growth rate of the HAZ and weld seam lower than that of the base metal.Under test conditions with stress ratio of 0.1,the fatigue crack growth rate of weld seam is the lowest,the fatigue crack growth rate of HAZ is the second,and the base metal showes the highest fatigue crack growth rate.

Experiment Study on Utilization in Additive of Cement of Panzhihua Ti-bearing Blast Furnace Slag Flotation Tailings

Zheng Yu, Cui Yating, Chen Tao, Wang Weiqing

2018, 39(4): 85-92. doi: 10.7513/j.issn.1004-7638.2018.04.015

Abstract(49) PDF(2)

Abstract:
In order to utilize titanium-bearing blast furnace slag,taking Panzhihua Ti-bearing blast furnace slag as raw material and recovering the titanium component through high temperature modificationflotation separation process.For flotation tailings,the characteristics of the mineral composition,micro-morphology,and specific surface area were analyzed,and tests were performed on cement mixtures under different conditions. The microstructure observation and mechanical properties tests on the cement blocks were then carried out. The experimental results show that the flotation tailings of Panzhihua Ti-bearing blast furnace slag with TiO₂ content of 8. 7% can be used as an additive into inert cement after being ground to d₉₀ of ~20 μm. When the massive weight of slag is 10%,the compressive strength of cement mortar after 28-days hydration is 50.2 MPa,and its activity index is 94.5%.

Experimental Study on Heat Recovery of the Process of Gas Blowing for Blast Furnace Slag

Wang Zibing, Liu Yue, Zhang Yuzhu, Xing Hongwei, Wang Lili, Liu Zhenchao

2018, 39(4): 93-98. doi: 10.7513/j.issn.1004-7638.2018.04.016

Abstract(56) PDF(7)

Abstract:
Blast furnace slag has high level of heat energy,which belongs to high grade waste heat resource,and is of great value for recovery.Taking blast furnace slag as heat source,air as gas quenching medium,air and water as heat exchange medium,rotary slag cooler is applied to carry out high temperature residue heat recovery experiment.The process separates granulation from waste heat recovery,greatly reducing power consumption.The effect of the proportion of texturizer,gas quenching pressure and nozzle structure on the heat recovery efficiency of the system are studied in this paper.The results show that with the increase of the proportion of the texturizer,the thermal efficiency of the system first increases and then decreases,the optimum proportion is 10%.With the increase of gas quenching pressure,the thermal efficiency of the system increases first and then decreases,and the optimum pressure is 0. 3 MPa. With the increase of the Maher number of the nozzle,the thermal efficiency of the system increases gradually,but the number of Maher is over 1.4,the growth rate slows down,and the best Maher number is 1.6.When the three experimental variables are in the best working condition,the thermal efficiency of the system can reach 52.35%.

Experiment Study on Ammonia System Leaching Zinc from Blast Furnace Dust

Huang Ping, Zhang Yuan

2018, 39(4): 99-103. doi: 10.7513/j.issn.1004-7638.2018.04.017

Abstract(42) PDF(2)

Abstract:
For the purpose of effectively leaching zinc from blast furnace dust by means of NH₃-(NH₄)₂SO₄-H₂O ammonia system,the effects of liquid-to-solid ratio,leaching time,leaching temperature,total ammonia concentration and stirring rate on the zinc leaching rate had been experimentally investigated,and the phase of the leaching residue had been determined.Through experimental study the optimized leaching parameters had been obtained as follows: liquid-to-solid ratio of 6 m L/g,leaching time of 60 min,leaching temperature of 20℃,total ammonia concentration of 6.0 mol/L,stirring rate 200 r/min.Under the optimized leaching condition,the leaching rate of zinc is 85.6 %.Phase analysis showed that the main components of leaching residue are SiO₂,Fe₂O₃、Fe₃O₄ and CaO,which indicated highly effective selectivity of zinc from blast furnace dust and effective separation of zinc from iron,silicon and calcium.

Experimental Study on Effect of Electrolytic Temperature on Performance of ZnO/semi Coke Desulfurizer

Dou Guanxiong, Long Yue, Zhang Liangjin, Sang Rongli, Pan Xiangyang

2018, 39(4): 104-108. doi: 10.7513/j.issn.1004-7638.2018.04.018

Abstract(29) PDF(1)

Abstract:
The active semi char loaded with Zinc Oxide was prepared by electrochemical deposition with a semi coke as the carrier,zinc nitrate（Zn（NO₃）₂） and six times methyl four amine（ HMT） as the electrolyte.The samples were characterized by SEM,TEM and FT-IR,and the effects of different electrolysis temperatures on Zn O/char compound desulfurizer were investigated,and the SO₂ adsorption properties of Zn O/char Desulfurizer at different electrolysis temperatures were evaluated.The results show that,under reaction conditions of 60 min electrolytic time,80 ℃ electrolysis temperature,3 V electrolytic voltage,0.001 5 mol/L Zn²⁺ and 0.001 5 mol/L HMT,the prepared catalyst has the 360 min penetration time and 6.1 g sulfur capacity,which can achieve the best load effect and desulfurization effect.

Effect of Al₂O₃ on the Formation Mechanism of Calcium Ferrite

Hu Changqing, Yang Jintao, Zhao Kai, Yan Longge

2018, 39(4): 109-113. doi: 10.7513/j.issn.1004-7638.2018.04.019

Abstract(68) PDF(3)

Abstract:
In the production of fluxed sinter,calcium ferrite as a low melting point compound which appears to be the starting point of liquid phase formation.During the sintering of iron ore the calcium ferrite acts as a reactant to form complex calcium ferrite in sinter,its amount and distribution affect the ore phase structure of sinter.In this paper,the influence of Al₂O₃ on the formation mechanism of calcium ferrite was studied by means of modern analysis and testing techniques,such as XRD and SEM.At temperature of 850 ~900 ℃,Al₂O₃ reacting with dicalcium ferrite（C₂F） forms calcium CA₂ and Calcium ferrite（CF）.When the temperature exceeds the 900 ℃,dicalcium ferrite starts reaction into ferrite calcium. When Al₂O₃ is lower in mixed ore,Al₂O₃ particles react almost completely with C₂F to form CA₂,at the same time some C₂F remained in the ore phase takes part into the reaction and eventually form the complex calcium ferrite.

Analysis of Titanium Distribution Based on the Conditions of Furnace Protection with Titanium Ore

Chang Zhiyu, Jiao Kexin, Ning Xiaojun, Zhang Jianliang, Mo Chaoxing, Chen Rugang

2018, 39(4): 114-121. doi: 10.7513/j.issn.1004-7638.2018.04.020

Abstract(91) PDF(6)

Abstract:
In order to further analyze the influence of composition and temperature of slags and hot metal on the titanium distribution ratio under the conditions of furnace protection with titanium ore,the production data of a blast furnace in China was statistically analyzed. And with the help of thermodynamic software Fact Sage,the calculation model of titanium distribution ratio was established.The results indicate that the distribution ratio of titanium increases with the increase of basicity of slags,and decreases with the TiO₂ content increasing in slags. The distribution ratio of titanium shows a positive correlation with the temperature of hot metal and the content of silicon and titanium,but is negatively correlated with the sulfur content in the hot metal.In order to ensure the effective furnace protection under higher titanium load,the basicity of slags and the content of silicon in hot metal should be appropriately increased while controlling the sulfur content and maintaining a higher temperature of hot metal.The distribution ratios of titanium calculated by the model and the on-site data have the same variation with the composition and temperature of slags and hot metal,and the actual value is about 1.7 times of the calculated value. In actual production,the titanium distribution ratio between slags and hot metal can be controlled and predicted based on the established model.

Single Taper Optimization of Beam Blank Mold

Chen Wei, Guo Gaoxiang, Yu Xingwang, Wang Jiaqi, Chen Ying, Yang Gaiyan

2018, 39(4): 122-128. doi: 10.7513/j.issn.1004-7638.2018.04.021

Abstract(91) PDF(2)

Abstract:
In order to control surface cracks in blank beam during continuous casting process,the thermomechanical coupling model of heat transfer,solidification and shrinkage of slab in mold was established by using multi-load step method.According to the calculation results about air gap,based on the principle of air gap minimization,the single taper is optimized for each surface of the beam blank and the best scheme of single taper optimization is determined. After twice optimization on taper,ie,the taper of flange tip is 0.81%/m,the taper of narrow face is 0.38%/m; the taper of-1.44%/m is relatively appropriate for the fillet and flange.The calculation result indicates that the large taper of the mold is the main cause for generating the surface crack,and then it is recommended to reduce the taper.

Study on Improving Equiaxed Grain Ration of Ferritic Stainless Steel with Core Containing-Ti

Chen Yongfeng, Shi Xiaofang, Chang Lizhong

2018, 39(4): 129-136. doi: 10.7513/j.issn.1004-7638.2018.04.022

Abstract(48) PDF(1)

Abstract:
The reason and countermeasure of "ridging"defect on the surface of stainless steel products is clarified,the advantages and disadvantages of various methods to improve the solidification quality of the casting billet are analyzed. Based on the previous theoretical and experimental results,the idea of refining the solidification structure of ferritic stainless steel with the composite core containing titanium is proposed and an industrial experiment is carried out.The result shows that the proportion of equiaxed grains without Ti addition is about 30%,while the proportion of equiaxed grains with 0. 15% Ti addition is above 85%.Through counting the cores containing-Ti in the different regions of the cast billet,it can be found that 50%of the cores in the columnar grain zone is Mg-Al-Ti（ O,C）,the cores in the CET zone are mainly composed of Ti（ C,N）,Ti N and Mg-Al-Ti（ O,N） where the outer layer of the cores is Ti N,the cores in the equiaxed grain zone are mainly composed of Ti N.The results of the industrial test further prove that the core containing-Ti is the main reason for the refinement of solidification structure of the ferrite stainless steel.

Research on Large Inclusion Behavior of Carbon Structural Steel before Steel Slag Modified

Qin Shuyang, Wu Bo, Li Sheng, Wang Shuoming, Zhu Liguang, Liu Zengxun, Han Yihua

2018, 39(4): 137-141. doi: 10.7513/j.issn.1004-7638.2018.04.023

Abstract(41) PDF(1)

Abstract:
The content,type,size and origin of large inclusions in two kinds of low cost carbon structural steel Q235 D in a steel factory in north China were studied systematically by inclusion tracing.The results shows: 120 tons BOF—CC process,the average content of T[O]in steady casting billets is 76×10-6,and the average content of [N]is 28×10-6,the content of large inclusions in the steady billets is 31.3 mg/10 kg; The average content of T[O]in mixed casting billet is 82×10-6,and the average content of [N]is 30×10-6,the content of large inclusions in the mixed casting billet is 38.8 mg/10 kg.Inclusions containing only slag tracer in ladle were about 5 %,containing only about 22 % of inclusions in tundish slag,and 27% of two tracers including ladle slag and tundish slag.120 tons BOF—ladle slag modification—CC process,The tapping temperature of this process is 15 ℃ higher than that of the original process,5 kg/t ladle slag modifier and 5 kg/t lime adding ladle with deoxidizer,and stir until the end of tapping,then blowing quietly 12 min and static 20 min after cover the ladle lip,and delivery to the continuous casting.Typical final slag composition of ladle: 43% CaO,36% Al₂O₃,9% SiO₂,6% Mg O,5%（ Mn O+Fe O）.After the modification,the content of T[O]and large inclusions in the steel decreased greatly.The addition of ladle top slag modifier increases the adsorption capacity of steel slag to large inclusions significantly.It can achieve that have no nozzle clogging in 30 times pouring cycle,and the effect of modification treatment is obvious.

Microstructure Evolution of 316 Stainless Steel During Tensile Process

Sun Lingli, Ho Hsinshen, Liu Kunkun, Zhang Erliang

2018, 39(4): 142-145,151. doi: 10.7513/j.issn.1004-7638.2018.04.024

Abstract(294) PDF(8)

Abstract:
To investigate the microstructure evolution of 316 stainless steel during the slow strain tensile test,strain control is adopted and the strain rate is 10^-3 s^-1. The specimens are mechanically polished,then chemically-etched,and the tensile test is carried out. The microstructure is investigated by Scanning Electron Microscopy（ SEM）,Atomic Force Microscope（ AFM） and Ultra deep field 3D Microscope. The yield strength and tensile strength of 316 stainless steel are 319 MPa,871 MPa,respectively. And the total elongation of the sample is 41%. The surface of the sample has obvious unevenness. SEM observation shows that the grain elongates remarkably along the tensile direction as the tensile deformation increases.During the tensile process,the slip band increases gradually,and the slip band height and number increase with the stretching. In the later stage of tensile test,grain rotates and multi slips appear,which leads to the obvious roughness on the surface of sample.

Continuous Casting Process Optimization of High-strength Steel 700L Thin Slab

Hou Mingshan, Zhou Chaogang, Ai Liqun, Li Mengying, Zhang Yao, Wei Shenghui, Dong Jiliang, Lu Boxun, Li Zhonghua

2018, 39(4): 146-151. doi: 10.7513/j.issn.1004-7638.2018.04.025

Abstract(44) PDF(3)

Abstract:
In order to solve the quality problems of 700 L thin slab during Tangshan iron and steel company FTSC continuous casting,force situation of solidification shell in funnel-typed mold and FTSC（ Flexible Thin Slab Casting） spray of secondary cooling was analyzed for thin slab continuous casting,at the same time,according to the characteristics of steel,the causes of surface cracks and internal cracks of 700 L steel was analyzed in this paper.The mould taper,mould water,tundish superheat,mould powder,secondary cooling water etc processes were optimized based on the above analysis results.The results showed that surface cracks and billet internal crack of continuous casting high strength steel thin slab were effectively solved by increasing the opening taper,reducing mould water quantity,reducing tundish superheat,adjusting the viscosity and basicity of mould powder,reducing fountain volume of secondary cooling water. Through the process optimization,heat phase diagram is stabilized,surface and internal quality of thin slab are improved.

Cause Analysis of Fine Longitudinal Stripe Defect on Ferritic Rolled IF Steel

Wang Jiangong, Li Lang, Zhou Xun, Qiu Chenyang, Xia Yinfeng, Chen Yongping, Kang Yonglin

2018, 39(4): 152-158. doi: 10.7513/j.issn.1004-7638.2018.04.026

Abstract(56) PDF(2)

Abstract:
In the development of IF steel in ferrite rolling process,the fine longitudinal stripe defects had been observed on the surface of cold rolled product,and the defect is different from the conventional rolling process.In order to find the reason of causing this kind of defects and thereby solve the problem,extensive experimental analysis had been done,focusing on the microstructure and mechanical properties of the product,at the same time surface roughness measurement had been carried out on a TR200 roughness tester.Microstructural observation show there is no obvious differences in grain size of hot rolled plate,implies that fine longitudinal stripe defects of IF ferrite rolling products should be formed during cold rolling and annealing process,and might be due to the low yield strength of the finished coil. Therefore,the annealing temperature has been reduced by 20 ℃,while the hot rolling process had been optimized.The mechanics properties and microstructure of resulted IF steel coil had been improved accordingly,while the fine longitudinal stripe defects had been eliminated.

Research on Resistance Spot Welding Process of DP780 Cold Rolled Sheet

Zhou Leilei, Yu Tengyi

2018, 39(4): 159-163. doi: 10.7513/j.issn.1004-7638.2018.04.027

Abstract(32) PDF(1)

Abstract:
In this paper,the spot welding performance of DP780 cold rolled sheet was evaluated by measuring the nugget diameter and penetration rate,detecting the shear force,texting the hardness of the welded joints,amd analyzing the microstructure and morphology,in order to propose the weldable process scope and the optimized technological parameters under test conditions. The result showed that,the spot welding performance of DP780 cold rolled sheet was good. When the electrode pressure was 3 k N,the welding current could be selected from 8 to 10 k A,and the welding time could be selected from 200 ms to 400 ms,while the welding current was 10 k A,then welding time 400 ms could not be selected. When the electrode pressure was 4 k N,the welding current could be selected from 8 to 9 k A,the welding time could be selected from 200 ms to 400 ms,while the welding current was 9 k A,then welding time 400 ms could not be selected.The optimized technological parameters under test conditions are as follows: welding current 9 k A,welding time 300 ms,electrode pressure 4 k N.Microstructural observation showed that; nugget zone was composed of coarse lath martensite and ferrite,the martensite presented columnar morphology,the microstructure of HAZ was blocky martensite and ferrite; the hardness in base metal and nugget zone were 240 HV and 420 HV,respectively.

Study on Surface Modification Technology of Mechanical Steel Gasket

Gao Shengxiang, Deng Lixia

2018, 39(4): 164-167. doi: 10.7513/j.issn.1004-7638.2018.04.028

Abstract(42) PDF(1)

Abstract:
The surface modification of mechanical gasket made of 1Cr5MoVSr steel was carried out using laser-cladding technique with varying laser power,spot diameter and scanning speed.Its wear resistance and impact resistance performances were tested and analyzed. The results show that with increasing the laser power from 1 k W to 5 k W,increasing the spot diameter from 1 mm to 3 mm,and increasing the scanning speed from 2 mm/s to 8 mm/s,its wear resistance and impact resistance performances show the tendency of increasing firstly and then decreasing.In order to make suitable mechanical 1Cr5MoVSr steel gasket,the laser power,the spot diameter,and the scanning speed are preferably 3 k W,2 mm,and 6 mm/s,respectively.

Impact Performance and Wear Resistance of Automotive Flywheel Plates Subjected to Press Forging Forming

WAWang Hao, Cao Yuan

2018, 39(4): 168-172. doi: 10.7513/j.issn.1004-7638.2018.04.029

Abstract(25) PDF(1)

Abstract:
In this paper,the effects of initial forging temperature and final forging temperature on the press forging of 1045 steel for the automotive flywheel plate was investigated.The impact performance and wear resistance were tested and analyzed.The results show that when the initial forging temperature is increased from 1 150 ℃ to 1 210 ℃ and the final forging temperature is increased from 790 ℃ to 850 ℃,the impact performance and wear resistance of 1045 steel for the flywheel plate firstly increase and then decrease.The initial forging temperature of 1045 steel for the flywheel plate is preferably 1 180 ℃ and the final forging temperature is preferably 820 ℃. The impact fracture dimples of fly wheel prepared by the optimized process are very few,small and shallow,and the surface wear scratch is small,shallow,almost no skin and pits,indicating the slightest wear.

2018 Vol. 39, No. 4