钢铁钒钛

Relationship between Blast Furnace Slag Properties of Vanadium Titano-magnetite and Reduction of Vanadium Oxide

Lü Qing, Tang Qi, Sun Yanqin, Liu Xiaojie, Qie Yana

2016, 37(6): 1-4,12. doi: 10.7513/j.issn.1004-7638.2016.06.001

Abstract(81) PDF(6)

Abstract:
Due to high vanadium content in Chenggang blast furnace slag,in order to improve the reduc-tion rate of vanadium,the relationship between blast furnace slag properties and reduction of vanadium ox-ide was investigated in this paper The results show that when the combined conditions of basicity of slag R conrrolled at 1.2,~10% MgO,~14% Al₂O₃,less than 9% TiO₂ content, and the slag temperature at about 1 500℃ are used,reduction of vanadium can be improved With the content of V₂O₅ increasing,the melting temperature of the slag decreases,but its effect on the viscosity of slag is not visible

Thermodynamics for Phase Transformation in the Reduction Process of Vanadium Oxides

Tang Kai, Xuan Senwei, Xu Yang, Lü Xuewei, Bai Chenguang

2016, 37(6): 5-12. doi: 10.7513/j.issn.1004-7638.2016.06.002

Abstract(368) PDF(23)

Abstract:
The rule of step-by-step indirect reduction of vanadium oxides was calculated theoretically.It is concluded that the indirect reduction of vanadium oxides follows the rule of V₂O₅→VO₂→V₃O₅→V₂O₃→VO→V at 273~987 K while V₂O₅→VO₂→V₂O₃→VO→V at 987~2 500 K.The temperature intervals for steady existence of vanadium oxides are 273~623 K for VO₂,623~713 K for V₃O₅,713~1 393 K forV₂O₃,1 393-1 882 K for VO and 1 882~2 500 K for V,respectively.The equilibrium diagram of V-O-CO system was obtained, and the effects of pressure and activity on the equilibrium diagram were investigated.The activity of vanadium,decreases with increase in C and S content but increases with increasing the content of Si,Mn,P,V,Ti and Cr, and the initial reduction temperature of vanadium oxides turns into 1 213 K considering the influence of activity of vanadium.The initial reduction temperature of vanadium ox-ides,rising with increase of system gas pressure,reaches to 943 K,1 053 K,1 190 K,1 381 K and 1 642 K as gas pressure is 0.000 1 MPa,0.001 MPa,0.01 MPa,0.1 MPa and 1 MPa,respectively.

Thermodynamics Analysis for Redox Calcination of Titanium Slag Produced by Electric Furnace in Panzhihua

Liu Shuishi, Zhou Zhian, Guo Yufeng

2016, 37(6): 13-17. doi: 10.7513/j.issn.1004-7638.2016.06.003

Abstract(75) PDF(2)

Abstract:
The thermodynamics calculation and analysis for oxidation-reduction roasting of titanium slag produced by electric furnace in Panzhihua were carried out in this paper,based on which the phase com-positions of the oxidized products at different roasting temperatures for the titanium slag were determined by X-ray diffraction.The results indicate that rutile and M₃O₅ solid solution are formed by the oxidation of titanium and iron with lower valence in the calcination process. The reduction thermodynamics analysis shows that the trivalent iron transforms into divalent iron compounds by reduction of the oxidation calcina-tion products for the titanium slag.

Effects of FeO in Titanium Slag on Molten Salt Chlorination

Miao Qingdong, Li Kaihua, Chen Aixiang, He Anxi, Li Liang

2016, 37(6): 18-23. doi: 10.7513/j.issn.1004-7638.2016.06.004

Abstract(75) PDF(2)

Abstract:
Chemical and phase compositions of the titanium slag with different FeO contents were analyzed, and the effects of FeO content on the heat release, quantity and compositions of collected slag, molten salts compositions and product quality in molten salt chlorination process were researched.The results show that the main phases of titanium slag are anosovite, rutile and silicate vitreous.With increasing FeO content, the heat release, ratio of the collected slag, contents of FeCl₃ and FeCl₂ in the molten salts, contents of FeCl₃ and solid in the products all increase for the chlorination process.It is feasible for preparation of TiCl₄ by molten salt chlorination using titanium slag with high content of FeO.However, the compositions of molten salts and collected slag are evidently affected in the chlorination process.Thus, the ratio of materials, salte limination system and slurry spray system should be adjusted to resolve the problems mentioned above.

Study on Preparation of TiCl₄ Using Titanium-containing Carbonized Blast Furnace Slag as Raw Material

Zhang Suxin, Yang Yangjun, Lu Ping, Liu Senlin, Wang Yun

2016, 37(6): 24-28. doi: 10.7513/j.issn.1004-7638.2016.06.005

Abstract(62) PDF(11)

Abstract:
By scanning electron microscopy(SEM) and energy dispersive spectrometer(EDS), the process mineralogies of titanium-containing carbonized blast furnace slag before and after chlorination, es-pecially the influence of the mineralogical characteristics of titanium carbide on the chlorination, were studied in this paper.The effects of chlorination temperature and aeration time, chlorine concentration and particle size of the slag on the chlorination rate were investigated.The results show that 91.77% of the maximum chlorination rate of titanium carbide can be obtained with chlorination at 580℃ for 30~40 min of chlorine aeration and 50% of volume concentration for chlorine.The findings in this paper can lay a foundation for the comprehensive utilization of titanium extracted from blast furnace slag.

Study on Vacuum Distillation of Titanium Sponge Using 7.5-ton Scale I-type Furnace

Sheng Zhuo, Li Kaihua, Miao Qingdong, Li Liang, Cheng Xiaozhe, Jiang Fangxin, Xu Hucheng, Zhang Zhanpeng

2016, 37(6): 29-34. doi: 10.7513/j.issn.1004-7638.2016.06.006

Abstract(110) PDF(8)

Abstract:
This paper respectively discussed the influences of vacuum level, distillation temperature, dis-tillation load and spray water system on vacuum distillation process of titanium sponge, according to the characteristics of titanium sponge production by half-combined I-type furnace.A higher vacuum level and better gas tightness of the alembic, a smaller distillation load and directly heating the furnace to 960~1 020℃ are favorable for increasing the evaporation rate and shortening the distillation period.In addition,by using the sudden decline of vacuum degree in the top of condenser tank as the judgment for vacuum distillation channel opening and adjusting the temperature of spray water periodically, the distillation effi-ciency decrease and distillation channel blocking of I-type furnace which are caused by the gas-liquid-solid phase transformation of Mg and MgCl₂ in condenser tank are efficiently resolved.

Vanadium Microalloying for Ultra-high Strength Steel Sheet Treated by Hot-dip Metallising

Hutchinson B, Martin D, Karlsson O, Lindberg F, Thoors H, Marceau R K W, Taylor A S

2016, 37(6): 35-45. doi: 10.7513/j.issn.1004-7638.2016.06.007

Abstract(101) PDF(2)

Abstract:
Ultra-high strength steel sheets have been subjected to heat treatments that simulate the thermal cycles in hot-dip galvanising and galvannealing processes and evaluated with respect to their resulting mechanical properties and microstructures. The steels contained suitable contents of carbon(~0.2%),manganese(1.2%) and chromium(0.4%) to ensure that they could be fully transformed to martensite after austenitisation followed by rapid cooling in a continuous annealing line,prior to galvanising. Different contents of vanadium(0~0.1%) and nitrogen(0.002%~0.012%) were used to investigate the possible role of these microalloying elements on the strength of the tempered martensite. Vanadium,especially when in combination with a raised nitrogen content,helps to resist the effect of tempering so that a larger proportion of the initial strengthening is preserved after the galvanising cycle,giving tensile strength levels exceeding 1 000 MPa. Different deoxidation practices using aluminium or silicon have also been included. These showed similar strength levels at corresponding carbon contents but the bendability of the Si-killed steel sheet was considerably superior. Microstructural examinations have been made on the annealed steels but the reason for the beneficial effect of vanadium is still not fully explained. It is concluded that microalloying with vanadium is a very promising approach in the development of corrosion-resistant ultra-high strength steel sheet products.

Effects of Heat Treatment Processes on Microstructures and Properties of the Vanadium-alloyed Cold-rolled TRIP Steel

Zhang Gongting, Zheng Zhiwang, Wang Minli, Cai Xiaowen

2016, 37(6): 46-50. doi: 10.7513/j.issn.1004-7638.2016.06.008

Abstract(67) PDF(3)

Abstract:
The microstructures and properties of vanadium-alloyed cold rolled TRIP steel were investigated by salt-bath heat treatment and methods of property testing and microstructure observation. The results show that all the tensile strength of the samples can reach 700 MPa in the certain heat treatment, and the best mechani-cal properties with 514 MPa yield stress, 738 MPa tension stress, 29% elongation and 21 402 MPa·%, re-spectively, can be achieved. As the intercritical annealing temperature increasing, the volume fraction of aus-tenite increases accordingly. So the hardening phases such as bainite and martensite increase to make the strength increasing and the ductility decreasing. The positive effect of vanadium on austenite is not apparent,which may be associated with the short annealing time and the precipitation of vanadium carbides in the bain-ite zone which can reduce the stability of retained austenite by consuming the carbon element.

Thermodynamic Analysis and Experimental Research on Preparation of V-4Cr-4Ti Crude Alloy by Mg and Ca Co-Reduction

Yin Danfeng, Sun Chaohui, Chen Haijun, Du Guangchao, Jing Han

2016, 37(6): 51-55. doi: 10.7513/j.issn.1004-7638.2016.06.009

Abstract(67) PDF(3)

Abstract:
The reaction process for preparation of V-4Cr-4Ti crude alloy by Mg and Ca co-reduction was thermodynamically analyzed. The feasibility of the reactions as well as the oxidation vulnerability of Ti was confirmed by the st and ard Gibbs free energies of chemical reactions. Experiments were designed by Fact-Sage software, and the adiabatic combustion temperature of the process was calculated to be 2 657.86℃,with about 2 100℃ of estimated slag melting point and 3 499.4 J·g^-1 of unit thermal effect. The experi-mental results show that V-4Cr-4Ti crude alloy with 91.6% V, 3.57% Cr and 1.53% Ti can be obtained according to design scheme by Fact-Sage, but further refining is necessary due to the inhomogeneity of Ti and slag inclusion in the alloy.

Effect of WC Content on the Microstructure of Ti(C,N)-based Cermets

Wu Yuemei, Yi Leijuan, Wang Xinling, Xiong Ji

2016, 37(6): 56-60. doi: 10.7513/j.issn.1004-7638.2016.06.010

Abstract(61) PDF(2)

Abstract:
Mo₂C is normally added to improve the wettability between Ti(C,N) and Ni in Ti(C,N)-based cermets.Due to the increasing price of Mo₂ C,much attention has been paid to Ti(C,N)-based cermets with WC addition.In this paper,effect of WC content on the microstructure of Ti(C_0.7N_0.3)-xWC-15%Ni cermets free of Mo₂ C was studied.The experimental results show that all the WC had been solid solved with TiC_0.7N_0.3or dissolved into Ni binder phase, and all the cermets have core-rim structure.WC has a strong effect of grain re-finement on microstructure(average grain size is below 10 μm) when WC content is above 20%.

Effects of Titanium on the Performances of Magnesium-based Electrical and Electronic Hydrogen Storage Alloy

Xu Hai, Zhang Yu

2016, 37(6): 61-65. doi: 10.7513/j.issn.1004-7638.2016.06.011

Abstract(27) PDF(2)

Abstract:
In order to study the effects of titanium on the properties of Mg₂Ni hydrogen storage materials,various contents of alloying element titanium was added in the hydrogen storage alloy Mg₂Ni, and the mi-crostructure,hydrogen absorption and desorption performances and cycle stability of the material were test-ed and analyzed.The results show that titanium could refine the grain and improve the hydrogen absorption and desorption performances as well as the cycle stability of the material.Compared to the material without titanium(Mg₂Ni),the average grain size of Mg₂NiTi_0.2 alloy decreases by 55.63% while the maximum ab-sorption of hydrogen increases by 47.37%, and the discharge capacity decay ratio decreases by 48.80% after 20 times of charge and discharge cycles with hydrogen absorption saturation time and hydrogen re-lease platform pressure essentially unchanged,at the optimum content of 8.233% titanium.

Extruding Process Optimization of Magnesium Alloy Plates Containing Titanium for Numerical Control Machine

Wang Xiaofeng, Yan Xiaojun

2016, 37(6): 66-71. doi: 10.7513/j.issn.1004-7638.2016.06.012

Abstract(31) PDF(2)

Abstract:
In order to optimize the extrusion process parameters of Mg-8Al-0.5Zn-0.5Ti magnesium alloy plates containing titanium and magnesium alloy, and to provide experimental data and reference for the in-dustrial production,the extrusion experiments had been carried out on the extrusion line with various ex-trusion temperature,extrusion speed and extrusion ratio.And the resulting microstructure observation and mechanical properties test had been performed.The results showed that when the extrusion temperature in-creased from 300℃ to 360℃, and the extrusion speed increased from 1 m/min to 5 m/min,or the extru-sion ratio increased from 8 to 16,grain size of the plate was firstly refined and then coarsened, and the me-chanical properties of the plate were firstly improved and then decreased.Comparing with the extrusion temperature at 300℃,the tensile strength and yield strength of the plate extruded at 350℃ increased by 22.7% and 34.0%,respectively.The optimized extrusion temperature,extrusion speed and extrusion ratio were 350℃,3 m/min and 14,respectively.

Effect of Different Cooling Methods on Crystallization of Blast Furnace Slag

Chen Shaosheng, Zhang Yuzhu, Long Yue, Ren Qianqian

2016, 37(6): 72-75. doi: 10.7513/j.issn.1004-7638.2016.06.013

Abstract(144) PDF(16)

Abstract:
The crystallization behaviors of blast furnace slag under different cooling modes including fur-nace cooling,air cooling and water cooling were investigated by Fact Sage simulation software,XRD and SEM,to explore the influence of cooling modes on the crystallization quantity of blast furnace slag.The re-sults show that the crystallization of the slag occurs at 1 425.9℃ with melilite precipitated and is comple-ted at 1 268.5℃,with 157.4℃ of temperature range.Due to the difference in heat exchange rate,the crystallization of blast furnace slag is obviously affected by the cooling methods at the same cooling tem-perature.The highest degree of crystallization can be obtained in the slag with furnace cooling mode,while the crystallization amount distinctly decreases in the slag by air cooling with the crystals and amorphous materials coexisted. The akermanite and gehlenite are the crystals precipitated in both of the cooling modes.With the water cooling method,amorphous materials are formed under rapid cooling rate.

Effect of Dust on HCl Removal in the Process of the Blast Furnace Top Gas

Hu Xuewu, Hu Binsheng, Gui Yongliang, Hu Guiyuan

2016, 37(6): 76-80. doi: 10.7513/j.issn.1004-7638.2016.06.014

Abstract(40) PDF(2)

Abstract:
In this paper the effect of furnace dust on the HCl removal in the top gas of blast furnace had been investigated.When ash content in gas baghouse increases within the level less than 5 mg/m³,the HCl removal can be improved.When the particle size of dust is less than 38 μm,increasing size can slightly improve the dechlorination effect,however,excess size will lead to rapid removal effect decreasing. The suit-able location for installing HCl removal equipment shall be the downstream of cloth bag dust remover, and the baghouse ash through purification can be used as an active additive into blast furnace top gas dechlorination agent.The gravity dust will deteriorate the effect of removing chlorine in the blast furnace top gas.

Influence of Diluents on the Performances of High Solid Anti-corrosion Coating Prepared by Converter Dust

Huo Dongxing, Liang Jinglong, Li Hui, Xie Shanshan, Hao Fei

2016, 37(6): 81-85. doi: 10.7513/j.issn.1004-7638.2016.06.015

Abstract(36) PDF(2)

Abstract:
In order to study the effects of diluent on the performances of the coatings prepared by converter dust,high solid anti-corrosion coatings were prepared by the converter dust with an average particle size of 59.33 μm.Using benzyl alcohol as the diluent,its effect of addition amount on the properties of the high solid anti-corrosion coatings was investigated.With increase of the diluent content,the viscosity of high sol-id anti-corrosion coatings reduces coupled with the decrease in surface bubble content of the coating film, and the corrosion resistance to salt water for the coating film decreases but its acid corrosion resistance in-creases.When the dosage of diluent is 15%,the coating film is more resistant to acid corrosion.

Study on Modification of Titanium Gypsum by Mineralizers

Li Liang

2016, 37(6): 86-90. doi: 10.7513/j.issn.1004-7638.2016.06.016

Abstract(43) PDF(3)

Abstract:
Titanium gypsum is a by-product of titanium dioxide production by sulphate process,with calcium sulfate dihydrate as the main phase accompanying a small quantity of dolomite.The main impurities of titanium gypsum include Fe₂O₃,Al₂O₃,SiO₂,MgO and TiO₂,which will affect the condensation properties of titanium gypsum and reduce the condensation strength. In order to improve the condensation strength of titanium gypsum,modification of titanium gypsum was carried out respectively using the silicate cement clinker,silica powder and fly ash as mineralizer.The order of modification effect for the selected mineralizers is silicate cement clinker ﹥ silica powder ﹥ fly ash.The effect of multiple mineralizers on the titanium gypsum modification was investigated by orthogonal experiments, and the optimal formula was confirmed to be 16% silicate cement clinker,6% silica powder and 3% fly ash.

Influence of Additive on Viscosity and Perovskite Precipitation of Titania Bearing Blast Furnace Slag

Zhu Ertao, Lu Jianguang, Li Fumin, Lü Qing, Qie Yana

2016, 37(6): 91-98. doi: 10.7513/j.issn.1004-7638.2016.06.017

Abstract(63) PDF(4)

Abstract:
The vanadium titano-magnetite slag from Chengde iron & steel company is characterized by high viscosity,difficult in separation of the slag-iron higher hardness.The study has been done to decrease the viscosity and hardness of the vanadium titano-magnetite slag.The results show that the viscosity decreases from 1.632 Pa·s to 0.880 Pa·s with the additive amount of CaF₂ increasing.The viscosity first decreases from 1.632 Pa·s to 1.104 Pa·s and then increases from 1.104 Pa·s to 1.296 Pa·s with the additive a-mount of precipitator dust increasing.The viscosity first decreases from 1.632 Pa·s to 1.024 Pa·s and then increases from 1.024 Pa·s to 1.664 Pa·s with the additive amount of coal fly ash increasing.Among the three cooling strategies of water-cooling,quenching and slow cooling,the precipitated amount of perovskite increases with the rate of cooling decreasing.Under the water-cooling condition,for both of original slag and with 2% coal fly ash,the precipitation area of perovskite is small,but the precipitation area of perovskite in the slag with CaF₂ addition is big.Under the quenching condition,the precipitated amount and the crystal size of perovskite increases with the additive amount of CaF₂ increasing,while the precipitated amount of perovskite decreases with the addition of 2% coal fly ash.Under the slow cooling condition,the precipitated amount and the crystal size of perovskite increases with the additive amount of CaF₂ increasing,while the precipitated amount of perovskite changes a little with the addition of 2% coal fly ash.

Study on Dealkalization Capacity of BF Slag with Low Titanium Content

Dong Xiaoxu, Zhang Shuhui, Lan Chenchen, Lü Qing

2016, 37(6): 99-102. doi: 10.7513/j.issn.1004-7638.2016.06.018

Abstract(28) PDF(3)

Abstract:
According to the dealkalization capacity of blast furnace(BF) slag with low titanium content in an integrated iron and steel company were tested and analyzed, the effects of w_CaO/w_{SiO₂,w_MgO,w_{Al₂O₃,w_{TiO₂ and initial alkali content on dealkalization capacity of BF slag were studied.The results show that:with the increase of w_CaO/w_{SiO₂,w_MgO and initial alkali content,the dealkalization capacity of BF slag decreases gradually.With the increase of w_{Al₂O₃,the dealkalization capacity of BF slag increa-ses.The dealkalization capacity increases slowly with the increase of w_{TiO₂.w_CaO/w_{SiO₂ and w_MgOshould be properly reduced in BF production,w_CaO/w_{SiO₂ and w_MgOshould be kept at 1.05~1.10 and 7%~8%.w_{Al₂O₃can be appropriately increased,w_{TiO₂can be decreased appropriately.The amount of alkali entering into the BF should be reduced,in order to reduce the degree of harmness to the BF.}}}}}}}}}}

Controlling Rephosphorization of Bearing Steel During Secondary Refining

Wang Le, Liu Liu, Wang Pin

2016, 37(6): 103-108. doi: 10.7513/j.issn.1004-7638.2016.06.019

Abstract(67) PDF(5)

Abstract:
Based on field experiments,the amount of rephosphorization quantity,the P content of alloy and auxiliary materials and the quantity of tapping slag were calculated in order to effectively control liquid steel rephosphorization.The effects of slag composition and temperature on the rephosphorization were also analyzed in the paper.The results show that the rephosphorization caused by alloy addition and tap-ping slag were the dominant roles contributing to the total rephosphorization quantity.Adding alloy with low P content and decreasing the tapping slag amount could effectively reduce the rephosophorization quantity.Controlling tapping temperature at~1620℃ and the content of FeO greater than 15% were necessary measurement in order to reduce rephosphorization.During secondary refining,controlling the slag basicity and the content FeO of refining slag ranging from 0.25% to 0.45%,liquid steel rephosphorization can be effectively controlled.

Composite Dephosphorizer Microwave High-phosphorus Iron Ore Roasting Process

Wang Xiaoyuan, Zhang Wei, Xing Hongwei, Tian Tielei, Wang Hui

2016, 37(6): 109-112,119. doi: 10.7513/j.issn.1004-7638.2016.06.020

Abstract(39) PDF(2)

Abstract:
In order to achieve high gasification dephosphorization of high-phosphorus iron ore after sintering,promote the development and utilization of high-phosphorus iron ore,the influence of material com-position on the gasification dephosphorization rate had been investigated via microwave heating. When u-sing bituminous coal,5% C/O,0.75% SiO₂ addition,1.5% CaCl₂ addition and 1.4 of alkalinity, high-phosphorus iron ore fines could be achieved 20.36% of gasification dephosphorization in the microwave field. X-ray diffraction(XRD) results on the calcined product found out that excessive addition of CaCl₂ would produce Ca₅(PO₄)₃Cl, and not favorable for gasification dephosphorization.

Effect of Mineral Materials on Crystallization Phases in Flux Film

Zhang Di, Liu Lei, Han Xiuli, Li Mingduo, Deng Meile

2016, 37(6): 113-119. doi: 10.7513/j.issn.1004-7638.2016.06.021

Abstract(37) PDF(3)

Abstract:
Due to the frequent surface defect happened to the peritectic steel slab, the effects of raw mineral materials on the properties and crystallization characteristics of mold flux were investigated using process mineralogy in this study. Mold flux were mainly prepared using cement clinker and industrial mineral materials under laboratory conditions, the crystallization phases of the flux film were systematically i-dentified and quantitatively analyzed. According to the analysis, the crystallization ratio of all the flux films reached more than 55% with additional mineral materials, and the main phases of the flux films are wollastonite and cuspidine. As the quartz(6%~24%) or wollastonite(11%~19%) addition increasing,viscosity and heat flow density of flux film increase, which facilitate the growth of wollastonite in the flux film. Whereas, with increasing fluorite(8%~16%) or soda ash(10%~18%), the viscosity of flux film decreases, which promote the cuspidine content increase and thus heat transfer of flux film. When the quartz and wollastonite addition exceeded, it will lead to a large number of wollastonite and few cuspidine, the excessive fluorite and soda ash addition will lead to mass cuspidine and few wollastonite.

Formation Mechanism and Prevention Measurements of Macro-segregation during Continuous Casting Solidification

Zhao Junpu, Liu Liu, Wang Le

2016, 37(6): 120-126. doi: 10.7513/j.issn.1004-7638.2016.06.022

Abstract(300) PDF(20)

Abstract:
The macro-segregation of alloying elements during continuous casting steel has adverse effect on the quality of steel product.The nature of macro-segregation in casting is physical movement of liquid phase or solid phase during solidification.The causes of molten steel flow in continuous casting process were sum-marized,such as forced convection by external force,bulging and solidification shrinkage.Accordingly,the mechanisms of macro-segregation caused by these factors were analyzed. To solve macro-segregation,the technologies such as low superheat pouring,electromagnetic stirring and liquid core reduction at the end of solidification were applied.However,practice result shows that this problem could not be solved by using every individual technology alone.In order to improve the composition uniformity of continuous casting product,it is advised that the corresponding measurements should be adopted for each type of segregation.

Simulation Research on Bottom Blowing System of 65 t Ladle Based on Fulent Software

Yang Zhaojun, Ceng Yanan, Li Junguo

2016, 37(6): 127-132. doi: 10.7513/j.issn.1004-7638.2016.06.023

Abstract(60) PDF(6)

Abstract:
According to the practical conditions of 65 t ladle,the effects of bottom blowing design and process parameters on slag entrapping,turbulent kinetic energy and lining Erosion of the ladle has been investigated by Fluent s of tware.Under the condition of 100 L/min bottom blowing,slag entrapping will not readily occur because the steel flow velocity on steel-slag interface ranges from 0.15~0.2 m/s,which is less than critical velocity 0.229 m/s at which slag entrapping can happen.The distribution of turbulent kinetic energy is reasonable when the intersection angle and the center distance of bottom blowing were 180° and 0.6R,respectively.Under this constructional condition,the predicted mixing time by Fluent soft-ware is good agreement with that of the cold model experiment.The standard error is within 5%,showing the good reliability of the numerical simulation.

Effect of Bainite Isothermal Time on Microstructure and Mechanical Properties of Ultra-high Strength Cold-rolled Transformation Induced Plasticity Steel

Tang Jianwei

2016, 37(6): 133-136. doi: 10.7513/j.issn.1004-7638.2016.06.024

Abstract(62) PDF(3)

Abstract:
In the paper, C-Si-Mn steels were soaked at 800℃ for 120 s, and then rapidly cooled to 350℃ and held for 100~1 000 s to simulate the bainite isothermal transformation process. The influence of bainite isothermal time on the microstructure and mechanical properties of ultra-high strength cold-rolled transformation induced plasticity(TRIP) steel was investigated by means of scanning electron microscopy(SEM) and tensile test. The results showed that the microstructure of cold-rolled TRIP steel was com-posed of ferrite, bainite, martensite and retained austenite. The bainite and retained austenite formed in the isothermal stage, and the martensite isl and formed in the final cooling stage after isothermal process.With an increase in the bainite isothermal time, the solute C atoms fully diffused into the retained austen-ite due to the transformation of the supercooled austenite into bainite. Therefore, the average solute C content in the austenite increased due to the enrichment of solute C atoms and the decrease of the austen-ite volume fraction. And the martensite volume fraction reduced, and the retained austenite volume frac-tion increased. As a result, with an increase in the isothermal time from 100 s to 1 000 s, the yield strength increased from 596 MPa to 692 MPa, the tensile strength decreased from 1 455 MPa to 1 138 MPa, the YS/UTS ratio increased from 0.41 to 0.60, and the elongation decreased from 6.2% to 18.9%.The cold-rolled ultra-high strength TRIP steel with excellent comprehensive mechanical properties(R_m×A=21 510 MPa·%) was obtained at 1 000 s of bainitic isothermal holding.

Study on the Transformation Induced Plasticity Steel of 780 MPa Grade Cold Rolled

Wang Minli, Xin Yunchang, Zheng Zhiwang

2016, 37(6): 137-141. doi: 10.7513/j.issn.1004-7638.2016.06.025

Abstract(60) PDF(2)

Abstract:
The microstructure of transformation induced plasticity steel(TRIP) is composed by ferrite,martensite and retained austenite, and have high qualified steel plate with high strength and good plastici-ty.To study super-cooled austenite transformation under the condition of continuous cooling,the determi-nation of continuous cooling transformation curve had been done, and the influence of cooling rate on mi-crostructure and hardness had been investigated.The results showed that the phase transition area included A to P transition zone, and A to B transition zone and A to M transition zone.When the cooling rate was increased to 2℃/s,both A to P transformation and A to B transformation occurred.When the cooling rate was increased to 3℃/s,only A to B transformation took place.When the cooling rate was increased to 10℃/s,A to M transformation occurred.Based on the experimental results,the industrial production have been done and achieved satisfied TRIP 780 strip where the yield strength,tensile strength and elongation A₅₀ and n value were 535 MPa,815 MPa,29.5% and 0.25,respectively.

Effects of Ti on Hardenability of Boron-bearing Track Steel

Guo Yuehua, Liu Ming, Deng Tongwu, Li Hongguang

2016, 37(6): 142-145. doi: 10.7513/j.issn.1004-7638.2016.06.026

Abstract(68) PDF(3)

Abstract:
In this paper the effects of Ti on the hardenability of boron-bearing track steel had been inves-tigated through Jominy end quench test and microstructure observation. It is found out that when Ti/N ra-tion is less than 5.2, the hardenability of boron steel increase with Ti/N increasing. The hardenability keep constant under condition of 5.27.3, the hardenability will decreases with increasing Ti/N. The suitable Ti addition should be controlled at 4.0

Measurement of Continuous Cooling Transformation Curve and Effect of Cooling Rate on the Inclusion and microstructure of DH36 Steels

Gao Lina, Zhang Caijun, Gu Kejing

2016, 37(6): 146-151. doi: 10.7513/j.issn.1004-7638.2016.06.027

Abstract(101) PDF(1)

Abstract:
The temperature-expansion curves under different of cooling rates of DH36 steels had been measured by high temperature phase transformation quenching instruments.The CCT curves of the steels had been determined by using the expansion method and observing the microstructure of the steels.The influence of different cooling rates on the inclusion size, quantity and microstructure had been studied.The results showed that the range of cooling rates for achieving acicular ferrite is 0.3~3℃/s and the optimum cooling rate is 1℃/s.With the increase of cooling rates, the number of the inclusions decreases first and then in-creases.The size of inclusion is mainly between 0~2 μm, and is suitable for inducing nucleation of acicular ferrite.The nucleation of acicular ferrite has not always been increased with the increase of inclusion num-ber.There is an optimal combination of number of inclusions and the nucleation of acicular ferrite.

Influence of Quick Cooling Process Parameters after Rolling on Reinforcing Steel Bar Performance

Ma Jinjiang

2016, 37(6): 152-156. doi: 10.7513/j.issn.1004-7638.2016.06.028

Abstract(74) PDF(1)

Abstract:
Using the quick cooling device located at the exit of final bar mill st and,The influence of main process parameters on the properties of reinforcing steel bar was tested and analyzed.The results show that the interval time between the final st and and the initial cooling can be shortened to increase the strength of reinforcing bar.Increasing water flow,cooling time or cooling water pressure can improve the strength of reinforcing bar,but it will decrease the elongation.Reducing self tempering temperature can increase the strength of reinforcing bar,but it will also decrease the elongation.Based on the research results,using the steel grade of Q235 produced at a overseas bar mill,controlling the self tempering temperature of Ø18 mm rebar in 570~630℃,Ø22 mm rebar in 550~650℃ and Ø25 mm in 460~520℃,it can obtain qualified reinforcing steel bar in accordance with the national st and ard.

2016, 37(6): 157-158.

Abstract(26) PDF(2)

Abstract:

2016 Vol. 37, No. 6