Abstract: M-phase vanadium dioxide (VO2) is a major thermally induced phase change material with a phase change temperature of 68 ℃. Due to obvious changes in physical and chemical properties before and after the phase change, M-phase VO2 can be widely used in the fields of phase change energy saving and sensing. Based on vanadyl oxalate as precursor in this particle, monoclinic phase vanadium dioxide with ultrafine particles was directly prepared by a thermal decomposition process in an inert gas atmosphere. The influences of reaction conditions on the phase purity of the product were explored, including pyrolysis temperature, pyrolysis time and gas flow rate. Under the optimal preparation conditions, relatively pure M-phase VO2 with ultrafine particles was prepared. The morphology and phase change properties of the products were characterized by scanning electron microscope and differential thermal analyzer. The obtained ultrafine particles in M-phase VO2 were mainly cuboid-like micron-sized particles, with irregularly shaped nano-sized fine particles attached to the surface. The average size of micron and nano particles were respectively 5.76 μm and 177.21 nm. The phase transition temperature was about 65 ℃. The method is simple, efficient, and easy to scale up to prepare M-phase VO2 with ultrafine particles.
Abstract: Based on non-isothermal thermogravimetric analysis, the influences of Na2CO3 addition and heating rate on oxidation of vanadium removal slag of titanium tetrachloride (vanadium-containing tailings) were studied. The Kissinger-Akahira-Sunose (KAS) method was used to calculate the activation energy and pre-exponential factor of the oxidation process of vanadium-containing tailings. Through the Coats-Redfem method, the mechanism function was inferred and the kinetics equations of different stages were established. The results show that the temperature for complete oxidation of the vanadium-containing tailings is 700 ℃. With the increase of Na2CO3 addition, the apparent activation energy gradually decreases and the oxidation rate increases. While the Na2CO3 addition exceeds 20%, the glassy phase appears during the oxidation roasting process which results in sintering, and the apparent activation energy gradually increases with the oxidation rate decreased consequently. The sodium roasting process can be divided into four stages and the kinetics equations are as follows: the first stage of two-dimensional diffusion with dα/dT=exp(−72.03/RT)4(1−α)1/2[1−(1−α)1/2]20.022/β, the second stage of three-dimensional diffusion with dα/dT = exp (−23.7/RT)3/2(1−α)4/3[(1−α)−1/3−1]−10.014/β, the third stage of chemical reaction with dα/dT=exp(−27.91/RT)(1−α)20.06/β and the fourth stage of nucleation and growth with dα/dT=exp(−12.09/RT)2(1−α)[−ln(1−α)]1/20.14/β.
Abstract: Regarding the problem that low acidolysis rate occurs frequently at the beginning of the experiment in low-grade titanium slag, an investigation was proposed to elaborate the relationship among the phase composition, acidolysis temperature curve, and standard heat of reaction for the chemical reaction in low-grade titanium slag and slag 74 (the titanium slag is 74%). Moreover, the effects of acid concentration, initiation temperature, primary reaction time, and acid-slag ratio on the acid hydrolysis rate of low-grade titanium slag were also investigated. The results show that the low acidolysis rate in low-grade titanium slag is not caused by the formation of the insoluble sulfuric acid phase but is related to the acidolysis reaction rate. One of the main reasons for the increasing acidolysis reaction rate and the decreasing primary reaction time in low-grade titanium is the increased initiation temperature. Appropriately reducing the initiation temperature can meet the demand of external heating to supplement heat for acidolysis in low-grade titanium slag. The acidolysis rate of slag 1# increases from 78.98% to 94.31%, and that of slag 2# increases from 71.77% to 91.19%, respectively, by reducing the concentration of reaction acid and the initiation temperature and prolonging the primary reaction time. In addition, compared with the phase of the residue obtained before optimization, the peak value about M2TiO5 is decreased, and a new phase (Ca(Mg,Fe,Al)(Si,Al)2O6) is formed in the phase of the residue.
Abstract: Calcification roasting-acid immersion is a very promising clean process for vanadium extraction, but the resultant acidic vanadium solution contains a higher content of manganese, which seriously affects the quality and application of vanadium products. Thus the removal of manganese from the acidic vanadium solution is urgently needed. This paper summarized the removal of manganese from different solution systems at home and abroad. The principles, operational conditions and efficiency of removing manganese from different solutions were expounded and the feasibility for removal of manganese from the acidic vanadium solution via different methods were discussed, which will provide a theoretical and technical guidance for removal of impurity manganese in acidic vanadium solution with high efficiency, high selectivity and low cost. Based on the specific requirements for selecting remover and methods to remove the manganese from the acidic vanadium solution, ammonium persulfate oxidation method, solvent extraction method and ion exchange method are theoretically suitable for removing impurity manganese from this solution system. However, the specific removing efficiency, operational conditions and acting mechanism need to be further studied.
Abstract: Vanadium slag and sodium peroxide (Na2O2) were mixed, briquetted, roasted, and leached to rich vanadium into V2O5. The effects of roasting temperature, briquetting pressure, roasting time, Na2O2 content, and leaching temperature on the vanadium leaching rate were studied. The results showed that the vanadium leaching rate first increased and then decreased as the molar ratio of Na2O2 to V2O5 increased from 0.5∶1 to 4∶1, the roasting temperature increased from 700 ℃ to 1000 ℃, and the briquetting pressure increased from 1 MPa to 25 MPa. The vanadium leaching rate reached the maximum 95.57% with the Na2O2/V2O5 of 3∶1, the roasting temperature of 850 ℃, and the pressure of 5 MPa. As for the roasting time in the range of 0.5–2.5 h and the leaching temperature of 60–100 ℃, the vanadium leaching rate fluctuated and reached the maximum at 2.5 h and 80 ℃. Under the optimum conditions, the vanadium leaching rate reached 95.57%. Meanwhile, the phases during roasting were analyzed and characterized by X-ray diffraction and electron probe microanalysis. The results showed that the main phases were Fe2O3, Fe3O4, Ca(TiO3), Na3VO4, Mg0.165Mn0.835O. Finally, ammonium salt was added into the leaching solution containing vanadium, and 96.84% V2O5 was obtained through precipitation and calcining process.
Abstract: The sources of impurity Al in titanium sponge produced by the Kroll process were analyzed. The impurity Al is mainly derived from titanium tetrachloride and magnesium. Based on the source analysis of Al in titanium tetrachloride, water vapor was introduced for Al removal from titanium tetrachloride during the chlorination process, where 84.22% of Al removal ratio can be obtained at 10 kg/h of water dosage. At the same time, Al in magnesium was removed by adding refining agent, and a favorable effect can be obtained at 20 kg/t of refining agent amount. Influenced by the reaction process for titanium sponge formation, Al is not evenly distributed in titanium sponge. Therefore, it is necessary to carry out Al removal measures from the source materials to produce high-quality titanium sponge.
Abstract: The in-situ formed (Ti5Si3 + TiBw)/TC11 composites with network structure were prepared by powder metallurgy. The metallographic structure, microstructure, mechanical properties and fracture surface of (Ti5Si3 + TiBw)/TC11 were analyzed. The results show that TiBw and partial Ti5Si3 distribute around the matrix particles in a quasi continuous network. The rest of Ti5Si3 distributes around the matrix, in β-Ti and at the boundary between α-Ti and β-Ti. With the increase of Si content, the in-situ reinforcement of Ti5Si3 increases, and α-Ti changes from long flake shape to short rod shape and tends to be equiaxed, which can refine the microstructure obviously. TiBw and Ti5Si3 play the role of load transfer and phase boundary strengthening, which can reduce the matrix connectivity and refine the matrix microstructure simultaneously. It is found that the strength of the composites is improved accompanying partial decrease of plasticity of the matrix. The strength and plasticity of the composites first increase and then decrease with increase of Si content. The composite of (2vol.%Ti5Si3+5vol.%TiBw)/TC11 has the highest tensile strength and compressive strength respectively at 1 105.8 MPa and 1 870.6 MPa, showing excellent mechanical properties. The fracture morphology of (Ti5Si3+TiBw)/TC11 composites is mainly dimple, and the reinforcements of Ti5Si3 and TiBw can slow down the crack propagation during the fracture process.
Abstract: The optical microscope (OM) was employed to investigate the influence of heat treatment on microstructure evolution of ZTC4 titanium alloy, and the relationship between microstructure and mechanical properties was discussed. The results showed that the ZTC4 titanium alloy casting was composed of martensitic phase α′. A typical Widmanstatten microstructure was always obtained after annealing or hot isostatic pressing followed by annealing heat treatment. The tensile strength of ZTC4 titanium alloy casting after annealing can reach 955 MPa, and its elongation and reduction of area were only 8.8% and 13.1%, respectively. After hot isostatic pressing followed by annealing heat treatment, the tensile strength was reduced to 892 MPa, but its elongation and reduction of area were increased to 11.2% and 21.4%. The hot isostatic pressing heat treatment can break the original β phase grains, which improve the plastic properties of ZTC4 titanium alloy.
Abstract: The research on welding process and weldability of TC4 titanium alloy has been widely concerned at home and abroad. Therefore, this paper mainly reviewed the current research progress of the effect of laser welding process on the geometrical dimensions, microstructure and mechanical properties of thin plate TC4 alloy. The weld geometrical dimension and microstructure transformation as well as the related mechanism were analyzed and discussed. It is found that the change of weld geometrical dimension is mainly due to the variation of welding heat input, which leads to the change of laser welding keyhole shape and mode. The increase of welding heat input causes the transformation of the microstructure. The acicular martensite α' phase is the main strengthening phase, with the blocky αm and Widmanstatten α phase as the main malleable phases. The laser energy should be strictly controlled to improve the welding quality in actual production applications.
Abstract: Industrial V-Mo/Ti denitration catalyst was modified by phosphorus (P) via impregnation method to enhance the catalytic performances. The catalyst was characterized by XRD, N2 adsorption and desorption, XPS, H2-TPR and UV-vis. The denitration activities of the catalyst were tested on a fixed-bed micro-reactor. The results show that phosphorus has little impact on the crystallographic form and pore structure of the catalyst. The presence of P could increase the polymeric vanadate of the catalyst, leading to the increase of (V3++V4+)/V5+ ratio and chemisorbed oxygen. This tendency becomes more obvious with the increase of calcination temperature, which is beneficial to the improvement of denitration activities of the catalyst. Besides, the presence of P also affects the acidity of the catalyst. The V-Mo-P/Ti catalyst exhibits relatively higher acidity than that of the V-Mo/Ti catalyst at lower calcination temperatures (≤500 ℃). However, high calcination temperature results in the increase of P2O5, and the acidity of the catalyst decreases accordingly. The catalyst roasted at 500 ℃ exhibits the best catalytic activity and high resistance to SO2 and H2O, possessing a promising perspective for industrial application.
Abstract: The characteristics of the photocatalysts can be prepared using Ti-bearing blast furnace slag containing TiO2 to realize Ti-bearing blast furnace slag′s high added value and reasonable comprehensive utilization. Photocatalytic material derived from vanadium and nitrogen co-doped Ti-bearing blast furnace slag was produced by two-step doping approach (high-temperature solid-phase sintering method was used to adulterate vanadium source and liquid-phase method was used to adulterate nitrogen source). The raw material was Ti-bearing blast furnace slag produced from Pangang. At the same time, ammonium nitrate and ammonium metavanadate were carried out as the nitrogen source and the vanadium source, respectively. The effects of calcination temperature, doping amount and calcination time on the degradation rate of simulated pollutant methylene blue solution were investigated under ultraviolet light, and SEM and XRD characterized the photocatalytic activity. The results show that the co-doping of vanadium and nitrogen has a negligible effect on the crystal structure of blast furnace slag but can increase the specific surface area of blast furnace slag and improve its photocatalytic activity. The N/Ti molar ratio is 30% and the mass percentage of ammonium metavanadate TiO2 was 45% when the calcination temperature was 300 ℃. In addition, the degradation rate of the prepared vanadium and nitrogen co-doped Ti-bearing blast furnace slag photocatalyst reached 97.0% when the calcination time was 2 h, which was 47.0% higher than that before doping.
Abstract: Deform software were employed to simulate hydraulic press and hammer press forging processes of TA15 titanium alloy, and two kinds of forging equipment were used to produce TA15 titanium alloy forgings. The results show that when hydraulic module of deform software is used to deform TA15 titanium alloy, the equivalent strain distributes symmetrically along the thickness direction, and the equivalent strain at the center is the largest. However, the equivalent effect near the lower die becomes smaller and the equivalent effect near the upper die becomes larger. The center thickness of lamellar α phase is higher than that of surface. The thickness of lamellar α phase is fine than produced by 400 kJ counter hammer of TA15 titanium alloy. The tensile strength of TA15 titanium alloy forgings at the surface is higher than that of center. The tensile strength of TA15 titanium alloy forging produced by 400 kJ counter hummer is higher.
Abstract: This paper used the sol-gel method to prepare Fe3+ doped GO-TiO2 films with different proportions on glass substrates. The samples were characterized by X-ray diffraction (XRD) and ultraviolet-visible spectrometer (UV-Vis). The photocatalytic degradation of TCM was irradiated under a UV lamp with a power of 20 W and wavelength of 254 nm for 210 min to investigate the effects of Fe3+ doping ratio, film calcination temperature, film layers, and film reuse times on the degradation. The results show that the samples are anatase, and the doping of Fe3+ reduces the crystal size, and a redshift occurs. The degradation effect of TCM increases with the increase of Fe3+ doping ratio, and the film formed by calcination at 400 ℃ is the best. Whether Fe3+ is doped or not, multiple coating can improve the degradation rate of TCM. The degradation ability of each film tends to be stable after being reused four times.
Abstract: Steelmaking slags containing large amounts of Ca silicate is a potentially alkaline waste that can be used to capture CO2 to synthesize high-quality CaCO3. Here, effect of ultrasonic on leaching efficiency and selective leaching rate of Ca in steelmaking slags was studied in acetic acid solution. Experimental results shown that ultrasound could help to strengthen leaching of Ca in acetic acid solution. Ultrasonic power, liquid-solid ratio, and initial acetic acid solution concentration were positively correlated with Ca extraction, but particle size of steelmaking slags and temperature were negatively correlated with Ca extraction. Meanwhile, temperature and initial concentration of acetic acid solation had a negative correlation to selective extraction yield of Ca, which were beneficial for the diffusion of impurity elements. Also, ultrasonic power and solid to liquid ratio were insignificant effect to selective extraction yield of Ca, but increase of ultrasonic power and solid to liquid ratio were also helpful to the diffusion of impurity elements. It was worth noting that decreasing grain size of steelmaking slags would raise selective leaching efficiency of Ca and the maximum selective leaching rate upped to 96.7%. During leaching process, ultrasonic could effectively break and remove the porous passivation layer formed by residual silica on surface of steelmaking slags particles, and improved leaching rate of Ca.
Abstract: Corundum slag is a solid waste produced in smelting 50 or 80 vanadium iron by thermite process. In order to improve the utilization value of corundum slag, the primary raw materials in this investigation were corundum slag, ferrosilicate, limestone, calcium carbide and sodium carbonate, respectively. Moreover, the silicon-vanadium alloy was prepared by electric furnace smelting. Limestone was selected as a slag-forming agent to investigate the effect of the addition amount of limestone on the slag phase and the yield of vanadium. The results show that the recovery rate of vanadium can reach 96.5% when the content of CaO in the final slag is 22%. The yield of vanadium increases to the maximum of 96.2% when the silicon blending coefficient increases to 105% under ferrosilicon are selected as reducing agent condition. Moreover, the dephosphorization rate increases to the maximum of 72% when the addition amount of CaC2 reaches 3.5% under calcium carbide is selected as a dephosphorization agent condition. In addition, the desulfurization rate increases from 70% to 86% when the CaO content in the slag increases from 16% to 22% by using CaO+2%Na2CO3.
Abstract: The mix proportion of high titanium heavy slag concrete (HTHS) and normal concrete was designed. Four groups of concrete cubic and prism specimens were made and tested. Using the PFC discrete element software, the meso-structure mechanical parameters of HTHS and normal concrete specimen were calibrated. Uniaxial compressive tests of prism-shaped specimens made of HTHS and normal concrete were simulated. Furthermore, the failure phenomena and reasons of HTHS concrete prism specimens were analyzed. It is found that the strength of HTHS aggregate is decreased due to the holes within HTHS aggregate. The bonding strength of the interface transition zone between coarse aggregate and harden mortar is improved. In addition, the failure modes of HTHS and normal concrete are different. The failure surfaces of HTHS concrete pass through the coarse aggregate and hardened mortar, while the failure surfaces of normal concrete can only develop along the interface transition zone and pass through the harden mortar.
Abstract: Vanadium-titanium magnetite has its unique characteristics like containing many valuable elements, complex phase structure and close intergrowth of iron and titanium, as well as the difficulty of full comprehensive utilization. In this paper, the phase change of vanadium-titanium magnetite reacted with Na2CO3 at high temperature were studied, and the influence of temperature and biomass sawdust on the metallization rate of the reduction product was discussed. The results show that the addition of Na2CO3 can promote reaction of vanadium-titanium magnetite with H2 and favour reducing the iron-titanium oxide in vanadium-titanium magnetite with H2. Increasing the temperature and addition of biomass sawdust both are beneficial to reduction of vanadium-titanium magnetite by H2. The is. When the reducing temperature is 1100 ℃, the metallization rate of vanadium-titanium magnetite can reach 80.22%, and the metallization rate can be increased to 84.47% by adding biomass sawdust under same conditions. The use of H2 to reduce vanadium-titanium magnetite while adding biomass sawdust is expected to achieve high-efficiency enrichment of iron.
Abstract: In this investigation, the low-alloy steel wire applied in additive manufacturing was made by clean steelmaking, hot rolling and drawing; subsequently, laser wire-feed additive manufacturing was carried out with this steel wire. The mechanical properties of the 3D printed parts are the yield strength of 857 MPa, the tensile strength of 930 MPa and the elongation of 18%, the average low-temperature impact toughness of −40 ℃ reaches 118 J, respectively, whose can meet the requirements of 900 MPa class in the marine engineering field by the method of additive manufacturing. In terms of scanning electron micrograph (SEM) and transmission electron microscope (TEM), and analysis of the microstructure of the printed pieces, the results showed that the microstructure was composed of granular bainite, lath bainite and diffusely distributed martensite-austenite constituents on the bainitic matrix, whose could improve the tensile property and impact property simultaneously.
Abstract: Based on the classical model of collision aggregation of inclusions, the growth mode of exponential increase of inclusions is used to establish the numerical model of reaction of aluminum and oxygen, collision and aggregation of inclusions, remove of inclusions, for the purpose of predicating the mass fraction and distribution of inclusions during the process of RH. The simulated results are found out good agreement previous findings from the developed model, the mass fraction of inclusions is sharply increasing with the plunge of aluminum. The mass fraction of inclusions increases from 0 to 0.0065% after 300 s circulation. Then the mass fraction reaches the maximum value. Afterwards the inclusions begin to remove because of the float and adsorption by the wall and the top slag of RH. The mass fraction of inclusions decreases to about 0.01% after 900 s circulation. The percentage of inclusions removal is 84.6%. The circulation has effectively removed the inclusions in RH. After 900 s circulation the maximum mass fractions of inclusions of diameter 2 μm and 50.8 μm are 0.000 02% and 0.0078% respectively.
Abstract: Based on the principle that electromagnetic force affects the distribution of non-metallic inclusions and the velocity of particles in molten metal, the effect of electromagnetic stirring in mold on the removal of non-metallic inclusions in billet was studied. The inclusion separation and removal experiments were carried out by using EMS current of 200, 250 and 300 A, and the samples were collected for energy spectrum analysis. The results show that the best control effect of non-metallic inclusion in the billet is obtained when the electromagnetic stirring parameters of the mold are 300 A current and 3 Hz frequency, which is 35% less than that without electromagnetic stirring.
Abstract: The development of vibration introduced into the metal solidification process was reviewed and the vibration methods, application fields, metallurgical effects, and advantages/disadvantages of mechanical vibration technology, vibration excitation nucleation technology, ultrasonic vibration technology and pulsed magnetic oscillation technology used for controlling metal solidification process were mainly summarized. Meanwhile, the modes and mechanisms of four kinds of vibration techniques were explored, and the impact of vibration on the solidification of molten metal and the specific forms were discussed. The mechanism of the existing vibration techniques improving solidification structure was discussed, and recent development of vibration technology used in the metal solidification process were summarized. A brief analysis and prospect of several vibration technologies for controlling metal solidification were also presented.
Abstract: The dynamic mechanical properties of austenitic stainless steel 06Cr19Ni10 were studied by a high temperature split-Hopkinson pressure bar (SHPB) at temperatures of 25–300 ℃ and strain rates of 1000–3000 s−1. The austenitic stainless steel 06Cr19Ni10 shows strain rate strengthening effect in the range of 1000–3 000 s−1, and temperature softening effect in the range of 25–300 ℃. A scanning electron microscope (SEM) was used to observe microstructure of deformed sample at strain rate of 3 000 s−1. It is found that under high strain rate, the deformation zone density is high, and decreases as the deformation temperature increases.
Abstract: 1725/WC composite coatings were prepared on the surface of cast iron by laser cladding. The effects of process parameters including laser power, scanning speed and powder feed rate on dilution ratio and hardness of the cladding coating were studied through orthogonal experiments. The results showed that the laser power had the greatest effect on the dilution rate of the cladding layer, followed by powder feeding rate and scanning speed, respectively. And the primary and secondary order sequence of these three factors on the surface microhardness were power feeding rate, laser power and scanning speed. The optimum process parameters were as follows: laser power was 2 000 W, scanning speed was 15 mm/s, powder feed rate was 10 g/min. The 1725/WC composite coating generated under the optimized process had good forming quality and WC had a uniform distribution. The average hardness of the cladding coating was 483.0HV0.2.
Abstract: In this work, the influence of Ti treatment on inclusions in steel and the formation conditions and evolution process of Ti oxide inclusions were studied by a combination of simulation calculation and experiment. The results show that at 1 600 ℃, when the content of [O] in steel is greater than 22×10−6, Ti oxide inclusions will be formed. At the same time, since the presence of [Als] in the steel will inhibit the formation of Ti-containing oxide inclusions, it is required to avoid the use of metallic Al for deoxidation treatment as much as possible during the smelting process. When the [O] content in the steel before Ti treatment is less than 80×10−6, with the increase of [O] content, the size of the inclusions changes slightly. The addition of Ca particles after the Ti treatment can modify the inclusions and promote the nucleation of MnS on the inclusions, which is beneficial to promote the formation of intragranular acicular ferrite.
Abstract: In order to investigate the effect of SO42− on the corrosion damage of 304 stainless steel in a solution containing 0.7 mol/L Cl−, acoustic emission technology and morphology observation technology were used to test the acoustic signal generated during the corrosion process and the surface morphology of the sample before and after corrosion, respectively. In the Cl−/SO42− solution, with the increase of SO42− concentration, the parameters such as relative energy and amplitude of AE signal generated during the corrosion process, the slope of cumulative number of impacts and duration time, as well as the number of corrosion pits and the number of cracked massive corrosion products firstly decrease and then increase. The degree of surface looseness caused by cracked corrosion products is firstly tight and then loose with the increase of SO42− concentration. The time period of sample corrosion damage is different due to the concentration of SO42− ions. The time periods for sample damage at 0, 0.10, 0.25, and 0.40 mol/L concentrations are the early and mid-term, early, late and full time periods of corrosion, respectively. The order of SO42− ion concentration influencing the degree of corrosion damage from heavy to light is 0 mol/L> 0.40 mol/L> 0.10 mol/L> 0.25 mol/L. In this study, after evaluating sample corrosion morphology and acoustic emission parameters, appropriate concentration of SO42− ions of 0.25 mol/L can effectively reduce the corrosion of 304 stainless steel in a 0.7 mol/L Cl− solution.
Abstract: The influence of rare earth modifier on nonmetallic inclusion morphology and size distribution of 1500 MPa grade hot stamping steel were investigated by optical microscope and scanning electron microscope. And the microstructure and plastic property of resulted steel at room temperature were compared. The results showed that macro segregation disappeared in the rare earth modifier treated steel. After rare earth modifier treatment, the size of D-type particle inclusion decreased obviously, however, the density of inclusion kept increasing. With the rare earth modifier treatment, the microstructure was refined apparently and the plastic property at room temperature was improved.
Abstract: In this paper, the microstructure, corrosion resistance and wear resistance of Fe-Si-Mn-C-Ti high-strength building steel with different titanium content were tested and analyzed. The results show that the addition of alloy element titanium is helpful to refine the internal structure and improve the corrosion resistance of the steel. With the increase of Ti content from 0 to 0.15%, the internal structure of the test steel is refined firstly and then coarsened, the corrosion potential firstly shifts to positive and then negative, the wear volume firstly decreases and then increase, the corrosion resistance and wear resistance increases firstly and then decreases. When 0.06% Ti is added, the corrosion potential of the steel is shifted forward by 91 mV, the wear volume decreases by 9×10−3 mm3, and the corrosion resistance is significantly improved. Fe-Si-Mn-C steel without titanium consists of matrix Fe and M3C carbides. When the content of Ti is 0.02%–0.06%, the steel consists of matrix Fe, TiC and M3C carbides. When the content of Ti is 0.15%, the steel consists of matrix Fe, TiC, TiN and M3C carbides.
Abstract: The work roll bending force of the last stand of the four stands 6-Hi HC tandem cold rolling mill is usually in saturation state when the brightwork roll is used in the last stand. This production phenomenon leads to the lack of the ability to control the strip shape, and then the shape defects are difficult to eliminate or further reduce. In the meantime, these restrict the continuous improvement of the shape quality of the cold-rolled strip. Therefore, the crown data of some hot-rolled coils were collected, and then its distribution was computed. Combined with the distribution characteristics of the work roll bending force of the first three stands, the relationship between the hot-rolled strip crown and the shape of the loaded roll gap and its impact on the work roll bending force was analyzed. Meanwhile, the influence of the online adjustment method to reduce the work roll bending force by using the negative displacement of intermediate roll on the surface quality of strip was also analyzed. On these bases, a control strategy of using a multi-section positive crown work roll was proposed to solve the saturation of the work roll bending force of the last stand. With the help of analyzing the influence of work roll profile parameters on the strip shape, the optimized parameters of sixth-order polynomial work roll were finally obtained through several online crown work roll rolling tests. In addition, the test results also showed that using five sections of positive crown work roll in the last stand can increase the adjustment ability of the work roll bending and reduce the negative displacement of the intermediate roll. This phenomenon can effectively solve the problem of the saturation of the work roll bending force of the last stand and improve the quality of the strip shape’s quality.
Abstract: The surface crack area of SAE1144 free cutting steel during cold drawing from 18 mm round bar to 15 mm octagonal bar was studied by means of optical microscope, sample electrolysis, SEM+EDS and ImageJ software. The results show that there exist large granular MnS inclusions, elongated strip cluster MnS inclusions and massive FeO inclusions in the crack propagation zone of octagonal bar, and lots of dense elongated strip MnS present on the crack surface. The large FeO inclusions are the source of microcracks, and the large granular MnS inclusions and elongated strip cluster MnS inclusions are the main causes of crack propagation.
Address：Editorial Department of Iron Vanadium Titanium Steel, Technology Development Research Center, Research Institute of Panzhihua Group Co., Ltd., No. 90 Taoyuan Street, East District, Panzhihua City, Sichuan Province (617000)