120t钢包底吹氩混匀过程的数值模拟研究

以某钢厂120 t单孔底吹氩钢包为研究对象,利用ANSYS-FLUENT软件对不同吹氩条件下钢包内钢液的流场进行数值模拟,并预测混匀时间。结果表明,吹孔位置位于1/2R处,氩气流量为100 L/min时,钢液的混匀时间最短,钢包内钢液的搅拌效果最好。     

钢液净化措施对高硅铸钢夹杂物的影响

本文在分析中频感应电炉熔炼的未经炉外精炼处理的高硅铸钢中的夹杂物的基础上，对高硅铸钢进行了底吹氩气精炼处理。结果表明，底吹氩气可以促进钢液中夹杂物的聚集长大，并促进夹杂物的上浮；随着氩气流量的增加，试样中夹杂物的含量逐渐减少，夹杂物的平均间距逐渐增加，得到了中频感应电炉熔炼高硅铸钢的有效钢液净化工艺。     

淬火温度对高硼铸钢显微组织和硬度的影响

研究淬火温度对含碳量小于0．4％和含硼量小于2．0％的高硼铸钢显微组织和硬度的影响。高硼铸钢铸态基体组织由珠光体和铁素体组成。淬火处理后，硼化物数量变化不明显，随着淬火温度升高，基体显微硬度和试样宏观硬度提高，淬火温度超过1000℃后，硬度略有降低。在900~1100℃内淬火，都可获得强韧性好的板条马氏体基体组织。高硼铸钢中的硼化物显微硬度超过1500HV，由F32B和少量FeB组成。     

SG45VCM钢LF+VD精炼吹氮合金化研究

1 873 K下,Mo Si2电阻炉上用70 mm×100 mm Mg O坩埚,以SG45VCM钢为研究对象,对不同压力下(33、66、100 k Pa)气相渗氮过程及脱氮过程中氮的溶解行为进行了研究。分别建立了相应的热力学及动力学模型,并在实验室进行了验证。实验发现,氮分压越大溶解度越大,吹氮25 min后钢液中氮达到饱和,吹氩脱气40 min后,钢中氮的质量分数在100×10-6以下。工业试验表明,60 t LF+VD精炼炉底吹氮气后钢中增氮效果稳定。在LF精炼底吹氩气压力1~1.5 MPa、流量300~400 Nl/min条件下吹氮20~30 min后切换成氩气,VD保真空5~10 min的冶炼工艺条件下,可不添加任何氮化合金,即可生产满足氮含量要求的产品。     

多元低合金贝氏体铸钢磨球的研究

针对常用磨球材质脆性大、耐磨性低、磨耗高的缺点，研制了多元低合金贝氏体铸钢磨球，它具有硬度高、硬度均匀性好和韧性高等特点，用于磨矿生产，磨耗接受高铬铸铁球，成本降低３０％～４０％，综合效益显著。     

淬火温度对高硼铸钢显微组织和硬度的影响

研究淬火温度对含碳量小于0.4%和含硼量小于2.0%的高硼铸钢显微组织和硬度的影响.高硼铸钢铸态基体组织由珠光体和铁素体组成.淬火处理后,硼化物数量变化不明显,随着淬火温度升高,基体显微硬度和试样宏观硬度提高,淬火温度超过1000℃后,硬度略有降低.在900～1100℃内淬火,都可获得强韧性好的板条马氏体基体组织.高硼铸钢中的硼化物显微硬度超过1500HV,由Fe2B和少量FeB组成.     

4J43膨胀合金底吹氩工艺的物理模拟及工业应用

钢包底吹氩工艺是一种经济实用且简单易行的精炼方法,通过实验室物理模拟确定出膨胀合金4J43在底吹氩工艺中氩气流量应控制在3~7 L/min之间。在该流量范围内,合金液的混匀时间随氩气流量的增加而减少。在合适的吹氩参数下进行工业生产,实验结果表明：吹氩工艺对4J43膨胀合金中氧元素及夹杂物的去除效果明显。当氩气流量为5 L/min时,与未吹氩相比合金中氧元素含量下降56.98%,非金属夹杂物总量减少46.43%,合金中大尺寸夹杂物数量明显减少,合金在室温下的各项力学性能与同组相比均得到很大提高。     

高碳硅锰铸钢中夹杂物的形成与控制

对高碳硅锰铸钢中夹杂物的主要类型进行了详细研究,发现高碳硅锰铸钢中除了常见的硫化物夹杂外,还存在含硅夹杂物、含铝夹杂物、含钙夹杂物和稀土夹杂物等。采用钢液高温出炉、吹氩处理以及吹氩后静置处理等工艺措施,可以明显减少高碳硅锰铸钢中的夹杂物,夹杂物含量可以控制在0.1%以下。高碳硅锰铸钢经吹氩去夹杂物处理后,韧性明显改善,尤其是冲击韧性提高21.2%,达到16.6J/cm2。     

含硼铸钢的研究和应用

介绍了硼元素的特点及其在钢中的作用,微量硼可以明显改善钢的淬透性和韧性。硼在铸钢中主要以硼化物形式偏聚于晶界,损害钢的韧性。采用淬火预处理,并适当提高奥氏体化温度,有利于消除硼脆,改善硼钢韧性。另外,提高铸钢硼含量,可以获得硬度高、热稳定性好的Fe2B化合物,有利于改善钢的耐磨性。     

高强度抗磨铸钢衬板的研究

在铸钢中加入硼元素,获得了高强度抗磨高硼铸钢.研究了淬火温度对高硼铸钢衬板显微组织和硬度的影响.结果显示,随着淬火温度提高,淬火组织硬度增加,淬火温度1000℃时,基体组织全部转变成了强韧性好的板条马氏体.高硼铸钢衬板经1000℃淬火后,再在230～240℃进行去应力回火处理,具有良好的强韧性和抗磨性,使用中衬板不会断裂,其使用寿命比高锰钢提高180%～200%,且不含贵重合金元素,生产工艺简便.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.