低碳球铁的系列化及其应用研究

对低碳球铁中不同种类Sx变质剂的制作工艺和组成进行了研究,对低碳球铁的系列化进行了探讨.研究表明,通过准铸态贝氏体工艺,并利用Sx-2型变质剂对Si-Mn-Cr-Cu低合金化的低碳铁液进行处理,可使低碳球铁稳定获得以针状无碳贝氏体为主,并有一定比例(25%～28%)奥氏体的准铸态贝氏体低碳球铁;含碳≤ 2%的Ni-Si-Cr35 5 2低碳铁液,经Sx-3型变质剂的变质处理,可获得球化良好的奥氏体耐热耐蚀低碳球铁;含2.0%C,2.8%Si的低碳铁液经过Sx-4型变质剂变质处理后,能够在铸态下获得石墨球圆整、金属基体中铁素体比例达85%以上,δ≥10%的高韧塑性铁素体低碳球墨铸铁.     

超低碳等温淬火球墨铸铁变质剂的研究

根据相关文献对变质剂中组成元素进行分类,分析了有关元素在铁液中的作用及行为,设计出四种不同成分的变质剂,对超低碳等温淬火球墨铸铁(AD)I进行变质处理。试验结果表明,SC变质剂变质效果最好,能够在铸态得到圆整度好、数量少、分布均匀的细小石墨球,并且基体组织中不存在碳化物。对SC变质剂加入量进行优化,探索不同变质剂含量对超低碳ADI的石墨球数、石墨球大小以及基体组织的影响。但是,SC变质剂加入量的改变,对石墨球数和石墨球大小的影响并不明显。     

低碳球铁研究的现状与展望

低碳球铁是含碳量远低于常规含碳量的球墨铸铁,现在已经发展了四个品种：1）铸态高韧塑性铁素体低碳球铁,2）铸态高强度珠光体低碳球铁,3）准铸态贝氏体低碳耐磨球铁,4）铸态耐热、耐蚀奥氏体低碳球铁.低碳球铁采用传统球铁生产中被认为有＂反球化＂作用的元素作为球化剂,为球化机理的研究提供新的依据.球化元素与＂反球化＂元素均为表面活性元素,没有本质的区别.低碳球铁的优点是成本低、性价比高.     

高冲击韧性QT900-6材料的开发与应用

通过优化球墨铸铁材料微量元素配比,采用SiC基变质剂进行铁液预处理和分段保温热处理的方式,研发出高冲击韧性的QT900-6新型球墨铸铁材料.该材料组织中石墨球数量明显增加,铁素体呈分散的破碎状分布,Si在铁素体中的固溶量减少,珠光体团和片间距明显变小,综合作用提高了材料的韧性.材料抗拉强度达到956 MPa,伸长率达到...     

SP1孕育剂及铸态珠光体球铁的实验研究

考察研究了铜、锰、锑、稀土、铝、钙、硅等元素在铸态珠光体球铁中的作用,经筛选后配制出一种强珠光体化复合孕育剂(SPI)。这种孕育剂兼有促进石墨球化、增加石墨球数等多种功能,在生产条件下,以液流孕育方式加入少量(0．08~0．12%)SPI,可使EQ140铸态球铁曲轴本体珠光体量大于75%,机械性能达QT70—2以上。     

热等静压工艺生产高强韧球墨铸铁件

介绍了热等静压生产工艺及作用,详细阐述了高压泵泵体铸件的生产工艺:采用水平分型无箱造型线造型;中频炉熔炼,严格控制铁液化学成分;采用Fe Si Mg8RE5球化剂,BS-1型Si-Ba孕育剂;盖包冲入法进行球化处理;铸件浇注后进行热等静压工艺处理。生产结果显示,铸件的金相组织为44.97%铁素体+42.28%珠光体+12.55%球状石墨,铁素体、珠光体与球状石墨组织分布均匀,石墨球更趋圆整;铸件的强韧性、硬度以及抗疲劳强度有了较大的提升,符合技术要求。     

正火处理对破碎铁素体球墨铸铁组织和性能的影响

为了提高球墨铸铁曲轴的强度和韧性,对铸态球铁进行不完全奥氏体化正火处理,在球铁基体内获得了珠光体及分散状的破碎铁索体组织.分析正火保温温度及保温时间对球墨铸铁组织和性能的影响,发现在奥氏体、铁素体和石墨的三相共存区内,随着保温温度的升高、保温时间的延长,正火后球铁基体中珠光体含量增加、铁素体含量下降,试样的强度、硬度呈上升趋势,韧性塑性有一定的下降.在860～870℃下保温1.5 h的曲轴,具有最佳的综合力学性能.     

镍和硅复合添加对低温高韧性球墨铸铁组织和性能的影响

采用1.2%～1.8%的镍对低温球墨铸铁进行合金化,同时加入2.0%～2.5%Si,并采用石墨化两阶段退火或低温石墨化退火工艺进行热处理。结果表明,热处理后材料的微观组织由铁素体、球状石墨和极少珠光体组成。当Si量为2.01%,Ni量为1.2%时,-20℃和-40℃的低温冲击功AKV都最高,分别达到16.3 J和13.6 J,同时抗拉强度大于400 MPa,伸长率高达23%。因此,要获得低温高韧性球墨铸铁,即保证不降低材料低温冲击功的前提下,提高其抗拉强度,应该选择合理的镍、硅含量,其中Ni量不超过1.5%,Si量在1.9%和2.3%之间。     

w（Si）、w（C）量及冷却速度对铸态球铁组织的影响

用热分析法研究了w（Si）、w（C）量和冷却速度对球铁中石墨和基体组织的影响。结果表明：适量增加孕育剂加入量能缩短球铁凝固过程中共晶平台的宽度,有限减少或避免石墨的畸变;在孕育剂加入量为1.38%时,能够得到66.8%的铁素体含量且球化效果良好的球墨铸铁;在w（C）量为3.94%、w（Si）量为2.23%时,由于CE达4.9%,导致与石墨漂浮相关的开花状石墨和枝晶石墨产生。     

风电轮毂用低温球墨铸铁的疲劳性能研究

通过控制铁水成分配比并采用脱氧工序,试制了一种可用于风电机轮毂的非标低温球墨铸铁。研究了基体组织和石墨形态对该球铁疲劳强度和断裂韧度的影响。结果表明,该球铁的这两种性能均达到了QT400-18球铁的水平;该球铁能达到符合要求的疲劳性能的显微组织为:珠光体含量<5%的铁素体基体,Ⅵ型球状石墨+Ⅴ型团絮状石墨,石墨尺寸≥6级,石墨球化级别≤3级。     

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).     

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.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

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.