碳对中铬合金白口铸铁热塑性影响规律研究

采用锻造方法可大幅度提高铬合金白口铸铁的冲击韧性,文章针对高铬合金白口铸铁成本高、锻造性能差以及低铬合金白口铸铁铸造性能差、耐磨性差的问题,选择含铬9%左右的中铬合金白口铸铁,采用热塑性镦粗试验方法,对不同碳含量中铬合金白口铸铁的热塑性、碳对中铬白口铸铁热塑性的影响规律进行了研究.结果表明,含碳量为1.85%～2.59%的中铬合金白口铸铁在850℃～1130℃的温度范围内,具有良好的塑性变形能力,且随碳含量的增加,中铬白口铸铁的热塑性下降,其主要原因是碳含量不同所引起的组织中共晶碳化物的数量的改变所致.     

铬、钼对锰硼白口铸铁组织及性能的影响

通过试验研究了铬、钼合金元素对锰硼白口铸铁组织及性能的影响。试验结果表明：在锰硼白口铸铁中加入适量的铬和钼，不仅可以提高其淬透性和硬度，而且能改善其冲击韧度，同时也使其耐磨性比普通锰硼白口铸铁提高50%。     

高碳型和中碳型高铬白口铸铁的研究

抛丸机叶片、反击式破碎机锥条和球磨机衬板等易损零件,品种多,需要量大,如用材得当,就可以收到很大的经济效益。我们经过材料试验、现场考核和现场对比试验,用高碳高铬白口铸铁研制了抛丸机叶片,用中碳高铬白口铸铁研制了反击式破碎机锤条,均取得了显著的效果。一、高碳型和中碳型高铬白口铸铁的成分设计高碳高铬和中碳高铬白口铸铁都是以铬钼为主要合金元素,两者都具有良好的抗磨性能。我们以含铬15％左右的高铬白口铸铁的主要成分为基础,     

用电子探针确定铸铁气缸套中碳化物的组成元素

一、前言目前,国内外生产气缸套、活塞环配对摩擦付,多采用往铸铁中添加磷、硼、钒、钛、铌、钨、铬等微量元素的方法,来提高铸铁组织中硬质相的显微硬度和强化基体组织。例如硼钨铬多元合金的气缸套,其耐磨性均优于其它材质。其原因主要是铸铁中含有硼、钨、铬、锰、铌、钽、钒、钛等多种合金元素。那么,这些合金元素在碳化物中分布情况究竟如何?为此,本文用X光能谱和扫描电镜对3种不同化学成分的铸铁气缸套中钨、钒、钛、铌、钽、磷等元素的分布情况以及合金碳化物的组成元素进行了初步分析。二、试验方法试样取自硼钨铬多元合金铸铁、钒钛铸铁和铌铸铁的气缸套上,其常规化学成分见表1。供电子探针分析用10×10×5毫米试样,     

低合金白口铸铁复合变质的研究

文中介绍的是一种主要用B、V、Ti及碱金属,稀土金属进行复合变质处理的方法.试验表明,该法可使低合金白口铸铁的碳化物形态明显改善,使a_k值提高为未变质处理的2倍以上.经合适变质的低铬白口铸铁的a_k值在铸态下可达10J/cm~2,经热处理可达12J/cm~2.     

铬白口铸铁—钢复合结构的组织与性能

采用铸造方法，将不同直径的４５钢钢筋包覆在铬白口铸铁（低铬和中铬）芯部，研究了所得复合试样的组织与性能，结果表明，选用较大直径比（钢筋直径／试样直径）并经适当热处理，可获得较理想的综合性能，外层铬白口铸铁的硬度可达ＨＲＣ６１．５￣６４．５，复合试样的抗弯强度可达σＷ＝７００￣１０００ＭＰａ，比单－铬白口铸铁提高４０￣４５％。     

铬白口铸铁－钢复合结构的组织与性能

采用铸造方法，将不同直径的４５钢钢筋包覆在铬白口铸铁《低络和中铬》芯部，研究了所得复合试样的组织与性能。结果表明，选用较大直径比《钢筋直径／试样直径）并经适当热处理，可获得较理想的综合性能。外层铬白口铸铁的硬度可达ＨＲＣ６１．５～６４．５，复合试样的抗弯强度可达。δｗ＝７００～１０００ＭＰａ，比单－铬白口铸铁提高４０～４５％。     

Si对低铬白口铸铁在含Cu2+离子介质中腐蚀磨损特性的影响

采用三体腐蚀磨损试验方法研究了硅对低铬白口铸铁在含铜离子浆料介质中的腐蚀磨损耐磨性的影响。结果表明，当浆料介质中铜离子浓度增加时，低铬白口铸铁的腐蚀磨损耐磨性降低。而增加含硅量后的低铬白口铸铁的腐蚀磨损耐磨性将比普通白口铸铁的高。磨损表面形貌分析表明，普通低铬白口铸铁的磨损机制为磨料磨损和介质腐蚀，而硅量增加的低铬白口铸铁的磨损机制则以磨料磨损为主，伴随着腐蚀作用。     

含钒高铬铸铁的研究

含钒高铬铸铁铸态或经亚临界热处理其硬度可达到经常规热处理达到的水平。铸态冷却条件下厚薄断面上的硬度分布基本趋于一致。残余奥氏体量比一般铬一钼系白口铸铁低得多。经亚临界热处理后其耐磨性优于铬一钼系白口铸铁。     

钒钛对稀土低铬耐磨铸铁性能的影响

研究了钒、钛对稀土低铬耐磨铸铁的机械性能及耐磨性的影响。结果表明,钒、钛使稀土低铬耐磨铸铁硬度略有增加,冲击韧性提高70%,相对耐磨性提高105%,生产验证表明,含有钒、钛的稀土低铬多元合金耐磨铸铁抛丸叶片比普通耐磨铸铁抛丸叶片使用寿命提高1~2倍。     

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.