车刀前刀面影响刃磨强度的研究

由于断屑槽的存在,车刀前刀面的形状各不相同.对相同前角下不同形状的前刀面的刃磨强度进行分析,结果表明曲面形前刀面的刃磨强度比平面形前刀面的高.另外由于断屑槽分布在车刀的前刀面上,因此在刃磨时除了保证前角,还应保证断屑槽刃磨后的光洁度和尺寸.针对此问题,提出在磨削断屑槽时,将砂轮倾斜一个很小的角度的方法,可以保证断屑槽刃磨的尺寸和精度.     

硬质合金可转位车刀片UG型断屑槽断屑机理的研究

本文采用接触图形法对硬质合金可转位车刀片UG型断屑槽的断屑机理进行了实验研究．结果表明：由于采用了根据不同切削深度和进给量巧妙改变有效槽宽、使切屑横截面弯曲呈拱形、弹形挡屑筹措施，UG型断屑槽具有断屑范围较宽、在进给量较大时不易出现过分断屑等特点．此外，文中还对化学气相涂层刀片的UG型断屑槽在切削速度明显提高以后断屑范围的变化进行了研究．文中给出的UG型断屑槽的断屑范围图可供实际选用．     

加工钢件自动断屑法

在组合机床或组合机床自动线加工钢件过程中,断屑是个普遍感到头痛的问题,特别是钻、扩大孔(φ20毫米以上),更感困难。我厂在为某汽车厂提供的加工叉子耳孔自动线上的钻、扩、镗粗加工工位的断屑装置,是采用小减速箱带动断屑凸轮来控制液压系统实现的。减速箱(参看图1)将微型电动机的高速转数经过一对交换齿轮和蜗杆蜗轮进行减速,以达到所要求的转速,因为自动线上的钻、扩、镗等工位的主轴转数不同,断屑凸轮的转速也应相应改变,以期达到较理想的断屑效果。各工位切削用量与相应的断屑凸轮参数如表1所列。     

内冷与喷雾复合冷却车刀的冷却性能数值模拟

针对难加工材料的高效、绿色可持续的加工需求,文章提出了一种外部的喷雾润滑冷却结合刀具内部循环冷却的冷却加工技术方案,并设计出一种冷却效果好、加工无污染的内冷与喷雾复合冷却车刀。建立了普通车刀、循环内冷车刀和内冷与喷雾复合冷却车刀及其切削工件的结构三维模型,并通过FLUENT软件对车刀加工冷却过程进行流-固热耦合仿真,探究内冷与喷雾复合冷却车刀的冷却性能。研究表明,三种车刀的温度从低到高依次为内冷与喷雾复合冷却车刀、循环内冷车刀、普通车刀,复合冷却车刀具有更好的冷却性能。并进一步研究了喷雾空气压力参数对冷却效果的影响规律,发现喷雾空气压力越大,冷却效果越好,但冷却效率与喷雾空气压力之间并不成线性关系。     

可变切深、断屑式深孔加工

研究了深孔加工切屑形成机理及各种断、排屑方式。结果表明,程序控制、变切深进给的断排屑式深孔加工效果明显,加工精度也显著提高。     

切削加工强制断屑方法的研究与应用

通过列举机械加工行业目前常用的几种切削加工断屑工艺,并结合典型实例进行分析,找出各工艺方案存在的缺点与不足.对于那些韧性好、难断屑的材料在进行低速切削加工时,断屑则成为一个十分棘手而又难以解决的问题.如何通过改进断屑方法来提高工件加工的表面质量和刀具的使用寿命,这是文章所要讨论和解决的问题.     

论刀具磨损量与断屑槽断屑的关系

本文通过实验研究和理论分析,讨论了前、后刀面磨损量对断屑槽断屑效果的影响及断屑槽槽形与磨损量的关系,还讨论了改变槽形以减少磨损量、提高刀具寿命并达到最佳断屑效果的断屑槽的设计原则。图4幅。     

液压振动断屑装置在自动线上的应用

针对机床切削加工自动线中，如何将切屑折断成一段段较短的断屑的问题，采用了液压振动断屑装置。本文对液压系统带动凸轮振动断屑的工作原理进行了论述。     

深孔钻断排屑机理与变切深加工数控宏程序研究

深孔加工面临许多困难,其中最主要的困难是断排屑、钻偏及折断钻头.文章针对深孔加工的特殊性,研究了切屑形成机理及各种断、排屑方式,采用“变切深、引钻”等方法并通过数控宏程序控制深孔加工,解决了断排屑、钻偏及折断钻头等难题,应用结果表明,深孔加工的断排屑效果明显,加工效率及精度显著提高.     

PCD金刚石刀具车削2A12硬铝合金工艺参数的优化

采用特定品牌PCD车刀在英格索尔50T线性高精度导轨FANUC数控车床上,对2A12硬铝合金进行外圆轮廓车加工试验,观察硬铝合金在特定工艺参数下切屑形态及加工质量的变化。利用高端的数字化检测设备及软件,对加工成型的硬铝合金表面进行轮廓度及圆柱度测量。分析特定品牌PCD车刀在不同加工工艺参数下2A12硬铝合金的加工质量,得出最佳的切削进给速度Vf=0.12mm·r-1、切削深度为ap=1.2mm。结果表明,合理选择加工切削的刀具材料、加工工艺参数,可使2A12硬铝合金切屑成完美的弹性卷屑状,工件表面轮廓与理论轮廓贴近,圆柱精度较高,实现加工2A12硬铝的高效高质量切削。     

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.     

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.     

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.