标准砂在磨料粒度组成检测中的作用分析

磨料粗磨粒粒度组成检测的基本方法为筛分法。本文通过对磨料粒度组成检测时筛分条件对筛分结果的影响进行分析，得出标准砂在粒度组成检测中的两个作用：一是用来选择高精度的试验筛，二是对筛分结果进行校正，达到准确检测粒度组成，统一检测结果的目的。同时论述了标准砂的校正原理，并以实例对标准砂的作用进行了论证。     

用计算法换算磨料粒度组成验收标准的设想

用标准砂校对换算磨料的粒度组成,方法虽然简单,但存在一定缺点。其一是标准砂的生产比较困难,有时需配制才能实现。其二是检查筛筛网的尺寸偏差对粒度组成的影响较大,甚至破坏粒群的连续性,在生产上会造成有些粒度号好干(易于生产),有些粒度号难干(不易生产)的现象。其三是校对的计算比较麻烦,在磨料新国标中对粒度组成的校正要用正     

磨料粘度“校正砂”使用知识问答

1、什么叫磨料粒度“校正砂”? 磨料粒度“校正砂”又称“标准砂”或“标准试料”,它是以选定的原材料按照磨料标准规定的要求制造,用以校正磨料检查筛统一磨料粒度不可缺少的标准试样。目前世界主要先进工业国家都有自己的磨料粒度“校正砂”。2、为什么磨料新国标(GB2481—83)规定磨料粒度检查筛必须用“校正砂”校正后     

在磨料粘度生产过程中对质量控制的一种方法

粒度检验是控制磨料粒度质量的最重要的工作之一;但单靠粒度检验还不能说是对产品质量的一种积极的控制办法,因为它只是所谓的“事后检查”;积极控制磨料粘度质量的办法应该是推行全面质量管理,通过对磨料粒度的检验利用概率与统计的方法找出既能保证产品质量而又比较合理的最佳磨料筛分生产工艺。再通过生产过程中的抽样检查,根据测定结     

固结磨具用磨料粒度组成及其检测方法新标准介绍

１前言磨料粒度组成是磨料的重要质量技术指标，普通磨料按用途分固结磨具用和涂附磨具用两大类。固结磨具用磨料粒度组成及其检测方法新国家标准已于１９９８年１１月１８日发布，并于１９９９年９月１日起实施。新标准代替原ＧＢ２４７７—８３《磨料粒度及其组成》和Ｇ...     

磨料粒度组成标准样的制备和行业检查筛校正

由于检查筛网达不到磨料粒度分级精度的要求,长期来全国磨料粒度组成不统一,有的粗细相差竟到一至两个号,直接影响磨具质量的稳定和磨削效果。本工作通过选定检查磨粒磨粉粒度用的筛机和一套行业公认的标准筛,制定了检查方法,并利用了这套标准筛作了大量     

磨料微粉粒度组成检测数据的计算机处理

本文介绍了一种计算机处理磨料微粉粒度组成检测数据的方法和软件,操作人员只要输入检测得到的原始数据,该软件就能在普通的家用或办公室用计算机上准确,快速地完成数据处理,并自动打印出精美的符合GB／T 2481．2－1998年GB／T 9258．3－2000要求的测定记录表,粒度组成图和结果报告,该软件与磨料微粉粒度组成检测仪和检测方法配套,把我国的磨料微粉粒度组成的检测水平提高到国际先进水平。     

超硬磨料粒度组成标准问题讨论

针对合格的超硬磨料出现的划伤现象,用图像分析仪分析发现有大颗粒磨料存在。根据正态分布模型计算及实测表明:现行超硬磨料粒度组成标准中,16/18~200/230各粒度号用于限制大颗粒的上限筛筛孔尺寸过大,起不到限制大颗粒的作用,是不合理的。研究结果表明:采用比GB/T 6406-1996标准中规定的上限筛筛孔尺寸小一档的筛网作为上限筛较为合理,可以较好地控制大颗粒,起到质量把关的作用。     

固结磨具用磨料微粉先进标准

本文详尽阐述了固结磨具用磨料微粉的最新国际标准和欧美日现行标准，读者将从中对这先先进标准的微粉粒度组成和检测方法有更深入的理解。     

中国GB/T2477-1983标准W系列磨料微粉Ds50近似值的理论推导方法

中国国家标准GB/12481.2-1998"固结磨具用磨料粒度组成的检测与标记"采用Ds50值表示磨料微粉的颗粒直径,这与过去老标准的标识方法有很大不同.为了方便生产、技术、商务等人员对新标准的理解和使用,本文对普通磨料微粉的粒度分布曲线之数学特征进行了分析,建立了原国家标准GB/T2477-1983磨料微粉Ds50近似值的理论计算公式--在磨料颗粒分布之中间区域,颗粒的累积体积与其直径成反比例函数关系,对几家磨料生产企业的磨料微粉进行了实测,与计算数值相比最大误差±1.1μn,结果相符性较好;同时提出了沉降管测定后,不作曲线近似计算Ds50值的公式,实验结果表明此方法方便可行.     

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.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。