PCD、PCBN切削刀具的发展浅析

从常用切削刀具入手,重点介绍了PCD、PCBN切削刀具的特点、性能、应用及其国内外发展,最后对国产PCD、PCBN切削刀具提出了几点建议.     

超硬刀具现代切削加工中的重要手段

代表现代机械加工主流方向的高速切削加工,因顺应了21世纪机械加工高效率、高精度、柔性与绿色化的要求而迅速发展,这一技术主要应用于车削和铣削.高速干切削能消除切削液所带来的污染环境、危害工人健康的负面影响,是符合可持续发展要求的先进制造技术.精磨是轴承精加工中最常用的加工工艺,随着PCBN刀具的出现及数控机床等加工设备精度的提高,以硬态切削代替磨削来完成零件的最终加工已成为硬轴承钢的一个新的精加工途径.后继工序有超精加工或精度磨削要求时,硬态切削是最好的选择.要实现高速切削、干切削、硬态切削,精密和超精密切削,刀具材料是关键.而PCD、PCBN刀具为上述切削技术的实现提供了最基本的前提条件.     

cBN-TiN-Al合成PCBN复合片及其性能研究

将立方氮化硼微粉和TiN、Al微粉按一定的质量比进行混料,在高温和超高压条件下合成聚晶立方氮化硼(PCBN)复合片,对复合片进行了物相分析、硬度测试以及表面显微结构分析,同时分析了切削淬火钢时cBN含量对PCBN刀具磨损的影响,研究了PCBN刀具切削时的磨损机理。烧结后PCBN复合层中的物相由除了cBN、TiN添加相以外,还出现了新相AlN和TiB_2,说明添加粘接剂与cBN发生反应,并且Al已完全反应,说明复合层中的cBN颗粒通过反应生成新物相,并被粘接剂固结。当cBN含量为80 wt%时,复合片的维氏硬度达到了4512 HV。PCBN后刀面的磨损成一个规则倒三角形,刀具的失效主要是粘结磨损和氧化磨损共同作用的结果。     

微硼科技有限公司走进中国

微硼科技有限公司（Microbor Technology Ltd．）于2009年11月3日在上海工博会期间召开了“微硼科技有限公司走进中国”新闻发布会,宣布其上海代表处的成立,并展示了他们在PCBN领域的创新科技——世界上第一款采用纳米级PCBN材质制造的切削刀具。     

晶须含量对Al2O3＋SiCw陶瓷刀具切削加工时磨损和破损的影响

晶须含量不同将影响到Ａｌ＿２Ｏ＿３３＋ＳｉＣ＿ｗ陶瓷刀具材料的力学性能，由此将进一步影响到该刀具材料切削加工时的抗磨损和破损性能。本文试验了不同晶须含量的Ａｌ＿２Ｏ＿３＋ＳｉＣ＿ｗ陶瓷刀具在连续切削时的抗磨损性能和断续切削时的抗破损性能。结果表明，晶须含量对该刀具材料的磨损和破损有很大的影响。因此在实际应用中应根据刀具损坏方式的不同分别选用不同晶须含量的Ａｌ＿２Ｏ＿３＋ＳｉＣ＿ｗ刀具材料，以充分发挥该刀具材料的增韧补强效果。     

SiC_p/Al复合材料的切削加工性能研究

通过PCD、PVD、CBN和YG6X四种不同材质的刀具对高体积分数的Si Cp/Al复合材料进行切削加工,分别从表面形貌、表面粗糙度以及表面残余应力三方面来综合表征复合材料加工后的表面质量,得出PCD刀具是切削加工高体积分数Si Cp/Al复合材料的最佳刀具。     

玻璃钢车削用刀具磨损研究

玻璃钢车削用车刀磨损的主要原因之一为切削热磨损，本文主要分析介绍了用车刀切削玻璃钢材料刀具磨损的主要原因，并介绍为解决刀具磨损几种常用的车刀刃磨方式。     

TiN/WC/Al合成PCBN复合材料及其性能研究

以TiN/WC/Al为主要实验原料,在高温和超高压条件下合成聚晶立方氮化硼(PCBN)复合片。利用X射线衍射(XRD)、扫描电子显微镜(SEM)对复合片的物相组成、显微结构进行了分析,同时对复合材料的气孔率、显微硬度、抗弯强度以及切削性能进行了测试。研究表明:在超高压5.5 GPa时,烧结温度越高PCBN复合片的性能越优。在相同的烧结温度下,当WC加入量为6 wt%时,PCBN复合片的综合性能最优,其中气孔率为0.87%,显微硬度为31.8 GPa,抗弯强度为830.3 MPa。在切削里程为4 km时,添加WC加入量为6 wt%的PCBN刀具的后刀面磨损量仅为310μm,被加工工件的表面粗糙度最小,仅为1.2μm。     

涂层高速钢刀具特点和合理使用

现代切削刀具中的拉刀、齿轮刀具、丝锥、钻头、铣刀等,多数仍用高速钢制作。而在现代工业产品中,采用强度高、韧性好的结构材料愈来愈多。由于这些材料的高硬度、加工硬化现象严重、导热性差等不同原因,使现在使用的高速钢刀具很难对这些材料进行切削加工。为此,世界各国刀具工作者对强化高速钢刀具表面的工艺方法进行了多种探讨,近几年来,涂层高速钢刀具的迅速推广应用,被认为是当今的一次刀具革命。涂层高速钢刀具是指用化学气相沉积法(CVD)或物理气相沉积法(PVD)在刀刃各表面土涂铍一层很薄的TiC 或TiN 膜层的高速钢刀具。     

梯度功能陶瓷刀具材料的残余应力设计及制备

根据陶瓷刀具切割时刀楔内的应力分布规律及刀具损坏机理的分析,首次提出以陶瓷刀具材料的组成分布进行设计以及梯度的模型,通过对不同组成分布的刀具材料制备过程中的残余应力及刀具切削过程中的热应力,机械应力进行模拟,以残余应力与外加应力部分抵消为目标优化设计了梯度组成分布,按设计结果,采用粉末铺填－热压烧结工艺研制成功Ａｌ２Ｏ３／ＴｉＣ系梯度功能陶瓷刀具材料。     

氢气纯度分析方法准确性的探讨

ONACCURACYOFANALYSISOFOFHYDROGEN1前言我公司目前应用的氢气纯度分析方法有两种,一种是爆炸反应法,另一种是焦性没食子酸吸收法。几年来,人们对两种分析方法的准确性曾有过褒贬不一的评论。这里我们也谈谈自己粗浅的观点。2爆炸法测定氢气纯度一定量的氢气样品与适量的空气之均匀混合物因反应后生成液体水而引起气体体积减少,减少的体积等于参加反应气体体积之和。其中l／3为氧气,2／3为氢气。根据氢气取样量和反应前后混气体体积之差,以及氢气在反应中的体积比例关系,可计算出样品的氢气纯度。计算公式式中：A一混…     

COMPARISON OF METHODS OF ANALYSIS OF GYPSUM1

The different analytical methods proposed for the evaluation of gypsum have been subjected to an experimental test. A combination method, consisting of a fusion with KHCO₃ and determination of CaO by KMnO₄ titration, the SO₃ by Andrews method of titration of BaCrO₄ has been found to give very reliable results with the least consumption of time.     

SEDIMENTATION OF BINARY MIXTURES OF PARTICLES OF UNEQUAL DENSITIES AND OF DIFFERENT SIZES

A model is developed for the sedimentation from a suspension of two particle species of unequal densities and of different sizes. The composition and the thickness of various layers in the sediments are predicted using graphical and analytical methods. The model predictions were in excellent agreement with experimental results, when the particle size ratio was ≥ 108. When size ratio of the particles was 2.60 and 4.31 the agreement occurred in about 50 percent of the cases.     

HEASUREHENT OF INSTANTANEOUS RATES OF LOSS OF VOIATILE COMPOUNDS DURING DRYING OF DROPS

A novel technique serves to monitor instantaneous rates of loss of a volatile solute from a suspended drop during drying. A highly sensitive electron capture detector is used to monitor concentrations of SF6 released into a flowing gas stream from a suspended, drying drop. Simultaneously, the appearance and morphological development of the drop are monitored with a video camera. This provides the wherewithal of relating instantaneous rates of loss of the volatile solute to particular events during the development of particle morphology.

Initial experiments have been carried out with drops of aqueous solutions of glucose, sucrose, maltodextrin and coffee extract. The results clearly display the onset of the volatiles-retentive selective diffusion phenomenon. There is also substantial loss of the volatile component later in the drying process, when the drops undergo repeated ex ansion, bursting and cratering due to the formation of internaf bubbles. These experiments appear to be the first quantitative demonstration of major losses accompanying changes in drop morphology.     

茶多酚提取方法进展

本文综述了国内外现有茶多酚提取方法的现状以及近期的研究进展，并对其优缺点进行了评价。这将有助于中低档茶的综合利用和茶多酚的进一步开发应用。     

ANALYSIS OF RECENT MEASUREMENTS OF THE VISCOSITY OF GLASSES

Viscosity of Simple Soda-Silicate 500° to 1400°C Comparison of the results given by English with those of Washburn, Shelton and Libman, indicates a discrepancy in the absolute values of log₁₀ viscosity amounting to 0.6, those of Washburn et al., being relatively too high. If correction for this is made, the isothermal curves of log₁₀ viscosity as a function of soda content are smooth up to 50% Na₂O, showing no inflection. The observations as a function of temperature T are all represented within accidental error by an equation of the type where all three constants vary regularly with the composition. Change of Viscosity of Glass (6SiO₂, 2Na₂O) due to Molecular Substitution of CaO, MgO and Al₂O₃ for Na₂O The effect is clearly brought out by plotting (from the results of English) the change of log₁₀η due to the substitution as a function of temperature. The curves each show a sharp bend at a temperature between 840° and 1050°C, which is designated the aggregation temperature T_a. If we divide these curves by the corresponding percentage substituted, we get curves for each oxide which are straight and parallel below the aggregation temperatures, the slopes (increase of change of log₁₀η per 100°C) being −0.056 (CaO), −0.055 (MgO), −0.018 (A1₂O₃) per per cent oxide substituted. For substitution of 1/2 molecule the slopes are −0.325 (CaO), −0.23 (MgO) and −0.18 (Al₂O₃) per 100°. At the aggregation temperature the change of log₁₀η per per cent is a minimum, 0.03 to 0.06 for CaO, 0.12 for MgO, 0.07 for Al₂O₃. Evidence of Aggregation in Glasses, from viscosity Measurements The sharp bends in the plots of change of log₁₀η due to substitution of an oxide for Na₂O, suggest the beginning of molecular aggregation at these temperatures. These aggregation temperatures are close to the devitrification temperatures, but the effect on the viscosity curves cannot be due to actual devitrification since it does not change with time. Taking the aggregation temperatures as equal to devitrification temperatures, additional isotherms are roughly sketched into the equilibrium triangle of the system Na₂O-CaO-SiO₂. Change of Viscosity of Glass (4SiO₂, 2Na₂O) due to of Substitution of B₂O₃ for SiO₂ The change of log₁₀η (from the results of English) is plotted as a function of temperature, and also the change of log₁₀η per per cent B₂O₃. The curves are more complex than for the substitution for Na₂O.     

环氧树脂羟基值测定方法的研究

利用乙酸酐、吡啶和浓硫酸混合的乙酰化试剂测定环氧树脂中羟基值含量的方法具有操作简便、滴定终点明显和分析结果误差小等优点。     

骑式摩托车油箱喷涂工艺的改进

面对日益激烈的市场竞争,摩托车油箱外观质量越来越成为影响销售的因素之一。文章介绍了改进工艺后的油箱涂装,该涂装体系提高了油箱外观的丰满度,降低了油箱涂装的生产成本。     

几种针状焦性能对比

针状焦分石油系和煤系两大类,这主要取决于针状焦的原料来源。在同一系列中由于原料不同和工艺条件不同 ,针状焦的各自性能也不相同。针状焦是生产超高功率石墨电极和高功率石墨电极的主要原料 ,针状焦的性能对石墨电极的质量有至关重要的影响。所以对针状焦性能以及其对石墨电极质量影响的研究十分必要的。以下是常用的几种进口针状焦和国产针状焦的性能对比。１原料性能分析对比原料试样包括４种针状焦 ,其中两种为进口针状焦：三菱针状焦和新日化针状焦;另两种为国产针状焦：鞍山针状焦和锦州针状焦。其中除锦州针状焦是石油系针状焦外…     

聚酰亚胺的合成法

本文评述了缩聚型聚酰亚胺的主要合成方法和近年来国际上在合成中所做的探索。