剪毛机刀片的金相组织设计和N.M处理工艺

对剪毛机刀片失效方式和磨损机理的研究表明，刀片的刃口与刃面有不同的磨机理和性以要求。根据钢中碳化物在刀刃磨损过程中的作用，提出刀片的组织设计，认为刃面上有数量足够，粗细适度和均匀分布的碳化物，可有效地抵御石英之类高硬度磨粒的划伤。但碳化物在刃口则有害，它会造成崩刃并加剧由剥层理论所描述的磨损过程。本文提出了含氮马氏体化处理（Ｎ．Ｍ处理）新工艺，它可使工具钢表层碳化物完全消失，得到刃口无碳化物而...     

低合金刃具钢的姜块状索氏体化处理

介绍了一种工具钢在稍低于Ａｃｌ温度下不太长时间加热,使片状索氏体不完全球化,形成姜块状碳化物的工艺。用于剪毛机刀片代替球化退火作毛坯预处理,淬火后刀片寿命大幅度提高。本文从空间形貌上说明姜块状碳化物的形成机制,并从微观机理分析姜块状碳化物提高刀片耐磨性的原因。研究表明,细粒碳化物可使刃口强化,但不能阻挡已压入刃面砂粒的划伤;而粗粒碳化物弥散强化效果差,却能阻挡砂粒的划伤,但对刃口则会加剧崩刃。姜块状碳化物兼有粗粒和细粒碳化物的优点,兼顾刃口和刃面的不同性能要求,因而是刀片的理想组织。     

剪毛机刀片的硬度设计与热处理工艺

在查明剪毛机刀片刃口和刃面不同的失效方式和磨损机理的基础上,运用摩擦学理论,借鉴前人的研究成果。提出承受以石英为代表的磨粒犁削、冲击磨料磨损、接触疲劳磨损和抑制粘着磨损的刃口和刃面应具备的硬度。经淬火、回火、硬度约62HRC的低合全工具钢刀片具有较高的耐磨性,但刀片硬度还应根据羊种和含砂情况作1～2HRC的调整。介绍了经获得最佳含碳量马氏体、G．S．预处理和N．M．处理三种工艺处理的刀片的使用效果。经N,M．处理的刀片不但刃口、刃面组织结构极佳。而且刃口、刃面的硬度分布合理,因而寿命大幅度提高。     

铝挤压机主剪剪刃设计

应用Forge软件和CrockroftLatham断裂准则对主剪剪切压余过程进行模拟,确定主剪剪刃的刃口部分一直与压余接触,主剪受力与剪刃刃口受力区域和受力大小直接相关。而后对剪刃刃口进行受力分析,确定剪刃受力大小主要取决于剪刃刃口克服材料变形抗力的大小,以及刃口宽度、高度和刃口与水平坐标轴的夹角。并结合剪刃刃口受力最危险工况对主剪结构进行有限元分析,结果表明,当剪刃的长刃口与水平坐标轴夹角较大时,主剪崩刃风险加大。建议按最危险工况确定长刃口与水平坐标轴的夹角取值,使主剪剪刃既满足强度和刚度的设计要求,又具有足够的安全裕度。     

斜刃冲裁的最优刃口与冲裁力

分析了斜刃冲裁的冲裁力。该力不仅与板料和斜刃高度有关,还与刃口形状有关,据此提出了刃口形状的最优设计问题。获得了最优刃口的一般微分方程及对应的圆弧与直线轮廓冲裁件最优刃口的解析解,也给出了一般冲裁件最优刃口的求解方法。对给定斜刃高度与零件采用最优刃口可使冲裁力及断裂噪声降至最低。     

热处理对滚丝轮碳化物形态及寿命的影响

利用光学显微镜分析和研究了固溶双细化处理前后碳化物形态及分布和热处理对滚丝轮寿命的影响。结果表明:在高碳高合金冷作模具钢中呈尖锐角的大块碳化物极大地降低了滚丝轮的寿命;通过固溶双细化处理后碳化物尺寸变小、尖锐角变钝;真空淬火后滚丝轮变形减小,崩刃的概率大大降低,滚丝轮的工作寿命提高到12000件以上。     

刀具刃口毛刷钝化工艺的刷子运动与刷毛磨损

对刀具切削刃进行钝化处理的要求是：使切削刃均匀钝化，从而提高刀具的加工效率。然而。毛刷的磨损增大了刃口钝化工艺的难度。     

干喷砂钝化工艺对硬质合金刀片刃口K值的影响

本文探讨干喷砂工艺对硬质合金刀片刃口K值的影响。通过采用喷射角度、喷枪压力、喷枪高度、喷射粉(白刚玉)粒度等不同工艺参数对硬质合金刀片进行干喷砂处理,采用先进的光学仪器对切削刃R值,S_y值和S_a值进行测量。结果表明:喷射角度、喷枪压力、喷枪高度与切削刃K值(K=S_y/S_a)相关,白刚玉粒度与刃口K值负相关。     

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CrWMn钢切纸刀的显微组织容易出现网状碳化物,网状碳化物所引发切纸刀的刃口微观变化会降低刃口锋利度和耐磨性.根据试验和相平衡热力学计算分析了产生网状碳化物的原因,提出了解决的工艺方法.结果表明,在热轧镶钢后的空冷过程中,容易从过饱和的奥氏体中沿晶界析出颗粒状碳化物,继续堆放冷却会形成网状碳化物;在奥氏体加碳化物的相区长时间恒温也会因晶界上扩散速度快,使碳化物聚集长大而形成网状碳化物,形成网状碳化物的温度区在880～800℃.为了防止网状碳化物形成,热轧镶钢后应风冷或喷水冷却躲过这一温度区,在此温度区进行退火处理的加热恒温时间也不应过长.     

不锈钢厨刀锋利度和耐用度影响因素分析

为全面分析不锈钢厨刀锋利度和耐用度的影响因素,对不同品牌的不锈钢厨刀进行硬度、锋利度、耐用度、刀包角、刃口厚度、材质及微观组织检测。结果分析表明：1)厨刀的硬度对锋利度及耐用度影响不大。但当刀片硬度位于(55～57)HRC区间时,产品的锋利度及耐用度较高;2)刀包角对厨刀锋利度和耐用度有较大影响,对耐用度的影响比锋利度更大;3)当刃口厚度小于0.46 mm时,随着刃口厚度的逐渐增大,锋利度及耐用度无明显的变化趋势;当刃口厚度大于0.46 mm时,厨刀的锋利度及耐用度迅速降低;4)在材料相同、刀包角和刃口厚度很接近的情况下,厨刀微观组织中的回火马氏体组织形态及分布、残余奥氏体含量及碳化物的形态和数量对最终产品的锋利度和耐用度影响很大。     

PCD刀具高速干式切削铜合金的磨损研究

使用PCD刀具对锡青铜合金材料进行高速干式切削试验,分别采用扫描电镜（SEM）、X射线能谱仪（EDS）对刀具的磨损形貌进行观察和磨损区域化学成分进行分析,并以此研究了PCD刀具的磨损机理。结果表明:在高速干式切削条件下,PCD刀具主要表现为前刀面的片状剥落和后刀面的轻微破损;同时还伴随着机械应力和热应力冲击下的脆性破损,出现崩刃、切削刃整体断裂以及前后刀面的大面积剥落。刀具磨损的主要原因是高温作用下的氧化磨损和扩散磨损。      

Evaluation of layer adhered on PCBN tools during turning of AISI D2 steel

Polycrystalline cubic boron nitride (PCBN) tools have high abrasion resistance and are thus suitable for application in the machining of steels with a high volume fraction of primary carbides in their microstructure. These tools are usually applied in the machining of steels with hardness above 45–50 HRC and in the case of application to steels with hardness below 45 HRC, the formation of an adhered layer on the rake face of the tools often occurs. This paper reports a study on the impact of the layer adhered on PCBN tools during the turning of AISI D2 steel, with 35 and 50 HRC. The microhardness and microstructure of the adhered material were determined, as well as the tool wear based on volumetric wear parameters. The layer adhered on the PCBN tool rake face has the same chemical elements as the machined steel alloy. Its microstructure is oriented in the direction of the chip flow and the primary carbides were fragmented. For the sample with 35 HRC the amount of material adhered (W_AM) on the rake face of the PCBN tool was approximately 360% higher than the steel with 50 HRC. The material layer adhered on the PCBN tool rake surface in the case of the 35 HRC steel acts as an edge (assuming the cutting function), while for the 50 HRC steel, the adhered layer intensifies the adhesion wear mechanism through spalling on the tool rake face. The results obtained provide important information for the selection of materials and grades for the development of new cutting tools.     

切削刃数量对球墨铸铁铣削性能及表面形貌特征的影响

目的 提高球墨铸铁铣削表面质量和刀具寿命。方法 通过刀具轨迹计算和切削试验,研究球墨铸铁平面铣削过程中切削刃数量对切削性能、刀具磨损和表面形貌特征的影响,并用分形维数和表面粗糙度共同表征表面形貌。结果 刀具轨迹分析表明,由于铣削过程中,刀具切削方向和进给方向间的夹角不断变化,铣削表面不同位置和方向的表面形貌存在差异,进而导致表面粗糙度存在较明显的差异。通过铣削试验研究切削刃数量对铣削表面不同位置和方向的几何特征的影响规律发现,随着切削刃数量的成倍增加,切削力显著增加,同时刀具磨损量降低了36.5%,表面粗糙度值降低了39.2%,表面轮廓分形维数值增加了4.8%。结论 增加切削刃数量可以使每齿切削力和刀具磨损均显著减小,刀具寿命显著增加,同时表面粗糙度减小,分形维数增大,即切削刃数量的增加使表面质量更好,表面轮廓结构更复杂。     

基于剪切增稠液的高速钢铣刀刃口修整

为研究剪切增稠抛光液对铣刀刃口的影响,以四刃高速钢平头立铣刀为研究对象,对高速钢刀具进行修整,测量铣刀刃口半径,并观测铣刀前刀面、后刀面以及刃口形貌。试验结果表明:修整后,铣刀刃口半径减小,但由于不同切削刃初始状态不同,刃口半径减小的程度不同,最大变化量为7.5 μm,最小变化量为0.4 μm;修整试验只是针对铣刀刃口进行修整,铣刀的前、后刀面无明显变化,磨削痕迹并没有去除;磨料粒度对修整效果有一定影响,a组、b组和c组碳化硅STF试验组修整后,平均刃口半径分别减小4.6、3.6和1.9 μm,磨粒尺寸越大,铣刀刃口半径变化越明显。      

碟轮修整对单层钎焊金刚石砂轮磨粒形貌影响研究

为揭示修整对金刚石砂轮磨粒形貌的影响规律,利用光学显微镜,分别对不同修整量下的磨粒形貌进行追踪观测;针对磨粒形貌变化,对磨粒磨损形式、磨粒切削刃宽度、顶面面积和刃圆半径的变化规律进行了统计分析。结果显示:在碟轮修整过程中,磨粒主要发生磨耗磨损,小部分发生破碎和断裂,且各种磨损比例均逐渐升高。随着修整量增加,磨粒平均切削刃宽度和平均顶面面积逐渐增大,而平均刃圆半径则呈现先增大后减小的变化规律。      

碳纤维/树脂基复合材料高速铣削的刀具磨损机理

采用涂层(Ti CN,Ti Al N)与无涂层超细晶粒硬质合金立铣刀对碳纤维/树脂基复合材料进行高速铣削试验,研究了刀具后刀面磨损带扩展及刀具磨损规律,并探讨了切削力、毛刺随着刀具磨损的变化趋势,观察了刀具的微观磨损形貌,分析了刀具的磨损机理。结果表明:在相同的切削条件下,无涂层刀具的后刀面磨损量及切削力最大,毛刺扩展严重,后刀面主要发生磨粒磨损,由于黏着磨损和氧化磨损对切削刃的弱化作用,主切削刃发生了微崩刃;Ti CN涂层刀具后刀面主要发生磨粒磨损,并伴随有黏着磨损和轻微的氧化磨损,失效形式为剥落和微崩刃;Ti Al N涂层刀具的后刀面磨损量及切削力最小,毛刺扩展缓慢,更适合碳纤维复合材料的加工。其后刀面主要发生了磨粒磨损,其失效形式为剥落。     

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 本文分析了6Cr21Mn11Mo1V1Nb1N汽车发动机排气门盘端面细微裂纹的成因，分析结果表明：细微裂纹系车削过程中产生的切削裂纹；碳化物沿晶界呈连续网状分布显著弱化了晶界，是盘端面在车削过程中产生切削裂纹的主要原因；排气门钢中碳化物沿晶界呈连续网状析出是高温时效及回火时间过长所致。     

The preparation of cutting edges using a marking laser

During the machining process, high mechanical and thermal loads occur at the cutting edge. Such loads can cause tool failure. Specifically non-uniform and sharp cutting edges that have a low cutting edge stability lead to such failures. In order to enhance the tool performance, the cutting edges are prepared by manufacturing both a pre-defined cutting edge geometry, and an appropriate cutting edge roughness. This paper describes the use of a low-cost marking laser for the preparation of cutting edges as an alternative to conventional preparation techniques, such as brushing or blasting. Cutting edge radii of 9?C47 ??m can be prepared with a machining accuracy of 1.5 ??m. The maximum preparation time for an individual cutting edge is approximately 10 s. Uncoated indexable inserts manufactured in this way were tested in a face milling operation. The results of these investigations (using prepared cutting edges) show both an increase in tool life and an improved surface roughness of the machined workpieces compared to those using non-prepared cutting edges.     

A new thermomechanical model of cutting applied to turning operations. Part I. Theory

In this paper, an analytical approach is used to model the thermomechanical process of chip formation in a turning operation. In order to study the effects of the cutting edge geometry, it is important to analyse its global and local effects such as the chip flow direction, the cutting forces and the temperature distribution at the rake face. To take into account the real cutting edge geometry, the engaged part in cutting of the rounded nose is decomposed into a set of cutting edge elements. Thus each elementary chip produced by a straight cutting edge element, is obtained from an oblique cutting process. The fact that the local chip flow is imposed by the global chip movement is accounted for by considering appropriate interactions between adjacent chip elements. Consequently, a modified version of the oblique cutting model of Moufki et al. [Int. J. Mech. Sci. 42 (2000) 1205; Int. J. Mach. Tools Manufact. 44 (9) (2004) 971] is developed and applied to each cutting edge element in order to obtain the cutting forces and the temperature distributions along the rake face. The material characteristics such as strain rate sensitivity, strain hardening and thermal softening, the thermomechanical coupling and the inertia effects are taken into account in the modelling. The model can be used to predict the cutting forces, the global chip flow direction, the surface contact between chip and tool and the temperature distribution at the rake face which affects strongly the tool wear. Part II of this work consists in a parametric study where the effects of cutting conditions, cutting edge geometry, and friction at the tool–chip interface are investigated. The tendencies predicted by the model are also compared qualitatively with the experimental trends founded in the literature.