新型陶瓷刀具在超硬材料加工中的应用

Sj3N4基陶瓷刀具通过硬质颗粒弥散,使硬度和切削能力得到提高,能对传统刀具难以加工的一系列超硬难加工材料进行顺利的切削。新型陶瓷刀具在轧辊、碴浆泵、矿山机械、轴承、汽车等领域中得到了应用,提高了生产效率,降低了加工成本,促进了机械加工工艺的改革并带来很大的社会经济效益。     

The performance of ceramic and cermet cutting tools for the machining of austempered ductile iron

In this study, the machinability of austempered ductile iron (ADI) having a ferritic structure was examined. For this purpose, three types of ductile iron materials (as cast, ADI-250, ADI-375) and two different types of cutting tool materials (ceramics and cermet) were used. To emphasize the role of austempering process, ductile iron (DI) specimens are first austenitized in salt bath at 900°C for 120 minutes after which they are quenched in salt bath at 250°C (ADI-250) and 375°C (ADI-375) for 120 min. Machining tests were carried out at various cutting speeds (100–500 m/min) under the constant depth of cut and feed rate. The performance of both ceramic and cermet tools were evaluated based on the workpiece surface roughness and flank wear. Wear conditions of the cutting tools were characterized by scanning electron microscope. The results point out that the lower austempering temperature results in increasing of the cutting forces, while better surface roughness is obtained. Additionally, the results indicate that the tool wear occurs mainly on the flank face. However, higher cutting speed results in chipping formation in cermet cutting tool.     

The actual geometry of the cutting tool involved in machining

Understanding actual geometry of the cutting tool involved in machining is critical to the investigation of the mechanism of cutting process. According to control pattern of the flank and the insert shape, the cutting tools are classified into four different types in this paper including S- and non-S-shaped tools with cylindrical control and conical control. By establishing all the four kinds of tools’ 3-D models, the actual geometry of the cutting tool can be obtained. Research results suggest that the actual geometry involved in machining of the S-shaped inserts whether with cylindrical control or conical control is sphere; non-S-shaped with cylindrical control tools is ellipsoid while non-S-shaped with conical control is paraboloid.     

Dry machining of aluminum for proper selection of cutting tool: tool performance and tool wear

Machining of aluminum and its alloy is very difficult due to the adhesion and diffusion of aluminum, thus the formation of built-up edge (BUE) on the surface. The BUE, which affects the surface integrity and tool life significantly, affects the service and performance of the workpiece. The minimization of BUE was carried out by selection of proper cutting speed, feed, depth of cut, and cutting tool material. This paper presents machining of rolled aluminum at cutting speeds of 336, 426, and 540 m/min, the feeds of 0.045, 0.06, and 0.09 mm/rev, and a constant depth of cut of 0.2 mm in dry condition. Five cutting tools WC SPUN grade, WC SPGN grade, WC + PVD (physical vapor deposition) TiN coating, WC + Ti (C, N) + Al₂O₃ PVD multilayer coatings, and PCD (polycrystalline diamond) were utilized for the experiments. The surface roughness produced, total flank wear, and cut chip thicknesses were measured. The characterization of the tool was carried out by a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) pattern. The chip underface was analyzed for the study of chip deformation produced after machining. The results indicated that the PCD tool provides better results in terms of roughness, tool wear, and smoother chip underface. It provides promising results in all aspects.     

Enhancing the machining performance by cutting tool surface modifications: a focused review

In machining, cutting tools suffer from severe surface wear, especially in the cutting of difficult-to-cut materials. A major cause of tool wear is the friction generated at the tool-work and tool-chip interfaces, which produces a great deal of frictional heat and abrasion. In order to extend tool life and improve the quality of machined components, a host of techniques have been applied to modify the rake and flank faces of cutting tools. These techniques aim at providing cutting tools with improved resistance to external loading, better tribological performance and/or better chemical stability. This article presents a review of the fundamentals behind which the friction and wear in machining are reduced by modifying the cutting tool surface with the commonly used techniques, such as surface coating, high energy beam treatment, and surface texturing. The effects of these surface modifications on improving the cutting performance are also analyzed. Future research directions are finally discussed.     

近年切削刀具品种及刀具材料的变化

刀具材料的发展和变化是推动金属切削工艺进展的重要因素之一。不同刀具材料的刀具销售值在刀具总销售值中的构成比能反应不同国家刀具应用水平的高低。本文分析“不同刀具材料的刀具销售值构成比”和“各种刀具大类品种构成比”的近年变化，以说明其现状与趋势。     

Wear characteristics of ceramic cutting tools in machining steel

Some ceramic materials such as Al₂O₃ which have a high compressive strength, hardness and chemical stability came into use industrially in the middle of this century as powder metallurgy produced indexable cutting tool inserts. These early ceramic tools were inherently weak in tension, impact and dynamic loading owing to their low tensile strength, toughness and transverse rupture strength; because of this their application was limited to medium productivity operations and work materials of softer grades. However, the technology of ceramic cutting tools has made great strides in the last few years through substantial improvements in their strength, toughness and wear resistivity. These modern ceramic tools have found wide and economic applications in high production machining of both cast iron and steels.In this paper the constructional characteristics of some modern ceramic tools and their wear behaviour and overall performances in machining mild steel at both low and high speeds are presented. The comparative results obtained are reported and discussed.     

Effect of cutting atmosphere on dry machining performance with Al2O3/ZrB2/ZrO2 ceramic tool

In this paper, Al₂O₃/ZrB₂/ZrO₂ ceramic cutting tool was produced by hot pressing. Dry cutting tests in air and nitrogen atmospheres were carried out on normalized AISI 1045 steel. The tool wear, cutting temperature, cutting force, and friction coefficient were measured. Compared in nitrogen, the friction coefficient in air was reduced when the cutting speed was higher than 160 m/min. Scanning electron microscopy and energy dispersive X-ray analysis techniques were employed to observe the worn surfaces of the ceramic tools, and the wear mechanisms were simultaneously discussed. Experimental data and observations revealed the formation of oxide film under air in dry machining, which related to the decrease of the friction coefficient and the improvement of cutting performance.     

Comparison of the wear resistance of selected steels and cemented carbide cutting tool materials in machining wood

An experimental investigation is described where specimens of selected steels and cemented carbides are tested to simulate cutting green wood and cured wood. Extensive results are presented that show quantitatively the progressive wear of several Stellites, steels and cemented carbides as a function of time for sliding under wet and dry conditions.A simple theoretical analysis of tool wear that applies to cutting green wood with cemented carbide tools is described. The analysis, which indicates the important parameters in the wear process, is used to predict the effect of carbide particle size on wear rate. Comparisons are made between the predicted and experimentally determined wear rates for two groups of cemented carbide materials. Good agreement is found between experimental measurements and theoretical predictions. It is shown that wear depends on carbide particle size. Superior wear resistance of cemented carbides is attributed to the high hardness and low chemical reactivity of the carbide phase. The improved wear resistance of the Stellites is attributed to the low reactivity of the matrix.     

高锰钢切削刀具的设计

高锰钢切削极易产生硬化层,很难加工。在生产实践中,通过合理地选择刀具材料、刀具结构、切削用量等,可以很好解决高锰钢难加工的问题,保证了高锰钢的加工质量。     

刀具与切削加工技术的新发展

在切削加工方面，寄希望于建立快捷生产体制的刀具产品，首推高速铣削刀具。     

工程陶瓷的加工技术

主要介绍了国内外工程陶瓷材料特种加工技术如电火花加工、激光加工、高速往复磨削、复合磨削、振动钻孔、超声波微孔等6项加工技术，以及3项常规加工新技术的开发及应用近况。     

The cutting tool stresses in finish turning of hardened steel with mixed ceramic tool

Precision hard machining is an interesting topic in manufacturing die and mold, automobile parts, and scientific research. While the hard machining has benefit advantages such as short cutting cycle time, process flexibility, and low surface roughness, there are several disadvantages such as high tooling cost, need of rigid machine tool, high cutting stresses, and residual stresses. Especially, tool stresses should be understood and dealt with to achieve successful performance of finish hard turning with ceramic cutting tool. So, the influence of cutting parameters on cutting stresses during dry finish turning of hardened (52 HRC) AISI H13 hot work steel with ceramic tool is investigated in this paper. For this aim, a series finish turning tests were performed, and the cutting forces were measured in tests. After literature procedure about finite element model (FEM), FEM is established to predict cutting stresses in finish turning of hardened AISI H13 steel with Ceramic 650 grade insert. As shown, effect of the cutting parameters on cutting tool stresses in finish turning of AISI H13 steel is obtained. The suggested results are helpful for optimizing the cutting parameters and decreasing the tool failure in finish turning applications of hardened steel.     

高速切削中的刀具材料

结合高速切削加工技术和刀具材料的研究,综合论述高速切削加工刀具材料的性能特点、研究进展和应用,展望高速切削加工刀具材料的未来。     

超硬刀具材料的发展与实验研究

超硬刀具材料有立方氮化硼和金刚石。金刚石的种类很多。本文对立方氮化硼和金刚石作了全面介绍，包括发展过程、种类、性能、制造方法和应用范围。近年，又发明了一种最新的超硬刀具材料氯化碳——CxNy，对CxNy也进行了介绍。本文还列出了部分试验数据和试验曲线。     

数控加工中对刀问题的处理

本文介绍了数控加工中对刀的基本原理和方法,对常见数控机床中对刀方法选择、NC指令选用和对刀参数设置等方面进行了详细讨论。     

Improved machining of heat-resistant materials by high-temperature embrittlement in cutting

The following hypothesis is verified: that heat-resistant materials are most easily machined at the temperature corresponding to their embrittlement. At that temperature, moreover, the mechanical characteristics ψ, δ of the material are least temperature-dependent. New methods are proposed for determining the conditions in which heat-resistant materials are most easily machined.