硬态切削高强度钢表面完整性的研究

高强度钢45CrNiMoVA以其良好的力学性能,被广泛作为车辆悬挂系统弹性零件扭杆的材料。45CrNiMoVA是典型的高强度钢,属于难加工材料,扭杆在实际应用中通常经常承受大应力、应变、冲击影响,疲劳寿命成为影响其断裂失效的重要参数。表面质量能够影响材料的疲劳强度、磨损率、耐腐蚀性等特征。硬态切削可以有助于在简化加工工艺的同时,达到预期的表面质量。对于已知的各种参数,如切削速度、进给率和切削深度对表面完整性都有很大的影响。在本试验中,表面完整性主要通过表面粗糙度、残余应力、微观硬度等方面进行分析。     

精密硬车加工轴承套圈的表面完整性试验研究

针对磨削加工中套圈精密加工存在的不足,进行精密硬车削加工轴承套圈新工艺的开发,通过加工试验分析了精密硬车加工轴承套圈的表面完整性,探究了基准面平面度、刀具磨损量等工艺参数与加工精度的对应关系。基于精密硬车削套圈试样的表面粗糙度、沟道圆度、显微硬度、热损伤、金相组织、残余应力分布、加工效率等方面的研究,得出了精密硬车削可达到磨削加工精度的结论,且金相组织稳定,不易存在热损伤,具有可控的残余应力分布和较高的加工效率,有利于产业化生产高精密轴承。利用磁性卡盘装夹套圈,分析试样基准面平面度对精密硬车削套圈沟道圆度的影响,发现提高基准面平面度可以有效提高加工套圈的沟道圆度;分析了刀具磨损对硬车削套圈加工精度的影响,得出在精密加工阶段刀具磨损量是控制套圈圆度的重要监控工艺参数的结论。     

Prediction of the Effect of Tool Interference on Surface Generation in Single-Point Diamond Turning

Tool interference has its origin from the small amplitude and low frequency vibration existing between the tool and the workpiece in single-point diamond turning (SPDT). It inevitably affects the surface quality of a diamond turned surface. In this paper, a surface topography simulation model is proposed for the prediction of the effect of tool interference on surface generation in SPDT. It makes use of the surface roughness profiles predicted at a finite number of equally spaced radial sections of a workpiece to construct the surface topography of a diamond turned surface. The approach overcomes the limitation of the existing theories that can check only for the existence of tool interference. The model was evaluated through practical cutting experiments. Experimental results were found to agree well with the predicted results.     

Tool crater wear depth modeling in CBN hard turning

Hard turning has been receiving increased attention because it offers many possible benefits over grinding in machining hardened steel. The wear of cubic boron nitride (CBN) tools, which are commonly used in hard turning, is an important issue that needs to be better understood. For hard turning to be a viable replacement technology, the high cost of CBN cutting tools and the cost of down-time for tool changing must be minimized. In addition to progressive flank wear, microchipping and tool breakage (which lead to early tool failure) are prone to occur under aggressive machining conditions due to significant crater wear and weakening of the cutting edge. The objective of this study is to model the CBN tool crater wear depth (K_T) to guide the design of CBN tool geometry and to optimize cutting parameters in finish hard turning. First, the main wear mechanisms (abrasion, adhesion, and diffusion) in hard turning are discussed and the associated wear volume loss models are developed as functions of cutting temperature, stress, and other process information. Then, the crater wear depth is predicted in terms of tool/work material properties and process information. Finally, the proposed model is experimentally validated in finish turning of hardened 52100 bearing steel using a low CBN content tool. The comparison between model predictions and experimental results shows reasonable agreement, and the results suggest that adhesion is the dominant wear mechanism within the range of conditions that were investigated.     

Effects of cutting edge geometry, workpiece hardness, feed rate and cutting speed on surface roughness and forces in finish turning of hardened AISI H13 steel

In this study, the effects of cutting edge geometry, workpiece hardness, feed rate and cutting speed on surface roughness and resultant forces in the finish hard turning of AISI H13 steel were experimentally investigated. Cubic boron nitrite inserts with two distinct edge preparations and through-hardened AISI H13 steel bars were used. Four-factor (hardness, edge geometry, feed rate and cutting speed) two-level fractional experiments were conducted and statistical analysis of variance was performed. During hard turning experiments, three components of tool forces and roughness of the machined surface were measured. This study shows that the effects of workpiece hardness, cutting edge geometry, feed rate and cutting speed on surface roughness are statistically significant. The effects of two-factor interactions of the edge geometry and the workpiece hardness, the edge geometry and the feed rate, and the cutting speed and feed rate also appeared to be important. Especially honed edge geometry and lower workpiece surface hardness resulted in better surface roughness. Cutting-edge geometry, workpiece hardness and cutting speed are found to be affecting force components. The lower workpiece surface hardness and honed edge geometry resulted in lower tangential and radial forces.     

硬态切削与磨削工艺的表面完整性

硬态切削具有良好的加工柔性、经济性和环保性,在对工件性能起关键作用的精加工中,已成为磨削加工的有力挑战者。表面完整性是评价加工质量和工件机械性能的重要指标。本文介绍了硬态切削和磨削工艺的加工表面完整性(包括白层、表面形貌、表面粗糙度、表面残余应力、表面硬化层等),并对二者进行了比较。此外,还分析了硬态切削与磨削工艺相互结合的应用前景。     

高硬金属加工过程中表面白层的研究

综述了国内外对高硬金属加工过程中表面白层的研究现状 ,指出了当前白层研究中存在的分歧和争论 ,着重讨论了表面白层的组织结构和形成机制 ,并提出了今后的研究方向     

Workpiece Surface Integrity and Tool Life Issues When Turning Inconel 718™ Nickel Based Superalloy

Inconel 718 is one of a family of nickel-based superalloys which are used extensively in the aerospace industry in the hot sections of gas turbine engines. The literature detailing the effects of varying operating parameters on tool life when machining nickel based superalloys is comprehensive, however, relatively little of this data refers to their effects on machined workpiece surface integrity. Greater knowledge of the effects of operating parameters on surface integrity is critical to the acceptance of new cutting tool materials, tool geometries, and strategies, especially by the aerospace industry. The article initially reviews prior work on the machinability and surface integrity achieved when turning Inconel 718. Following on from this a series of experiments evaluating the effects of varying cutting tool material, geometry, and operating parameters are detailed.     

核电机组用铸钢GX4CrNi13-4车削加工表面质量研究

针对百万千瓦核电机组用铸钢GX4CrNi13-4材料进行车削试验,主要从表面粗糙度和加工变质层两方面分析其加工表面质量。采用正交试验方法,选取切削速度、进给量、切削深度和切削宽度,并考量了刀具刀尖圆弧半径和后刀面磨损等因素,以表面粗糙度(Ra和Rz值)为试验目标,研究了加工表面粗糙度的变化。在最优切削参数下Rz值可达0.792μm。最后,选取加工表面加工硬化、金相组织变化和残余应力特性三项指标研究了铸钢加工表面变质层的变化规律。     

Producing high quality hardened parts using sequential hard turning and ball burnishing operations

This paper presents a novel sequential process which incorporates optionally CBN turning operations with (CHT) or without (HT) cryogenic pre-cooling of the workpiece and ball burnishing (B) operations. The main hypothesis tested concerns the fact that cryogenic pre-cooling slightly deteriorates surface finish but at the same time it enhances the mechanical and service properties of the subsurface layer without white layer. Moreover, it indicates how this complex process (cryogenic pre-cooling, hard turning and ball burnishing) should be performed to obtain satisfactory surface integrity and service properties. Investigations include 2D and 3D surface roughness, microstructure alterations by means of SEM/BSE techniques and microhardness distribution. The geometrical, mechanical and physical improvements of surface layer properties were revealed.     

Experimental study and evaluation methodology on hard surface integrity

The Taguchi method is adopted experimentally to investigate the surface integrity (surface roughness, residual stress, and thermal damage layer) of hardened bearing steel in hard dry turning, and the validation experiments are consequently performed. It was revealed that the value and effect sequence of optimal hard turning parameter varies with different objectives of surface integrity. However, it is quite difficult to select or determine the optimal combination of hard turning parameters. A hard-turned component performance, which reflects an integrated impact of surface integrity, should be fully recognized to resolve the inherent conflict in the selection process. Based on it, an evaluation methodology composed of four steps is proposed that surface integrity should be evaluated by the service/fatigue life of hard-turned components and therefore turning parameters. It bears significance for super-finish hard turning further application in respect that it provides an integrated approach for hard turning parameter optimization to achieve a superior surface integrity. Funded by the Ministry of Education of China- “985” of international cooperation project “Clean Manufacturing Technology”.     

陶瓷结合剂CBN砂轮磨削GH4169高温合金的磨削加工性与磨削表面完整性

本文对ＣＢＮ砂轮磨削ＧＨ４１６９高温合金的磨削加工性和磨削表面完整性进行了系统研究。研究了ＣＢＮＳ轮磨削ＧＨ４１６９高温合金时磨削参数对磨削力、磨削温度和磨削比的影响规律；在正交试验和显著性分析的基础上．建立了磨削力和磨削温度的经验公式。在ＣＢＮ砂轮磨削ＧＨ４１６９高温合金磨削表面完整性的试验研究中，对磨削表面粗糙度、磨削表面硬化及磨削表面残余应力进行了研究．建立了表面完整性指标与磨削参数之间的关系。并根据正交试验建立了磨削表面粗糙度的经验公式。     

硬车削及其加工技术

介绍了硬车削加工的特点,硬车削加工所需的条件;分析了硬车削应用不广的原因,指出硬车削是一种高效洁净的工艺方法,具有广阔的应用前景。     

GH4169高速车削参数对加工表面完整性影响研究

使用PVD-TiAlN涂层硬质合金刀片进行高温合金GH4169的高速车削正交试验,建立了表面完整性特征中表面粗糙度、表面残余应力、显微硬度的经验公式,分析了车削参数对表面完整性各特征量的影响规律,并观测了高速车削加工的表面形貌。结果表明:表面粗糙度随车削速度的增加而减小,随进给量和切削深度的增加而增大,进给量是影响表面粗糙度的最主要因素;随着进给量的增加,表面形貌变差;轴向残余应力表现为压应力,切向残余应力表现为拉应力,减小进给量,降低车削速度可减小车削加工的残余应力,轴向残余应力对进给量最敏感,切向残余应力对切削深度最敏感;显微硬度随车削速度的增大而增加,车削速度是影响显微硬度的主要因素。     

Integration of Cutting Parameter Selection and Tool Adjustment Decisions for Multipass Turning

This paper presents an integrated approach to simultaneous optimisation of machining parameters, including machining speed, feedrate and depth of cut, number of passes, tool adjustment interval, and the amount of adjustment. Associated models have been developed for both small parts, where each tool can be used to machine several parts, and large parts, where several tools may be required for a single workpiece. Examples are given to demonstrate the application of the proposed models. The impact of machining parameters and tool cost on tool adjustment and the effect of rapid reverse on the final solution are also discussed.     

Performance of coated and uncoated mixed ceramic tools in hard turning process

The present contribution deals with the study of the effects of cutting speed, feed rate and depth of cut on the performance of machining which traditionally named “machinability”. The focus is made on the effect of the pre-cited cutting parameters on the evolution of surface roughness and cutting force components during hard turning of AISI D3 cold work tool steel with CC6050 and CC650 ceramic inserts. Also, for both ceramics a comparison of their wear evolution with time and its impact on the surface equality was proposed. The planning of experiments was based on Taguchi’s L₁₆ orthogonal array. The analysis of variance (ANOVA), the signal-to-noise ratio and response surface methodology (RSM) were adopted. Consequently, the validity of proposed linear regression model was checked and the most important parameter affecting the surface roughness and cutting force components were determined. Furthermore, in order to determine the levels of the cutting regime that lead to minimum surface roughness and minimum machining force the relationship between cutting factors was analyzed. The results revealed that the surface quality obtained with the coated CC6050 ceramic insert is 1.6 times better than the one obtained with uncoated CC650 ceramic insert. However, the uncoated ceramic insert was useful in reducing the machining force.     

Hard turning using HiPIMS-coated carbide tools: Wear behavior under dry and minimum quantity lubrication (MQL)

In the present work, experimental investigations carried out to assess the applicability of HiPIMS (High Power Impulse Magnetron Sputtering)-coated carbide tools to hard turning (55 HRC) and to address the widely debated topic about the use of coolants in hard turning are presented. Tool wear progressions and hence, tool life, different tool wear forms and wear mechanisms observed for tools coated with HiPIMS coating technique, namely, nanocomposite AlTiN, nanocomposite multi-layer TiAlN/TiSiN and nanocrystalline AlTiCrN are presented along with the images captured by digital and electron microscope. Characterization results of all the coated tools in terms of their average coating thickness (measured using Calotest and Fractographs), adhesion strength of the coating(s) (determined using Scratch test), composition and microhardness (using EDAX and Vickers microhardness test, respectively) are presented. Experimental observations indicate higher tool life with nanocrystalline AlTiCrN coated carbide tools which shows encouraging potential of these tools to hard turning. Improvement in tool life of almost 20–25% has been observed under minimum quantity lubrication (MQL) due to better cooling and lubricating effects. However, this effect was more prominent at higher cutting speed of 150 m/min.     

硬态干式切削技术及其应用

阐述了硬态干式切削技术的优越性及其研究现状,讨论了实现硬态干式切削加工的关键技术,对我国目前推广应用硬态切削技术存在的主要问题进行了深入研究.     

铜、铝合金镜面切削加工的表面质量

研究了天然单晶金刚石刀具对铜、铝合金进行超精切削加工时,材料的组织、性能与残余应力对表面质量如反射率、面形、显微粗糙度等的影响,并就优化表面特性和加工工序进行了探讨.     

Characterization of Tool Wear Measurement with Relation to the Surface Roughness in Turning

Abstract

In turning, an accurate gauging of tool wear condition is an essential part of process control due to adverse effects on dimensional tolerance and surface finish quality. When the surface roughness is the primary concern, the conventional measure of tool wear is found to be imprecise because it provides very little information on the wear patterns in tool nose and flank. A tool wear model, developed in this study, represents the wear condition more comprehensively and accurately with relation to the surface roughness. Experimental results validate the model, showing 92% accuracy between the predicted surface roughness and the actual measurements.