Wear Mechanism of Cemented Carbide Tool in High Speed Milling of Stainless Steel

Adhesion of cutting tool and chip often occurs when machining stainless steels with cemented carbide tools. Wear mechanism of cemented carbide tool in high speed milling of stainless steel 0Cr13Ni4 Mo was studied in this work. Machining tests on high speed milling of 0Cr13Ni4 Mo with a cemented carbide tool are conducted. The cutting force and cutting temperature are measured. The wear pattern is recorded and analyzed by high?speed camera, scanning electron microscope(SEM) and energy dispersive X?ray spectroscopy(EDS). It is found that adhesive wear was the dominant wear pattern causing tool failure. The process and microcosmic mechanism of the tool's adhesive wear are analyzed and discussed based on the experimental results. It is shown that adhesive wear of the tool occurs due to the wear of coating, the a nity of elements Fe and Co, and the grinding of workpiece materials to the tool material. The process of adhesive wear includes both microcosmic elements di usion and macroscopic cyclic process of adhe?sion, tearing and fracture.     

An Investigation of the Wear Mechanisms of Polycrystalline Cubic Boron Nitride (PCBN) Tools when End Milling Hardened Steels at Low/Medium Cutting Speeds

The commercial availability of PCBN tools has created the possibility for great improvements in the area of machining hardened steels. Roughing and finishing cuts can be carried out to achieve a surface finish as good as that obtained by grinding. Through this procedure, fabrication time can be greatly reduced and quality increased. This work presents a study of the wear of PCBN and cemented carbide tools when end milling hardened steels at low/medium cutting speeds. The experiments were carried out using a 12.0 mm diameter end milling tool with an indexable insert tipped with PCBN. Removal rate was 384 mm 3 min −1 . Carbide inserts were also tested under the same cutting conditions. The tests were carried out in the dry condition. Three different hardened steels were cut and the wear mechanism was investigated using a scanning electronic microscope (SEM). The minimal wear mechanism found was a combination of adhesion and abrasion. The wear occurred predominantly on the flank face, although some indications of crater wear were also detected. The amount of wear was significantly smaller for PCBN tools than for cemented carbide tools.     

Tool wear reduction through an externally applied electric current

It was shown in a previous investigation that when an electric current is passed between two sliding surfaces in the presence of engine oils, the wear characteristics of two surfaces could be altered significantly, but not friction. The wear on the cathode surface is decreased while the wear on the anode surface increased. The difference in wear rate of surfaces with and without current is attributed to the modification of the elemental composition of surface films. In this investigation, the concept was extended to a machining operation where it is desirable to reduce wear of the cutting tool while increasing metal removal. Two types of experiments were conducted: (a) ball-on-disk test and (b) face milling test. It was observed in ball-on-disk tests that in the presence of a metalworking fluid, the wear of the anode surface decreased significantly while the wear of the cathode surface increased slightly. Similar observations were made in face milling tests where the milling insert wear was reduced when it was the anode and increased when the insert was the cathode. In addition to wear, vibration during milling was also reduced when the insert was the anode.     

基于遗传算法的铣刀片三维复杂槽型重构技术

为了获得切削性能更优良的可转位铣刀片槽型,从而改善铣刀片的温度场和应力场,进行了三维复杂槽型铣刀片的测温试验、三维温度场分析及其模糊综合评判。基于遗传算法,提出了以受热密度函数为目标函数,以温度场模糊综合评判为驱动的铣刀片三维复杂槽型的重构算法,获得了新的波形槽型。实例验证表明,新槽型较重构前的槽型在温度场方面具有更好的性能。利用该方法同样可以构造拟合其他类型三维复杂槽型。     

硬质合金铣刀片粘结破损的研究

针对铣削难加工材料时刀具粘结破损问题,进行了用平刀片和自主研发的复杂槽型铣刀片切削3Cr1Mo1／4V高温耐热钢的测温测力试验,同时采用高速摄影观察了铣刀片切入切出时粘结切屑脱落过程,应用有限元法分析了粘结破损时温度场和应力场耦舍后的等效合成应力。理论和试验数据分析结果表明,粘结破损的主要原因是工件和刀具材料的亲合力、铣刀片的等效合成应力大于硬质舍金的强度,改变铣刀片的槽型是提高抗粘结破损的有效方法。为三雏复杂槽型铣刀片槽型的优化和重构技术提供了理论依据和试验数据。     

灰口铸铁面铣加工中修光刃磨损特性的研究

采用具有不同前角和表面处理形式的刀片,对HT250灰口铸铁进行了平面铣削试验。通过观察刀片修光刃处前后刀面的磨损状况,发现修光刃磨损可分为均匀磨损和刀尖破损导致的非均匀磨损两个阶段。结合对切削过程中刃口形貌变化规律的研究,分析了铸铁面铣过程中刀片几何形状、表面处理形式等因素对修光刃磨损特性的影响。     

三维复杂槽型铣刀片耦合场的数值模拟

为研究三维复杂槽型铣刀片的切削性能和失效机理,运用数值模拟技术对三维复杂槽型铣刀片和平前刀面铣刀片进行了热应力场、热应力与机械应力的耦合场分析。通过有限元分析,得到了两种铣刀片的应力集中区和危险区,经与试验结果对比,证明了有限元分析结果的正确性,说明三维槽型铣刀片具有优于平前刀面铣刀片的切削性能,从而预测在铣刀片上开出合理的槽型能有效地改善切削性能。     

基于密度函数的三维复杂槽型铣刀片物理场分析

以哈尔滨理工大学开发的波形刃(前刀面为波形曲面)铣刀片为例,在铣削力数学模型基础上,通过铣削力试验以及切屑与前刀面接触面积试验,建立了三维复杂槽型铣刀片前刀面的受力密度函数;基于该函数,对波形刃铣刀片进行了应力场分析。在铣削温度数学模型基础上,运用传热学理论,建立了波形刃铣刀片表面受热密度函数;基于该函数,对波形刃铣刀片进行了温度场分析。这些研究结果可为槽型优选技术的研究打下理论基础。     

钛合金零件高速铣削刀具磨损的试验研究

高速铣削钛合金时,由于切削区内的切削温度高,加剧了刀具的磨损。通过对钛合金TC4的高速铣削实验,得出带TiA lN涂层的硬质合金刀具切削钛合金TC4时的刀具磨损的变化规律和刀具耐用度公式。通过对刀具磨损特性的分析,研究结果主要是刀具表面层的粘结相Co在高温下丧失对WC颗粒的结合强度,磨损机理以高温下的粘结层撕裂磨损为主。     

Friction of PM ferritic stainless steels at temperatures up to 300 °C

Two ferritic stainless steels (409Nb and 434L) manufactured through powder metallurgical techniques were wear tested at different temperature conditions (up to 300 °C). Two sliding speeds were used, and tests were carried out against a wrought austenitic stainless steel. Materials’ wear performance was characterized through friction coefficients and analysis of wear tracks was carried out through scanning electron microscopy. Results have shown an adhesive wear mechanism. Oxidized ferrite particles have also been found on wear tracks.     

钛合金铣削过程刀具前刀面磨损解析建模

钛合金Ti6Al4V作为典型的航空航天难加工材料,在其铣削过程中硬质合金刀具的磨损会降低加工过程稳定性,进而影响加工效率和已加工表面表面质量。刀具前刀面磨损会导致刀具刃口强度降低,并影响切屑的流向和折断情况。针对前刀面磨损机理进行分析并构建了月牙洼磨损深度预测模型。首先运用解析方法构建了前刀面应力场模型,得到切屑在前刀面滑动过程中的刀具前刀面应力分布情况及磨损位置。基于刀-屑接触关系的基础上建立了前刀面温度场模型。然后,基于所得刀具前刀面应力与温度分布,构建综合考虑磨粒磨损、粘结磨损与扩散磨损的铣刀月牙洼磨损深度预测模型,获得月牙洼磨损预测曲线;结合铣刀月牙洼磨损带沿切削刃方向分布的特点,建立了随时间变化的铣刀前刀面磨损体积预测模型。最后通过试验验证了切削宽度对前刀面磨损的影响规律,预测结果与试验测量值具有较好的吻合性。结果表明随着切削宽度的增加,月牙洼磨损深度及前刀面磨损体积都随之增加。研究结果为钛合金铣削用刀具的设计和切削参数的合理选择提供了理论基础。     

TOOL WEAR PREDICTION FROM ACOUSTIC EMISSION AND SURFACE CHARACTERISTICS VIA AN ARTIFICIAL NEURAL NETWORK

We examine the application of an artificial neural network to classification of tool wear states in face milling. The input features were derived from measurements of acoustic emission during machining and topography of the machined surfaces. Five input features were applied to the back-propagating neural network to predict a wear state of light, medium or heavy wear. We present results from milling experiments with multi- and single-point cutting and compare the neural network predictions with observed cutting insert wear states.     

SY钢铣削参数优化及刀具磨损机理的试验研究

通过正交切削试验,研究了用YW2和M2两种硬质合金刀具铣削SY钢新型垃圾焚烧炉炉排材料的切削性能,并获得了优化切削参数。研究结果表明:YW2硬质合金刀具更适合切削加工SY钢;YW2硬质合金铣刀的磨损机理为硬质点磨损、氧化磨损和粘结磨损。     

A study on wear and wear mechanism of exhaust valve and seat insert depending on different speeds using a simulator

The wear of engine valve and seat insert is one of the most important factors which affect engine performance. Because of higher demands on performance and the increasing use of alternative fuel, engine valve and seat insert are challenged with greater wear problems than in the past. In order to solve the above problems, a simulator was developed to be able to generate and control high temperatures and various speeds during motion. The wear simulator is considered to be a valid simulation of the engine valve and seat insert wear process with various speeds during engine activity. This work focuses on the different degrees of wear at three different singular test speeds (10 Hz, 25 Hz & multi-Hz). For this study, the temperature of the outer surface of the seat insert was controlled at 350°C, and the test load was 1960 N. The test cycle number was 6.0×10⁶. The mean (±standard error) wear depth of the valve at 10 Hz and 25 Hz was 45.1 (±3.7)μm and 81.7 (±2.5)μm, respectively. The mean wear depth of the seat insert at 10 Hz and 25 Hz was 52.7 (±3.9) μm and 91.2 (±2.7) μm, respectively. In the case of multi-Hz it was 70.7 (±2.4)/on and 77.4 (±3.8) μm, respectively. It was found that higher speed (25 Hz) cause a greater degree of wear than lower speed (10 Hz) under identical test condition (temperature, valve displacement, cycle number and test load). In the wear mechanisms of valves, adhesive wear, shear strain and abrasive wear could be observed. Also, in the wear mechanisms of seat inserts, adhesive wear, surface fatigue wear and abrasive wear could be observed.     

气体风冷高速铣削的刀具磨损研究

立铣刀高速铣削方式加工可显著提高淬硬钢模具的加工效率,但同时也存在切削温度高、刀具磨损快的问题。对刀具与工件的切削接触区域进行充分冷却及润滑是解决此问题的有效方法。对气体风冷高速切削展开刀具磨损研究,涉及两种气体冷却方法—压缩气体冷却法以及涡流管冷却法。实验结果表明,涡流管冷却法相比压缩气体冷却法可降低切削区域温度,有效减轻切屑粘结及粘结磨损现象,最终有效降低立铣刀刀刃的剥落宽度以及刀具磨损程度。     

基于二维元胞自动机的铣刀片温度场算法研究

切削热是铣刀片磨损和破损产生的重要原因.对铣刀片温度场研究的传统方法是有限元法.为了实现三维复杂槽型铣刀片槽型优化中能直接利用分析得到的数据进行自组织动态设计,文中结合切削温度试验,利用元胞自动机理论对铣刀片温度场进行研究,建立了二维波形刃铣刀片温度场算法系统,得出切削中各点的温度场,为刀片槽型重构奠定基础.     

硬质合金刀具铣削30CrNi3MoV高强度钢的切削性能研究

30CrNi3MoV高强度钢是某兵器型号专用的难加工材料。本文在分析材料铣削特性的基础上,选择了合理的铣刀盘和铣刀片的几何参数,通过刀具磨损与耐用度对比试验优选出了最佳的硬质合金刀具牌号,并给出了铣削过程中硬质合金铣刀片的典型磨破损形态。研究结果表明:添加钽、铌的硬质合金是解决30CrNi3MoV高强度钢铣削工艺理想的刀具材料,在92m/min~186m/min的铣削速度范围内,刀具耐用度可达10min~49min;由于材料切削温度高和机械冲击严重,铣刀片的磨破损形态主要表现为后刀面上狭长的热磨损带,倒棱上长方形的磨损坑,前刀面上扇形剥落和刀尖处三角形崩碎破损等。     

波形刃铣刀片温度场的试验研究

利用大型软件ANSYS对波形刃铣刀片及平前刀面铣刀片进行了有限元分析,并应用模糊数学理论对其温度场进行了模糊综合评判,预测了三维复杂槽型波形刃铣刀片的优越性能;通过对难加工材料3Cr-1Mo-1/4V钢的铣削试验,对采集数据应用Matlab软件进行处理,得到前刀面刀—屑接触区平均温度与时间关系的试验方程,对比分析也证明了波形刃铣刀片的优越性。     

铣削粉末冶金高温合金的刀具优选试验

针对粉末冶金高温合金材料的铣削特性,选择了合理的刀片材质。通过刀具磨损与寿命对比试验,优选出了最佳的刀片牌号及几何参数。研究结果表明:SECO SEMX1505AFTN-MD20-F30M涂层硬质合金刀片适用于铣削粉末冶金高温合金,并对涂层硬质合金刀具前、后刀面的磨损形貌和失效机理进行了分析。     

Experiment, modeling, and analysis for temperature field of milling insert

This paper presents a theoretical and experimental study of the dynamic temperature field on a milling insert with complex groove. Experimental measurements of milling temperature using the thermocouple technique were performed. A mathematical model of the temperature field of the insert was established. A finite element model of the insert was built to simulate the temperature field. The boundary condition was determined by the experimental data and mathematical calculation, and then the temperature field of the milling insert was simulated through finite element analysis. The temperature distribution in a cut-in/cut-out cycle was obtained.