Investigating the Tool Life, Cutting Force Components, and Surface Roughness of AISI 302 Stainless Steel Material Under Oblique Machining

The aim of this work is to investigate the machinability of austenitic AISI 302 stainless steel under oblique cutting. This can be achieved by studying the cutting forces, analysis of tool life, and investigation of the surface roughness at different cutting conditions and nose radius. A factorial experiment and analysis of variance technique are used in which several factors are evaluated for their effects on each level. The machinability experiments are based on design of experiments to obtain empirical equations for machinability values for machining conditions such as speed, feed, depth of cut, and nose radius. The parameters considered in the experiments were optimized to attain maximum tool life using a response graph and a response table. Based on the response models, dual response contours (tool life and surface roughness as a response and metal removal rate) have been plotted in cutting speed-feed planes. Evaluating the effect of the predominant variables influencing the value of tool life is very important for improving the machined product quality.     

难加工材料高速切削力非线性特征规律的最大熵谱分析与小波分析

在切削速度范围157～1 000 m/min内，综合应用析因试验与速度单因素试验，对航空用难加工材料2Cr13马氏体不锈钢进行了高速干式铣削试验。在分析其切削力显著性影响因素的基础上，对切削力随机信号进行了现代谱分析与小波分析。研究结果表明，高速切削马氏体不锈钢材料时，切削速度和每齿进给量之间的交互作用对切削力有显著影响；铣削深度和每齿进给量之间的交互作用在切削力响应信号中表现为低频周期信号；低频周期信号与高频信号叠加后，其波形的振幅将会增大。     

Experimental Study on Force of Electric Heating Drilling to Hard-to-Cut Materials

In this study, a simple and flexible transplantation device of electric heating drilling is developed for hard-to-cut materials. Based on this device, small holes (diameter of 1–3 mm) are drilled for stainless steel 1Cr18Ni9Ti and high manganese steel ZGMn13 adopting hard carbide twist drill YG6A. In the process of electric heating drilling, the dynamic change in drilling force (including axial force and torque) is discussed with the change in variant heating current, cutting speed, and feed. Experimental data show that axial force and torque increase with increasing cutting speed and feed, and with increasing heating current, total drilling force is obviously reduced in the initial stage, then it increases slightly over time. The heating current helps to reduce axial force and torque, which shows that electric hot drilling is effective in hard-to-cut materials.     

Analysis of hard turning process:thermal aspects

In manufacturing sector,hard turning has emerged as a vital machining process for cutting hardened steels.Besides many advantages of hard turning operations,one has to implement to achieve close tolerances in terms of surface finish,high product quality,reduced machining time,low operating cost and environmental friendly characteristics.In the study,three dimensional(3D) computer aided engineering(CAE) based simulation of hard turning by using commercial software DEFORM 3D has been compared to the experimental results of stresses,temperatures and tool forces in machining of AISI D3 and AISI H13 steel using mixed ceramic inserts(CC6050).In the following analysis,orthogonal cutting models are proposed,considering several processing parameters such as cutting speed,feed and depth of cut.An exhaustive friction modelling at the tool-work interface is carried out.Work material flow around the cutting edge is carefully modelled with adaptive re-meshing simulation capability of DEFORM 3D.The process simulations are performed at constant feed rate(0.075 mm/r) and cutting speed(155 m/min),and analysis is focused on stresses,forces and temperatures generated during the process of machining.Close agreement is observed between the CAE simulation and experimental values.     

304不锈钢箔材在不同应变速率下的拉伸性能研究

304不锈钢是一种常用的奥氏体不锈钢.在拉伸应变过程中,应变速率的变化会诱发马氏体转变量和转变速率,以及内部组织滑移线、位错、层错、形变孪晶密度的转变量和转变速率的不同,从而表现出不同的应变硬化行为.本文针对0.1 mm厚度304奥氏体不锈钢箔材,从断后伸长率,断面收缩率,屈服强度,抗拉强度及硬化指数5个方面,研究了室温条件下不同应变速率对其拉伸性能的影响.实验结果表明：马氏体转变理论同样适用于304奥氏体不锈钢箔材, 且0.1 mm厚度304不锈钢存在“越薄越脆,越小越强”的尺寸效应现象;同时,0.1 mm厚度304奥氏体不锈钢箔材拉伸力学性能随应变速率的变化主要表现在以下几方面：断后延伸率和断面收缩率均随着应变速率的增加而降低;低应变速率时,随着应变速率的增加屈服强度增大,而抗拉强度随应变速率的提高呈现减弱的相反规律;高应变速率下,304奥氏体不锈钢的强度主要由材料本身性能决定,应变速率的改变对强度的影响较小;准静态低应变速率下,硬化指数随应变速率增大而升高,较高应变速率下,硬化指数与应变速率变化无关.     

Prediction of cutting force based on machining parameters on AL7075-T6 aluminum alloy by response surface methodology in end milling

Cutting forces modeling is the basic to understand the cutting process, which should be kept in minimum to reduce tool deflection, vibration, tool wear and optimize the process parameters in order to obtain a high quality product within minimum machining time. In this paper a statistical model has been developed to predict cutting force in terms of geometrical parameters such as rake angle, nose radius of cutting tool and machining parameters such as cutting speed, cutting feed and axial depth of cut. Response surface methodology experimental design was employed for conducting experiments. The work piece material is Aluminum (Al 7075-T6) and the tool used is high speed steel end mill cutter with different tool geometry. The cutting forces are measured using three axis milling tool dynamometer. The second order mathematical model in terms of machining parameters is developed for predicting cutting forces. The adequacy of the model is checked by employing ANOVA. The direct effect of the process parameter with cutting forces are analyzed, which helps to select process parameter in order to keep cutting forces minimum, which ensures the stability of end milling process. The study observed that feed rate has the highest statistical and physical influence on cutting force.     

Fabrication of nanostructure in inner-surface of AISI 304 stainless steel pipe with surface plastic deformation

In the present investigation, a pipe inner-surface grinding (PISG) technique was developed to fabricate nanostructure in the inner-surface of an austenitic 304 stainless steel pipe. PISG was performed by high speed shearing with hard sphere tips, leading to gradient distribution of strain, strain rate and strain gradient along depth. Nano-austenite with an average boundary spacing of 20?nm was generated, followed by deformation microstructure characterized by shear bands, multi- and uni-directional twins and planar dislocation arrays. Deformation induced grain refinement of austenitic 304 stainless steel with low stacking fault energy (SFE) covering 4–5 order’s magnitude of length scales toward nanometer regime was unified.     

Investigating the Machinability of AISI 420 Stainless Steel Using Factorial Design

This work aims at studying the machining characteristics of high-strength materials using carbide cutting tool inserts at different cutting conditions. This is an essential step in building up an accurate machining information system. The tested material is high-strength stainless steel of the AISI 420 type. Machining tests were carried out using orthogonal cutting conducted to investigate the machining characteristics for high-strength stainless steel AISI 420 at different cutting conditions and tool rake angles. This assessment is achieved by investigating the effect of cutting parameters (cutting speed, feed, depth of cut, and tool geometry) on cutting forces, specific cutting energy, shear angle, coefficient of friction, shear stress, shear strain, and shear strain rate. Empirical equations and a correlation for the behavior of each of the output responses were investigated as a function of the independent variables. Main effect and interaction plot were presented for the most influential factors affecting the main cutting force and the power consumed.     

Investigation of the influential parameters of machining of AISI 304 stainless steel

Austenitic stainless steels are hard materials to machine, due to their high strength, high ductility and low thermal conductivity. The last characteristic results in heat concentration at the tool cutting edge. This paper aims to optimize turning parameters of AISI 304 stainless steel. Turning tests have been performed in three different feed rates (0.2, 0.3, 0.4 mm/rev) at the cutting speeds of 100, 125, 150, 175 and 200 m/min with and without cutting fluid. A design of experiments (DOE) and an analysis of variance (ANOVA) have been made to determine the effects of each parameter on the tool wear and the surface roughness. It is being inferred that cutting speed has the main influence on the flank wear and as it increases to 175 m/min, the flank wear decreases. The feed rate has the most important influence on the surface roughness and as it decreases, the surface roughness also decreases. Also, the application of cutting fluid results in longer tool life and better surface finish.     

Economical and ecological cryogenic machining of AISI 304 austenitic stainless steel

 While it is a clean alternative to conventional machining using environmentally polluting cutting oils and emulsions, cryogenic machining using liquid nitrogen has been reported to increase cutting forces and shorten tool life when cutting AISI 304 austenitic stainless steel. This paper presents improved results by using an economical cryogenic cooling approach designed after studying the cryogenic properties of the stainless steel material. By injecting a small amount of liquid nitrogen to the chip–tool interface, but not to the workpiece, this approach yielded a 67% tool-life improvement at 3.82 m/s and a 43% improvement at the medium speed of 3.40 m/s when compared with conventional emulsion cooling. It improved machining productivity and reduced production cost. In this study, different cryogenic machining approaches were compared in the machining test using commercial carbide inserts. The results show the cooling approach is crucial in attaining the benefits of cryogenic machining in cutting stainless steel. Received: 7 February 2000 / Accepted: 30 April 2000     

Ranges of application of free-cutting steels and recommended tool materials

Abstract

Four low carbonfree-cutting steels (0·11% carbon resulphurised, 0·11% carbon leaded–resulphurised, 0·08% carbon resulphurised, and 0·15% carbon leaded) were turned, dry, with a series of six types of cutting tool in which rake angle, tool material, and coating were varied (5° rake, high speed steel, TiN coated and uncoated; 15° rake, high speed steel, TiN coated and uncoated; 5° rake, cemented carbide, TiN coated and uncoated) in order to determine the optimum tool–workpiece combination for three cutting speed ranges: a low speed range in which the built-up edge (BUE) was forming or about to form; a speed range covering the BUE regime; and a higher speed range in which the BUE became a built-up layer (BUL). Tool–workpiece interaction was assessed by measurement of cutting forces, chip form, surface finish, tool temperature, and wear. It is suggested by the results that the best combination in the low speed range is that of leaded–resulphurised steel and uncoated high speed steel. In the BUE range, the combination of leaded steels and uncoated tools should be avoided; at higher speeds, coated tools are preferred, with non-resulphurised leaded steel giving the lowest tool temperatures and highest cutting speeds before ultimate failure. These recommendations should be treated with caution and used only as guidelines.

MST/867     

Experimental investigation of cutting parameters influence on surface roughness and cutting forces in hard turning of X38CrMoV5-1 with CBN tool

This experimental investigation was conducted to determine the effects of cutting conditions on surface roughness and cutting forces in hard turning of X38CrMoV5-1. This steel was hardened at 50 HRC and machined with CBN tool. This is employed for the manufacture of helicopter rotor blades and forging dies. Combined effects of three cutting parameters, namely cutting speed, feed rate and depth of cut, on the six performance outputs-surface roughness parameters and cutting force components, are explored by analysis of variance (ANOVA). Optimal cutting conditions for each performance level are established. The relationship between the variables and the technological parameters is determined through the response surface methodology (RSM), using a quadratic regression model. Results show how much surface roughness is mainly influenced by feed rate and cutting speed. The depth of cut exhibits maximum influence on cutting force components as compared to the feed rate and cutting speed.     

A review on nickel-free nitrogen containing austenitic stainless steels for biomedical applications

The field of biomaterials has become a vital area, as these materials can enhance the quality and longevity of human life. Metallic materials are often used as biomaterials to replace structural components of the human body. Stainless steels, cobalt–chromium alloys, commercially pure titanium and its alloys are typical metallic biomaterials that are being used for implant devices. Stainless steels have been widely used as biomaterials because of their very low cost as compared to other metallic materials, good mechanical and corrosion resistant properties and adequate biocompatibility. However, the adverse effects of nickel ions being released into the human body have promoted the development of “nickel-free nitrogen containing austenitic stainless steels” for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also much improves steel properties. Here we review the harmful effects associated with nickel and emphatically the advantages of nitrogen in stainless steel, as well as the development of nickel-free nitrogen containing stainless steels for medical applications. By combining the benefits of stable austenitic structure, high strength, better corrosion and wear resistance and superior biocompatibility in comparison to the currently used austenitic stainless steel (e.g. 316L), the newly developed nickel-free high nitrogen austenitic stainless steel is a reliable substitute for the conventionally used medical stainless steels.     

金相学史话 (4):合金钢的早期发展史

Faraday进入皇家学院(Royal Institutio n)后,在1820-1822年间从事包括铜、镍、铬及贵金属在内的合金钢研究,尽管未发展出有实际用途的钢种,也可算是合金钢研究的先驱.1856年转炉炼钢法出现后,钢产量猛增,Mu sh et高碳高钨自淬火刀具钢应运而生(1868),逐渐发展成18\|4\|1高速钢(1906).Hadfield在 1882年研制出高碳高锰奥氏体耐磨钢,成分至今未变.他还研制出硅钢片,并在1903年制出第一台铁损小的变压器.Brearley在1913年研制出低碳高铬(1Cr13)马氏体不锈钢,在这之后,铬镍奥氏体不锈钢才问世.本世纪初汽车工业的兴起,促进了合金结构钢的发展(合金钢牌号前面冠以SAE就是美国汽车工程师学会的缩写),而两次世界大战都伴随有合金钢的产量及品种的大发展.     

Optimizing the performance of high speed steel circular saw blades machining cupro 107, Inconel 600L and Nimonic PK31 nickel based alloys

Nickel based alloys are machined by methods similar to those used to cut ferrous materials, however there are additional process requirements due to the poor machinability of these alloys. The current paper reports on work undertaken to optimize the cutting conditions for high speed steel circular saw blades machining materials from three of the principal categories of nickel based alloy.Techniques have been developed and verified that simulate the cutting characteristics of multi-point cutting tools by testing blade segments that contain representative teeth. The cutting behaviour of high speed steel circular saw blades have been simulated in this manner. Materials from three of the principal classifications of nickel based alloy; Cupro 107, Inconel 600L and Nimonic PK31, have been machined over a range of cutting feeds and speeds. Cutting and thrust forces were measured and the performance criteria, specific cutting energy (Esp) evaluated. Optimized cutting conditions for each material were determined from curves of Esp against feed rate at the selected cutting speeds.In an area of high product and material costs, the information contained within this paper will be of interest to the manufacturing engineer and end user when appraising the suitability of high speed steel circular saw blades as a tool for machining these materials.Inconel 600L and Nimonic PK31 are registered trademarks of the Inco Family of Companies.     

Surface finish prediction models for fine turning

Surface finish data were generated for aluminium alloy 390, ductile cast iron, medium carbon leaded steel 10L45, medium carbon alloy steel 4130, and inconel 718 for a wide range of machining conditions defined by cutting speed, feed and tool nose radius. These data were used to develop surface finish prediction models, as a function of cutting speed, feed, and tool nose radius, for each individual metal. A general purpose surface finish prediction model is also proposed for ductile cast iron, medium carbon leaded steel, and alloy steel. Statistical analysis of experimental data indicated that surface finish is strongly influenced by the type of metal, speed and feed of cut, and tool nose radius. While the effects of feed and tool nose radius on surface finish were generally consistent for all materials, the effect of cutting speed was not. The surface finish improved with speed for ductile cast iron, medium carbon leaded steel, medium carbon alloy steel, and aluminium alloy, but it deteriorated with speed for inconel. Apparently, speed effect on surface finish is not always positive. For all metals, the surface finish improved with the tool nose radius while it deteriorated with speed.     

Effect of δ-ferrite co-existence on hot deformation and recrystallization of austenite

This work evaluates the effect of co-existence of a large volume fraction of δ-ferrite on the hot deformation and dynamic recrystallization (DRX) of austenite using comparative hot torsion tests on AISI 304 austenitic and 2205 duplex stainless steels. The comparison was performed under similar deformation conditions (i.e. temperature and strain rate) and also under similar Zener-Hollomon, Z, values. The torsion data were combined with electron backscatter diffraction (EBSD) analysis to study the microstructure development. The results imply a considerable difference between DRX mechanisms, austenite grain sizes and also DRX kinetics of two steels. Whereas austenitic stainless steel shows the start of DRX at very low strains and then development of that microstructure based on the necklace structure, the DRX phenomena in the austenite phase of duplex structure does not proceed to a very high fraction. Also, the DRX kinetics in the austenitic steel are much higher than the austenite phase of the duplex steel. The results suggest that at a similar deformation condition the DRX grain size of austenitic steel is almost three times larger than the DRX grains of austenite phase in duplex steel. Similarly, the ratio of DRX grain size in the austenitic to the duplex structure at the same Z values is about 1.5.     

基于焊道尺寸控制的电弧增材成形高氮奥氏体不锈钢与316L不锈钢交织结构EI北大核心CSCD

采用高氮奥氏体钢与316L不锈钢丝材,对高氮奥氏体不锈钢熔覆焊道、单道多层、单层多道表面成形特性进行分析,筛选适宜的工艺参数。通过控制两种材料焊道尺寸,获得最适用于成形异材交织结构的工艺参数。利用不同道间距实验得到异材焊道的最佳道间距,并采用合理路径,制备电弧增材成形交织结构。结果表明:工艺参数的变化对高氮奥氏体不锈钢焊道表面成形特性影响极大,易出现气孔;提出异材焊道几何尺寸、截面面积匹配误差法,获得最佳工艺参数:其中高氮奥氏体钢丝材的送丝速率为5.7 m/min,316L不锈钢丝材的送丝速率为5.6 m/min,焊接速率均为0.6 m/min。通过降低起弧次数,采用闭合路径,提高了异材交织结构成形精度,减少了后处理加工。     

低频电磁场对奥氏体不锈钢铸坯组织的影响

在工业实验中研究了低频电磁场对水平连铸奥氏体不锈钢组织的影响,结果表明:在低频电磁场作用下,合适的电磁搅拌参数使奥氏体不锈钢宏观组织在一定程度上得到了明显改善,铸坯的柱状晶和等轴晶得到了显著的细化,消除了穿晶现象,等轴晶区扩大,中心缩孔、中心疏松级别明显降低;多次实验发现:对于奥氏体不锈钢,所需的搅拌强度应高于一般钢种,即使搅拌器的中心磁感应强度达900GS平均值(幅值达到1413GS),采用3～4Hz的频率,搅拌后对钢液的组织影响较小;在同样的磁场强度下,不锈钢液由于粘度大,因而其转速比碳钢液的转速约低20%～30%。     

奥氏体不锈钢滞回本构模型研究

准确的材料滞回本构模型是保证弹塑性地震反应预测准确性的基本前提,如果本构模型选取不当,会对计算结果产生较大影响。为此该文提出了奥氏体不锈钢考虑循环强化作用的单轴滞回本构模型,包括骨架准则及滞回准则。建立数学模型描述奥氏体不锈钢在循环荷载作用下的受力性能。根据提出的理论模型并利用ABAQUS用户材料子程序UMAT,采用Fortran语言二次开发了能够进行循环荷载下奥氏体不锈钢计算分析的程序。通过与试验结果进行对比,表明提出的模型能够准确描述奥氏体不锈钢材料的滞回行为,兼顾计算精度和效率,为奥氏体不锈钢结构体系强震分析提供有力工具。