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.     

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     

Numerical simulation of finish hard turning for AISI H13 die steel

A coupled thermo-mechanical model of plane-strain orthogonal turning of hardened steel was presented. In general, the flow stress models used in computer simulation of machining processes are a function of effective strain, effective strain rate and temperature developed during the cutting process. However, these models do not adequately describe the material behavior in hard machining, where the workpiece material is machined in its hardened condition. This hardness modifies the strength and work hardening characteristics of the material being cut. So, the flow stress of the work-material was taken with literature [H. Yan, J. Hua, R. Shivpuri, Development of flow stress model for hard machining of AISI H13 work tool steel. The Fourth International Conference on Physical and Numerical Simulation of Materials Processing, Shanghui in China, 2004, p. 5] in order to take into account the effect of the large strain, strain-rate, temperature and initial workpiece hardness. Then a series of numerical simulations had been done to investigate the effect of machining parameters on the machinability of hardened steel AISI H13 in finish turning process. The results obtained are helpful for optimizing process parameters and improving the design of cutting inserts in finish turning of hardened steel AISI H13.     

基于CVD厚膜金刚石刀具的超声振动切削模具钢实验

采用化学气相沉积（chemicalvapordeposition,CVD）厚膜金刚石刀具进行模具钢超声振动切削实验．首先阐述刀具的材质特点,观测其刀尖微观形貌和切削刃截面轮廓．然后搭建了适应精密／超精密加工需求的超声振动切削实验装置,其中激振机构可稳定实现频率42．0kHz、振幅峰峰值8～9μm的振动输出．通过切削无氧铜实验证明该超声振动切削装置工作有效、稳定后,选用AISI420模具钢进行切削实验,研究切削工艺条件及切削用量对加工质量的影响,得到适用于CVD厚膜金刚石刀具的切削用量选取范围,对比研究发现超声振动切削在提升加工表面质量、减少金刚石刀具磨损方面均优于常规切削．本研究可使切削模具钢时的金刚石刀具磨损VBmax由500～600μm减少至40μm,模具铜表面粗糙度Ra由0．93μm改善至0．09μm．本研究为金刚石刀具超声振动切削模具钢的实用化积累工艺经验,并探索提供可行的技术实现途径．     

Cutting tool material selection using grey complex proportional assessment method

In today’s metalworking industry, many types of materials, ranging from high carbon steel to ceramics and diamonds, are used as cutting tools. Because of the wide range of conditions and requirements, no single cutting tool material meets all the needs of machining applications. Each tool material has its own properties and characteristics that make it best for a specific machining application. While evaluating a cutting tool material for a machining operation, the applicability is dependant on having the correct combination of its physical properties. Thus, it is extensively important to select the most appropriate cutting tool material with the desired properties for enhanced machining performance. This paper considers an exhaustive list of 19 cutting tool materials whose performance are evaluated based on ten selection criteria. The grey complex proportional assessment (COPRAS-G) method is then applied to solve this cutting tool material selection problem considering grey data in the decision matrix. Synthetic single crystal and polycrystal diamonds emerge out as the best two choices. Oil quenched tool steel (AISI O2) and powder metal tool steel (AISI A11) may also be used as the suitable cutting tool materials. Sialon and sintered reaction bonded silicon nitride are the worst chosen cutting tool materials.     

Experimental investigation into the effects of nozzle position,workpiece hardness,and tool type in MQL turning of AISI 1045 steel

Minimum quantity lubrication (MQL) is a replacement for dry machining in which a minimum quantity of lubricant fluid is mixed up with compressed air and sprayed periodically on the machining area. In this research the effects of different parameters on the MQL turning of AISI 1045 steel have been investigated to evaluate the cutting force, surface roughness, and tool wear in comparison with the wet and dry machining. The research is aimed to study the effect of the MQL nozzle position, workpiece hardness and tool type on the output parameters. During MQL machining experiments, the nozzles were placed in three different arrangements relative to the tool to investigate the effect of the nozzle position. The effect of workpiece hardness and tool type were also studied experimentally for different lubrication conditions. The results indicated that the MQL system significantly increases the cutting efficiency in AISI 1045 steel machining. The experiments results have also confirmed a significant influence of the nozzle position, workpiece hardness, and tool type on the outputs. Machining with MQL is also beneficial to the environment and machine tool operator health as lubricant consumption during operation with MQL is 7-fold lower than in the conventional system.     

Comparative study of the effect of surface texturing on cutting tool in dry cutting

Recent researches in the field of dry machining have indicated that surface texture has the potential to influence tribological conditions. Researchers have studied the application of controlled surface microtextures on cutting tool surfaces to improve machining performance by changing the tribological conditions at the interfaces of tool–chip and tool–work piece. An experiment to study the performance of the microtextured high-speed steel cutting implement within the machining of steel and aluminum samples was performed. Surface textures were introduced using Rockwell hardness tester, Vickers hardness tester, and by scratching with diamond dresser on the face of single point cutting tool. Machining in dry conditions was applied on mild steel (EN3B) and aluminum (AA 6351) samples using lathe machine with microtextured and traditional cutting tool for the constant range of feed, depth of cut, and for varying range of cutting speeds. Measurement of cutting force, cutting temperature, and surface roughness of the work surfaces after machining were made. The results showed reduction in cutting forces and cutting temperature with textured tools in comparison with those of the untextured tool. Chips collected from different samples were studied under a microscope and the results showed that textures created on the tool surface by various methods exhibited variations in chip formation. Cutting tools without texture and with texture were comparatively studied and the outcomes of the experimental study are presented in this paper.     

陶瓷刀具切削304不锈钢时的磨损性能

采用Ｓｉ３Ｎ４陶瓷刀具切削Ｔｉ基陶瓷，ＹＴ１５硬质合金和高速钢四种刀具对３０４奥氏体不锈钢进行了切削试验，比较各种刀具的耐磨性能，并且用ＳＥＭ，ＥＤＸ等对刀具的磨损表面进行分析。     

Thermal aspects, material considerations and cooling strategies in cryogenic machining

 Conventional machining prolongs tool life by using cutting oils to cool the metal cutting process. Unfortunately, the cutting fluid contaminates the environment, and endangers the health of humans. Cryogenic machining offers an environmentally safe alternative to conventional machining by using liquid nitrogen, which can be naturally recycled. However, for the cryogenic machining process to be effective and economical, manufacturers must select the correct cooling approach. This paper describes our experimental study to investigate the cryogenic properties of some common cutting tool materials and five workpiece materials of industrial interest: low carbon steel, AISI 1010, high carbon steel AISI 1070, bearing steel AISI 52100, titanium alloy Ti-6Al-4V, and cast aluminum alloy A390. The paper addresses the major aspects of heat generated in metal cutting in terms of its effects on chip formation, tool wear, and on the functional integrity of the machined component. The paper then discusses the cooling strategies for cryogenic machining each material based on the thermal effects and material properties. The investigators conclude that the cooling approach must be finely adjusted for different materials to obtain the optimum effectiveness in cryogenic machining. The goal of our study is to provide a basis for designing the cryogenic machining system. Received: 25 November 1998 / Accepted: 12 February 1999     

An energy‐based damage parameter for the life prediction of AISI 304 stainless steel subjected to mean strain

Abstract

This study extends the plastic strain energy approach to predict the fatigue life of AISI 304 stainless steel. A modified energy parameter based on the stable plastic strain energy density under tension conditions is proposed to account for the mean strain and stress effects in a low cycle fatigue regime. The fatigue life curve based on the proposed energy parameter can be obtained directly by modifying the parameters in the fatigue life curve based on the stable plastic strain energy pertaining to fully reversed cyclic loading. Hence, the proposed damage parameter provides a convenient means of evaluating fatigue life on the mean strain or stress effect. The modified energy parameter can also be used to explain the combined effect of alternating and mean strain/stress on the fatigue life. In this study, the mean strain effects on the fatigue life of AISI 304 stainless steel are examined by performing fatigue tests at different mean strain levels. The experimental results indicate that the combination of an alternating strain and a mean strain strongly influences the fatigue life. Meanwhile, it is found that the change in fatigue life is sensitive to changes in the proposed damage parameter under the condition of a constant strain amplitude at various mean strain levels. A good agreement is observed between the experimental fatigue life and the fatigue life predicted by the proposed damage parameter. The damage parameter proposed by Smith et al. (1970) is also employed to quantify the mean strain effect. The results indicate that this parameter also provides a reasonable estimate of the fatigue life of AISI 304 stainless steel. However, a simple statistical analysis confirms that the proposed damage parameter provides a better prediction of the fatigue life of AISI 304 stainless steel than the SWT parameter.     

High-speed machining of martensitic stainless steel using PcBN

The performance of PcBN cutting tool during its application in the mass production of components made from AISI 440B stainless steel has been considered. The experimental tests have been performed at cutting speed ranging between 350–500 m/min at dry cutting conditions. The machining operations that have been explored included facing, turning, grooving and boring and the 3D topography of the machined surface are presented. The results show that good surface finish similar to grinding and dimensional accuracy can be achieved with PcBN tools.     

Effects of vegetable-based cutting fluids on the wear in drilling

This study focuses on both formulation of vegetable-based cutting fluids (VBCFs) and machining with these cutting fluids. For this purpose, characterizations of chemical and physical analyses of these formulated cutting fluids are carried out. In this study, performances of three VBCFs developed from crude sunflower oil, refined sunflower oil, refined canola oil and commercial semi-synthetic cutting fluid are compared in terms of tool wear, thrust force and surface roughness during drilling of AISI 304 austenitic stainless steel with HSSE tool. Experimental results show that canola-based cutting fluid gives the best performance due to its higher lubricant properties with respect to other cutting fluids at the constant cutting conditions (spindle speed of 750 rpm and feed rate of 0.1 mm/rev).     

Performance Improvement of End Milling Using Graphite as a Solid Lubricant

In any machining operation, the use of coolants is essential to dissipate heat generated during machining and hence to improve productivity, machinability, etc. However, the use of cutting fluids in machining operations may seriously degrade the quality of environment. New cutting techniques are to be investigated to alleviate the problems associated with wet machining. To overcome some of the problems, an attempt has been made to use graphite as a solid lubricant. This paper deals with an investigation on using graphite as a solid lubricant to reduce the heat generated at the milling zone. An experimental setup has been developed to direct graphite powder continuously onto the workpiece and tool interface at the required flow rate. Experimental studies have been conducted to see the effect of tool geometry (radial rake angle and nose radius) and cutting conditions (cutting speed and feed rate) on the machining responses such as cutting forces, specific energy, and surface finish in solid lubricant assisted machining using four fluted solid coated carbide end mill cutters. Results indicate that there is a considerable improvement in the performance of milling AISI 1045 steel using graphite as a solid lubricant when compared with machining using cutting fluids in terms of specific energy requirements, cutting force, and surface finish.     

Cyclic deformation behavior of austenitic Cr–Ni-steels in the VHCF regime: Part II – Microstructure-sensitive simulation

In Part I – Experimental study, the cyclic deformation behavior of two austenitic stainless steel grades (AISI 304, AISI 316 L) were experimentally investigated at low stress amplitudes in the very high cycle fatigue (VHCF) regime. The observations indicate that during VHCF the metastable austenitic stainless steel (304 grade) performs a pronounced localization of plastic deformation in shear bands followed by a deformation-induced martensitic phase transformation. The 316 grade undergoes only a very limited local plastic deformation in shear bands with almost no phase transformation. Consequently, both materials exhibit distinctly different cyclic softening and hardening characteristics during VHCF. In order to provide a more detailed knowledge about the individual deformation mechanisms and their effect on the cyclic softening and hardening behavior the experimental study is extended by microstructure-sensitive modeling and simulation. Two-dimensional (2-D) microstructures consisting of several grains are represented using the boundary element method and plastic deformation within the microstructure is considered by a mechanism-based approach. Specific mechanisms of cyclic plastic deformation in shear bands and deformation-induced martensitic phase transformation – as documented by experimental results and based on well-known model approaches – are defined and implemented into the simulation. The fatigue behavior at low stress amplitudes observed in experiments can be well represented in simulations so that the underlying model helps to understand the cyclic deformation behavior of austenitic stainless steels at low stress amplitudes in the regime of VHCF strength. In a comparative study based on the resonant behavior the effect of certain deformation mechanisms on the global cyclic softening and hardening characteristics is pointed out for both materials.     

Electrochemical methods for studying hydrogen diffusivity,permeability, and solubility in AISI 420 and AISI 430 stainless steels

Abstract

Hydrogen permeation and diffusivity were studied electrochemically at temperatures between 283 and 343 K at constant current for annealed and hardened AISI 420 and annealed AISI 430 stainless steel. Permeation rate, effective diffusivity, and solubility were calculated from these data. Annealed AISI 420 shows higher permeation rate and lower diffusivity than annealed AISI 430 stainless steel. Hardened AISI 420 has the highest permeation rate and lowest effective diffusivity. The calculation of solubility values from permeation data is in good agreement with the values obtained using a newly developed electrochemical hydrogen solubility measurement technique.

MST/1026     

TOOL WEAR MONITORING UNDER DRY AND WET MACHINING

External turning operations for steel 37 (AISI 1025) tubes were performed on a center lathe using high-speed steel tools. The workpiece was machined orthogonally using a wide range of cutting speeds for both dry and wet cutting conditions. The tool wear and the constants of the tool life equation (C, n) were studied by changing the cutting speed and the wear criterion. Comparisons between dry and wet cutting for different cutting speeds were performed, and the constants of the tool life equation were studied under different wear criterion values. The economy of dry and wet cutting was also studied under different wear criterion values. As a result of using cutting fluids, percentage increase in the constant C reached 18%, whereas percentage decrease in the constant n reached 7% at 0.9 wear criterion, which leads to a percentage increase in the tool life of about 214%.     

Role of machining defects and residual stress on the AISI 304 fatigue crack nucleation

Machining defects as rebuilt material and dislodgement were often induced by cutting of difficult to machining AISI 304 stainless steel. Their density increases with a decreasing of cutting speed. The effect of these defects on surface topography and residual stress was evaluated by roughness and X‐ray diffraction measurements coupled with numerical simulation. The role of the rebuilt material on the distribution of fatigue crack nucleation sites was investigated by scanning electron microscope examination of post fatigue samples loaded at different imposed strain amplitudes. The association of machining defects and fatigue crack nucleation sites was attributed to the contribution of additional tensile residual stresses induced by rebuilt material rather than local stress concentration. Moreover, the fatigue crack coalescence is promoted by increasing the rebuilt material density. When the machining defect density increases from 5 to 60 particles/mm², the fatigue life decreases from ?22% to ?65% with respect to the electropolished surface.     

304不锈钢管滚压成形圆锥外螺纹组织及性能研究

滚压加工螺纹可以获得更高的螺纹强度、精度,其在加工效率和环保性方面的优越性不容忽视.同时,滚压加工可以解决某些工艺方法不能解决的问题,如对特大型缸体的加工,可以达到减少机床和夹具、提高工件加工精度、缩短加工周期和节约作业面积的效果.为此,本文采用一种四滚丝轮车床滚压加工得到了304不锈钢管圆锥外螺纹.通过金相分析、扫描电镜、显微硬度计和万能试验机等手段,研究了304不锈钢管滚压成形圆锥外螺纹的组织及性能,并与传统的套丝管螺纹进行对比.研究结果表明,套丝加工的管螺纹,齿表层出现孔洞、金属组织被切断,其内部显微组织仍是原有的等轴晶,齿形不完整;而滚压加工使得螺纹表层组织细化,形成了沿螺纹齿形连续分布的纤维组织.套丝加工后304钢管螺纹硬度有所提高,但幅度不大;与套丝加工相比,滚压加工后304钢管螺纹的抗剪拉力和硬度均有大幅提高.     

Adiabatic shear fracture prediction in high-speed cutting at various negative rake angles and feeds

The critical characteristics of adiabatic shear fracture (ASF) that induce the formation of isolated segment chip in high-speed machining was further investigated. Based on the saturation limit theory, combining with the stress and deformation conditions and the modified Johnson-Cook constitutive relation, the theoretical prediction model of ASF was established. The predicted critical cutting speeds of ASF in high-speed machining of a hardened carbon steel and a stainless steel were verified through the chip morphology observations at various negative rake angles and feeds. The influences of the cutting parameters and thermal-mechanical variables on the occurrence of ASF were discussed. It was concluded that the critical cutting speed of ASF in the hardened carbon steel was higher than that in the stainless steel under a larger feed and a lower negative rake angle. The proposed prediction model of ASF could predict reasonable results in a wide cutting speed range, facilitating the engineering applications in high-speed cutting operations. The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0212-2     

Simplified MQL system for drilling AISI 304 SS using cryogenically treated drills

In machining operations, cutting fluids have been comprehensively used to improve the cutting tool life, but the issues related to manufacturing cost, environment and health call for reducing their use by possible methods. Minimum quantity lubrication (MQL) is a technique that overcomes these problems by spraying a small amount of cutting fluid (<100?ml/hr) as mist using compressed air. In this work, the basic MQL technique is used to achieve flow rates slightly higher (～880?ml/hr) than MQL using simple techniques like paint sprayer and compressor, which is more generally called reduced quantity lubrication (RQL). Another method to increase the tool life is by cryogenic treatment, which increases the hardness of the tool. Tungsten carbide drill bits were subjected to cryogenic treatment (?185 °C). Drilling studies were carried out on AISI 304 stainless steel (SS) using untreated and cryo-treated WC drill bits under RQL and conventional wet lubrication conditions. The tool wear on the treated WC drill bits with RQL was comparatively less than on the untreated ones with RQL and wet lubrication. These improvements were established through microhardness, SEM images, XRD, wear studies and surface roughness measurements comparisons.