Two-dimensional vibration-assisted magnetic abrasive finishing of stainless steel SUS304

Traditional magnetic abrasive finishing (MAF) involves unidirectional polishing of surface but suffers the drawback of forming deep scratches, resulting in poor surface quality. This study attempts to enhance the polishing efficiency of MAF by adding vibration to the platform, focusing on the fabrication of the two-dimensional vibration-assisted MAF (2D VAMAF) setup. Experiments are conducted with variations in parameter levels of 2D VAMAF. Comparison of finished surface results shows superiority of 2D VAMAF in obtaining lower surface roughness and mirror surface quality. In addition, this study uses the Taguchi experimental design method to obtain the optimal parameter combination of 2D VAMAF for surface roughness improvement. The optimal combination obtained includes working gap (1 mm) and weight of SiC, steel particles, and machining fluid (1 g, 1.5 g and 3 g, respectively); frequency of vibration along X and Y directions (16.67 Hz); rotational speed of magnet (500 rpm); and size of SiC and steel particles (8000 and #120, respectively). With 5-min 2D VAMAF under optimal parameter combination, the surface roughness of a stainless steel SUS304 workpiece can be reduced from 0.13 to 0.03 μm, an improvement of 77 %. Experimental results reveal that 2D VAMAF can indeed improve surface quality with a shorter processing time and a smaller amount of abrasives required, both of which contribute to cost reduction. With less pollution incurred, 2D VAMAF is a more environmental friendly machining method in industry.     

Fretting properties of SUS304 stainless steel in a vacuum environment

In this paper the effect of the ambient pressure on the friction and wear of SUS304 stainless steel during fretting at room temperature is described.

The ambient pressure was varied from 10⁻³ to 10⁵ Pa. The experiment was carried out under the following conditions: normal load, 14 N; slip amplitudes, 35 and 110 μm; frequency, 8.3 Hz; number of fretting cycles, 6 × 10⁴.

The relationship between the frictional behaviour and the number of cycles is affected by the pressure. The coefficient of friction at steady state increases with a decrease in the pressure to below 10 Pa. From the point of view of the wear mechanism, the transition is determined as that from oxidative wear at the higher pressure to adhesive wear at the lower pressure. The transition pressure depends on the slip amplitude, i.e.it is 2.7 Pa at 35 μm and 10⁻¹ Pa at 110 μm. The wear volume is greater in the oxidative wear regime than in the adhesive wear regime. Oxide wear debris is removed easily from the interface in the former regime. In contrast, metallic wear debris is retained at the interface and adhesive transfer occurs from one surface to the opposing surface in the latter regime. The characteristic feature of the wear damage at 10⁻³ Pa and at 35 μm is the formation of a vertical crack at the boundary between the fretted and the unfretted areas.     

Fretting fatigue behavior of SUS304 stainless steel under pressurized hot water

Fretting fatigue behavior of the sensitized SUS304 stainless steel under a pressurized hot water at 7.3 MPa and 288 °C was investigated. The tests were carried out under a contact pressure of 100 MPa and a frequency of 20 Hz. From the experimental result, combined effect of pressurized hot water and localized high tangential stress due to fretting resulted in nucleation of intergranular crack along the outer edge of contact region at lower stress amplitudes, while a fretting fatigue crack was nucleated at the highest tangential force point independently from these intergranular cracks at higher stress amplitudes. No intergranular crack nucleation was observed for fretting fatigue at the same temperature in air. The higher stress ratio reduced the fatigue strength, where the crack tip was exposed more in corrosive environment due to the high mean stress compared to the lower stress ratio.     

Laser shock forming of SUS304 stainless steel sheet with elliptical spot

A novel forming method by laser shock wave with elliptical spot is reported. The mechanism of laser shock forming (LSF) and equation of pressure pulse were presented, and SUS304 stainless steel with a thickness of 0.4?mm was experimentally investigated. Firstly, the deformed specimen was measured by ARGUS optical measuring system, and the results of major and minor strain and material thickness reduction of sheet metal to analyze the deformation qualities were provided. Secondly, the major and minor strains were imported into forming limit diagram (FLD) to evaluate the forming parameters. The result clearly shows that all measurement points are below the forming limit curves of the SUS304 steel. Finally, the thickness reduction along long-axis direction was simulated and analyzed by using ABAQUS finite element (FE) software. The simulated results are basically in agreement with the experiment data.     

The optimal cutting-parameter selection of heavy cutting process in side milling for SUS304 stainless steel

This paper presents an optimal cutting-parameter design of heavy cutting in side milling for SUS304 stainless steel. The orthogonal array with grey-fuzzy logics isapplied to optimize the side milling process with multiple performance characteristics. A grey-fuzzy reasoning grade obtained from the grey-fuzzylogics analysis is used as a performance index to determine the optimal cutting parameters. The selected cutting parameters are spindle speed, feed per tooth,axial depth of cut and radial depth of cut, while the considered performance characteristics are tool life and metal removal rate. The results ofconfirmation experiments reveal that grey-fuzzy logics can effectively acquire an optimal combination of the cutting parameters. Hence, performance in theside milling process for heavy cutting can be significantly improved through this approach.     

A comparative experimental investigation of deep-hole micro-EDM drilling capability for cemented carbide (WC-Co) against austenitic stainless steel (SUS 304)

Microelectro-discharge machining (micro-EDM) has become a widely accepted non-traditional material removal process for machining difficult-to-cut but conductive materials effectively and economically. The present study aims to investigate the feasibility of machining deep microholes in two difficult-to-cut materials: cemented carbide (WC-Co) and austenitic stainless steel (SUS 304) using the micro-EDM drilling. The effect of discharge energy and electro-thermal material properties on the performance of the two work materials during the micro-EDM drilling has also been investigated. The micro-EDM drilling performance of two materials has been assessed based on the quality and accuracy of the produced microholes, machining stability, material removal rate (MRR), and electrode wear ratio. The results show that deep-hole micro-EDM drilling is technically more feasible in WC-Co as it offers microholes with smooth and burr-free surfaces at the rim in addition to improved circularity and lower overcut than those provided by SUS 304. Moreover, WC-Co exhibits better machinability during the deep-hole micro-EDM drilling, providing relatively higher MRR and stable machining.     

Thermal modeling of friction stir welding of stainless steel 304L

This paper presents a numerical model, based on the displacement of one point of the material flow relative to a fixed reference point, in order to formulate the heat generation during friction stir process and thereby calculate the temperature difference between advancing and retreating sides. This model considers frictional heating dependent on both the temperature and the velocity of the tool, as well as heat generation due to plastic deformation dependent on temperature, and assumes that friction heat at high temperature was replaced by heat generation due to plastic deformation. The heat generated by plastic strain energy dissipation in thermomechanically affected zone is calculated by a new technique, and the convection heat transfer coefficient and the sticking state parameter are considered as a function of temperature. Finally, the thermal equations are solved using a nonlinear finite element code ABAQUS. The numerical results correctly showed the asymmetric nature of temperature distributed at different sides of the weld line which have good agreement with experimental data that are presented in the literature.     

Study on the protective effect of built-up layer in dry cutting of stainless steel SUS304

This work presents a systematic and comprehensive investigation of the protective effect of built-up layer (BUL) in dry cutting of stainless steel SUS304. A detailed examination of BUL and built-up edge (BUE) formation conditions, their formation mechanisms, and their protective effect was carried out at different cutting speeds (5–140 m/min), and different feed rates (0.02–0.1 mm/rev). The uncoated cemented carbide tool was used as a cutting tool. The dimensions of BUL/BUE and tool wear were measured by scanning electron microscope (SEM) and laser confocal microscopy (LCM). The protective effect of BUL/BUE was characterized using flank wear progression, as well as crater wear progression, cutting force analysis, and surface roughness analysis. As a result, it was found that BUE forms around the cutting edge at low cutting speeds (5–20 m/min), and BUL, which resembles a water drop, forms on the tool rake face at cutting speeds equal to or above 40 m/min. And a thin layer of flank built-up (FBU) can form on the tool flank face as the cutting speed increases from 40 m/min to 140 m/min. The BUL/BUE formation mechanism was also confirmed. It was revealed that BUL can be considered as a protective layer, which can not only prevent the tool rake face from wear but also decrease the tool flank wear, but BUE can only prevent the crater wear; and to a certain extent, the thin layer of FBU can also work as a protecting layer on the worn tool flank face in dry cutting of SUS304. It was also revealed that the height of BUL plays a very important role in its protective effect. Meanwhile, it was found that BUL and the thin layer of FBU have no or few influences on the amplitude variation of cutting forces and on the surface roughness. These results indicated that BUL can be used to realize the self-protective tool (SPT) in cutting of difficult-to-cut material such as SUS034. In addition, the research also proved that it is necessary to take the influences of BUL, BUE, and FBU formations on tool wear into account in the tool wear model in order to achieve high-precision prediction.     

Mechanical and metallurgical properties of friction welded AISI 304 austenitic stainless steel

Owing to the superior properties, of stainless steel it is pertinent to make use of it in various automotive, aerospace, nuclear, chemical and cryogenic applications. It is observed that a wide range of dissimilar materials can be easily integrated by solid phase bonding techniques, such as friction welding and explosive bonding. This study mainly focuses on friction welding of AISI 304 austenitic stainless steel. The friction processed joints are evaluated for their integrity and quality aspects. Friction welding of austenitic stainless steel was carried out using a KUKA friction welding machine (Germany). As the friction time increased, the fully plastically deformed zone (region I) in the vicinity of the bond line becomes increased. In contrast, an increase in friction time will decrease the region (region II) where the grains are partly deformed and grown. Tensile test results indicated that, the joint strength is decreased with an increase of the friction time. The detailed fractographic observation confirmed that the rupture occurred mostly at the joint zone and partly through the base material.     

Mechanical and metallurgical properties of friction welded AISI 304 austenitic stainless steel

Owing to the superior properties, of stainless steel it is pertinent to make use of it in various automotive, aerospace, nuclear, chemical and cryogenic applications. It is observed that a wide range of dissimilar materials can be easily integrated by solid phase bonding techniques, such as friction welding and explosive bonding. This study mainly focuses on friction welding of AISI 304 austenitic stainless steel. The friction processed joints are evaluated for their integrity and quality aspects. Friction welding of austenitic stainless steel was carried out using a KUKA friction welding machine (Germany). As the friction time increased, the fully plastically deformed zone (region I) in the vicinity of the bond line becomes increased. In contrast, an increase in friction time will decrease the region (region II) where the grains are partly deformed and grown. Tensile test results indicated that, the joint strength is decreased with an increase of the friction time. The detailed fractographic observation confirmed that the rupture occurred mostly at the joint zone and partly through the base material.     

Mechanism of reduction of fretting fatigue limit caused by hydrogen gas in SUS304 austenitic stainless steel

The fretting fatigue strength of pre-strained SUS304 is reduced in hydrogen gas. The mechanism of the reduction is discussed. In hydrogen gas, local adhesion between contacting surfaces occurred and many small cracks were formed at the adhered spots. The major crack propagated from one of the small cracks. The roles of the adhesion in relation to the initiation and propagation of the small cracks were examined by a two-step environment test. When adhesion was prevented by an oxidized film, no failure of the specimen occurred. It can be presumed that the stress conditions were more severe in hydrogen gas than that in air due to local adhesion.     

Erosion of 304 stainless steel

Erosion rate measurements and scanning electron microscopy observations were made for the steady state erosion of 304 stainless steel eroded by sharp alumina particles. Both the velocity and the particle size dependence of the erosion rates were similar at all angles of impact between 10° and 90°. Micrographic observations of the steady state erosion surfaces disclosed similar overall features at low and high angles of impact. Results reported in the literature for aluminum tend to confirm these observations. It was concluded that a single erosion mechanism can be operative at all impact angles 7in ductile metals such as stainless steel, rather than a superposition of different mechanisms for the low angle and high angle range. The physical basis for a single mechanism of erosion by sharp particles was discussed.     

Manufacturing process of bezel frame for strength-reinforced TFT LCD module by progressive hemming of SUS304 stainless steel sheet

In this study, the design procedure for a progressive multi-hemming forming process has been proposed for manufacturing bezel frames for strength-reinforced TFT LCD (Thin-film-transistor liquid-crystal display) modules. First, a strength analysis was performed using Finite element (FE) simulations to determine the minimum number of required folding edges. Subsequently, anoother FE analysis was carried out in order to investigate the effects of the process parameters on the dimensional accuracy of the bezel frame and to design the progressive hemming process. The analytical results were validated by hemming experiments performed using SUS304 stainless steel with a thickness of 0.3 mm. Finally, the quality of the bezel frame was estimated through measurements of its dimensional accuracy and bending stiffness. From the experimental results, it was confirmed that a bezel frame with a height distribution of 1.5±0.05 mm and a respectable bending stiffness of 70 N/mm could be manufactured using the proposed process.     

Evolution of friction-induced microstructure of SUS 304 meta-stable austenitic stainless steel and its influence on wear behavior

The microstructure evolution of the worn surface and sub-surface layer of SUS 304 austenitic stainless steel (ASS) disc against Al₂O₃ ceramic ball were studied on the basis of the tribological behaviors in the tests performed using a Cameron-Plint TE67 pin-on-disc tester. The microstructure after friction test was observed by optical and scanning electron microscope. The possible phase transformation of meta-stable austenite to martensite was detected by X-ray diffractometer. Results showed that friction-induced deformation led to finer grain at the subsurface beneath the worn surface. Furthermore, white layer was observed on some worn surface layers after higher normal loads. Transformed martensite from the austenite appeared on the worn surface under both low and high normal-loading conditions. Absence of transformed martensite was detected at the site about 25 μm below the worn surface although the grains at the site were still intensive and fine. In addition, the specific wear rate of SUS 304 stainless steel specimens was measured, and the possible reasons affecting the wear behavior were analyzed and discussed.     

SUS304耦合摩擦实验机测控系统的研究

SUS304耦合摩擦实验机是用来模拟SUS304亚稳奥氏体不锈钢的摩擦学问题。该文分析了SUS304耦合摩擦实验机的组成,亚稳奥氏体在耦合摩擦条件下摩擦力的分析,提出了采用工业计算机和PCL-812PG多功能数据采集卡相结合的测控系统在SUS304耦合摩擦实验机中的应用。采用VC＋＋6．0作为测控系统软件的开发平台,针对PCL-812PG数据采集卡进行二次开发。试验测量结果表明：采用计算机和PCL-812PG多功能数据采集卡的控制系统,能很好地采集实验中耦合摩擦实验机的摩擦力,且与理论分析基本一致。该控制系统稳定性好,结构配置灵活,易于维护和扩展,具有较强的通用性和实用性。     

304不锈钢A-TIG焊的试验研究

主要研究在304不锈钢焊接时涂敷活性焊剂和未涂敷活性焊剂对焊缝成形的影响。试验结果表明304不锈钢采用A-TIG焊时,涂敷活性焊剂的焊缝熔深显著增加,熔宽有所减小;活性剂使熔池横截面形状发生明显变化,即焊缝上部比较宽、中下部变得很窄,这主要是由表面张力梯度的变化引起的。     

Optimization of pulsed GTA welding process parameters for the welding of AISI 304L stainless steel sheets

Optimization of pulsed gas tungsten arc welding (pulsed GTAW) process parameters was carried out to obtain optimum weld bead geometry with full penetration in welding of stainless steel (304L) sheets of 3 mm thickness. Autogenuous welding with square butt joint was employed. Design of experiments based on central composite rotatable design was employed for the development of a mathematical model correlating the important controllable pulsed GTAW process parameters like pulse current (I _p), pulse current duration (T _p), and welding speed (S) with weld bead parameters such as penetration, bead width (W), aspect ratio (AR), and weld bead area of the weld. The developed models were checked for adequacy based on ANOVA analysis and accuracy of prediction by conducting a confirmation test. Weld bead parameters predicted by the models were found to confirm observed values with high accuracy. Using these models, the main and interaction effects of pulsed GTAW process parameters on weld bead parameters were studied and discussed. Optimization of pulsed GTAW process parameters was carried out to obtain optimum bead geometry using the developed models. A quasi-Newton numerical optimization technique was used to solve the optimization problem and the results of the optimization are presented.