Machining Of Stainless Steel Research Articles

Improving the efficiency of running-in for a bronze–stainless steel friction pair

In this paper, the possibility of the transfer of additives that are in the emulsion mist is shown by the example of the bronze CuSn7Zn4Pb6–stainless steel X10CrNi18-8 friction pair. The additive is first transferred on the processed surface of the part and through it–in the contact zone of the friction pair. It was established that the emulsion mist reduces the roughness of machined stainless steel surface more than three times, and the introduction of additives based on phosphate esters into the emulsion reduces the roughness by 4–4.5 times. Phosphate-based additive remains on the machined surface in significant quantities, even after 30 min working at heavy loads, reducing the instantaneous friction coefficient and the temperature of the friction zone. The mean width of profile elements of the assessed profile of bronze samples decreases by two times and their bearing length ratio decreases by four times. In this case, a decrease in the wear rate of bronze by more than 40% is ensured. This fact indicates the better running-in of the friction pair.

Effect of High-Pressure Coolant Supply on Chip-Breaking and Tool Wear in Machining of Stainless Steel

The high-pressure coolant supply cutting has attracted attention from a viewpoint of chip evacuation and tool life. In this study, the influence of high-pressure coolant supply on chip shape, cutting force and tool wear were investigated. The tests were carried out during external turning of stainless steel with cemented carbide cutting inserts. The results suggest that the length and radius of the chips got shorter with high-pressure coolant supply, especially supply pressure more than 5MPa. The cutting force was increase slightly with high-pressure coolant supply. However the thrust force was decrease. The uniform flank wear and crater wear were reduced and tool life was improved by high-pressure coolant supply.

Performance evaluation of coated carbide tool in machining of stainless steel (AISI 202) under minimum quantity lubrication (MQL)

The benefits of cutting fluids in machining are well known, but their use is accompanied by health and environment hazards. Moreover, strict environmental regulations make the manufacturers to switch over to dry turning, which is not feasible during machining of sticky material like stainless steel and Inconel etc. Therefore, the use of minimal quantities of lubricant (MQL) can be regarded as an alternative solution and a step towards green machining. In the present investigation an attempt has been made to explore the potential of MQL turning of stainless steel with coated carbide cutting tool. Turning under MQL conditions has shown superior results (in terms of flank wear and machined surface roughness) over wet and dry turning. Signal to noise (S/N) ratio as per Taguchi design revealed speed and MQL as significant parameters for minimizing flank wear and surface roughness, whereas feed can be set within range. The optimum combination of parameters are cutting speed (58 m/min), feed rate (0.06 mm/rev.) and MQL flow rate (100 mL/h) for flank wear and cutting speed (23 m/min), feed rate (0.07 mm/rev.) and MQL flow rate (150 mL/h) for surface roughness. Taguchi optimized conditions were validated through multiple response optimization using desirability function.

선삭가공의 피삭재에 따른 표면거칠기의 비교 분석

선삭작업에서 가공 여유각 변경은 가공특성을 변화시킨다. 본 연구에서는 피삭재로 기계구조용탄소강, 크롬믈리브텐 강, 스테인리스강을 선택하여 정해진 가공조건으로 재질들의 특색이 어떻게 변화하는지 나타내었다. 피삭재의 재질별 표면거 칠기를 알아보기 위하여 촉침식 표면 거칠기 측정기로 측정한 결과 인장강도가 높은 피삭재가 표면거칠기 값이 좋게 나왔다. 또한, 가공 이송속도 0.07 mm/rev와 0.10 mm/rev를 비교하였을 경우, 0.07mm/rev일 때가 재질과 관계없이 표면거칠기가 매우 좋게 나타났다. 선삭 여유각 변경에 따른 표면거칠기를 종합하여 분석하여 보면 3가지 재질 모두 0.9˚일 때 가장 좋은 거칠기 값을 보였으며 0.3˚일 때 가장 나쁜 거칠기 값을 보였다.

Cutting performance and life prediction of an Al2O3/TiC micro–nano-composite ceramic tool when machining austenitic stainless steel

The cutting performance and failure modes of an Al2O3/TiC micro–nano-composite ceramic tool in the machining of austenitic stainless steel were investigated. Orthogonal test and range analysis were employed to determine the optimal cutting parameters. The largest metal removal amount was got at the speed of 80m/min, the feed rate of 0.15mm/r and the depth of cut of 0.1mm. The wear resistance of Al2O3/TiC micro–nano-composite ceramic tool were better than that of the alumina-based ceramic tool only reinforced by micro-scale TiC particles. Failure modes of the present tool were cutting edge fracture and tool material peeling off, which mainly resulted from the subcritical crack growth in the tool. The ceramic tool life was predicted based on the dynamic fatigue behavior of the tool material. Due to the inherent fatigue behavior of ceramics, the tensile stress distributing in ceramic tool would cause cracks initiation and promote the cracks extension. The life of ceramic tool for the failure mode of breakage was closely related to the fatigue behavior of the tool material. So, the ceramic tool life could be predicted by calculating the fatigue life of tool material. The stochastic tool life well scattered in the tool life prediction interval.

Tool damage and machined-surface quality using hot-pressed sintering Ti(C7N3)/WC/TaC cermet cutting inserts for high-speed turning stainless steels

A Ti(C7N3)/WC/TaC cermet cutting tool was developed using a hot-pressed technology. A standard orthogonal array was used to investigate the cutting performance of this newly developed insert in the high-speed turning of 17-4PH martensitic and 321 austenitic stainless steels. The effects of the cutting parameters on the tool life and surface quality were analysed to examine the performance of the inserts based on Taguchi method. The mechanisms of tool damage and machined-surface generation and their relationships were also thoroughly discussed to understand the machinability of different stainless steels. The used cutting parameters are as follows: a cutting speed of 350∼400 m/min for 17-4PH steel and 300∼350 m/min for 321 steel and a feed of 0.10 mm/r and a depth of cut of 0.30∼0.35 mm, which is considered to be a notably efficient parameter for machining stainless steel. The crater wear and flank wear prevailed in the machining of 17-4PH martensitic stainless steel, whereas the flank wear was serious and edge chipping occurred in the machining of 321 austenitic stainless steel. There were some pits on the machined-surfaces of 17-4PH steel and some material side flow on the machined-surface of 321 steel, which is related with the e material properties of these two stainless steels.

Overview of Sustainability Studies of CNC Machining and LAM of Stainless Steel

Laser additive manufacturing (LAM), known also as 3D printing, is a powder bed fusion (PBF) type of additive manufacturing (AM) technology used to fabricate metal parts out of metal powder. The development of the technology from building prototype parts to functional parts has increased remarkably in 2000s. LAM of metals is promising technology that offers new opportunities to manufacturing and to resource efficiency. However, there is only few published articles about its sustainability.Aim in this study was to create supply chain model of LAM and CNC machining and create a methodology to carry out a life cycle inventory (LCI) data collection for these techniques. The methodology of the study was literature review and scenario modeling. The acquisition of raw material, production phase and transportations were used as basis of comparison. The modelled scenarios were fictitious and created for industries, like aviation and healthcare that often require swift delivery as well as customized parts.The results of this study showed that the use of LAM offers a possibility to reduce downtime in supply chains of spare parts and reduce part inventory more effectively than CNC machining. Also the gap between customers and business is possible to be shortened with LAM thus offering a possibility to reduce emissions due to less transportation. The results also indicated weight reduction possibility with LAM due to optimized part geometry which allow lesser amount of metallic powder to be used in making parts.

Near-dry electrical discharge machining of stainless steel

Near-dry electrical discharge machining (NDEDM) has characteristics of high material removal rate (MRR) and low tool wear rate (TWR). NDEDM uses the mixture of air and water as a two-phase dielectric fluid, so it does not produce toxic fumes like conventional EDM which uses hydrocarbon-based oils as the dielectric fluid. Realising all these advantages of NDEDM, it was selected to machine stainless steel. The effect of pulse current (IP), pulse-on time (Ton) and lift setting on NDEDM of stainless steel was investigated. Taguchi's technique was applied to obtain an optimal setting of the process parameters. 'The higher the better' approach was used for MRR as higher MRR is desired. The measured results and subsequent analysis revealed that IP was the only significant parameter. MRR increases with an increase in IP. Also, TWR was found to be negligible in comparison of MRR.

Experimental Study of Surface Finish During Electro-Discharge Machining of Stainless Steel

The main objective of this research is to show the influence of EDM parameters such as current intensity and depth of penetration on both the surface finish and process productivity, in order to deduce technical guidelines for selection of the optimum process conditions. A series of experimental tests about electro-discharge machining of AISI 316 stainless steel using copper electrodes were carried out. The surface roughness parameters were registered, and scanning electron microscopy (SEM) was applied to analyze the surface integrity, as well as the migration of electrode material elements to machined surface. The process productivity and surface finish were studied as a function of the current intensity employed during material removal and the overall depth of penetration on the workpiece material. It was proved that both current intensity and depth of penetration present a high influence on the surface integrity and production time during EDM of this stainless steel.

DIAGNOSTICS OF WORKPIECE SURFACE CONDITION BASED ON CUTTING TOOL VIBRATIONS DURING MACHINING

The paper presents functional relationships between surface geometry parameters, feedrate and vibrations level in the radial direction of the workpiece. Time characteristics of the acceleration of cutting tool vibration registered during C45 steel and stainless steel machining for separate axes (X, Y, Z) were presented as a function of feedrate f. During the tests surface geometric accuracy assessment was performed and 3D surface roughness parameters were determined. The Sz parameter was selected for the analysis, which was then collated with RMS vibration acceleration and feedrate f. The Sz parameter indirectly provides information on peak to valley height and is characterised by high generalising potential i.e. it is highly correlated to other surface and volume parameters of surface roughness. Test results presented in this paper may constitute a valuable source of information considering the influence of vibrations on geometric accuracy of elements for engineers designing technological processes.

Experimental Study on Hybrid Cryogenic and Plasma-Enhanced Turning of 17-4PH Stainless Steel

This article presents machinability of 17-4PH stainless steel using a hybrid technique composed of plasma-enhanced turning and cryogenic turning. First of all, using some primary experimental tests and nonlinear regression, a mathematical model was developed for surface temperature of uncut chip as a function of plasma current and cutting parameters. Then, the influence of cutting speed (Vc), feed (f), and surface temperature of uncut chip (Tsm) was studied on surface roughness (Ra), cutting force (Fz), and tool flank wear (VB). The results show that hybrid turning (HYT) is able to lower the main cutting force and tool flank wear in comparison with conventional turning. In addition, surface roughness was improved except for high level of surface temperature of uncut chip. However, hardness measurement of machined workpiece showed that HYT does not change the hardness of machined surface.

Accurate determination of the total hemispherical emittance and solar absorptance of opaque surfaces at elevated temperatures

In many applications such as solar power conversion technologies, radiative heat transfer plays a significant role in the energy balance. For accurate performance predictions of solar power conversion devices the total hemispherical emittance and solar absorptance of surfaces need to be known with high accuracy. Often times the emittance of a surface is calculated from indirect spectral bidirectional or directional-hemispherical reflection measurements at room temperature which can significantly underestimate the total hemispherical emittance. Here, we report a simple steady-state calorimetric method to directly measure the total hemispherical emittance of opaque surfaces at elevated temperatures with a maximum experimental uncertainty of 5%. The method is further expanded to directly measure the solar absorptance of the surface at elevated temperature using a solar simulator. We show experimental total hemispherical emittance and solar absoprtance results for various surfaces such as machine polished copper and stainless steel and several spectrally selective solar absorbers. We describe a methodology to characterize solar absorbers and apply it to a cermet-based spectrally selective solar absorber.

Optimization of Intervening Variables in MicroEDM of SS 316L using a Genetic Algorithm and Response-Surface Methodology

This research paper attempts to investigate the optimum values of the major intervening parameters in micro-Electric Discharge Machining (microEDM) of Stainless Steel (SS) 316L. Experiments are conducted using a 400 micrometre brass electrode. The discharge current, pulseon time and pulse-off time with three levels are selected as significant intervening parameters. The Taguchi method is initially applied to determine the optimum process parameters and the number of experiments required to model the responses. The response-surface methodology (RSM) is applied to correlate between intervening parameters, and the selected objectives to maximize the material removal rate (MRR) and to minimize the tool wear rate (TWR) in the machining of SS 316 L. The mathematical model obtained from RSM is used as a fitness function to multi-objective optimization using a genetic algorithm (GA). The results reveal that the resulting optimal intervening parameters improve the chosen objectives significantly. The confirmation results prove that the better developed mathematical model yields deviate within 5% of the experiment.

ANN and multiple regression method-based modelling of cutting forces in orthogonal machining of AISI 316L stainless steel

In this study, predictive modelling was performed for the cutting forces generated during the orthogonal turning of AISI 316L stainless steel. An artificial neural network (ANN) and a multiple regression analysis were utilised. The input parameters of the ANN model were the cutting speed, feed rate and coating type. In the model, tungsten carbide cutting tools, uncoated and with two different coatings (TiCN + Al2O3 + TiN and Al2O3), were used. The ANN predictions closest to the experimental cutting forces were obtained for the main cutting force (F c) and the feed force (F f) by 3-7-1 and 3-6-1 network architectures with a single hidden layer, respectively. While the SCG learning algorithm provided the optimal results for F c, the optimal results for F f were provided by the LM learning algorithm. A very good performance of the neural network, in terms of agreement with the experimental data, was achieved. With the developed model, the cutting forces could be precisely predicted depending on the cutting speed, feed rate and coating type. The prediction results showed that the ANN was superior to the multiple regression method in terms of prediction capability.

Binderless-cBN as Cutting Material for Ultra-Precision Machining of Stainless Steel

The ultra–precision cutting of steel materials is possible but needs modifications of machine tools or the workpiece material. One approach of actual research is the development of cutting materials that gives the opportunity for direct cutting of surfaces with ultra–precision quality. Binderless–cBN is here one of the most promising materials. The paper shows results of experimental studies with binderless–cBN as cutting material while turning stainless steel. Various investigations were carried out to determine the wear mechanisms. Furthermore, measurements are shown regarding the surface quality. The achieved results show the high potential ofbinderless–cBN as cutting material for the machining of steel.

A Study on Straightness of Deep Hole in Small-Diameter Drilling of Stainless Steel

This paper describes influence of the cutting conditions on the hole shape accuracy in deep-hole machining of stainless steel with small-diameter drill. The drilling tests were carried out by changing the step feed, the rotational speed and the feed rate in order to investigate the relationship between the straightness of the hole and the cutting conditions. As a result, it was found that the thrust force decreased with a decrease in the step feed amount and accordingly the straightness was improved. By changing the drill in incremental step from short drill length to long drill length, the straightness was improved.

High Speed Machining of Difficult-to-Machine Materials under Different Lubrication Conditions

This paper describes the applicability of air jet assisted (AJA) machining to stainless steel and titanium alloy at high cutting speeds in terms of tool wear and tool life. A specially designed tool holder with an air nozzle very close to the tool tip was prepared for turning stainless steel. From the experimental results, it was found that the application of flood coolant from the side of the end flank face leads to better result in tool life in AJA machining of stainless steel than that from the side of the side flank face. The assistance of air jet can improve the tool life of the M35 CVD coated insert in machining of the stainless steel by 36 to 100% under the optimal conditions in comparison with wet machining. It was also found that the air jet assistance extended the tool life of the S10 PVD coated insert by 48% in turning titanium alloy. The tool life extension of the coated insert in AJA machining titanium alloy is much longer than that of an uncoated carbide insert.

Study on the Welding of Feeder Hopper and Cylinder Instead of Casting Process

According to the specific structure of the hopper and cylinder of twin screw cone feeder machine, 16MnR and austenitic hopper and machine cylinder and stainless steel 1Cr18Ni9 are used for construction by welding process instead of cast steel ZG310-570 galvanized originally. The weld technology process is formulated. In the process of implementation of the program, the difficulties of the process as follows are solved: Selection the alternative materials; rational design of cooling water structures; form and position tolerances between double cone screw and inner sphere – conical surface, reduction of the difficulty of processing the double cone cambered, welding deformation control, post - weld heat treatment of removal residual stresses.

Chip Morphology Investigation among Dry, Wet and Gas Cooled Machining of Super Duplex Stainless Steel

In this paper, a detailed comparison between dry, wet and gas-cooled turning has been presented based on experimental study. Machining of super duplex stainless steel is considered. Cutting tool considered in this paper is uncoated carbide tool. It was observed that gas cooled machining provides a better machining performance while compared with the dry and the wet machining. Gas cooled machining is particularly needed in case of high speed machining and hard turning. In this study we investigated the chip morphology for various condition of machining and concludes that gas cooled machining is suitable for machining at higher production rate..

Multi-objective optimization and bio-inspired methods applied to machinability of stainless steel

Nowadays, due to the growing needs of market, the simultaneous optimization of various responses is configured as a necessary strategy in real process. Machinability of stainless steel has always been considered a difficult task and any movement toward optimization of this process are really worthy. Traditionally, the treatment of this problem is done through the application of the desirability function that consists in transforming the original multi-response problem in a similar with one objective. In spite of various applications involving this methodology, the quality of the solution obtained is dependent on the choice of the inferior and superior limits and on goals for each one of the responses. To overcome this disadvantage, the present work proposes a methodology to solve the original multi-objective problem by using the Bio-inspired Optimization Methods (BiOM). The strategy proposed consists in the extension of the BiOM to problems with multiple objectives, through the incorporation of two operators into the original algorithm: (i) the rank ordering, and (ii) the crowding distance. The proposed algorithm is applied to the machinability of stainless steel AISI (ABNT) 420 using a model that considers the tool life and cutting forces responses in terms of cutting speed, feed per tooth and axial depth of cut, in end milling process. The effects of these variables in the responses were investigated crossing information contained in response surfaces of material removal rate and cutting forces. The results obtained showed that the methodology used represents an interesting approach to the treatment of the optimization problem formulated.