Steel Workpiece Research Articles

A novel magnetorheological finishing process based on three revolving flat tip tools for external cylindrical surfaces

The magnetorheological finishing technique based on a stationary curved tip tool is found less effective in finishing external cylindrical surfaces. Therefore, three revolving flat tip tools-based magnetorheological finishing process which utilises the rotation of both workpiece and tools have been developed to address the issues of the existing method. Also, a feed mechanism has been built to provide the longitudinal movement to the workpiece. A workpiece of mild steel has been finished by both developed and existing methods. It has been observed that after finishing 1 hour 30 minutes with a stationary curved tip tool, surface roughness values Ra, Rq, and Rz decrease by 69.29%, 64.41%, and 61.26%, respectively. Whereas, the reduction in the surface roughness value of Ra, Rq, and Rz by 85.38%, 84.51%, and 82.7%, respectively, have been noted after finishing with the three revolving flat tip tools process at the same parameters and conditions.

Model Based Prediction of the Heat Affected Zone in a Steel Workpiece Induced by an EDM Single Discharge

Setting a determined microstructure within the rim zone of a manufactured workpiece without cost-intensive trial and error experiments is essential to meet the increasing requirements of the industry. The most promising approach to predict the final functional properties is to simulate the microstructure evolution and to build an inverse approach of the manufacturing process. Thermal load based microstructure evolution models with an artificial initial structure and temperature gradients up to 1·106 K/s have been published in previous works presented by the authors. In this work, an existing heat transfer model was extended to predict the actual temperature gradients for a single discharge during electrical discharge machining (EDM). These calculated temperature gradients were then used to simulate the microstructure evolution of a 42CrMo4 steel. The initial structure was derived from a cross sectional SEM image. Therefore, the presented model is able to simulate the actual microstructure evolution within the heat affected zone of an EDM'ed workpiece.

Effect of laser scanning velocity on the microstructural changes and mechanical properties of the H13 steel part treated by laser surface remelting

This paper investigates the effect of laser scanning velocity on the structural changes and mechanical properties of a H13 steel part treated by laser surface remelting. A high energy density laser with a large laser beam was used to improve the processing efficiency. The room temperature phases are dominated by martensite, retained austenite, and carbides. The laser treatment effects under various exposition conditions are compared in terms of heat affected depth, surface topography, and mechanical properties. The strengthening mechanisms include grain refinement, dislocation and precipitation strengthening, which act simultaneously during the laser remelting process to confer a high hardness at the surface of the H13 steel workpiece. Due to its higher yield strength and lower elongation, failure in the remelting zone occurred at the grain boundaries of the dendrites and in between the heat affected zone (HAZ) and the parent metal (Base Metal). These results can support the mass production of surface hardened H13 steel moulds using a laser treatment (high laser density and large laser heat source) with apprehensible changes of properties.

Thermo-hydraulic analysis of melt pool dynamics and material removal on anode in electrical discharge machining

The melt pool dynamics and material removal mechanism in electrical discharge machining (EDM) is not clear yet. In this study, a thermo-hydraulic coupling simulation model considering practical boundary conditions was proposed to investigate the melt pool evolution and material removal on the anode in EDM, with the simulated results directly verified by the high-speed observation of the discharge process. Discharge currents of 5–15 A, a discharge duration of 10 µs, and workpieces of zinc and steel were used in the model, with the forces acting on the melt pool comprehensively integrated and their effects on the melt pool dynamics and material removal analyzed. The simulation results show that on the anode the evaporation recoil pressure is one of the dominant factors that drive the melt flow and cause the molten material removal. The increase of discharge current results in larger evaporation recoil pressure, and thus larger volume of the molten material is removed. Under the effect of evaporation, obvious fluctuation of the melt pool will occur. Meanwhile, the evaporation recoil pressure oscillates with the melt pool fluctuation, which may induce a wave-like motion of the molten material and promote the generation of debris particles. Novel high-speed observation methods were proposed to observe the melt pool evolution and the material removal, with the observed melt pool behavior consistent with the simulated results. The observation also shows that the intermittent removal of the molten material occurs in the case of long discharge duration, which is considered to be caused by the intermittent increase of the evaporation recoil pressure during the melt pool fluctuation.

Combination of Thermal and Mechanical Strategies to Compensate for Distortion Effects during Profile Grinding

This paper describes the investigations and the results of an analysis of distortion compensation processes for profile grinding. Steel workpieces often change their residual stress state due to machining in a seemingly uncontrolled matter. Furthermore, in research as well as in the industry, the accurate representation of shape deviations during the cutting of slim profiled workpieces and their deformation handling is a major challenge. In this paper, a valid predictive model, developed for the compensation of distortions resulting from the effect of a laser-based treatment and a deep rolling, was calibrated by experimental data. The numerical design of these strategies provided a model for predicting compensation parameters to minimize profile grinding distortions.

Experimental Research on Sheared Edge Formation in the Shear-Slitting of Grain-Oriented Electrical Steel Workpieces.

This study sought to experimentally develop guidelines for shaping 0.3-mm-thick cold-rolled grain-oriented ET 110-30LS steel using a shear-slitting operation. Coated and non-coated steel was used for the analysis. The coated sheet had a thin inorganic C-5 coating on both sides applied to the C-2 substrate. The first part of this paper presents an analysis of the quality of the cut surface depending on the adopted machining parameters, which were the control variables on the production lines. The second part presents an analysis of the magnetic parameters of the cut samples, which allowed for the specific impact of the quality of the cut edge on the selected magnetic features. Finally, an optimization task was developed to obtain a set of acceptable solutions on the plane of controllable process variables such as slitting speed and horizontal clearance. The obtained results can be used to control the shear-slitting process on production lines and obtain high-quality workpieces.

ВЛИЯНИЕ СМАЗОЧНО-ОХЛАЖДАЮЩИХ ЖИДКОСТЕЙ НА ШЕРОХОВАТОСТЬ ОТВЕРСТИЙ ПРИ СВЕРЛЕНИИ ЗАГОТОВОК ИЗ НИЗКОЛЕГИРОВАННЫХ СТАЛЕЙ

The rational choice of cooling mixtures (coolant) is a complex technological task. Currently, world industries produce a wide range of such substances. At the same time, manufacturers' recommendations on their use are of a general nature, which makes it difficult to choose them for specific cases. One of the criteria for choosing a coolant is the roughness of the formed surface, especially during constrained cutting, in particular during drilling. Therefore, studies of the influence of cooling mixture on the roughness of the hole surface during drilling are relevant. The task to which the paper is devoted is to find out the dependence of the roughness of the hole surface obtained when drilling workpieces of low-alloy steel on the properties of the coolant used. To achieve this aim, experimental studies were conducted. As a result of laboratory tests of coolants, their lubricating properties and density were determined. The evaluation of the obtained roughness dependencies during drilling on the properties of coolant allowed us to define a formula for determining the predicted surface quality. It is found out that the determinant property of the coolant is its lubricating action, and the parameter for its evaluation is friction factor. The calculation formula makes it possible to predict the roughness of the hole surface when drilling low-alloy steels with an error of 11.8%. The method of coolants testing and determination of their effectiveness by the roughness parameter Raavg is presented.

A case study for a worn tool steel in the hot stamping process

A good understanding of failure mechanisms can help us improve the lifetime of the dies. This paper presents a case study investigating the wear behaviour of a QRO90 die insert utilized for stamping uncoated boron-alloyed high-strength steel sheets. Topography and microstructure were characterized by means of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), hardness measurement and X-ray photoelectron spectroscopy (XPS). Severe galling due to accumulated layers transferred from the boron-alloyed steel workpieces occurred on the die surface. Material softening was detected in the sublayer of the tool steel (up to ∼200 μm). In addition, white layers with a in a thickness of 1–2 μm were frequently observed on the surface of the round corner of the tool. The main wear mechanisms are discussed. Galling caused by surface softening and the spallation of white layers are considered to be the primary wear mechanisms for the tool.

ТЕХНОЛОГІЧНІ ОСОБЛИВОСТІ КОМБІНОВАНОГО ЛИВАРНО-ІНДУКЦІЙНОГО МЕТОДУ ОДЕРЖАННЯ ТРИШАРОВИХ ВИЛИВКІВ

The technological features of developed casting-induction method for obtaining threelayer «cast iron-steel-cast iron» castings were studied. The specified method consists in the use of induction heating of a steel billet with a high-frequency electromagnetic field in the casting process for obtaining three-layer products. The paper represents mathematical modeling results of temperature fields distribution under the action of electromagnetic fields on a steel workpiece. The main regularities of steel billet temperature changes depending from the current level and heating time have been established. As a result of simulation modeling, the technological parameters of the steel workpiece heating and cooling process were determined, as well as the pouring of the melt during the production of three-layer castings. Obtained dependences between temperature of the poured melt and temperature of the workpiece are necessary to ensure a high-quality connection between the steel inner part and working layer made of cast iron. The results of the experimental testing confirmed the adequacy of the mathematical modeling of the thermal state of the workpiece, as well as the effectiveness of using the developed combined casting-induction method for obtaining three-layer castings. Keywords: induction casting method, induction heating, simulation modeling, three-layer casting, electromagnetic field, melt.

Determining the Optimal Cutting Parameters for Required Productivity for the Case of Rough External Turning of AISI 1045 Steel with Minimal Energy Consumption

One of the most important challenges for every machining shopfloor, especially a small one, is to achieve the required productivity with minimal energy consumption and engaged power. The paper presents a way to determine the optimal combination of values of cutting parameters such as depth of cut, feed rate and cutting speed from the range of their recommended values, which are usually additionally limited by the real conditions of available machines and tools. The optimal combination is the one which ensures targeted productivity and maximum energy savings at the same time. As an example, a real practice case of external rough turning of an AISI 1045 steel workpiece is presented. The selection of the optimal combination of cutting parameter values is based on a model which is developed using in situ measurements of energy consumption and engaged power in an experiment that emulates the critical operation in terms of energy consumption. The results show that optimization of cutting parameter values that enables the minimum of total energy consumption while achieving target productivity, does not necessarily enable the maximum of energy savings for a given operation. In the example from real practice shown in the paper, this optimization approach can cause higher total energy consumption by as much as 15.9% compared to the combination of parameters that ensure maximum productivity.

Nonlinear dynamics of friction-induced regenerative chatter in internal turning with process damping forces

Stability in internal turning operation depends on several factors such as cutting conditions, tool overhang, associated tool dynamics, regeneration, friction and process damping. In the present work, an improved friction-induced regenerative chatter mechanism is introduced for internal turning operations with the help of a two-degree of freedom (DOF) cutting tool model by considering structural nonlinearities and process damping effects. The model is initially validated with the existing linear stability analysis theory via the natural parameter continuation method. The stability lobes obtained from the proposed model predict the stable regions with good accuracy. Furthermore, the nonlinear behaviour of the cutting tool with Stribeck and regenerative effects under internal resonance and primary resonance conditions is investigated. The nonlinear dynamic responses and the cutting stability are predicted using the higher-order method of multiple time scales (MMTS). The effect of nonlinearities on the frequency response and stability is studied in detail and the system parameters for stable cutting operations are identified. In order to validate the cutting states of the stability diagrams, internal turning experiments are performed on AISI 1020 carbon steel workpieces and the stability conditions are found to be in good agreement.

Formation of the Structure and Properties of Deposited Multilayer Specimens from Austenitic Steel under Various Heat Removal Conditions

The effect of side limiters (shaping blocks) on the formation of the structure and hardness of AISI 308LSi stainless steel workpieces obtained by multilayer build-up welding in an argon environment has been studied. The studies were carried out on specimens deposited using graphite limiters, copper limiters and without limiters. As a result of numerical simulation, it was found that the lowest temperatures of the specimen metal are observed when using copper limiters, and the highest when using graphite limiters (different thermal conductivity of materials) in comparison with the temperatures of the specimen obtained without limiters. With the use of graphite limiters, most of the specimen’s metal is in the temperature range of austenite formation (45%) and a more uniform growth of structural elements is observed, without sharp transitions between the deposited layers, in contrast to the other two types of specimens. The high value of the thermal conductivity of copper leads to an increase in the difference in the size of the dendrites between the central and peripheral side parts of the deposited specimen. The highest values of hardness are observed in the specimen obtained using graphite blocks, due to the more active diffusion of δ-ferrite into austenite by an average of 12%, compared with the other investigated specimens, despite the overall increase in size dendrites. The technology of electric arc multilayer build-up welding with the use of shaping graphite blocks makes it possible to produce a workpiece with a uniform structure and properties. The above makes it a promising direction in electric arc additive manufacturing.

Affecting Microstructure and Properties of Additively Manufactured AISI 316L Steel by Rotary Swaging.

The presented work focused on the development of the microstructural and mechanical properties of a AISI 316L stainless steel workpiece prepared through additive manufacturing and subsequently processed by hot rotary swaging. In order to characterize the effects of swaging on the structural development, samples were taken for electron microscopy scanning and microhardness measurements were taken after each swaging reduction. The as-built and final swaged pieces were also subjected to tensile testing at room temperature and at 900 °C. The structural analyses showed that the hot swaging introduced a substructural formation; low angle grain boundaries prevailed over high angle ones after each pass. The swaging also imparted an almost complete elimination of the porosity and significant grain size; the average grain area decreased from the original value of 365.5 µm2 to 4.4 µm2 after the final swaging pass. The changes in the texture between the passes were negligible, however, the grain refinement went hand in hand with the microhardness increase (up to almost 300 HV1). The results of the tensile testing confirmed that the mechanical properties of the swaged pieces which improved dramatically and remained favorable up to high temperatures.

Study on the working performance of CrAlCN coated and uncoated carbide twist drill

A drilling test was carried out for a 6 mm diameter carbide twist drill with CrAlCN coating and an uncoated carbide twist drill to grasp the effect of CrAlCN coating on the tool performance. Drilling and machining tests on ASTM1045 steel workpieces using CrAlCN coated and uncoated tools. Observe the pattern of variation of surface morphology and roughness of holes with the number of drilled holes using SEM and optical microscope. The effect of CrAlCN coating on carbide twist drill on drilling quality was analyzed by comparing the wear, surface roughness and chip shape of twist drill at different periods and parameters of drilling. The study concluded that using CrAlCN coated tools improved the wear resistance of the drill and significantly reduced BUE. Compared to the uncoated bit, the diameter of the drill decreased to 5.91 mm for the coated tool and 5.79 mm for the uncoated tool after 80 holes. The roughness of the coated bit was 3.324 µm at a feed rate of 0.12 mm/r and several holes of 40, which was significantly lower than that of the uncoated bit. Chip analysis showed that the coated tool maintained well-broken and tightly spiraled chips. In contrast, the uncoated tool produces tightly spiraled chips and short ribbon chips at a feed rate of 0.18 mm/rev, and the edges of the chips can appear significantly serrated. The research results improve the understanding of the drilling wear mechanism, provide new technical means to improve the analysis of working tool performance and provide a reference basis for the design of new coating tools.

Straightness Prediction in CNC Turning Process for Carbon Steel and Aluminum Workpieces Applying Artificial Neural Networks

Straightness Prediction in CNC Turning Process for Carbon Steel and Aluminum Workpieces Applying Artificial Neural Networks

Processes of Physical Treatment of Stainless Steels Obtained by Additive Manufacturing

With a vista of available stainless steel grades at our disposal, it is possible to manufacture items for a wide range of industries. These include chemicals production, medicine, and pharmacology, aerospace, power engineering, etc. Stainless steels are widely used mostly due to their unique property set, both mechanical and physicochemical ones, achieved by alloying various components. Stainless steel workpieces are usually obtained by melting, alloying, casting, and subsequent rolling to the desired shape. The experience in the study of the microstructure and processes of physical treatment of steel accumulated to the present day mainly concerns the machinability (blade, abrasive, laser, etc.) of such steels obtained by conventional techniques. Meanwhile, approaches to the production of workpieces from stainless steels by additive manufacturing (AM) methods are actively developing. In their turn, additive manufacturing technologies allow for producing workpieces that are structurally as close as possible to the final product shape. However, the use of AM workpieces in the manufacturing of functional products brings questions related to the study of the treatability of such steels by mechanical and physical processes to achieve a wide range of functional characteristics. This article discusses the issues of treatability and the characteristics and properties of stainless steels obtained by AM.

Investigation of thermal behaviour of structural steel S235N under laser cutting process: Experimental, analytical, and numerical studies

Laser cutting represents an appealing solution for high machining speed and precision in steel constructions. To control the efficiency of laser cutting, the effects of laser heating must be understood; and to investigate thermal effects on a steel workpiece, a methodological approach for analytical modeling of laser cutting heat source is proposed herein. The proposed model takes into account laser source geometry variation along the cut edge thickness. Given the complexity of the analyzed process, there is no accurate mathematical formulation capable of modelling both heat flux and temperature distribution. Therefore, to model heat flux with an accurate temperature distribution field and both calibrate and validate solid phases of a cut specimen, the paper proposes a modified heat source based on a Gaussian distribution. The study focuses on mild structural steel S235N and relevant commonly used laser cutting parameters for structural applications. More precisely, the model allows the laser cutting process to be simulated as a function of laser beam diameter, cutting speed, laser power and element thickness. Thus, to simulate the thermal process by means of a proper heat source, a model was implemented in the FE software Abaqus. Model parameters were both calibrated and validated through experimental results provided by online monitoring of laser cutting process with a thermal camera and location of microconstituents. In particular, the temperature profiles obtained from the proposed FE model, exhibit a good agreement with experimental results. Finally, the distribution of microconstituents along the depth agrees with predicted temperature profiles.

Response surface methodology based parametric study for AISI H13 die steel using customized designed 3D printed Ti64 multi-nozzle polishing tool

The work presents a study on FJP polishing of AISI H13 die steel using 3D printed multi nozzle (dual orifice) polishing tool and Silicon Carbide (SiC) abrasive slurry. It presents a simultaneous effect of feed rate and spindle rotation on the percentage change in surface roughness (%[Formula: see text]). Central Composite Design (CCD) method was used to design the experimentation plan and Analysis of Variance (ANOVA) was performed to evaluate the optimum values of the process parameters. The regression model developed for the FJP process was validated by polishing the AISI H13 workpiece with 39[Formula: see text] average initial surface roughness with the optimized process parameters; feed rate of [Formula: see text] and spindle rotation of [Formula: see text]. The optimized FJP parameters were able to generate the surface roughness of [Formula: see text]. The results obtained from the confirmatory experiments were found to be very close to the predicted results which validated the developed regression model. To further enhance the polishing efficiency, the optimum process parameters were used to polish AISI H13 die steel workpiece, the surface roughness was reduced from 390 to 110 nm in 15 min with 12 number of passes which shows the reduction in peaks and valleys with surface improvement of 71.79%.

Modeling of Deep Rolling as a Distortion Compensation Strategy during Profile Grinding

This paper analyzes the possibility to induce residual compressive stresses utilizing deep rolling in a long, slim steel workpiece that is profile ground and that resembles a linear guide rail. These intentionally caused residual compressive stresses at the side surfaces of the workpiece are intended to counteract the distortion due to residual stresses in the V-groove of the guide rail induced by grinding. A finite element model was prepared based on the initial state of the workpiece. The amount of respective stresses depended on the load intensity and duration of the process. The experimental data regarding the residual stress profiles due to the deep rolling process and the resulting workpiece distortion were used to validate the simulation, so that an adjustment or a calibration of the thermometallurgical and thermomechanical material data was possible. The key findings are the numerical design of appropriate strategies for the distortion potential induction, the experimental distortion results, knowledge on the mechanical treatment by deep rolling, and the successful modeling of the mechanical treatment and the process strategy.

Research on the Oscillation in Centerless Grinding Technology When Machining Bearing Steel.

In today’s engineering industry, technical diagnostics presents many advantages for improving the management of machining centers and automated production lines. As the fourth industrial revolution is currently being implemented, which includes machine diagnostics, the idea of adding information from the field of vibrodiagnostics was born. The vibration of the workpiece or machine tool negatively affects the geometric parameters of the machined surfaces of the workpiece. Through vibrodiagnostics, the influence of cutting parameters on the oscillation of a bearing steel workpiece during centerless grinding is investigated. The presented publication deals with the vibration of the mechanical parts of a centerless grinding machine. The oscillations are recorded by acceleration sensors, which are also placed on the support ruler in which the workpieces are guided, and the recorded data are input parameters for statistical processing of acceleration values in the form of statistical characteristics (minimum, lower quartile, median, upper quartile, maximum). In this paper, this procedure was applied for the selection of the optimum cutting parameters (for the speed of the support wheel), where the machining parameters at which the minimum oscillation values occur were selected based on the above-mentioned statistical characteristics. This optimization procedure revealed increased vibration values which reached the highest amplitude on the ruler, namely accelerations of 11 m/s2, the origin of which was subsequently detected by STFT because the occurrence of resonance events or the excitation of natural frequencies of the machine were suspected. The STFT analysis identified a resonant region at machine start-up determined by the spindle speed which excites the resonance on the machine. The speed range between 1950 and 2150 rpm, which corresponds to the built-up resonance, was provided to the technologists to ensure that the machine was not operated around this resonance region at 400 and 760 Hz until the undesired phenomenon was eliminated. The results of the individual measurements provided information on the ideal setting of the cutting parameters and the current state of the machine.