Metalworking Industry Research Articles

Effect of Cr Plating and Plasma Nitriding on Hardness and Corrosion Resistance of H13 Steel

H13 steel has been widely used in several metal working industries. Plasma nitriding is employed for improving surface hardness, but it significantly decreases corrosion resistance of H13 steel. To improve corrosion resistance, Cr plating before and after plasma nitriding is studied in the research. Surface characterization, phase analysis, hardness and corrosion test were done to evaluate the appropriate method to improve corrosion resistance. It was found that Cr plating after plasma nitriding can improve the corrosion resistance close to as-heat treated sample. The formation of Cr can increase the corrosion potential to-310.66 mV(Ag-AgCl) comparing to-349.54 mV(Ag-AgCl) of as-heat treated sample. For the corrosion resistance at constant applied voltage tested by potentiostatic technique, the sample with plasma nitriding prior to Cr plating shows the lowest corrosion current which implies the lowest corrosion rate. For the process in which Cr plating is applied before plasma nitriding, CrN layer can be formed on the surface, but this layer is very thin (about 100 nm thick). This thin layer retards nitrogen diffusion; hence, nitrided layer beneath CrN layer cannot be formed. With only thin layer of CrN, both corrosion resistance and micro-scale surface hardness cannot be improved.

Planejamento experimental no estudo eletroquímico de camadas de óxido de nióbio em liga de alumínio 3003

A cromagem é uma opção que a indústria de metal mecânica tem encontrado para aumentar a resistência à corrosão de peças metálicas, porém esse revestimento apresenta a desvantagem de ser tóxico ao ser humano e ao meio ambiente. Para se alcançar um novo tratamento de superfície, pode-se aplicar planejamento experimental, a fim de otimizar os experimentos, principalmente quando há diversas variáveis para se chegar ao processo ou produto final. O objetivo principal deste trabalho é utilizar planejamento experimental para se obter um revestimento cerâmico à base de óxido de nióbio para ligas de alumínio 3003 e compará-lo ao revestimento de Cr (III), no mesmo substrato metálico. As técnicas empregadas foram polarização potenciodinâmica anódica, espectroscopia de impedância eletroquímica, microscopia eletrônica de varredura e mapeamento por espectroscopia de energia dispersiva. Utilizou-se um planejamento experimental 2³, no qual as variáveis foram velocidade de imersão, tempo de repouso após imersão e emersão na solução sol-gel à base de óxido de nióbio (razões molares n/n ácido cítrico/etilenoglicol 1:4, ácido e o complexo amoniacal de nióbio 10:1). Registrou-se uma tendência nas superfícies de respostas estudadas, sugerindo que em 5 min de imersão e emersão e na velocidade de 18 cm/min, o filme gerado apresenta uma maior resistência à corrosão. Os resultados de impedância eletroquímica e polarização potenciodinâmica anódica mostraram que o filme de óxido de nióbio apresenta maior resistência à corrosão que o revestimento utilizado industrialmente. Sendo assim, esse novo tratamento de superfície torna-se uma opção de substituição do revestimento a base de Cr (III).

0106 Reduction of occupational accidents: Evidence based prevention and the Prevention Index (PI-TOP)

ObjectivesPrevention Index (PI-TOP) is a practical measurement tool which is currently used to monitor injury prevention activities at workplaces. This 12-item scoring system has 3 subscales rating technical, organisational and...

Simple Virtual Reality Skill Training System for Manual Arc Welding

Although many metal work welding processes have been robotized recently, manual welding is indispensable in custom-made and high-mix low-volume productions. Hence, skilled welders are needed widely in the metal work industry. On the other hand, many people have little incentive to become a new welder because of the high physical risk and heavy demands of skills training. Virtual Reality (VR) technology may provide an effective solution, and various complex high-tech VR systems for training have been proposed so far. However, high tech VR training systems may not be required as long as the skill to be acquired is analyzed, and its tasks are confined. In this paper, a simple VR training system for steady state electrode manipulation skills in manual arc welding is proposed that uses neither force display nor mixed reality, and its effectiveness is verified. Good correlation is found between skills learned via VR welding and in actual welding in experimental tasks. Consequently, the proposed system can train novice welders safely.

STL-less based CAD/CAM Approach for Laser Scanning in Micro Stereo Lithography

Micro Stereo Lithography (MSL) is an additive rapid prototyping process for fabrication of three dimensional micro parts that requires slicing of 3D model into layers and generation of laser tool path for each of the layer. To generate laser scan path, existing general purpose CAD/CAM software is being used in microstereolithography (MSL) set up built in house to fabricate micro parts. CAD/CAM software are used as aids for generating NC tool path for machining in metal working industries. Rapid Prototyping require specialized CAD/CAM packages to generate laser tool path for macro sized components. Most of the existing rapid prototyping softwares utilize STL format files for slicing and generation of tool path. This paper describes about adapting the standard CAD/CAM package and utilizing its features for generating laser tool path for manufacture of 3D miniature parts using MSL. This approach has reduced the overall time required for product development.

仮想環境による手溶接作業の高効率技能訓練

Manual welding continues to be an indispensable skill in custom fabrication and high-mix low-volume production. Hence, skilled welders are needed throughout the metal working industry. On the other hand, many people have little inducement to enter the field because of high physical risk and the demanding training required. Virtual reality technology may provide an effective solution, and several VR systems have been proposed for welding training. Such VR simulations offer the possibility of safe and highly efficient training. This paper deals with a high efficiency training method for manual arc welding, which employs a simulation of a simplified, idealized welding situation. In the proposed method, trainees are presented with an idealized, easy-to-weld situation in the beginning stage of training, and the welding challenges gradually become more difficult and realistic in the following stages. Experimental results show the proposed training method can reduce the fatigue reported by trainees.

Bosnia and Herzegovina's metalworking industry companies barriers to export to EU market

Export of products and services on EU market can bring great benefits, but also sets requirements to companies which are not easy to meet. Metal processing industry today is the main exporter in Bosnia and Herzegovina (BIH). However value of import significantly exceeds value of the export. Therefore, there is a need to increase export to EU market. The aim of this paper is an empirical examination of the export possibilities to EU market, conducted on a sample of 24 metal complex companies in BIH. Obtained results indicate that adequate marketing strategy is a minor influential factor for export to EU market. Also the research shows that a significant number of companies is not familiar with new approach directives, as well as with procedures for conformity assessment. Most of the surveyed companies have an opinion that there is not enough number of adequate laboratories and institutions for export assistance. Also, the lack of capital for export financing in the companies as export barrier is significant. This topic should be further researched, as it is very important for companies' growth and development in BIH.

Occupational and Environmental Exposures Associated with Testicular Germ Cell Tumours: Systematic Review of Prenatal and Life-Long Exposures

BackgroundTesticular germ cell tumours (TGCT) are the most common cancers in men aged between 15 and 44 years and the incidence has increased steeply over the past 30 years. The rapid increase in the incidence, the spatial variation and the evolution of incidence in migrants suggest that environmental risk factors play a role in TGCT aetiology. The purpose of our review is to summarise the current state of knowledge on occupational and environmental factors thought to be associated with TGCT.MethodsA systematic literature search of PubMed. All selected articles were quality appraised by two independent researchers using the ‘Newcastle-Ottawa Quality Assessment Scale’.ResultsAfter exclusion of duplicate reports, 72 relevant articles were selected; 65 assessed exposure in adulthood, 7 assessed parental exposures and 2 assessed both. Associations with occupation was reported for agricultural workers, construction workers, firemen, policemen, military personnel, as well as workers in paper, plastic or metal industries. Electromagnetic fields, PCBs and pesticides were also suggested. However, results were inconsistent and studies showing positive associations tended to had lower quality ranking using the assessment scale (p=0.02).DiscussionCurrent evidence does not allow concluding on existence of any clear association between TGCT and adulthood occupational or environmental exposure. The limitations of the studies may partly explain the inconsistencies observed. The lack of association with adulthood exposure is in line with current hypotheses supporting the prenatal origin of TGCT. Future research should focus on prenatal or early life exposure, as well as combined effect of prenatal and later life exposure. National and international collaborative studies should allow for more adequately powered epidemiological studies. More sophisticated methods for assessing exposure as well as evaluating gene–environment interactions will be necessary to establish clear conclusion.

Influence of Cutting Tool Material on the Surface Roughness of AlMgSi Aluminium Alloy

Milling is one of the most universal operations in machining processes because it can remove the redundant part of material efficiently, and moreover, it can produce almost all kinds of contour surfaces with a high quality finish. Surface roughness plays an important role in determining the product quality since it strongly influences the performance of mechanical parts as well as production cost. Many types of cutting materials are used as tool materials in today's metalworking industry. Selecting the proper cutting tool material for a specific machining application can provide substantial advantages including increased productivity, improved quality and ultimately reduced costs. This article is aimed at determining the influence of different tool materials on surface roughness of AlMgSi aluminium alloy after side milling with using of the analysis of variance (ANOVA).

Health Effects from Occupational Exposure to Metalworking Fluid Mist

Metalworking fluids (MWFs) are an essential part of a technological process. They are used in machining operations for enhancing cutting process performance. The performance of MWFs depends on properties such as specific heat, viscosity, density and thermal conductivity. MWFs are used to cool and lubricate the cutting zone, flush away chips and inhibit corrosion during machining operations. On the other hand, MWFs are associated with formation of liquid aerosols (mists) that represents two types of occupational risk factors for machine operators - chemical and biological. Epidemiological assessments with machine operators in the metalworking industry have identified dermatologic and respiratory effects. The aim of this article is to review what is known about health effects from inhalation exposure to mist from various types of MWFs.

Acute hydrofluoric acid exposure reported to Taiwan Poison Control Center, 1991–2010

Hydrofluoric acid (HF) is a dangerous chemical that can cause severe cutaneous burns as well as possible systemic toxicity. We retrospectively analyzed all human HF exposure cases reported to the National Poison Control Center of Taiwan between 1991 and 2010. In this 20-year survey, 324 calls were identified, with a majority of dermal exposure (84%). Occupational exposure accounted for 80% of all cases, with workers in semiconductor industry (61%), cleaning industry (15%), chemical or metal industry (13%), and other industries (11%). Electrolyte imbalances were uncommon, hypocalcemia, hypomagnesemia, and hypokalemia were recorded in 8.6%, 1.2%, and 1.5% of all cases, respectively. Most cases (64%) of dermal exposure received antidotal treatment. Treatment modalities of dermal exposure included calcium gluconate soaking, 49.8%; intravenous calcium, 20.6%; and topical use of calcium gluconate gel, 13.9%. Twenty patients (7%) received surgery. Following HF exposure, the majority of patients presented with mild (56.5%) or moderate (36.7%) toxic effects. However, four patients were severely intoxicated; two patients died of HF-related dysrhythmia and shock. Significant symptomology may occur following HF exposure, and most of the HF exposure required hospitals evaluation. Calcium gluconate soaks appear to be effective in reducing local pain and tissue damage. Hyperkalemia should not be overemphasized as a common finding in HF exposure, hypokalemia tends to occur in cases of severe HF poisoning.

Minimising makespan heuristics for scheduling a single batch machine processing machine with non-identical job sizes

In this paper, the problem of minimising maximum completion time on a single batch processing machine is studied. A batch processing is performed on a machine which can simultaneously process several jobs as a batch. The processing time of a batch is determined by the longest processing time of jobs in the batch. The batch processing machine problem is encountered in many manufacturing systems such as burn-in operations in the semiconductor industry and heat treatment operations in the metalworking industries. Heuristics are developed by iterative decomposition of a mixed integer programming model, modified from the successive knapsack problem by Ghazvini and Dupont (1998, Minimising mean flow times criteria on a single batch processing machine with non-identical jobs sizes. International Journal of Production Economics 55: 273–280) and the waste of batch clustering algorithm by Chen, Du, and Huang (2011, Scheduling a batch processing machine with non-identical job sizes: a clustering perspective. International Journal of Production Research 49 (19): 5755–5778). Experimental results show that the suggested heuristics produce high-quality solutions comparable to those of previous heuristics in a reasonable computation time.

Recent Developments in Membrane Treatment of Spent Cutting-Oils: A Review

Throughout the metal-working industry, cutting-oil emulsions are used as lubricants and coolants. However, they have to be discarded after a certain time due to losing their functional properties. Hence, they need to be treated in order to separate any oil before disposal. Conventional methods have their advantages, but none are effective enough. Therefore, membrane technology appears to be a promising alternative. The aim of this work was to study the membrane treatment of spent metal-working fluids. The main drawback of membranes is flux decline due to fouling and concentration–polarization. The complexes of cutting-oils containing membrane filtration systems demand complementary studies on issues relating to fouling control and its reduction and membrane cleaning after fouling. Important conclusions were therefore formed about achievements in the field of fouling control and membrane cleaning.

Emissivity and temperature determination on steel above the melting point

The knowledge of the temperatures of materials above the melting point is of interest in the metal working industry, e.g., in welding to observe the weld pool formation. Therefore, procedures to determine the temperature also in the liquid phase are significant and necessary. In this paper, a spectroscopic method is presented to determine the surface temperature of liquid S235. A liquid metal-pool generated by a welding process was observed during its cool-down. The resulting temperature and emissivity distributions are presented. This procedure was also adapted to a controlled short arc process and the resulting data are shown.

Makespan minimization in a job shop with a BPM using simulated annealing

A scheduling problem commonly observed in the metal working industry has been studied in this research effort. A job shop equipped with one batch processing machine (BPM) and several unit-capacity machines has been considered. Given a set of jobs, their process routes, processing requirements, and size, the objective is to schedule the jobs such that the makespan is minimized. The BPM can process a batch of jobs as long as its capacity is not exceeded. The batch processing time is equal to the longest processing job in the batch. If no batches were to be formed, the scheduling problem under study reduces to the classical job shop problem with makespan objective, which is known to be nondeterministic polynomial time-hard. A network representation of the problem using disjunctive and conjunctive arcs, and a simulated annealing (SA) algorithm are proposed to solve the problem. The solution quality and run time of SA are compared with CPLEX, a commercial solver used to solve the mathematical formulation and with four dispatching rules. Experimental study clearly highlights the advantages, in terms of solution quality and run time, of using SA to solve large-scale problems.

Machine tools and mass production in the armaments boom: Germany and the United States, 1929–44

This article anatomizes the ‘productivity race’ between Nazi Germany and the US over the period from the Great Depression to the Second World War in the metalworking industry. We present novel data that allow us to account for both the quantity of installed machine tools and their technological type. Hitherto, comparison of productive technologies has been limited to case studies and well‐worn narratives about US mass production and European‐style flexible specialization. Our data show that the two countries in fact employed similar types of machines combined in different ratios. Furthermore, neither country was locked in a rigid technological paradigm. By 1945 Germany had converged on the US both in terms of capital‐intensity and the specific technologies employed. Capital investment made a greater contribution to output growth in Germany, whereas US growth was capital‐saving. Total factor productivity growth made a substantial contribution to the armaments boom in both countries. But it was US industry, spared the war's most disruptive effects, that was in a position to take fullest advantage of the opportunities for wartime productivity growth. This adds a new element to familiar explanations for Germany's rapid catch‐up after 1945.

Electrocoagulation of Soluble Oil Wastewater: Parametric and Kinetic Study

Soluble oils (cutting oils) in aqueous solution are used extensively in the engineering and metal working industries, as coolants, metal forming fluids, and/or lubricants. Hysol-X is a general-purpose cutting oil used in 1–10% concentration in aqueous solution. This paper investigates demulsification of soluble-oil-water emulsion using electrocoagulation with aluminum electrodes. It examines the current efficiency and the pH variation of the system due to electrocoagulation and the effect of pH of the oil-water emulsion, current density, and temperature on the demulsification process. A simple first order kinetics fits the experimental data at a constant value of current density. The optimum pH and current density were found to be 6.50 and 138.8 A/m2, respectively. Apparent electrode current efficiency was found to be 115.5%. Temperature has significant effect on emulsion stability and solution pH. At a lower temperature of 20°C or a higher temperature of 60°C, the turbidity (or oil) removal is found to be very high. More than 99% oil separation is achieved in 3 h at 20°C. The residual aluminum concentration in the treated water at an initial pH 6.5 is found to be 0.001 mg/l, well below the statutory discharge standard value.

Evaluation of Waste Process Grease as Feedstock for Biodiesel Production

Awareness of the depletion of fossil energy reserves, the rising demand for energy in the world and the problems associated with the burning of fossil fuel encourage researchers to find alternative energy sources, such as biodiesel. The use of inedible and waste oils as feedstock for biodiesel production is an important way of converting waste into valuable energy products. In this study, waste process grease (WPG) was used to produce biodiesel via two processing routes. The traditional two-step alkaline catalyzed transesterification method (route 1) produced biodiesel that did not conform to the SANS1935 biodiesel standard of South Africa with regard to sulfur and phosphorous levels. The WPG in the second process route was modified by saponification with aqueous sodium hydroxide followed by acidulation with hydrochloric acid to be purified by means of column chromatography. A hydrophobic resin with methanol as the mobile phase was used to reduce the non-polar sulfur from the grease. The crude biodiesel produced by means of acid esterification using sulfuric acid as catalyst was purified using silica gel with hexane as the mobile phase. The sulfur level in the biodiesel was reduced to a low enough level to conform to the SANS1935 standard for biodiesel production. It was shown with this study that waste process grease from the metal working industry can be used to produce biodiesel that conforms to the SANS 1935 specification for sulfur and is suitable to be used in biodiesel blending. A preliminary economic assessment shows that owed to the complexity of the second process route, biodiesel produced by this process is not economically viable given the current petroleum diesel prices. With the rising trend in crude oil prices and the limited supply of feedstock for biodiesel, WPG is anticipated to become a viable feedstock for biodiesel production in future.

Association between the high risk occupations and bladder cancer in Iran: A case-control study

The objective of this work was to identify the high-risk occupations in Iran and to re-inspect occupations that were related to bladder cancer. In the study, 300 patients suffering from bladder cancer and 500 control individuals were interviewed. Demographic information, occupational history, and history of exposure to chemical compounds such as aromatic amines for each participant were collected. ORs and 95% CIs were calculated using unconditional logistic regression for each occupation. There was a significantly increased risk of bladder cancer among truck and bus drivers (OR = 11.3), skilled agricultural, forestry and fishery workers (OR = 6.0), metal industry workers (OR = 6.0), domestic housekeepers (OR = 5.9), and construction workers (OR = 3.8). The study showed a strong correlation between truck and bus drivers, skilled agricultural, forestry and fishery workers, metal industry workers, domestic housekeepers, as well as construction workers and the increased risk of bladder cancer in these occupations.

Tool – Solid Lubricant – Workpiece Interactions in High Temperatures Applications

Tribological research concerning sliding contacts operating at elevated temperatures has received very limited attention so far, despite its importance for reliable, safe and efficient operation of many tribological systems. Typical examples can be found in aerospace, power generation and metal working industry. Considerable differences induced by higher temperatures, when compared to lower temperature applications, are the increased rate of desired (tribochemical, oxidative) and undesired (adhesive, corrosive) reactions and changes in mechanical properties. The control of friction at the tool-workpiece interface and minimisation of tool wear is crucial to ensure the quality of formed parts. This can be achieved by spraying solid lubricant onto the surface of heated tools. The efficiency of high temperature industrial processes is strongly linked with the structure and thickness of the formed layer of oxides or/and applied solid lubricant onto the tools.The objective of this study is to verify the reliability of well-designed High Temperature Disc-on-Disc-Tribometer (HT-RRV) tests for providing accelerated data for friction and wear characterisation of several solid lubricants under forming conditions. Performed laboratory tests show that this test methodology can be used to carry out parametric studies with the aim to understand the tool – solid lubricant – workpiece interactions in high temperatures applications. The application of solid lubricant greatly changes the tribological performance by reducing the coefficient of friction, and adhesive and abrasive wear phenomena. Due to the in-situ formation in the tribocontact of a sacrificial layer, which is constantly formed and removed, the surface of the tool remains mostly unaffected in terms of damage.