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İnsanlar gün içerisindeki faaliyetlerinin büyük bölümünü kapalı alanlarda geçirir. Bu nedenle insanlar için kapalı mahallerde iyi bir havalandırma ve iklimlendirme sistemi tasarlamak son derece kritiktir. İyi bir havalandırma, insanlarda hem vücut sağlığı hem de çalışma verimleri adına önemli bir kıstastır. Sıcaklık maruziyeti, vücudun fizyolojik ve psikolojik dengesini, çalışma verimini önemli ölçüde etkileyen ve çalışma ortamında sıkça karşılaşılan problemlerdendir. Isıl konfor ise, kişinin bulunduğu ortamın sıcaklığı ile uyumun sağlanması ve memnuniyetsizliğin bertaraf edilmesi anlamına gelmektedir. Termal konfor şartlarının tam olarak sağlanamadığı ortamlarda çalışmak zorunda kalan çalışanların verimlerinin düştüğü, güvenli çalışma durumunun zayıfladığı ve buna bağlı olarak iş kazasına maruz kalma sıklıklarının arttığı gözlemlenmiştir. Bu yüzden ısıl işlemin zorunlu olduğu, sıcaklık maruziyetinin kaynağında yok edilemediği durumlarda çalışan kişilerin termal konfor şartlarının iyileştirilmeleri öncelikle çalışanların sağlığına sonrasında ise üretim verimine olumlu katkılar sağlayacaktır. Bu çalışmada, ısıl konforu belirleyen parametreler üzerine incelemeler yapılmış olup, örnek mahal olan sıcak şekillendirme prosesi kullanılarak sac şekillendirme yapan hatta çalışan işçilerin ısıl konfor için çalışma koşulları gözlenmiştir. Isıl konforu sağlamak adına soğuk yelek üretilmiş ve ısı transferi dikkate alınarak iyileştirici faaliyetler belirlenmiştir. People spend most of their activities during the day in closed areas. Therefore, it is extremely critical to design a good ventilation and air-conditioning system in closed spaces for people. Good ventilation is an important criterion for both human health and working efficiencies. Temperature exposure is one of the most frequently encountered problems in the working environment, which significantly affects the physiological and psychological balance of the body and the working efficiency. Thermal comfort means compliance with the temperature of the person's environment and eliminating dissatisfaction. It was observed that the efficiency of the employees who had to work in the environments where the thermal comfort conditions could not be fully decreased, the safety status of the workers had weakened and the frequency of exposure to work accidents increased. Therefore, if the thermal treatment is compulsory and the temperature exposure cannot be eliminated at the source, the improvement of the thermal comfort conditions of the employees will firstly contribute to the health of the employees and then to the production efficiency. In this study, the parameters determining thermal comfort were investigated and the working conditions of the workers who worked on the sheet metal forming even by the hot forming process were observed. In order to provide thermal comfort, cold vests were produced and healing activities were determined considering heat transfer. Beyçelik

Additive manufacturing (AM) brings the possibility to produce tools with a complex design of the cooling channels to achieve desired properties in the working piece. However, AM of tool steels can be challenging due to the residual stresses and crack formation which may be mitigated by optimizing process parameters. In this study, process parameters development in the laser powder bed fusion (L-PBF) of a martensitic hot work tool steel was under investigation. Having power, scanning speed and hatch distance as variables, a design of experiment was performed to map a process window to produce dense components. In addition, the same sets of process parameters were applied at different preheating temperatures to study and discuss the effect of three preheating temperatures on the porosity, microstructure and hardness of the manufactured components. The characterization of the parts was done using optical and scanning electron microscopy, x-ray diffraction and micro-hardness test. The results showed that the martensitic hot work tool steel can be manufactured with L-PBF with high densities above 99.95%. © 2022 The Authors. Published by Elsevier B.V.

In recent years, promising technique of deep cryogenic treatment (DCT) is taking a new step in improving properties of various materials, especially steels. This study is focusing on influence of selected heat treatment process involving deep cryogenic treatment on the microstructure and microstructural evolution of four different steel grades (bearing steel 100Cr6, cold work tool steel X210Cr12, hot work tool steel X38CrMoV5-3 and stainless steel X17CrNi16-2). The study was performed for different heat treatment conditions, focused on effectiveness of DCT when using different austenitizing and tempering temperatures. The evolution of the microstructure was investigated in a sequential manner with various analytical techniques. The study indicates that the microstructure and microstructural evolution and changes are strongly related to the chemical composition of steel and the predefined matrix microstructure. DCT increases precipitation of carbides and induce their more homogenous distribution. The magnitude of increased carbide precipitation after DCT is correlated with the higher carbon content, whereas the content of other alloying elements does not scale with the precipitation behavior. The obtained results indicate that incorporation of DCT with heat treatment with higher austenitizing and lower tempering temperature is the most suitable for improving steels’ properties with DCT, due to the stronger impact of DCT on the carbide precipitation and matrix modification.

This research focuses on specimen geometry and the associated surface roughness of H13 hot-work tool steel, processed using laser-directed energy deposition additive manufacturing, and varying both the powder feed rate and the laser scanning speed. Under the examined conditions, the test sample measurements of length and width did not vary, but the sample heights were significantly affected by the scanning speed. An increase in scan speed resulted in ‘underbuilding’, while a decrease resulted in ‘overbuilding’, as might be anticipated. The top surface roughness of the samples was found to be greater than the side surface roughness, due to the capture of extra powder particles. For the single-track and multitrack clad samples, the surface roughness was increased when decreasing the scan speed. The addition of a draft angle, when producing 3-D components, was shown to reduce the side surface roughness. Using a finer layer thickness results in overbuilding the target height, while a coarser layer thickness results in underbuilding. Finally, the surface roughness exhibited no clear trend when the layer thickness was changed.

To elevate the friction and wear performances of hot work mold, CrNi coatings with the different TiO2 mass fractions were fabricated on H13 steel using laser cladding (LC). The morphologies and phases of obtained coatings were analyzed using a scanning electron microscope (SEM) and x-ray diffraction (XRD), respectively. The effects of TiO2 mass fraction on the friction and wear performances of CrNi coatings at 600 °C were investigated using a high-temperature wear tester, and the wear mechanism was also discussed. The results show that the TiO2-reinforced CrNi coatings are mainly composed of Fe0.64Ni0.36, Cr and Cr2Fe14C phases; their porosity decreases with the increase in TiO2 mass fraction. The average coefficients of friction (COFs) of CrNi-5%TiO2, -10%TiO2 and -15%TiO2 coatings are 0.77, 0.74, and 0.67, respectively, and the corresponding wear rates are 1.164 × 10−5, 0.942 × 10−5, and 0.614 × 10−5 mm3·s−1·N−1, respectively. The TiO2 plays a role of friction reduction and wear resistance, and the wear mechanism is abrasive wear and oxidation wear.

CV. Grafika Dua Tujuh is an industry engaged in publishing and printing books and student worksheets located in Klaten. The average output produced daily is 85.400 books and student worksheets, while the company has a production target of 90.000 books and student worksheets. Based on the results of interviews with workers, the level of production that is not maximal is caused by an uncomfortable working environment. Workers in the production room complained about the condition of a hot work environment so that workers feel easily tired and lack of concentration. To overcome the hot workplace, workers often go to the restroom and they work while holding the hand fan. This condition disturbed their concentration and cause work errors. If this condition is carried out continuously, there will be a lot of lost work time which can cause a decrease in productivity. This study aims to analyze the improvement of working temperature conditions in the production room of CV. Grafika Dua Tujuh. This research was conducted by directly measuring thermal conditions in the entire production room of CV. Grafika Dua Tujuh. Determination of the coordinate point of room temperature measurement is based on SNI: 16-7061-2004. Workload assessment is carried out based on SNI 7269: 2009. The results of the measurement of work climate at the content printing workstation are the values of air temperature, humidity, and wind speed i.e 33.32 °C, 39.9%, and 0 m/s. In addition, Wet Bulb Globe Temperature Index (WBGT) value is obtained which is on the verge of a limit, i.e 29.90 °C for the category of the heavy workload with an allocation of working time of 87.5%. The temperature is above the standard set by the Ministry of Health of the Republic of Indonesia No. 1405 / MENKES / 2002 which sets the temperature in an industrial room ranging from 18 °C - 28 °C. Improvement for working temperature is done by engineering control, namely the installation of a turbine ventilator or exhaust fan.

Introduction: Working in a hot work environment has a negative impact on occupational health and safety. The impact on health due to work at temperatures above a comfortable temperature can affect body temperature and blood pressure of workers. The aim of this study was to analyze the differences in body temperature and blood pressure of workers before and after exposure to hot work climates at PT. Pertamina (Persero) Tanjung Wangi. Method: This research was an observational study with cross sectional approach. The population of this study was all workers at PT. Pertamina (Persero) Tanjung Wangi., with the total of 11 people. The sample in this study was obtained by total sampling method with a sample of 11 workers. The dependent variables in this study were body temperature, blood pressure, age, fluid intake, and nutritional status, while the independent variable was work climate. Results: Most of the grass lathe workers at PT. Pertamina (Persero) Tanjung Wangi has an age between 17-25 years, some of the grass lathe workers had a fluid intake with less categories with normal nutritional status. The measurement results showed that the average ISBB value was 28.8°C, this value still exceeded TLV. In addition, the results showed that there were differences in body temperature before and after work, from 36.04° C to 36.8° C. In addition there were differences in systolic and diastolic blood pressure before work which was 112.7 mm Hg 77.3 mm Hg, and the average after work was 121 mm Hg and 83.6 mm Hg. Conclusion: There is a difference between body temperature and blood pressure before and after exposure to hot work climates.Keywords: blood pressure, body temperature, hot work climate

Company XXX is a factory that involving manufacturing of offshore containers in where the hot works are one of the crucial activities in fabrication and structuring the framework of the containers. This study had been conducted at hot work section to conduct initial and advanced ergonomic risk assessment to identify ergonomic risk factors involved among hot-work workers which cause the significant number of reports on ergonomic related health issues at hot works area from the year 2011 to year 2017. The initial and advanced ergonomic risk assessment had been conducted based on DOSH latest release of guideline on ergonomic risk assessment 2017 and all findings had been tabulated and analysed. Based on the intial ergonomic assessment, total score achived is 17.7 with main risk factors identified through the hot work acticties are including awkward postures, repetitive motions, static and sustained work postures, vibration, insufficient ventilation, exposure of noise and working in extreme temperature. Based on Advanced ERA conducted on selected 3 workers, the study shows Muscle Fatigue Assessment (MFA) with average score for risk level shown ‘High’ and ‘Very High’ categories, Rapid Entire Body Assessment (REBA) with average total score more than 10 which categorized as ‘High Risk’ and Quick Exposure Check (QEC) which shown the workers have very high risk for back and shoulder or arm parts with score level are between 29 to 40 for back static and 41 to 56 for shoulder and arm parts. Based on results of the assessment, company XXX recommended had been to conduct further investigation for improvements to determine effective control measure for the work process in order to reduce that risk level towards the hot work workers.

Excessive exposure to heat can lead to injuries, illness, and death among mineworkers. The actual cost of heat-related injuries and illnesses is unknown because of underreporting and lack of symptom recognition. Multi-factorial, evidence-based, and field-ready guidelines for identifying–and predicting–physiological markers of heat strain are currently unavailable. The predicted heat strain (PHS) model, is the latest attempt by mining companies to aid in the evaluation and management of occupational heat exposures. The adopted algorithm relies on worksite environmental measurements and an estimate of individual metabolic rate for mine workers to provide an estimate of the workers’ core temperature during a work shift. There are several known limitations of the PHS model, including the assumption that the subject worker is hydrated and fit. A modified PHS model was presented based on eight physical parameters that are measured at different intervals during a work shift; these parameters are air temperature, relative humidity, air velocity, radiation, metabolic rate, acclimatization, clothing insulation and posture. To validate the results, the predictions from the modified PHS model were compared with direct physiological measurements obtained from ingestible pills and heat stress monitors under different environmental and working conditions.

Recently, micro-milling has been one of the most important technologies to produce miniature components, because optional geometrical structures can be machined with a high material removal rate. In terms of conventional dimensions, dynamic milling definitely signals the direction of development in modern technologies: dynamic milling results in higher productivity, better thermal circumstances, and increased tool life. The current paper gives a summary of the possible applications of dynamic milling tool paths in the case of micromachining. The major problems of this technology are the issue of minimum chip thickness and relatively large tool deformation. Different milling strategies, i.e. up milling and down milling, will be compared in detail. A systematic series of experiments were performed in order to generate data for the investigation. A special measuring system was established to perform related data collection. The experiments were carried out on a 5-axis micromachining centre using a tool steel workpiece with a hardness of 50 HRC. Based on the results of the experiments, the force components and the vibrations were also analysed at different radial depths of cut and different feed per tooth values, where productivity was also an important factor. It was found that dynamic milling can be applied in micro sizes, too. It is concluded that in the case of small contact angles, setting as high a feed per tooth value as 23.52 μm is also justified. During the investigation, optimal cutting parameters were also determined within the applied parameter range, these are ae = 34.80%, fz = 8.28 μm, and the use of the down milling strategy.

In this research, the microstructure evolution in the machined subsurface is numerically simulated through a developed multi-physics model applied to H13 hot work die steel. The multi-physics model based on dislocation density evolution is utilized to predict the change of grain size through finite element analysis by varying cutting parameters. In spite of the cutting conditions, the simulated grain size on the top-most machined surface is around 330 nm, and the machining-affected depth with refined grain varies in the range of 25–45 μm. In addition, the appeared periodical fluctuation of dislocation density and grain size in a wavy configuration induced by the generated serrated chip segments is revealed. The efficacy of the proposed finite element model is verified and the probable mechanism of grain refinement is demonstrated with the assistance of TEM observation, which in turn promotes the in-depth understanding of microstructure evolution during metal cutting.

H13 steel is a typical hot work die steel with good strength and toughness that is often used to manufacture high-temperature disk springs. However, disk springs occasionally fail after use in the petrochemical industry. Therefore, the effects of the quenching and tempering temperatures on the microstructure and mechanical properties of H13 steel after quenching and tempering processes are investigated herein. The results show that the lath width (lath) controls the strength of the H13 steel. The precipitated phases mainly comprise Cr23C6, Cr7C3 and VC. The coarsening of the Cr23C6 phase reduces the hardness, while reducing the dislocation density improves the toughness of the H13 steels after quenching and tempering. When the quenching temperature is 1040 °C and the tempering temperature is 570 °C, the H13 steel after quenching and tempering has a uniform microstructure with good strength and toughness.

In the past few decades, demand for precise miniature components has grown significantly. Modern production technologies required for the production of such components, including micro milling, have become extensively researched areas. In spite of the intensive research in this field, there are still many topics and aspects that merit investigation. Through a systematic series of experiments, this paper analyses the special characteristics of micro milling including cutting forces, vibrations, burr formation, and surface quality. A 5-axis micromachining centre with 60.000 rpm maximum spindle speed was used for the experiments carried out in the scope of this paper, and the machining of hardened hot-work tool steel (AISI H13) with a hardness of 50 HRC was investigated in detail. Also, a special measurement environment was prepared in order to collect machining data. Based on the results of the experiments, a power regression prediction model for cutting forces was created. As part of the analysis in the scope of the experiments, fast Fourier transformation was carried out in order to analyse the dynamic characteristics of the micro milling process, and to determine dominant frequencies. In addition, an analysis of variance (ANOVA) was applied to extensively analyse the main effects and interactions of different cutting parameters on different characteristics. Based on the investigations carried out in a comprehensive parameter range, an optimal parameter combination was also determined. The results of the experiments introduced in this paper contribute to a deeper understanding of the micro milling process, and this research provides information directly applicable in the industry.

The paper discusses some new technological solutions for producing die inserts for forging on forging machines the parts of a high-pressure tractor engine. In the current solution, the inserts were made of WNL (NiCrMoV6) steel, and then toughened. In the adopted new solution, the inserts made of cast steel with a composition corresponding to WCL (X38CrMoV5-1) steel, after toughening, were subjected to gas nitriding regulated by the NITREG method, or fluidized bed oxynitriding. The conducted tests of immediate resistance, impact strength and service life showed a beneficial effect of nitriding and oxynitriding on the properties and service life of die inserts. Precise casting of inserts by the Shaw method reducing their manufacturing costs, was also an interesting technological innovation.

Until now, additive manufacturing of high-performance materials such as martensitic hardenable tool steels is rarely investigated. This work addresses the introduction of an alternative alloying strategy for hot work tool steel powder, provided for laser powder bed fusion (L-PBF). The focus is on the question whether a powder mixture of spherical iron powder mixed with mechanically crushed ferroalloy particles can be processed by L-PBF, instead of using cost-intensive pre-alloyed gas-atomized powder, and to investigate the material properties associated with it. The particle morphology, packing density and flowability of this L-PBF powder feedstock is compared to gas-atomized spherical pre-alloyed steel powder and the results are correlated to the defect density, the resulting microstructure and the chemical homogeneity. Finally the resulting surface hardness is compared to a conventionally casted material as a reference state. It shows that the L-PBF fabrication of high-dense parts by means of both starting powders is technically feasible. Even though the alternative alloying concept promotes local chemical inhomogeneities within the microstructure, the overall porosity and the appearance of micro cracks are reduced.

Selected thermophysical properties of the hot work tool steel AISI H11 (1.2343) were measured in the temperature range from room temperature to the melting temperature. Thermal diffusivity was measured by the laser-flash method; heat capacity by differential scanning calorimetry; linear thermal expansion by push-rod dilatometry; and density at room temperature by an Archimedean balance. From these experimentally obtained data, thermal conductivity was calculated. Additionally, electrical resistivity of AISI H11 (1.2343) was measured by millisecond pulse-heating in the above mentioned temperature range. The measurement results of electrical resistivity as a function of specific enthalpy was combined with results of specific heat capacity measurements by differential-scanning calorimetry to obtain the relation between resistivity and temperature. Based on measured electrical resistivity and thermal conductivity, a Smith-Palmer-plot for the hot work tool steel AISI H11 (1.2343) is obtained for the ferritic and austenitic phases. No linear behaviour – as expected by the Wiedemann-Franz law – is observed in the ferritic phase region. In the high temperature austenitic region, the thermal conductivity can be computed from electrical resistivity using empirical constants of similar austenitic steels or superalloys.

Metal matrix composite materials are of high interest for their increased stiffness, strength or wear resistance. Wear resistant composites contain hard ceramic particles to reduce microcutting and grooving of the metal matrix surface. In this paper, a gas atomised hot work tool steel X40CrMoV5-1 (1.2344/AISI H13) was combined with fused tungsten carbide (FTC) particles in order to create forging tools with increased abrasive wear resistance. For that purpose, tool components were manufactured by sinter-forging of stacked powder layers to build up a graded hard phase concentration of up to 10 vol.-%. Subsequently, sinter-forged specimens were combined with basic hot work tool steel components and joined by diffusion bonding to assemble the complete tool. In order to evaluate their performance, the tools were examined in a hot backward can extrusion process of low-alloyed steel. Optical geometry measurements, light microscopy and scanning electron microscopy of the worn tool radii indicated a significant decrease in abrasive wear when using FTC-reinforced tools rather than conventional hardened tool steel.

The article discusses the issues of safe operations on the main gas pipelines of the Republic of Kazakhstan, which, as a result of deterioration of pipelines main part and their active susceptibility to stress corrosioncracking, require repair work. Considered new approaches of repair work organization by open fire using. It has beenanalyzed that the application of these measures in practice will ensure proper organizational planning and technicaltraining of personnel, and effective provision of necessary level safety for hot work. It was concluded that it isnecessary to introduce safety increasing measures during fire work on gas pipelines, it will prevent possible disasters,fires, destruction and human losses due to explosions during repair work on gas pipelines, as well as reduce damaging factors affecting workers health. It is shown that introduction of the named above measures helps to preventdisasters, fires, destruction and loss of life as a result of explosions during gas pipelines repair, as well as damagingfactors reduction that affect workers health during these types of work.

Hot work climate starts from the emergence of heat energy that comes from a heat source that is emitted directly or through an intermediary and enters the work environment, and becomes a heat pressure as an additional burden on the workforce. This can worsen health conditions and labor stamina when added to the heavy physical workload. The ceramics industry requires special and unique techniques such as combustion. The hot work climate itself can affect the physical and mental condition of workers. The impact that often occurs in workers due to the heat of work is fatigue and dehydration. The purpose of this study is to analyze the conditions of the work climate in the work environment and evaluate the work climate in the production section, which will be compared to the threshold value so that it can be used as a basis for carrying out control measures in an effort to prevent occupational diseases in the industry. This research is a descriptive study, using a cross sectional study design. Measurements of work climate carried out on 4 companies in the ceramics industry in the Gresik region with 10 measurement points in each company, are known to have results, most of which have ISBB values> 30ºC. Observations that have been carried out workloads on the ceramics industry are moderate workloads with a working time of 75% -100% with 25% rest time. based on the results of an average of 10 points from the four companies the ISBB value of measurement results is greater than the value of the NAB that has been set, with a value of 28ºC NAB. Therefore, the need to control the work climate both in its environment and its workers. These controls are general controls such as training (education / training), heat pressure control through the application of hygiene.

The failure mechanisms under thermal-mechanical conditions have always been a critical issue in hot work steels. However, previous studies mainly focused on the mechanical properties of hot work materials, while the underlying deformation mechanism remains largely unclear. Here, we investigate the crack morphology and microstructure evolution mechanism near the fracture surfaces of 4Cr5MoSiV1 hot work die steels subjected to the uniaxial tension at 580 °C. An evident deformation band was observed consisting of refined α-Fe grains with a width of about 100nm along both sides of the intergranular fracture surface. Additionally, characteristic slip band rings formed frequently, presumably due to the grain rotation near the crack. Finally, carbides (including MC, M7C3 and M23C6) were also considered as possible crack nucleation sources due to the existence of incoherent boundary between these carbides and the ferrite matrix. Keywords: 4Cr5MoSiV1 steel, Uniaxial tensile, Crack deformation band, Crystallite, Carbides

Introduction Heat stress can lead to various health issues that include heat rash, heat exhaustion, heat syncope, cramps, and heat stroke. Core body temperature, a reliable and accepted measurement for heat stress, can only be assessed via invasive means such as ingestible thermometer pills and rectal thermometers. The goal of this study was to determine a more convenient method of assessing heat stress by comparing temperature measurements from thermometer pills to measurements of a participant’s face taken with an infrared camera. Methods Workers at hot worksites had their temperatures recorded via ingestible thermometer pill and infrared camera over the course of a daytime work shift. Multivariate linear regression was used to evaluate the relationship, if any, between the thermometer pill and infrared camera while taking into account additional factors such as indoor and outdoor temperatures, age, gender, and BMI. Results/discussion A Pearson Correlation Coefficient of r = 0.611 was found. This is a strong correlation and shows potential for the infrared camera as a non-invasive alternative to the thermometer pill and rectal thermometer. One thermometer pill measurement of 86 °C was excluded due to verbal confirmation from the participant that they had taken a drink of water prior to measurement. Conclusions Statistical results showed that the ability of the infrared camera to successfully predict core body temperature measurements taken thermometer pill was strong (r = 0.611). More research should be conducted during times with warm outdoor temperatures and with larger sample sizes.

Since the popularization of press hardening in the early noughties, die and tooling systems have experienced considerable advances, with tool refrigeration as an important focus. However, it is still complicated to obtain homogeneous cooling and avoid hot spot issues in complex geometries. Additive Manufacturing allows designing cavities inside the material volume with little limitation in terms of channel intersection or bore entering and exit points. In this sense, this technology is a natural fit for obtaining surface-conforming cooling channels: an attractive prospect for refrigerated tools. This work describes a pilot experience in 3D-printed press hardening tools, comparing the performance of additive manufactured Maraging steel 1.2709 to conventional wrought hot work tool steel H13 on two different metrics: durability and thermal performance. For the first, wear studies were performed in a controlled pilot plant environment after 800 hot stamping strokes in an omega tool configuration. On the second, a demonstrator tool based on a commercial tool with hot spot issues, was produced by 3D printing including surface-conformal cooling channels. This tool was then used in a pilot press hardening line, in which tool temperature was analyzed and compared to an equivalent tool produced by conventional means. Results show that the Additive Manufacturing technologies can be successfully applied to the production of press hardening dies, particularly in intricate geometries where new cooling channel design strategies offer a solution for hot spots and inhomogeneous thermal loads.

Increasing the service life of die casting dies is an important goal of the foundry industry. Approaches are either material- or process-related. Despite new material concepts, hot work steels such as H11 are still predominantly used in the uncoated condition for die casting dies. In order to withstand the stresses that occur, this steel is used exclusively in the quenched and tempered condition. Required properties such as high high-temperature strength and high hardness combined with high toughness are, in principle, contradictory and can only be adjusted consistently over the entire die by furnace-based heat treatment. However, the results of various investigations have shown that improvements in the thermal shock resistance and wear resistance of hot work tool steels can be achieved by thermally influencing the microstructure near the surface. Based on these studies and related findings, an approach to surface heat treatment using the electron beam was developed. Due to the particle character of the radiation and the associated possibility of high-frequency beam deflection, the electron beam offers significantly greater flexibility in energy input into the workpiece surface compared with lasers or induction. The overall technological concept envisages replacing furnace-based heat treatment in the production of casting dies by localized and demand-oriented boundary layer heat treatment with the electron beam. The experiments include, on the one hand, the experimental determination of a suitable temperature–time interval with a focus on short-term austenitization. On the other hand, a simulation-based approach of boundary layer heat treatment with validation of a suitable heat source is investigated. Regarding short-term austenitization, the corresponding temperature and time range could be narrowed down more precisely. Some of these parameter combinations seem to be very suitable for practical use. The test specimens show a hard surface layer with a depth of at least up to 6 mm and a very tough buffer layer. Numerical simulation is used to estimate the resulting metallurgical microstructure and the achievable hardness as a function of the temperature–time interval. In addition, the results provided show the possibility of determining and optimizing the material properties by means of a simulation-based approach within the framework of a purely digital process planning and subsequently transferring them into a process planning. In the technical implementation, a temperature control was first established by means of a two-color pyrometer. In the further course of research, the pyrometer will be supplemented by an internally installed infrared camera, which will allow the reproducible setting of specified temperature profiles even for complex, large-area contours in the future.

The purpose of this study is to determine the causes of welding accidents on-board. The problem of work accidents is caused by the lack of the ship’s crew discipline to use the safety equipment while working. The data processing method was using descriptive method. The researchers tried to observe the cases that often occur on the ship related to the previous problem and note the causes and solutions to improve the ship’s crew discipline while working. The main potential hazards for hot work activities on vessels are fire and explosion. The implementation of the hot work permit system at Merak, Banten Port is in accordance with NFPA 51 B 2009 of Standard Fire Prevention during Welding, Cutting, and other Hot Work.

This study presents investigations on the additive manufacturing of hot work steel with the energy-reduced gas metal arc welding (GMAW) process, which is a cold metal transfer (CMT) process. The paper analyses the influence of arc energy and the thermal field on the resulting mechanical properties and microstructure of the material. The investigations were carried out with hot work tool steel X37CrMoV 5-1, which is used for the manufacturing of plastic moulds, hot extrusion dies, and forging dies. The results show that this steel can be used to generate 3D metal components or structures with high reproducibility, near-net-shaped geometry, absence of cracks, and a deposition rate of up to 3.6 kg/h. The variation of the wire feed speed and the welding speed enables the production of weld beads of width up to 9.4 mm. The mechanical properties of the generated structures can be adapted by the dominant thermal field, which in turn is influenced by the bypass temperature and the electric arc energy. A determining factor to describe the main variables of the welding process is represented by energy per unit length EL. If the bypass temperature is above the martensite start temperature (Ms), there is a homogeneous hardness level along the height of the additively manufactured structure height as long as the energy produced by the welding arc is enough to keep the temperature of all layers above Ms.

In this work, the H13 hot work die steels were surface modified and experimentally evaluated in a homemade thermal fatigue simulation tester. Two types of nitrided compound layers, and compound-free layers with and without surface deformation were prepared by a selection of surface modifications including traditional gas nitriding, controlled gas nitriding, gas nitriding with pre-shot peening, and controlled gas nitriding with post-shot peening. Thermal cracks formed in the nitrided compound layer propagated faster on surface but slower along the depth direction as compared to those in the compound-free layer. Thermal crack advancing along the depth direction in the sample nitrided with pre-shot peening had a tendency to be suppressed by the higher cross-sectional hardness distribution. The deformed compound-free nitrided layer showed the excellent thermal fatigue cracking resistance in both surface and cross-section, which was attributed to the good combination of hardness and toughness, as well as the underlying enhanced compressive residual stress.

The Stellite-6/WC composite coatings were produced on AISI H13 hot work tool steel by laser cladding with mixture of Co-coated WC (WC-12Co) particles and Stellite-6 powder. The phase composition, microstructural characterization, high temperature wear resistance and thermal fatigue behavior of Stellite-6/WC coatings were investigated and compared with the properties of the coatings produced from mixture of WC particles and Stellite-6 powder. The results showed that using the WC-12Co particles alleviated the decomposition of WC and resulted in the weaker intensity of W2C, CoCx and Co6W6C peaks in the X-Ray Diffraction (XRD) patterns. Compared with using the WC particles directly as the coating material, using the WC-12Co particles could further improve the wear resistance of coatings according to the relative lower width and depth of wear scars at the same WC content. In addition, fewer fatigue cracks were observed on the surface of coatings made by adding WC-12Co particles under the same thermal fatigue conditions, which indicates that using WC-12Co is beneficial to extend the life of Stellite-6/WC coatings.

Laser Powder Bed Fusion (LPBF) is an additive manufacturing process employed in the aerospace, automotive, and medical industries. In these sectors, nickel-, aluminium-, and titanium-based alloys are mainly used for various applications. Yet, only few of the commonly used steels have been qualified for the LPBF process in the mechanical engineering industry, which normally uses hot work tool steels with less than 0.5 wt.-% carbon content. However, many applications need high wear-resistant steel alloys with high hardness, both of which can be achieved with a higher carbon content, like in high-speed steels. But when processed with LPBF, these steels often form cracks, making the process very challenging. In this feasibility investigation, we demonstrate that LPBF can be used to manufacture dense and crack-free specimens with a hardness of over 62 HRC (as built) from high-speed steel AISI M50 (carbon content of 0.8 wt.-%). Furthermore, we evaluate the influence of typical LPBF process parameters, especially of preheating temperatures up to 500 ℃, on the microstructure of the specimens.

Purpose: The purpose of this investigation was to determine the changes in the surface layer (Inconel 625), obtained during the laser treatment of tool-steel alloy for hot work by the use high-power fibre laser. Design/methodology/approach: Observations of the layer structure, HAZ, and substrate material were made using light and scanning microscopy. The composition of elements and a detailed analysis of the chemical composition in micro-areas was made using the EDS X-ray detector. The thickness of the resulting welds, heat affected zone (HAZ) and the contribution of the base material in the layers was determined. Findings: As a result of laser cladding, using Inconel 625 powder, in the weld overlay microstructure characteristic zones are formed: at the penetration boundary, in the middle of weld overlay and in its top layer. It was found that the height of weld overlay, depth of penetration, width of weld overlay and depth of the heat affected zone grows together with the increasing laser power. Practical implications: Laser cladding is one of the most modern repair processes for eliminating losses, voids, porosity, and cracks on the surface of various metals, including tool alloys for hot work. Laser techniques allow to make layers of materials on the repaired surface, that can significantly differ in chemical composition from the based material (substrate material) or are the same. Originality/value: A significant, dynamic development in materials engineering as well as welding technologies provides the possibility to reduce the cost of production and operation of machinery and equipment, among others by designing parts from materials with special properties (both mechanical and tribological) and the possibility of regeneration of each consumed element with one of the selected welding technologies.

This paper presents a multi-scale analysis of the mechanical behaviour of hot work steels taking into account the effect of residual stress generated by the initial microstructure and the external load and induced industrially by heat treatment and machining process. The methodology is based on: i) laboratory study to evaluate the macroscopic behaviour of the material, ii) numerical simulation based on finite element and homogenisation approaches to evaluate the material's microstructure complexity and characterize the residual stress distribution, iii) industrial tests during pretreatment and forging process of valve gas parts in order to complete the results obtained at laboratory scale. It was proved that residual stress induced by the initial microstructure of the hot steel material has significant effects on the stress behaviour of the hot forging steel under static tensile load. Besides, the residual stress generated during the manufacturing process affected more significantly the stress distribution on the die surface than the heat treatment, inducing residual stress close to plastic deformation.

One of the major advantages of micromachining is the high achievable surface quality at highly flexible capabilities in terms of the machining of workpieces with complex geometric properties. Unfortunately, finishing operations often result in extensive process times due to the dependency of the resulting surface topography on the cutting parameter, e.g., the feed per tooth, fz. To overcome this dependency, special tool shapes, called wipers, have proven themselves in the field of turning. This paper presents the transfer of such tool shapes to solid carbide milling tools for micromachining. In this context, a material removal simulation (MRS) was used to investigate promising wiper geometries for micro end mills (d = 1 mm). Through experimental validation of the results, the surface topography, the resulting process forces, and tendencies in the residual stress state were investigated, machining the hot work tool steel (AISI H11). The surface-related results show a high agreement and thus the potential of MRS for tool development. Deviations from the experimental data for large wipers could be attributed to the non-modeled tool deflections, friction, and plastic deformations. Furthermore, a slight geometry-dependent increase in cutting forces and compressive stresses were observed, while a significant reduction in roughness up to 84% and favorable topography conditions were achieved by adjusting wipers and cutting parameters.

The aim of this work is to develop a die material selection criterion for aluminum hot stamping applications. The criterion has been based on the back-to-back comparison of a set of reciprocating friction and wear tests. Three representatives belonging to different stamping die material families have been selected for the study: a cold work steel, a hot work steel, and a cast iron. These tool materials have been combined with an exemplary member from two heat treatable aluminum families: 2XXX and 6XXX. Each die-material/aluminum–alloy combination has been tested at three temperatures: 40, 200, and 450 ºC. The temperatures have been selected according to different stamping scenarios: long takt time press quenching, short takt time press quenching, and very short takt time hot forming without quenching, respectively. The results show that, among the three die material options available, the cold work steel turned out to be the most favorable option for high volume production and long takt time, the hot work steel fitted best for high volume production coupled with short takt time, and cast iron turned to outstand for short runs with prototype dies and for hot stamping without die quenching.

Each workplace must have its own source of danger which can cause health problems or occupationaldiseases due to the exception of informal sector workers such as brick workers. Health problems that canbe experienced are dehydration caused by exposure to hot working climate. Incidence of dehydration cancause workers to get tired quickly and decrease productivity. The purpose of this study was to analyze thecorrelation between hot working climate with dehydration on bricks workers in one of Mojosulur’s brickhome industries. Methodes of his research is an analytic observational study, with cross sectional design.The subjects of this study were all brick workers in one of the brick home industries in Mojosulur by 30respondents. The results of the study showed that most brick workers were dehydrated, varying in level,both moderate and severe dehydration. The results of statistical analysis show that the correlation coefficient(r = 0.638) which can be interpreted as a work climate factor has a strong correlation with the incidenceof dehydration Conclusion of this research on work climate and dehydration of brick workers in one ofMojosulur’s brick home industries have a very strong correlation.

In recent years, hard turning, an alternative to grinding, which provides low cost and good surface quality, has become an attractive method to the manufacturers. In this experimental study, AISI H11 hot work tool steel that has been hardened up to 50 HRC was subjected to hard turning tests with coated carbide tooling. The analyses were carried out by applying response surface methodology with the analysis of variance method. A total of 27 experiments were modeled utilizing 3 3 full factorial design and were carried out using a CNC lathe. The effects of the cutting parameters on surface roughness, energy consumption, electric current value, and sound intensity level were investigated. Optimum cutting parameters and levels were determined according to these optimum values. The relationship between cutting parameters and output variables was analyzed with two-dimensional and three-dimensional graphics. The results show that while the most effective parameter on the surface roughness was the feed rate (88.62%), the most effective parameter on the sound intensity level was the cutting speed (44.92%). In addition, the cutting depth was the most effective parameter on both electric current (52.20%) and energy consumption (46.15%). Finally, regression coefficients were determined as a mathematical model, and it was observed that this estimated model gave results that were very similar to those achieved with real experiment (correlation values: 97.64% for surface roughness, 98.72% for energy consumption, 97.22% for electric current value, and 91.38% for sound intensity level).