Journal articles: 'Hot working results'

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Wang, Heng, Shukun Cao ※, Quancheng Dong, Yi Cui, Zijian Cao, Shuqiang Xu, Xiangwen Song, and Hao Shen. "Optimization and control of working parameters of hot blast furnace." MATEC Web of Conferences 175 (2018): 02030. http://dx.doi.org/10.1051/matecconf/201817502030.

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In order to improve the working efficiency of hot blast stoves, reduce environmental pollution, reduce labor intensity and improve combustion efficiency, this paper uses ANSYS software to simulate the temperature field and flow field of the hot blast stove, and uses the PID controller to realize the automatic control of the hot blast stove. The model and working principle of the hot blast stove are briefly introduced. The operating parameters (blowing fan air flow, coal intake) of the hot blast stove are briefly studied. The results show that the amount of air flow of the blast furnace depends on the coal intake of the hot blast stove, which is generally per kilogram of coal. 8m3-10m3- air is required. When the coal intake is 120kg/h and the air volume of the blower is 1200m3/h, the hot blast stove can work stably with high efficiency. The results obtained are input into the database for later combustion. The work provides a theoretical basis.

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Popa, Mihai, Bogdan Pricop, Elena Mihalache, Leandru Gheorghe Bujoreanu, and Nicoleta Monica Lohan. "Hot Working Effects on the Damping Behavior of Shape Memory Alloys." Materials Science Forum 907 (September 2017): 180–87. http://dx.doi.org/10.4028/www.scientific.net/msf.907.180.

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Cu-Zn-Al shape memory alloys (SMAs) were analysed in two different processing states: (i) hot-forged and (ii) hot-rolled. Both hot-forged and hot-rolled specimens were cut into lamellar configuration, before being homogenized (1073 K/ 18 ks/ water) and tempered (373, 473, 573, 673 K/ 300 s/ water). From each of the five differently treated lamellas, in hot-forged and hot-rolled states, rectangular specimens were cut for dynamic mechanical analysis (DMA). The remaining segments were sectioned into metallographic specimens. The metallographic specimens were embedded into could mounting resin, ground, polished and etched for scanning electron microscopy (SEM) -observations. DMA results revealed the influence of plastic deformation procedure and heat treatment temperature on the reversible martensitic transformation.

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Bartkowiak, Grażyna, and Pamela Miśkiewicz. "Firefighters’ preferences regarding underwear – survey results." Occupational Safety – Science and Practice 564, no. 9 (September 21, 2018): 14–17. http://dx.doi.org/10.5604/01.3001.0012.4721.

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People working as firefighters are frequently exposed to heat factors such as flame or hot objects and surfaces associated with the work environment. As a result of the combination of protective clothing and physical effort in the hot microclimate, unfavorable hydrothermal conditions are formed under clothing, causing serious thermal discomfort. Improving comfort and safety of firefighters can be obtained among others through properly selected underwear clothing made from materials supporting the removal of sweat, water vapour and heat, limiting the accumulation of heat. In order to obtain information about the clothing worn under protective clothing and underwear which is most often used and to recognize preferences and expectations in this area, a survey was carried out among firefighters who are exposed to heat factors during fire-fighting activities.

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Wang, Heng, Shukun Cao, Yi Cui, Zijian Cao, and Shuqiang Xu. "Analysis of temperature field of grain and drying medium for grain drying integrated mechanical device." MATEC Web of Conferences 175 (2018): 02024. http://dx.doi.org/10.1051/matecconf/201817502024.

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In order to improve the working efficiency of the drying tower and the hot blast stove in the process of grain drying, this paper proposes a method to solve the problems of air pollution and energy waste caused by excessive combustion or insufficient combustion of the hot blast stove. Based on finite element analysis, this paper uses ANSYS software to simulate the drying process of grain. This paper briefly introduces the grain drying device model and working mechanism, analyzes the temperature field of the drying device, and studies the influence on the drying effect of the working parameters (hot water, hot air, hot air hot blast stove combustion temperature) during the grain drying process. The results show that the hot air temperature is 85°C, the hot water temperature is 90°C, the combustion chamber temperature is 480°C, the grain drying effect is good, the combustion efficiency of the combustion furnace is the best, and the energy utilization rate is the highest.

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Zhang, Yan Shu, and Yan Sun. "Investigation on Constitutive Equations for TA15 during Hot Working." Applied Mechanics and Materials 184-185 (June 2012): 1492–96. http://dx.doi.org/10.4028/www.scientific.net/amm.184-185.1492.

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Hot compression tests were conducted on Gleeble-1500 thermal simulator for TA15 titanium alloy at temperatures of 750~1050 °C and at strain rate of 0.001 ~ 1 s with a deformation reduction of 60%. The results show that the flow stress of TA15 titanium alloy increases rapidly to a peak with deformation strain, then decreases to a saturation status. The steady and peak stress significantly decreases with deformation temperature increasing and strain rate decreasing. The activation energies (Q) are 619.264kJ/mol in (α+β) phase and 522.58kJ/mol in β phase, respectively. It was found that the parameters, peak stress σp, steady stress σres, peak strain εp and steady strain εres, have linear relationships with Zenner-Hollomon parameter, Z.

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Cebulski, Janusz, Dorota Pasek, Bartosz Chmiela, Magdalena Popczyk, Andrzej Szymon Swinarew, Arkadiusz Stanula, Zbigniew Waśkiewicz, and Beat Knechtle. "Evaluation of Structure and Corrosion Behavior of FeAl Alloy after Crystallization, Hot Extrusion and Hot Rolling." Materials 13, no. 9 (April 27, 2020): 2041. http://dx.doi.org/10.3390/ma13092041.

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The paper presents the results of tests on the corrosion resistance of Fe40Al5Cr0.2TiB alloy after casting, plastic working using extrusion and rolling methods. Examination of the microstructure of the Fe40Al5Cr0.2TiB alloy after casting and after plastic working was performed on an Olympus GX51 light microscope. The stereological relationships of the alloy microstructure in the state after crystallization and after plastic working were determined. The quantitative analysis of the structure was conducted after testing with the EBSD INCA HKL detector and the Nordlys II analysis system (Channel 5), which was equipped with the Hitachi S-3400N microscope. Structure tests and corrosion tests were performed on tests cut perpendicular to the ingot axis, extrusion direction, and rolling direction. As a result of the tests, it was found that the crystallized alloy has better corrosion resistance than plastically processed material. Plastic working increases the intensity of the electrochemical corrosion of the examined alloy. It was found that as-cast alloy is the most resistant to corrosion in a 5% NaCl compared with the alloys after hot extrusion and after hot rolling. The parameters in this study show the smallest value of the corrosion current density and corrosion rate as well as the more positive value of corrosion potential.

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Alcelay, Ignacio, Esteban Peña, and Anas Al Omar. "Hot working behaviour and processing maps of duplex cast steel." International Journal of Materials Research 112, no. 7 (July 1, 2021): 518–26. http://dx.doi.org/10.1515/ijmr-2021-8242.

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Abstract In this paper the hot working behaviour of medium carbon duplex cast steel is studied using uniaxial hot compression tests over a temperature range varying from 700 ˚C to 1 000 °C and at different strain rates ranging from 10–4 to 10–1 s–1. A model based on a variant of a dynamic materials model was employed to construct processing maps. These maps delineate the safe and unsafe domains. The safe domains, associated with dynamic recrystallization and dynamic recovery, can be chosen to optimize the hot workability of the studied material. Whereas, the unsafe domain is to be avoided because it is associated with plastic deformation instabilities. The domain associated with dynamic recrystallization is centred at 1000 °C and 10–4 s–1 with a peak energy dissipation efficiency of about 40%, while the domain associated with dynamic recovery is centred at 700 °C and 10–4 s–1 with a peak energy dissipation efficiency of about 27%. The unsafe hot working domain, spread over the entire temperature range and moderate to high strain rates, predicts the appearance of flow instabilities, in the form of shear bands and intergranular cracks. To validate the obtained results, microstructural observations corresponding to different processing conditions are presented.

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Zhang, Xiao Ping, and Wen Zhang Chen. "Experimental Research on Hot Working Property of Monel K-500 Alloy." Advanced Materials Research 712-715 (June 2013): 87–93. http://dx.doi.org/10.4028/www.scientific.net/amr.712-715.87.

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Monel K-500 alloy is an important nickel-based corrosion resistant material with excellent corrosion resistant ability in various corrosion circumstances (include electrochemical and chemical corrosion) and good mechanical properties. However, Monel K-500 alloy is also a sensitive material to high temperature. Hot working process has significant effect on its working character and quality. In view of existing problems in domestic manufacturing enterprises, some experiments were carried out in different working temperature, deformation degree and strain rate to investigate the performance of Monel K-500 alloy in hot working process. The research results show that moderate temperature, higher strain rate and deformation degree will be favorable to improve crystal structure and mechanical property of Monel K-500 Alloy.

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Li, Lei, Yu Qi Chen, Qiang Li, and Guo Jie Huang. "Study on the Microstructures and Properties of the Lead-Free Easy-Cutting Bial-Brass." Advanced Materials Research 463-464 (February 2012): 1057–61. http://dx.doi.org/10.4028/www.scientific.net/amr.463-464.1057.

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Traditional lead brass products pollute the environment and do harm to the human health. Fabrication of the new kind of the brass without lead is an urgent task. Bi-brass is the most popular lead-free easy-cutting brass. However, its mechanical and hot-working properties are not satisfied. In present paper, aluminum element was added into the Bi-brass alloy in order to improve the alloy’s mechanical and hot-working property. Experiment results showed that the aluminum can increase the surface tension of the Bi and change the existing morphology of Bi from film-like into particle-like. Therefore, the ingot’s hot-working property is excellent. Experiment results showed that even the extrusion ration reaches 256, the ingot still can be extruded into rod successfully. Experiment results also indicated that the homogenizing annealing treatment on the ingot and addition of the rare earth La did not improve the mechanical properties or the machinability.

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Lin, Y. C., and Xiao-Min Chen. "A critical review of experimental results and constitutive descriptions for metals and alloys in hot working." Materials & Design 32, no. 4 (April 2011): 1733–59. http://dx.doi.org/10.1016/j.matdes.2010.11.048.

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Kuc, Dariusz, Eugeniusz Hadasik, Jaroslaw Mizera, and Tomasz Mikuszewski. "Plasticity and Microstructure of Magnesium - Lithium Alloys." Solid State Phenomena 212 (December 2013): 11–14. http://dx.doi.org/10.4028/www.scientific.net/ssp.212.11.

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The article presents the results of tests connected with influence of strain parameters on the susceptibility to hot working of magnesium lithium alloys with lithium content of 7.5% mass. Plasticity tests were conducted in compression test from room temperature up to 400°C with strain rate of 0.1s-1. Conducted tests allowed for determination of susceptibility of magnesium alloys with different lithium content to hot working. The results were compared with typical alloy AZ31. The results of influence of deformation temperature on the microstructure of tested alloys are also presented in this paper.

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Ye, Hongyu, Xuancang Wang, Naren Fang, Ziyuan Su, and Xiaowen Sun. "Interlayer Working Conditions Classification and Treatment Measures of Airport Asphalt Pavement Overlay." Journal of Advanced Transportation 2019 (December 31, 2019): 1–16. http://dx.doi.org/10.1155/2019/9646091.

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The bonding strength between the overlays of an airport asphalt pavement directly affects its service life. In this study, a finite element model of asphalt overlay on airport pavement of Juba Airport in South Sudan was established, and the elastic modulus of overlay, thickness of overlay, running state of aircraft, variation trend of interlayer shear stress under the action of load and temperature were obtained. The AHP-entropy method was used to calculate the combined weight of each influencing factor. The climate in hot and humid areas was further zoned, and a comprehensive classification of airport asphalt pavement overlay between hot and humid tropics was obtained. Four interlayer treatment measures (asphalt precoating, two oils and one aggregate, geotextile, and geogrid) and three interlayer materials (SBS-modified asphalt, ordinary hot asphalt, and SBS-modified emulsified asphalt) were designed and tested. Through shear test, wheel-load fatigue test, and pressurized seepage test, the variation trends of interlayer shear, crack resistance, and waterproofing under different combination schemes were obtained. Finally, the matching relationship between different working conditions and interlayer treatment measures was established. The results show that the actual working conditions of an airport asphalt pavement can be divided into three levels. Combined with the performance ranking of different materials and interlayer treatment measures, the recommended interlayer treatment measures for comprehensive classifications I, II, and III are two oils and one material + SBS-modified asphalt, asphalt precoating, or geogrid + SBS-modified emulsified asphalt or ordinary hot asphalt, and geotextile + ordinary hot asphalt, respectively. The working conditions in Juba Airport in South Sudan can be classified as comprehensive classification II, the recommended treatment measures for geogrid + ordinary hot asphalt.

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Varela-Castro, Gonzalo, Jose María Cabrera, and Jose Manuel Prado. "Influence of Manganese on the Hot Working Behaviour of Construction Steels." Advanced Materials Research 89-91 (January 2010): 580–85. http://dx.doi.org/10.4028/www.scientific.net/amr.89-91.580.

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The microstructural control of rolled products is based on managing the austenite phase transformations during and after hot deformation to attain the desired microstructure after the cooling step. Therefore, it is very important an appropriate description of the kinetics of the hardening and softening phenomena taking place during the deformation at high temperatures, namely, dynamic recovery (DRV) and recrystallization (DRX). This investigation examines the effect of manganese contents on the hot flow behaviour of plain carbon steels. For this purpose, uniaxial hot compression tests were carried out in carbon steels in an extensive range of temperatures, from 1123 to 1373 K and strain rates, from 510-4 to 110-1 s-1. This work is focused in determining the physically-based constitutive equations that govern the plastic behaviour of plain carbon steels. Experimental results were compared with the predictions of the model and an excellent agreement over a broad range of temperatures and strain rates was obtained.

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Matougui, Nadjoua, Mohamed Lamine Fares, and David Piot. "Dynamic Recrystallization Mechanisms of Nickel Niobium Alloys during Hot Working." Materials Science Forum 1016 (January 2021): 869–74. http://dx.doi.org/10.4028/www.scientific.net/msf.1016.869.

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This present work examines the influence of niobium in solid solution on the microstructural evolution of pure nickel at various deformation conditions. On this purpose, high-purity nickel and six model nickel-niobium alloys (Ni–0.01, 0.1, 1, 2, 5 and 10 wt. % Nb) were subjected to hot torsion test to large strains within the temperature range from 800 to 1000 °C at strain rates of 0.03, 0.1 and 0.3 s–1. Microstructural analyses were carried out using both optical and scanning electron microscopy-based electron back-scattered diffraction technique. The overall results showed the key role played by the Nb amount when coupled with various DRX mechanisms involved, i.e. DDRX, CDRX, and GDRX with respect to the prescribed deformation conditions, in reducing grain size and retarding DRX kinetics from which the microstructures of the examined materials such as Ni 2 and 10 wt. % Nb were seen evolving in different ways. In all these deformed materials, a transition from discontinuous dynamic recrystallization to continuous dynamic recrystallization was observed at low temperature and high strain rate whereas only discontinuous dynamic recrystallization occurred at high temperature.

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Gong, Zhihua, Hansheng Bao, and Gang Yang. "Dynamic Recrystallization and Hot-Working Characteristics of Ni-Based Alloy with Different Tungsten Content." Metals 9, no. 3 (March 6, 2019): 298. http://dx.doi.org/10.3390/met9030298.

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The hot deformation behavior of the GY200 Ni-based alloys with different tungsten (W) content were investigated by means of hot compression tests, microscopic observations, and processing maps at temperatures between 950 °C and 1200 °C, strain rate between 0.01 s−1 and 10 s−1 with strain of 0.9. The hyperbolic-sine type constitutive equations were established between peaks tress and deformation conditions through Z parameters, and for alloys with higher W content results in higher activation energy and complete recrystallization temperature. The hot-working maps were exploited based on the experimental data. The hot-working maps showed that the instability zone extended with increasing W content. The stable domain of alloys are located in the temperature range between 1025 °C and 1200 °C and strain rate range between 0.01 s−1 and 1 s−1, dominated by the dynamic recrystallization (DRX) microstructural evolution, suited for hot deformation. The cracking on the surface of the sample compressed at 950 °C was resulted from the tensile stress, while the fracture of the sample compressed at 1200 °C was triggered by the melting of grain boundaries.

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Zhang, Hai Yan, Shi Hong Zhang, and Ming Cheng. "Influence of δ Phase Content on Hot Deformation Behavior of Ni-Based Superalloy IN718." Advanced Materials Research 314-316 (August 2011): 1159–62. http://dx.doi.org/10.4028/www.scientific.net/amr.314-316.1159.

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The effect of δ phase content on the hot deformation behavior of alloy IN718 has been investigated using isothermal compression tests. The results indicated that the δ phase has a significant effect on the deformation behavior of alloy IN718 during hot working. After the peak stress, the decreasing speed of the stress raises as the increase in the δ phase content. The deformation activation energy for alloy IN718 increases with the raise of the δ phase content. And the peak strain for the alloy decreases with the increase of the δ phase content, which indicates that the δ phase can stimulate the occurrence of dynamic recrystallization during hot working.

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Wojtacha, Anna, and Marek Opiela. "Hot Working Behavior in Multiphase Steel with Ti and V." Materials 15, no. 17 (August 25, 2022): 5852. http://dx.doi.org/10.3390/ma15175852.

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This study investigated the effect of hot working conditions on changes in yield stress and the softening degree in the newly developed multiphase steel with Ti and V microadditions. The research was performed on the GLEEBLE 3800 thermomechanical simulator. In order to determine the σ-ε curves, continuous compression tests were carried out. The samples were plastically deformed at temperatures from 900 °C to 1100 °C at the rate of 0.1 s−1, 1 s−1 and 10 s−1. The activation energy of the plastic deformation was 375 kJ·mol−1. The analysis of the shape and course of the curves indicated that the decrease in strain hardening was mainly the result of the continuous dynamic recrystallization process. Two-stage compression with isothermal holding of the samples was also carried out between the two stages of deformation lasting from 1 s to 50 s. The structure of primary austenite was generated using the ARPGE software. The different size of austenite grain is the result of various thermally activated processes—when increasing the strain rate from 0.1 s−1 to 10 s−1, the average grain size of the primary austenite decreases from approx. 16 µm to approx. 6 µm. The time t0.5 needed to form 50% of the austenite fraction recrystallized at 1100 °C is approx. 4 s and extends to approx. 10 s with the reduction in the plastic deformation temperature to 900 °C. The time of complete austenite recrystallization tR, which varies from approx. 50 s to approx. 90 s in the tested temperature range, lengthens even more. The obtained results make it possible to develop thermomechanical treatment technology for the production of forgings from the tested multiphase steel.

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Zhao, Xin, Hong Zhao, and Rui Zhang. "Processing Maps for TC18 Titanium Alloy Deformed in α+β Region." Advanced Materials Research 490-495 (March 2012): 3423–26. http://dx.doi.org/10.4028/www.scientific.net/amr.490-495.3423.

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The hot deformation characteristics of TC18 titanium alloy were studied in the temperature range 750-850°C and strain rate range 0.001-1 s-1 by using hot compression tests. Processing maps for hot working are developed on the basis of the variations of efficiency of power dissipation with temperature and strain rate. The results reveal that the flow stress of TC18 is sensitive to strain rate. Processing map at stain of 0.6 reveals two domains: one is centered at 750°C and 0.001s-1; another is centered at 850°C and 0.001s-1. The maximum efficiency is more than 60%. According to the maps, the zone with the temperature range of 750-850°C and strain rate range of 0.01-0.001s-1 may be suitable for hot working

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YEOM, JONG-TAEK, EUN JEOUNG JUNG, JEE HOON KIM, JEOUNG HAN KIM, JAE-KEUN HONG, NHO-KWANG PARK, KOOK-JOO KIM, and SEUNG-SIK CHOI. "MODELING AND SIMULATION OF DYNAMIC RECRYSTALLIZATION AND GRAIN GROWTH DURING HOT WORKING OF INCONEL 783 SUPERALLOY." Surface Review and Letters 17, no. 01 (February 2010): 105–9. http://dx.doi.org/10.1142/s0218625x10014041.

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In this study, the modeling of recrystallization and grain growth was investigated to predict the microstructure evolution during hot working of INCONEL 783 superalloy (Alloy 783). The recrystallization model was constructed on the basis of the Avrami formation. A least-square optimization technique was used to determine several important parameters within the model from isothermal heat treatment and hot compression test results. High temperature compression tests were carried out under different temperatures, strain rates and strain conditions. The model for describing the recrystallization and grain growth behaviors of Alloy 783 was implemented onto the user-subroutine of a commercial FE code. In order to demonstrate the reliability of the model, the microstructure evolution of Alloy 783 alloy during the hot compression test was simulated and was accorded well with the experimental results.

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Chen, Rongchuang, Haifeng Xiao, Min Wang, and Jianjun Li. "Hot Workability of 300M Steel Investigated by In Situ and Ex Situ Compression Tests." Metals 9, no. 8 (August 10, 2019): 880. http://dx.doi.org/10.3390/met9080880.

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In this work, hot compression experiments of 300M steel were performed at 900–1150 °C and 0.01–10 s−1. The relation of flow stress and microstructure evolution was analyzed. The intriguing finding was that at a lower strain rate (0.01 s−1), the flow stress curves were single-peaked, while at a higher strain rate (10 s−1), no peak occurred. Metallographic observation results revealed the phenomenon was because dynamic recrystallization was more complete at a lower strain rate. In situ compression tests were carried out to compare with the results by ex situ compression tests. Hot working maps representing the influences of strains, strain rates, and temperatures were established. It was found that the power dissipation coefficient was not only related to the recrystallized grain size but was also related to the volume fraction of recrystallized grains. The optimal hot working parameters were suggested. This work provides comprehensive understanding of the hot workability of 300M steel in thermal compression.

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Berns, H., and H. Pinto. "Anisotropic size change during continuous quenching and deep freezing of tool steel ^*." HTM Journal of Heat Treatment and Materials 62, no. 5 (October 1, 2007): 221–28. http://dx.doi.org/10.1515/htm-2007-0007.

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Abstract The size change of a low carbon maraging steel and of a ledeburitic cold work tool steel produced by ingot (IN) or powder metallurgy (PM) was measured by dilatometry using specimens taken in longitudinal or transverse direction of hot working. The anisotropy of the size change during martensitic transformation ΔεM was negative for the maraging and the PM steel, but positive for the IN steel and the more so, if the cooling rate was raised by injecting liquid nitrogen during quenching to −150 °C. The microstructure and texture was investigated by high resolution SEM equipped with microprobe analysis and respective imaging as well as by EBSD. The results show that Δεis not related to a texture M of the martensitic matrix but to a microstructural banding caused by microsegregation and hot working. The alignment of the eutectic M7 C3 carbides in the direction of hot working coincides with their texture.

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Ulbrich, Dariusz, Arkadiusz Stachowiak, Jakub Kowalczyk, Daniel Wieczorek, and Waldemar Matysiak. "Tribocorrosion and Abrasive Wear Test of 22MnCrB5 Hot-Formed Steel." Materials 15, no. 11 (May 30, 2022): 3892. http://dx.doi.org/10.3390/ma15113892.

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The article presents the results of research on abrasive and tribocorrosion wear of boron steel. This type of steel is used in the automotive and agricultural industries for the production of tools working in soil. The main goal of the article is the evaluation of tribocorrosion and abrasive wear for hot-formed 22MnCrB5 steel and a comparison of the obtained results with test results for steel in a cold-formed state. The spinning bowl method to determine the wear of samples working in the abrasive mass was used. Furthermore, a stand developed based on the ball-on-plate system allows to determine the wear during the interaction of friction and corrosion. After the hot-forming process, 22MnCrB5 steel was three times more resistant for the abrasive wear than steel without this treatment. The average wear intensity for 22MnCrB5 untreated steel was 0.00046 g per km, while for 22MnCrB5 hot-formed steel it was 0.00014 g per km. The tribocorrosion tests show that the wear trace of hot-formed 22MnCrB5 steel was about 7.03 µm, and for cold-formed 22MnCrB5 steel a 12.11 µm trace was noticed. The hot-forming method allows to obtain the desired shape of the machine element and improves the anti-wear and anti-corrosion properties for boron steel.

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Bartkowiak, Grażyna, Anna Dąbrowska, and Anna Marszałek. "Assessment of the human responses to the influence of personal liquid cooling system in the hot environment." International Journal of Clothing Science and Technology 26, no. 2 (May 27, 2014): 145–63. http://dx.doi.org/10.1108/ijcst-03-2013-0024.

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Purpose – People working in the hot environment are constantly exposed to the overheating, that can lead to cardiovascular disorders and as a consequence result in occupational diseases. The purpose of this paper is to present developed personal liquid cooling system that is able to efficiently draw excess heat from the human organism, protecting against thermal stress. Design/methodology/approach – The paper presents study concerning the assessment of effect of the coolant temperature in the developed liquid cooling garment (LCG) on physiological parameters of the subjects (heart rate, body temperature, skin temperature) and parameters of the undergarment microclimate, as well as subjective sensations reported by volunteers exercising in hot microclimate while wearing LCG and without LCG. Findings – Obtained results of physiological parameters measurements, as well as undergarment physical parameters and volunteers subjective sensations, proved satisfactory level of thermal stress reduction while working in the aluminized protective clothing in hot environment by the developed personal liquid cooling system for the variant with coolant temperature 19°C and the flow rate 0.9 dm3/min. Originality/value – This paper presents a new clothing construction intended for LCG that can efficiently support human thermoregulation processes while working in the hot environment.

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Deng, Xiaodong, Jianli Li, and Xiao Xie. "Effect of Preheating Temperature on Thermal–Mechanical Properties of Dry Vibrating MgO-Based Material Lining in the Tundish." Materials 15, no. 21 (November 2, 2022): 7699. http://dx.doi.org/10.3390/ma15217699.

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For the collapse of the working layer of dry vibrating material during preheating, the four-strand tundish of a steel plant was taken as a prototype for numerical simulation. The software ANSYS was used to calculate the temperature field and stress and strain field on the working layer under three preheating stages through the indirect coupling method. The results show that during the preheating process, the temperature field distribution on the hot surface of the working layer gradually develops toward uniformity with the increase in preheating temperature. However, the temperature gradient between the cold and hot surfaces increases subsequently, and the highest temperature between the cold and hot surfaces reaches 145.31 °C in the big fire stage. The stress on the top of the working layer is much larger than in other areas, and the maximum tensile stress on the top reaches 39.06 MPa in the third stage of preheating. Therefore, the damage to the working layer starts from the top of the tundish. In addition, the strain of the area near the sidewall burner nozzle in the casting area is much larger than that in the middle burner area with the increase in preheating temperature. Thus, the working layer near the sidewall burner nozzle is more prone to damage and collapse compared with the middle burner nozzle.

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Amori, Dr Karima E., Dr Mohammad N. Hussain, Zainab T. Abdulwahab, and Wafa O. Ali. "Utilizing OF Thermal Energy OF Gas Turbines Exhaust Gases Working IN Petroleum Sector." Journal of Petroleum Research and Studies 7, no. 2 (May 6, 2021): 190–210. http://dx.doi.org/10.52716/jprs.v7i2.196.

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The gas turbine stations are used in petroleum sector for different application, such as compressing of gas, pumping of crude oil or water, and power generation. The main parts of these stations are compressor, combustion chamber, and gas turbine. The compressor provides a compressed air for combustion process, and for cooling process of different parts of the station. The fuel (liquid or gas fuel) is injected into the combustion chamber to perform the combustion process. The resulted hot flue gases are passed to the gas turbine to convert its' thermal energy into rotational mechanical energy to operate the air and gas compressors, crude oil or water pumps, and to generate electricity.This work concerns with the applicability of utilizing the thermal energy content in flue gases exit from the gas turbine by adopting a field data received from one of the operating stations in north Oil Company in Iraq. The flue gases mass flow rate, and its' available energy have been calculated. Different operational conditions have been selected to produce superheated steam such as operating pressure range of (0.36-1.4 MPa), with a range of superheated temperature differs than the corresponding saturation temperature by (10-60 oC) for each selected pressure. This work is also concerned with the possibility of producing of hot water for a pressure range of (0.36-1.4 MPa) with a temperature lower than the corresponding saturation temperature by (5 oC). The results show that the power produced reaches (1.4-3.3 MW). Also the hot water produced reaches 90000 kg/hr at operating pressure of 0.36MPa. The obtained results in this work are interesting since an elimination of thermal pollution by exhaust gases is accomplished. The available energy in these gases has been utilized to produce either superheated steam or hot water without consuming a conventional fuel.ntroductionI -

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Yang, Zhi Fu, Qing Yuan Meng, and Yu Hang Jing. "Cellular Automaton Simulation and Experimental Observation of the Dynamic Recrystallization of Titanium Alloy TC11 with Varied Strain Rates." Advanced Materials Research 476-478 (February 2012): 71–74. http://dx.doi.org/10.4028/www.scientific.net/amr.476-478.71.

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During the metal hot working process, the dislocation density will vary with strain and strain rate, and the variation of the dislocation density will affect the grain evolution subsequently. The cellular automaton (CA) method is an effective technique used to simulate the grain evolution of materials. In this work, a dynamic recrystallization (DRX) model of titanium alloy TC11 under varied strain rates was established by the use of cellular automaton method and verified by experimental observation. Two types of loading processes called “begin fast and then slowly” and “begin slowly and then fast” were simulated to investigate the titanium alloy TC11 grain evolution processes during hot working. The simulation results are in good coincidence with experimental data. Both cellular automaton simulation and experimental results show that the flow stresses and DRX transformation percentage during hot working process of the TC11 alloy are closely related not only to the strain rate but also to the loading sequence. Compared to the “begin slowly and then fast” loading sequence, the flow stress with the “begin fast and then slowly” loading sequence is relatively smaller under the same strain rates, and the DRX transformation percentage is relatively larger.

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Pavel, Ioan, Radu-Iulian Rădoi, Gabriela Matache, Ana-Maria Carla Popescu, and Ioan Caba. "Experimental research on a hot air generator working on the TLUD principle." E3S Web of Conferences 112 (2019): 01006. http://dx.doi.org/10.1051/e3sconf/201911201006.

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The current paper presents the processes of data acquisition and air temperature monitoring in the key points of a hot air generator working on the TLUD principle, which uses temperature sensors, a data acquisition board and an application developed in LabView that numerically and graphically displays temperature variation during burning. The results of the monitoring were obtained on an experimental model, developed by research scientists at INOE 2000-IHP. The data acquired is then used to establish the algorithm for opening the air supply valves for gasification and combustion air, in order to optimize combustion by maintaining the optimum temperature at the funnel.

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Terčelj, Milan, Matevž Fazarinc, and Goran Kugler. "Testing of thermal fatigue resistance of tools and rolls for hot working." Materials and Geoenvironment 64, no. 3 (September 26, 2017): 161–68. http://dx.doi.org/10.1515/rmzmag-2017-0010.

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Abstract In the present contribution two tests for thermal fatigue testing, which have been developed in our group, are presented. First test has provided internal cooling system of sample, while second has external cooling. For both tests heating and cooling of samples are computer guided that enables very reliable results of testing. The first test is more appropriate for testing the base material, i.e. roll cast irons, roll steels, tool steels. The second test is more appropriate for experiments that are aimed for selection of appropriate tool surface treatment, i.e. laser cladding, nitriding, coating, etc., and to compare and to achieve improved resistance against thermal fatigue of produced surface layers.

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Preisler, Dalibor, Miloš Janeček, Petr Harcuba, Jan Džugan, Kristýna Halmešová, Jaroslav Málek, Anna Veverková, and Josef Stráský. "The Effect of Hot Working on the Mechanical Properties of High Strength Biomedical Ti-Nb-Ta-Zr-O Alloy." Materials 12, no. 24 (December 17, 2019): 4233. http://dx.doi.org/10.3390/ma12244233.

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Beta titanium alloy Ti-35Nb-6Ta-7Zr-0.7O (wt%) was developed as a material intended for the manufacturing of a stem of a hip joint replacement. This alloy contains only biocompatible elements and possesses a very high yield strength already in the cast condition (900 MPa). However, the porosity, large grain size and chemical inhomogeneity reduce the fatigue performance below the limits required for utilization in the desired application. Two methods of hot working, die forging and hot rolling, were used for processing of this alloy. Microstructural evolution, tensile properties and fatigue performance of the hot worked material were investigated and compared to the cast material. Microstructural observations revealed that porosity is removed in all hot-worked conditions and the grain size is significantly reduced when the area reduction exceeds 70%. Static tensile properties were improved by both processing methods and ultimate tensile strength (UTS) of 1200 MPa was achieved. Fatigue results were more reproducible in the hot rolled material due to better microstructural homogeneity, but forging leads to an improved fatigue performance. Fatigue limit of 400 MPa was achieved in the die-forged condition after 70% of area reduction and in the hot rolled condition after 86% of area reduction.

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30

Qin, Kuan, Yongzheng Zhang, Zhougao Shen, Chengmao Cao, Zhengmin Wu, Jun Ge, Liangfei Fang, and Haijun Bi. "Investigating the Coupling Effect of High Pressure and Hot Air on External Friction Angle Based on Resistance Reduction Tests on Subsoiling Tillage Tools for Sandy Clay Loam." Agronomy 12, no. 11 (October 27, 2022): 2663. http://dx.doi.org/10.3390/agronomy12112663.

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Sandy clay loam has the characteristics of both sand and clay. Because of these characteristics, both frictional resistance and adhesive resistance occur between the soil and tillage tool. The combined effect of the two frictional forces increases the external friction angle between the soil and tillage tool, thus increasing the working resistance. To address this issue, this study investigated the coupling effect of high pressure and hot air on the external friction angle by using a self-developed device to measure the external friction angle. Test results showed that high-pressure air between the soil and tillage tool formed a high-pressure air curtain layer which acted as a lubricant, thereby reducing the external friction angle. The external friction angle decreased as the airflow pressure increased. The reduction in the moisture content of the subsoil to less than 30% by the high-pressure hot air reduced the resistance between the soil and tillage tool. The approach with the high-pressure hot air curtain was verified in tests on a subsoiling shovel; the working resistance of the shovel under high-pressure hot air was reduced by 14.8%, demonstrating that this approach was effective in reducing the working resistance of the shovel.

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31

Camarillo-Cisneros, J., R. Pérez-Bustamante, and R. Martínez-Sánchez. "Thermomechanical behavior of Al-Cu-Si commercial alloy modified with rare earths." Revista Mexicana de Física 66, no. 6 Nov-Dec (November 5, 2020): 782. http://dx.doi.org/10.31349/revmexfis.66.782.

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The effect of cerium/lanthanum rare earths on the microstructural and mechanical behavior of an automotive grade AA319 aluminum alloy was studied at room and hot working conditions. The microstructural results in the modified AA316 aluminum alloys showed that Ce/La additions formed stable micrometric phases at room and hot working conditions, whilst a reductionin the total area of the eutectic-Si phase of up to 75\% was observed in comparison with the reference alloy. The effect of the Ce/La addition in the aluminum alloys produced an increment in hardness and UTS under room temperature; however, their mechanical behavior was improved in hot working conditions. This improvement is attained to the presence of well dispersed Ce/La phases increasing the amount of the $\theta$'-phase (Al$_2$Cu) across the aluminum matrix. The $\theta$'-phase (Al$_2$Cu) interferes directly with crack diffusion of the solid in two crystallographic directions. Additionally, it was observed through transmission electron microscopy, that Ce/La presence alters the kinetics of precipitation in the formation of the coherent $\theta$-phase from the $\theta$'-phase.

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32

Li, Letian, Boyang Sun, Zhuqiang Hu, Jun Zhang, Song Gao, Haifeng Bian, and Jiansong Wu. "Heat Strain Evaluation of Power Grid Outdoor Workers Based on a Human Bioheat Model." International Journal of Environmental Research and Public Health 19, no. 13 (June 26, 2022): 7843. http://dx.doi.org/10.3390/ijerph19137843.

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Power grid outdoor workers are usually exposed to hot environments and could suffer the threats to occupational health and safety like heat strain and injury. In order to predict and assess the thermophysiological responses of grid workers in the heat, the clothing thermal insulation of grid worker ensembles was measured by a thermal manikin and a multi-segment human bioheat model was employed to evaluate the thermophysiological response parameters of grid workers such as core temperature, skin temperature and sweat loss. The results show that working in a hot environment can cause a obvious increase in core temperature and skin temperature of grid workers, and the acceptable maximum working time of grid workers varies greatly in different hot environments. A reasonable work organization strategy can effectively decrease the core temperature and sweat loss, increasing the duration of acceptable maximum working time for grid workers. This study is helpful to assess heat-related risks of grid workers and support power grid companies to rationalize work organization strategies and personal protection guidelines.

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33

Zhu, Hui, Mingle Hu, Songtao Hu, Haiying Wang, and Hua Su. "Evaluation of the cognitive performance under hot-humid environments using heart rate variability." E3S Web of Conferences 356 (2022): 03016. http://dx.doi.org/10.1051/e3sconf/202235603016.

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The human cognitive performance under hot and humid exposure is a critical issue for people working under hot and humid environments, for the considerations of both their health and safety. In order to find an indicator of the cognitive performance, the electrocardiogram (ECG) data were recorded continuously for 2.5 hours with portable Holter, when participants were exposed to 4 hot-humid environmental conditions and conducting different cognitive tests. The ECG data then were analysed to obtain the HRV indices that were used to establish a relationship with the cognitive test results. Temporal index pNN50 of HRV time domain indices was selected as a biomarker of the cognitive performance in this study. Results showed that the pNN50 responded significantly to the air temperature, while the influences of the cognitive tasks and the exposure time were found to be less significant. Meanwhile, the mean accuracy of the cognitive tasks was found to be positively related to the changes of mean pNN50, but a negatively related relationship between the mean reaction time and the mean pNN50 was observed. Furthermore, a positive relationship between the relative cognitive performance and the pNN50 was obtained, which meant that higher pNN50 responded to the higher cognitive performance. The potential reason could be ascribed to the changes in temperature-related allocation of the mental resources. And the low cognitive performance could be attributed to the rise of the mental fatigue due to the high sympathetic activities that corresponded to the low pNN50. The results revealed that the pNN50 could act as a biomarker of the cognitive performance under hot-humid exposure. The findings gave some implications to the real-time evaluation of the working performance and health of the people working under hot-humid environments.

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34

Bai, Ou, Masatoshi Nakamura, Yasuyuki Ikegami, and Haruo Uehara. "A Simulation Model for Hot Spring Thermal Energy Conversion Plant With Working Fluid of Binary Mixtures." Journal of Engineering for Gas Turbines and Power 126, no. 3 (July 1, 2004): 445–54. http://dx.doi.org/10.1115/1.1760526.

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Hot spring thermal energy conversion (STEC) is a system that converts heat energy into electricity using the temperature difference between hot spring water and sea/river water. This paper describes dynamic model construction for the transient performance of STEC plant, which uses a recently developed power cycle with binary mixtures as working fluid. The mathematical models were constructed based on thermodynamics and structural features of the power cycle for representing the timely dependent state variables of the working fluid. Confidence in the accuracy of the developed models has been established by comparison of the simulation results with those obtained experimentally in a pilot STEC plant.

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35

Lin, Jun Pin, Xiang Jun Xu, Jian Feng Gao, Yan Li Wang, Zhi Lin, and Guo Liang Chen. "Microstructure and Tensile Properties of Hot Worked High Nb Containing TiAl Alloy on Industrial Scale." Materials Science Forum 475-479 (January 2005): 785–88. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.785.

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. A hot working and its effect on the microstructure and tensile properties of Ti-45Al-9 (Nb, W, B, Y) alloy ingot on industrial scale were investigated. The results showed that the alloy has good workability in anα+γphase region. An ingot on industrial scale was successfully extruded followed by multi-step canned forging. The initial microstructure of the alloy is fine full lamellar (FL) microstructure. After hot working a sound pancake exhibiting a fine grain duplex (DP) microstructure with grain size about 20μm was obtained. The as-forged alloy has more balanced tensile properties than the small heats with similar composition and microstructure at both room and high temperatures.

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36

Moon, Ho Keun, Jae Seong Lee, Sun Joon Yoo, Man Soo Joun, and June Key Lee. "Hot Deformation Behavior of Bearing Steels." Journal of Engineering Materials and Technology 129, no. 3 (April 9, 2007): 349–55. http://dx.doi.org/10.1115/1.2744392.

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The material behaviors of two types of bearing steels at hot working conditions are investigated. Stress-strain curves at various temperatures (900–1300°C) and strain rates (1–50/s) are obtained by compression tests with a computer controlled servo-hydraulic Gleeble 3800 testing machine. Elongation and reduction of the area are also obtained by tensile tests with the Gleeble 1500 testing machine. Flow stresses are calculated from the experiments and are used to predict the temperature distribution and the metal flow of a workpiece during a multistage hot forging process of a bearing race. A rigid-thermoviscoplastic finite element method is applied. The experimental and numerical results are summarized to reveal the reasons for internal crack formation.

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37

Goode, K. B., J. Moore, and B. J. Roylance. "Plant machinery working life prediction method utilizing reliability and condition-monitoring data." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 214, no. 2 (May 1, 2000): 109–22. http://dx.doi.org/10.1243/0954408001530146.

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A recently developed condition-based maintenance model is described which utilizes reliability data combined with condition-monitoring and measurements to predict the remaining useful life of critical components in a hot strip steel mill. The results obtained from case studies are presented which indicate how the model can be used as part of a condition-based maintenance strategy.

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38

Liang, Ze De, and Shu Jie Wang. "Study of Power Generation System Based on Black Smokers." Applied Mechanics and Materials 535 (February 2014): 185–91. http://dx.doi.org/10.4028/www.scientific.net/amm.535.185.

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The OTEC system of the paper studying is different with the traditional OTEC system, which takes the marine geothermal energy (black smokers) as the heat source, takes cold seawater of deep sea as the cold source. The paper analyzes and calculates some parameters of open-circle system which uses water vapor as the working fluid and the closed-circle system which uses pure ammonia as the working fluid, those parameters include thermal efficiency, heat load of condenser and evaporator, pump power consumption, and the net power output. The results show that: with the closed-circle system which uses pure ammonia as the working fluid, the large power consumption of hot water pump is the biggest problem for the open-circle system, besides reducing the temperature of hot fluid and increasing the flash pressure are disadvantageous for open-circle system; but water vapor as the working fluid helps to reduce the load of condenser and evaporator, which is very advantageous for heat exchanger design.

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39

Hao, Wu, Hou Yingzhe, and Cui Lin. "Study on Temperature Distribution Characteristics of Condensate in Marine Condensator." E3S Web of Conferences 185 (2020): 01089. http://dx.doi.org/10.1051/e3sconf/202018501089.

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According to the structure and working principles of marine condensator, utilizing FLUNET, a numerical model of the flow field related to the hot well is established and the results were analysed. The flow field and temperature distribution characteristics of hot well with metal mesh and different heat flow distribution schemes are compared and analysed to improve the operation economy and safety of steam turbine units.

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40

Zhao, Deli, Liguo Ren, Yong Wang, Wei Wang, Zhe Zhu, and Wantang Fu. "Hot Deformation Behaviors of as Cast 321 Austenitic Stainless Steel." Metals 11, no. 8 (August 5, 2021): 1245. http://dx.doi.org/10.3390/met11081245.

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AISI 321 stainless steel has excellent resistance to intergranular corrosion and is generally used in nuclear power reactor vessels and other components. The as-cast and wrought structures are quite different in hot workability, so physical simulation, electron back-scatter diffraction, and hot processing maps were used to study the mechanical behavior and microstructure evolution of as-cast nuclear grade 321 stainless steel in the temperature range of 900–1200 °C and strain rate range of 0.01–10 s−1. The results showed that the flow curve presented work-hardening characteristics. The activation energy was calculated as 478 kJ/mol. The fraction of dynamic recrystallization (DRX) increased with increasing deformation temperature and decreasing strain rate. DRX grain size decreased with increasing Z value. Combining the hot working map and DRX state map, the suggested hot working window was 1000–1200 °C and 0.01–0.1 s−1. The main form of instability was necklace DRX. The nucleation mechanism of DRX was the migration of subgrains. The δ phase reduced the activation energy and promoted DRX nucleation of the tested steel.

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41

Bambach, Markus, Irina Sizova, Ole Geisen, and Omar Fergani. "Comparison of the Hot Working Behavior of Wrought, Selective Laser Melted and Electron Beam Melted Ti-6Al-4V." Materials Science Forum 941 (December 2018): 2030–36. http://dx.doi.org/10.4028/www.scientific.net/msf.941.2030.

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The production of high-temperature components is of great importance for the transport and energy sector. Forging of high-temperature alloys often requires expensive dies, multiple forming steps and leads to forged parts with large tolerances that require machining to create the final shape. Additive manufacturing (AM) offers the possibility to print the desired shapes directly as net-shape components. AM could provide the advantage of being more energy-efficient compared to forging if the energy contained in the machining scrap exceeds the energy needed for powder production and laser processing. However, the microstructure and performance of 3D-printed parts will not reach the level of forged material unless further processes such as hot-isostatic pressing are applied. Combining AM and metal forming could pave the way for new process chains with little material waste, reduced tooling costs and increased part performance. This study investigates the hot working properties and microstructure evolution of Ti–6Al–4V pre-forms made by selective laser melting and electron beam melting. The results show that both materials are hot workable in the as-built state. Due to its martensitic microstructure, the SLM material shows a lower activation energy for hot working than EBM and wrought material and a faster globularization during forming, which is beneficial for hot forming since it reduces the forming forces and tool loads.

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42

Donnini, Riccardo, Loredana Santo, and Vincenzo Tagliaferri. "Hot Drilling of Aluminium Matrix Composite." Materials Science Forum 678 (February 2011): 95–104. http://dx.doi.org/10.4028/www.scientific.net/msf.678.95.

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The aim of this paper is to investigate the behaviour in terms of drilling forces and roughness of Metal Matrix Composites (MMC) in hot drilling machining. In particular, Al2009/(SiC)w, Al6061/(SiC)w, and Al6061(Al2O3)p metal matrix composites were used, and the adopted temperature were in the range 20°C-160°C. A comparison with drilling at room temperature has been discussed. The results have shown the sensible influence of the working temperature on drilling forces and on surface material properties. In the case of Al2009/(SiC)w a minimum in the drilling forces has been found, making possible the dry machining and improving the cutting conditions. Instead, for Al6061/(SiC)W and Al6061(Al2O3)p in the used temperature range no minimum appears.

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43

Gautier, G., M. Faga, V. Tebaldo, G. Martra, and F. Cartasegna. "Study of Wear Phenomena of Coatings for Die-Casting." Applied Mechanics and Materials 302 (February 2013): 520–24. http://dx.doi.org/10.4028/www.scientific.net/amm.302.520.

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During high pressure die casting process, molten metal (aluminum) is injected with a die casting machine under considerable pressure into a steel mold or die to form products. Usually, during the process, the components can undergo several damages such as hot and abrasive wear, metal corrosion and plastic deformation. In order to increase the die life, a surface modification through the application of a Physical Vapour Deposition (PVD) coating can be done. This paper deals with the wear behaviour of a nanocomposite coating (AlSiTiN) deposited onto hot-working tool steel and onto a ion nitrided hot-working tool steel. The characterization includes: nanoindentation test, adhesion test, wear testing at high temperature and optical profilometry. Results showed that the nitriding step had a beneficial effect in terms of hardness, while adhesion between the coating and the substrate was reduced . The film exhibited good wear resistance, with adhesion phenomena as main mechanism.

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44

Sogut, O. S., and A. Durmayaz. "The effect of heat loss on the performance of a solar-driven heat engine." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 223, no. 7 (March 30, 2009): 1615–21. http://dx.doi.org/10.1243/09544062jmes1271.

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An optimal performance analysis of a parabolic-trough direct-steam-generation solar-driven Rankine cycle power plant at maximum power (MP) and under maximum power density (MPD) conditions is performed numerically to investigate the effects of heat loss from the heat source and working fluid. In this study, the ideal Rankine cycle of the solar-driven power plant is modified into an equivalent Carnot-like cycle with a finite-rate heat transfer. The main assumptions of this study include that: (a) the parabolic collector is the thermal reservoir at a high temperature, (b) the heat transfer process between the collector and the working fluid is through either radiation and convection simultaneously or radiation only, and (c) the heat transfer process from the working fluid to the low-temperature thermal reservoir is convection dominated. Comprehensive discussions on the effect of heat loss during the heat transfer process from the hot thermal reservoir to the working fluid in the parabolic-trough solar collector are provided. The major results of this study can be summarized as follows: (a) the working fluid temperature at the hot-side heat exchanger decreases remarkably whereas the working fluid temperature at the cold-side heat exchanger does not show any significant change with increasing heat loss, (b) the MP, MPD, and thermal efficiencies decrease with increasing heat loss, and (c) the effect of heat loss on the decrease of thermal efficiency increases when convection is the dominant heat transfer mode at the hot-side heat exchanger.

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45

Sanrutsadakorn, Apichat, Vitoon Uthaisangsuk, Surasak Suranuntchai, and Borpit Thossatheppitak. "Constitutive Modeling of Flow Behaviour of AISI 4340 Steel under Hot Working Conditions." Applied Mechanics and Materials 249-250 (December 2012): 863–69. http://dx.doi.org/10.4028/www.scientific.net/amm.249-250.863.

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Using compression test on a thermo-mechanical simulator/dilatometer, hot deformation behavior of steel AISI 4340 was studied in the temperature range of 850-1150°C and strain rate range of 0.01-10 s-1. The resulted true stress-strain curves exhibited a peak stress at low strain values, after which the flow stresses decreased monotonically until higher strains, representing the dynamic flow softening. The stress level decreased with increasing deformation temperature and decreasing strain rate. The material flow behavior at elevated temperatures was described using a Zener-Hollomon parameter with an exponent-type equation. Additionally, the model was modified by compensating strain rate parameter. The stress-strain responses for the investigated steel predicted by the proposed model agreed well with the experimental results. It was confirmed that the modified constitutive equations provided a more accurate prediction of the flow stress under hot working conditions for steel AISI 4340.

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46

Yong, Junhyeok, Junggyun Ham, Ohkyung Kwon, and Honghyun Cho. "Experimental Investigation of the Heat Transfer Characteristics of Plate Heat Exchangers Using LiBr/Water as Working Fluid." Energies 14, no. 20 (October 17, 2021): 6761. http://dx.doi.org/10.3390/en14206761.

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In this study, the heat exchange characteristics of water–LiBr solutions used as working fluid in a plate heat exchanger (PHE) were experimentally investigated at various concentrations. To analyze the heat transfer characteristics under LiBr/water conditions, a brazing type plate heat exchanger was installed, and the LiBr concentration on the high-temperature side was controlled at 56%, 58%, 60% and 60%. The results showed that the average heat transfer rate under water/water conditions was higher than that under LiBr/water conditions and the average heat transfer rate decreased as the LiBr concentration on the hot side increased. In addition, under both water/water and LiBr/water conditions, the average heat transfer rate and overall heat transfer coefficient increased as the mass flow rate of the working fluid on the hot side increased. When LiBr was used, the Reynolds number (Re) of LiBr on the hot side was more than nine times lower than that of water at the same mass flow rate owing to the influence of the increased viscosity. Based on the data obtained from the water/water and LiBr/water experiments, a correlation for predicting the Nusselt number (Nu) on the hot side in a wide range was developed.

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47

Matsumoto, Hiroaki, Hiroshi Yoneda, Kazuhisa Sato, Toyohiko J. Konno, Shingo Kurosu, Damien Fabrègue, Éric Maire, and Akihiko Chiba. "Microstructure and Mechanical Properties of α’ Martensite Type Ti-V-Al Alloy after Cold- or Hot Working Process." Key Engineering Materials 436 (May 2010): 171–77. http://dx.doi.org/10.4028/www.scientific.net/kem.436.171.

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Ti alloys are widely utilized for industrial applications due to their excellent mechanical properties combined with low density. In general, Ti alloys are classified as , + and  alloys, with further subdivision into near  and metastable  alloys. Quite recently, we have presented new type structural ’ martensite (H.C.P.) Ti alloys with low Young’s modulus, high strength and excellent ductility at room temperature. In this work, we examined the microstructure and mechanical properties of ’ martensite type Ti-V-Al alloy after cold- or hot working process. Then, we found that deformation behavior of ’ initial microstructure as compared with (+) initial microstructure was different based on the results of stress-strain curves and Processing Maps under the hot working process. Further, cold rolled ’ martensite microstructure exhibited the refined equiaxed dislocation cell structure, thereby resulting in high strength. This result suggests the new type deformation processing (for both cold- and hot work processing) utilizing ’ martensite in industrial Ti alloys.

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48

Han, Lin, Haoyu Zhang, Jun Cheng, Ge Zhou, Chuan Wang, and Lijia Chen. "Thermal Deformation Behavior of Ti-6Mo-5V-3Al-2Fe Alloy." Crystals 11, no. 10 (October 14, 2021): 1245. http://dx.doi.org/10.3390/cryst11101245.

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The Gleeble-3800 thermal simulation machine was used to perform hot compression experiments on a new type of β alloy, Ti-6Mo-5V-3Al-2Fe (wt.%), at temperatures of 700–900 °C, strain rates of 5 × 10−1 to 5 × 10−4 s−1, and total strain of 0.7. Transmission and EBSD techniques were used to observe the microstructure. The results show that the deformation activation energy of the alloy was 356.719 KJ/mol, and dynamic recrystallization occurred during the hot deformation. The higher the deformation temperature was, the more obvious the dislocations that occurred and the more sufficient the dynamic recrystallization that occurred, but the effect of strain rate was the opposite. When the deformation temperature was higher than the phase transition point, the recrystallized grains clearly grew up. The calculated strain rate sensitivity index of the alloy was 0.14–0.29. The constitutive equation of hot deformation of Ti-6Mo-5V-3Al-2Fe alloy was established by using the Arrhenius hyperbolic sine equation. The dynamic DMM hot working diagram with the strain of 0.7 was constructed. The relatively good hot working area of the alloy was determined to be the deformation temperature of 700–720 °C and 0.0041–0.0005 s−1.

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Mikielewicz, Dariusz, and Jarosław Mikielewicz. "Utilisation of bleed steam heat to increase the upper heat source temperature in low-temperature ORC." Archives of Thermodynamics 32, no. 3 (December 1, 2011): 57–70. http://dx.doi.org/10.2478/v10173-011-0013-5.

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Utilisation of bleed steam heat to increase the upper heat source temperature in low-temperature ORC In the paper presented is a novel concept to utilize the heat from the turbine bleed to improve the quality of working fluid vapour in the bottoming organic Rankine cycle (ORC). That is a completely novel solution in the literature, which contributes to the increase of ORC efficiency and the overall efficiency of the combined system of the power plant and ORC plant. Calculations have been accomplished for the case when available is a flow rate of low enthalpy hot water at a temperature of 90 °C, which is used for preliminary heating of the working fluid. That hot water is obtained as a result of conversion of exhaust gases in the power plant to the energy of hot water. Then the working fluid is further heated by the bleed steam to reach 120 °C. Such vapour is subsequently directed to the turbine. In the paper 5 possible working fluids were examined, namely R134a, MM, MDM, toluene and ethanol. Only under conditions of 120 °C/40 °C the silicone oil MM showed the best performance, in all other cases the ethanol proved to be best performing fluid of all. Results are compared with the "stand alone" ORC module showing its superiority.

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Fojt-Dymara, Gabriela, Marek Opiela, and Wojciech Borek. "Susceptibility of High-Manganese Steel to High-Temperature Cracking." Materials 15, no. 22 (November 18, 2022): 8198. http://dx.doi.org/10.3390/ma15228198.

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Tests were carried out on two high-Mn steels: 27Mn-4Si-2Al-Nb with Nb microaddition and 24Mn-3Si-1.5Al-Nb-Ti with Nb and Ti microadditions. High-manganese austenitic steels, due to their good strength and plastic properties belong to the AHSS (Advanced High-Strength Steel) group and are used in the automotive industry. The main difficulties faced during the casting of the steel and hot working are hot cracks, which can appear in the surface of the ingot. Cracks on the edges of the sheet after hot rolling are the reason for cutting the edges of the sheet and increasing production costs and material losses. The main reason for the formation of hot cracks is the decrease in metal ductility in the high-temperature brittleness range (HTBR). The width of the HTBR depends on mechanical properties and microstructural factors, i.e., non-metallic inclusions or intermetallic phases at austenite grain boundaries. In this paper, a hot tensile test was performed. The research was performed on the GLEEBLE 3800 thermomechanical simulator. This test allows us to determine the width of the high-temperature brittleness range (HTBR), the Nil Strength Temperature (NST), the Nil Ductility Temperature (NDT), and the Ductility Recovery Temperature (DRT). Hot ductility was determined from the value of the reduction in area R(A). The obtained results make it possible to determine the temperature of the beginning of hot working from the tested high-Mn steels. Fractographic research enabled us to define mechanisms of hot cracking. It was found that hot cracks form as a result of disruptions in the liquid film on crystals’ boundaries.

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Journal articles on the topic 'Hot working results'

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