Abstract In fire investigations, the most important aspect is determining the presence of a liquid accelerant at the fire scene. The presence or absence of accelerants is critical evidence during trials for fire cases. Upon exposure to high temperatures, metallic substances undergo oxidation, which can be imparted by accelerants in the fire. Oxides and substrates found on metal surfaces offer valuable information on the characteristics of fire, including exposure temperature, duration, and involvement of a liquid accelerant. In this study, we investigated the oxidation behavior of copper at high temperatures in a simulated flame environment using ethanol combustion. After oxidation, the morphological, oxide phase composition, and microstructural features of specimens were characterized by observation, X-ray diffraction, X-ray photoelectron energy spectroscopy, transmission electron microscopy, and scanning electron microscopy with energy-dispersive spectroscopic analysis. The elemental carbon with a hexagonal structure deposited on the sample’s surface was found, which may be incomplete combustion and the chemical composition of ethanol. Copper has a preferred orientation of oxide on the (111) crystal plane, which differs from oxidation in ordinary hot air that is related to the large Coulomb force of the (111) crystal plane. Hot air convection due to combustion may cause large areas of oxide layer on the copper surface to crack and peel. Oxide properties and surface state of metals strongly depended on oxidation duration, temperature, and atmosphere. These data shall offer reference information for determining the presence of combustion accelerants at fire scenes.
{"title":"Application on oxidation behavior of metallic copper in fire investigation","authors":"Xie Dongbai, H. Hao, Duo Shuwang, Li Qiang","doi":"10.1515/htmp-2022-0014","DOIUrl":"https://doi.org/10.1515/htmp-2022-0014","url":null,"abstract":"Abstract In fire investigations, the most important aspect is determining the presence of a liquid accelerant at the fire scene. The presence or absence of accelerants is critical evidence during trials for fire cases. Upon exposure to high temperatures, metallic substances undergo oxidation, which can be imparted by accelerants in the fire. Oxides and substrates found on metal surfaces offer valuable information on the characteristics of fire, including exposure temperature, duration, and involvement of a liquid accelerant. In this study, we investigated the oxidation behavior of copper at high temperatures in a simulated flame environment using ethanol combustion. After oxidation, the morphological, oxide phase composition, and microstructural features of specimens were characterized by observation, X-ray diffraction, X-ray photoelectron energy spectroscopy, transmission electron microscopy, and scanning electron microscopy with energy-dispersive spectroscopic analysis. The elemental carbon with a hexagonal structure deposited on the sample’s surface was found, which may be incomplete combustion and the chemical composition of ethanol. Copper has a preferred orientation of oxide on the (111) crystal plane, which differs from oxidation in ordinary hot air that is related to the large Coulomb force of the (111) crystal plane. Hot air convection due to combustion may cause large areas of oxide layer on the copper surface to crack and peel. Oxide properties and surface state of metals strongly depended on oxidation duration, temperature, and atmosphere. These data shall offer reference information for determining the presence of combustion accelerants at fire scenes.","PeriodicalId":12966,"journal":{"name":"High Temperature Materials and Processes","volume":"41 1","pages":"216 - 223"},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44977448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The thermodynamics of the phase equilibria in the Al–Fe–Zn–O quaternary system was studied using the calculation of phase diagrams method to understand the oxidation behavior of the Zn bath surface during galvanizing process. The thermodynamic parameters for the Gibbs energies of the different constituent phases in the binary and ternary systems relevant to this quaternary system were taken mainly from previous studies. In this study, the thermodynamic assessment of the Al2O3–ZnO system was carried out based on the available experimental data, and some modifications to the thermodynamic model and/or parameters for the Fe–Zn–O ternary system were made to maintain consistency with the thermodynamic descriptions of other binary and ternary systems, making up the Al–Fe–Zn–O quaternary system adopted in this study. The calculated results on the ternary and quaternary systems generally agreed with the available experimental results on phase equilibria. The set of thermodynamic parameters enabled us to calculate the phase equilibria in the Al–Fe–Zn–O quaternary system over the entire composition and temperature ranges.
{"title":"Thermodynamic calculation of phase equilibria in the Al–Fe–Zn–O system","authors":"N. Matsumoto, T. Tokunaga","doi":"10.1515/htmp-2022-0249","DOIUrl":"https://doi.org/10.1515/htmp-2022-0249","url":null,"abstract":"Abstract The thermodynamics of the phase equilibria in the Al–Fe–Zn–O quaternary system was studied using the calculation of phase diagrams method to understand the oxidation behavior of the Zn bath surface during galvanizing process. The thermodynamic parameters for the Gibbs energies of the different constituent phases in the binary and ternary systems relevant to this quaternary system were taken mainly from previous studies. In this study, the thermodynamic assessment of the Al2O3–ZnO system was carried out based on the available experimental data, and some modifications to the thermodynamic model and/or parameters for the Fe–Zn–O ternary system were made to maintain consistency with the thermodynamic descriptions of other binary and ternary systems, making up the Al–Fe–Zn–O quaternary system adopted in this study. The calculated results on the ternary and quaternary systems generally agreed with the available experimental results on phase equilibria. The set of thermodynamic parameters enabled us to calculate the phase equilibria in the Al–Fe–Zn–O quaternary system over the entire composition and temperature ranges.","PeriodicalId":12966,"journal":{"name":"High Temperature Materials and Processes","volume":"41 1","pages":"605 - 620"},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45468927","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chao Feng, K. Dong, R. Zhu, Tao Lin, Jianfeng Dong, Tao Xia, Xin Ren
Abstract O2 mixed with CO2 gas has been successfully applied in converter smelting; however, up to now, there have been few studies regarding the jet characteristics of the mixed injection of the swirl oxygen lance nozzle and the influence of different ambient temperature conditions on jet characteristics compared with common nozzles. In this study, Fluent software was used to simulate the jet characteristics of a four-hole common nozzle and a four-hole swirl nozzle under four different ambient temperature conditions to inject 95% O2 + 5% CO2 and analyze the influence of different ambient temperatures on nozzle-jet characteristics. The results show that with an increase in the ambient temperature, the jet-axis velocity and nozzle centerline speed increase. Under the same distance condition, the distance between the maximum radial velocity point of the jet and the centerline of the nozzle becomes larger, with a velocity greater than that of the swirl nozzle. However, the influence of the ambient temperature on the offset of the jet centerline is small. With an increase in the ambient temperature and distance, the jet-axis temperature increases and the temperature of the nozzle centerline decreases. The research results can provide a theoretical reference for the optimal design of a CO2 + O2 swirl oxygen lance nozzle.
{"title":"Effect of ambient temperature on the jet characteristics of a swirl oxygen lance with mixed injection of CO2 + O2","authors":"Chao Feng, K. Dong, R. Zhu, Tao Lin, Jianfeng Dong, Tao Xia, Xin Ren","doi":"10.1515/htmp-2022-0239","DOIUrl":"https://doi.org/10.1515/htmp-2022-0239","url":null,"abstract":"Abstract O2 mixed with CO2 gas has been successfully applied in converter smelting; however, up to now, there have been few studies regarding the jet characteristics of the mixed injection of the swirl oxygen lance nozzle and the influence of different ambient temperature conditions on jet characteristics compared with common nozzles. In this study, Fluent software was used to simulate the jet characteristics of a four-hole common nozzle and a four-hole swirl nozzle under four different ambient temperature conditions to inject 95% O2 + 5% CO2 and analyze the influence of different ambient temperatures on nozzle-jet characteristics. The results show that with an increase in the ambient temperature, the jet-axis velocity and nozzle centerline speed increase. Under the same distance condition, the distance between the maximum radial velocity point of the jet and the centerline of the nozzle becomes larger, with a velocity greater than that of the swirl nozzle. However, the influence of the ambient temperature on the offset of the jet centerline is small. With an increase in the ambient temperature and distance, the jet-axis temperature increases and the temperature of the nozzle centerline decreases. The research results can provide a theoretical reference for the optimal design of a CO2 + O2 swirl oxygen lance nozzle.","PeriodicalId":12966,"journal":{"name":"High Temperature Materials and Processes","volume":"41 1","pages":"635 - 649"},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43221835","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xin Li, Chang-yu Zhou, X. Pan, L. Chang, Lei Lu, Guodong Zhang, F. Xue, Yanfen Zhao
Abstract The effect of hold time with 0, 20, and 40 s on in-phase thermomechanical fatigue (TMF) behavior and life of P92 steel is investigated in this study. TMF tests are carried out under mechanical strain control with strain amplitudes of 0.4 0.4 , 0.6 0.6 , and 0.8 % 0.8text{%} , and temperature range of 550–650°C which is closely relevant to the operating condition in power plant. TMF tests are performed in a mechanical strain ratio of R = − 1 R=-1 and cycle time of 120 s. The fatigue life variation follows the sequence of N f 0 s < N f 20 s < N f 40 s {N}_{text{f}}^{0hspace{.1em}text{s}}lt {N}_{text{f}}^{20hspace{.1em}text{s}}lt {N}_{text{f}}^{40hspace{.1em}text{s}} for the same mechanical strain amplitude. In addition, the influence of hold time on fatigue life decreases with the increasing strain amplitude. A continuous softening can be observed from the cyclic stress response under all test conditions. Fractographic and microstructural tests indicate that the fracture surfaces are characterized by a multi-source cracking initiation and an oxidation phenomenon. Furthermore, a modified Ostergren model is used to predict the fatigue life and achieves a good predicted result.
摘要0、20和40的保持时间的影响 研究了P92钢的同相热机械疲劳行为和寿命。TMF试验是在机械应变控制下进行的，应变幅度分别为0.4、0.6、0.6和0.8%，温度范围为550–650°C，这与发电厂的运行条件密切相关。TMF试验是在R=−1 R=-1的机械应变比和120的循环时间下进行的 s.疲劳寿命变化遵循N f 0 s
{"title":"In-phase thermomechanical fatigue studies on P92 steel with different hold time","authors":"Xin Li, Chang-yu Zhou, X. Pan, L. Chang, Lei Lu, Guodong Zhang, F. Xue, Yanfen Zhao","doi":"10.1515/htmp-2022-0024","DOIUrl":"https://doi.org/10.1515/htmp-2022-0024","url":null,"abstract":"Abstract The effect of hold time with 0, 20, and 40 s on in-phase thermomechanical fatigue (TMF) behavior and life of P92 steel is investigated in this study. TMF tests are carried out under mechanical strain control with strain amplitudes of 0.4 0.4 , 0.6 0.6 , and 0.8 % 0.8text{%} , and temperature range of 550–650°C which is closely relevant to the operating condition in power plant. TMF tests are performed in a mechanical strain ratio of R = − 1 R=-1 and cycle time of 120 s. The fatigue life variation follows the sequence of N f 0 s < N f 20 s < N f 40 s {N}_{text{f}}^{0hspace{.1em}text{s}}lt {N}_{text{f}}^{20hspace{.1em}text{s}}lt {N}_{text{f}}^{40hspace{.1em}text{s}} for the same mechanical strain amplitude. In addition, the influence of hold time on fatigue life decreases with the increasing strain amplitude. A continuous softening can be observed from the cyclic stress response under all test conditions. Fractographic and microstructural tests indicate that the fracture surfaces are characterized by a multi-source cracking initiation and an oxidation phenomenon. Furthermore, a modified Ostergren model is used to predict the fatigue life and achieves a good predicted result.","PeriodicalId":12966,"journal":{"name":"High Temperature Materials and Processes","volume":"41 1","pages":"57 - 68"},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43851993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract A novel hot-work die steel 5CrNiMoVNb is developed by optimizing the alloy composition of 5CrNiMoV steel. Thermal stability tests were carried out to compare the hardness evolution of the two steel types. The hardness reduction of 5CrNiMoVNb at 600 and 650°C was only 4.3HRC and 9.6HRC, while that of 5CrNiMoV steel at the same condition was as large as 6.5HRC and 17.5HRC, respectively, which suggests that the thermal stability of the 5CrNiMoVNb steel is more excellent. The thermal stability mechanism of 5CrNiMoVNb was studied based on microstructure analyses and thermodynamic calculations. This suggests that high tempering temperatures cause the coarsening of some carbides and suppress the recovery and recrystallization of the martensite matrix, which is the main reason for the slight decrease in the thermal stability. For the adding of the medium and strong carbide-forming elements, the carbides in 5CrNiMoVNb steel are mainly MC and M23C6 with low coarsening rate coefficient, and the content of these two carbides is almost constant below 670°C. The fine MC and M23C6 carbides showed strong pinning and dragging effects on the dislocations and suppressed martensite recovery and recrystallization. Therefore, the novel hot-work die steel showed excellent tempering softening resistance and thermal stability than 5CrNiMoV steel.
{"title":"Investigation into the thermal stability of a novel hot-work die steel 5CrNiMoVNb","authors":"Zhiqiang Hu, Kaikun Wang","doi":"10.1515/htmp-2022-0031","DOIUrl":"https://doi.org/10.1515/htmp-2022-0031","url":null,"abstract":"Abstract A novel hot-work die steel 5CrNiMoVNb is developed by optimizing the alloy composition of 5CrNiMoV steel. Thermal stability tests were carried out to compare the hardness evolution of the two steel types. The hardness reduction of 5CrNiMoVNb at 600 and 650°C was only 4.3HRC and 9.6HRC, while that of 5CrNiMoV steel at the same condition was as large as 6.5HRC and 17.5HRC, respectively, which suggests that the thermal stability of the 5CrNiMoVNb steel is more excellent. The thermal stability mechanism of 5CrNiMoVNb was studied based on microstructure analyses and thermodynamic calculations. This suggests that high tempering temperatures cause the coarsening of some carbides and suppress the recovery and recrystallization of the martensite matrix, which is the main reason for the slight decrease in the thermal stability. For the adding of the medium and strong carbide-forming elements, the carbides in 5CrNiMoVNb steel are mainly MC and M23C6 with low coarsening rate coefficient, and the content of these two carbides is almost constant below 670°C. The fine MC and M23C6 carbides showed strong pinning and dragging effects on the dislocations and suppressed martensite recovery and recrystallization. Therefore, the novel hot-work die steel showed excellent tempering softening resistance and thermal stability than 5CrNiMoV steel.","PeriodicalId":12966,"journal":{"name":"High Temperature Materials and Processes","volume":"41 1","pages":"353 - 363"},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47572819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Low-carbon, green and intelligent production is urgently needed in China’s iron and steel industry. Accurate prediction of liquid steel composition at the end of basic oxygen furnace (BOF) plays an important role in promoting high-quality, high-efficiency and stable production in steelmaking process. A prediction model based on the principal component analysis (PCA) – genetic algorithm (GA) – back propagation (BP) neural network is proposed for BOF end-point P and O contents of liquid steel. PCA is used to eliminate the correlation between the factors, and the obtained principal components are seen as input parameters of the BP neural network; then, GA is employed to optimize the initialized weights and thresholds of the BP neural network. The flux composition and bottom blowing are considered in the input variables. The results indicate that the prediction accuracy of the single output model is higher than that of the dual output model. The root-mean-square error of P content between predicted and actual values is 0.0015%, and that of O content is 0.0049%. Therefore, the model can provide a good reference for BOF end-point control.
{"title":"Prediction model of BOF end-point P and O contents based on PCA–GA–BP neural network","authors":"Zhao Liu, S. Cheng, P. Liu","doi":"10.1515/htmp-2022-0050","DOIUrl":"https://doi.org/10.1515/htmp-2022-0050","url":null,"abstract":"Abstract Low-carbon, green and intelligent production is urgently needed in China’s iron and steel industry. Accurate prediction of liquid steel composition at the end of basic oxygen furnace (BOF) plays an important role in promoting high-quality, high-efficiency and stable production in steelmaking process. A prediction model based on the principal component analysis (PCA) – genetic algorithm (GA) – back propagation (BP) neural network is proposed for BOF end-point P and O contents of liquid steel. PCA is used to eliminate the correlation between the factors, and the obtained principal components are seen as input parameters of the BP neural network; then, GA is employed to optimize the initialized weights and thresholds of the BP neural network. The flux composition and bottom blowing are considered in the input variables. The results indicate that the prediction accuracy of the single output model is higher than that of the dual output model. The root-mean-square error of P content between predicted and actual values is 0.0015%, and that of O content is 0.0049%. Therefore, the model can provide a good reference for BOF end-point control.","PeriodicalId":12966,"journal":{"name":"High Temperature Materials and Processes","volume":"41 1","pages":"505 - 513"},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46541284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Based on CAFE theory and KGT model, the twin-roll strip casting mathematical model was established to solve the dendrite growth and solidification of T2 copper alloy in the molten pool. The influence mechanism of casting temperature, heat transfer, and other technological conditions on the microstructure of strip was analyzed. The results showed that the liquid metal formed 35 µm chilling layer after touching the rollers, and the layer was consisted of a high number of small and equiaxed crystals. Then some grains would appear close to the newly chilling layer, and grow toward the core of molten pool competitively. The dominant grains mainly grew along the 〈001〉 orientation into columnar crystals, and the rest grains that grew out of alignment were eliminated gradually. The number of grains declined, and the radius of columnar grains became coarsening. The Kiss point is a key factor for solidification structure, and the lower location of the Kiss point could limit the growth spaces of columnar crystals, which refined the grains.
{"title":"Numerical and experimental research on solidification of T2 copper alloy during the twin-roll casting","authors":"Zheng-feng Lv, Zhengjun Sun, Zhichao Hou, Zhou-Yi Yang, Xiliang Zhang, Yinping Shi","doi":"10.1515/htmp-2022-0012","DOIUrl":"https://doi.org/10.1515/htmp-2022-0012","url":null,"abstract":"Abstract Based on CAFE theory and KGT model, the twin-roll strip casting mathematical model was established to solve the dendrite growth and solidification of T2 copper alloy in the molten pool. The influence mechanism of casting temperature, heat transfer, and other technological conditions on the microstructure of strip was analyzed. The results showed that the liquid metal formed 35 µm chilling layer after touching the rollers, and the layer was consisted of a high number of small and equiaxed crystals. Then some grains would appear close to the newly chilling layer, and grow toward the core of molten pool competitively. The dominant grains mainly grew along the 〈001〉 orientation into columnar crystals, and the rest grains that grew out of alignment were eliminated gradually. The number of grains declined, and the radius of columnar grains became coarsening. The Kiss point is a key factor for solidification structure, and the lower location of the Kiss point could limit the growth spaces of columnar crystals, which refined the grains.","PeriodicalId":12966,"journal":{"name":"High Temperature Materials and Processes","volume":"41 1","pages":"1 - 7"},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47281031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-01DOI: 10.1615/hightempmatproc.2022046575
N. Batrak, Nikita Kopaleishvili, M. Kutyrev
{"title":"Experimental analysis of pulse injectors used in the creation of plasma beams","authors":"N. Batrak, Nikita Kopaleishvili, M. Kutyrev","doi":"10.1615/hightempmatproc.2022046575","DOIUrl":"https://doi.org/10.1615/hightempmatproc.2022046575","url":null,"abstract":"","PeriodicalId":12966,"journal":{"name":"High Temperature Materials and Processes","volume":"7 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87980545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Herein, the surface decarburization and oxidation characteristics of Cr–Mo cold heading steel are investigated via optical microscopy, scanning electron microscopy, and electron backscatter diffraction under different temperatures. Furthermore, the competitive mechanisms of decarburization and oxidation are analyzed. The results indicate that the heating temperature considerably affects the decarburization and oxidation characteristics of the steel sample. With an increase in the temperature, the depth of the total decarburization layer increases. The fully decarburized layer is prominent between 750 and 850°C and culminates at 800°C. The oxide thickness parabolically increases, and Cr2O3 is present, which inhibits oxidation. Between 700 and 950°C, the oxidation weight gain is slow. The main structure of the oxide scale is the dense Fe3O4 layer, inhibiting decarburization. The oxidation rate increases at 950°C, and the proportion of loose FeO layer in the oxide scale exceeds 66%, promoting decarburization. At >1,000°C, the surface decarburization and oxidation rate simultaneously increase.
{"title":"Characterization of surface decarburization and oxidation behavior of Cr–Mo cold heading steel","authors":"Ji-Long Chen, G. Feng, Yaxu Zheng, Jian Ma, Peng Lin, Ningtao Wang, Honglei Ma, Jian Zheng","doi":"10.1515/htmp-2022-0237","DOIUrl":"https://doi.org/10.1515/htmp-2022-0237","url":null,"abstract":"Abstract Herein, the surface decarburization and oxidation characteristics of Cr–Mo cold heading steel are investigated via optical microscopy, scanning electron microscopy, and electron backscatter diffraction under different temperatures. Furthermore, the competitive mechanisms of decarburization and oxidation are analyzed. The results indicate that the heating temperature considerably affects the decarburization and oxidation characteristics of the steel sample. With an increase in the temperature, the depth of the total decarburization layer increases. The fully decarburized layer is prominent between 750 and 850°C and culminates at 800°C. The oxide thickness parabolically increases, and Cr2O3 is present, which inhibits oxidation. Between 700 and 950°C, the oxidation weight gain is slow. The main structure of the oxide scale is the dense Fe3O4 layer, inhibiting decarburization. The oxidation rate increases at 950°C, and the proportion of loose FeO layer in the oxide scale exceeds 66%, promoting decarburization. At >1,000°C, the surface decarburization and oxidation rate simultaneously increase.","PeriodicalId":12966,"journal":{"name":"High Temperature Materials and Processes","volume":"41 1","pages":"531 - 541"},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41585967","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zheng-feng Lv, Zhou-Yi Yang, Jian-Yu Zhang, Xueting Li, P. Ji, Qiangfang Zhou, Xiliang Zhang, Yinping Shi
Abstract Based on the three-dimensional field of molten pool and twin-roll strip casting experiments, this work verified the cracking mechanism of the strip by establishing mathematical model and rolling experiments. The results showed that due to the instability of the thermophysical field of the molten pool and the inconsistency of kiss curve height, the newly solidified strip will undergo incompatible deformation through the rolling. The stress concentration will appear around the large reduction area and then form slip bands. When plastic strain exceeds the limit of the metal, the oblique cracks will appear in the slip bands periodically or completely penetrate the strip. In addition, tensile cracks could also be produced by incompatible deformation. Therefore, keeping the uniformity and stability of the thermal physical field in molten pool is the key factor to restrain cracks.
{"title":"Numerical simulation and experimental research on cracking mechanism of twin-roll strip casting","authors":"Zheng-feng Lv, Zhou-Yi Yang, Jian-Yu Zhang, Xueting Li, P. Ji, Qiangfang Zhou, Xiliang Zhang, Yinping Shi","doi":"10.1515/htmp-2022-0251","DOIUrl":"https://doi.org/10.1515/htmp-2022-0251","url":null,"abstract":"Abstract Based on the three-dimensional field of molten pool and twin-roll strip casting experiments, this work verified the cracking mechanism of the strip by establishing mathematical model and rolling experiments. The results showed that due to the instability of the thermophysical field of the molten pool and the inconsistency of kiss curve height, the newly solidified strip will undergo incompatible deformation through the rolling. The stress concentration will appear around the large reduction area and then form slip bands. When plastic strain exceeds the limit of the metal, the oblique cracks will appear in the slip bands periodically or completely penetrate the strip. In addition, tensile cracks could also be produced by incompatible deformation. Therefore, keeping the uniformity and stability of the thermal physical field in molten pool is the key factor to restrain cracks.","PeriodicalId":12966,"journal":{"name":"High Temperature Materials and Processes","volume":"41 1","pages":"694 - 701"},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42117297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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