Jialie Liu, Junjie Xu, Chuntao Ge, Jie Pang, Weiliang Jin, Geir Martin Haarberg, Saijun Xiao
To enhance the anticorrosion properties of molybdenum metal in liquid zinc, this study successfully fabricated TiB2 coatings on molybdenum substrates via the molten salt electrophoretic deposition technique and investigated their corrosion resistance in molten zinc. Initially, TiB2 nanoparticles with a size ranging from 50 to 150 nm were synthesized using the borothermal reduction method in a molten NaF-AlF3 bath at 1238 K. Subsequently, the electrophoretic deposition experiment was conducted under a cell voltage of 1.2 V (i.e., 0.6 V/cm) for a duration of 1 h in the melt containing TiB2 nanoparticles, resulting in a uniform, continuous, and compact TiB2 coating (35 μm thick) on the molybdenum substrate. Moreover, the corrosion resistance of the TiB2-coated molybdenum metal to molten zinc was tested through continuous immersion. After 120 h of immersion, the TiB2 coating showed no signs of cracking or peeling off, successfully protecting the molybdenum metal substrate from corrosion by molten zinc. The results confirm that the molten salt electrophoretic deposition technique can be used to prepare TiB2 coatings with good resistance to molten zinc corrosion on molybdenum metal.
{"title":"Stability Investigation of TiB2 Coatings in Molten Zinc Fabricated by Electrophoretic Deposition in Molten Salts","authors":"Jialie Liu, Junjie Xu, Chuntao Ge, Jie Pang, Weiliang Jin, Geir Martin Haarberg, Saijun Xiao","doi":"10.3390/met14090981","DOIUrl":"https://doi.org/10.3390/met14090981","url":null,"abstract":"To enhance the anticorrosion properties of molybdenum metal in liquid zinc, this study successfully fabricated TiB2 coatings on molybdenum substrates via the molten salt electrophoretic deposition technique and investigated their corrosion resistance in molten zinc. Initially, TiB2 nanoparticles with a size ranging from 50 to 150 nm were synthesized using the borothermal reduction method in a molten NaF-AlF3 bath at 1238 K. Subsequently, the electrophoretic deposition experiment was conducted under a cell voltage of 1.2 V (i.e., 0.6 V/cm) for a duration of 1 h in the melt containing TiB2 nanoparticles, resulting in a uniform, continuous, and compact TiB2 coating (35 μm thick) on the molybdenum substrate. Moreover, the corrosion resistance of the TiB2-coated molybdenum metal to molten zinc was tested through continuous immersion. After 120 h of immersion, the TiB2 coating showed no signs of cracking or peeling off, successfully protecting the molybdenum metal substrate from corrosion by molten zinc. The results confirm that the molten salt electrophoretic deposition technique can be used to prepare TiB2 coatings with good resistance to molten zinc corrosion on molybdenum metal.","PeriodicalId":18461,"journal":{"name":"Metals","volume":"2 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142184958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Iwona Sulima, Michał Stępień, Paweł Hyjek, Sonia Boczkal, Remigiusz Kowalik
This study aimed to investigate the physical, mechanical, corrosion, and tribological properties of Cu-based composites with varying zirconium diboride content. The composites were successfully consolidated using spark plasma sintering (SPS) at temperatures of 850 °C and 950 °C and a pressure of 35 MPa. The effect of the ZrB2 content and the sintering temperature on the properties of the Cu-based composites was investigated. Scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and X-ray diffraction were used to analyse microstructure evolution in copper matrix composites. Microhardness tests were used to evaluate mechanical properties. Wear behaviour was evaluated using a ball-on-disc method. Corrosion properties were estimated on electrochemical tests, such as potentiodynamic polarisation. The results demonstrated an enhancement in the density and porosity of the composites as the sintering temperature increased. A uniform dispersion of ZrB2 was observed in the copper matrix for all composites. With an increase in the content of the ZrB2 reinforcement phase, there was an increase in microhardness and an improvement in the wear resistance of the sintered composites. A reduction in densification and corrosion resistance of Cu-based composites was observed with increasing ZrB2 content.
{"title":"Mechanical, Corrosion and Wear Characteristics of Cu-Based Composites Reinforced with Zirconium Diboride Consolidated by SPS","authors":"Iwona Sulima, Michał Stępień, Paweł Hyjek, Sonia Boczkal, Remigiusz Kowalik","doi":"10.3390/met14090974","DOIUrl":"https://doi.org/10.3390/met14090974","url":null,"abstract":"This study aimed to investigate the physical, mechanical, corrosion, and tribological properties of Cu-based composites with varying zirconium diboride content. The composites were successfully consolidated using spark plasma sintering (SPS) at temperatures of 850 °C and 950 °C and a pressure of 35 MPa. The effect of the ZrB2 content and the sintering temperature on the properties of the Cu-based composites was investigated. Scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and X-ray diffraction were used to analyse microstructure evolution in copper matrix composites. Microhardness tests were used to evaluate mechanical properties. Wear behaviour was evaluated using a ball-on-disc method. Corrosion properties were estimated on electrochemical tests, such as potentiodynamic polarisation. The results demonstrated an enhancement in the density and porosity of the composites as the sintering temperature increased. A uniform dispersion of ZrB2 was observed in the copper matrix for all composites. With an increase in the content of the ZrB2 reinforcement phase, there was an increase in microhardness and an improvement in the wear resistance of the sintered composites. A reduction in densification and corrosion resistance of Cu-based composites was observed with increasing ZrB2 content.","PeriodicalId":18461,"journal":{"name":"Metals","volume":"35 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142184976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The reactor pressure vessel (RPV) is a critical barrier in nuclear power plants, but its embrittlement during service poses a significant safety challenge. This study investigated the effects of Cu-enriched clusters on the mechanical and magnetic properties of Fe-0.9 wt.%Cu model alloys through thermal aging. Using Vickers hardness tests, Magnetic Barkhausen Noise (MBN) detection, and Atom Probe Tomography (APT), the study aimed to establish a quantitative correlation between MBN signals, Vickers hardness, and Cu-enriched clusters, facilitating the non-destructive testing of RPV embrittlement. Experimental results showed that the hardness and MBN parameters (RMS and Vpp values) changed significantly with aging time. The hardness increased rapidly in the early stage (under-aged), followed by a plateau and then a decreasing trend (over-aged). In contrast, MBN parameters decreased initially and then increased. APT analysis revealed that Cu-enriched clusters increase in size to 4.60 nm and coalesced during aging, with their number density peaking to 3.76 × 1023 m−3 before declining. An inverse linear correlation was found between MBN signals and the combined factor Nd2Rg (product of the number density squared and the mean radius of Cu-enriched clusters). This correlation was consistent across both under-aged and over-aged states, suggesting that MBN signals can serve as applicable indicators for the non-destructive evaluation of RPV steel embrittlement.
{"title":"Magnetic Indicator for Evaluating Cu Clustering and Hardening Effect in RPV Model Alloy","authors":"Wenqing Jia, Qiwei Quan, Wangjie Qian, Chuang Bian, Chaoliang Xu, Jian Yin, Bin Li, Yuanfei Li, Minyu Fan, Xiangbing Liu, Haitao Wang","doi":"10.3390/met14090973","DOIUrl":"https://doi.org/10.3390/met14090973","url":null,"abstract":"The reactor pressure vessel (RPV) is a critical barrier in nuclear power plants, but its embrittlement during service poses a significant safety challenge. This study investigated the effects of Cu-enriched clusters on the mechanical and magnetic properties of Fe-0.9 wt.%Cu model alloys through thermal aging. Using Vickers hardness tests, Magnetic Barkhausen Noise (MBN) detection, and Atom Probe Tomography (APT), the study aimed to establish a quantitative correlation between MBN signals, Vickers hardness, and Cu-enriched clusters, facilitating the non-destructive testing of RPV embrittlement. Experimental results showed that the hardness and MBN parameters (RMS and Vpp values) changed significantly with aging time. The hardness increased rapidly in the early stage (under-aged), followed by a plateau and then a decreasing trend (over-aged). In contrast, MBN parameters decreased initially and then increased. APT analysis revealed that Cu-enriched clusters increase in size to 4.60 nm and coalesced during aging, with their number density peaking to 3.76 × 1023 m−3 before declining. An inverse linear correlation was found between MBN signals and the combined factor Nd2Rg (product of the number density squared and the mean radius of Cu-enriched clusters). This correlation was consistent across both under-aged and over-aged states, suggesting that MBN signals can serve as applicable indicators for the non-destructive evaluation of RPV steel embrittlement.","PeriodicalId":18461,"journal":{"name":"Metals","volume":"11 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142184975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Boštjan Arh, Franc Tehovnik, Franci Vode, Bojan Podgornik
This research was focused on the effect of Ti and S content on the formation of non-metallic inclusions and their influence on the mechanical properties and machinability of low-carbon ferritic–pearlitic steels. An analysis and classification of the non-metallic inclusions were carried out. The tensile strength and impact toughness were determined from samples taken in the rolling direction. Machinability investigations were carried out on a CNC turning machine and by analyzing the surface roughness. TiO-TiN inclusions are present in steels with an increased Ti content. In these steels, the hardness, tensile strength, and cutting forces increase with a higher proportion of Ti. In the second group of steels with increased contents of S, Al, and Ca, MnS and CaO-Al2O3-MnS non-metallic inclusions are formed. As the S content increases, the tensile strength and cutting forces decrease, while the impact toughness increases. In steels with added Ti, the machining is more difficult, but a finer surface is achieved after turning, while a higher S content results in an increased fraction of softer sulfide inclusions, which reduce the cutting forces but also result in a reduced surface quality.
这项研究的重点是 Ti 和 S 含量对非金属夹杂物形成的影响及其对低碳铁素体-珠光体钢机械性能和切削性的影响。对非金属夹杂物进行了分析和分类。从轧制方向取样测定了拉伸强度和冲击韧性。在数控车床上通过分析表面粗糙度进行了切削性研究。在钛含量增加的钢中存在 TiO-TiN 杂质。这些钢材的硬度、抗拉强度和切削力随着钛含量的增加而提高。在第二组 S、Al 和 Ca 含量增加的钢中，形成了 MnS 和 CaO-Al2O3-MnS 非金属夹杂物。随着 S 含量的增加，抗拉强度和切削力降低，而冲击韧性增加。在添加了 Ti 的钢中，加工难度增加，但车削后的表面更精细，而 S 含量越高，较软的硫化物夹杂物的比例越大，从而降低了切削力，但也导致表面质量下降。
{"title":"Effect of Ti and S Content on the Properties and Machinability of Low-Carbon Ferritic–Pearlitic Steel","authors":"Boštjan Arh, Franc Tehovnik, Franci Vode, Bojan Podgornik","doi":"10.3390/met14090977","DOIUrl":"https://doi.org/10.3390/met14090977","url":null,"abstract":"This research was focused on the effect of Ti and S content on the formation of non-metallic inclusions and their influence on the mechanical properties and machinability of low-carbon ferritic–pearlitic steels. An analysis and classification of the non-metallic inclusions were carried out. The tensile strength and impact toughness were determined from samples taken in the rolling direction. Machinability investigations were carried out on a CNC turning machine and by analyzing the surface roughness. TiO-TiN inclusions are present in steels with an increased Ti content. In these steels, the hardness, tensile strength, and cutting forces increase with a higher proportion of Ti. In the second group of steels with increased contents of S, Al, and Ca, MnS and CaO-Al2O3-MnS non-metallic inclusions are formed. As the S content increases, the tensile strength and cutting forces decrease, while the impact toughness increases. In steels with added Ti, the machining is more difficult, but a finer surface is achieved after turning, while a higher S content results in an increased fraction of softer sulfide inclusions, which reduce the cutting forces but also result in a reduced surface quality.","PeriodicalId":18461,"journal":{"name":"Metals","volume":"12 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142184979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Witold Malec, Joanna Kulasa, Anna Brudny, Anna Hury, Bartlomiej Adamczyk, Ryszard Rzepecki, Robert Sekula, Grzegorz Kmita, Andrzej Rybak
This article presents a comparative analysis of the crucial physical properties of electrically conductive components made of pure copper, produced by various additive manufacturing technologies such as binder jetting (BJ) and direct metal laser sintering (DMLS). The comparison concerned the assessment of critical parameters important from the application point of view, such as: electrical conductivity, hardness, yield point, microstructure and the occurrence of internal material defects. Same-sized components made in a conventional casting and subtractive method (machining) were used as a reference material. Comprehensive tests and the comparison of a wide range of parameters allowed us to determine that among the selected methods, printing using the DMLS technique allowed for obtaining arcing contact with mechanical and electrical parameters very similar to the reference element. Therefore, the obtained results showed the possibility of using the copper elements made by additive manufacturing for the switching and protection devices used in electrification and energy distribution industrial sectors.
{"title":"Comparative Studies of the Properties of Copper Components: Conventional vs. Additive Manufacturing Technologies","authors":"Witold Malec, Joanna Kulasa, Anna Brudny, Anna Hury, Bartlomiej Adamczyk, Ryszard Rzepecki, Robert Sekula, Grzegorz Kmita, Andrzej Rybak","doi":"10.3390/met14090975","DOIUrl":"https://doi.org/10.3390/met14090975","url":null,"abstract":"This article presents a comparative analysis of the crucial physical properties of electrically conductive components made of pure copper, produced by various additive manufacturing technologies such as binder jetting (BJ) and direct metal laser sintering (DMLS). The comparison concerned the assessment of critical parameters important from the application point of view, such as: electrical conductivity, hardness, yield point, microstructure and the occurrence of internal material defects. Same-sized components made in a conventional casting and subtractive method (machining) were used as a reference material. Comprehensive tests and the comparison of a wide range of parameters allowed us to determine that among the selected methods, printing using the DMLS technique allowed for obtaining arcing contact with mechanical and electrical parameters very similar to the reference element. Therefore, the obtained results showed the possibility of using the copper elements made by additive manufacturing for the switching and protection devices used in electrification and energy distribution industrial sectors.","PeriodicalId":18461,"journal":{"name":"Metals","volume":"158 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142184978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
NbRu has a potential as a high-temperature shape-memory alloy (HTSMA) because it has a martensitic transformation temperature above 1000 °C. However, its shape-memory properties could be improved for consideration in the aerospace and automotive industry. The unsatisfactory shape-memory properties could be associated with the presence of a brittle tetragonal L10 martensitic phase. Therefore, in an attempt to modify the transformation path from B2→L10 in preference of either B2→orthorhombic or B2→monoclinic (MCL), an addition of B2 phase stabiliser, titanium (Ti), has been considered in this study to partially substitute niobium (Nb) atoms. The ab initio calculations have been conducted to investigate the effect of Ti addition on the thermodynamic, elastic, and electronic properties of the Nb50−xTixRu50 in B2 and L10 phases. The results showed that the B2 and L10 phases had comparable stability with increasing Ti content. The simulated data presented here was sufficient for the selection of suitable compositions that would allow the L10 phase to be engineered out. The said composition was identified within 15–30 at.% Ti. These compositions have a potential to be considered when designing alloys for structural application at high temperatures above 200 °C.
NbRu 具有高温形状记忆合金（HTSMA）的潜力，因为它的马氏体转变温度高于 1000 ℃。不过，它的形状记忆特性还需要改进，以便用于航空航天和汽车工业。形状记忆性能不理想可能与脆性四方 L10 马氏体相的存在有关。因此，为了改变 B2→L10 的转变路径，优先选择 B2→ 正交或 B2→ 单斜（MCL）相，本研究考虑添加 B2 相稳定剂钛（Ti），以部分替代铌（Nb）原子。我们进行了 ab initio 计算，以研究添加 Ti 对 B2 和 L10 相 Nb50-xTixRu50 的热力学、弹性和电子特性的影响。结果表明，随着钛含量的增加，B2 和 L10 相的稳定性相当。此处提供的模拟数据足以帮助选择合适的成分，从而将 L10 相工程化。上述成分的钛含量在 15-30% 之间。在设计用于 200 °C 以上高温环境下的结构合金时，可以考虑使用这些成分。
{"title":"First-Principle Study on Tailoring the Martensitic Transformation of B2 Nb50−xTixRu50 Shape-Memory Alloy for Structural Applications","authors":"Duduzile Nkomo, Yu-Nien Shen, Roelf Mostert, Yoko Yamabe-Mitarai, Maje Phasha","doi":"10.3390/met14090976","DOIUrl":"https://doi.org/10.3390/met14090976","url":null,"abstract":"NbRu has a potential as a high-temperature shape-memory alloy (HTSMA) because it has a martensitic transformation temperature above 1000 °C. However, its shape-memory properties could be improved for consideration in the aerospace and automotive industry. The unsatisfactory shape-memory properties could be associated with the presence of a brittle tetragonal L10 martensitic phase. Therefore, in an attempt to modify the transformation path from B2→L10 in preference of either B2→orthorhombic or B2→monoclinic (MCL), an addition of B2 phase stabiliser, titanium (Ti), has been considered in this study to partially substitute niobium (Nb) atoms. The ab initio calculations have been conducted to investigate the effect of Ti addition on the thermodynamic, elastic, and electronic properties of the Nb50−xTixRu50 in B2 and L10 phases. The results showed that the B2 and L10 phases had comparable stability with increasing Ti content. The simulated data presented here was sufficient for the selection of suitable compositions that would allow the L10 phase to be engineered out. The said composition was identified within 15–30 at.% Ti. These compositions have a potential to be considered when designing alloys for structural application at high temperatures above 200 °C.","PeriodicalId":18461,"journal":{"name":"Metals","volume":"4 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142184990","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anok Babu Nagaram, Giulio Maistro, Erik Adolfsson, Yu Cao, Eduard Hryha, Lars Nyborg
Vanadis 4E (V4E) is a powder metallurgical cold work tool steel predominantly used in application with demand for wear resistance, high hardness, and toughness. It is of interest to have a processing route that enables full density starting from clean gas-atomized powder allowing component shaping capabilities. This study presents a process involving freeze granulation of powder to facilitate compaction by means of cold isostatic pressing, followed by sintering to allow for capsule-free hot isostatic pressing (HIP) and subsequent heat treatments of fully densified specimens. The sintering stage has been studied in particular, and it is shown how sintering in pure nitrogen at 1150 °C results in predominantly closed porosity, while sintering at 1200 °C gives near full density. Microstructural investigation shows that vanadium-rich carbonitride (MX) is formed as a result of the nitrogen uptake during sintering, with coarser appearance for the higher temperature. Nearly complete densification, approximately 7.80 ± 0.01 g/cm3, was achieved after sintering at 1200 °C, and after sintering at 1150 °C, followed by capsule-free HIP, hardening, and tempering. Irrespective of processing once the MX is formed, the nitrogen is locked into this phase and the austenite is stabilised, which means any tempering tends to result in a mixture of austenite and tempered martensite, the former being predominate during the sequential tempering, whereas martensite formation during cooling from austenitization temperatures becomes limited.
Vanadis 4E (V4E) 是一种粉末冶金冷作工具钢，主要用于需要耐磨性、高硬度和韧性的应用领域。人们希望有一种加工方法，能从清洁的气体原子化粉末开始，实现全密度加工，从而使部件具有成型能力。本研究提出了一种工艺，包括粉末冷冻造粒，以便通过冷等静压法进行压实，然后进行烧结，以实现无胶囊热等静压（HIP），并对完全致密化的试样进行后续热处理。我们特别对烧结阶段进行了研究，结果表明，在 1150 °C 的纯氮环境下烧结主要会产生闭合孔隙，而在 1200 °C 的环境下烧结则会产生接近全密度的孔隙。微观结构研究表明，烧结过程中的氮吸收形成了富钒氮化碳（MX），温度越高，MX 越粗大。在 1200 °C 烧结和 1150 °C 烧结后，经过无胶囊 HIP、淬火和回火，几乎实现了完全致密化，密度约为 7.80 ± 0.01 g/cm3。无论采用何种加工工艺，MX 一旦形成，氮就会被锁定在这一相中，奥氏体就会稳定下来，这意味着任何回火都会产生奥氏体和回火马氏体的混合物，前者在连续回火过程中占主导地位，而在从奥氏体化温度冷却过程中形成的马氏体则会受到限制。
{"title":"Full Density Powder Metallurgical Cold Work Tool Steel through Nitrogen Sintering and Capsule-Free Hot Isostatic Pressing","authors":"Anok Babu Nagaram, Giulio Maistro, Erik Adolfsson, Yu Cao, Eduard Hryha, Lars Nyborg","doi":"10.3390/met14080914","DOIUrl":"https://doi.org/10.3390/met14080914","url":null,"abstract":"Vanadis 4E (V4E) is a powder metallurgical cold work tool steel predominantly used in application with demand for wear resistance, high hardness, and toughness. It is of interest to have a processing route that enables full density starting from clean gas-atomized powder allowing component shaping capabilities. This study presents a process involving freeze granulation of powder to facilitate compaction by means of cold isostatic pressing, followed by sintering to allow for capsule-free hot isostatic pressing (HIP) and subsequent heat treatments of fully densified specimens. The sintering stage has been studied in particular, and it is shown how sintering in pure nitrogen at 1150 °C results in predominantly closed porosity, while sintering at 1200 °C gives near full density. Microstructural investigation shows that vanadium-rich carbonitride (MX) is formed as a result of the nitrogen uptake during sintering, with coarser appearance for the higher temperature. Nearly complete densification, approximately 7.80 ± 0.01 g/cm3, was achieved after sintering at 1200 °C, and after sintering at 1150 °C, followed by capsule-free HIP, hardening, and tempering. Irrespective of processing once the MX is formed, the nitrogen is locked into this phase and the austenite is stabilised, which means any tempering tends to result in a mixture of austenite and tempered martensite, the former being predominate during the sequential tempering, whereas martensite formation during cooling from austenitization temperatures becomes limited.","PeriodicalId":18461,"journal":{"name":"Metals","volume":"192 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141931628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pengcheng Xiao, Yuxin Jin, Liguang Zhu, Chao Wang, Rong Zhu
The materials charged into a converter comprise molten iron and scrap steel. Adjusting the ratio by increasing scrap steel and decreasing molten iron is a steelmaking raw material strategy designed specifically for China’s unique circumstances, with the goal of lowering carbon emissions. To maintain the converter tapping temperature, scrap must be preheated to provide additional heat. Current scrap preheating predominantly utilizes horizontal tunnel furnaces, resulting in high energy consumption and low efficiency. To address these issues, a three-stage shaft furnace for scrap preheating was designed, and Fluent software was used to compare and study the preheating efficiency of the new three-stage furnace against the traditional horizontal furnace under various operational conditions. Initially, a three-dimensional transient multi-field coupling model was developed for two scrap preheating scenarios, examining the effects of both furnaces on scrap surface and core temperatures across varying preheating durations and gas velocities. Simulation results indicate that, under identical gas heat consumption conditions, scrap achieves markedly higher final temperatures in the shaft furnace compared to the horizontal furnace, with scrap surface and core temperatures increasing notably with extended preheating times and higher gas velocities, albeit with a gradual decrease in heating rate as the scrap temperature rises. At a gas velocity of 9 m/s and a preheating time of 600 s, the shaft furnace achieves the highest waste heat utilization rate for scrap, with scrap averaging 325 °C higher than in the horizontal furnace, absorbing an additional 202 MJ of heat per ton. In the horizontal preheating furnace, scrap steel exhibits a heat absorption efficiency of 35%, whereas in the vertical furnace, this efficiency increases notably to 63%. In the vertical furnace, the waste heat recovery rate of scrap steel reaches 57%.
{"title":"Comparative Study of Heat Transfer Simulation and Effects of Different Scrap Steel Preheating Methods","authors":"Pengcheng Xiao, Yuxin Jin, Liguang Zhu, Chao Wang, Rong Zhu","doi":"10.3390/met14080913","DOIUrl":"https://doi.org/10.3390/met14080913","url":null,"abstract":"The materials charged into a converter comprise molten iron and scrap steel. Adjusting the ratio by increasing scrap steel and decreasing molten iron is a steelmaking raw material strategy designed specifically for China’s unique circumstances, with the goal of lowering carbon emissions. To maintain the converter tapping temperature, scrap must be preheated to provide additional heat. Current scrap preheating predominantly utilizes horizontal tunnel furnaces, resulting in high energy consumption and low efficiency. To address these issues, a three-stage shaft furnace for scrap preheating was designed, and Fluent software was used to compare and study the preheating efficiency of the new three-stage furnace against the traditional horizontal furnace under various operational conditions. Initially, a three-dimensional transient multi-field coupling model was developed for two scrap preheating scenarios, examining the effects of both furnaces on scrap surface and core temperatures across varying preheating durations and gas velocities. Simulation results indicate that, under identical gas heat consumption conditions, scrap achieves markedly higher final temperatures in the shaft furnace compared to the horizontal furnace, with scrap surface and core temperatures increasing notably with extended preheating times and higher gas velocities, albeit with a gradual decrease in heating rate as the scrap temperature rises. At a gas velocity of 9 m/s and a preheating time of 600 s, the shaft furnace achieves the highest waste heat utilization rate for scrap, with scrap averaging 325 °C higher than in the horizontal furnace, absorbing an additional 202 MJ of heat per ton. In the horizontal preheating furnace, scrap steel exhibits a heat absorption efficiency of 35%, whereas in the vertical furnace, this efficiency increases notably to 63%. In the vertical furnace, the waste heat recovery rate of scrap steel reaches 57%.","PeriodicalId":18461,"journal":{"name":"Metals","volume":"17 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141931626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Longitudinal crack defects are a frequent occurrence on the surface of thin slabs during the high-speed continuous casting process. Therefore, this study undertakes a detailed analysis of the solidification characteristics of hyper-peritectic steel thin slabs. By establishing a three-dimensional heat transfer numerical model of the thin slab, the formation mechanism of longitudinal cracks caused by uneven growth of the initial shell is determined. Based on the mechanism of longitudinal crack formation, by adjusting the performance parameters of the mold flux, the contradiction between the heat transfer control and lubrication improvement of the mold flux is fully coordinated, further reducing the incidence of longitudinal cracks on the surface of the casting thin slab. The results show that, using the optimized mold flux, the basicity increases from 1.60 to 1.68, the F- mass fraction increases from 10.67% to 11.22%, the Na2O mass fraction increases from 4.35% to 5.28%, the Li2O mass fraction increases from 0.68% to 0.75%, and the carbon mass fraction reduces from 10.86% to 10.47%. The crystallization performance and rheological properties of the mold flux significantly improve, reducing the heat transfer performance while ensuring the lubrication ability of the molten slag. After optimizing the mold flux, a surface detection system was used to statistically analyze the longitudinal cracks on the surface of the casting thin slab. The proportion of longitudinal cracks (crack length/steel coil length, where each coil produced is about 32 m long) on the surface of the thin slab decreases from 0.056% to 0.031%, and the surface quality of the thin slab significantly improves.
{"title":"Analysis of Longitudinal Cracking and Mold Flux Optimization in High-Speed Continuous Casting of Hyper-Peritectic Steel Thin Slabs","authors":"Zhipeng Yuan, Liguang Zhu, Xingjuan Wang, Kaixuan Zhang","doi":"10.3390/met14080909","DOIUrl":"https://doi.org/10.3390/met14080909","url":null,"abstract":"Longitudinal crack defects are a frequent occurrence on the surface of thin slabs during the high-speed continuous casting process. Therefore, this study undertakes a detailed analysis of the solidification characteristics of hyper-peritectic steel thin slabs. By establishing a three-dimensional heat transfer numerical model of the thin slab, the formation mechanism of longitudinal cracks caused by uneven growth of the initial shell is determined. Based on the mechanism of longitudinal crack formation, by adjusting the performance parameters of the mold flux, the contradiction between the heat transfer control and lubrication improvement of the mold flux is fully coordinated, further reducing the incidence of longitudinal cracks on the surface of the casting thin slab. The results show that, using the optimized mold flux, the basicity increases from 1.60 to 1.68, the F- mass fraction increases from 10.67% to 11.22%, the Na2O mass fraction increases from 4.35% to 5.28%, the Li2O mass fraction increases from 0.68% to 0.75%, and the carbon mass fraction reduces from 10.86% to 10.47%. The crystallization performance and rheological properties of the mold flux significantly improve, reducing the heat transfer performance while ensuring the lubrication ability of the molten slag. After optimizing the mold flux, a surface detection system was used to statistically analyze the longitudinal cracks on the surface of the casting thin slab. The proportion of longitudinal cracks (crack length/steel coil length, where each coil produced is about 32 m long) on the surface of the thin slab decreases from 0.056% to 0.031%, and the surface quality of the thin slab significantly improves.","PeriodicalId":18461,"journal":{"name":"Metals","volume":"49 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141931629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study investigates active filling friction stir repair (AF-FSR) and passive filling friction stir repair (PF-FSR) for repairing AISI 304 stainless steel sheets, focusing on addressing the challenges posed by high melting point metals. The research involved repairing overlapping 2 mm thick sheets with pre-drilled holes of 2, 4, and 6 mm diameters, simulating broken components. Various process parameters, including rotational speed, dwell time, and the use of metal fillers, were tested to evaluate their impact on repair quality. The results demonstrated that PF-FSR provided superior mechanical strength to AF-FSR, particularly for larger pre-hole diameters. PF-FSR achieved higher shear tension strength due to better defect filling and reduced void formation, with shear tension strengths exceeding 25 kN for larger pre-holes and lower variability in strength measurements. AF-FSR was less effective for larger pre-holes, resulting in significant voids and reduced strength. Microstructural analysis revealed that PF-FSR facilitated more efficient material mixing and filling, minimizing unrepaired regions. However, excessive rotational speeds and dwell times in PF-FSR led to deformation and flash formation, highlighting the need for optimal parameter selection. Although further studies are needed, this study confirms the feasibility of FSR techniques for repairing small defects in AISI 304 steels, offering valuable insights for sustainable manufacturing practices in industries such as automotive and aerospace, where efficient and reliable repair methods are critical.
{"title":"Active and Passive Filling Stir Repairing of AISI 304 Alloy","authors":"Vincenzo Lunetto, Dario Basile, Valentino Razza, Pasquale Russo Spena","doi":"10.3390/met14080911","DOIUrl":"https://doi.org/10.3390/met14080911","url":null,"abstract":"This study investigates active filling friction stir repair (AF-FSR) and passive filling friction stir repair (PF-FSR) for repairing AISI 304 stainless steel sheets, focusing on addressing the challenges posed by high melting point metals. The research involved repairing overlapping 2 mm thick sheets with pre-drilled holes of 2, 4, and 6 mm diameters, simulating broken components. Various process parameters, including rotational speed, dwell time, and the use of metal fillers, were tested to evaluate their impact on repair quality. The results demonstrated that PF-FSR provided superior mechanical strength to AF-FSR, particularly for larger pre-hole diameters. PF-FSR achieved higher shear tension strength due to better defect filling and reduced void formation, with shear tension strengths exceeding 25 kN for larger pre-holes and lower variability in strength measurements. AF-FSR was less effective for larger pre-holes, resulting in significant voids and reduced strength. Microstructural analysis revealed that PF-FSR facilitated more efficient material mixing and filling, minimizing unrepaired regions. However, excessive rotational speeds and dwell times in PF-FSR led to deformation and flash formation, highlighting the need for optimal parameter selection. Although further studies are needed, this study confirms the feasibility of FSR techniques for repairing small defects in AISI 304 steels, offering valuable insights for sustainable manufacturing practices in industries such as automotive and aerospace, where efficient and reliable repair methods are critical.","PeriodicalId":18461,"journal":{"name":"Metals","volume":"57 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141931631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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