共查询到20条相似文献,搜索用时 125 毫秒
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近年来.随着结构及工程机械(如履带式推土机、岩层推土机等)逐渐增加,所用的环境日益恶劣,要求使用的钢板具有超高强度和良好的韧性。为满足这些要求,日本JFE公司开发了两种超高强度钢:JFE—HYD960LE和JFE—HYD1100LE,两种钢的最小屈服强度分别为960MPa和1100MPa。经过形变热处理、快速加热回火可细化晶粒,改善细渗碳体均匀分布。形变热处理通过淬火加工硬化奥氏体来实现, 相似文献
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为了稳定亚温淬火工艺与工业化生产,通过力学性能分析及显微组织观察,对比了正火+亚温淬火+回火、在线淬火+亚温淬火+回火、离线淬火+亚温淬火+回火3种热处理工艺对690 MPa级海洋工程用钢板组织性能的影响。结果表明,采用离线淬火+亚温淬火+回火工艺结果最理想,能够大幅度提高钢板的低温冲击性能和伸长率。同时,还能够获得较低的屈强比,断口形貌全部为韧窝,呈明显的韧性断裂,而且随着亚温保温时间的增加,强度逐渐提高,当保温时间达到30 min以后,强度及条片状铁素体基本不发生变化;采用直接淬火态+亚温淬火+回火虽然可以保证高强度低屈强比,但是冲击功表现较为离散,稳定性欠佳,断口形貌为混合型,以韧性断裂为主;采用正火态+亚温淬火+回火工艺效果最差,尤其是不能保证钢板低温韧性,断口形貌全部为解理,呈明显的脆性断裂,其中片条状铁素体形貌是决定优良低温冲击性能的关键因素。 相似文献
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中厚钢板热处理技术及设备发展概况 总被引:1,自引:0,他引:1
概述了中厚板热处理工艺及设备的发展应用情况,介绍了近年来开发成功的中厚板新型高强度均匀化冷却技术——Super OLAC及在线热处理技术——HOP(在线淬火及回火工艺)。同时,介绍了国内当前中厚板热处理线的建设和设备配置情况以及国产首套具有自主知识产权的中厚板辊式淬火机设备及应用情况。随着国内中厚板企业冶炼和轧制装备及技术水平的日益提高,中厚板轧后辅助工序和技术,尤其是提高钢板强度和性能等级的轧后热处理技术,已成为国内中厚板生产厂家提高产品档次和竞争力的必然选择。 相似文献
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基于合金设计制备出2种低合金试验热轧板钢,在采用水淬+盐浴回火的淬火-分配-回火(Q-P-T)工艺处理后,达到了屈服强度900MPa和伸长率15%的设计指标,为后期自行设计的单道次穿水淬火冷却装置用于热轧板的Q-P-T工艺工程可行性的研究奠定了基础。X射线衍射、扫描电镜和透射电镜的微观组织分析表明:与传统的淬火回火(Q&T)工艺相比,Q-P-T先进高强度钢中位错型板条马氏体基体及其内弥散分布的合金碳化物贡献于高的强度,板条马氏体间的薄片状奥氏体贡献于优良的塑性。此外,还进一步探讨了Q-P-T工艺中残余奥氏体的作用和多道次穿水淬火冷却装置用于不同厚度热轧板在线Q-P-T处理的可行性。 相似文献
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针对不同热处理工艺对EH690级特厚钢板心部组织和性能的影响展开研究,结果表明:经过在线淬火+回火处理,钢板心部的强度能够满足性能要求,但冲击韧性极差,显微组织为粗大粒状贝氏体和珠光体的混合组织;一次淬火+回火处理后,强度下降明显,冲击性能有所改善,但是不能满足-40℃低温冲击吸收功≥69 J的要求,存在混晶,组织为粒状贝氏体+少量马氏体;二次淬火+回火处理后,强度整体偏高,冲击功均值满足标准要求,强韧性匹配程度一般,晶粒细化明显,马氏体含量占比增多。通过调整回火温度,最终获得晶粒细小均匀、以高密度位错回火索氏体为主的组织,钢板心部强韧性匹配较好。 相似文献
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The improvement of hole-expansion properties for medium carbon steels by ultra fast cooling (UFC) after hot strip rolling was investigated. It was found that finely dispersed spherical cementite could be formed after ultra fast cooling, coiling and annealing treatment. Tensile strength of the steel after annealing was measured to be about 440 MPa. During hole-expansion test, cracks were observed in the edge region around the punched hole because necking or cracking took place when tangential elongation exceeded the forming limit. Cracks were mainly formed by the coalescence of micro-voids. Fine and homogeneous microstructure comprised of ferrite and spheroidized cementite could increase elongation values of the tested sheets by suppressing the combination of the adjacent micro-voids, resulting in the improved hole-expansion property. 相似文献
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Jun CHEN Xin-jun SHEN Feng-qin JI Shuai TANG Zhen-yu LIU Guo-dong WANG 《钢铁研究学报(英文版)》2013,20(9):86-92
Effects of annealing time on microstructure of cold-rolled niobium-titanium bearing micro-alloyed steel strips were investigated by optical microscopy, scanning electron microscopy, electron back-scatter diffraction (EBSD) and transmission electron microscopy. The complete recrystallization annealing temperature of 670 °C and complete annealing time of 9 min were determined using Vickers-hardness testing and EBSD analysis. The ferrite microstructure with spheric cementite particles and nano-scale precipitates of Nb(C, N) in matrix was obtained. The kinetics of the ferrite grain growth is lowered due to ferrite grain boundaries pinned by the cementite particles, so the ferrite grain size of 5. 5 μm remains unchanged among the annealing time ranging from 9 to 30 min. In addition, the strength of tested steel also keeps unchanged with the increase of annealing time. The higher yield strength of approximately 420 MPa can be obtained by grain refinement and precipitation hardening and the higher elongation of approximately 40% and work-hardening exponent of approximately 0. 2 can be gained due to grain refinement and presence of cementite particles, indicating that the balance of strength, ductility and forming property is realized. 相似文献
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为满足490—590MPa级厚钢板使用中对焊接大线能量化、高强度厚板化、高韧性化的要求.开发出新的超越了已有技术界限的热影响区细晶高韧性化技术.从而可以得到韧性良好的热影响区。该技术旨在明显抑制熔合线附近热影响区内奥氏体晶粒长大,使高温热稳定性优良的氧化物或硫化物在钢中微细分散。通过显著细化奥氏体晶粒来微细化热影响区组织。技术要点是确定工业方法,使含有适量镁或钙、尺寸为数十纳米至数百纳米的钢中氧化物或硫化物密而分散。该技术适用于建筑、造船、海洋工程结构和石油管线用厚钢板,在确保焊接钢结构安全可靠基础上,提高焊接热影响区的韧性。 相似文献
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Herein, the microstructure and mechanical properties of a high-carbon bainitic steel treated by long-time bainitic austempering and short-time austempering plus tempering processes are compared. The multiphase microstructures are characterized by dilatometry, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy to correlate with mechanical properties. Results show that although long-time austempering treatment can reduce the volume fraction of brittle martensite, no significant improvement is observed in fracture damage resistance. Besides, the cementite is prone to precipitation from the austenite at the later period of the long-time austempering process. The cementite precipitation in austenite decreases the carbon content in retained austenite (RA) and consequently reduces the mechanical stability of RA. In contrast, the cementite has not been able to precipitate from austenite after short-time austempering treatment, whereas the martensite is softened and the stability of RA is improved during subsequent tempering. Therefore, excellent mechanical properties are obtained in the samples treated by short-time austempering plus tempering process: ultimate tensile strength, 1489 MPa, yield strength, 1014 MPa, total elongation, 33.2%, and the product of strength and elongation (PSE) of 48.4 GPa%, where PSE is increased by 27% compared with the sample after long-time bainitic austempering. 相似文献
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利用拉-拉疲劳试验方法对比研究了51CrV4钢不同奥氏体化温度下试样的疲劳性能,并采用扫描电镜(SEM)对其微观组织变化和疲劳断口进行了分析。结果表明,当奥氏体化温度由850℃升高至900℃后,疲劳强度由840 MPa增加到883 MPa,疲劳断口表面二次裂纹数量增多,且主裂纹扩展路径更曲折,裂纹扩展速率降低。且随着奥氏体化温度的升高,组织中合金渗碳体得到细化,部分碳和合金元素从大尺寸合金渗碳体中回溶到基体中,增加了固溶强化,强度和硬度分别增加约32 MPa和20HV。通过分析发现,合金渗碳体细化及碳和合金元素的回溶是疲劳性能改善的主要因素。 相似文献
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HUANG Hui- hui YANG Geng- wei ZHAO Gang DA Chuan- li HE Xian- ling CAI Zhen 《钢铁研究学报》2018,30(3):236-243
The effect of heat treatment processes on microstructure and mechanical properties of 30CrMo hot rolled steel produced by CSP (compact strip production) process were investigated. The results show that the martensite is obtained in the experimental steels by oil quenched from 900?? after holding for 15min and 60min. And the samples which oil quenched from 900?? after holding for 15min have the better mechanical properties after tempering at different temperatures. With the increase of tempering temperature, the decomposition of martensite accelerated that resulted in the lath character of martensite gradually disappeared and the precipitation of cementite in matrix. When the tempering temperature increased from 200?? to 600??, the tensile strength decreased from 1744MPa to 949MPa and the hardness of the experimental steel decreased from 50. 8HRC to 35. 3HRC.While the elongation first decreased and then increased, the yield strength first increased and then decreased. When the tempering temperature is 300??, the experimental steel has the maximum yield strength and theminimum elongation which are 1421MPa and 7. 5%, respectively. Moreover, the model was developed to predict the hardness of experimental steel after tempered at different temperatures for 120min. The calculated results were in good agreement with the experimental results. 相似文献
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The change in structure, phase composition, and defect substructure in the head of differentially quenched rail after the passage of gross traffic amounting to 691.8 million t is investigated over the central axis, at different distances from the top surface, by means of transmission electron microscopy. The results confirm that prolonged rail operation is accompanied by two simultaneous processes that modify the structure and phase composition of the plate-pearlite colonies: cutting of the cementite plates; and solution of the cementite plates. The first process involves cutting of the carbide particles and removal of their fragments, accompanied simply by change in their linear dimensions and morphology. The second process involves the extraction of carbon atoms from the crystal lattice of cementite by dislocations. That permits phase transformation of the metal in the rail, which is associated with marked relaxation of the mean binding energy of the carbon atoms at dislocations (0.6 eV) and at iron atoms in the cementite lattice (0.4 eV). The stages in the transformation of the cementite plates are as follows: the plates are wrapped in slipping dislocations, with subsequent splitting into slightly disoriented fragments; the slipping dislocations from the ferrite lattice penetrate into the cementite lattice; and the cementite dissolves with the formation of nanoparticles. The cementite nanoparticles are present in the ferrite matrix as a result of their transfer in the course of dislocational slip. On the basis of equations from materials physics and X-ray structural data, the content of carbon atoms at structural elements of the rail steel is assessed. It is found that prolonged rail operation is accompanied by significant redistribution of the carbon atoms in the surface layer. In the initial state, most of the carbon atoms are concentrated in cementite particles. After prolonged rail operation, the carbon atoms and cementite particles are located at defects in the steel’s crystalline structure (dislocations, grain and subgrain boundaries). In the surface layer of the steel, carbon atoms are also observed in the crystal lattice based on α iron. 相似文献
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Jia-Yi Yan Wen-Zheng Zhang Annika Borgenstam 《Metallurgical and Materials Transactions A》2013,44(9):4143-4149
Proeutectoid Widmanstätten cementite in a hypereutectoid carbon steel was found to be associated with a surface relief effect. A hot-stage microscope was used for heat treatment and in situ observation. Widmanstätten cementite plates were obtained near the surface of the specimen. The surface relief effect of Widmanstätten cementite plates was quantitatively characterized by atomic force microscopy. It was found that the relief had either a typical tent shape or apex-lost tent shape. The relief tilt angles were of considerable dispersion, ranging from 20 deg to 50 deg. 相似文献