共查询到20条相似文献,搜索用时 156 毫秒
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《材料热处理学报》2015,(7)
研究了不同热处理工艺(淬回火、贝氏体等温淬火、马氏体预淬火后贝氏体淬火和贝氏体变温淬火处理)对典型高碳铬轴承钢GCr15的组织以及硬度、抗拉强度、冲击功和耐磨性等力学性能的影响,对比分析了不同热处理工艺的微观组织和性能的关系;为了更好地分析下贝氏体短时处理和尺寸稳定性,采用膨胀法进行了试验研究;利用XRD分析,研究了不同热处理工艺后残留奥氏体的量。研究表明,与常规淬回火相比,得到贝氏体组织的处理过程可以得到组织和性能的最佳匹配;贝氏体处理后,试样综合性能优于淬回火处理且尺寸稳定性好;马氏体预淬火处理和贝氏体变温处理在提高钢综合性能的同时又能不同程度缩短贝氏体转变时间。 相似文献
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采用有限元仿真和试验方法分析贝氏体等温淬火工艺对GCr15钢轴承套圈畸变和断裂韧性的影响。采用Deform-3D软件对轴承套圈贝氏体淬火工艺进行数值模拟。以圆柱滚子轴承NJ308为研究对象,仿真热处理后最大直径畸变量为0.08 mm,与试验结果对比,仿真误差14%。采用热处理工艺试验,测量贝氏体淬火后轴承直径畸变量为0.07 mm。对比测量分析常规马氏体淬火和贝氏体淬火后的畸变大小,贝氏体热处理后直径畸变极差小,更为均匀,有利于后续的磨削加工。通过断裂试验对比分析,常规的马氏体淬回火工艺断裂强度为113.3 kN,贝氏体等温淬火处理后的断裂强度为152.7 kN,断裂强度显著提升。 相似文献
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基于有限元计算分析了直径为ø40 mm的42CrMo钢圆棒试样分别使用淬火油和PAG水基液淬火后试样不同位置的组织、硬度以及淬火过程中的温度变化,采用硬度检测和显微组织分析对模拟结果进行了验证。结果表明,当使用淬火油淬火时,试样表面由奥氏体向马氏体和贝氏体转变,心部由奥氏体向贝氏体转变;当使用PAG水基液淬火时,试样表层几乎转变成马氏体,心部转变成马氏体和贝氏体;试样经淬火油和PAG水基液淬火后,表面硬度分别为58和55 HRC,均由表面至心部硬度逐渐降低,但使用PAG水基液淬火后试样的心部硬度比用淬火油的高5 HRC,约为50 HRC。 相似文献
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《热处理技术与装备》2020,(4)
本文对高淬透性轴承钢进行不同的等温淬火工艺试验。试验结果表明:淬火加热温度过高,贝氏体尺寸有明显增大,甚至局部出现了个别粗大的不合格贝氏体组织。合理的等温淬火工艺参数有利于获得性能良好的贝氏体组织。 相似文献
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利用淬火连续冷却得到奥—贝球铁的研究 总被引:1,自引:0,他引:1
利用等温淬火,研究了锰促进球铁基体组织向贝氏体转变的含量。在确定锰含量条件下,利用水玻璃淬火介质代替等温淬火介质,对球铁进行淬火处理。试验结果表明,当锰含量为2.0%~3.0%时,可在组织中获得较多的贝氏体,有较高的硬度和适当的冲击韧度。水玻璃淬火可以代替等温淬火,获得下贝氏体组织。 相似文献
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研究了等温淬火工艺参数对化学成分(质量分数)为0.42%C,2.1%Si,1.64%Mn,0.9%Cr中低碳低合金铸钢力学性能的影响.光学显微组织、透射电镜组织以及XRD物相分析结果表明,试样在340~380℃范围内经等温淬火处理后,可以获得无碳化物析出的奥氏体-贝氏体组织,且随着等温淬火温度的升高,贝氏体形貌由板条状下贝氏体逐渐向上贝氏体转变,试样的硬度≥HRC 40,冲击韧性ak≥120 J/cm2. 相似文献
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Uma Batra Subrata Ray S.R. Prabhakar 《Journal of Materials Engineering and Performance》2007,16(4):485-489
The influence of austenitization and austempering parameters on the impact properties of copper-alloyed and nickel-copper-alloyed
austempered ductile irons (ADIs) has been studied. The austenitization temperature of 850 and 900 °C have been used in the
present study for which austempering time periods of 120 and 60 min were optimized in an earlier work. The austempering process
was carried out for 60 min for three austempering temperatures of 270, 330, and 380 °C to study the effect of austempering
temperature. The influence of the austempering time on impact properties has been studied for austempering temperature of
330 °C for time periods of 30-150 min. The variation in impact strength with the austenitization and austempering parameters
has been correlated to the morphology, size and amount of austenite and bainitic ferrite in the austempered structure. The
fracture surface of ADI failed under impact has been studied using SEM. 相似文献
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本文研究了奥氏体-贝氏体等温淬火球墨铸铁(以下简称ADI)等淬工艺对组织、性能的影响,得到了各项力学性能指标所对应的工艺参数;对20mm-50mm范围试样壁厚敏感性进行了试验,认为通过控制合金成分、球化、孕育、等淬工艺可使断面组织均匀、齐一性好,并作了理论分析。 相似文献
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Austempering kinetic measurements and mechanical property measurements are reported for two Mn ductile irons with and without Co and three austempering treatments. It is shown that Co accelerates the stage I reaction in each of the irons and for each of the austempering treatments but has little affect on the stage II reaction. Consequently, the processing window is widened and moves to earlier austempering times. This can be useful in the austempering of thicker section components to obtain the higher ductility grades of the ADI standard and to increase process productivity. 相似文献
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Measurements of ultimate tensile strength, 0.2% proof strength, elongation and unnotched Charpy impact energy are presented as a function of austempering time in the range from 1 to 4320 minutes for austempering temperatures of 400, 375 and 285 °C and austenitising temperatures of 870, 920 and 950 °C for a ductile iron of composition 3.39%C, 2.56% Si, 0.25% Mo, 0.29% Cu, 0.37% Mn and 0.04% Mg. Austempering kinetic measurements are presented for the various austenitising and austempering temperatures. These measurements are analysed to relate microstructure and mechanical properties and to define processing windows for the different austempering conditions. The analysis suggests a new definition for the closure time of the processing window. The newly defined processing windows are consistent with mechanical property observations in the present iron and a previously studied iron with the same base composition but containing 0.67% Mn. 相似文献
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《International Journal of Cast Metals Research》2013,26(6):330-343
AbstractDuctile cast iron samples were austenitised at 900°C and subjected to two types of austempering called as conventional austempering and two-step austempering. Five different temperatures, 280, 300, 320, 350, 380 and 400°C, with an austempering time of 2 h, were chosen for conventional austempering. For two-step austempering process, the first step temperatures were 280, 300 and 320°C. The samples were austempered at each of these temperatures for different times, i.e. 10, 20, 30, 45 and 60 min, and then upquenched to higher temperature of 400°C for 2 h. Fracture toughness and tensile studies were carried out under all these austempering conditions. During conventional austempering, the fracture toughness initially increased with increasing austempering temperature, reached a peak value of 63 MPa m1/2 and dropped with further increase in temperature. During the two-step austempering, fracture toughness was found to increase with increasing first step time. The curve shifted to higher values of fracture toughness as the first step temperature was decreased and the maximum value of 78 MPa m1/2 was obtained. The results of the fracture toughness study and the fractographic examination were correlated with microstructural features such as bainitic morphology, the volume fraction of retained austenite, and its carbon content. Ferrite lath size and stability of the retained austenite were found to influence the fracture toughness. 相似文献
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Uma Batra S. Ray S. R. Prabhakar 《Journal of Materials Engineering and Performance》2003,12(4):426-429
The variation in the austempered microstructure, the volume fraction of retained austenite, Xλ, the average carbon content of retained austenite, Cλ, their product XλCλ and the size of bainitic ferrite needles with austempering temperature for 0.6% Cu alloyed ductile iron have been investigated
for three austempering temperatures of 270, 330, and 380 °C for 60 min at each temperature after austenitization at 850 °C
for 120 min. The austempering temperature not only affects the morphology of bainitic ferrite but also that of retained austenite.
There is an increase in the amount of retained austenite, its carbon content, and size of bainitic ferrite needles with the
rise in austempering temperature. The influence of austempering time on the structure has been studied on the samples austempered
at 330 °C. The increase in the austempering time increases the amount of retained austenite and its carbon content, which
ultimately reaches a plateau. 相似文献
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Riccardo Donnini Alberto Fabrizi Franco Bonollo Franco Zanardi Giuliano Angella 《Metals and Materials International》2017,23(5):855-864
The aim of this investigation was to determine a procedure based on tensile testing to assess the critical range of austempering times for having the best ausferrite produced through austempering. The austempered ductile iron (ADI) 1050 was quenched at different times during austempering and the quenched samples were tested in tension. The dislocation-density-related constitutive equation proposed by Estrin for materials having high density of geometrical obstacles to dislocation motion, was used to model the flow curves of the tensile tested samples. On the basis of strain hardening theory, the equation parameters were related to the microstructure of the quenched samples and were used to assess the ADI microstructure evolution during austempering. The microstructure evolution was also analysed through conventional optical microscopy, electron back-scattered diffraction technique and transmission electron microscopy. The microstructure observations resulted to be consistent with the assessment based on tensile testing, so the dislocation-density-related constitutive equation was found to be a powerful tool to characterise the evolution of the solid state transformations of austempering. 相似文献
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Junyu Tian Guang Xu Zhengyi Jiang Haijiang Hu Mingxing Zhou 《Metals and Materials International》2018,24(6):1202-1212
The effects of Nickle (Ni) addition on bainitic transformation and property of ultrahigh strength bainitic steels are investigated by three austempering processes. The results indicate that Ni addition hinders the isothermal bainite transformation kinetics, and decreases the volume fraction of bainite due to the decrease of chemical driving force for nucleation and growth of bainite transformation. Moreover, the product of tensile strength and total elongation (PSE) of high carbon bainitic steels decreases with Ni addition at higher austempering temperatures (220 and 250 °C), while it shows no significant difference at lower austempering temperature (200 °C). For the same steel (Ni-free or Ni-added steel), the amounts of bainite and RA firstly increase and then decrease with the increase of the austempering temperature, resulting in the highest PSE in the sample austempered at temperature of 220 °C. In addition, the effects of austempering time on bainite amount and property of high carbon bainitic steels are also analyzed. It indicates that in a given transformation time range of 30 h, more volume of bainite and better mechanical property in high carbon bainitic steels can be obtained by increasing the isothermal transformation time. 相似文献
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The thermal stability of an ADI has been studied by isothermal aging at 350℃ for 150 hours, measuring the amount of retained austenite and its carbon content by X-ray diffractometry. The influence of different austempering treatments, carried out at temperatures between 300 and 450℃ (300, 330, 360, 410 and 450℃) and holding times between15 and 60 minutes (15, 30, 45, 60), was considered. Thermal stability depends on whether austempering temperature is higher or lower than the ageing one. Thermal stability increases by increasing austempering temperatures, from 300° to410℃. Samples treated at 410° and 450° show a lower austenite decomposition than samples at 300-330-360℃. A drop in stability is shown by increasing the austempering temperature from 410° to 450℃. The results have been interpreted on the basis of the austenite stability out of the processing window, which in turn depends on the austempering parameters. 相似文献