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在不同的固溶温度、时效温度和时效时间的条件下,时真空感佑行热处理,研究不同热处理制度对其性能的影响.结果显示:在750~975 ℃不同的固溶温度下,固溶温度的变化对T250钢性能的影响很小;在450~570 ℃不同的时效温度下,T250钢的抗拉强度、屈服强度、冲击韧性和断裂韧性受到时效温度的显著影响,时效温度的变化对T250钢其他性能指标影响不大;时效时间大于5 h后,延长时效时间对T250马氏体时效钢性能的影响很小,T250钢在时效时间5 h时具有最佳的力学性能. 相似文献
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研究了马氏体时效钢00Ni14Cr3Mo3Ti(%:0.002C、14.06Ni、3.19Cr、3.06Mo、1.32Ti)750~1 050℃固溶处理的组织和力学性能。结果表明,≤900℃固溶处理,该钢奥氏体晶粒和强度无明显变化,固溶温度超过900℃时钢的奥氏体晶粒显著增大,钢的强度呈下降趋势。当固溶温度由750℃增加至900℃时,随固溶处理温度提高,钢中Fe2Mo相量降低,810℃时完全溶解,钢的冲击功由32 J提高至61 J,当固溶温度由900℃增至1 050℃,随奥氏体晶粒增大,钢的冲击功由61 J 降至26 J。 相似文献
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为了定量研究铌对高铌钢加热过程奥氏体晶粒长大的影响,采用化学溶解过滤分离及电感耦合等离子光谱测定不同加热温度两种试验钢固溶铌质量分数,并对比研究了奥氏体晶粒长大行为。结果表明,在低温条件下,低铌钢固溶铌质量分数高于高铌钢;随加热温度升高,高铌钢固溶铌质量分数快速增加,但即使在1 300 ℃时,铌也不能完成固溶,少量铌存在于(Ti,Nb)(N,C)析出相中;奥氏体晶粒快速长大的温度与固溶铌质量分数快速增加的温度有关。随铌质量分数由0.082%增加到0.120%,奥氏体晶粒快速长大的临界温度由1 050升高到1 150 ℃。高铌钢在1 150~1 250 ℃加热温度范围内,奥氏体晶粒尺寸小于100 μm。 相似文献
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研究了固溶温度750~1050℃对00Ni14Cr3Mo3Ti新型马氏体时效钢冲击性能和硬度的影响,并用扫描电镜观察试验钢冲击断口的形貌和固溶态显微组织。试验结果表明,钢的固溶温度低于900℃时,随着固溶温度的升高,基体中未溶的Laves相逐渐溶解,固溶态和510℃ 5 h时效态的冲击性能均随着固溶温度的上升而提高;固溶温度高于900℃,固溶态冲击性能随着固溶温度的上升而提高,该钢固溶态冲击功由900℃的215J增加至1050℃固溶的226J,但时效态冲击性能随着固溶温度上升而降低,510 5h时效钢的冲击功由900℃最大值62J降至1050℃固溶的25J。 相似文献
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《特殊钢》2020,(1)
研究了固溶温度750~1 050℃对00Ni14Cr3Mo3Ti新型马氏体时效钢冲击性能和硬度的影响,并用扫描电镜观察试验钢冲击断口的形貌和固溶态显微组织。试验结果表明,钢的固溶温度低于900℃时,随着固溶温度的升高,基体中未溶的Laves相逐渐溶解,固溶态和510℃5 h时效态的冲击性能均随着固溶温度的上升而提高;固溶温度高于900℃,固溶态冲击性能随着固溶温度的上升而提高,该钢固溶态冲击功由900℃的215 J增加至1 050℃固溶的226 J,但时效态冲击性能随着固溶温度上升而降低,510 5 h时效钢的冲击功由900℃最大值62 J降至1050℃固溶的25 J。 相似文献
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Nb、Ti碳化物的溶解与析出对低C微合金钢组织和性能的影响 总被引:2,自引:0,他引:2
采用理论计算方法分析了Nb、Ti碳化物在低C微合金钢(%:0.09C、1.42Mn、0.035Nb、0.012Ti)奥氏体中的溶解与析出,测试了不同加热温度下奥氏体晶粒尺寸以及固溶-时效后实验钢的硬度。结果表明,Nb、Ti碳化物在1060℃全部溶解,800℃时效时,奥氏体中的Nb、Ti基本以NbC、TiC形式析出。700℃时效时,Nb、Ti碳化物在铁素体内析出,随温度降低,碳化物析出减慢。600℃时效,钢的硬度达到最大值。 相似文献
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通过对焦炭在高炉内的历程及其变化规律的剖析,阐述焦炭热性能指标的意义,形象地把焦炭在高炉内的损耗分为三部分(M1,M2,M3)。指出M2对焦比及焦炭价格有一定的指导作用。 相似文献
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K Ohta M Nishi M Ueda S Ohyama T Matsubara T Takahashi T Nakajima 《Canadian Metallurgical Quarterly》1998,99(9):589-594
Cancer of the cardia is traditionally discussed with cardiac cancer of the lower portion of the esophagus and upper gastric cancer invading the esophagus, and the specific characteristics of cancer of the cardia have never been clearly defined. We reviewed the outcome of 172 patients with adenocarcinoma of the cardia who had undergone radical surgery between 1949 and 1994 in the Division of Gastrointestinal Surgery of the Cancer Institute Hospital. The centers of the tumors were located within 2 cm above and below the boundary between the esophagus and the stomach, and their longitudinal diameter was less than 8 cm. We divided the patients into an early period (1949-1979; n = 79) and a late period (1980-1994; n = 93), and focused on the historical transition. There were no differences in patient gender or histology between the two periods. However, the late period was associated with fewer cases of esophageal invasion and shorter longitudinal diameter, as the age of the population advanced. The number of advanced cancers such as the localized and infiltrative type had decreased, and early cancer and early clinical stage had become more common, but despite the fact that the number of early cancers had increased, extended dissection, such as thoracic and paraaortic lymph node dissection, was performed more frequently. By clinical stage, the long-term outcome markedly improved in Stage I patient in the late period, and tended to improve in Stage II and III patients. This appears to have been attributable to the prevention of micrometastasis by extended dissection, although the number of early cancers is another major potential cause. There were no differences in the outcome of Stage IV patients between the two periods, and further advances in multimodality therapy must be awaited. The range of resection is basically proximal gastrectomy, and if there are adequate indications, the prognosis is favorable. In view of the status of lymphatic flow and lymph node metastasis, and long-term results, lateroaortic lymph node dissection is important. Since the number of early cancer patients has been increasing, if intraabdominal recurrence is prevented, intrathoracic lymph node dissection will contribute greatly to the outcome of such patients. 相似文献
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Some theories of personality hold that an individual's perception of others is influenced by his own personality characteristics; more specifically, that a trait of low social value will be projected more into others, and that insight into the possession of these characteristics reduces this distortion. These 2 hypotheses were tested by having a group of college students rate each other (including themselves) on degree of friendliness or hostility. Agreement with group rating about self yielded the insight score. In general, the hypotheses were supported; the "friendly" Ss were most accurate in their perception of others, and insight was positively associated with accurate perception. From Psyc Abstracts 36:04:4HL16M. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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The rates of infection of two methods of external ventricular drainage in use at Atkinson Morley's Hospital--namely, (a) percutaneous drainage with Rickham reservoirs and (b) tunnelled ventriculostomies--were compared in this retrospective review. Percutaneous drainage of CSF with Rickham reservoirs was associated with a 27% rate of infection as identified by positive microbiological cultures; tunnelled ventriculostomy catheters had a 10% infection rate. The difference in the infection rate between the two methods was statistically significant (P < 0.015). Other variables examined, including the age and sex of the patients and the reasons for ventricular drainage, were not associated with an increased rate of infection. Most infections from either method were caused by a coagulase negative staphylococcus. The average duration of ventricular drainage before identification of positive cultures was 5.7 days for Rickham reservoirs and 6.0 days for ventriculostomies. 相似文献
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鲁迅先生一生热爱美术作品,对版画中木刻兴趣尤甚.<野草>作为其"写心之作",亦呈现出一些与木刻版画一致的审美特征:一是具有木刻版画的色彩特征,多对比、多冷色,有阴郁的美感;二是具有木刻版画的力度特征,环境描写、人物刻画处处刀锋毕现,遒劲有力,有一种"力之美". 相似文献
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针对四辊破碎机车刀架车削中存在的几个问题,详细介绍了电动车刀架的结构和工作原理,建立主要设计参数的数学表达式,并进行适当的分析。改造后,这种电动车刀架运行平稳、可靠、方便、省力,取得了预期的效果。 相似文献
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The effect of 20 different antibiotics on chemotaxis by human neutrophils was studied. Human leukocytes incubated with chloramphenicol, rifampin, sodium fusidate, and tetracyclines in vitro showed markedly depressed migration. The mechanisms by which these antibiotics affect leukotaxis are discussed. 相似文献