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模拟了04Cr13Ni5Mo超级马氏体不锈钢不同焊接热循环条件下热影响区组织,进行了焊条电弧焊接及焊后热处理试验,分析了焊接热模拟试样及焊条电弧焊接头的微观组织、力学性能.焊接热模拟试验结果表明,模拟热影响区的组织主要为低碳板条马氏体,其硬度较母材有较大提高,冲击韧性有所下降;模拟单道焊或多道焊时,不同的冷却速度及层间热处理对模拟热影响区的硬度及冲击韧性影响不大,600℃焊后回火热处理可以明显软化模拟热影响区组织,并让其冲击韧性恢复到较高水平.焊条电弧焊接结果表明,采用04Cr13Ni5MoRe型焊条及配套的焊后热处理工艺,可以获得良好综合力学性能的焊接接头. 相似文献
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QP980淬火-配分钢属于第三代先进高强钢,具有强塑积高、成形性好等优点而成为汽车轻量化发展的重要材料。对国内某公司生产的1.5 mm厚的QP980淬火-配分钢采用机器人MAG焊(熔化极活性气体保护焊)进行焊接,分析焊接工艺参数对其焊接接头组织和力学性能的影响。考虑到焊接的淬火作用以及焊接接头的等强匹配原则,采用ER50-6焊丝作为填充材料。研究结果表明,在合适的焊接工艺窗口内,减小焊接热输入有利于提高焊接接头的强度,但对其塑性有不利影响。焊接接头横截面的组织和力学性能变化非常大,焊缝金属区主要由铁素体和珠光体组成,硬度较低,但能达到原始母材的硬度值;靠近焊缝的热影响区主要是完全相变区,该区是由原始母材组织发生奥氏体转变后冷却产生的以板条马氏体为主的组织,硬度较母材有较大提升,该区成为焊接接头的硬化区,而靠近母材的焊接热影响区主要包括两相区和回火区,两相区中部分组织发生了奥氏体转变,冷却后转变的组织较原始组织中的马氏体含量有所降低,硬度略有下降,而回火区是由原始组织中的铁素体、少量奥氏体以及发生了回火的马氏体组成,由于马氏体的回火作用,硬度也略有降低。在该钢的MAG焊中,焊接接头软化现... 相似文献
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超高强钢对汽车轻量化具有重要意义,可在不降低汽车安全性的前提下,降低车身自重。超高强钢在点焊过程中的热影响区软化是进一步提高超高强钢承载能力的关键。本文采用Gleeble 3800热模拟试验机,对超高强钢电阻点焊过程中热影响区的组织转变进行了模拟,研究了热影响区不同区域的微观组织和显微硬度。研究显示,B1500HS超高强钢在加热到Ac3以上温度时,形成索氏体和铁素体组织。加热到Ac1-Ac3之间的温度时形成珠光体和铁素体组织。加热到Ac1以下温度时形成铁素体和残留马氏体组织。热影响区的最低硬度出现在临界热影响区。通过加快冷却速度,以获得高硬度的马氏体相,可以提高接头的承载能力。 相似文献
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研究了采用ER309L不锈钢焊丝对25 mm厚的A514/ZGMn13Mo异种钢进行多层多道的熔化极气体保护焊。显微组织显示了焊缝组织为铁素体和奥氏体,具有较强的抗裂性,A514钢热影响区组织主要为板条状马氏体和少量的铁素体,未发现碳化物,热影响区存在较大的应力,ZGMn13Mo钢热影响区组织为粗化的奥氏体,晶界与晶内存在大量的碳化物,同时较大的焊接应力导致该侧影响区易萌生裂纹。显微硬度结果表明了焊缝底部和中部显微硬度相对于焊缝顶部较高,A514钢热影响区显微硬度表现为先升后降的特点,ZGMn13Mo钢热影响区硬度持续上升直至达到母材硬度水平。 相似文献
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采用热膨胀法结合显微金相与硬度检测,在热模拟试验机上测定了1000MPa级低碳微合金高强钢焊接过程中的临界点Ac1和Ac3,绘制出该钢在不同冷却速率下的焊接连续冷却转变曲线(SH-CCT曲线),研究了冷却速率对焊接热影响区粗晶区(CGHAZ)组织和硬度的影响规律,揭示了不同冷却速率下焊接热影响区的相变过程及组织特征,同时获得了奥氏体晶粒平均尺寸随t8/5的变化关系。研究结果表明,在焊接条件下,该钢的奥氏体化温度要比平衡状态下的奥氏体化温度显著升高;该钢在相当宽的冷却速率范围内发生中温转变,获得贝氏体组织;在较快的冷却速率(≥40℃/s)下,焊接热影响区组织以马氏体为主;随着冷却时间t8/5的增加,硬度逐渐下降,最高硬度HV10为425。在试验条件下,奥氏体晶粒粗化程度并不显著。 相似文献
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利用扫描电镜、透射电镜和硬度测试等方法研究了不同退火工艺对 AMS 6308钢硬度及组织的影响。结果表明,提高退火温度,马氏体板条内位错密度降低,M6 C 的尺寸逐渐增加,硬度下降,但在750℃以上退火,进入二相区,空冷后产生二次马氏体,硬度回升。延长退火时间,马氏体板条回复逐渐充分,硬度开始下降较快,16 h后组织变化不明显,M6 C 的含量变化不大,硬度变化也不大。退火软化程度主要受板条内位错密度的下降以及M6 C 的粗化控制。推荐退火温度选择700~720℃,退火时间不低于16 h,720℃退火软化效果最佳。 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