汽车齿轮制造过程中钢的组织控制

以新型Cr-Ni-Mo系齿轮钢20CrNi2MoH钢为例,分别论述20CrNi2MoH钢锻造齿坯和该钢冷挤压坯料的组织控制.     

减速机齿轮轴断齿原因分析

针对减速机齿轮轴发生断齿现象，进行了化学成分分析，利用金相分析技术研究了齿轮轴内部微观组织结构以及产生缺陷的原因，采用扫描电镜观察断口形貌特征，以及通过硬度计算方法计算了齿部的硬化层深度，并对齿顶渗碳淬火硬化层进行了数学校验。结果表明，由于齿轮在淬火加热时温度过高，导致齿轮内部出现粗大马氏体及网状碳化物，齿面存在严重的内氧化现象致使齿部材料脆化，进而出现沿晶裂纹和掉块，并且在齿轮轴存在安装偏载且硬度偏低的协同作用下发生断齿现象。     

增速器大齿轮渗碳淬火变形原因分析与改进

对增速器大齿轮渗碳淬火变形原因进行了分析,提出采用两侧用盖板保炉、凹槽内填充耐火纤维等措施,可以大大改善大齿轮渗碳淬火变形情况,并满足了工艺技术要求.     

齿轮类渗碳件淬火变形及控制

介绍齿轮类渗碳件淬火后的变形原因,根据硬齿面齿轮生产现状,分析渗碳件变形的原因,并进一步系统分析了齿轮变形的原因,采取相应措施控制并减少变形来获得均匀的渗碳层,从而提高齿轮的承载能力和使用寿命。     

中碳钢锻造卸扣断裂分析

45钢锻造卸扣在使用过程中发生断裂。通过化学成分分析、断口形貌分析、金相检验和力学性能测试等方法对卸扣断裂的原因进行了分析。结果表明:该卸扣表面存在众多的锻造细小折叠裂纹,这些细小折叠裂纹扩展及延伸形成陈旧裂纹,导致卸扣的承载能力下降,当卸扣受到冲击载荷作用,便产生以陈旧裂纹为断裂源的一次脆性断裂。     

齿轮用19CrNi5钢的研制

介绍了依维柯汽车齿轮用钢19CrNi5的研制情况,针对该钢种的主要技术要求确定试生产工艺,在关键工艺点实施控制,使产品的实物质量满足了用户要求,实现了依维柯系汽车齿轮用钢的国产化。     

大规格钼合金径向锻造中心裂纹成因分析及改进措施

通过金相组织观察、化学成分分析、断口形貌观察、显微硬度测试、有限元模拟等方法对大规格径向锻造钼合金棒材的周期性中心裂纹进行分析.结果表明,棒材中心存在轻微的成分偏析,严重的不均匀变形是棒材在锻造过程中产生中心裂纹的主要原因.通过提高原料纯净度、均匀化退火以及增加回火温度和时间,可在一定程度上防止大规格钼合金棒材在加工过...     

高速线材04H轧机减速齿轮断裂分析

应用硬度检验，化学分析及金相分析等方法对高速线材轧机减速机大齿轮断裂原因进行综合分析。结果表明，齿轮在制造过程中的机械加工不当，使齿轮产生磨削裂纹，渗碳层不均匀，在齿轮工作过程中裂纹进一步扩展导致齿轮断裂。     

30CrNi3Mo渗碳钎钢的心部组织及其与性能的关系

本文利用电镜分析了30CrNi3Mo渗碳钎钢的心部组织为板条马氏体和板条间的薄膜状残余奥氏体,并根据此组织对钢的K_(IC)、冲击韧性和裂纹扩展速度进行了分析和讨论。     

SAE8620H的淬透性对热处理变形的影响

利用C型缺口试样研究了不同淬透性的SAE8620H齿轮钢的渗碳热处理变形,并对C型缺口试样心部微观组织和硬度进行了分析.结果表明,SAE8620H齿轮钢在距淬火端9 mm处的硬度低于32HRC时,C型缺口试样心部主要为贝氏体组织,渗碳热处理变形较小;随着淬透性的提高,试样心部马氏体组织逐渐增加,渗碳热处理变形显著增大.不同淬透性的SAE8620H齿轮钢的相变组织不同,因而渗碳热处理变形不同.     

转炉炉壳热应力分析

根据实际转炉建立实体模型。以有限元为手段,考虑了炉衬和炉壳材料的物性参数随温度变化的特点和炉衬与炉壳之间膨胀间隙,计算了转炉炉壳在温度载荷和炉衬膨胀压力同时作用下的热应力。所得结果可为转炉炉壳设计提供依据。     

焦炭热性能指标意义浅析

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。     

Results of treatment of cancer of the cardia

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.     

The effect of amount of possession of the trait of hostility on accuracy of perception of hostility in others.

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)     

Comparison of rates of infection of two methods of emergency ventricular drainage

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.     

浅析《野草》的版画特征

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".     

四辊破碎机车刀架的改造

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。     

Effect of antibiotics of chemotaxis of human leukocytes

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.