含碳量对烧结铜钢尺寸与性能的影响

通过金相检验、拉伸试验、硬度及尺寸测定,研究了含碳量对烧结铜钢尺寸及性能的影响。结果表明:铜含量及密度一定,在相同烧结和热处理条件下,随含碳量的增加,试样尺寸逐渐变小;试样烧结态的极限强度、屈服强度、硬度值显著增加,但延伸率却明显下降;试样热处理态强度也略有增加,但当碳含量超过一定值时会有所下降,延伸率相对变化也不大,表面硬度值略有增加。     

C含量对Fe-Cu-C合金性能的影响

研究了碳含量对Fe-Cu-C合金性能的影响.结果表明:碳含量低于1.2%时,随着碳含量的增加,材料的表观硬度增加,强度先增后减,在含碳0.8%时综合性能最佳,其表观硬度HRB达74.7,强度为487.30MPa,延伸率达1.8%.烧结后Fe-Cu-C材料的轴向膨胀率随碳含量的增加逐渐减少.经淬火 回火处理后的Fe-2Cu-0.8C试样性能为:硬度HRC 22.5,强度630.20 MPa,延伸率1.4%;较之于烧结态,强度、硬度提高明显,但延伸率稍有下降.     

SPS制备WC颗粒增强高合金工具钢的组织及力学性能

采用放电等离子烧结技术(SPS)制备不同WC颗粒含量的HGSF01高合金工具钢.通过扫描电镜、X射线衍射技术等测试手段研究烧结态的组织、物相组成和力学性能,并对试样的弯曲断裂断口进行分析.实验结果表明:随着烧结温度的提高,材料密度不断提高;随着增强颗粒含量的增加,材料的硬度和抗弯性能得到明显提升,但致密度有所下降;烧结态试样的主相是马氏体,同时还伴有残余奥氏体、Cr7C3、VC、Cr2VC2及少量的Mo、Cr碳化物;由弯曲试验的断口分析得知,1 050℃烧结试样的断口形貌特征为多种断裂机制并存.     

Ni、P元素对于铁基粉末冶金材料力学性能的影响

采用粉末冶金方法制备铁基烧结材料,并测试材料的硬度和压溃强度,考察了Ni、P元素对于铁基粉末冶金材料密度和力学性能的影响.结果表明:Ni不仅可以提高铁基材料中珠光体的含量,还可以显著提高材料的硬度和压溃强度,当Ni含量为3％时效果最好;添加微量P元素可以明显提高含Ni铁基材料的硬度和压溃强度,但当P含量超过0.15％后,对材料硬度的提升作用减缓,而材料的压溃强度则大幅下降.     

先进的烧结-硬化材料在汽车齿轮、凸轮及链轮等中的应用

最近的汽车产业应用,要求具有高表观硬度、高淬透性及高力学性能的粉末冶金零件材料。这些要求往往是相互矛盾的,因此需要开发烧结态具有高表观硬度、良好静态动态力学性能又不会增加后续热处理费用的新材料。传统上,烧结硬化材料具有适用的表观硬度,但力学性能与烧结体密度差。这里将用资料证明具有良好压缩性,高表观硬度及提高力学性能的一系列烧结硬化材料的力学性能。集中讨论这些材料在汽车发动机与变速器中的应用,诸如齿轮、凸轮及链轮等,这些零件目前都是由压制-烧结及热处理工艺或由铸件或锻造材料用常规切削加工生产的。也将讨论用高温烧结来增强其工艺过程。     

原始成分组成对Ti(C,N)基金属陶瓷烧结性能的影响

采用真空烧结工艺制备了Ti(C,N)基金属陶瓷,研究了原始成分组成对材料烧结特性和力学性能的影响规律。结果表明:保持Mo/(Mo+Ni)为定值,随着硬质相成分的增加,烧结体抗弯强度降低,硬度增加;硬质相成分TiN含量超过一定阈值时,烧结体疏松导致硬度和抗弯强度同时大幅下降;TiN含量保持定值,硬质相成分含量增加,烧结体硬度增加,抗弯强度下降;粘结相成分用Co部分替代Ni,随Co含量的增加,烧结体硬度略有升高的基础上抗弯强度升高。     

铁基粉末冶金材料感应烧结过程研究

以粗铁粉为主要原料,研究了原始颗粒尺寸、压坯密度及感应电流对感应烧结过程及材料性能的影响。结果表明:粉末颗粒尺寸减小、压坯密度增大和电流增大都可以使铁粉产生更多的热量,促进烧结过程的进行。烧结开始时,粉末颗粒自身的硬度下降,加工硬化现象消除,材料硬度大幅度降低;烧结基本完成后,颗粒间结合强度增大,试样的硬度逐渐趋于平稳,并且有小幅上升。材料的耐腐蚀性随烧结时间的延长而提高。     

石墨含量对粉末冶金凸轮轴性能的影响

以铁基粉末冶金材料Fe-5Cr-2Cu-1Si-1Mo-0.5P-XC作为凸轮材料,采用烧结焊技术实现粉末冶金凸轮与16Mn钢管的连接。研究石墨添加量(质量分数1.5%~2.5%)对粉末冶金凸轮材料烧结致密化、硬度及凸轮与钢管之间扭矩的影响。结果表明:随石墨含量的增加,烧结坯尺寸收缩率、密度、硬度急剧增加,石墨含量大于1.9%后各性能参数值增加趋势减缓,最大值分别为5%、7.496 g/cm3和53.77 HRC;随石墨含量的增加,扭矩先急剧增大后略有下降,石墨含量为1.9%时扭矩达到最大值980 N.m。     

W对自由烧结型铁基金刚石工具胎体性能的影响

以专用于自由烧结型金刚石工具胎体的亚微米级铁基合金粉末为主要结合剂,添加金属W(添加量为0~12%,质量分数),采用自由烧结工艺制成金刚石工具胎体和金刚石/胎体试样,对胎体进行力学性能测试和断口形貌分析,并用金刚石工具进行磨削试验。结果表明,随W含量增加,胎体的相对密度及强度均下降;添加6.0%W可明显提高胎体对金刚石的把持能力,并提高胎体硬度,但随W含量进一步增加,把持能力下降,同时胎体硬度降低;W在胎体内虽然可生成强碳化物,但在自由烧结过程中起不到强化胎体的作用,反而降低胎体的韧性,尤其是当胎体中添加12.0%W时,胎体内孔隙明显,强度大幅下降;与不添加W的胎体相比,添加8.0%W时,虽然金刚石工具的锋利度有所下降,但耐磨性提高。     

含铜铁基粉末冶金零件烧结性能的研究进展

含铜铁基粉末冶金材料在烧结前后易发生尺寸变化,为此类零件的生产带来不便。本文介绍了有关含铜铁基粉末冶金材料的烧结过程、烧结过程中铁铜粉末颗粒尺寸变化和烧结尺寸变化的相关研究进展,主要包括以下内容:高于Cu熔点温度烧结时,Cu颗粒熔化扩散渗入Fe颗粒中,在Cu颗粒原本位置形成流出孔隙,从而造成烧结坯尺寸的膨胀;随着烧结温度或烧结时间的增加,烧结过程中铁铜粉末颗粒的尺寸呈增大趋势;影响含铜铁基粉末冶金材料烧结尺寸变化率的主要因素是粉末粒度及合金元素的成分和含量。     

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.