影响烧结硬化合金钢齿轮特性之参数探讨

根据不同合金钢合金化的方式与添加元素的种类, 规划出4 组不同硬化能之烧结合金钢; 将这4 种硬化能不同之烧结合金钢粉末分别压制成密度为6.85 g/cm3 的齿轮胚体, 经RX型保护气氛、1 120 ℃烧结30 min后, 继以24℃/min与48℃/min的冷速率来控制冷却过程中合金钢的相变化行为, 再将烧结态之合金钢齿轮施以200℃、1~4 h之回火处理; 最终对合金钢齿轮进行硬度、齿轮精度、齿破裂负载等量测与金相观测。研究结果显示烧结合金钢的硬化程度随硬化能的增加或烧结淬冷速率的加快而提升, 而齿轮精度则随其相变后的马氏体含量的增加而降低。故针对烧结硬化合金钢齿轮的制造流程开发中, 烧结淬冷区的冷却速率须达48℃/min, 才能确保齿轮之硬度维持在HRC 30以上; 且硬化能倍数宜调整在15~25之间, 经1 h以上的回火, 即可获得具经济竞争力, 又具优异机械性能与齿轮精度组合的烧结硬化合金钢齿轮。     

影响烧结硬化合金钢齿轮特性之参数探讨

根据不同的合金钢合金化方式与合金添加种类，规画出四组不同硬化能力之烧结合金钢。将这四种硬化能力不同之烧结合金钢粉末分别压制成密度为6．58g／cm^3的齿轮坯体，在RX型保护气氛下。1120℃烧结30min后，再以2412／min与48℃／min的冷却速率来控制冷却过程中合金钢的相变行为，再将烧结态之合金钢齿轮施以200℃、1～4h之回火处理；最终对合金钢齿轮进行硬度、齿轮精度、齿破裂负载等量测与金相观测。研究结果显示，烧结合金钢的硬化程度随硬化能力的增加或烧结后淬冷速度的加快而提高，而齿轮精度则随其相变为马氏体含量的增加而降低。故在烧结硬化合金钢齿轮的开发制造过程中，烧结后淬冷区的冷却速度须达48℃／min，才能确保齿轮特性之硬度维持在30HRC以上，且硬化能力倍数宜调整在15～25之间，经1h以上的回火，即可获得具经济竞争力，又具优异力学性能与齿轮精度组合的烧结硬化合金钢齿轮。     

渗铜剂成分对烧结钢渗铜性能的影响

采用纯Cu粉、Cu-2Zn粉、Cu-2Fe粉、Cu-2Zn-2Fe粉等4种不同成分的渗铜剂,以Fe-Cu-C烧结钢为基体,在1 120～1 150℃、保温30 min工艺下渗铜,研究不同成分渗铜剂的熔渗性能及其对渗铜烧结钢力学性能的影响。结果表明:同其它3种渗铜剂相比,Cu-2Zn-2Fe渗铜剂渗铜性能最好,烧结钢渗铜后表面质量均匀一致、无溶蚀现象;上下表面硬度基本一致,较未渗铜烧结钢提高了约60%;4种渗铜剂渗铜的烧结钢冲击韧性为13.7～14.0 J/cm2,较未渗铜的提高2倍以上;在渗铜剂中,Fe元素可以降低渗铜剂熔体活性、增加黏度;Zn元素可以降低渗铜剂熔体黏度、增加其活性。     

激光硬化粉末烧结钢的组织结构及耐磨性

两种Fe-Ni-Cr-Cu-Mo-C系粉末烧结钢宽带激光硬化处理表明,激光硬化的粉末烧结钢表面层的组织结构由马氏体、贝氏体、残余奥氏体和游离态石墨等组成.激光硬化处理显著改善了粉末烧结钢的耐磨性.     

高耐磨、耐热碳化钨不锈钢喷煤枪应用

煤枪因高温氧化及煤粉的冲刷，破损严重、寿命短。以WC为硬化相，以合金钢粉末为粘结剂，经配料、混料、压制和烧结制成的粉末冶金材料为渗剂对喷枪进行渗碳化钨处理，渗层厚度1．2mm，可提高喷枪表面硬度(HLC大于780)、耐磨性及抗高温氧化的能力。应用表明，使用寿命是普通喷煤枪的3～4倍。     

压制压力对粉末冶金烧结硬化钢性能的影响

研究压制压力(550、600、650、700、750 MPa)对粉末冶金烧结硬化钢(Fe-1%Mo-0.1%Mn-3%Ni-2%Cu-0.8%C)密度、显微组织以及力学性能的影响.结果表明:压制压力在550～750 MPa范围内逐渐增大时,烧结密度随之增加,但密度增量逐步减小,在600～650 MPa时密度增量达到最高,650～700 MPa密度增量有所降低,在700～750MPa密度增量趋近于0.当压力为700 MPa时烧结坯的密度及力学性能最佳.在1 200℃下烧结硬化合金钢的力学性能略高于在1 120℃烧结的.采用烧结硬化工艺烧结得到的合金钢力学性能与同等工艺条件下普通烧结后淬火处理的试样性能相近,但生产时间大大缩短.这对于实际生产中提高生产效率,节约生产成本有很大意义.     

烧结硬化材料在现代汽车齿轮、链轮、凸轮中的应用

近年来,汽车产业内部要求应用的材料需要具有高表观硬度、高淬透性以及提高力学性能。这些往往-矛盾的要求迫使寻找开发新材料,这些新材料必须不增大后续热处理的费用,能够提供较高的烧结态表观硬度及良好的静态/动态力学性能。传统的烧结硬化材料虽然提供适用的表观硬度,但力学性能与烧结体密度却不高。本文将用许多文献资料证明,一系列烧结硬化材料既有好的压缩性、高表观硬度,又能增高力学性能。将着重讨论这些材料在汽车(包括发动机与变速器)的,诸如齿轮、凸轮及链轮中的应用。这些零件当前是用压制-烧结-热处理工艺,或者是用常规的铸锻材料-切削加工制造的。还将讨论用高温烧结来强化生产工艺。     

渗铜烧结钢用高性能渗铜剂的研究及应用

介绍了国内外烧结钢用渗铜剂的研究现状,对国内外渗铜剂的性能进行了对比,分析了渗铜剂成分对熔渗性能的影响,指出了渗铜时的基体侵蚀和表面残留(粘附)产生的原因,提出了解决方法,对国内高性能渗铜剂的开发和应用提出了一些建议.     

WC对合金化烧结硬化钢的性能影响

应用粉末冶金烧结合金化及温压成形技术,制备了Fe-Mo-Mn-Cu-W-C烧结硬化钢摩檫材料,研究了该材料的组织结构和性能.结果表明:加入经过特殊处理的合金化元素后,烧结硬化钢的主要金相组织为珠光体、下贝氏体以及少量铁素体,材料的密度、强度、硬度及基体的耐磨性大幅度提高.Mn-Mo合金在高碳保护下加入到基体中,在烧结过程中产生了部分液相,因而促进了致密化过程.W以碳化物的形式加入到Fe-Mn-Mo-Cu-C烧结硬化钢基体中,起到了弥散强化的作用,材料的磨损量显著降低.     

烧结硬焊连接粉末冶金件的技术开发

在皮带滑座生产中，机械加工耗费了一半以上的工时，为此作者采用烧结硬焊技术，将皮带滑座制备工艺改变为皮带座硬焊接合滑座圆盘工艺。为评估不同商用硬焊填料在烧结炉中的熔融硬焊结合行为，将硬焊填料安置于粉末冶金试片结合处，再放入一般的铁系烧结炉中进行30min的烧结硬焊（烧结温度为1120℃、烧结气氛为裂解丙烷），观察不同硬焊填料在试片之间产生的扩散行为与结合状况，借以判定在铁系合金烧结条件下较适合的硬焊填料；而后将此硬焊填料应用于由烧结硬化合金钢所压制的皮带座与滑座圆盘的组合上。实验结果表明，硬焊填料适当的扩散能力，将促使填料与粉末冶金零件压坯间产生适当的扩散层，既维持大部分零件基体的原有特性，又能保留大量的硬焊填料存留于粉末冶金坯体间，因而形成渐层结构的高强度硬焊界面。与传统粉末冶金工艺相比，采用烧结硬焊技术后，皮带滑座的制造成本降低30％，而皮带滑座的结合力仅减小约10％。     

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。     

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。     

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.     

Comparison of the results of surgical and conservative treatment of fractures of the diaphysis of the tibia

In this paper is treated the fundamental problematic of the fracture of the diaphysis of the tibia and the therapeutic results after the conservative and operative treatment are confronted. Among 518 patients with 433 open fractures and 35 with closed fractures of the diaphysis of the tibia, successful treatment of more 2/3 was obtained in the period from 1968 to 1972. Following our casuistics and literature, whose results are similar, we find out that the average total treatment of the osteosynthesis of the fracture of the diaphysis was shortened for 2,5 months depending upon the type and the localisation of the fracture. Apolied methods of the operative and conservative and conservative treatment in relation to the velocity of the medical cure as well as to the extreme anatomical-functional results are analised. We noticed that osteosynthesis, made by the intermedullary nail and the extension of the canals or by a small AO table, by the achieved stability makes conditions of immediate motions and an early rehabilitation. Because of that it gives the best functional results.