M50NiL轴承钢淬回火组织特征及拉压疲劳裂纹的萌生

摘要：通过拉压疲劳试验及微观组织观察研究了M50NiL轴承钢淬回火组织特征及对疲劳裂纹萌生的影响作用。结果表明,试验钢的组织主要为板条马氏体,少量δ-铁素体及M2C、MC碳化物;扫描电镜观察发现1070℃淬回火试样δ-铁素体及临近的聚集球状M2C碳化物,δ-铁素体位于晶界处,尺寸主要为4~8μm,钢中碳化物尺寸最大为2.66μm;1100℃淬回火试样δ-铁素体相界存在大量片状的M2C碳化物,尺寸在8μm以上的δ-铁素体数量增加,最大为17.51μm;1070℃淬回火试样的疲劳极限为713MPa,主要起裂源为Al2O3、Al2O3-CaO夹杂物,循环次数随夹杂物尺寸的增大而降低,且Al2O3-CaO夹杂更易引起试样的疲劳断裂;1100℃淬回火试样的疲劳极限为707MPa,主要起裂源为δ 铁素体组织缺陷,起裂源于8μm以上δ-铁素体的相界处,疲劳寿命受应力及δ-铁素体尺寸影响。     

38MnVS非调质钢的缺口高周疲劳破坏行为

锻件截面尺寸变化及表面加工缺陷所引起的应力集中往往会导致其早期疲劳失效,因而要求钢材具有高的缺口疲劳性能和低的疲劳缺口敏感度。为了明确非调质钢的缺口疲劳破坏行为,采用旋转弯曲疲劳试验机研究了一种锻造用中碳非调质钢38MnVS在不同应力集中系数Kt(1、2、4)下的高周疲劳破坏行为。结果表明,试验料的光滑和缺口疲劳S-N曲线均存在明显的疲劳极限,Kt对试验料的疲劳极限和疲劳缺口敏感度qf具有显著的影响,当Kt从1(光滑试样)提高到2和4时,疲劳极限分别降低了48%和67%,qf值分别为0.93、0.68,呈现出较高的疲劳缺口敏感性。试验结果及文献数据的拟合分析表明,可采用Kt的幂函数来表征试验料的缺口疲劳极限,并提出了预测铁素体+珠光体型非调质钢在不同Kt下疲劳极限的一种简便高效方法。     

一种新型胀断连杆用中碳非调质钢

 采用降低铁素体相韧性、提高铁素体相硬度及适当脆化原奥氏体晶界的方法,开发出一种新型胀断连杆用铁素体-珠光体型中碳非调质钢,从钢种设计、微观组织、力学性能及胀断特征等方面对此钢种进行了介绍。硅和磷元素的铁素体固溶强化作用及钒元素析出强化和组织细化作用,使得开发钢不仅具有较高的强度水平和屈强比,同时具有远高于传统的胀断连杆用高碳钢C70S6的优异高周疲劳性能。此外,模拟胀断试验结果表明,开发钢的断口呈典型脆性解理断裂,胀断前后的变形量很小,具有优于C70S6钢的胀断性能,可采用胀断工艺制造连杆。     

7475-T7351铝合金抗疲劳性能研究

采用旋转弯曲疲劳试验、轴向加载疲劳试验、疲劳裂纹扩展速率试验等疲劳性能测试方法,研究了7475-T7351铝合金厚板的疲劳性能.并通过透射电镜(TEM)和扫描电镜(SEM)分析了该合金的显微组织和疲劳断口形貌.结果表明:7475-T7351铝合金具有良好的耐疲劳损伤性能,光滑试样(Kt=1)在室温旋转弯曲和高温轴向加载条件下的疲劳极限分别为180.0和345.0 MPa,缺口试样(Kt=2.2)在室温旋转弯曲加载条件下的疲劳极限为91.9 MPa;合金厚板材料在高温下缺口敏感性有所降低;国产材料裂纹扩展速率随应力比增加而增大,裂纹扩展门槛值减小;国产7475铝合金与进口材料在裂纹稳定扩展阶段裂纹扩展行为基本相当;在近门槛值附近不同应力比下的裂纹扩展门槛值略有差别.     

微镁处理对车轮钢组织与性能的调控作用

为揭示Mg在低碳微合金钢中的作用,以HR60车轮钢为研究对象,分别进行实验室感应炉试验和工业试验。采用OM、SEM-EDS和INCA定量统计等方法对比不同处理钢中典型夹杂物特征和微观组织形貌,并对试验钢的力学性能进行测定。结果表明:Mg处理后,钢中Al_2O_3夹杂变质为细小的MgO·Al_2O_3夹杂物,且含Mg夹杂物粒子可有效诱导针状铁素体形核,组织由"多边形铁素体(PF)+珠光体(P)"向"多边形铁素体(PF)+针状铁素体(AF)+退化珠光体(DP)"演变,组织得到细化;Mg处理后,车轮钢强度提高,工业试验钢中,Mg处理钢疲劳极限均大于460MPa,Ca处理钢疲劳极限在450MPa左右,Mg处理钢的疲劳寿命普遍优于Ca处理钢;实验室试验中,降低Nb、Ti含量,当钢中Mg的质量分数为18×10-6时,车轮钢的强度接近基准钢,认为利用Mg的微合金化作用来降低生产成本的方案具有可行性。     

中碳非调质钢的高周疲劳性能

非调质钢常用来代替调质钢制造用于疲劳设计的运动部件,因而改善其疲劳性能十分重要.对于铁素体一珠光体型非调质钢,由于存在软相铁素体,其疲劳裂纹基本上萌生于试样表面的铁素体/珠光体边界,并优先沿着该边界扩展.因此,强化铁素体、改善铁素体的分布状态和组织细化是改善其疲劳性能的关键.研究结果证实,具有粗大网状铁素体一珠光体组织...     

CSP流程中B对低碳Al镇静钢组织及力学性能的影响

研究了B元素对CSP流程生产的低碳Al镇静钢热轧钢带的组织及力学性能的影响,探讨了B元素在CSP流程中的析出规律及对AlN和MnS析出行为的影响.试验结果表明:B元素能够起到使钢带组织软化的作用.在连铸过程中B与N结合形成粗大的BN粒子,减少了钢中固溶氮的质量分数,抑制AlN细微颗粒的析出,减少了铁素体组织细晶强化及AlN析出强化的作用,从而降低了材料的强度.     

控轧控冷中碳非调质钢的高周疲劳性能

 采用中碳非调质钢制造的轴类等零件常承受交变载荷，因而对钢材疲劳性能具有高的要求。为了评估控轧控冷工艺生产的非调质钢棒材的疲劳性能，利用旋转弯曲疲劳试验机研究了一种常用的钒微合金化中碳非调质钢38MnVS及对比钢38MnS的高周疲劳性能。结果表明，与38MnS钢相比，38MnVS钢中铁素体体积分数增加，组织明显细化；相分析表明约有54%的钒处于M（C，N）相中，且尺寸小于10 nm的M（C，N）粒子质量分数为32%，这些细小粒子的析出强化增量约为116 MPa。38MnVS钢的疲劳极限较38MnS钢提高了62 MPa，提高幅度约为18%；疲劳极限比从38MnS钢的0.43提高到38MnVS钢的0.48。M（C，N）相的析出强化及组织细化是38MnVS钢较38MnS钢具有优异疲劳性能的主要原因，但其疲劳性能仍低于锻态非调质钢。根据试验结果及文献数据，给出了预测铁素体＋珠光体型非调质钢疲劳极限的简便方法。     

DP980钢及DP980钢激光焊接接头的高周疲劳性能

摘要：为了研究DP980钢的高周疲劳性能,采用疲劳试验机对DP980钢和DP980钢激光焊接接头进行高周疲劳试验,得到Basquin方程,并利用光学金相显微镜和扫描电镜进行组织和断口分析。结果表明：DP980钢激光焊接接头的焊缝根部和顶部出现形状凹陷,焊接接头的质量为中等。DP980钢疲劳极限为341MPa,DP980钢激光焊接接头的疲劳极限为148MPa,激光焊接接头的疲劳极限较母材的疲劳极限降低约50%。对于DP980钢而言,铁素体/马氏体晶界是裂纹萌生的主要位置,疲劳断口为准解理断口。对于DP980钢激光焊接接头而言,疲劳裂纹源位于焊缝凹陷处,而非热影响区及母材,疲劳断口为解理断口。DP980钢和DP980钢激光焊接接头的疲劳裂纹扩展区均有明显的疲劳条带,并伴随有二次裂纹。     

一种含Ti冷轧热处理双相钢的组织性能研究

介绍了含0.085%Ti微合金元素的780 MPa级冷轧热处理双相钢的试制工艺流程,观察和测试了试验钢的组织,织构和性能,并与相关学者的类似研究做了比较.结果表明:试验钢经过连退工艺后,获得了多边形铁素体和分布在铁素体晶界上的岛状马氏体组织,并有少量贝氏体存在;Ti的添加有细晶强化和沉淀强化的作用,经连退热处理后试验钢的强度达到780 MPa级,拉伸时铁素体中的TiC颗粒钉扎和阻碍位错运动,试验钢出现屈服平台;连退后试验钢组织中铁素体晶粒间多为大角度晶界,且α纤维织构较强,γ纤维织构较弱.     

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.