低压脉冲磁场凝固硅钢的热变形组织和行为

为了细化硅钢铸锭组织，提高其加工性能，研究了低压脉冲磁场对硅钢凝固组织的影响规律，并对比了不同凝固组织的热变形行为和组织。研究结果表明，在硅钢的凝固过程中施加脉冲磁场，传统的柱状晶组织转变为等轴晶组织。随着磁场频率的增加，等轴晶比率(等轴晶面积/整体面积)先增加后降低，等轴晶晶粒尺寸先减小后增大。随着励磁电压增加，等轴晶比率增加，等轴晶晶粒尺寸不断增加，获得最佳脉冲磁场工艺参数，磁场频率为5 Hz,励磁电压为200 V。在该脉冲磁场工艺参数下，硅钢凝固组织中的等轴晶尺寸细化至无磁场作用时的1/2,等轴晶比率提高至100%。对无脉冲磁场的柱状晶组织和施加脉冲磁场(磁场频率为5 Hz,励磁电压为200 V)的等轴晶组织，进行了热压缩试验(温度为950℃,应变速率为0.01 s^-1和0.1 s^-1)和热轧试验(初轧温度1 100℃)。通过微观组织结果发现，无脉冲磁场作用的柱状晶凝固组织在热压缩过程中发生少量动态再结晶，组织中存在难以消除的变形晶粒，影响后续加工性能。脉冲磁场作用下等轴晶凝固组织在相同热压缩条件下获得细小均匀的再结晶组织，平均晶粒尺寸...     

稳恒磁场对低碳锰铌钢γ→α相变的影响

用X－Y记录仪测定了低碳锰铌钢在稳恒磁场下的温降曲线,分析标定了奥氏体向铁素体转变的起始相变点,通过对空冷至不同温度后淬火试样金相显微组织的分析,研究了稳恒磁场对γ→α相变的影响。研究结果表明：在奥氏体化后的空冷过程中加入稳恒磁场,可以提高奥氏体向铁素体相变的起始温度。随着磁通密度的增大,铁素体相变点也随着提高,而且铁素体晶料得到了显的细化;稳恒磁场下小幅度的冷却速度变化对铁素体相变点的影响不大,但对铁素体晶粒长大过程的影响较大。     

低合金钢焊接粗晶区连续冷却铁素体相变规律

 利用焊接粗晶区连续冷却淬火方法,对比分析了钛处理钢和普通C Mn钢焊接粗晶区连续冷却不同阶段的相变组织,研究了铁素体相变规律。结果表明,C Mn钢焊接粗晶区主要为晶界铁素体+魏氏组织铁素体;钛处理钢焊接粗晶区主要为晶界铁素体+魏氏组织铁素体+晶内铁素体组织。在钛处理钢中,晶界铁素体、魏氏组织铁素体和晶内铁素体的相变开始温度相同,但各自长大的动力学条件不同。当晶内铁素体和魏氏组织铁素体竞争发生相变时,晶内铁素体在晶内弥散分布氧化物夹杂上的非均质形核抑制了魏氏组织铁素体向晶内的长大。     

连铸连轧生产25CrMo4齿轮钢带状组织的控制实践

通过调整连铸工艺参数与轧钢工艺参数,改善了25CrMo4齿轮钢带状组织。研究结果表明：在连铸坯凝固过程中,较大的电磁力促使连铸坯凝固时枝晶不断的重新发生迁移,微观枝晶的枝干与枝间分布更加均匀,由此产生的微观偏析也随之减小,连铸坯凝固过程中形成的一次带状组织得到改善。提升连铸坯在加热炉内的加热温度,碳元素以及合金元素相对富化区域的元素向贫化区域发生实质性的迁移速度也随之提升,铸坯前期因选择性结晶形成的无序分布枝晶组织加速均质化。钢材轧后采用风冷,其冷却过程钢材的铁素体与珠光体形核率较高,铁素体与珠光体分布更为细小均匀,轧材不易形成二次带状组织。     

铁素体不锈钢凝固组织的影响因素

 铁素体不锈钢凝固过程中形成的柱状晶会影响钢的成形性,减少甚至避免铸坯柱状晶的形成,促进等轴晶的形成,对铁素体不锈钢来说尤为重要。采用连铸和模铸的试验方法浇铸了铁素体不锈钢430,以分析影响其凝固结构的因素。结果表明,电磁搅拌对430不锈钢连铸坯等轴晶的形成作用显著。无论模铸试验还是连铸试验,冷却强度对430铸坯柱状晶的形成都有明显的影响。在模铸试验条件下,碳、氮含量越高,越有利于其凝固时等轴晶的形成;在连铸试验条件下,由于温度梯度大,碳、氮含量对凝固组织的影响被削弱,但如果对钢液进行搅拌,碳、氮含量的变化对凝固组织仍然有明显的影响。     

铌微合金化抗震钢筋形变奥氏体连续冷却转变

 为了研究铌对高强抗震钢筋生产过程中组织转变的影响,通过热模拟试验对比研究了无铌碳素钢筋及铌微合金化钢筋(铌质量分数为0.03%)形变奥氏体在不同冷却速率下的组织和相变规律,获得动态CCT曲线。研究结果表明,添加0.03%铌使试验钢奥氏体连续冷却转变有明显变化。从连续冷却曲线(CCT)可看出,添加铌后,发生先共析铁素体、珠光体相变的冷却速度范围减小,铁素体、珠光体转变温度降低;贝氏体相变的冷却速度区间整体右移。添加铌能细化组织,各冷却速度下含铌钢的硬度均大于无铌钢。利用TEM对不同冷却速度下含铌钢中析出相进行观察,发现Nb(C,N)弥散分布于钢中,随着冷却速度的增加,析出的Nb(C,N)逐渐减少,析出相尺寸呈先减小后增大的规律,2 ℃/s冷却速度冷却得到的析出相尺寸细小且数量较多。     

脉冲磁场强度对钛处理低碳钢凝固过程的影响

采用自发研制的脉冲磁场发生装置将脉冲磁场非接触式地施加到钛处理低碳钢的凝固过程中,利用金相显微镜、扫描电镜和能谱仪研究了不同强度的脉冲磁场对试样的宏观形貌、枝晶和组织的影响。结果表明,随着脉冲磁场强度的增加,试样的宏观表面逐渐变得平整;枝晶和组织随着脉冲磁场强度的增加逐渐细化,但达到一定强度后,继续增加又出现了相反的结论。由此可以推断,脉冲磁场强度对枝晶和组织的影响存在一个最佳值。     

热轧含钒微合金钢在加速冷却条件下的强化因素

讨论了含钒微合金钢在热轧及加速冷却条件下终轧温度，终冷温度，冷却速度对钢的力学性能的影响，加速冷却含钒钢的显微组织为细小的无边形铁素体和粒状贝氏体组织，由此获得相变强化。钒引起的碳化物析出强化，在加速冷却条件下得到加强，这是由于生成了大量的弥散细小的析出物，并且析出强化效果在６００℃冷却条件下最大。     

形变温度和冷却方式对中碳钢显微组织及拉拔性能的影响

采用Gleeble热模拟试验机研究了形变温度及冷却速度对ML35钢显微组织与硬度的影响;对比分析了10B21钢SM控冷盘条和板链式控冷盘条的显微组织差异,用Minitab软件统计分析了显微组织对盘条拉拔性能的影响。结果表明:当ML35钢形变温度为750℃时晶粒明显细化,部分珠光体发生退化,渗碳体呈短棒状或颗粒状,但硬度相对偏高;降低形变后的冷却速度可粗化晶粒,降低硬度;粗大的铁素体+珠光体组织比细小的铁素体+珠光体组织具有较高的初始加工硬化率;并且在初始变形过程中,具有相对粗大的铁素体+珠光体组织盘条的断后伸长率下降偏快。     

电磁场对改善钢材质量的作用

研究了电磁制动技术对结晶器内钢液流动及夹杂物迁移行为的作用,以及电磁搅拌和电磁超声波对钢材料凝固组织的影响。研究结果表明,在恒稳电磁场作用下,钢液内形成的与钢液流动相反的电磁力可有效地控制钢液流动、稳定液面波动,有利于夹杂物的去除;在电磁搅拌和电磁超声波的作用下,金属的凝固组织得到细化,等轴晶比率明显提高。计算了磁场对奥氏体／铁素体及铁素体／奥氏体平衡边界的影响,磁场对相图的奥氏体／铁素体界限产生很大影响,使其向高成分或高温度区域移动;随成分不同,磁场每增加1T,钢的Ae3温度升高2～3℃。研究了电场奥氏体化对中碳合金钢40MnMoV性能的影响,与常规工艺处理样品相比,电场奥氏体化可使其硬度值升高,且冲击性能和拉伸性能的指标都有所提高。     

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.