Nb对0Cr11铁素体不锈钢组织和性能的影响

 铁素体不锈钢与奥氏体不锈钢相比具有成本低、热膨胀系数低和耐应力腐蚀等优点,所以被广泛应用到汽车排气系统、家用电器和建筑等领域。研究了不同的Nb含量对铁素体不锈钢显微组织和力学性能的影响。研究结果表明：Nb有细化晶粒的作用,随着Nb含量的增加,晶粒的平均尺寸减小;由于合金元素Nb和Ti的加入,形成了TiN、NbC 和 Fe2Nb析出相,其透射电镜观察结果与Thermal calc计算结果一致;材料的抗拉强度和显微硬度随着Nb含量的增加而增加,这是由于Nb的固溶强化和析出强化共同作用的结果。     

N含量对Nb微合金化HRB400E钢筋组织与性能的影响

摘要：为了更好地发挥N元素在Nb微合金化钢筋中的作用,降低生产成本以及为钢筋成分设计提供理论依据。利用金相显微镜、扫描电镜、透射电镜、力学试验机对不同N含量的Nb微合金化高强抗震钢筋进行显微组织表征及力学性能测试,探究N含量对Nb微合金化钢筋的组织与力学性能的影响。研究表明,轧制过程中的奥氏体组织,随着N含量的增加,平均奥氏体晶粒有所减小;最终组织为铁素体和珠光体,随着N含量的增加,铁素体平均晶粒尺寸而减小,片层状珠光体的连续性增加,片层间距减小;析出相Nb(C,N)随着N含量的增大,沉淀析出的第二项颗粒体积分数增大,颗粒尺寸随之减小;在力学性能方面,屈服强度逐渐增加,抗拉强度先增加后减少。     

铌钛对430铁素体不锈钢第二相析出及力学性能的影响

以不同铌钛含量的430铁素体不锈钢为试验材料,研究了稳定化元素铌钛对显微组织、析出相和力学性能的影响。通过拉伸试验、碳化物萃取试验,结合光学显微镜、透射电子显微镜、X射线衍射分析探究材料析出物的含量和类型及力学性能的变化规律。结果表明,430不锈钢中析出物主要为Cr23C6、Mn23C6和Cr7C3,具有较强的析出强化效果;单独添加Ti时,由于Ti的稳定化作用,析出物类型主要是Ti C和Ti N;粗大的Ti C对材料的力学性能产生不利影响;Nb、Ti双稳定化时,除Ti N以外较为粗大的Ti C被细小的Nb C取代;Nb、Ti的加入,不仅改变了析出相的类型,同时起到了析出强化和固溶强化的作用,使得材料的抗拉强度和塑性应变比分别达到433.60 MPa和1.37,显著改善了材料性能。     

12%Cr铁素体不锈钢的焊接热影响区组织特征

针对12%Cr铁素体不锈钢,利用光学显微镜、扫描电镜,对在不同焊接热输入条件下的显微组织种类进行观察,得出热影响粗晶区的组织变化规律;应用Thermal-cal软件,确定了12%Cr铁素体不锈钢在焊接热循环条件下发生相变的温度区间,以及微合金元素Ti和Nb的析出相图.给出在焊接热循环作用下,改善铁素体不锈钢焊接接头热影响区韧性的建议,即焊接热影响粗晶区存在适量的马氏体;钢中添加微量元素Ti可抑制粗晶区晶粒长大,其作用优于Nb.     

铌含量对17%Cr超纯铁素体不锈钢组织与高温强度的影响

随着汽车行业的发展,汽车排气系统热端用铁素体不锈钢的使用温度越来越高,高温性能成为限制其发展的关键性能。研究铌含量对铁素体不锈钢组织与高温性能的影响可以指导钢种设计和工业化生产。选取了2种17%Cr超纯铁素体不锈钢进行高温时效试验,结果表明:铌的质量分数为0.2%时,铌没有明显的强化作用,950℃高温下晶粒迅速长大,高温强度迅速降低;铌的质量分数为0.4%时,在950℃高温下时效,材料中析出弥散第二相粒子Fe2Nb,阻止晶粒长大,提高强度,防止高温引起的材料软化。材料的高温强度是由固溶铌以及铌析出物的共同作用引起的,当固溶铌析出形成析出物时,固溶铌含量减少引起的强度降低以及析出引起强度升高的竞争导致了材料的强度变化。     

高温时效对铁素体不锈钢组织和性能的影响

通过金相、SEM和EDS等技术,研究了900 ℃下不同时效时间对超纯铁素体不锈钢组织和性能的影响。结果表明,439钢种高温时效对Ti(C,N)析出作用较小,晶界析出相TiN较少,晶粒粗化严重,塑性较低;441钢种高温时效会沿着晶界析出Fe2Nb(Laves)相,析出数量较多,晶粒较细小,但由于Fe2Nb(Laves)相沿晶界呈网状分布,对材料塑性影响较大;444钢种高温时效会在晶界和晶内析出Fe3(Nb,Mo)3C,析出数量较少,第二相钉扎作用较弱,部分晶粒出现异常长大,由于Fe3(Nb,Mo)3C析出相未呈网状分布,断后伸长率高于441钢种。     

低碳锰(铌)钢控轧控冷实验研究

通过TMCP研究了低碳锰钢和添加微量Nb的低碳锰铌钢的组织和力学性能的影响因素.研究了Nb对实验钢显微组织和力学性能的影响.Nb的添加能够细化铁素体晶粒,促进铁素体转变,对贝氏体形成有一定的抑制作用.相对低碳锰钢来说,铌的加入减少了贝氏体的体积分数,贝氏体强化效果减弱,钢的屈强比升高.通过增加冷速和降低卷取温度,可以使低碳锰铌钢获得一定量的贝氏体,综合性能较佳.低碳锰铌钢的主要强化机制有细晶强化、贝氏体相变强化和析出强化.     

建筑维护系统用高耐蚀性铁素体不锈钢的研发与应用

研究了Mo、Nb、Ti对22.5%Cr铁素体不锈钢力学性能、耐腐蚀性能的影响,研究结果表明,Mo主要以固溶状态存在于铁素体不锈钢中,通过固溶强化提高了铁素体不锈钢的强度;在Ti/Nb双稳定铁素体不锈钢中,由于粗大TiN颗粒的形成和金属间化合物在晶界的析出,钢的韧性明显降低;在Nb单稳定铁素体不锈钢中,Nb以固溶状态和Nb(C,N)析出相存在于铁素体基体中,Nb(C,N)弥散分布于铁素体晶内,并作为σ相的形核质点,避免了σ相在晶界的析出,从而改善了钢的低温韧性。在此基础上研制出建筑维护系统用的高耐蚀性铁素体不锈钢B445R。测试结果表明,B445R在氯离子溶液中具有比316L更优越的耐点腐蚀性能,而且具有良好的成形性能和焊接性能,这些优点使其成为沿海地区建筑维护系统理想的装饰材料。     

Nb对热轧盘条组织性能的影响

采用C-Si-Mn和C-Si-Mn-Nb两种成分设计,结合高速线材生产的特点开发出了屈服强度345 MPa级高韧性热轧盘条.研究了Nb含量对热轧盘条显微组织、力学性能和低温冲击韧性的影响.结果表明,两种试验盘条显微组织均为铁素体+少量珠光体,含Nb盘条晶粒细小,且珠光体含量较少;Nb(C、N)在轧制和冷却过程中析出,提高盘条屈服强度和同圈性能稳定性;添加Nb元素明显提高热轧盘条低温冲击韧性.     

La对微合金高强钢组织及析出相的影响

借助场发射扫描电镜、X-射线衍射仪及电感耦合等离子发射光谱仪等检测手段,研究了La对微合金高强钢组织和析出相的影响。结果表明,实验钢显微组织均为粒状贝氏体、准多边形铁素体、少量板条贝氏体及残余奥氏体,析出相主要为Ti N、Ti C、Nb C、Nb Ti C2、Ti VC2。随La含量的增加,准多边形铁素体相比例降低,尺寸减小,贝氏体相增多且晶粒变小,残留奥氏体和细小析出相增多。     

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。     

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。     

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.     

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.     

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。     

参与式农业基地建设行动方案设计

为了编制实用性强的基地建设行动方案,首先,确定参与式发展的主体,搭建一个"决策框架";其次,针对行动目标,提出不同参与主体,如管理者、农民、消费者等团队与个人的目标及行动内容;最后,工作应向重塑伙伴式合作关系,挖掘农民自我发展潜力,完成三大角色的转换,打造农业基地文化等方向推进.