退火处理对热轧Fe-12Mn-8Al-0.8C轻质钢组织性能的影响

利用OM, SEM, TEM及XRD等,对不同退火温度下热轧Fe-12Mn-8Al-0.8C轻质钢的组织演变及力学性能进行了研究.研究结果表明,较低温度下退火时,实验钢组织为奥氏体+铁素体+κ-碳化物.随着退火温度的升高,实验钢中κ-碳化物发生溶解,奥氏体晶粒尺寸逐渐增加,实验钢的屈服强度和抗拉强度逐渐降低,伸长率则先增大后降低.不同退火温度下实验钢应变硬化行为的差异与其组织组成有关.750℃退火0.5 h的实验钢具有铁素体+κ-碳化物体积分数较高的复相组织,其加工硬化能力较高.随着退火温度的升高,铁素体与κ-碳化物的体积分数逐渐降低,应变硬化率有所降低,但应变硬化行为表现得更为持续.950℃退火0.5 h的实验钢与其他退火温度下的实验钢相比,获得了良好的综合性能,抗拉强度为930 MPa,伸长率为35.48%,韧脆转变温度约为-40℃.     

退火温度对冷轧中锰钢组织性能和断裂行为的影响

 为了系统研究临界区退火和全奥氏体区退火对中锰钢性能的影响,为中锰钢的实际应用提供理论基础,在650~900 ℃范围内系统研究了冷轧中锰钢的显微组织和力学性能,并通过断口形貌观察分析了试验钢的断裂特性。结果表明,试验钢在临界区退火的综合力学性能明显优于全奥氏体区退火。650~750 ℃退火时,抗拉强度在1 000 MPa左右,强塑积超过30 GPa·%,发生韧性断裂,宏观上可以观察到明显的层状裂纹,微观下为大量韧窝;在800~900 ℃退火时,抗拉强度在743~1 154 MPa范围内波动较大,强塑积不足10 GPa·%,断口平整,发生脆性沿晶断裂;退火温度为650 ℃时,组织为片层状和等轴状的奥氏体、铁素体双相及大量渗碳体;随着退火温度的升高,渗碳体逐渐溶解消失,等轴状组织所占体积分数明显增加,奥氏体体积分数也不断增加,在750 ℃时达到52.2%;退火温度为800 ℃时,有马氏体产生,奥氏体体积分数下降;退火温度为900 ℃时,组织基本为马氏体,残留奥氏体体积分数仅为14.6%。     

锰对贝氏体钢中残余奥氏体回火稳定性的影响

为探索锰含量的变化(锰质量分数为0.1%(0.1Mn钢)和1.5%(1.5Mn钢))对无碳化物贝氏体钢中残余奥氏体(RA)回火稳定性的影响,利用扫描电镜(SEM)、电子背散射衍射(EBSD)及透射电镜(TEM)等试验方法对残余奥氏体稳定性和力学性能的变化规律进行研究。结果表明,0.1Mn钢的热轧态组织主要是由粒状贝氏体(GB)+板条贝氏体(LB)组成,而1.5Mn钢的热轧态组织主要以板条贝氏体为主,且1.5Mn钢中残余奥氏体含量较高,屈服强度和抗拉强度均优于0.1Mn钢。在经过300～500℃回火后,残余奥氏体体积分数逐渐下降至完全分解,屈服强度和抗拉强度均表现为先升高后降低,但伸长率逐步增加。300℃回火性能最佳,原因主要是由于残余奥氏体在300℃回火中,块状残余奥氏体分解为过饱和马氏体/贝氏体,碳从过饱和马氏体/贝氏体中扩散至邻近残余奥氏体中使其含量增加,热稳定性得到提高,在拉伸的过程中产生了TRIP效应,从而使试验钢的强塑性得到提升。1.5Mn钢的性能明显优于0.1Mn钢,因为锰可以与碳产生协同作用共同促进奥氏体的稳定,提高伸长率,另外锰含量的增加使碳当量也提高,强度增强。基于修...     

超细晶钒微合金化双相钢性能

研究了钒微合金化对高强双相钢微观组织及性能的影响。与Fe-0.186C-1.5Mn-0.3Si-0.008N参照钢相比,加入0.14%V带来如下效果:(1)在冷轧及退火状态铁素体晶粒高度细化;(2)严重推迟在连续退火过程中铁素体向奥氏体转变的初始动力学;(3)慢冷条件下铁素体开始转变温度稍微提高,但珠光体和贝氏体转变被抑制,导致淬透性提高;(4)在临界退火温度≤740℃时观察到未溶渗碳体;(5)750℃/180 s退火后铁素体相中发现大量V(C,N)析出(平均直径7.4 nm),而马氏体(奥氏体)中析出物稀少,尺寸更大(平均直径13.4 nm);(6)不含钒参照钢抗拉强度随马氏体体积分数增量为~16 MPa/%,而含钒钢由于晶粒细化和铁素体选择强化,强度随马氏体含量变化增量相当低(~4 MPa/%),在马氏体体积分数45%变软。     

回火工艺对热轧U20Mn2SiCrNiMo贝氏体钢轨组织性能的影响

U20Mn2SiCrNiMo贝氏体钢轨的生产流程为150 t 转炉-LF-VD-280 mm×380 mm铸坯 轧制,终轧930~980 ℃,空冷-340 ℃ 4 h两次回火,空冷。U20Mn2SiCrNiMo钢热轧态(终轧930~980 ℃空冷）和(320 ℃一、二次回火)组织均由贝氏体、马氏体和残余奥氏体组成。力学性能试验结果表明：U20Mn2SiCrNiMo钢轨最佳回火工艺为320 ℃ 4 h空冷+320 ℃ 4 h空冷二次回火,其性能为：屈服强度1242 MPa,抗拉强度1393 MPa,HBW硬度值417,伸长率15.0%,断面收缩率60%,冲击吸收功K_U2 98 J,轨底纵向残余应力+180 MPa。     

临界退火温度对中锰TRIP钢组织和性能的影响

采用淬火热膨胀仪、扫描电镜、透射电镜、X射线衍射和拉伸试验机对0.2C-5Mn TRIP钢临界区相变行为、微观组织及力学性能进行了研究,并运用Factsage软件对0.2C-5Mn TRIP钢在临界区的相变热力学进行了计算,在此基础上讨论了临界区相变过程的特点。研究结果表明,临界区逆转奥氏体含量随着临界退火温度的升高而逐渐增加,逆转奥氏体中碳含量先增加后减少,Mn含量逐渐下降,逆转奥氏体热稳定性也逐渐下降。当临界退火温度为700℃时,在冷却过程中发生明显的马氏体相变;随着临界退火温度增加,渗碳体逐渐溶解,但由于相变时间较短,渗碳体无法完全溶解;当临界退火温度为600~675℃时,临界退火后的微观组织由铁素体、渗碳体和残余奥氏体构成。当临界退火温度为700℃时,临界退火后的组织由铁素体、残余奥氏体、马氏体以及少量未溶解的渗碳体构成;随着临界退火温度的升高,实验钢的工程应力-应变曲线变化显著,在675℃退火3min后获得最佳的力学性能,抗拉强度为1 138MPa,断后伸长率为23%。     

0Cr13C铁素体不锈钢冷拔断丝分析及工艺改善

0Cr13C钢(/%:0.02C,0.32Si,0.18Mn,0.016P,0.002S,12.25Cr,0.0140N)冷拔丝的工艺为Φ5.5mm热轧退火材(680~700℃退火)-冷拔至Φ2.0 mm材-氢气退火-冷拔至Φ0.70 mm丝-氢气退火-冷拔至Φ0.3mm丝。通过成分、断口、组织和力学性能分析,得出退火Φ5.5 mm热轧材为混晶组织,强度较高,造成冷拔时变形不均和断丝。通过720~760℃退火试验表明,随退火温度升高,抗拉强度降低,720、740、760℃退火后0Cr13C钢Φ5.5 mm热轧材的抗拉强度分别为471~503 MPa,417~448 MPa和378~417 MPa。生产结果表明,通过将Φ5.5mm热轧盘条的退火温度从原680~700℃2 h提高至740℃3~4 h,每台冷拔机的平均断丝率由6次/12 h降至2次/12 h。     

0.1C-5Mn钢两相区退火后的残余奥氏体与力学性能

通过ART(奥氏体逆相变)热处理工艺,研究了两相区退火温度对0.1C-5Mn钢中残余奥氏体与力学性能的影响。采用SEM、XRD、室温拉伸等分析测试手段,表征了试验钢组织形貌、亚稳奥氏体含量以及力学性能。结果表明,试验钢经ART工艺处理后,室温组织主要由铁素体与残余奥氏体组成;随退火温度升高,试验钢中出现碳化物析出与再溶解,同时板条状形变马氏体回复多边化形成等轴铁素体,颗粒状奥氏体过冷转变为板条状和块状马氏体;630、645、660℃退火1h试样中奥氏体体积分数相近,分别为18.4%、19.5%、18.8%,随温度升高,奥氏体含量骤降,大量逆相变奥氏体转变为马氏体;综合不同退火温度,表明试验钢经660℃退火可获得最佳的综合力学性能。     

逆相变退火对连铸坯组织和力学性能的影响

 研究了逆相变退火温度对0.1C5Mn钢连铸坯的组织结构和力学性能的影响规律,采用SEM进行组织结构的表征,利用XRD技术分析连铸坯退火后奥氏体含量,并测试了退火试样的力学拉伸性能。试验结果表明,连铸坯退火过程中发生奥氏体逆转变且在较低退火温度下有少量碳化物析出,随着退火温度升高,奥氏体含量先增加后减少,析出物逐渐溶解消失。提高退火温度可以显著提高试验钢的抗拉强度但却降低它的屈服强度,另外随退火温度升高,断后伸长率和强塑积先增高后降低。在625~650℃退火,可以获得20%~25%的伸长率。研究结果说明利用逆转变退火可以大幅度提高中锰钢铸坯的力学性能。     

终轧温度对低硅含磷系TRIP钢组织性能的影响

通过实验室热轧试验,研究了不同终轧温度下低硅含磷系热轧TRIP钢的组织特征及性能特点。结果表明：终轧温度由900℃降低到790℃,铁素体体积分数增加,贝氏体体积分数降低,残余奥氏体体积分数变化不太明显;终轧温度900和820℃时,得到贝氏体为基体的室温组织;终轧温度降低到790℃时,低温变形促进了奥氏体到铁素体的相变率...     

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.