Mg处理石油储罐用钢大线能量焊接性能研究

采用Gleeble对不同焊接线能量下微量Mg处理石油储罐用钢粗晶热影响区(CGHAZ)的低温韧性进行了研究,并结合SEM,TEM等技术对CGHAZ进行了微观分析.结果表明:经微镁处理690MPa级石油储罐用钢,改变了钢中夹杂物的形态和分布状态,使钢中原有的氧化铝和硫化物夹杂物变成细小的弥散分布的含镁夹杂物,提高母材与焊接热影响区性能;随着线能量的增加,微镁处理690MPa级石油储罐钢CGHAZ的M-A组元均随着线能量的升高而粗化,M-A组元面积百分数随线能量的升高而降低,导致其低温冲击韧性降低.     

石油储罐钢焊接热影响区模拟研究

采用焊接热模拟技术,研究不同焊接热输入条件下焊接热循环对石油储罐钢焊接热影响区粗晶区(CGHAZ)的组织和性能的影响.结果表明:实验钢在80～100kJ/cm的大热输入下,热影响区仍能够保持良好的低温韧性;随着焊接热输入的增加,实验钢CGHAZ组织变粗大,低温冲击功下降;钢中弥散分布着大量细小TiN粒子,在焊接热循环中...     

20钢管焊缝开裂分析

通过对焊管理化检测及断口分析，确认了焊缝开裂是由于钢中存在着大量的MnS夹杂物，在高频焊接时，又在焊缝区，熔合区和热影响区形成了较多球状MnS夹杂和大块状铁的氧化物及硫氧复合型夹杂物，并在热应力作用下产生了微裂纹。在上述因素下，钢管在压扁试验时即产生开裂。     

焊接热输入对耐热钢埋弧焊(SAW)焊缝金属冲击韧性的影响

耐热钢因具有优异的焊接性能和加工性能而被广泛应用于许多制造工业。为了提高焊接接头的性能,同时延长构件的使用寿命和提高工作效率,选择合适的焊接热输入是非常重要的。本工作研究不同焊接热输入对耐热钢埋弧焊焊缝金属冲击韧性的影响。通过夏比冲击试验测试不同焊接热输入下焊缝金属的冲击韧性。利用扫描电镜、光镜和显微硬度等手段分析不同热输入下焊缝金属冲击韧性差异的原因。高热输入焊缝金属对应显微组织是块状铁素体、链状分布的碳化物和大尺寸的夹杂物。较大尺寸夹杂物越容易使裂纹形核。更多硬脆碳化物相的聚集导致裂纹形核扩展越容易。造成不同焊接热输入下耐热钢埋弧焊焊缝金属冲击韧性波动的原因是焊缝金属组织的不均匀,高热输入下出现的粗大块状铁素体、链状碳化物、块状M-A组元和较大尺寸的夹杂物导致冲击韧性的降低。     

氮对钒微合金钢粗晶热影响区(CGHAZ)的组织和性能的影响

用热模拟方法研究了氮含量对钒微合金钢粗晶热影响区(CGHAZ)的组织和性能的影响。结果表明,氮含量为0.0031%或0.021%时,CGHAZ的韧性较差。氮含量0.0031%时CGHAZ中有少量的Ti(C,N),晶界铁素体(GBF)较少,晶内有大量尺寸较大的侧板条铁素体(FSP),解理裂纹沿FSP的直线扩展使其韧性较差。氮含量0.021%时在CGHAZ中生成了较为粗大的(Ti, V)(C, N)和GBF,解理裂纹沿GBF扩展使其韧性较差。氮含量为0.012%时低温韧性较好,在CGHAZ中生成了大量细小的(Ti, V)(C, N)粒子,且GBF尺寸相对较小,晶内有大量的针状铁素体(AF)。这些因素都有利于阻止裂纹扩展,使其低温韧性显著提高。     

热加工对硫化物及氧化物夹杂的影响

随着制造业的发展,人们对钢材的质量提出了更高的要求,而夹杂物是影响钢材质量十分重要的因素之一.特别是对高强钢而言,夹杂物对其韧性的影响更加敏感.因此,研究冶炼过程中对夹杂物的控制及后续热轧和热处理工艺对钢中夹杂物的影响,是钢铁材料制造和加工过程中的一个重要课题.夹杂物对钢材的强度、塑性、韧性、抗疲劳性能、耐腐蚀性能都会产生重要影响.要减少夹杂物对钢材性能的影响,需从优化冶炼工艺开始.随着气泡去除夹杂物技术、真空碳脱氧技术及中间包电磁搅拌技术在冶炼过程中的应用,钢材中的夹杂物含量明显降低.然而,在目前工业化的生产环境中,仍然无法实现将钢中的非金属夹杂物完全消除.目前的研究已经表明,热轧和热处理过程对夹杂物也有重要影响,这对进一步控制夹杂物的尺寸、分布、形态,达到减轻夹杂物对钢材性能影响的目的具有重要的意义.因此,目前除了发展新的冶炼工艺以进一步降低钢中的夹杂物含量外,研究和阐明热加工工艺对夹杂物的影响也是研究重点.文中归纳了冶炼过程中先进的夹杂物控制技术及其原理,评述了热变形和热处理过程对夹杂物的数量、尺寸、分布、形态特征及类型产生的影响,对研究钢材在制造、加工过程中夹杂物的变化规律及控制具有参考价值.     

热输入对E40钢双丝埋弧焊焊缝组织及性能的影响

为研究最新研制的大热输入焊接所用低合金高强实心焊丝G55,对大热输入用钢E40进行热输入分别为60、122、158 kJ/cm的双丝埋弧焊焊接.经过拉伸、冲击试验及光学显微镜、扫描电镜和透射电镜分析,对焊接接头焊缝组织性能进行研究,并对接头强韧性进行分析.结果表明:不同热输入焊缝组织均以针状铁素体组织为主;随着热输入的增加,焊缝冲击韧性增加,这是因为焊接热输入增加时,柱状晶比例减小、宽度增加,针状铁素体含量增加;焊缝中含氧量减少,夹杂物数量减少;焊接道次减少导致块状铁素体含量减少等三方面因素.随着热输入的增加,焊缝金属强度提高,主要是因焊缝针状铁素体组织含量增加.     

钒-钛微合金化钢焊接热影响区晶内铁素体与夹杂物的界面关系

采用聚焦离子束方法制备试样,利用最高加速电压为1 300 kV的高分辨电镜观察钒-钛微合金化钢100 kJ/cm大线能量热模拟焊接热影响区,对作为晶内铁素体形核核心的夹杂物形貌与结构及夹杂物与晶内铁素体界面关系进行了研究.结果表明,晶内铁素体在MnS V(C,N)复合夹杂物相上形核析出,夹杂物和晶内铁素体存在确定的晶体学位向关系.     

定向铸造镍基高温合金Hf夹杂的特征及成因

采用扫描电镜、透射电镜和能谱技术，详细分析DZ125和DZ22镍基高温合金中富Hf夹杂物的形貌、结构及成分，开展不同Hf添加量的镍基合金凝固组织特征的模拟实验探究，阐明Hf夹杂物的形成机理。结果表明：DZ125和DZ22合金铸件的边缘均存在不规则形态的夹杂物，其中白亮夹杂物为HfO₂,与之伴生的灰色夹杂物中含有Al₂O₃。镍基高温合金中的Hf元素聚集倾向强，Hf含量较高时可形成百微米以上的大尺寸富Hf相，随着Hf含量降低，富Hf相减小且分布更为均匀。高温下Hf与熔体中的氧、陶瓷型壳/型芯氧化物具有高的自发反应驱动力，当Hf分散不充分时，Hf倾向于向氧化物陶瓷相/熔体的界面聚集，在高温下与陶瓷中的Al₂O₃和硅溶胶黏结剂中的SiO₂发生反应，从而导致铸件表层HfO₂夹杂物的形成。     

钢中非金属夹杂物对疲劳性能的影响

本文研究了38CrMoAlA和30CrMnSiA两种钢中所含夹杂物对疲劳性能的影响。研究结果表明:在夹杂物含量基本相同的条件下,夹杂物的大小、形状及分布特徵对疲劳寿命具有明显的影响。夹杂物的颗粒大小直接支配着裂纹的成核与扩展,当夹杂物的平均直径大于40μm时,由夹杂物引起疲劳失效的比率可达95％以上。因此,在控制夹杂物含量的基础上,通过减小夹杂物颗粒尺寸和改变不利的几何形状及分布,可减缓夹杂物对疲劳性能的有害影响。     

Gender differences in publication productivity in psychology in India

An analysis of gender differences in psychology in India provides quantitative and qualitative assessment of R&D output contributed by psychologists with the indication of the trend of growth, skewness, relatedness, co-authorship pattern of productivity.     

Metrology in Chemistry in Germany

The system for Metrology in Chemistry in Germany is described. At the national standards level, a network of high-level chemistry institutes coordinated by the national metrology institute, PTB, provides the primary references for chemical measurements. A dissemination mechanism employs chemical calibration laboratories accredited within the framework of the German Calibration Service (DKD). They act as “multipliers” between the national standards level and the user level by providing the user with calibration means which are traceable to the SI via national standards. Traceability structures in clinical chemistry, electrochemistry, elemental analysis and gas analysis are described     

Natural radioactivity in drinking water in private wells in Finland

Natural radioactivity in drinking water was determined in population-based random study of 472 private wells. The mean concentrations of (222)Rn, (226)Ra, (234)U, (238)U, (210)Pb and (210)Po in drilled wells were 460, 0.05, 0.35, 0.26, 0.04 and 0.05 Bq l(-1), and in wells dug in the soil were 50, 0.016, 0.02, 0.015, 0.013 and 0.007 Bq l(-1), respectively. Approximately 10% of the drilled wells exceeded a radon concentration of 1000 Bq l(-1) and 18% a uranium concentration of 15 microg l(-1). The mean annual effective dose from natural radionuclides for a drilled well user was 0.4 mSv and 0.05 mSv for a user of a well dug in the soil. The effective dose arising from (222)Rn was 75% of the total of all natural radionuclides for drilled well users. As regards long-lived radionuclides, (210)Po and (210)Pb caused the largest portion of the effective dose. The dose arising from (238)U, (234)U and (226)Ra was only 8% of the total of all natural radionuclides.     

Natural radioactivity in drinking water in private wells in Finland

Radiation Protection Dosimetry     

Radioactivity in building materials in Iraq

Activity concentrations of (226)Ra, (232)Th and (40)K in 45 samples of different building materials used in Iraq were measured using gamma-spectroscopy system based on high-purity germanium detector with an efficiency of 40 %. Radium equivalent activity, air-absorbed dose rate, annual effective dose, external and internal hazard indices and alpha index due to radon inhalation originating from building materials were measured to assess the potential radiological hazard associated with these building materials. The activity concentrations of the natural radionuclides (226)Ra, (232)Th and 40K were found to range from below detection limit (BDL) to 223.7 ± 9, BDL to 93.0 ± 3 and BDL to 343.1 ± 12, respectively. Values of average radium equivalent activity, air-absorbed dose rate, indoor and outdoor annual effective doses, external and internal hazard indices and alpha index ranged from 6.5 to 124.9, 16.2 to 89.5 (nGy h(-1)), 0.08 to 0.44 mSv, 0.02-0.11 mSv, 0.09 to 0.53, 0.13 to 0.69 and 0.03 to 0.62, respectively. These values indicate a low dose. Therefore, the building materials used in the current study are quite safe to be used as building materials.     

Optische in situ Schichtdickenmessung in Bedampfungsanlagen. Optical in situ film thickness monitoring in coating systems

Optical film thickness monitoring is more precise than crystal monitoring. The optical measurement makes use of the fact that the intensity of a monochromatic light beam which is reflected on a film will change periodically with increasing film thickness. The measurement is performed at an exchangeable test glass that is positioned beside the substrates and is therefore coated in the same way as the substrates. The accuracy of cut‐off is achieved by a “fit” of a theoretical curve shape to the measured values. Order filters are used to ensure that, at a certain wavelength, higher deflection orders do not influence the measurement when a monochromator grating is used.