三峡工程永久船闸区地下水腐蚀性评价分析

长江水利委员会在三峡水利枢纽初步设计勘察阶段对三峡工程坝址区地下水的腐蚀性进行了明确的评价,即除少数泉水外,绝大多数地下水对砼不具有腐蚀性。2000年1月,永久船闸南北两侧共14条排水洞内出现Ca质析出物和红棕色Fe质析出物后,人们一方面质疑初勘阶段关于地下水对砼腐蚀性评价的准确性,怀疑地下水对砼可能具有腐蚀性;另一方面想弄清地下水对保证船闸高边坡稳定至关重要的锚索、锚杆是否具有腐蚀性等,以便设计决定是否需采取措施及采取何种措施,以确保永久船闸高边坡稳定。为此,对地下水腐蚀性进行了专题研究。通过对地下水的各种可能补给源以及不同空间位置的地下水的对比、分析和研究,并结合前期勘察阶段地下水化学试验成果,对永久船闸区地下水的腐蚀性进行了评价。     

鄂尔多斯盆地靖边气田前石炭纪古地貌解释新模式

近年来,鄂尔多斯盆地靖边气田在原有古地貌解释模式下部署的多口勘探开发井钻探均告失利,二维地震储层预测准确率下滑至70%以下,制约了该区天然气勘探的进程。为此,在综合分析已有古地貌恢复方法优缺点的基础上,根据印模法、残余厚度法的基本原理,结合钻井、测井资料,创建了一种考虑古构造影响的定量古地貌恢复方法,并利用该方法对该气田进行古地貌恢复与侵蚀沟槽重新解释。研究结果表明:(1)该区下古生界储层沟槽解释模式由原来的"东西向大型侵蚀沟槽、南北向毛细沟槽模式"修正为"东西侵蚀主沟槽与局部侵蚀潜坑并存"新模式;(2)较之于原预测结果,下古生界侵蚀主沟槽东西向长度缩短近1/2,毛细沟槽发育范围较小,局部被半径介于1~15 km的潜坑替代;(3)据重新解释的成果,该区下古生界气藏可扩大含气面积305 km~2,预计可建天然气产能4.5×10~8 m~3/a。2016—2017年,利用该研究成果在原解释的沟槽内部署井位30口,目前已完钻8口井,7口井下古生界奥陶系马家沟组马五1+2亚段储层保存完整,其中5口井试气的平均无阻流量为14.3×104 m~3/d,证实新方法能准确地对该区古地貌进行定量化表征、提高储层预测的准确率。     

基于DPM模型的铅铋合金中颗粒物对管道冲蚀的数值模拟研究

基于流体力学理论研究液态铅铋合金（LBE）流体中颗粒物对管道壁面的冲蚀作用,采用Fluent软件中的离散相模型（DPM）对管壁的冲蚀进行数值模拟研究。结果表明,弯管角度、颗粒粒径、颗粒物浓度、管道的管径以及流速等对管壁的冲蚀磨损产生明显影响,其中,流速影响较大,在高流速下的冲蚀严重;弯管角度的影响显著,对直管段的冲蚀较弱,对弯管角度在30° ~ 90°之间的管道的冲蚀比较严重;颗粒粒径在1 ~ 9 μm内的微颗粒对管道冲蚀影响较小,粒径增大到10 ~ 90 μm时,冲蚀速率变化不明显,粒径增大到100 ~ 900 μm时,大直径的颗粒对管道冲蚀严重。      

Erosion corrosion of low-alloy wear-resistant steels in alkaline slurry

Erosion corrosion causes significant problems in various industrial environments through a synergistic effect which results in much greater weight loss than the sum of the weight losses in the individual processes. The erosion-corrosion behavior of three low-alloy steels was investigated in a simulated concrete slurry using the rotation method. The key influencing factors and mechanism of material degradation were analyzed. The experimental results indicate that the weight loss increases with the linear velocity according to a nearly exponential relationship (W = KVⁿ), where n is 1. 40–2. 14. This weight loss is mainly caused by erosion in the alkaline slurry, and steels with higher tensile strengths show higher erosion-corrosion resistance. The formation of many platelets and ring cracks and their removal from the sample surface during erosion corrosion in the slurry are thought to constitute the mechanism responsible for this weight loss. These platelets and ring cracks are formed by solid particles striking the sample surface. Craters are initially produced and subsequently disappear as they grow and come in contact with each other. Fewer craters were observed on the surfaces of samples that exhibited higher weight loss. The surface of the material became work-hardened because of the effect of the particles striking and scratching, and a deformed layer was produced on the surface for steels of lower strengths, leading to deeper and more abundant gouges.     

沙钢2500m~3高炉炉缸侧壁三角形侵蚀的原因分析

沙钢宏发1#高炉(2 500 m3)在2011年年初大修,发现炉缸侧壁在竖直方向呈现出巨大的三角形侵蚀,侵蚀最大处位于炉壳拐点部位,不同于传统的"象脚型"侵蚀。为了调查炉缸部位三角形侵蚀的原因,对炉缸的热应力分布进行了分析,发现竖直方向的正应力对炉缸的侵蚀影响较大,热应力首先集中在炉缸侧壁靠近底部的地方,侵蚀逐渐向碳砖方向发展,当碳砖完全暴露于铁水中后,在残留陶瓷杯和碳砖交界处产生了一条裂纹,该裂纹逐渐向上发展至炉壳拐点上方,待裂纹停止后,随着铁水的流动和有害元素的破坏,炉缸部位逐渐形成了巨大的三角形侵蚀。     

Bulk transportation of sand particles in quantitative simulations of dune field evolution

Bulk transportation of sand particles is a key process controlling and quantifying the evolution of aeolian dune field. Sand amount eroded by wind within a given period is usually depicted in terms of ‘sand body elements’, whose thickness and transportation distance have direct impact on the accuracy of simulated spatiotemporal scales and the efficiency of quantitative simulations. This paper presents a detailed analysis to the rule of determining the thickness and transportation distance of ‘sand body elements’, which can be described in analytical formulas with respect to sand diameter, frictional wind velocity, and time interval of computational simulations. Following this model, the efficiency of quantitative simulations of dune field evolution is greatly enhanced without losing accuracy.     

The wear of ultrafine WC–Co hard metals

The wear performance of ultrafine-grained tungsten carbide–cobalt (WC–Co) hard metals during three-body abrasion and particle erosion has been evaluated and compared to that of similar conventional coarser grained hard metals. The tungsten carbide grain size varied between 0.5 and 3 μm with cobalt contents ranging from 6 to 15%. Silica particles were used in both forms of testing. Erosion was carried out at 60 ms⁻¹ at an impact angle of 75° and abrasion at a velocity of 0.5 ms⁻¹ and a load of 50 N.

The wear resistance of the ultrafine grades was found to be at least double that of the closest conventional fine grained hard metals. These increases in wear performance are considerably higher than any corresponding increase in hardness which is, at most, 25% and is not achieved at the expense of fracture toughness which is maintained at a similar level to that of conventional fine grained hard metals. The increase in wear resistance coincides with a change in the mechanism of material removal. Sub-micron materials experience ductile deformation and bulk removal of material whilst coarser grades display more localised response with extensive fragmentation of the WC grains.     

通气对空化引起振动的影响

为了研究通气对旋旋涡空化所引起振动的影响,把不同量的气体通入射流放水阀阀针后部的旋涡空化区。分别在通气和不通气条件下,用安装在分流栅区域阀壁上的加速度仪测量了空化所引起的振动,通过快速富立中变换（FFT）分析了振动加速度的频段分布和强度,发现旋涡空化所引起振动主要发生在10KHZ－23KHZ的频段范围内。通气可以有效地抑 生的振动强度,随通气量的增加振动强度逐渐降低,实验表明,随空气化的减小相同通气量条件。对振动的影响逐渐变弱。     

Erosion behavior of SiC–WC composites

Dense silicon carbide (SiC) ceramics were prepared with 0, 10, 30 or 50 wt% WC particles by hot pressing powder mixtures of SiC, WC and oxide additives at 1800 °C for 1 h under a pressure of 40 MPa in an Ar atmosphere. Effects of alumina or SiC erodent particles and the WC content on the erosion performance of sintered SiC–WC composites were assessed. Microstructures of the sintered composites consisted of WC particles distributed in the equi-axed grain structure of SiC. Fracture surfaces showed a mixed mode of fracture, with a large extent of transgranular fracture observed in SiC ceramics prepared with 30 wt% WC. Crack bridging by WC enhanced toughening of the SiC ceramics. A maximum fracture toughness of 6.7 MPa*m^1/2 was observed for the SiC ceramics with 50 wt% WC, whereas a high hardness of 26 GPa was obtained for the SiC ceramics with 30 wt% WC. When eroded at normal incidence, two orders of magnitude less erosion occurred when SiC–WC composites were eroded by alumina particles than that eroded by SiC particles. The erosion rate of the composites increased with increasing angle of SiC particle impingement from 30° to 90°, and decreased with WC reinforcement up to 30 wt%. A minimum erosion wear rate of 6.6 mm³/kg was obtained for SiC–30 wt% WC composites. Effects of mechanical properties and microstructure on erosion of the sintered SiC–WC composites are discussed, and the dominant wear mechanisms are also elucidated.     

Solid particle erosion behaviour of hardfacing deposits on cast iron—Influence of deposit microstructure and erodent particles

Solid particle erosion (SPE) behaviour of different hardfacing electrodes deposited on gray cast iron (ASTM 2500) was studied using quartz sand and iron ore as erodent particles. Erosion test was carried out as per ASTM G76 test method. Considerable differences in erosion rates were found among different hardfacing electrodes at normal impact. Both volume fraction of carbides and type of carbides played an important role in the erosion behaviour of the deposits when quartz sand was used as erodent particles. On the other hand, only volume fraction of carbides irrespective of carbide type mainly controlled the erosion rate of the same deposits when iron ore was used as erodent particles. Such difference is attributed due to difference in metal removal mechanisms by the two erodent particles used. Hard quartz sand particles were capable of causing damage to most of the carbides while relatively softer iron ore particles were unable to fracture any carbides present in the microstructures. Furthermore, relatively brittle matrix led to high erosion rate which is significant in case of quartz sand as erodent, but not in case of iron ore particles. Like abrasion resistance, hardness is not a true index of erosion resistance of hardfacing deposits.