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根据流体力学理论和传热学机理,建立了运动等离子弧作用下立焊穿孔焊接熔池流场和温度场的三维瞬态数值分析模型,并采用有限元法对模型进行离散化处理。模型中,考虑了熔池内部液态金属的对流传热和熔池外部的固体导热、材料热物理性能参数随温度的变化、焊件表面通过对流和辐射向周围环境的散热以及熔化/凝固相变潜热对熔池流场与温度场的影响,焊接热源采用高斯分布函数,计算中对边界条件进行了处理,根据穿孔熔池温度场与流场模型的特点,采用非均匀网格对单元进行划分,并采用分区异步长算法确定时间步长,利用ANSYS(一种有限元计算软件)有限元软件对所建立的模型进行了求解。通过试验测量焊缝几何尺寸与计算结果相比较,验证了本模型的计算结果和实际相差不大,是基本正确和可靠的。 相似文献
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介绍了等离子弧产生臭氧机理及对人体的危害,实测表明,在等离子弧区,影响臭氧浓度的主要工艺参数是电流,电流愈大,紫外幅射愈强,产生臭氧愈多,提高50A电流,等离子弧区臭氧浓度可增加16.9%,因此对臭氧危害应采取“防”和“治”两方面措施。所谓“防”是指正确调节等离子弧工艺参数,在满足工艺要求条件下,尽量降低电流,减少气体流量;所谓“治”是指合理安装排风除尘装置,把等离子弧产臭氧及粉尘对人体危害控制在 相似文献
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等离子弧喷焊分布式微机控制系统的研究 总被引:2,自引:2,他引:0
以等离子弧喷焊为例,介绍了分布式控制系统对焊接过程进行控制的原理和方法,提出当控制对象较多时,采用计算机分级结构,即以一个主计算机和多个从计算机为基础的结构体系,可达到理想的综合控制效果。试验结果表明,采用分散控制,集中管理的方法,使系统的可靠性大大提高,控制更加灵活,精度更高,功能更强。 相似文献
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材料为ZG310-570的铸钢件因承受冲击载荷的频繁作用导致其内孔磨损失效,是该类铸钢件最主要的失效形式。利用粉末等离子弧喷焊技术对铸钢件受损内孔进行修复,并利用火花直读光谱仪、金相显微镜、布氏硬度计、冲击试验机和扫描电子显微镜分别对喷焊层外观质量、显微组织和力学性能进行分析。分析结果表明,采用粉末等离子弧喷焊修复方法使铸钢件内孔尺寸得到恢复;喷焊层与基体为冶金结合,结合线清晰;喷焊层的硬度值为267.5 HBW,优于基体材料的180.2 HBW,修复后的内孔冲击吸收功为15.40 J,满足技术要求;喷焊层的断口存在大量撕裂,说明喷焊层具有一定的冲击韧性。 相似文献
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AnewtypeofpilotarcpowersourceusedforA.C.plasmaarcweldingofaluminumalloys¥ZhengBing;WangQilongandLiXia(HarbinInstituteofTechno... 相似文献
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The adoption of two-shifting in coal-fired power generation (switching from on-load to off-load conditions on a daily basis and off-load for the weekend) results in regular cycling of the solution chemistry of the condensed steam on the turbine discs. A first stage investigation has been made of the effect of such chemistry cycling on the corrosion potential of the disc steel. The corrosion potential is typically about +0.05 V (SCE) in off-load chemistry (aerated pure water) and below −0.6 V (SCE) in on-load chemistry (deaerated solution containing chloride or chloride and sulphate anions). The critical observation was the sluggish response of the corrosion potential upon restoration of deaerated on-load conditions with the implication of a likely increase in pit and stress corrosion crack development. 相似文献
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Effect of Fe-Zn alloy layer on the corrosion resistance of galvanized steel in chloride containing environments 总被引:2,自引:0,他引:2
In this study, the effect of Fe-Zn alloy layer that is formed during galvanizing process on the corrosion behavior of galvanized steel has been investigated. The galvanostatic dissolution of galvanized steel was carried out in 0.5 M NaCl solution to obtain the Fe-Zn alloy layer on the base steel. The alloy layer was characterized to be composed of FeZn13, FeZn7 and Fe3Zn10 intermetallic phases, which constitute the zeta, delta1 and gamma layers of galvanized steel, respectively. It was observed that the alloy layer has similar cathodic polarization behavior but different anodic polarization behavior compared to galvanized steel. The anodic current plateau of alloy layer was up to 100 times lower than that of galvanized coating. Corrosion test performed in wet-dry cyclic condition has shown that the alloy layer has lower corrosion rate as compared to galvanized steel. From the results of corrosion test of alloy layer and base steel, it was concluded that Zn2+ has positive effect on the protectiveness of the zinc corrosion products. The measurement of surface potential over the alloy/steel galvanic couple has confirmed the galvanic ability of alloy layer to protect both the alloy layer itself and the base iron during initial stage of atmospheric corrosion. 相似文献
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E.E. Abd El Aal 《Corrosion Science》2008,50(1):47-54
The open circuit potentials of Zn electrode were followed as a function of time in different concentrations Na2B4O7 solutions until steady-state, Est., values were attained. The potential shifts immediately towards positive values, indicating film thickening and repair. The effect of addition of NaCl, NaBr and NaI as aggressive agent on the steady-state potential of a Zn electrode previously equilibrated in a passivating borate solution was also established. For each Na2B4O7 concentration, the variation in the potential with the quantity of aggressive anions follows an S-shaped relationship. The new potentials are established after an induction period which decreases with the increase in the concentration of the aggressive anion, Cagg., and/or decreases in that of the passivator anion, Cpass.. The concentration, Cagg., that can be tolerated by a certain concentration of the passivator anion, Cpass., is given by the relation: log Cpass. = k + n log Cagg., where k and n are constants. This is derived on the basis of competitive adsorption of both types of anion and the structure of the double layer at the metal/solution interface. The implications of the equations are briefly discussed. 相似文献
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E.E. Abd El Aal 《Corrosion Science》2008,50(1):41-46
The open circuit potentials of Zn electrode were followed as a function of time in different concentration of Na2B4O7 solution until steady-state, Est., values were attained. The potential shifts immediately towards positive values, indicating film thickening and repair. The rate of oxide film thickening was determined from the linear relationship between the open circuit potential, E, of the Zn electrode and the logarithm of immersion time t as E = a1 + b1 log t. The liner plots consist of two segments indicating the duplex nature of the formed oxide film on the Zn surface. The final steady- state potential, Est., varied with the logarithm of molar concentration of Na2B4O7 solution according to: Est. = a2 − b2 log CNa2B4O7. The effect of rising pH and temperature was also studied. It was found that the rising of pH and temperature of the solution affect on the rate of oxide film thickening and the final steady- state potential. 相似文献
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K. Yazdanfar 《Corrosion Science》2010,52(4):1297-6672
The kinetics of oxide film formation/conversion on carbon steel in the presence of halide anions at pH 10.6 were studied by electrochemical and surface analytical techniques. While variations in breakdown potential are observed in the presence of the different halides, the breakdown potential does not show any systematic dependence on halide type and concentration, and never occurs below 0.0 V vs. SCE. It is proposed that the conversion of Fe3O4/γ-Fe2O3 to γ-FeOOH leads to a volume change, causing the film to fracture. The halide anion then takes advantage of the opportunity to accelerate breakdown and inhibit repassivation. 相似文献
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Corrosion of Mo-silicides and MoxRuySiz compounds in molten glass is studied by electrochemical techniques at 1350 °C, metallographic observations (SEM) and chemical analysis (EPMA). The open circuit potential measurements (free-potential) enabled the determination of the reactions responsible for the degradation of the materials.The degradation of Mo-silicide occurs through selective oxidation of Si. MoxRuySiz compounds were subjected to reactions leading to the successive oxidation of silicon and molybdenum. The progressive depletion of Si and Mo resulted in the more or less quick formation of a thick, porous and low adherent Ru-layer. Therefore, Ru-additions had no positive effect on the molten glass corrosion resistance of MoSi2-based materials and should even accelerate the degradation kinetics of the later through galvanic coupling. 相似文献